Cabletron Systems 100BASE-FX Cabling Manual

Cabletron Systems

Cabling Guide

Notice

Cabletron Systems reserves the right to make changes in speciﬁcations and other information contained in this document without prior notice. The reader should in all cases consult Cabletron Systems to determine whether any such changes have been made.

The hardware, ﬁrmware, or software described in this manual is subject to change without notice.

IN NO EVENT SHALL CABLETRON SYSTEMS BE LIABLE FOR ANY INCIDENTAL, INDIRECT, SPECIAL, OR CONSEQUENTIAL DAMAGES WHATSOEVER (INCLUDING BUT NOT LIMITED TO LOST PROFITS) ARISING OUT OF OR RELATED TO THIS MANUAL OR THE INFORMATION CONTAINED IN IT, EVEN IF CABLETRON SYSTEMS HAS BEEN ADVISED OF, KNOWN, OR SHOULD HAVE KNOWN, THE POSSIBILITY OF SUCH DAMAGES.

Printed in the United States of America.

Order Number: 9031845-02E1 December 1996

Cabletron Systems, Inc. P.O. Box 5005 Rochester, NH 03866-5005

Cabletron Systems , SPECTRUM , BRIM , DNI , FNB , LANVIEW , Multi Media Access Center , are

registered trademarks, and Bridge/Router Interface Modules , BRIM-A100 , Desktop Network

Interface , EPIM , EPIM-3PS , EPIM-A , EPIM-C , EPIM-F1 , EPIM-F2 , EPIM-F3 , EPIM-T , EPIM-T1 , EPIM-X , Media Interface Module , MicroMMAC , MIM , MMAC , MMAC-3FNB , MMAC-5FNB ,, MMAC-M8FNB , MMAC-Plus , RMIM , SPECTRUM Element Manager , SPECTRUM for Open Systems , are trademarks of Cabletron Systems, Inc.

All other product names mentioned in this manual may be trademarks or registered trademarks of their respective companies.



Notice

Chapter 1 Introduction

Using This Guide.........................................................................................................................1-1

Document Organization ............................................................................................................. 1-1

Document Conventions..............................................................................................................1-3

Warnings and Notiﬁcations ................................................................................................1-3

Formats ..................................................................................................................................1-3

Additional Assistance .................................................................................................................1-4

Related Documentation .............................................................................................................. 1-4

Contents

Chapter 2 Cabling Terms

Physical Components..................................................................................................................2-1

Media......................................................................................................................................2-1

Cable.......................................................................................................................................2-1

Wire.........................................................................................................................................2-2

Connector ..............................................................................................................................2-3

Port .........................................................................................................................................2-6

Test Characteristics ......................................................................................................................2-6

Chapter 3 Relevant Speciﬁcations

EIA/TIA........................................................................................................................................3-1

Universal Service Order Code (USOC) ....................................................................................3-2

National Electrical Code (NEC)................................................................................................. 3-2

Chapter 4 Ethernet Media

Cabling Types ............................................................................................................................... 4-1

Attachment Unit Interface (AUI) .......................................................................................4-1

Coaxial Cable ........................................................................................................................4-3

Unshielded Twisted Pair (UTP)..........................................................................................4-5

Fiber Optics .........................................................................................................................4-14

Connector Types ........................................................................................................................4-17

AUI .......................................................................................................................................4-17

Coaxial Cable ......................................................................................................................4-19

UTP Cable............................................................................................................................4-23

Fiber Optics .........................................................................................................................4-28

iii

Chapter 5 Ethernet Network Requirements

10BASE-T ......................................................................................................................................5-1

Cable Type .............................................................................................................................5-1

Insertion Loss (Attenuation) ...............................................................................................5-1

Impedance .............................................................................................................................5-2

Jitter.........................................................................................................................................5-2

Delay.......................................................................................................................................5-2

Crosstalk ................................................................................................................................5-3

Noise.......................................................................................................................................5-3

Other Considerations...........................................................................................................5-3

Length.....................................................................................................................................5-4

10BASE-F (Multimode)...............................................................................................................5-4

Cable Type .............................................................................................................................5-4

Attenuation............................................................................................................................5-5

Insertion Loss ........................................................................................................................5-5

Delay.......................................................................................................................................5-5

Length.....................................................................................................................................5-6

Ethernet FOIRL (Single Mode)...................................................................................................5-6

Cable Type .............................................................................................................................5-6

Attenuation............................................................................................................................5-6

Insertion Loss ........................................................................................................................5-7

Delay.......................................................................................................................................5-7

Length.....................................................................................................................................5-7

10BASE2 ........................................................................................................................................5-8

Cable Type .............................................................................................................................5-8

Termination............................................................................................................................5-8

Connectors/Taps ..................................................................................................................5-8

Grounding .............................................................................................................................5-9

Length.....................................................................................................................................5-9

10BASE5 (Coaxial Cable)............................................................................................................5-9

Cable Type .............................................................................................................................5-9

Termination............................................................................................................................5-9

Connectors/Taps ................................................................................................................5-10

Grounding ...........................................................................................................................5-10

Length...................................................................................................................................5-10

Chapter 6 Full-Duplex Ethernet Network Requirements

Full-Duplex 10BASE-T................................................................................................................6-1

Cable Type .............................................................................................................................6-1

Insertion Loss (Attenuation) ...............................................................................................6-2

Impedance .............................................................................................................................6-2

Jitter.........................................................................................................................................6-2

Delay.......................................................................................................................................6-2

Crosstalk ................................................................................................................................6-3

Noise.......................................................................................................................................6-3

Other Considerations...........................................................................................................6-3

Length.....................................................................................................................................6-4

10BASE-F (Multimode)...............................................................................................................6-4

Cable Type .............................................................................................................................6-4

Attenuation............................................................................................................................6-5

Insertion Loss........................................................................................................................6-5

Delay.......................................................................................................................................6-5

Length ....................................................................................................................................6-6

Ethernet FOIRL (Single Mode) ..................................................................................................6-6

Cable Type .............................................................................................................................6-6

Attenuation............................................................................................................................6-6

Insertion Loss........................................................................................................................6-7

Delay.......................................................................................................................................6-7

Length ....................................................................................................................................6-7

Chapter 7 Fast Ethernet Network Requirements

100BASE-TX..................................................................................................................................7-1

Cable Type .............................................................................................................................7-1

Insertion Loss (Attenuation)...............................................................................................7-2

Impedance .............................................................................................................................7-2

Jitter ........................................................................................................................................7-2

Delay.......................................................................................................................................7-3

Crosstalk ................................................................................................................................ 7-3

Noise.......................................................................................................................................7-3

Other Considerations...........................................................................................................7-3

100BASE-FX (Multimode) .......................................................................................................... 7-4

Cable Type .............................................................................................................................7-4

Attenuation............................................................................................................................7-4

Insertion Loss........................................................................................................................7-4

Delay.......................................................................................................................................7-5

Length ....................................................................................................................................7-5

Hybrid Installations ....................................................................................................................7-5

Repeater Classes ................................................................................................................... 7-6

Buffered Uplinks...................................................................................................................7-7

Chapter 8 Full-Duplex Fast Ethernet Network Requirements

100BASE-TX..................................................................................................................................8-1

Cable Type .............................................................................................................................8-1

Insertion Loss (Attenuation) ...............................................................................................8-2

Impedance .............................................................................................................................8-2

Jitter.........................................................................................................................................8-2

Crosstalk ................................................................................................................................8-2

Noise.......................................................................................................................................8-3

Other Considerations...........................................................................................................8-3

Length.....................................................................................................................................8-4

100BASE-FX (Multimode) ..........................................................................................................8-5

Cable Type .............................................................................................................................8-5

Attenuation............................................................................................................................8-5

Insertion Loss ........................................................................................................................8-5

Delay.......................................................................................................................................8-5

Length.....................................................................................................................................8-6

Chapter 9 Token Ring Media

Cabling Types ...............................................................................................................................9-1

Shielded Twisted Pair (STP) ................................................................................................9-1

Unshielded Twisted Pair (UTP) ..........................................................................................9-5

Fiber Optics............................................................................................................................9-8

Connector Types.........................................................................................................................9-10

STP ........................................................................................................................................9-10

Unshielded Twisted Pair Cable ........................................................................................9-15

Fiber Optics..........................................................................................................................9-17

Chapter 10 Token Ring Network Requirements

IEEE 802.5 Shielded Twisted Pair ............................................................................................10-1

Cable Type ...........................................................................................................................10-1

Attenuation..........................................................................................................................10-2

Impedance ...........................................................................................................................10-2

Link Length .........................................................................................................................10-3

Trunk Cable Length............................................................................................................10-4

IEEE 802.5 Unshielded Twisted Pair .......................................................................................10-5

Cable Type ...........................................................................................................................10-5

Attenuation..........................................................................................................................10-5

Impedance ...........................................................................................................................10-6

Crosstalk ..............................................................................................................................10-6

Link Length .........................................................................................................................10-6

Trunk Cable Length............................................................................................................10-7

IEEE 802.5j (Multimode Fiber Optics) ....................................................................................10-8

Cable Type ...........................................................................................................................10-8

Attenuation..........................................................................................................................10-9

Link Length ......................................................................................................................... 10-9

Trunk Cable Length............................................................................................................10-9

IEEE 802.5j Single Mode Fiber Optics................................................................................... 10-10

Cable Type .........................................................................................................................10-10

Attenuation........................................................................................................................10-10

Link Length ....................................................................................................................... 10-10

Trunk Cable Length..........................................................................................................10-10

Chapter 11 FDDI Media

Cabling Types ............................................................................................................................. 11-1

Unshielded Twisted Pair (UTP)........................................................................................ 11-1

Shielded Twisted Pair (STP).............................................................................................. 11-5

STP Cable Quality ..............................................................................................................11-7

Fiber Optics .........................................................................................................................11-8

Connector Types ...................................................................................................................... 11-11

UTP..................................................................................................................................... 11-11

STP...................................................................................................................................... 11-12

Fiber Optics .......................................................................................................................11-13

Chapter 12 FDDI Network Requirements

MMF-PMD.................................................................................................................................. 12-1

Cable Type ...........................................................................................................................12-1

Attenuation..........................................................................................................................12-1

Length ..................................................................................................................................12-2

Emitted Power ....................................................................................................................12-2

SMF-PMD ...................................................................................................................................12-2

Cable Type ...........................................................................................................................12-2

Attenuation..........................................................................................................................12-2

Length ..................................................................................................................................12-3

Emitted Power ....................................................................................................................12-3

LCF-PMD....................................................................................................................................12-3

Cable Type ...........................................................................................................................12-3

Attenuation..........................................................................................................................12-3

Length ..................................................................................................................................12-4

Emitted Power ....................................................................................................................12-4

TP -PMD (UTP)..........................................................................................................................12-4

Cable Type ...........................................................................................................................12-4

Attenuation..........................................................................................................................12-4

Length ..................................................................................................................................12-5

TP-PMD (STP)............................................................................................................................12-5

Cable Type ...........................................................................................................................12-5

Attenuation..........................................................................................................................12-5

Length ..................................................................................................................................12-5

vii

Chapter 13 Cabling Devices

Hardware Mounting..................................................................................................................13-2

Relay Rack ...........................................................................................................................13-2

Enclosed Equipment Cabinet............................................................................................13-3

Cable Termination......................................................................................................................13-4

Patch Panel ..........................................................................................................................13-4

Harmonica ...........................................................................................................................13-5

Punchdown Block...............................................................................................................13-6

Distribution Box..................................................................................................................13-7

Wallplate ..............................................................................................................................13-8

Surface Mount Box .............................................................................................................13-9

Facility Cable Management......................................................................................................13-9

Conduit ................................................................................................................................13-9

D-Rings...............................................................................................................................13-10

J-Hooks...............................................................................................................................13-11

Strain-Relief Bracket.........................................................................................................13-11

Innerduct............................................................................................................................13-12

Latching Duct....................................................................................................................13-12

Raceway .............................................................................................................................13-13

Labeling Tape ....................................................................................................................13-13

Ty-Wraps and Adhesive Anchors...................................................................................13-14

Chapter 14 Connecting and Terminating

Ethernet .......................................................................................................................................14-1

DB15......................................................................................................................................14-1

RJ45.......................................................................................................................................14-3

RJ21.......................................................................................................................................14-4

BNC ......................................................................................................................................14-5

N-Type..................................................................................................................................14-7

ST Connector .......................................................................................................................14-7

Token Ring ..................................................................................................................................14-9

DB9........................................................................................................................................14-9

RJ45.....................................................................................................................................14-10

Token Ring MIC ................................................................................................................14-12

ST Connector .....................................................................................................................14-13

FDDI...........................................................................................................................................14-14

RJ45.....................................................................................................................................14-14

FDDI MIC ..........................................................................................................................14-16

SC Connector.....................................................................................................................14-18

Appendix A Charts and Tables

Ethernet ........................................................................................................................................A-1

Token Ring ...................................................................................................................................A-4

FDDI..............................................................................................................................................A-6

viii

Introduction

Using This Guide

The Cabletron Systems Cabling Guide is intended to provide much of the information necessary to allow Network Managers to plan facility network cabling and to ensure that the cabling is usable by the networking devices that will populate the cabling.

Chapter 1

This Cabling Guide also provides instructions that may be helpful for connecting Cabletron Systems networking devices to an existing facility cabling infrastructure.

Document Organization

This guide begins with an overview of the important aspects of cabling and cables. The information presented in the initial sections is essential to a complete understanding of the material that is presented in later sections. Following the introductory material, detailed examinations of the standard media and connectors used for Ethernet, Token Ring, and Fiber Distributed Data Interface (FDDI) networks are presented. The closing sections of the document describe some common installation and cable management devices, and explain some methods for testing cables and planning installations.

The remainder of this guide contains charts and tables which supply much of the information that the cable system planning process requires, and an extensive glossary of the terms used within this guide and other Cabletron Systems publications.

1-1

Introduction

The following summarizes the organization of this manual:

Chapter 1, Introduction , discusses the use and contents of this guide.

Chapter 2, Cabling Terms , deﬁnes and explains some of the terminology used throughout this document to describe aspects and components of cabling and installation planning.

Chapter 3, Relevant Speciﬁcations , details some relevant speciﬁcations and standards that apply to the installation of facility network cabling.

Chapter 4, Ethernet Media , identiﬁes and discusses several networking cables and their characteristics when used in Ethernet and Fast Ethernet networking environments. The chapter examines the physical characteristics and requirements of both physical cabling and the connectors and ports used with the cabling.

Chapter 5, Ethernet Network Requirements , provides a series of test envelopes and installation requirements that Ethernet cabling must meet in order to conform to the Ethernet standard.

Chapter 6, Full-Duplex Ethernet Network Requirements , supplies the test characteristics and network limitations of Ethernet networks intended to operate in full-duplex mode.

Chapter 7, Fast Ethernet Network Requirements , deals with the cable characteristics and requirements of the Fast Ethernet networking technology, including 100BASE-TX and 100BASE-FX.

Chapter 8, Full-Duplex Fast Ethernet Network Requirements , Provides speciﬁc information related to the requirements of full-duplex Fast Ethernet network cabling.

Chapter 9, Token Ring Media , identiﬁes and details the cables and connectors that may be used in Token Ring network environments.

Chapter 10, Token Ring Network Requirements , lists the required performance and test characteristics of Token Ring cabling.

Chapter 11, FDDI Media , lists and describes the various cabling types that may be used with Fiber Distributed Data Interface (FDDI) networks.

Chapter 12, FDDI Network Requirements , lists the required test characteristics and accepted maximums of cabling used in FDDI network installations.

Chapter 13, Cabling Devices , provides a list of several useful tools and accessories that can aid in the installation, management, and control of installed cabling in a facility.

Chapter 14, Connecting and Terminating , describes the procedures involved in connecting and disconnecting the standard connectors of each network technology treated in Chapters 4, 9, and 11.

1-2 Document Organization

Appendix A, Charts and Tables , provides the information contained in the network requirements chapters of this document in a simpliﬁed table form. Tables of test requirements and acceptable levels are provided for all media discussed in this document.

Following the appendix, the Cabletron Systems Glossary of Terms may be found.

Document Conventions

Warnings and Notiﬁcations

Introduction

Formats

NOTE

TIP

CAUTION

References to chapters or sections within this document are printed in boldface type.

References to other Cabletron Systems publications or documents are printed in

italic type.

Note symbol. Calls the reader’s attention to any item of

information that may be of special importance.

Tip symbol. Used to convey helpful hints concerning

procedures or actions that would assist the operator in performing the task in a more timely manner in the future.

Caution symbol. Used to caution against an action that could

result in damage to equipment or poor equipment performance.

Warning symbol. Used to warn against an action that could

result in personal injury or death and equipment damage.

Document Conventions 1-3

Introduction

Additional Assistance

The planning and installation of facility cabling for network operation is a complex and highly specialized process. Due to the different nature of each and every cabling installation and the special problems and concerns raised by any facility, there may be aspects of installation planning that are not covered in this guide.

If you have questions or concerns about your cabling design, or if you require installation personnel to perform the actual installation process, Cabletron Systems maintains a staff of network design personnel and a sizable team of highly-trained cabling and hardware installation technicians. The services of the Networking Services group are available to customers at any time. If you are interested in obtaining design assistance or a network installation plan from the Networking Services group, contact your Cabletron Systems Sales Representative.

In addition to the availability of Networking Services, the Cabletron Systems Technical Support department is available to answer customer questions regarding existing Cabletron Systems networks or planned expansion issues. Contact Cabletron Systems at (603) 335-9400 to reach the Technical Support department with any speciﬁc product-related questions you may have.

Related Documentation

The following publications may be of assistance to you in the design process. Several of these documents present information supplied in this Cabling Guide in greater or lesser detail than they are presented here.

• Cabletron Systems Networking Guide - MMAC-FNB Solutions

• Cabletron Systems Ethernet Technology Guide

• Cabletron Systems Token Ring Technology Guide

• Cabletron Systems FDDI Technology Guide

• EIA/TIA 568 Speciﬁcation

• IEEE 802.3 Speciﬁcations

• IEEE 802.5 Speciﬁcations

• ANSI X3T9.5 Speciﬁcation

1-4 Additional Assistance

Chapter 2

Cabling Terms

This chapter identiﬁes and deﬁnes several terms that are used throughout the text of this manual.

Physical Components

The following terms and deﬁnitions deal with the physical makeup of cabling used in Local Area Networks.

Media

Media refers to a type or family of cables. When the term media is used, it indicates a type of cabling, rather than a speciﬁc cable. A reference to “ﬁber optic media” deals with the characteristics of all ﬁber optic cable types, such as single or multimode ﬁber optics.

Cable

The term cable, as used in this document, indicates either a speciﬁc type of transmission media (i.e., multimode ﬁber optic cable) or indicates a physical section of that media (i.e., “the installed cable must be no longer than 200 m”).

Facility Cabling

Facility cabling, sometimes referred to as building cable or horizontal cable, is the network cabling that is installed in a building or ofﬁce. It only includes the actual wires that are placed within the walls, conduits, or speciﬁc cable channels of the building. The majority of cabling used in a network installation is facility cabling.

2-1

Cabling Terms

Jumper Cabling

Run

Jumper cabling is a term that identiﬁes short, inexpensive cables that are used to make connections between nearby cabling devices. Typically, workstations and network devices are connected to the facility cabling of a site with jumper cables.

A “run” of cabling is a single end-to-end cable path in a networked facility. The cable run typically begins at a network device such as a hub or bridge and ends at a workstation or other end node. The cable run, if calculated, must include all areas on the cable to which signals will travel. On point-to-point media, such as UTP or ﬁber optics, this will be the same as the measure of cabling between stations. In a shared media environment, however, the measure of a run must include the total length of the shared cable being used, regardless of the distance between stations on that cable.

Wire

Core

A cable run includes the facility cabling, jumper cabling, and any passive cable management devices, such as wallplates, patch panels, and punchdown blocks, between the two devices. When a speciﬁc type of cabling is referred to when identifying a cable run, the term refers only to the total length of that type of cable in the installation.

As an example, if a thick coaxial cable run is referred to in an installation description, it is concerned with the total length of coaxial cable and does not include the AUI cables used to connect stations to transceivers on the thick coaxial cable. If a UTP cable run is referred to, it includes only the jumper cables, patch panels, wallplates, and facility cabling between the devices in question.

The wire terms listed below deal with the components that make up a physical cable.

The core of a wire is that portion of the wire upon which the electrical (or light, in the case of ﬁber optics) signals of network communications travel. In all cases, the term core refers to the transmissive center of the cable or wire in question. The term core is most often used when referring to a cable that has a single transmission path. Cables with multiple transmission paths cannot have an overall core.

2-2 Physical Components

Strand

Insulator

Shield

Cabling Terms

A strand is a metal or glass (in the case of ﬁber optics) transmission media that is typically surrounded by an insulator. Strands in metallic cables may be made up of either solid lengths of relatively thick wire (solid core) or a bundle of much thinner wires that contact one another throughout the wire (stranded).

An insulator is a layer of non-conductive material that protects the core or strands of a cable from both physical damage and from the effects of other strands within a multistranded cable. Insulator also protects the strands or core from the effects of external electrical noise to a small extent.

A shield is a layer of metal foil or braided screen that protects the core or strands of the cable from interference from outside electrical inﬂuences. The shield is wrapped around the core, and is separated from the core by a layer of insulator.

Gauge

Connector

The gauge of a wire is an indication of its thickness. Gauge is typically measured in American Wire Gauge (AWG). The lower the AWG number of a strand or core, the thicker it is. The gauge of a wire has an affect on the resistance it presents to electrical signals attempting to travel through it. In general, lower-gauge (thicker) strands allow network communications to travel through them more readily than strands with a higher gauge.

A connector is a metal, plastic, or composite assembly that is used to simplify the connection of separate lengths of cable or to connect cables to devices. Connectors are only found on cables (ports are located on devices). The terms that follow deﬁne important parts of connectors.

Physical Components 2-3

Cabling Terms

Housing (Shell)

The basis of the connector is its housing. A housing is the metal or plastic parts that make up the shape of the connector and determine its characteristics and what ports or other connectors it may be attached to. The purpose of the housing is to separate and organize any strands in the cable being connected and arrange them in a standard fashion for connection to a port or other connector.

If a housing can be assembled and disassembled easily, or is made up of several separate sections, it may be called a shell.

A pin is an exposed metal prong or wire that is either inserted into a channel or allowed to touch a contact. In this fashion, the pin creates a path for network signals to ﬂow from the connector to the port or device it is connected to.

Pins may be fully exposed, for insertion into a channel, or partially exposed, for connection to a contact. Fully exposed pins will protrude from a housing or insulator. Partially exposed pins are encased on two or three sides by the construction material of the connector housing. An example of a partially exposed pin is that used in the RJ45 modular connector.

Contact

Channel

A contact refers to a location where one electrical transmission carrier meets another and creates a link through which electrical signals may be passed. Contacts, when referred to as physical parts of a connector or port, are usually ﬂat, exposed metal surfaces.

A channel is a hollow cylinder, usually metal, that receives a fully exposed pin. The pin is inserted into the channel, where an electrical contact is made.

The cabling term “channel” should not be confused with the networking term “channel,” which refers to a logical path or group of paths of transmission and reception for network signals.

2-4 Physical Components

Gender

Cabling Terms

The gender of a connector refers to the organization of the pins, contacts, or channels of the connector. Connectors may be identiﬁed as male, female, hermaphroditic, or genderless. The most common types of connectors in networking are male and female.

A male connector is one that is inserted into a recessed or hollow port. In the case of some connectors, the determination of male gender is based upon whether the connector makes its networking connection through a pin or a channel. Connectors with pins are considered male.

Female connectors are those that are constructed to accept a male connector. Female connectors typically provide channels into which the pins of male connectors are inserted. A readily available example of male and female connectors is the standard electrical extension cord. The extension cord has a male end, the prongs that are placed in the wall outlet, and a female end, the slots on the opposite end of the cable.

Connections in any gendered cable systems must be made between one male connector and one female connector. The connectors themselves will not allow male/male or female/female connections.

Keyed

Threaded

Locking

Some connectors are genderless or hermaphroditic. These are connectors that have aspects of both male and female connector types. They may be connected to any other port or connector. The Token Ring MIC connector is perhaps the most common genderless connector in networking.

A keyed connector is one that has a housing speciﬁcally designed to be connected to a port in a particular orientation. The keyed connector is shaped in such a way that it may only be inserted into the port or connector so that the pins or channels of the housing match up properly.

Threaded connectors are designed to be secured to other threaded connectors or ports. They are designed to be screwed together. The threads hold the connectors in place.

A locking connector is one that snaps into place. Locking connectors are usually keyed, and are often gendered. The locking action holds the connector ﬁrmly in place and makes the connection resistant to disconnection due to strain or movement. Locking may be accomplished by a spring clip mechanism or by the use of key pins and locking channels.

Physical Components 2-5

Cabling Terms

Port

A port is a set of pins or channels on a networking or cabling device that are arranged to accept a connector. Ports are constructed much like connectors, and will only accept the connector type they are speciﬁcally designed for. Ports may be keyed, gendered, or locking, in the same fashion as connectors.

Jack

A jack is a term that is usually synonymous with port, and indicates a port location. Typically, the term refers to ports located on wallplates or other passive cabling devices.

Test Characteristics

The following section deals with the various important speciﬁcations and testing information related to the cabling and connectors used in LAN environments.

Impedance

Crosstalk

Noise

Impedance is the resistance that a conductive cable offers to the transmission of current. Impedance is measured in ohms (Ω). Cables with high Impedance values are highly resistant to the transmission of electrical signals. Some network operation speciﬁcations and network devices require the use of cabling with speciﬁc impedance levels and will not work properly with cabling having signiﬁcantly higher or lower values.

Crosstalk is electrical interference between wires in a multi-stranded cable, such as Unshielded Twisted Pair (UTP) cabling. Crosstalk occurs when a cable strand or group of strands absorb signals from other wires that they are adjacent to. Crosstalk can be caused by a break in the insulation or shielding that separates wires from one another in a bundle.

In regards to network cabling, the term noise refers to electrical noise, electrical signals that are spontaneously introduced onto a cable due to that cables proximity to noise sources. Typical sources of electrical noise include lighting ﬁxtures, electric motors, and transformers.

2-6 Test Characteristics

Delay

Attenuation

Cabling Terms

The term delay, when applied to network cabling, typically refers to the propagation delay of the segment or network. As signals in both electrically conductive cables and ﬁber optic cables travel through the transmission media at a fraction of the speed of light, there is an appreciable delay between the transmission of a signal on one end of a cable and the reception of the same signal on the other end. Network delay is typically measured in microseconds (µs). One microsecond is equal to 1/1,000,000 of a second.

Attenuation is the reduction of signal strength in a cable as a result of absorption or dispersion of the electrical or optical impulse traveling through the cable. The effect of attenuation is a gradual decrease in the power or clarity of a signal after it traverses a length of cabling. The measure of the attenuation of a cable is expressed in decibels (dB).

There are two different measures of attenuation that are important from a networking point of view. The ﬁrst is the attenuation characteristics of a cable. These are estimates of the expected attenuation that a signal will suffer for passing through a given length of the cable. Expected attenuation values are expressed in dB/m, dB/km, or dB/ft.

The second measure of attenuation is that which is determined by testing a length of cable to determine its total attenuation. Total attenuation takes into account all components of the cable run and is expressed as a total measure of signal loss in decibels from one end of the cable to the other.

Test Characteristics 2-7

Cabling Terms

2-8 Test Characteristics

Chapter 3

Relevant Speciﬁcations

This chapter presents and examines a number of networking speciﬁcations and how they are related to planning and installing network cabling.

Just as there are speciﬁcations that deal with the tested aspects of installed cabling and their ﬁtness for use with a particular networking technology, there are also standards that deal with the construction of cables and the methods by which they may be installed. These higher-level cabling standards involve such things as the pairing and insulating of cables within a multi-wire cable, the labeling of cable jackets, and the allowable proximity of cables of certain types to other cables or electrical equipment.

EIA/TIA

These higher-level speciﬁcations are out of the purview of this Cabling Guide, and are not covered in detail within this document. Some of the aspects treated by the higher-level speciﬁcations are discussed in the sections which follow, as they impact or affect the use or selection of cabling materials in certain facilities or for use with individual networking standards.

The EIA/TIA speciﬁcations deal with the recommended methods and practices for constructing, installing, and terminating wiring. There are several different EIA/TIA speciﬁcations which cover different aspects of wiring. EIA/TIA speciﬁcation number 568 is the one that network installers are most commonly interested in, as it deals with the installation of networking and telephony and networking cable.

The construction speciﬁcations of the EIA/TIA speciﬁcation are important only when selecting a speciﬁc type of cable. The EIA/TIA construction speciﬁcation used in the manufacture of that cable determines the construction and tested characteristics of the cable, the organization and quality of its components, and what applications it is suited for.

3-1

Relevant Speciﬁcations

The installation procedures of the EIA/TIA help to ensure that care is taken to avoid cabling situations that are possibly hazardous or which can result in degradation of the operating quality of the installed cable.

The EIA/TIA 568 speciﬁcation details the minimum distance that cables may be located away from sources of electrical noise, what types of power cables or other telephony cabling the cables being installed may be next to, how the connectors must be installed, and other aspects which affect the overall usability of the cable for a particular purpose.

Full copies of the EIA/TIA 568 speciﬁcation may be obtained from a technical document seller or ordered directly from the Electronics Industries Association/Telecommunications Industry Association.

Universal Service Order Code (USOC)

The USOC speciﬁcation is similar to many EIA/TIA speciﬁcations, including EIA/TIA 568. The USOC speciﬁcation describes, among other things, the construction and installation characteristics of a type of twisted pair cable. The USOC speciﬁcation deals with the same aspects of the installation process as the EIA/TIA speciﬁcations, but provides slightly different guidelines.

Originally, the speciﬁcation was drafted by the Bell System, and copies of the USOC speciﬁcation may be obtained from technical booksellers or those Regional Bell Operating Companies (RBOCs) which provide speciﬁcations to customers.

National Electrical Code (NEC)

The National Electrical Code or NEC is an overall speciﬁcation to which all facility wiring of any kind in the United States of America must be held. As the NEC is a higher-level standard than either the EIA/TIA or USOC speciﬁcations, the two lower-level speciﬁcations are designed to be automatically in accordance with the NEC.

3-2 Universal Service Order Code (USOC)

Chapter 4

Ethernet Media

This chapter examines the physical characteristics and requirements of both physical cabling and the connectors and ports used with the cabling in Ethernet , Full-Duplex Ethernet, and Fast Ethernet environments.

Cabling T ypes

Attachment Unit Interface (AUI)

Attachment Unit Interface cable (referred to hereafter as AUI cable) is a shielded, multistranded cable that is used to connect Ethernet network devices to Ethernet transceivers. AUI cable should be used for no other purpose. AUI cable is available in two basic types: standard AUI and ofﬁce AUI.

AUI cable is made up of four individually shielded pairs of wire surrounded by an overall cable shielding sheath. The doubled shielding makes AUI cable more resistant to electrical signal interference than other, lighter cables, but increases the signal attenuation suffered over long distances.

AUI cables are connected to other devices through DB15 connectors. The connectors of an AUI cable run from Male to Female at all times. Any transceiver cable that uses a Male/Male or Female/Female conﬁguration is a non-standard cable, and should be avoided.

4-1

Ethernet Media

YES

Standard

NO NO

1845n01

Figure 4-1. AUI Cable Conﬁgurations

The reason for the conﬁguration of AUI cables as Male to Female only is due to their intended use. AUI cables are designed to attach transceivers to workstations or other active network equipment. Transceivers require power to operate, and that power is supplied either by an external power supply or by a pair of wires dedicated to power in the cable. A Male/Male or Female/Female AUI cable does not correctly supply power and grounding to the transceiver. If you use a Female/Female AUI cable between two transceiver devices, both transceivers will try to draw power from each other. Neither is capable of providing this power. Therefore, this conﬁguration will not function. Likewise, two AUI device ports should never be directly attached without using transceivers.

If you ﬁnd yourself in need of a gender changer to connect a

NOTE

device with AUI cable, you are doing something wrong.

The gauge of the internal wires that make up the cable determines the thickness and relative ﬂexibility of the AUI cable. Standard AUI cable (containing pairs of AWG 20 or 22 wire) is capable of reaching a maximum distance of 50 meters between transceivers and the network device, but is thick, (0.420 inch) and somewhat inﬂexible.

Standard AUI cables, due to their bulk, are typically used in environments that require the 50 meter distances that standard AUI cables can provide. In situations where the workstations or networking equipment are close to the transceivers they are to be connected to, Ofﬁce AUI cable, being more easily managed and more ﬂexible, is often used.

4-2 Cabling Types

Ofﬁce

Coaxial Cable

Ethernet Media

Ofﬁce AUI cable is a thinner cable that is more convenient to use on many environments than standard AUI. This lighter-gauge AUI cable is made up of four pairs of AWG 28 wire, which is thinner (at 0.26 inch) and much more easily ﬂexed, but can only be run to a maximum distance of 16.5 meters.

Ofﬁce AUI cable is intended to be used in places where standard AUI cable would be cumbersome and inﬂexible. Typically, ofﬁce AUI is used in locations where a large number of workstations are concentrated in a single area.

Coaxial cable is a cabling type where two or more separate materials share a common central axis. While several types of networking cables could be identiﬁed as having coaxial components or constructions, there are only two cable types that can support network operation using only one strand of cabling with a shared axis. These are commonly accepted as the coaxial cables, and are divided into two main categories: thick and thin coaxial cable.

Thick Coaxial Cable

Thick coaxial cable (also known as thick Ethernet cable, “thicknet,” or 10BASE5 cable), is a cable constructed with a single solid core, which carries the network signals, and a series of layers of shielding and insulator material. The shielding of thick coaxial cable consists of four stages. The outermost shield is a braided metal screen. The second stage shield, working inward, is usually a metal foil, but in some brands of coaxial cable may be made up of a second screen. The third stage consists of a second braided shield followed by the fourth stage, a second foil shield. The various shields are separated by non-conductive insulator materials.

Foil Shield

Solid Core

Insulator

Braided Shield

Outer Jacket

1845n02

Figure 4-2. Thick Coaxial Cable Diagram

Cabling Types 4-3

Ethernet Media

Thick coaxial cable is a media used exclusively in Ethernet installations, commonly as a backbone media. Transceivers are connected to the cable at speciﬁed distances from one another, and standard transceiver cables connect these transceivers to the network devices.

Due to the extensive shielding, thick coaxial cable is highly resistant to electrical interference by outside sources such as lighting, machinery, etc. Because of the bulkiness (typically 0.405 inch in diameter or thicker) and limited ﬂexibility of the cable, thick coaxial cable is primarily used as a backbone media and is placed in cable runways or laid above ceiling tiles to keep it out of the way.

Thick coaxial cable is designed to be accessed as a shared media. Multiple transceivers can be attached to the thick coaxial cable at multiple points on the cable itself. A properly installed length of thick coaxial cable can support up to 100 transceivers.

Annular Rings

Coaxial Cable

Thin Coaxial Cable

N-Type Connector

2.5 m

(10BASE5)

1845n03

Figure 4-3. Annular Rings

Multiple transceivers on a thick coaxial cable must be spaced at least 2.5 meters from any neighboring transceivers or terminators. Thick coaxial cable is often bright yellow or orange in color. The outer jacket will frequently be marked with annular rings, dark red or black sections of jacketing that are spaced 2.5 meters from one another. These annular rings are a useful guide for ensuring that terminators and transceivers are spaced not less than 2.5 m from one another.

Thin coaxial cable (also known as thin Ethernet cable, “thinnet,” “cheapernet,” RG-58 A/U, BNC or 10BASE2 cable) is a less shielded, and thus less expensive, type of coaxial cabling. Also used exclusively for Ethernet networks, thin coaxial cable is smaller, lighter, and more ﬂexible than thick coaxial cable. The cable itself resembles (but is not

identical to) television coaxial cable.

Thin coaxial cable is made up of a single outer copper shield that may be braided or foil, a layer beneath that of non-conductive dielectric material, and a stranded center conductor. This shielding makes thin coaxial cable resistant to electromagnetic interference as the shielding of thick coaxial cable does, but does not provide the same extent of protection. Thin coaxial cable, due to its less extensive shielding capacity, can be run to a maximum length of 185 meters (606.7 ft).

4-4 Cabling Types

Building Network Coax (BNC) connectors crimp onto a properly prepared cable end with a crimping tool. To prevent signal reﬂection on the cable, 50 Ohm terminators are used on unconnected cable ends.

As with thick coaxial cable, thin coaxial cable allows multiple devices to connect to a single cable. Up to 30 transceivers may be connected to a single length of thin coaxial cable, spaced a minimum of 0.5 meter from one another. This minimum spacing requirement keeps the signals from one transceiver from interfering with the operation of others. The annular rings on the thin coaxial cable are placed 0.5 meter apart, and are a useful guide to transceiver placement.

Unshielded Twisted Pair (UTP)

Unshielded Twisted Pair cabling (referred to here as UTP, but also may be termed copper wire, 10BASE-T wire, Category 3, 4, or 5 Ethernet wire, telephone cable, or twisted pair without shielded or unshielded qualiﬁer) is commonly made up of two, four, or 25 pairs of 22, 24, or 26 AWG unshielded copper solid or stranded wires. These pairs of wires are twisted together throughout the length of the cable, and are broken up into transmit and receive pairs. In each pair, one wire carries the normal Ethernet transmission, while its associated wire carries a copy of the transmission that has been inverted.

Ethernet Media

Tx+ Tx-

RxRx+

1845n04

Figure 4-4. UTP Cable Pair Association

The twisting of associated pairs helps to reduce the interference of the other strands of wire throughout the cable. This is due to the method of transmission used with twisted pair transmissions.

In any transceiver or Network Interface Card (NIC), the network protocol signals to be transmitted are in the form of changes of electrical state. The means by which the ones and zeroes of network communications are turned into these signals is called encoding. In a twisted pair environment, once a transceiver has been given an encoded signal to transmit, it will copy the signal and invert the polarity of that signal (see Figure 4-5). The result of this inverted signal is a mirror opposite of the original signal.

Cabling Types 4-5

Ethernet Media

Both the original and the inverted signal are then transmitted, the original signal over the TX+ wire, the inverted signal over the TX - wire. As these wires are the same length and of the same construction, the signal travels (propagates) at the same rate through the cable. Since the pairs are twisted together, any outside electrical interference that affects one member of the pair will have the same effect on the other member of that pair.

The transmissions travel through the cable, eventually reaching a destination transceiver. At this location, both signals are read in. The original signal is unchanged, but the signal that had previously been inverted is reverted to the original state. When this is done, it returns the encoded transmission to its original state, but reverses the polarity of any signal interference that the encoded transmission may have suffered.

Once the inverted transmission has been returned to the normal encoded state, the transceiver adds the two signals together. As the encoded transmissions are now identical, there is no change to the data content. Line noise spikes, however, are combined with noise spikes of their exact opposite polarity, causing them to cancel one another out.

Original Signal

Normal

Transmission

Inverted

Transmission

Induced

Noise Spike

Reversion of Inverted

Transmission

Noise spikes

cancel out

Resulting Signal

1845n05

Figure 4-5. UTP Signal Equalization

The UTP cable used in network installations is the same type of cable used in the installation of telephone lines within buildings. UTP cabling is differentiated by the quality category of the cable itself, which is an indicator of the type and quality of wire used and the number of times the wires are twisted around each other per foot. The categories range from Category 1 to Category 5, with Category 5 cabling being of the highest quality.

The wires that make up a length of UTP cable are numbered and color coded. These color codes allow the installer of the networking cable to determine which wires are connected to the pins of the RJ45 ports or patch panels. The numbering of the wires in EIA/TIA standard cables is based on the color of the insulating jacket that surrounds the core of each wire.

4-6 Cabling Types

Ethernet Media

The association of pairs of wire within the UTP cable jacket are decided by the speciﬁcations to which the cable is built. There are two main speciﬁcations in use around the world for the production of UTP cabling: EIA/TIA 568A and the EIA/TIA 568B. The two wiring standards are different from one another in the way that the wires are associated with one another at the connectors.

The arrangement of the wires in the two EIA/TIA speciﬁcations does not affect the usability of either type of connector style for 10BASE-T purposes. As the arrangement of the wires into pairs and the twisting of the pairs throughout the cable remain the same regardless of the EIA/TIA speciﬁcation being used, the two speciﬁcations can be considered equivalent. As the speciﬁcations terminate the wires into different arrangements, care must be taken to keep all the cables at a facility terminated to the same EIA/TIA standard. Failure to do so can result in the mis-association of wires at the connectors, making the cabling unable to provide a connection between Ethernet devices. The arrangement of the wires and pairs in the two EIA/TIA speciﬁcations is discussed in the UTP Cable portion of the Connector Types section of this chapter.

Keep in mind that the selection of an EIA/TIA wiring scheme determines the characteristics of Wallplates, Patch Panels, and other UTP interconnect hardware you add to the network. Most manufacturers supply hardware built to both of these speciﬁcations. The more common of the two speciﬁcations in 10BASE-T applications is EIA/TIA 568A.

Four-Pair Cable

The typical single UTP cable is a polyvinyl chloride (PVC) or plenum-rated plastic jacket containing four pairs of wire. The majority of facility cabling in current and new installations is four-pair cable of this sort. The dedicated single connections made using four-pair cable are easier to troubleshoot and replace than the alternative, bulk multipair cable such as 25-pair cable.

The jacket of each wire in a four-pair cable will have an overall color: brown, blue, orange, green, or white. In a four-pair UTP cable (the typical UTP used in networking installations) there is one wire each of brown, blue, green, and orange, and four wires whose overall color is white. The white wires are distinguished from one another by periodically placed (usually within 1/2 inch of one another) rings of the other four colors.

Wires with a unique base color are identiﬁed by that base color: blue, brown, green, or orange. Those wires that are primarily white are identiﬁed as white/<color>, where <color> indicates the color of the rings of the other four colors in the white insulator.

The 10BASE-T and 100BASE-TX standards are concerned with the use of two pairs, Pair 2 and Pair 3 (of either EIA/TIA 568 speciﬁcation). The 10BASE-T and 100BASE-TX standards conﬁgure devices to transmit over Pair 3 of the EIA/TIA 568A speciﬁcation (Pair 2 of EIA/TIA 568B), and to receive from Pair 2 of the EIA/TIA 568A speciﬁcation (Pair 3 of EIA/TIA 568B). The use of the wires of a UTP cable is shown in Table 4-1.

Cabling Types 4-7

Ethernet Media

Table 4-1. 10BASE-T/100BASE-TX Four-Pair Wire Use

Ethernet Signal Use

Wire Color EIA/TIA Pair

568A 568B

White/Blue (W-BL)

Pair 1 Not Used

Blue (BL)

White/Orange (W-OR)

Orange (OR) RX- TX-

White/Green (W-GR)

Green (GR) TX- RX-

White/Brown (W-BR)

Brown (BR)

NOTE

Twenty-Five Pair Cable

RX+ TX+

Pair 2

TX+ RX+

Pair 3

Pair 4 Not Used

Do not split pairs in a twisted pair installation. While you may consider combining your voice and data cabling into one piece of horizontal facility cabling, the Crosstalk and interference produced by this practice greatly reduces the viability of the cable for either application. The use of the pairs of cabling in this fashion can also prevent the future usage of advanced networking technologies such as FDDI TP-PMD and 100BASE-T4, that require the use of all four pairs in a twisted pair cable.

UTP cabling in large installations requiring several cable runs between two points is often 25-pair cable. This is a heavier, thicker form of UTP. The wires within the plastic jacket are of the same construction, and are twisted around associated wires to form pairs, but there are 50 individual wires twisted into 25 pairs in these larger cables. In most cases, 25-pair cable is used to connect wiring closets to one another, or to distribute large amounts of cable to intermediate distribution points, from which four-pair cable is run to the end stations.

4-8 Cabling Types

Ethernet Media

As with four-pair cable, the wires within a 25-pair cable are identiﬁed by color. The jacket of each wire in a 25-pair cable has an overall color: violet, green, brown, blue, red, orange, yellow, gray, black, and white. In a 25-pair UTP cable all wires in the cable are identiﬁed by two colors. The ﬁrst color is the base color of the insulator, while the second is the color of narrow bands painted onto the base color. These identifying rings are periodically placed on the wire, and repeat at regular intervals. When a wire is identiﬁed in a 25-pair cable, it is identiﬁed ﬁrst by its base color, and then further speciﬁed by the color of the bands or rings.

As a 25-pair cable can be used to make up to 12 connections between Ethernet stations (two wires in the 25-pair cable are typically not used), the wire pairs need to be identiﬁed not only as transmit or receive pairs, but what other pair they are associated with. There are two ways of identifying sets of pairs in a 25-pair cable. The ﬁrst is based on the connection of a 25-pair cable to a speciﬁc type of connector designed especially for it, the RJ21 connector. The second is based on connection to a punchdown block, a cable management device typically used to make the transition from a single 25-pair cable to a series of four-pair cables easier.

For further information on the RJ21 connector, refer to the Connector Types section later in this chapter. A description of punchdown blocks may be found in Chapter 13, Cabling Devices, and details of the punchdowns may be found in the Connector Types section later in this chapter.

Table 4-2. 25-Pair Cable Pair Mapping

Port Number Wire Use Wire Color

RX + White/Blue 26 A1 B1

RX - Blue/White 1 A2 B2

TX + White/Orange 27 A3 B3

TX - Orange/White 2 A4 B4

RX + White/Green 28 A5 B5

RX - Green/White 3 A6 B6

TX + White/Brown 29 A7 B7

TX - Brown/White 4 A8 B8

RX + White/Gray 30 A9 B9

RX - Gray/White 5 A10 B10

TX + Red/Blue 31 A11 B11

TX - Blue/Red 6 A12 B12

RJ21 Pin

Number

Punchdown

In Number

Punchdown

Out Number

Cabling Types 4-9

Ethernet Media

Table 4-2. 25-Pair Cable Pair Mapping (Continued)

Port Number Wire Use Wire Color

RX + Red/Orange 32 A13 B13

RX - Orange/Red 7 A14 B14

TX + Red/Green 33 A15 B15

TX - Green/Red 8 A16 B16

RX + Red/Brown 34 A17 B17

RX - Brown/Red 9 A18 B18

TX + Red/Gray 35 A19 B19

TX - Gray/Red 10 A20 B20

RX + Black/Blue 36 A21 B21

RX - Blue/Black 11 A22 B22

TX + Black/Orange 37 A23 B23

TX - Orange/Black 12 A24 B24

RX + Black/Green 38 A25 B25

RJ21 Pin Number

Punchdown

In Number

Punchdown

Out Number

RX - Green/Black 13 A26 B26

TX + Black/Brown 39 A27 B27

TX - Brown/Black 14 A28 B28

RX + Black/Gray 40 A29 B29

RX - Gray/Black 15 A30 B30

TX + Yellow/Blue 41 A31 B31

TX - Blue/Yellow 16 A32 B32

RX + Yellow/Orange 42 A33 B33

RX - Orange/Yellow 17 A34 B34

TX + Yellow/Green 43 A35 B35

TX - Green/Yellow 18 A36 B36

4-10 Cabling Types

Table 4-2. 25-Pair Cable Pair Mapping (Continued)

Ethernet Media

Port Number Wire Use Wire Color

RX + Yellow/Brown 44 A37 B37

RX - Brown/Yellow 19 A38 B38

TX + Yellow/Gray 45 A39 B39

TX - Gray/Yellow 20 A40 B40

RX + Violet/Blue 46 A41 B41

RX - Blue/Violet 21 A42 B42

TX + Violet/Orange 47 A43 B43

TX - Orange/Violet 22 A44 B44

RX + Violet/Green 48 A45 B45

RX - Green/Violet 23 A46 B46

TX + Violet/Brown 49 A47 B47

TX - Brown/Violet 24 A48 B48

N/A - 25 N/A N/A

Unused Pair

N/A - 50 N/A N/A

RJ21 Pin

Number

Punchdown

In Number

Punchdown

Out Number

Cabling Types 4-11

Ethernet Media

Crossovers

The 10BASE-T and 100BASE-TX speciﬁcations require that some UTP connections be crossed over. Crossing over is the reversal of the transmit and receive pairs at opposite ends of a single cable. Each cable that swaps the location of the transmit and receive pairs at only one end is called a crossover cable. Those cables that maintain the same pin numbers for transmit and receive pairs at both ends are called straight-through cables.

The 10BASE-T and 100BASE-TX speciﬁcations are designed around connections from networking hardware to end user stations being made through straight-through cabling. Because of this, the transmit wires of a networking device such as a standalone hub or repeater connect to the receive pins of a 10BASE-T or 100BASE-TX end station.

If two similarly-designed network devices are connected using a straight-through cable, the transmit pins of one device are connected to the transmit pins of the other device. In effect, the two devices will both attempt to transmit on the same pair of the cable between them.

To overcome this, a crossover must be placed between two like devices on a network, forcing the transmit pins of one device to connect to the receive pins of the other device. When two like devices are being connected to one another using UTP cabling, an odd number of crossover cables, preferably one, must be part of the cabling between them.

Tx+

Tx-

Rx-

Rx+

Tx+

Tx-

Rx-

Rx+

Path of Transmission

Straight-Through

Tx+ Tx-

RxRx+

Crossover

Rx+ Rx-

TxTx+

1845n06

Path of Transmission

Figure 4-6. Straight-Through vs. Crossover Cables

4-12 Cabling Types

UTP Cable Quality

Category 3

Ethernet Media

UTP cabling is produced in a number of overall quality levels, called Categories. The requirements of networking limit UTP cabling for Ethernet to Categories 3, 4, and 5. Any of these cable Categories can be used in an Ethernet installation, provided that the requisite IEEE 802.3 speciﬁcations regarding the cables are met.

UTP cabling that is built to the Category 3 speciﬁcation consists of two or more pairs of solid 24 AWG copper strands. Each strand, approximately 0.02 inch thick, is surrounded by a layer of insulation. The characteristics of the insulation are determined by the ﬁre resistant construction of the cable (plenum cable is thicker and made with slightly different material than normal PVC cabling).

The individual wires are twisted into pairs. The twisted pairs of cable are laid together within an outer jacket, that may be low-smoke PVC plastic or a plenum-rated insulating material. The outer jacket surrounds, but does not adhere to, the wire pairs that make up the cable.

Category 3 UTP cabling must not produce an attenuation of a 10 MHz signal greater than 98 dB/km at the control temperature of 20° C.

Category 4

Category 5

Category 4 UTP cabling is constructed in the same manner as the Category 3 cabling discussed previously. Category 4 UTP is constructed using copper center strands of 24 or 22 AWG. The resulting wire pairs are then covered by a second layer of insulating jacketing. Higher-quality materials and a closer association of the twisted pairs of wire improve the transmission characteristics of the cable in comparison to Category 3 cabling.

Category 4 UTP cabling must not produce an attenuation of a 10 MHz signal greater than 72 dB/km at the control temperature of 20° C.

Category 5 UTP cabling is manufactured in the same fashion as Category 3 cable, but the materials used are of higher quality and the wires that make up the pairs are more tightly wound than those in lower Category classes. This closer association helps to reduce the likelihood that any one member of a pair may be affected by external noise sources without the other member of the pair experiencing the same event. Only Category 5 cable may be used in 100BASE-TX networks.

Cabling Types 4-13

Ethernet Media

Fiber Optics

Category 5 UTP consists of 2 or more pairs of 22 or 24 AWG wire. Category 5 cable is constructed and insulated such that the maximum attenuation of a 10 MHz signal in a cable run at the control temperature of 20° C is 65 dB/km. A cable that has a maximum attenuation higher than 65 dB/km does not meet the Category 5 requirements.

Fiber optic cable is a high performance media constructed of glass or plastic that uses pulses of light as a transmission method. Because ﬁber optics do not utilize electrical charges to pass data, they are free of interference due to proximity to electrical ﬁelds. This, combined with the extremely low rate of signal degradation and dB loss makes ﬁber optics able to traverse extremely long distances. The actual maximums are dependent upon the architecture being used, but distances upwards of 2 kilometers (1.2 miles) are not uncommon.

Glass optical ﬁber is made up of a glass strand, the core, that allows for the easy transmission of light, the cladding, a less transmissive glass layer around the core that helps keep the light within the core, and a plastic buffer that protects the cable.

Cladding

Transmissive Core

PVC Buffer (Jacketing)

1845n07

Figure 4-7. Fiber Optic Cable Construction (multimode)

There are two basic types of ﬁber optics, multimode and single mode. The names come from the types of light used in the transmission process. Multimode ﬁber uses inexpensive Light Emitting Diodes (LEDs) that produce light of a single color. Due to the nature of the LED, the light produced is made up of a number of differing wavelengths of light, ﬁred outward from the center of the LED. Not all the rays of light enter the ﬁber, and those that do often do so at an angle, which reduces the amount of distance the signal can effectively cover. Single mode ﬁber optics use lasers to achieve greater maximum distances. Since light from a laser is all of the same wavelength, and travels in a coherent ray, the resulting signal tends to be much clearer at reception than an LED signal under the same circumstances.

4-14 Cabling Types

Ethernet Media

Fiber optics of both types are measured and identiﬁed by a variety of means. The usual means of referring to a ﬁber optic cable type is to identify if it is single mode or multimode, and to describe the thickness of each strand. Fiber optics are very thin, and the diameter of each strand is measured in microns (µm). Two measurements are important in ﬁber optic identiﬁcation; the diameter of the core, where signals travel, and the diameter of the cladding, which surrounds the core. Thus, ﬁber optic measurements will usually provide two numbers separated by the “/” symbol. The ﬁrst number is the diameter, in microns, of the core. The second is the diameter of the cladding. Thus, a 62.5/125 multimode cable is a type of ﬁber optic cabling with a 62.5 micron core and 125 micron cladding, which is commonly used by LED driven transmitting devices.

In much the same way that UTP cabling is available in two-, four-, 25-, and 50-pair cables, strands of ﬁber optic cabling are often bound together with other strands into multiple strand cables. These multiple strand cables are available with anywhere from two to 24 or more strands of ﬁber optics, all gathered together into one protective jacket.

Cabletron Systems recommends that customers planning to

TIP

install ﬁber optic cabling not install any facility ﬁber optics (non-jumper cabling) containing fewer than six strands of usable optical ﬁber . The minimum number of strands needed to make an end-to-end ﬁber optic link between two network devices is two (using the Ethernet network architecture). In the event that a strand within the cable is damaged during installation or additional ﬁber pairs become desired along the cable path, the availability of extra strands of optical ﬁber will reduce the likelihood that a new cable must be pulled. The existing, unused pairs of optical ﬁber can be terminated and used immediately.

Multimode

Multimode ﬁber optic cabling is designed and formulated to allow the propagation of many different wavelengths, or modes, of light. Multimode ﬁber optics are the most commonly encountered ﬁber type in Ethernet installations, due to their lower cost compared to other ﬁber types.

Multimode ﬁber optics may be terminated with any type of ﬁber optic connector; SMA, ST, FDDI MIC, or the new and not currently standardized SC connector.

Cabling Types 4-15

Ethernet Media

Single Mode

Single mode ﬁber optics are designed speciﬁcally to allow the transmission of a very narrow range of wavelengths within the core of the ﬁber. As the precise wavelength control required to accomplish this is performed using lasers, which direct a single, narrow ray of light, the transmissive core of single mode ﬁber optics is typically very small (8 to 10 µm). Single mode ﬁber is more expensive to produce than multimode ﬁber, and is typically used in long-haul applications.

Due to the very demanding tolerances involved in connecting two transmissive media with diameters approximately one-quarter as thick as a sheet of paper, single mode ﬁber optics require very precise connectors that will not move or shift over time. For this reason, single mode ﬁber optics should only be terminated with locking, preferably keyed, connectors. Fiber optic connector types such as the ST, SC, or FDDI MIC connector all meet the requirements of single mode ﬁber optics, if installed and tested properly.

4-16 Cabling Types

Connector Types

AUI

AUI cabling is always connected with DB15 ports and connectors. The use of any other type of connector for AUI cable is a violation of the IEEE 802.3 speciﬁcation and is considered nonstandard.

DB15

The DB15 connector (male or female) provides 15 pins or channels (depending on gender). For identiﬁcation, these pins are numbered from 1 to 15. To identify the number of a pin, look at the front of the connector, holding the DB15 as shown in Figure 4-8, below, keeping the longer edge of the D-shaped connector up.

Ethernet Media

Female

Channel #15 Channel #1

Pin #1

Pin #15

Male

1845n08

Figure 4-8. DB15 Connectors

The channel located at the upper right-hand corner of the female DB15 connector is identiﬁed as channel 1. The numbering continues across the top of the connector, to channel 8 at the upper left-hand corner. The channels from 9 to 15 are the seven channels at the bottom of the connector, from the lower right-hand corner (9) to the lower left-hand corner (15). The male DB15 connector reverses the left-right order of numbering, placing pin 1 at the upper left-hand corner, then following the path across and down to pin 15 at the lower right-hand corner.

The wires of an AUI cable are connected to different locations (pins or channels) of the male and female DB15 connectors. The differing organizations are called “pinouts.” The standard Ethernet DB15 pinout is discussed below.

Connector Types 4-17

Ethernet Media

Table 4-3. AUI Pinouts

AUI Connector Pin Wire Function

1 Logic Ref

2 Collision +

3 Transmit +

4 Logic Ref

5 Receive +

6 Power Return

7 No Connection

8 Logic Ref

9 Collision -

10 Transmit -

11 Logic Ref

12 Receive -

13 Power (+12 Vdc)

14 Logic Ref

15 No Connection

4-18 Connector Types

Coaxial Cable

N-Type

Ethernet Media

The connectors available for coaxial cabling are dependent upon the type of coaxial cabling in question. Thick coaxial cable may be tapped into without breaking the continuity of the cable or may be physically cut and re-connected. Thin coaxial cable cannot support the non-intrusive tap style, and must be split and connected to a junction device at each point where a connection is to be made.

N-Type connectors are used for the termination of thick coaxial cables and also for the connection of transceivers to the cable. When used to provide a transceiver tap, the coaxial cable is broken at an Annular Ring and two N-Type connectors are attached to the resulting bare ends. These N-Type connectors, once in place, are screwed onto a barrel housing. The barrel housing contains a center channel that the signals of the cable are passed across, and a pin or cable that contacts this center channel, providing access to and from the core of the coaxial cable. The pin that contacts the center channel is connected to the transceiver assembly and provides the path for Ethernet transmission and reception.

Crimping Sleeve

Coaxial Cable

Terminator Barrel

Figure 4-9. N-Type Connector and Terminator

Threaded Connector

Center Channel

Threaded Connector

Center Pin

Insulator

1845n09

Connector Types 4-19

Ethernet Media

Non-Intrusive

Thick coaxial cables require termination with N-Type connectors. As the coaxial cable carries network transmissions as voltage, both ends of the thick coaxial cable must be terminated with N-Type connectors and terminators to keep the signal from reﬂecting throughout the cable, which would disrupt network operation. The terminators used for thick coaxial cable are 50 Ohm (Ω) terminators. These terminators are screwed into an N-Type connector placed at the end of a run of thick coaxial cabling.

Tapping a thick coaxial cable may be done without breaking the cable itself. The non-intrusive, or “vampire” tap (Figure 4-10), inserts a solid pin through the thick insulating material and shielding of the coaxial cable. The solid pin reaches in through the insulator to the core wire where signals pass through the cable. By contacting the core, the pin creates a tap. The signals travel through the pin to and from the core.

Non-Intrusive taps are made up of saddles, which bind the connector assembly to the cable, and tap pins, which burrow through the insulator to the core wire. Non-Intrusive connector saddles are clamped to the cable to hold the assembly in place, and usually are either part of, or are easily connected to, an Ethernet transceiver assembly.

Compression

Screw

Annular Ring

Tap Pin

("stinger")

Transceiver

Contact

1845n10

Figure 4-10. Non-Intrusive Tap and Cable Saddle

The non-intrusive tap’s cable saddle is then inserted into a transceiver assembly (Figure 4-11). The contact pin, that carries the signal from the tap pin’s connection to the coaxial cable core, makes a contact with a channel in the transceiver housing. The transceiver breaks the signal up and carries it to a DB15 connector, to which an AUI cable may be connected.

4-20 Connector Types

Cable Saddle

TRANSCEIVER

Ethernet Media

Coax Cable

Contact Pin

BNC

1845n11

AUI Connector

(Female)

Figure 4-11. Cable Saddle and Transceiver Assembly

The BNC connector, used in 10BASE2 environments, is an intrusive connector much like the N-Type connector used with thick coaxial cable (described above). The BNC connector (shown in Figure 4-12) requires that the coaxial cable be broken at an annular ring to make the connection. Two BNC connectors are either screwed onto or crimped to the resulting bare ends. Cabletron Systems recommends the use of the crimp-on BNC connectors for more stable and consistent connections. BNC connectors use the same pin-and-channel system to provide a contact that is used in the thick coaxial N-Type connector.

BNC Male connectors are attached to BNC female terminators or T-connectors (Figure 4-13). The outside metal housing of the BNC male connector has two guide channels that slip over corresponding locking key posts on the female BNC connector. When the outer housing is placed over the T-connector or terminator locking keys and turned, the connectors will snap securely into place.

Connector Types 4-21

Ethernet Media

T-Connector

Key Guide Channel

Locking Key

Metal Casing

Insulator

Solid Center Strand Hollow Center Channel

1845n12

Figure 4-12. BNC connectors

Connections from the cable to network nodes are typically made using T-connectors, which provide taps for additional runs of coaxial cable to workstations or network devices. T-connectors, as shown in Figure 4-13, below, provide three BNC connections, two of which attach to Male BNC connectors on the cable itself and one of which is used for connection to the Female BNC connection of a transceiver or Desktop Network Interface Card (DNI or NIC) on a workstation.

NOTE

4-22 Connector Types

1845n13

Figure 4-13. Thin Coax T-Connector

T-connectors should be attached directly to the BNC connectors of Network Interface Cards or other Ethernet devices. The single solid strand connector of a T-connector should not be attached to a coaxial jumper cable of any length.

UTP Cable

RJ45

Ethernet Media

The RJ45 connector is a modular, plastic connector that is often used in UTP cable installations. The RJ45 is a keyed connector, designed to be plugged into an RJ45 port only in the correct alignment. The connector is a plastic housing that is crimped onto a length of UTP cable using a custom RJ45 die tool. The connector housing is often transparent, and consists of a main body, the contact blades or “pins,” the raised key, and a locking clip and arm.

Contact Blades

Locking Arm

Locking Clip

1845n14

Figure 4-14. RJ45 Connector

The locking clip, part of the raised key assembly, secures the connector in place after a connection is made. When the RJ45 connector is inserted into a port, the locking clip is pressed down and snaps up into place. A thin arm, attached to the locking clip, allows the clip to be lowered to release the connector from the port. For a complete discussion of connecting and disconnecting RJ45 connectors, refer to Chapter 14, Connecting and Terminating.

RJ45 connectors for UTP cabling are available in two basic conﬁgurations; stranded and solid. These names refer to the type of UTP cabling that they are designed to connect to. The blades of the RJ45 connector end in a series of points that pierce the jacket of the wires and make the connection to the core. Different types of connections are required for each type of core composition.

A UTP cable that uses stranded core wires will allow the contact points to nest among the individual strands. The contact blades in a stranded RJ45 connector, therefore, are laid out with their contact points in a straight line. The contact points cut through the insulating material of the jacket and make contact with several strands of the core.

Connector Types 4-23

Ethernet Media

Solid Core

Staggered Teeth Clamp Core Wire

Insulator

Stranded Core

Inline Teeth Nest in Core Strands

Insulator

1845n15

Figure 4-15. Solid and Stranded RJ45 Blades

The solid UTP connector arranges the contact points of the blades in a staggered fashion. The purpose of this arrangement is to pierce the insulator on either side of the core wire and make contacts on either side. As the contact points cannot burrow into the solid core, they clamp the wire in the middle of the blade, providing three opportunities for a viable connection.

The contact pins and their associated wires are organized into what is known as a pinout. The pinout of a connector or port is the layout of the wires or cables coming into the connector. The pinout used in any connector is dependent upon the wiring speciﬁcation to which the cable is constructed. The 10BASE-T standard requires that all the cables used in the network end in connectors with particular pinouts. The pinout form required by the 10BASE-T standard is the EIA/TIA 568A speciﬁcation.

The EIA/TIA 568A speciﬁcation orders the pairs in a four-pair cable into the pinout shown in Figure 4-16, below. The RJ45 connector in Figure 4-16 is being viewed from the contact blade end, with the locking clip up.

Figure 4-16. EIA/TIA 568A Pair Association

4-24 Connector Types

Pair 3

Pair 2 Pair 1

W-OR BL W-BLGR OR W-BRW-GR BR

Pair 4

1845n16

RJ21 (Telco)

Ethernet Media

The EIA/TIA 568B speciﬁcation reverses the arrangement of Pair 1 and Pair 2, but does not change the association of pairs within the cable. The Universal Service Order Code, or USOC, a standard used for Token Ring network installations or some telephone wiring, uses a different pair association than EIA/TIA 568A. The USOC standard will cause a split pair condition in an IEEE 10BASE-T environment, causing a loss of network functionality. For further information on the differences between the standards, refer to the USOC and EIA/TIA speciﬁcations.

The RJ21 or “Telco” connector is another standard 10BASE-T connector type. The RJ21 connector is a D-shaped metal or plastic housing that is wired and crimped to a UTP cable made up of 50 wires, a 25-pair cable. The RJ21 connector can only be plugged into an RJ21 port. The connector itself is sizable, and the cables that it connects to are often quite heavy, so the RJ21 relies on a tight ﬁt and good cable management practices to keep itself in the port. Some devices may also incorporate a securing strap that wraps over the back of the connector and holds it tight to the port.

25-Pair Cable

Contact Pins

1845n17

Figure 4-17. The RJ21 Connector

The RJ21 is used in locations where 25-pair cable is being run either to stations or to an intermediary cable management device such as a patch panel or punchdown block. Due to the bulk of the 25-pair cable and the desirability of keeping the wires within the insulating jacket as much as possible, 25-pair cable is rarely run directly to Ethernet stations.

The RJ21 connector, when used in a 10BASE-T environment, must use the EIA/TIA 568A pinout scheme. The numbers of the RJ21 connector’s pins are detailed in Figure 4-18, below. The actual association of the wire colors into pairs and the organization that these pairs may use to connect to a punchdown block are discussed in the Cabling Types portion of this chapter.

Connector Types 4-25

Ethernet Media

1 2 3 4 5 6 7

ReceiveReceive

TransmitTransmit

8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25

26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43

44 45 46 47 48 49 50

1845n18

Figure 4-18. RJ21 Pinout Mapping for 10BASE-T

Punchdown Blocks

While not strictly a connector type, the punchdown block is a fairly common component in many Ethernet 10BASE-T installations that use 25-pair cable. The punchdowns are bayonet pins to which UTP wire strands are connected. The bayonet pins are arranged in 50 rows of four columns each. The pins that make up the punchdown block are identiﬁed by the row and column they are members of. Each of the four columns is lettered A, B, C, or D, from leftmost to rightmost. The rows are numbered from top to bottom, one to 50. Thus, the upper left hand pin is identiﬁed as A1, while the lower right hand pin is identiﬁed as D50.

4-26 Connector Types

Ethernet Media

ABCD

1845n19

Figure 4-19. Punchdown Block Mapping for UTP Cabling

Connector Types 4-27

Ethernet Media

Fiber Optics

As both multimode and single mode ﬁber optics use the same standard connector in the Ethernet 10BASE-FL and FOIRL speciﬁcations, both cabling types are treated in the section that follows. The recommended connector for 100BASE-FX networks is discussed in the closing pages of this section.

Straight-Tip

NOTE

categories; 10BASE-FP Passive Fiber Optic Star, 10BASE-FB Active Fiber Optic Backbone, and 10BASE-FL Active Fiber Optic Link. Cab letron Systems produces Ethernet products that comply with the 10BASE-FL speciﬁcation.

The 10BASE-FL standard and FOIRL speciﬁcation for Ethernet networks deﬁne one style of connector as being acceptable for both multimode and single mode ﬁber optic cabling - the Straight-Tip or ST connector (note that ST connectors for single mode and multimode ﬁber optics are different in construction and are not to be used interchangeably). Designed by AT&T, the ST connector replaces the earlier Sub-Miniature Assembly or SMA connector. The ST connector is a keyed, locking connector that automatically aligns the center strands of the ﬁber optic cabling with the transmission or reception points of the network or cable management device it is connecting to.

Side Elev. Front Elev.

Hollow Center Channel

The 10BASE-F speciﬁcation is broken up into three main

Solid Glass Center

Locking Key

Keyed Connector

Key Guide Channel

Cladding

1845n20

4-28 Connector Types

Figure 4-20. ST Connectors

SC Connector

Ethernet Media

The key guide channels of the male ST connector allow the ST connector to only be connected to a female ST connector in the proper alignment. The alignment keys of the female ST connector ensure the proper rotation of the connector and, at the end of the channel, lock the male ST connector into place at the correct attitude. An integral spring helps to keep the ST connectors from being crushed together, damaging the ﬁber optic cables. For a complete discussion of connecting and disconnecting ST connectors, refer to Chapter 14, Connecting and Terminating.

The SC connector is a gendered connector that is recommended for use in Fast Ethernet networks that incorporate multimode ﬁber optics adhering to the 100BASE-FX speciﬁcation. It consists of two plastic housings, the outer and inner. The inner housing ﬁts loosely into the outer, and slides back and forth with a travel of approximately 2 mm (0.08 in).

The inner housing ends in two ﬂoating ferrules, which are very similar to the ﬂoating ferrules used in the FDDI MIC connector. The 100BASE-FX speciﬁcation requires very precise alignment of the ﬁber optic strands in order to make an acceptable connection. In order to accomplish this, SC connectors and ports each incorporate “ﬂoating” ferrules that make the ﬁnal connection between ﬁbers. These ﬂoating ferrules are held in place relatively loosely. This arrangement allows the ferrules to move slightly when making a connection. This small amount of movement manages to accommodate the subtle differences in construction found from connector to connector and from port to port.

The sides of the outer housing are open, allowing the inner housing to act as a latching mechanism when the connector is inserted properly in an SC port.

Guide Keys

Sliding Latch

1845n28

"Floating" Ferrules

Figure 4-21. Fast Ethernet SC Connector

Connector Types 4-29

Ethernet Media

4-30 Connector Types

Chapter 5

Ethernet Network Requirements

This chapter provides test parameters and speciﬁcation requirements for Ethernet network cabling.

10BASE-T

All Cabletron Systems 10BASE-T products require that installed facility cabling and cable hardware meet the following minimum speciﬁcations. If a network cabling installation is not within the limitations presented here, the operation of the 10BASE-T products may be affected.

Cable T ype

10BASE-T network operations are more demanding than normal telephony, and thus require speciﬁc, high-quality cabling in order to function properly. The 10BASE-T speciﬁcation for Ethernet networks requires UTP cabling of Category 3, 4, or 5. Categories of UTP cabling below Category 3 may not meet the quality requirements of the networking speciﬁcation, and may therefore be unable to meet the tested characteristics listed below.

The Category of cabling used in a network installation is dependent upon all the components that make up the cabling run. If an installation utilizes Category 5 cabling, and the wallplates and patch panels to which that cabling is connected are Category 3 compliant, the cable does not meet the EIA/TIA end-to-end speciﬁcations for a Category 5 installation.

Insertion Loss (Attenuation)

The maximum allowable insertion loss for any 10BASE-T station on the Ethernet network is 11.5 dB at frequencies from 5 to 10 MHz. This calculation must take all cabling devices in the cable path into account. A typical insertion loss test must include the jumper cabling used at the station and at the wiring closet, and any patch panels, punchdown blocks, and wallplates in the installation.

5-1

Ethernet Network Requirements

The insertion loss characteristics of a cable are one of the main determinants of link length allowed by the Ethernet and 10BASE-T speciﬁcations. As long as a UTP cable does not exceed the total insertion loss of 11.5 dB, it may be any length up to 200 m (656 ft). The 200 meter maximum total length is based on the total allowable propagation delay in the network, and cannot be exceeded.

Impedance

Jitter

Delay

NOTE

Cabletron Systems 10BASE-T equipment requires that 10BASE-T cables in the Ethernet network have an impedance within the range of 75 - 165 Ω. Typical UTP cables used in Ethernet environments have an impedance between 85 to 150 Ω.

Jitter may be caused by intersymbol interference and reﬂection of signal. Networking technologies that rely on particular timing or clocking schemes may be affected by jitter due to excessive signal reﬂection. Any 10BASE-T cable installation should not exceed 5.0 ns of jitter. If a cable run meets the 10BASE-T impedance requirements (detailed above), jitter should not be a concern.

As longer cables are more susceptible to other limiting factors, Cabletron Systems does not recommend the installation of 10BASE-T cabling over 100 m in length.

The maximum propagation delay allowable on a 10BASE-T segment is 1 microsecond (µs). If an Ethernet signal is unable to traverse the entire length of an installed UTP cable run within 1 µs, Out of Window (OOW) errors will occur due to excessive delays between transmission of signals and notiﬁcation of collisions. This propagation delay requirement limits UTP cabling to a total maximum length of 200 m (656 ft).

NOTE

As longer cables are more susceptible to other limiting factors, Cabletron Systems does not recommend the installation of 10BASE-T cabling over 100 m in length.

5-2 10BASE-T

Crosstalk

25-Pair Cable

Four-Pair Cable

Ethernet Network Requirements

Crosstalk is electrical interference between wires. Crosstalk occurs when a cable strand absorbs signals from other wires that it is adjacent to. Excessive crosstalk can be caused by a break in the insulation or shielding that separates wires from one another in a bundle.

Ethernet UTP cables should be checked for Near-End Crosstalk, or NEXT, at installation. The allowable amount of NEXT for a UTP cable is dependent upon the type of cable used in the installation.

The acceptable amount of NEXT between pairs in a 25-pair cable is at least 60 dB for a 10 MHz link.

The acceptable amount of NEXT between pairs in a four-pair cable is not less than 60 dB for a 10 MHz link.

Noise

As “noise” is not a readily quantiﬁed and tested aspect of installed cables, there are no hard and fast rules for the amount of acceptable cable noise on a 10BASE-T segment. If a cable that meets all other requirements for 10BASE-T operation is experiencing an unusual number of errors, the introduction of noise may be a problem.

If you suspect noise of causing signal degradation, examine the cable or cables in question. If they are near possible sources of outside noise, such as lighting ﬁxtures, electric motors, or transformers, reroute the cable.

Other Considerations

UTP cabling, due to the small gauge of the wires it is constructed out of, is susceptible to changes in attenuation due to heat. In an installation that exceeds the control temperature of 20° C (68° F), the attenuation of PVC jacketed UTP cabling that is within the 11.5 dB limitations may fall outside the acceptable range. In installations where UTP cables are expected to be subjected to temperatures of 40° C (104° F) or greater, the use of plenum-jacketed cabling is recommended. The thicker insulating jacket of a plenum-rated cable reduces the susceptibility of that cable to heat-induced changes in attenuation characteristics.

10BASE-T 5-3

Ethernet Network Requirements

The IEEE 802.3 10BASE-T speciﬁcation requires that all 10BASE-T devices support UTP cables of not less than 100 m (328 ft) in length. This requirement does not factor in losses due to connectors, patch panels, punchdown blocks, or other cable management hardware, which introduce additional loss.

For each connector or other intrusive cable management device in the total link, subtract 12 m (39.4 ft) from the total allowable link length.

Length

The 10BASE-T standard speciﬁes that any 10BASE-T compliant device must be capable of transmitting an Ethernet signal not less than 100 m (328 ft) over a UTP cable segment that meets the minimum quality values listed above. As long as all speciﬁcations are met for the entire length of the cable, UTP cable segments can be run up to a maximum allowable length of 200 m (656 ft).

NOTE

As longer cables are more susceptible to noise and other limiting factors, Cabletron Systems does not recommend the installation of 10BASE-T cabling over 100 m in length.

10BASE-F (Multimode)

All Cabletron Systems 10BASE-F and FOIRL products require that installed facility cabling and cable hardware meet the following minimum speciﬁcations. If a network cabling installation is not within the limitations presented here, the operation of the 10BASE-F products may be affected.

Cable T ype

10BASE-F network devices require speciﬁc types of cabling. 10BASE-F multimode ﬁber optic devices manufactured by Cabletron Systems are able to support connections to and from the following types of multimode ﬁber optics:

• 50/125 µm

• 62.5/125 µm

• 100/140 µm

5-4 10BASE-F (Multimode)

Attenuation

Ethernet Network Requirements

Multimode ﬁber optic cables must be tested for attenuation with a ﬁber optic attenuation test set. The test set must be conﬁgured to determine attenuation of the cable at a wavelength of 850 nm. The attenuation test will conﬁrm or deny that the cable falls within an acceptable level. The acceptable level of attenuation for a cable is dependent upon the type of multimode ﬁber optic cable being tested. The acceptable levels of attenuation for the types of multimode ﬁber optic cabling supported by Cabletron Systems products are listed in Table 5-1 below:

Table 5-1. Multimode Fiber Optic Attenuation Limits

Insertion Loss

Delay

Cable Type

50/125 µm 13.0 dB

62.5/125 µm 16.0 dB 100/140 µm 19.0 dB

The 10BASE-F speciﬁcation allows for a total dB loss of 10 dB or less between any two stations or devices connected by ﬁber optic cabling. When calculating insertion loss, you must consider and count any loss introduced by ﬁber optic splices, barrel connectors, distribution boxes or other cable management devices. The typical dB loss for a splice or a connector is less than 1 dB. The loss statistics for any ﬁber optic cable management hardware should be available from the manufacturer.

As ﬁber optic cabling is often used to make connections between Ethernet repeaters or hubs, the 10BASE-F speciﬁcation allows a multimode ﬁber optic link to be conﬁgured such that the total propagation delay for the link is less than or equal to 25.6 µs one-way. Keep in mind, however, that propagation delay must be calculated for the entire network. If there are more stations than the one connected by your ﬁber optic link, you must also calculate the propagation delay for the longest of those station links.

Maximum

Attenuation

If there is any signal path whose total one-way propagation delay exceeds 25.6 µs, the Ethernet network is out of speciﬁcations, and error conditions may result. To eliminate propagation delay problems, incorporate some form of segmentation, such as bridging or routing, into the network to separate the problem signal paths from one another.

10BASE-F (Multimode) 5-5

Ethernet Network Requirements

Length

The 10BASE-F speciﬁcation limits a multimode ﬁber optic cable segment to 2 km or less. Assuming that a ﬁber optic cable meets all other limitations for 10BASE-F usage, it is possible to extend a multimode ﬁber optic link to an absolute maximum of 2 km. At a length of more than 2 km, the propagation delay introduced by the multimode ﬁber optic cable segment may exceed the 25.6 µs limit of the Ethernet speciﬁcation and cause excessive OOW errors. Cabletron Systems does not recommend the installation or use of any multimode ﬁber optic cable segment that exceeds 10BASE-F limitations of 2 km.

Older networking equipment for ﬁber optic connections may be built to the FOIRL speciﬁcation. FOIRL devices will support a multimode ﬁber optic link of up to 1 km.

Ethernet FOIRL (Single Mode)

All Cabletron Systems FOIRL products require that installed single mode ﬁber optic facility cabling and cable hardware meet the following minimum speciﬁcations. If a network cabling installation is not within the limitations presented here, the operation of the FOIRL products may be affected.

Cable T ype

Attenuation

FOIRL network devices require speciﬁc types of cabling. FOIRL single mode ﬁber optic devices manufactured by Cabletron Systems are able to support connections to and from the following types of single mode ﬁber optics:

• 8/125 µm

• 12/125 µm

Single mode ﬁber optic cabling must be tested with a ﬁber optic attenuation test set conﬁgured to determine attenuation of the cable at a wavelength of 1300 nm. The acceptable level of attenuation for a single mode ﬁber optic is less than or equal to 10.0 dB for any given link.

5-6 Ethernet FOIRL (Single Mode)

Insertion Loss

Delay

Ethernet Network Requirements

The FOIRL speciﬁcation allows for a total loss of 10 dB or less between any two stations or devices connected by ﬁber optic cabling. When calculating insertion loss, you must consider and count any loss introduced by ﬁber optic splices, barrel connectors, distribution boxes or other cable management devices. The typical dB loss for a splice or a connector is less than 1 dB. The loss statistics for any ﬁber optic cable management hardware should be available from the manufacturer.

If there is any signal path in the overall network whose total one-way propagation delay exceeds 25.6 µs, the Ethernet network is out of speciﬁcations, and error conditions may result. To eliminate propagation delay problems, incorporate some form of segmentation, such as bridging or routing, into the network to separate the problem signal paths from one another.

Length

The FOIRL speciﬁcation limits single mode ﬁber optic cabling links to a total of 1 km or less. If a single mode ﬁber optic cable is used to form a link between two bridges and shares no connection with other Ethernet stations, the total segment length may reach up to 5 km, assuming all other requirements for a FOIRL network are met. At lengths over 5 km, propagation delays for the ﬁber optic link exceed the 25.6 µs limit of Ethernet networks. Cabletron Systems does not recommend the installation or use of any single mode ﬁber optic cable segment that exceeds the FOIRL limitations of 1 km.

Ethernet FOIRL (Single Mode) 5-7

Ethernet Network Requirements

10BASE2

All Cabletron Systems 10BASE2 products require that installed thin coaxial cables and related cabling hardware meet the following minimum speciﬁcations. If a network installation does not comply with the following speciﬁcations, operation of the 10BASE2 products may be affected.

Cable T ype

Cabletron Systems 10BASE2 products are designed to be connected to 50 Ohm RG-58 A/U type coaxial cable. If Cabletron Systems products are connected to other types of thin coaxial cable, the 10BASE2 networks will be subject to errors and poor performance.

Termination

All 10BASE2 cables must be terminated at both ends of the cable with 50 Ohm terminators. Some 10BASE2 network equipment is capable of performing internal termination. If a network device supports internal termination, and that device is located at one end of the 10BASE2 cable, no external terminators need to be added to the cable segment.

Connectors/Taps

10BASE2 cables may only be terminated with BNC connectors. Connectors on the 10BASE2 cable must be spaced more than 0.5 m (1.64 ft) from any other connector or tap in the cable. If connectors are located closer to one another than this minimum, signal reﬂection may occur, causing network errors and a loss of performance.

One segment of 10BASE2 thin coaxial cable can support no more than 30 stations. When planning a thin coaxial cable segment that will connect to a bridge, repeater, or hub, keep in mind that one connection must be reserved for the network device, leaving a maximum of 29 stations that may be connected to one segment.

Connections from T-connectors to network devices may not be made through thin coaxial jumper cables; connections must be made from the T-connector directly to the device.

5-8 10BASE2

Grounding

Each thin coaxial cable segment should be connected to earth ground at only one point. The connection to a ground should not be made through the BNC ports of a network device or T-connector unless the connection to the ground is made through the BNC terminator at the end of the cable. The grounding wire must be connected to the outer metal shield of the coaxial cable and should be no longer than 10 m (32.8 ft). If insulated, grounding wires should be green in adherence with accepted wiring practice.

Length

10BASE2 speciﬁcations allow thin coaxial cable segments to be no longer than 185 m (606.7 ft). The use of longer cable segments can cause excessive error conditions and poor network operation.

10BASE5 (Coaxial Cable)

Ethernet Network Requirements

Cable T ype

Termination

The IEEE 802.3 10BASE5 speciﬁcation details the use of thick coaxial cabling and Attachment Unit Interface (AUI) cables. If a thick coaxial cable network does not meet the requirements listed here, operation of the 10BASE5 networking components may be adversely affected.

Cabletron Systems 10BASE5 transceivers are designed to be connected to IEEE

802.3-compliant 50 Ω thick coaxial cable with a core gauge of 12 AWG. If Cabletron Systems products are connected to other types of thin coaxial cable, the 10BASE5 network may be subject to errors and poor performance.

All 10BASE5 cables must be terminated at both ends of the cable with 50 Ω terminators. Any time an N-Type barrel connector or intrusive tap is removed from the thick coaxial cable segment, the segment or segments resulting from the cable split must be either reconnected or terminated at the resulting ends. Failure to terminate a thick coaxial cable segment can cause reﬂection of signal and the creation of excessive error conditions.

10BASE5 (Coaxial Cable) 5-9

Ethernet Network Requirements

Connectors/Taps

10BASE5 cables may be terminated with intrusive (N-Type) connectors or tapped by coring through the cable to the transmissive core wire. Termination of the cable segment must be accomplished with intrusive connectors. Connectors or taps on the 10BASE5 cable must be spaced no less than 2.5 m (8.2 ft) from one another or the cable termination. If connectors are located closer to one another than this minimum, a loss of network performance may result.

One segment of 10BASE5 cabling can support up to 100 taps or intrusive connectors. This number does not count the terminating connectors at each end of the cable as taps.

Grounding

Each thick coaxial cable segment should be connected to earth ground at only one point. The connection to a ground should not be made through an N-Type connector unless the connection to the ground is made through the N-Type terminator at the end of the cable. The grounding wire must be connected to the outer metal shield of the coaxial cable and should be no longer than 10 m (3.28 ft). If insulated, grounding wires should be green in adherence with accepted wiring practice.

Length

10BASE5 speciﬁcations allow a thick coaxial cable segment to be no longer than 500 meters (1,646 ft). The use of longer cable segments can cause excessive error conditions and poor network performance.

5-10 10BASE5 (Coaxial Cable)

Chapter 6

Full-Duplex Ethernet Network Requirements

This chapter provides test parameters and speciﬁcation requirements for Full-Duple x Ethernet network cabling.

Full-Duplex 10BASE-T

All Cabletron Systems Full-Duplex 10BASE-T products require that installed facility cabling and cable hardware meet the following minimum speciﬁcations. If a network cabling installation is not within the limitations presented here, the operation of the 10BASE-T products may be affected.

Cable T ype

Note that Full-Duplex Ethernet links are dependent upon dedicated links from one Ethernet switch to another Ethernet switch or from one Ethernet switch to a single workstation. Both the end devices must be capable of operating in full-duplex mode.

Network operations using 10BASE-T are more demanding than normal telephony, and thus require speciﬁc, high-quality cabling in order to function properly. The 10BASE-T speciﬁcation for Ethernet networks requires UTP cabling of Category 3, 4, or 5. Categories of UTP cabling below Category 3 may not meet the quality requirements of the networking speciﬁcation, and may therefore be unable to meet the tested characteristics listed below.

The Category of cabling used in a network installation is dependent upon all the components that make up the cabling run. If an installation utilizes Category 5 cabling, and the wallplates and patch panels to which that cabling is connected are Category 3 compliant, the cable will not meet the EIA/TIA end-to-end speciﬁcations for a Category 5 installation.

6-1

Full-Duplex Ethernet Network Requirements

Insertion Loss (Attenuation)

Impedance

Jitter

Delay

NOTE

Cabletron Systems 10BASE-T equipment requires that 10BASE-T cables in the Ethernet network have an impedance within the range of 75 to 165 Ω. Typical UTP cables used in Ethernet environments have an impedance between 85 and 150 Ω.

As longer cables are more susceptible to other limiting factors, Cabletron Systems does not recommend the installation of 10BASE-T cabling over 100 m in length.

As Full-Duplex Ethernet operation eliminates the possibility of collisions occurring, total media length for a Full-Duplex link is determined by signal strength, noise, and jitter. Delay is not a factor in Full-Duplex Ethernet network cabling design.

6-2 Full-Duplex 10BASE-T

Crosstalk

25-Pair Cable

Four-Pair Cable

Full-Duplex Ethernet Network Requirements

Crosstalk is electrical interference between wires. Crosstalk occurs when a cable strand absorbs signals from adjacent wires. Excessive crosstalk can be caused by a break in the insulation or shielding that separates wires from one another in a bundle.

Ethernet UTP cables should be checked for Near-End Crosstalk, or NEXT, at installation. The allowable amount of NEXT for a UTP cable is dependent upon the type of cable used in the installation.

The acceptable amount of NEXT between pairs in a 25-pair cable is at least 60 dB for a 10 MHz link.

The acceptable amount of NEXT between pairs in a four-pair cable is not less than 60 dB for a 10 MHz link.

Noise

If you suspect that noise is causing signal degradation, examine the cable or cables in question. If they are near possible sources of outside noise, such as lighting ﬁxtures, electric motors, or transformers, reroute the cable.

Other Considerations

Due to the small gauge of the wires which make up UTP cabling, it is susceptible to changes in attenuation due to heat. If the temperature at the installation site exceeds the control temperature of 20°C (68°F), the attenuation of PVC jacketed UTP cabling that is within the 11.5 dB limitations may fall outside the acceptable range. In installations where UTP cables are expected to be subjected to temperatures of 40° C (104° F) or greater, the use of plenum-jacketed cabling is recommended. The thicker insulating jacket of a plenum-rated cable reduces the susceptibility of that cable to heat-induced changes in attenuation characteristics.

Full-Duplex 10BASE-T 6-3

Full-Duplex Ethernet Network Requirements

For each connector or other intrusive cable management device in the total link, subtract 12 m (39.4 ft) from the total allowable link length.

Length

NOTE

As longer cables are more susceptible to noise and other limiting factors, Cabletron Systems does not recommend the installation of 10BASE-T cabling over 100 m in length.

10BASE-F (Multimode)

Cable T ype

Networking devices built to the 10BASE-F standard require speciﬁc types of cabling. The 10BASE-F multimode ﬁber optic devices manufactured by Cabletron Systems are able to support connections to and from the following types of multimode ﬁber optics:

• 50/125 µm

• 62.5/125 µm

• 100/140 µm

6-4 10BASE-F (Multimode)

Attenuation

Full-Duplex Ethernet Network Requirements

Table 6-1. Multimode Fiber Optic Attenuation Limits

Insertion Loss

Delay

Cable Type

50/125 µm 13.0 dB

62.5/125 µm 16.0 dB 100/140 µm 19.0 dB

The 10BASE-F speciﬁcation allows for a total dB loss of 10.0 dB or less between any two stations or devices connected by ﬁber optic cabling. When calculating insertion loss, you must consider and count any loss introduced by ﬁber optic splices, barrel connectors, distribution boxes or other cable management devices. The typical dB loss for a splice or a connector is less than 1 dB. The loss statistics for any ﬁber optic cable management hardware should be available from the manufacturer.

As is the case with Full-Duplex 10BASE-T operation, Full-Duplex 10BASE-F operation eliminates the possibility of collisions on a network link. Again, for interoperability with the half-duplex 10BASE-F speciﬁcations, Cabletron Systems recommends that a 10BASE-F link not exceed 5 km in length or 25.6 µs of total one-way propagation delay.

Maximum

Attenuation

10BASE-F (Multimode) 6-5

Full-Duplex Ethernet Network Requirements

Length

Older networking equipment for ﬁber optic connections may be built to the FOIRL speciﬁcation. FOIRL devices will support a multimode ﬁber optic link of up to 1 km.

Ethernet FOIRL (Single Mode)

Cable T ype

Attenuation

• 8/125 µm

• 12/125 µm

Some Cabletron Systems single mode ﬁber optic devices may be connected to multimode ﬁber optic cabling with measurements of 62.5/125 µm, but the greater optical loss characteristics of multimode ﬁber optics will limit the maximum distance of the single mode ﬁber optic signal to approximately 2 km. Connecting single mode devices to multimode ﬁber optic cabling is not recommended and is not compliant with the FOIRL speciﬁcation.

6-6 Ethernet FOIRL (Single Mode)

Insertion Loss

Delay

Full-Duplex Ethernet Network Requirements

The FOIRL speciﬁcation allows for a total loss of 10.0 dB or less between any two stations or devices connected by ﬁber optic cabling. When calculating insertion loss, you must consider and count any loss introduced by ﬁber optic splices, barrel connectors, distribution boxes or other cable management devices. The typical dB loss for a splice or a connector is less than 1 dB. The loss statistics for any ﬁber optic cable management hardware should be available from the manufacturer.

Length

Ethernet FOIRL (Single Mode) 6-7

Full-Duplex Ethernet Network Requirements

6-8 Ethernet FOIRL (Single Mode)

Chapter 7

Fast Ethernet Network Requirements

This chapter provides test parameters and speciﬁcation requirements for Fast Ethernet network cabling.

100BASE-TX

All Cabletron Systems 100BASE-TX products require that installed facility cabling and cable hardware meet the following minimum speciﬁcations. If a network cabling installation is not within the limitations presented here, the operation of the 100BASE-TX products may be affected.

Cable T ype

The operation of a 100BASE-TX network is more demanding than that of standard Ethernet, and high-quality cables are required. The 100BASE-TX speciﬁcation for Fast Ethernet networks requires UTP cabling Category 5. Categories of UTP cabling below Category 5 may not meet the quality requirements of the networking speciﬁcation, and may therefore be unable to meet the tested characteristics listed below.

NOTE

Due to the construction of the connectors and organization of wires, the 25-pair RJ21 connector is not Category 5 compliant.

7-1

Fast Ethernet Network Requirements

The TIA/EIA 568A cabling speciﬁcation for Category 5 compliant UTP installations allows the use of two different types of cable: horizontal wire and patch wire. The speciﬁcation allows horizontal wire to be used to cover distances of up to 90 m, while patch wire is restricted to a maximum length of 10 m.

NOTE

Horizontal wire must be constructed with solid core wires. Horizontal wire is intended to be used as the “in-the-wall” cabling of the network. Patch wire is constructed with more ﬂexible stranded core wires, and is useful in situations where bending or movement of the wire is expected. Patch wire should only be used for connections between punchdown blocks, patch panels, or workstations.

A third type of TIA/EIA 568 A cab ling, backbone wire , does not apply to this implementation of the 100BASE-TX standard, and is not discussed in this chapter.

Insertion Loss (Attenuation)

The maximum allowable insertion loss for any 100BASE-TX station on the Fast Ethernet network is 24.0 dB at a frequency of 100 MHz. This calculation must take all cabling devices in the cable path into account. A typical insertion loss test must include the jumper cabling used at the station and at the wiring closet, and any patch panels, punchdown blocks, and wallplates in the installation.

Impedance

Cabletron Systems 100BASE-TX equipment requires that 100BASE-TX cables in the Fast Ethernet network have an impedance within the range of 75 to 165 Ω. Typical UTP cables used in Fast Ethernet environments have an impedance between 85 and 111 Ω.

Jitter

Jitter may be caused by intersymbol interference and reﬂection of signal. Networking technologies that rely on particular timing or clocking schemes may be affected by jitter due to excessive signal reﬂection. Any 100BASE-TX cable installation should not exceed 1.4 ns of jitter. If a cable run meets the 100BASE-TX impedance requirements (detailed above), jitter should not be a concern.

7-2 100BASE-TX

Delay

Crosstalk

Noise

Fast Ethernet Network Requirements

The maximum propagation delay allowable on a 100BASE-TX segment is 1 microsecond (µs). If a Fast Ethernet signal is unable to traverse the entire length of an installed UTP cable run within 1 µs, Out of Window (OOW) errors will occur due to excessive delays between transmission of signals and notiﬁcation of collisions. This propagation delay requirement limits UTP cabling to a total maximum length of 100 m (328 ft).

Fast Ethernet UTP cables should be checked for Near-End Crosstalk, or NEXT, at installation. The acceptable amount of NEXT between pairs in a four-pair cable is not less than 27 dB for a 100 MHz link.

As “noise” is not a readily quantiﬁed and tested aspect of installed cables, there are no hard and fast rules for the amount of acceptable cable noise on a 100BASE-TX segment. If a cable that meets all other requirements for 100BASE-TX operation is experiencing an unusual number of errors, the introduction of noise may be a problem.

Other Considerations

Due to the small gauge of the wires in a UTP cable, it is susceptible to changes in attenuation due to heat. In an installation that exceeds the control temperature of 20° C (68° F), the attenuation of PVC jacketed UTP cabling that is within the 11 dB limitations may fall outside the acceptable range of attenuation. In installations where UTP cables are expected to be subjected to temperatures of 40° C (104° F) or greater, the use of plenum-jacketed cabling is recommended. The thicker insulating jacket of a plenum-rated cable reduces the susceptibility of that cable to heat-induced changes in attenuation characteristics.

The IEEE 802.3 100BASE-TX speciﬁcation requires that all 100BASE-TX devices support UTP cables up to 100 m (328 ft) in length. This requirement does not factor in losses due to connectors, patch panels, punchdown blocks, or other cable management hardware, which introduce additional loss.

For each connector or other intrusive cable management device in the total link, subtract 12 m (39.4 ft) from the total allowable link length for purposes of estimation.

100BASE-TX 7-3

Fast Ethernet Network Requirements

100BASE-FX (Multimode)

All Cabletron Systems 100BASE-FX products require that installed facility cabling and cable hardware meet the following minimum speciﬁcations. If a network cabling installation is not within the limitations presented here, the operation of the 100BASE-FX products may be affected.

Cable T ype

Networking devices built to the 100BASE-FX speciﬁcation require speciﬁc types of cabling. 100BASE-FX multimode ﬁber optic devices manufactured by Cabletron Systems are able to support connections to and from 62.5/125 µm multimode ﬁber optics.

Attenuation

Insertion Loss

The 100BASE-FX speciﬁcation allows for a total dB loss of 10.0 dB or less between any two stations or devices connected by ﬁber optic cabling. When calculating insertion loss, you must consider and count any loss introduced by ﬁber optic splices, barrel connectors, distribution boxes or other cable management devices. The typical dB loss for a splice or a connector is less than 1 dB. The loss statistics for any ﬁber optic cable management hardware should be available from the manufacturer.

7-4 100BASE-FX (Multimode)

Delay

Length

Fast Ethernet Network Requirements

As ﬁber optic cabling is often used to make connections between Fast Ethernet repeaters or hubs, the 100BASE-FX speciﬁcation allows a multimode ﬁber optic link to be conﬁgured such that the total propagation delay for the link is less than or equal to 2.56 µs one-way. Keep in mind, however, that propagation delay must be calculated for the entire network. If there are more stations than the one connected by your ﬁber optic link, you must also calculate the propagation delay for the longest of those station links.

If the total one-way propagation delay of any signal path exceeds 2.56 µs, the Fast Ethernet network is out of speciﬁcations, and error conditions may result. To eliminate propagation delay problems, incorporate some form of segmentation, such as bridging or routing, into the network to separate the problem signal paths from one another.

2.56 µs limit of the Fast Ethernet speciﬁcation and cause excessive OOW errors. Cabletron Systems does not recommend the installation or use of any multimode ﬁber optic cable segment that exceeds 100BASE-FX limitations of 412 m.

Hybrid Installations

In Fast Ethernet networks, the combining of ﬁber optic and unshielded twisted pair media in a single, repeated network requires calculating a network radius. This is because the delay requirements for a Fast Ethernet network are so demanding that a mixed-media network must take the differences between the standard media into account.

The network radius is the calculation of the longest path in the Fast Ethernet repeater domain (from one station to a Fast Ethernet repeater and out to another station). Figure 7-1 shows an example of a mixed media Fast Ethernet repeater domain.

Hybrid Installations 7-5

Fast Ethernet Network Requirements

If the two longest links in the Fast Ethernet repeater domain are both made using UTP cable, each UTP segment may be 100 m in length, for a total network radius of 200 m. If these links were both made using multimode ﬁber optics, the allowable maximum network radius would be 272 m, less than that allowed by a repeater with a single 100BASE-FX link.

When media are mixed in a Fast Ethernet network, the allowable network radius changes slightly. In a mixed UTP and multimode ﬁber optic network, the maximum radius is 263 m. This means that the longest UTP segment in the Fast Ethernet network may be up to 100 m, and the longest 100BASE-FX link may be 160 m. The maximum network radius for each Fast Ethernet media conﬁguration is provided in Table 7-1.

Repeater Classes

Repeaters in Fast Ethernet networking are divided into two categories, or “classes” by the 100BASE-TX standard. The difference between these Class I and Class II repeaters is the method each uses to handle received signals for transmission. The different techniques result in different rules of conﬁguration for a Fast Ethernet network.

Link A

Fast Ethernet Repeater

Figure 7-1. Fast Ethernet Network Radius

Link B

1845n29a

Class I repeaters receive the 100BASE-TX electrical signal on one interface and translate that signal from its electrical form into a digital series, much in the same way that a Fast Ethernet station receives a transmission. The Class I repeater then generates a new signal on each of its interfaces using the translated digital series. The Class I repeater does not make any decisions based of the received signal, nor does it perform any error-checking. The translation of the received signal is intended to improve the strength and validity of the repeated Fast Ethernet frame.

The Class II repeater receives and immediately repeats each received transmission without performing any translation. The repeating process is a simple electrical duplication and strengthening of the signal.

7-6 Hybrid Installations

The design and operation of these different repeater types result in different operating characteristics and network limitations. Class I repeaters, by translating the received signal, produce a stronger repeated transmission. The translation process, however, takes up a number of microseconds. This additional delay reduces the total distance a signal may travel before the allowable delay for that transmission has elapsed. While Class II repeaters are faster, the signals they produce are less precise, and they cannot connect to different media types.

These differences mean that, in any Fast Ethernet network, there may be a maximum of one Class I or two Class II repeaters between any two end stations. These implementations also result in different maximum network radii, as shown in Table 7-1.

Buffered Uplinks

Several Fast Ethernet devices support the incorporation of buffered uplinks to help alleviate the pressures placed on network design by the small network radius of Fast Ethernet networks. The buffered uplink acts as a non-ﬁltering bridge, providing little more than retiming and regeneration of signals. In effect, the buffered uplink provides only the distance characteristics of a bridged connection. Fast Ethernet networks that incorporate a buffered uplink effectively extend the maximum network radius. The multimode ﬁber optic buffered uplink can be up to 400 m in length. The overall allowable network radius for Fast Ethernet networks that incorporate buffered uplinks are also provided in Table 7-1.

Fast Ethernet Network Requirements

Table 7-1. Fast Ethernet Maximum Network Radii

Repeater

Class

Class I 200 m 260 m 272 m 500 m 800 m

Class II 200 m N/A 320 m N/A N/A

UTP

UTP & Fiber

Optics

Fiber Optics

UTP &

Buffered

Uplink

Fiber Optics

and Buffered

Uplink

Hybrid Installations 7-7

Fast Ethernet Network Requirements

7-8 Hybrid Installations

Chapter 8

Full-Duplex Fast Ethernet Network Requirements

This chapter provides test parameters and speciﬁcation requirements for Full-Duplex Fast Ethernet network cabling.

100BASE-TX

Cable T ype

It is important to remember that full-duplex Fast Ethernet operation requires dedicated single links from one port of a Fast Ethernet switch to another Fast Ethernet switch or a Fast Ethernet workstation. If both endstations are not capable of full-duplex operation, a standard Fast Ethernet link will be automatically established.

100BASE-TX network operations are more demanding than those of standard Ethernet, and high-quality cables are required. The 100BASE-TX speciﬁcation for Fast Ethernet networks requires UTP cabling meeting Category 5 speciﬁcations. Categories of UTP cabling below Category 5 may not meet the quality requirements of the networking speciﬁcation, and may therefore be unable to meet the tested characteristics listed below.

8-1

Full-Duplex Fast Ethernet Network Requirements

Insertion Loss (Attenuation)

The maximum allowable insertion loss for any 100BASE-TX station on the Fast Ethernet network is 11.5 dB at frequencies from 5 to 10 MHz. This calculation must take all cabling devices in the cable path into account. A typical insertion loss test must include the jumper cabling used at the station and at the wiring closet, and any patch panels, punchdown blocks, and wallplates in the installation.

The insertion loss characteristics of a cable are one of the main determinants of link length allowed by the Fast Ethernet and 100BASE-TX speciﬁcations. As long as a UTP cable does not exceed the total link length of 11.5 dB, it may be any length up to 100 m (328 ft). The 100 meter maximum total length is based on the total allowable propagation delay in the network, and cannot be exceeded.

Impedance

Jitter

Crosstalk

NOTE

Jitter may be caused by intersymbol interference and reﬂection of signal. Networking technologies that rely on particular timing or clocking schemes may be affected by jitter due to excessive signal reﬂection. Any 100BASE-TX cable installation should not exceed 1.4 ns of jitter. If a cable run meets the 100BASE-TX impedance requirements (detailed above), jitter should not be a concern.

As longer cables are more susceptible to other limiting factors, Cabletron Systems does not recommend the installation of 100BASE-TX cabling over 100 m in length.

Fast Ethernet UTP cables should be checked for Near-End Crosstalk, or NEXT, at installation. The allowable amount of NEXT for a UTP cable is dependent upon the type of cable used in the installation.

8-2 100BASE-TX

25-Pair Cable

Full-Duplex Fast Ethernet Network Requirements

The acceptable amount of NEXT between pairs in a 25-pair cable is at least 60 dB for a 10 MHz link.

Four-Pair Cable

Noise

NOTE

The acceptable amount of NEXT between pairs in a four-pair cable is not less than 60 dB for a 10 MHz link.

Due to the construction of the connectors and organization of wires, the 25-pair RJ21 connector is not Category 5 compliant.

Other Considerations

Due to the small gauge of the wires in UTP cabling, it is susceptible to changes in attenuation due to heat. In an installation that exceeds the control temperature of 20° C (68° F), the attenuation of PVC jacketed UTP cabling that is within the 11.5 dB limitations may fall outside the acceptable range. In installations where UTP cables are expected to be subjected to temperatures of 40° C (104° F) or greater, the use of plenum-jacketed cabling is recommended. The thicker insulating jacket of a plenum-rated cable reduces the susceptibility of that cable to heat-induced changes in attenuation characteristics.

The IEEE 802.3 100BASE-TX speciﬁcation requires that all 100BASE-TX devices support UTP cables of not less than 100 m (328 ft) in length. This requirement does not factor in losses due to connectors, patch panels, punchdown blocks, or other cable management hardware, which introduce additional loss.

For each connector or other intrusive cable management device in the total link, subtract 12 m (39.4 ft) from the total allowable link length.

100BASE-TX 8-3

Full-Duplex Fast Ethernet Network Requirements

Length

The 100BASE-TX standard speciﬁes that any 100BASE-TX compliant device must be capable of transmitting a Fast Ethernet signal not less than 100 m (328 ft) over a UTP cable segment that meets the quality values listed above. As long as all speciﬁcations are met for the entire length of the cable, UTP cable segments can be run up to a maximum allowable length of 260 m (852 ft).

NOTE

As longer cables are more susceptible to noise and other limiting factors, Cabletron Systems does not recommend the installation of 100BASE-TX cabling over 100 m in length.

8-4 100BASE-TX

100BASE-FX (Multimode)

Cable T ype

Cabletron Systems 100BASE-FX network devices require speciﬁc types of cabling. 100BASE-FX multimode ﬁber optic devices manufactured by Cabletron Systems are able to support connections to and from the following types of multimode ﬁber optics:

• 50/125 µm

• 62.5/125 µm

• 100/140 µm

Full-Duplex Fast Ethernet Network Requirements

Attenuation

Insertion Loss

Delay

The 100BASE-FX speciﬁcation allows for a total dB loss of 10 dB or less between any two stations or devices connected by ﬁber optic cabling. When calculating insertion loss, you must consider and count any loss introduced by ﬁber optic splices, barrel connectors, distribution boxes or other cable management devices. The typical dB loss for a splice or a connector is less than 1 dB. The loss statistics for any ﬁber optic cable management hardware should be available from the manufacturer.

100BASE-FX (Multimode) 8-5

Full-Duplex Fast Ethernet Network Requirements

If there is any signal path whose total one-way propagation delay exceeds 2.56 µs, the Fast Ethernet network is out of speciﬁcations, and error conditions may result. To eliminate propagation delay problems, incorporate some form of segmentation, such as bridging or routing, into the network to separate the problem signal paths from one another.

Length

The 100BASE-FX speciﬁcation limits a multimode ﬁber optic cable segment to 412 m or less. Assuming that a ﬁber optic cable meets all other limitations for 100BASE-FX usage, it is possible to extend a multimode ﬁber optic link to an estimated maximum of 2 km. At a length of more than 2 km, the propagation delay introduced by the multimode ﬁber optic cable segment may exceed the 2.56 µs limit of the Fast Ethernet speciﬁcation and cause excessive OOW errors. Cabletron Systems does not recommend the installation or use of any multimode ﬁber optic cable segment that exceeds 100BASE-FX limitations of 412 m.

8-6 100BASE-FX (Multimode)

Chapter 9

Token Ring Media

This chapter examines the physical characteristics and requirements of both cabling and the connectors and ports used in Token Ring networks.

Cabling T ypes

Shielded Twisted Pair (STP)

Shielded Twisted Pair cabling is a multistranded cable most often constructed of eight 26 AWG conductive copper solid or stranded core wires. Each wire is surrounded by a non-conductive insulating material such as Polyvinyl Chloride (PVC). These wires are twisted around one another in a speciﬁc arrangement to form pairs. The pairs are made up of associated wires - transmit wires are paired with transmit wires, receive wires are paired with receive wires.

Each pair in the STP cable is then surrounded by a metallic foil shield that runs the length of the cable. Some types of STP incorporate an additional braided or foil shield that surrounds each of the shielded pairs in the cable. The overall cable is wrapped in an insulating jacket which covers the shields and holds the wires together.

9-1

Token Ring Media

Overall Shield

Tx+ Tx-

RxRx+

Outer Jacket

Pair Shield

1845n21

Figure 9-1. STP Cable Pair Association

Twisting the pairs together throughout the cable helps to reduce the effects of externally-induced electrical noise on the signals that pass through the cable. In each pair, one wire carries the normal network signal, while its associated wire carries a copy of the transmission that has been inverted.

The twisting of associated pairs helps to reduce the interference of the other strands of wire throughout the cable. This is due to the method of transmission used with twisted pair transmissions.

In any transceiver or Desktop Network Interface Card (DNI or NIC), the network protocol signals to be transmitted are in the form of changes of electrical state. The means by which the ones and zeroes of network communications are turned into these signals is called encoding. In a twisted pair environment, once a transceiver has been given an encoded signal to transmit, it copies the signal and inverts the voltage (see Figure 9-2). The result of this inverted signal is a mirror opposite of the original signal.

Both the original and the inverted signal are then transmitted, the original signal over the TX + transmit wire, the inverted signal over the TX - wire. As these wires are the same length, the signal travels at the same rate (propagates) through the cable. Since the pairs are twisted together, any outside electrical interference that affects one member of the pair will have the same effect on the other member of that pair.

The transmission travels through the cable, eventually reaching a destination transceiver. At this location, both signals are read in. The original signal is unchanged, but the signal that had previously been inverted is reverted to the original state. When this is done, it returns the encoded transmission to its original state, but reverses the polarity of any signal interference that the encoded transmission may have suffered.

9-2 Cabling Types

Token Ring Media

Original Signal

Normal

Transmission

Inverted

Transmission

Induced

Noise Spike

Reversion of Inverted

Transmission

Noise spikes

cancel out

Resulting Signal

1845n05

Figure 9-2. Twisted Pair Signal Equalization

STP cable is made up of four or more wires, and each wire within the cable has a speciﬁc insulator color. These colors are part of the IEEE speciﬁcations to which the cable construction process must be held. Each color identiﬁes a particular usage for the cable. The four standard colors are black, red, green, and orange. Table 9-1, below, identiﬁes the type of signal that each wire carries.

Table 9-1. STP Cable Wire Identiﬁcations

Type 1

Cable Color Application

Black TX -

Red RX +

Green RX -

Orange TX +

STP cabling is available in several different arrangements and construction styles, called Types. The type deﬁnitions are based on the IBM cabling system. STP cabling that may be used in Token Ring environments falls into four types, called Type 1, Type 2, Type 6, and Type 9. Any of these cable Categories can be used in a Token Ring installation, provided that the requisite IEEE 802.5 speciﬁcations regarding the cables are met.

Type 1 STP consists of two pairs of solid 22 AWG copper strands. Each strand, approximately 0.02 inch thick, is surrounded by a layer of insulation. The characteristics of the insulation is determined by the ﬁre resistance construction of the cable (plenum cable is thicker and made with slightly different material than normal PVC cabling).

Cabling Types 9-3

Token Ring Media

Type 2

The individual wires are twisted into pairs. The pairs that are formed by this twisting are then surrounded by a mylar foil shield. These shielded pairs are then laid alongside one another in an overall braided metal shield. The shield containing the twisted pairs is then surrounded by a tight outer covering. Type 1 STP is heavy and rather inﬂexible, but provides excellent resistance to interference and noise due to its construction characteristics. Type 1 STP is most commonly used as a facility cabling, while more ﬂexible cabling is used for jumper cables and patch panel connections.

IBM Type 2 cable is constructed in much the same fashion as Type 1 cable. The two central shielded pairs and the overall braided shield which surrounds them are constructed of the same materials, and then two additional pairs of AWG 22 insulated solid copper wires are laid outside the braided shield before the whole cable is surrounded by the tight outer covering. These outer wires may be used to carry telephone trafﬁc, as the shields surrounding the inner, network wires is intended to eliminate the interference that might otherwise occur between the inner and outer pairs.

Type 6

NOTE

voice and data wiring in the same cable. Degradation of network performance may result from any non-standard uses of cable.

The added pairs of wire in a Type 2 cable make it even less ﬂexible than Type 1 cable. For this reason, it is typically used as facility cable. Lighter-gauge, more ﬂexible cable types, such as Types 6 and 9, discussed below, are frequently used as patch cables between networking hardware and Type 2 cable.

Type 6 cable uses the same dual-shielded construction that Type 1 and Type 2 cable use, but the materials used in the construction are of a narrower gauge. The wires that make up the twisted pairs in a Type 6 cable are constructed of 26 AWG stranded conductors.

The construction materials used in Type 6 cabling make it a much more ﬂexible form of STP, but greatly reduce the cable’s ability to carry network signals over long distances. Type 6 cable is intended for use as jumper or patch panel cabling only.

Cabletron Systems does not recommend combining active

9-4 Cabling Types

Type 9

Type 9 cable is similar in construction to Type 6 cable, and is intended to be used for the same purposes. The center strands of a Type 9 cable are made of either solid or stranded 26 AWG conductors.

Unshielded Twisted Pair (UTP)

Unshielded Twisted Pair cabling (referred to here as UTP) is commonly made up of two or four pairs of 22, 24, or 26 AWG unshielded copper solid or stranded wires. These pairs of wires are twisted together throughout the length of the cable. These twisted pairs of wire within the UTP cable are broken up into transmit and receive pairs. The UTP cable used in network installations is the same type of cable used in the installation of telephone lines within buildings. UTP cabling is differentiated by the quality category of the cable itself, which is an indicator of the type and quality of wire used and the number of times the wires are twisted around each other per foot. The categories range from Category 1 to Category 5, with Category 5 cabling being of the highest quality.

The wires that make up a length of UTP cable are numbered and color coded. These color codes allow the installer of the networking cable to determine which wires are connected to the pins of the RJ45 ports or patch panels. The numbering of the wires in USOC standard cables is based on the color of the insulating jacket that surrounds the core of each wire.

Token Ring Media

Each jacket will have an overall color: brown, blue, orange, green, or white. In a 4-pair UTP cable (the typical UTP used in networking installations) there will be one wire each of brown, blue, green, and orange, and four wires whose overall color is white. The white wires will be distinguished from one another by periodically placed (usually within 1/2 inch of one another) rings of the other four colors.

The association of pairs of wire within the UTP cable jacket are decided by the speciﬁcations to which the cable is built. There are two main speciﬁcations in use around the world for the production of UTP cabling: EIA/TIA 568 and USOC. The two wiring standards are different from one another in the way that the wires are associated with one another throughout the cable.

The arrangement of the wires in the two speciﬁcations does not affect the usefulness of the resultant cables for Token Ring networking. The arrangement of the wires and pairs in the EIA/TIA and USOC speciﬁcations is discussed in the UTP Cable portion of the Connector Types section of this chapter.

Cabling Types 9-5

Token Ring Media

While UTP cables are usually built to provide four pairs of wire, IEEE 802.5 standards only require the use of two pairs, referred to as Pair 1 and Pair 2 (Pair 1 and Pair 3 of the EIA/TIA 568A speciﬁcation). Pair 2 of the connector is the transmit pair and Pair 1 of the connector is the receive pair. This organization of wires at the connector is referred to as a pinout. Pinouts will be discussed in greater detail in the Connector Types section of this chapter.

Table 9-2. IEEE 802.5 Wire Use

Token Ring Signal Use

Wire Color USOC Pair

568A 568B

White/Blue (W-BL)

Blue (BL) TX- RX-

White/Orange (W-OR)

Orange (OR) RX- TX-

White/Green (W-GR)

Green (GR)

White/Brown (W-BR)

Brown (BR)

Pair 1 Pins 3 and 4

Pair 2 Pins 2 and 5

Pair 3 Pins 1 and 6

Pair 4 Pins 7 and 8

TX+ RX+

RX+ TX+

Not Used

Do not split pairs in a twisted pair installation. While you may

NOTE

consider combining your voice and data cabling into one piece of horizontal facility cabling, the crosstalk and interference produced by this practice greatly reduces the viability of the cable for either application. The use of the pairs of cabling in this fashion can also prevent the future usage of advanced networking technologies that require the use of all four pairs in a twisted pair cable.

UTP cabling is produced in a number of overall quality levels, called Categories. The requirements of networking limit UTP cabling for Token Ring to Categories 3, 4, or 5. Any of these cable Categories can be used in a Token Ring installation, provided that the requisite IEEE 802.5 speciﬁcations regarding the cables are met.

9-6 Cabling Types

Category 3

Category 4

Token Ring Media

The individual wires are twisted into pairs. The twisted pairs of cable are laid together along with a thin nylon cord. This “ripcord” is useful for stripping the outer jacket of the cable, which may be low-smoke PVC plastic or a plenum-rated insulating material. The outer jacket surrounds, but does not adhere to, the wire pairs which make up the cable.

Category 3 UTP cabling must not produce an attenuation of a 16 MHz signal greater than 40 dB/305 m (1000 ft) at the control temperature of 20° C.

Category 4 UTP cabling is constructed in the same manner as the Category 3 cabling discussed previously. Category 4 UTP is constructed using copper center strands of 24 or 22 AWG. Each strand is insulated and twisted together with another strand to form a pair. The resulting wire pairs are then covered by a second layer of insulating jacketing.

Category 5

Category 4 UTP must not produce an attenuation of a 16 MHz signal greater than 27 dB/305 m (1000 ft) at the control temperature of 20° C.

Category 5 UTP cabling is manufactured in the same fashion as Category 3 cable, but the materials used are of higher quality and the wires that make up the pairs are more tightly wound.

Category 5 UTP consists of 2 or more pairs of 22 or 24 AWG wire. Category 5 cable is constructed and insulated such that the maximum attenuation of a 16 MHz signal in a cable run at the control temperature of 20° C is 0.655 dB/m (25 dB/1000 ft). A cable that has a higher maximum attenuation than 0.655 dB/m does not meet the Category 5 requirements.

Cabling Types 9-7

Token Ring Media

Fiber Optics

Fiber optic cable is a high performance media constructed of glass or plastic that uses pulses of light as a transmission method. Because ﬁber optics do not utilize electrical charges to pass data, they are free from the possibility of interference due to proximity to electrical ﬁelds. This, combined with the extremely low rate of signal degradation and dB loss makes ﬁber optics able to traverse extremely long distances. The actual maximums are dependent upon the architecture being used, but distances up to 10 km (6.2 miles) are not uncommon.

Glass optical ﬁber is made up of a glass strand, the core, which allows for the easy transmission of light, the cladding, a glass layer around the core that helps keep the light within the core, and a plastic buffer that protects the cable.

Cladding

Transmissive Core

PVC Buffer (Jacketing)

1845n07

Figure 9-3. Fiber Optic Cable Construction

There are two basic types of ﬁber optics: multimode and single mode. The names come from the types of light used in the transmission process. Multimode ﬁber uses inexpensive Light Emitting Diodes (LEDs) that produce light of a single color. Due to the nature of the LED, the light produced is made up of a number of differing wavelengths of light, ﬁred outward from the center of the LED. Not all the rays of light enter the ﬁber, and those that do often do so at an angle, which reduces the amount of distance the signal can effectively cover. Single mode ﬁber optics use lasers to achieve greater maximum distances. Since light from a laser is all of the same wavelength, and travels in a coherent ray, the resulting signal tends to be much clearer at reception than an LED signal under the same circumstances.

Fiber optics of both types are measured and identiﬁed by a variety of means. The usual means of referring to a ﬁber optic cable type is to identify if it is single mode or multimode, and to describe the thickness of each strand. Fiber optics are very thin, and the width of each strand is measured in microns (µm). Two measurements are important in ﬁber optic identiﬁcation: the diameter of the core, where signals travel, and the diameter of the cladding, which surrounds the core. Thus, ﬁber optic measurements will usually provide two numbers separated by the “/” symbol. The ﬁrst number is the diameter, in microns, of the core. The second is the diameter of the cladding. Thus, a 62.5/125 multimode cable is a type of ﬁber optic cabling with a 62.5 micron core and 125 micron cladding, which can be used by inexpensive LED equipment, as it allows multiple modes of light to pass through it. Incidentally, 62.5/125 µm multimode cabling is a very common type of ﬁber optics.

9-8 Cabling Types

Token Ring Media

Cabletron Systems recommends that customers planning to

TIP

install ﬁber optic cabling not install any facility ﬁber optics (non-jumper cabling) containing fewer than six strands of usable optical ﬁber . The minimum number of strands needed to make an end-to-end ﬁber optic link between two network devices is two. In the event that a strand within the cable is damaged during installation or additional ﬁber pairs become desired along the cable path, the availability of extra strands of optical ﬁber will reduce the likelihood that a new cable must be pulled. The existing, unused pairs of optical ﬁber can be terminated and used immediately.

Multimode

Single Mode

Multimode ﬁber optic cabling is designed and formulated to allow the propagation of many different wavelengths, or modes, of light. Multimode ﬁber optics are the most commonly encountered ﬁber type in network installations, due to their lower cost compared to other ﬁber types.

Token Ring ﬁber optic devices that meet the IEEE 802.5j speciﬁcation are terminated with ST connectors. Older network installations may utilize the IBM biconic connector or the Sub-Miniature Assembly (SMA) connector.

Single mode ﬁber optics are designed speciﬁcally to allow the transmission of a very narrow range of wavelengths within the core of the ﬁber. As the precise wavelength control required to accomplish this is performed using lasers, which direct a single, narrow ray of light, the transmissive core of single mode ﬁber optics is typically very small (8 to 12 µm). Single mode ﬁber is more expensive to produce than multimode ﬁber, and is typically used in long-haul applications.

Due to the very demanding tolerances involved in connecting two transmissive media with diameters approximately one-quarter as thick as a sheet of paper, single mode ﬁber optics require very precise connectors that will not move or shift over time. For this reason, single mode ﬁber optics should only be terminated with locking, preferably keyed, connectors. Token Ring ﬁber optic installations must use the ST connector to be compliant with the IEEE 802.5j speciﬁcation.

Cabling Types 9-9

Token Ring Media

Connector Types

STP

Medium Interface Connector (MIC)

The Medium Interface Connector is a genderless connector that is designed to be used with IBM Type 6 and Type 9 STP cabling. The MIC connector may also be used on Type 1 or Type 3 STP cabling.

The design of the MIC connector allows it to be properly and securely connected to any other Token Ring MIC connector. It is made up of a plastic outer shell and four gold-plated contacts arranged in two rows of two each, as shown in Figure 9-4.

Locking Arm

Contact Plates

1845n23

Figure 9-4. The Medium Interface Connector

The design of the MIC connector allows it to internally self-short. Spring-release mechanisms within the connector open the transmit and receive paths in the MIC connector when it is properly attached to another MIC connector. Once unplugged, the paths are looped back onto one another, allowing Token Ring signals to travel back through the cable and remain in the Token Ring network, keeping the ring whole. This helps prevent error conditions from occurring every time a station or cable is unplugged.

Attaching a MIC connector to the end of an STP cable run is relatively simple to understand, as the pins of the MIC connector are color coded in the same manner as the wires of the STP cable. To attach the connector, the individual wires of the STP cable are attached to the four pins in the arrangement shown by the color coded posts that hold the wires once the connector is assembled.

9-10 Connector Types

DB9

Token Ring Media

The DB9 connector is a smaller standard connector for IEEE 802.5 networking applications, typically used for desktop and networking hardware connections. It is used in locations where a sturdy connection to STP cabling is required, but the use of MIC connectors is either impossible or undesirable. The DB9 cabling is usable on all types of STP cabling, but is most commonly found on jumper cabling such as IBM Types 6 and 9.

The DB9 connector is a metal or composite shell with nine pins or channels at the end of the connector, arranged in two staggered rows. The pins are numbered from one to nine, beginning with the upper row of ﬁve pins or channels, that are numbered one to ﬁve, starting from the far right pin. The lower four pins are numbered from six to nine, beginning also at the far right. The arrangement of pins in the DB9 connector is shown in Figure 9-5, below.

Pin Ordering

12345

6789

1845n24

Figure 9-5. DB9 Pin Arrangement

The male DB9 connector housing, or shell, also incorporates two securing screws. These screws are used to secure the DB9 connector to a female DB9 connector and hold it in place. The screws of a DB9 connector should always be used to ensure a solid connection between two connectors, otherwise, disconnection of the cable or damage to the connectors may result.

The DB9 connector looks identical to the PC EGA monitor

NOTE

connector. If a Token Ring lobe connection is attached to the monitor port, the Token Ring network will enter an error state. This is due to the resemblance that EGA monitor current has to the phantom current required to open a Token Ring lobe connection.

Connector Types 9-11

Token Ring Media

The DB9 connector does not perform a wrap on disconnect as does the larger MIC connector. There is no internal mechanism for performing these operations. Stations connected to networking hardware with DB9 connectors rely on the networking hub to perform any wrapping in the event of a disconnection or cable error.

STP wires that are connected to a DB9 cable must be set up in the fashion detailed below:

Table 9-3. IEEE 802.5 DB9 Pinouts

RJ45

STP Wire

Color

IEEE 802.5

Signal

DB9 Pinout

Black TX - 1

Green RX - 5

Orange TX + 6

Red RX + 9

The shielded RJ45 connector used with STP cable is identical in shape to the standard RJ45 connector used in other network applications such as Ethernet and FDDI TP-PMD. The difference between the shielded RJ45 and the standard RJ45 is the addition of a metal shielding ground to the plastic housing of the RJ45 connector. This shield is connected to the braided outermost shield of the STP cable.

The connector itself is a rectangular keyed connector with a locking clip. The RJ45 connector can only be inserted into an RJ45 port in its proper alignment, and, when inserted, will lock into place. Due to the lighter construction characteristics of the RJ45 connector in comparison with the other STP cable connectors, care should be taken to ensure that the strain placed on an RJ45 connection is minimized through proper use of cable management hardware.

9-12 Connector Types

Plastic Hood

Token Ring Media

Contact Blades

Metal Shielding

Locking Clip

1845n25

Figure 9-6. The Shielded RJ45 Connector

The shielded RJ45 cable is made up of the plastic and metal outer housing and locking clip. Within the housing, a series of contact blades are lined up next to one another to provide contact points for the pins of the RJ45 port. The contact blades themselves are square-shaped, ﬂat on three sides and with a set of two or three triangular teeth on one side. The teeth of the connector are at the bottom of the blades to pierce the individual wires of the STP cable when the connector is crimped shut.

Shielded RJ45 connectors are available in conﬁgurations designed to attach to either solid core or stranded core STP wires. Be sure when selecting cabling and connectors that the RJ45 connector chosen is correct for the type of cabling to be used. The blades of the RJ45 connector (shown in Figure 9-8) end in a series of points that pierce the jacket of the wires and make the connection to the core. Different types of connections are required for each type of core composition. These connectors are differentiated by the arrangement of the teeth of the contact blades.

An STP cable that uses solid core wires requires the use of contact blades with three teeth. This is due to the inability of the teeth to effectively penetrate the solid core of the STP wire without damaging the cable. The three teeth are placed in a staggered left-right-left orientation that pierces the insulator of the STP wire and wedges the core between the teeth, making an electrical contact at three points.

A cable that uses stranded core wires will allow the contact points to nest among the individual strands. The contact blades in a stranded RJ45 connector, therefore, are laid out with their contact points in a straight line. The contact points cut through the insulating material of the jacket and make contact with several strands of the core.

Connector Types 9-13

Token Ring Media

The wires of the STP cable must be organized in the RJ45 connector properly, based upon the USOC speciﬁcation and the IEEE 802.5 speciﬁcation. This organization of the wires at the connector is known as a pinout. The proper pinout for the Token Ring shielded RJ45 connector is given in Table 9-4, below. In addition to arranging the cables properly, the braided shield of the STP cable must be connected to the metal shield of the RJ45 connector.

The USOC speciﬁcation orders the pairs in a four-pair cable into the pinout shown in Figure 9-7, below. The RJ45 connector in the ﬁgure is being viewed from the contact blade end, with the locking clip up. The contact blades of the RJ45 connector are numbered one through eight from left to right for purposes of identiﬁcation.

Pair 2 Pair 1

BK RE GR OR

Pair 3 Pair 4

1845n22

Figure 9-7. USOC Pair Organization - STP

Table 9-4. IEEE 802.5 RJ45 Pinouts for STP

Wire Color

IEEE 802.5

Signal

RJ45 Pinout

Black TX - 3

Red RX + 4

Green RX - 5

Orange TX + 6

9-14 Connector Types

Cabletron Systems 100BASE-FX Cabling Manual

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Frequently Asked Questions

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