Cisco Systems UBR900 User Manual
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Configuring the Cisco uBR900 Series

Cable Access Routers

This document addresses the following topics:

Feature Overview on page 1

Supported Platforms on page 32

Prerequisites on page 32

Supported MIBs and RFCs on page 33

Configuration Tasks on page 36

Configuration Examples on page 46

VoIP Bridging Configuration Using SGCP on page 52

Debug Commands on page 118

Glossary on page 135

Feature Overview

Cisco uBR900 series cable access routers are fully-functionalCisco IOS routers andstandards-basedbidirectional cable modems that give a residential or small office/home office (SOHO) subscriberhigh-speedInternet or Intranet access and packet telephone services via a sharedtwo-waycable system and IP backbone network. Cisco uBR900 series cable access routers are based on the currentData-Over-CableService Interface Specifications (DOCSIS) standards, and interoperate with any bidirectional,DOCSIS-qualifiedheadend cable modem termination system (CMTS).

Cisco uBR900 series routers connect computers, telephone equipment, and other customer premises devices at a subscriber site to the service provider’s Hybrid/Fiber Coax (HFC) and IP backbone network. Functioning as cable modems, the Cisco uBR900 series routers transport data and voice traffic on the same cable system that delivers broadcast TV signals.

Cisco uBR900 series cable access routers typically ship from the Cisco factory with a Cisco Internetwork Operating System (IOS) software image stored in nonvolatile memory (NVRAM). The standard Cisco IOS software image supports DOCSIS-compliantbridging operation for data as the default.

Based on the feature licenses purchased, other Cisco IOS images can be downloaded from Cisco Connection Online (CCO). Each Cisco uBR900 series router in your network can then be configured to support Voice over IP (VoIP) and/or other special operating modes based on your service offering and the practices in place for your network. A Cisco uBR900 series device can function as an advanced router, providing wide area network (WAN) data connectivity in a variety of configurations.

Configuring the Cisco uBR900 Series Cable Access Routers 1

Feature Overview

Cisco IOS Software Feature Sets

This section briefly describes the common feature sets supported by the Cisco uBR900 series cable access routers. Each feature set contains a number of features that provide a specific functionality such as Voice over IP (VoIP) or virtual private network (VPN) access.

The following feature set categories are currently available:

Data Operations

Data and Voice Operations

The data and voice feature sets add Voice over IP (VoIP) support to the same base features contained in the data only feature sets. Telephones that are connected to the uBR924 cable access router can make voice calls over the Internet using either the H.323 (Gateway/Gatekeeper) voice control protocol or Simple Gateway Control Protocol (SGCP). (For more information on these protocols, refer to H.323 Protocol Stack andSGCP Protocol Stack in this document.)

Because voice calls are real-timetraffic, the Cisco uBR924 cable access router supports the DOCSIS Quality of Service (QoS) enhancements to give higher priority to IP packets containing voice traffic.

Note Voice features are available only on the Cisco uBR924 cable access router.

Note Feature sets and software images vary depending on the cable access router model you are using and the Cisco IOS software release that is running. For a list of the available software images for your application, and the specific features contained in each image, refer to the release notes for the Cisco uBR900 series cable access router and Cisco IOS software release you are using. This document describes the features available for the Cisco uBR904 and uBR924 cable access routers in Cisco IOS Release 12.0(7)T.

The following feature sets are available in data and voice versions as well as in data only versions:

Base IP Bridging – provides full DOCSIS1.0-compliantcable modem support for users who want a basichigh-speedconnection to the Internet.

Home Office (Easy IP) – provides ahigh-speedconnection to the Internet, along with server functions that simplify the administration of IP addresses, so that the Cisco uBR900 series cable access router can connect a small number of computers to the Internet through the cable interface.

Small Office – provides a firewall feature set in addition to thehigh-speedInternet connection and server functions provided by the Home Office feature set. You can protect your office network from intrusion and interference while still havinghigh-speedaccess to the Internet.

Telecommuter – provides encryption and layer 2 tunneling support in addition to thehigh-speedInternet connection and server functions provided by the Home Office feature set. Businesses can establish securehigh-speedInternet connections between employees’ homes and the office local network.

These feature sets are described in the following sections.

2 Cisco IOS Release 12.0(7)T

Cisco IOS Software Feature Sets

Base IP Bridging

Base IP Bridging includes full and DOCSIS-compliantbridging andDOCSIS Baseline Privacy. The Base IP Bridging feature set allows the Cisco uBR900 series cable access router to function as a DOCSIS 1.0 cable modem and to interoperate with any DOCSIS1.0-qualifiedCMTS. It provides basichigh-speedInternet connectivity for users who want to connect only one computer to the cable network.

DOCSIS-compliantbridging (also referred to as“plug-and-play”bridging) is the default configuration for Cisco uBR900 series cable access routers. While inplug-and-playbridging mode, the router locates a downstream and upstream channel; finds ToD, TFTP, and DHCP servers; obtains an IP address; downloads a DOCSIS configuration file; and obtains DHCP parameters to work in bridging mode.

Note This feature set does not include Easy IP and Routing.

In DOCSIS-compliantbridging mode, the Cisco uBR900 series cable access router acts as a transparent bridge for the following device combinations:

3 CPE devices when using Cisco IOS Release 12.0(4) XI1 or higher

254 CPE devices when using Cisco IOS Release 12.0(5)T or higher images, or Cisco IOS Release 12.1.

Note The ability of the Cisco uBR900 series cable access router to grant access to CPE devices is controlled by the MAX CPE field in the DOCSIS configuration file. The MAX CPE field defaults to one CPE device unless otherwise set to a higher number.

Home Office (Easy IP)

The Home Office feature set provides high-speedInternet connectivity for customers who have a small home network (typically2-4computers). In addition to full DOCSIS 1.0 support and all of the functionality of theBase IP Bridging feature set, the Home Office feature set (also known as Easy IP) supports intelligent Dynamic Host Configuration Protocol (DHCP) server functions, including DHCP Relay Agent and DHCP Client functionality. It also supportsEasy IP (NAT/PAT).

This feature set allows the Cisco uBR900 series cable access router great flexibility in administering IP addresses for the PCs and other customer premises equipment it is connecting to the cable network. The DHCP functionality allows intelligent use of the IP addresses that allow customer premises computers and other equipment to connect to the Internet. The NAT/PAT functionality allows you to use private IP addresses on the local network, while still maintaining connectivity to the Internet.

Small Office

In addition to full DOCSIS 1.0 support and all of the functionality of the Easy IP feature set, the Small Office feature set supports the Cisco IOS firewall feature set which provides a wide range of security features for Cisco uBR900 series cable access routers. Using the firewall feature set, Cisco uBR900 series cable access routers act as buffers between the customer’s private enterprise network and the Internet and other connected public networks.

Configuring the Cisco uBR900 Series Cable Access Routers 3

Feature Overview

In firewall mode, the Cisco uBR900 series cable access router provides a high-speedInternet connection for an office’s local network while protecting the computers on the office network from common attacks such as denial of service attacks and destructive Java applets, as well asreal-timealerts of such attacks.

The Small Office feature set can be optionally extended with support for IPSec encryption to ensure that the traffic passed over the Internet cannot be intercepted. You can select either standard 56-bitIPSec Network Security encryption orhigh-security168-bitTriple Data Encryption Standard (DES) encryption.

Telecommuter

In addition to full DOCSIS 1.0 support and all of the functionality of the Easy IP feature set, the Telecommuter feature set supports IPSec encryption and the Layer 2 Tunneling Protocol (L2TP), which can establish secure high-speedInternet connections between employees’ homes and the office local network.

IPSec is an IP security feature that provides robust authentications and encryption of IP packets for the secure transmission of sensitive information over unprotected networks such as the Internet. You can select either standard 56-bitIPSec Network Security encryption orhigh-security168-bitTriple Data Encryption Standard (DES) encryption.

L2TP is an extension of the Point-to-PointProtocol (PPP) that allows computers on different physical networks to interoperate as if they were on the same local area network (LAN). These features are important components for Virtual Private Networks (VPNs).

Note The Telecommuter feature set does not require the firewall feature set because the individual telecommuter has a secure connection to the office network. The office network, however, should implement a firewall for its own connection to the Internet.

Data Operations

Figure 1 illustrates a typical broadband data cable system. Data transmitted to a Cisco uBR900 series cable access router from the service provider’s CMTS shares a 27 or 26 Mbps, 6 MHz data channel in the 88 to 860 MHz range. The Cisco uBR900 series cable access router shares an upstream data rate of up to 10 Mbps on a 200kHz-wideto 3.2MHz-widechannel in the 5 to 42 MHz range.

Note End-to-endthroughput varies based on the design and loading of network components, the mix of traffic, the processing speed and interface of the host server(s), the processing speed and local Ethernet performance of the subscriber’s computer, as well as other parameters. Since the network can be configured to support multiple levels of service to meet differing market price/performance requirements, the subscriber’s service level agreement also affects throughput. DOCSIS further contains some fundamental performance limitations because standards are designed to give a larger number of customers good performance, rather than permitting a few users to consume the entire capacity.

4 Cisco IOS Release 12.0(7)T

Data Operations

Figure 1 Typical Cisco Broadband Data Cable System

WAN

 

 

 

 

 

CMTS

 

Combiner

 

Tx

 

 

 

 

 

Switch/router

 

 

rack equipment

 

 

 

Rx

 

Fiber

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Servers

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Cisco uBR900 series cable access router

Internal backbone and

worldwide internet

HFC cable plant

Cable System Headend

Upstream and downstream data interfaces Operation support system interface Downstream RF interface

Upstream RF interface

18197

Residence or SOHO subscriber site: subscriber RF interface Ethernet interface

Operating Modes

The broadband data cable system uses multiple types of access control to ensure efficient use of bandwidth over a wide range of loading conditions. Advanced queuing techniques and service algorithms are used to define the acquisition and release of channels.

Cisco uBR900 series cable access routers support 64 or 256 Quadrature Amplitude Modulation (QAM) downstream, and Quadrature Phase Shift Keying (QPSK) or 16 QAM upstream transmission. This allows the CMTS system administrator to set the preferred modulation scheme based on the quality of the cable plant.

Note In noisy plant environments, 16 QAM upstream and 256 QAM downstream modulation may not be viable. Inhigh-qualityHFC networks capable of supporting 16 QAM formats in the upstream direction, Cisco recommends using QPSK forfixed-slotshort packets like maintenance or data requests, and 16 QAM for variable length data packets. This results in the most efficient use of the available upstream timeslots or minislots.

The system uses Transmission Control Protocol/Internet Protocol (TCP/IP) to transmit data. TCP/IP transmits data in segments encased in IP datagrams, along with checksums to detect data corruption and sequence numbers to ensure an ordered byte stream on the TCP connection between the Cisco cable access router and the CMTS.

Cisco cable access routers also support multicast services—datastreams sent to groups of subscribers. These applications utilize the User Datagram Protocol (UDP) instead of TCP. Since UDP does not mandate upstream acknowledgments, these applications can be very efficient in the network. Additionally, restricting upstream throughput will have no effect on downstream UDP streaming throughput.

Configuring the Cisco uBR900 Series Cable Access Routers 5

Feature Overview

Note Interactive games are the exception. Although low latency is required in gaming applications, high upstream data throughput is not demanded since the volume of data transmitted upstream is typically small.

Data Specifications

Table 1

Cisco uBR900 Series Cable Access Router Data Specifications

 

 

 

Description

Downstream Values

Upstream Values

 

 

 

Frequency Range

88 to 860 MHz

5 to 42 MHz

 

 

 

Modulation

64 QAM

QPSK

 

256 QAM

16 QAM

 

 

 

Data Rate

30 Mbps/64 QAM

QPSK—320Kbit/sec to 5 Mbit/sec

 

(27 Mbit/sec after FEC overhead)

 

 

42.8 Mbps/256 QAM

16 QAM—640Kbit/sec to 10 Mbit/sec

 

(36 Mbit/sec after FEC overhead)

 

 

 

 

Bandwidth

6 MHz

200K, 400K, 800K, 1.6M,

 

 

3.2 MHz

 

 

 

FEC

RS (122, 128) Trellis

Reed Solomon

 

 

 

One Channel

Receive level of digital signal

QPSK— +8 to +58 dBmV

 

-15to +15 dBmV

 

Note Most field measurements are of nearby

16 QAM— +8 to +55 dBmV

 

or adjacent analog signal which is normally

 

+6 to +10 dB (system specific) above the

 

digital signal level

 

Signal-to-NoiseRatio

64 QAM:

(SNR)

>23.5 dB @ BER<10^8

 

256 QAM*:

 

>30 dB @ BER <10^-8

 

(For input level between +15 and -8dBmV,

 

SNR must be greater than 30 dB. For input

 

level between -8and-15dBmV, SNR must be

 

greater than 33 dB.)

 

Note These performance numbers are in

 

laboratory-controlledconditions against

 

statistically pure noise sources (AWGN). Since

 

such conditions do not exist in practise, a 6 dB

 

or more SNR margin is required for reliable

 

operation. Check with your local system

 

guidelines.

QPSK:

>15 dB @ BER<10^-8

(QPSK will work at 98% successful ping rate for SNR>13 dB. A SNR of 15 dB will be needed to get almost optimal packets per minute transition.)

16 QAM:

>22 dB @ BER <10^-8

(For 16 QAM, a SNR>22 dB makes the grade for 98% ping efficiency. To get good packet rate, you need

SNR>25 dB)

Note These measurements were made for 0 and-10dBmV input to the CMTS, 1280 ksym/sec and 64 bytes packet size with a Cisco uBR904 cable access router andlaboratory-controlledconditions.

6 Cisco IOS Release 12.0(7)T