Specifications

DOCSIS 1.1 for Cisco uBR905 and Cisco uBR925 Cable Access Routers and Cisco CVA122 Cable Voice Adapters

Information About DOCSIS 1.1 Support

Cisco IOS Release 12.2(15)CZ

• You must load at least one CVC into the cable modem through the DOCSIS configuration file. The

cable modem uses the CVC to verify that a downloaded software image is from the proper

manufacturer and has not been altered during transmission. You can load two types of CVCs into

the cable modem:

–

Manufacturer’s CVC (M-CVC)—Verifies that the downloaded software image has been

digitally signed by the manufacturer (Cisco Systems). The M-CVC is loaded into the cable

modem by specifying TLV 32 (MFG CVC) in the DOCSIS configuration file.

–

Cosigner’s CVC (C-CVC)—Verifies that the downloaded software image has been digitally

signed by both the manufacturer (Cisco Systems) and the cable operator. The C-CVC is loaded

into the cable modem by specifying TLV 33 (MSO CVC) in the DOCSIS configuration file.

If you load the M-CVC into the cable modem, you can download only those software images that

Cisco Systems has digitally signed. If you load the C-CVC into the cable modem, you can download

only those software images that Cisco Systems and the cable operator have digitally signed.

Note A DOCSIS 1.1 cable modem must use the secure software download feature when upgrading its software

image through the DOCSIS configuration file or through SNMP commands. However, users can still use

CLI commands to copy an unsigned software image from a TFTP server, if they know the enable

password and are allowed console or Telnet access.

After the cable modem loads and runs the DOCSIS 1.1 image, the cable modem must use the secure

software download process for all future upgrades. In particular, this means that the cable modem cannot

be downgraded to a DOCSIS 1.0 software image unless the manufacturer provides a digitally signed

DOCSIS 1.0 image. After downgrading to a DOCSIS 1.0 image, you cannot use the secure software

download process again until you have upgraded the cable modem to a new DOCSIS 1.1 image.

Tip Cisco IOS software images that include “cvc” as part of the software image filename

(ubr925cvc-k9o3sv9y5-mz) are digitally signed. Unsigned software images do not have “cvc” as part of

the filename (ubr925-k9o3sv9y5-mz). If you are using secure software download, you must use a

digitally signed image (includes “cvc”). If you are not using secure software download, you must use an

unsigned image (does not include “cvc”).

DOCSIS 1.1 Quality-of-Service

DOCSIS 1.1 implemented a number of changes to allow great flexibility in the ability of a cable modem

and service provider to transmit almost any combination of data traffic and real-time traffic, such as

voice and video. These changes required a fundamental shift in how a cable modem requests service and

how traffic can be transmitted across the cable network.

Overview

The DOCSIS 1.1 QoS framework is based on the following objects:

• Service class—A collection of settings maintained by the CMTS that provide a specific QoS service

tier to a cable modem that has been assigned a service flow within a particular service class.

• Service flow—A MAC-layer transport service that provides unidirectional transport of packets to

upstream packets transmitted by the cable modem or to downstream packets transmitted by the

CMTS. A service flow is characterized by a set of QoS parameters such as latency, jitter, and

throughput assurances.