ADTRAN 4200659L2 User Manual
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Chapter 1 Introduction


The MX2800 STS-1is a SONET multiplexer that consolidates T1 and E1 signals into anSTS-1signal. This unit provides a costeffective, versatile tool for combining independent T1s or E1s over the sameSTS-1carrier.

Embedded SNMP (simple network management protocol) and Telnet are available through the modem port using SLIP/PPP or through the 10BaseT ethernet port. Using the Management Information Base II (MIB II), RFC 1595 standards, and an ADTRAN enterprise MIB, the MX2800 STS-1can be configured, monitored, and diagnosed with standard SNMP network management programs such as Hewlett Packard’s HP OpenView™ and Cabletron’s Spectrum™. In addition, the SysLog Host Daemon allows remote monitoring, collecting, and logging of MX2800STS-1events in real time. This information can be useful during installation setups and/or troubleshooting.

Complete configuration, diagnostics, and performance monitoring are available through SNMP, Telnet, or a VT-100terminal interface. This connection can be made via ethernet, a local EIA232 link, or through thebuilt-inV.34 modem (see the note at the end of this section onpage 1-2).The modem candial-outa “cry for help” for units located in unmanned facilities. The MX2800STS-1is designed for either desktop use or for installation in a19-inchor23-inchrack.


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Chapter 1. Introduction

The major features of the MX2800 STS-1are as follows:

Built-in1:1 redundancy

Hot-swappablecontroller cards

Independent, dual-loadsharing, redundant power supplies

Embedded SNMP and Telnet management through 10BaseT ethernet or SLIP/PPP dialup

Detailed performance monitoring for local and remote units

Simplified configuration through the VT-100terminal menu structure

Integrated V.34 modem for dial-upanddial-outaccess (see the following note)

Capable of backhauling multiple service types (T1/E1)

AC or DC power

VT Hairpining

VT cross-connectto any DS1

NEBS Level 3 compliant

Standard 10-yearwarranty

Information regarding the built-inmodem applies to the following list of part numbers: 4200659L1, L2, L3, and L4.

Controller Card 1:1 Redundancy

The MX2800 STS-1supports twohot-swappablecontroller cards which provide 1:1 redundancy for the T1 andSTS-1signals as well as theSTS-1connections. With two cards installed, the MX2800STS-1can recover from circuit or network failure, depending on the configuration. SeeChapter 7, Circuit and Network Redundancy for more information.


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Chapter 1. Introduction


The MX2800 STS-1multiplexer delivers up to 28 T1s or 21 E1s via the SONET Synchronous Transport Signal Level One(STS-1)at a speed of 51.84 Mbps. This is acost-effectiveway to provide T1/E1 signals without the need for costly and complexmulti-levelmultiplexing/demultiplexing as in an M13 multiplexer. The T1/E1 signals can be directly multiplexed into the SONETSTS-1signal, allowing simplified add and drop functionality.

The MX2800 STS-1multiplexer also implements VT hairpining and VTcross-connectmapping. Any VT can be hairpinned back to theSTS-1signal for dropping further down the SONET ring.Cross-connectmapping permits a VT to be mapped to any of the 28 available physical ports.


The STS-1frame is organized as 9 rows by 90 columns of bytes. This frame is transmitted row by row, from left to right, and with the most significant bit (MSB) of each byte transmitted first. It is defined to operate at the basic rate of 8 kHz or 125 microseconds per frame, or 8,000 frames per second at a bit rate of 51.84 Mbps.

The frame is divided into two parts to physically segregate the layers. The first 3 columns make up the transport overhead (TOH); the remainder is the synchronous payload envelope (SPE). The TOH has 3 rows for the section overhead (SOH) and 6 rows for the line overhead (LOH). The SPE has one column for the path overhead (POH). The remaining 86 columns are for payload data (49.536 Mbps).


There are several mechanisms that allow for timing compensation between the STS-1and its low speed tributaries. The MX2800STS-1multiplexer uses pointer adjustments to achieve timing


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Chapter 1. Introduction

compensation. Pointer adjustments allow the synchronous payload envelope (SPE) to float with respect to the SONET frame. The pointer is contained in the H1 and H2 bytes of the line overhead (LOH), and is a count of the number of bytes the J1 byte is away from the H3 byte, not including the transport overhead. When timing differences exist, dummy bytes are inserted into the SPE without affecting data. The receiving end can recover the payload since the pointer is adjusted to indicate where the payload overhead (POH) starts.

Transport Overhead (TOH)

The first three columns are the TOH, which contains the overhead bytes for the Section and Line layers. Section overhead is comprised of 9 bytes and Line overhead is comprised of 18 bytes.

STS-1Synchronous Payload Envelope (SPE)

The SPE has 87 columns and 9 rows of bytes for a total of 783 bytes. Column 1 contains the STS Path Overhead and has 9 bytes. The remaining 774 bytes are available for payload.

Virtual Tributaries (VT)

The SPE is divided into seven virtual tributary groups, made up of 12 columns each. Smaller tributaries are multiplexed together to form these groups. For example, there can be four VT1.5 tributaries in a VT group or three VT2 tributaries. A VT1.5 tributary consists of three columns per STS-1frame and has a bit rate of 1.728 Mbps, allowing transport of a T1 at 1.544 Mbps plus required overhead. A VT2 uses four columns perSTS-1frame and has a bit rate of 2.304 Mbps, allowing transport of an E1 at 2.048 Mbps plus required overhead.


MX2800 STS-1User Manual