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

• Ability to provide separate downstream rates for any given cable modem, based on the

IP-precedence value in the packet. This helps separate voice signaling and data traffic that goes to

the same ITCM to address rate shaping purposes.

• Concatenation allows a cable modem to send several packets in one large burst, instead of having to

make a separate grant request for each.

Caution All DOCSIS 1.0 extensions are available only when using a cable modem (such as the Cisco uBR924

cable access router) and CMTS (such as the Cisco uBR7200 series universal broadband router) that

supports these extensions. The cable modem activates the use of the extensions by sending a dynamic

MAC message. DOCSIS 1.0 cable modems continue to receive DOCSIS 1.0 treatment from the CMTS.

SNMPv3 Support

DOCSIS 1.1 also requires support of v3 of the Simple Network Management Protocol (SNMPv3).

SNMPv3 offers a number of significant improvements over SNMPv1 and SNMPv2:

• DES 56-bit encryption that encrypts each packet to prevent interception or alteration intransit.

SNMP attributes can be set and retrieved without exposing confidential information on a public

network.

• Authentication based on the HMAC-MD5 or HMAC-SHA algorithms that ensures that each packet

is from a valid source.

• An improved security model that provides for a larger number of security levels, with a greater

granularity in determining per-user access. Each SNMPv3 user belongs to a group, which defines

the security model and security level for its users. This includes the level of access to SNMP objects

and the list of notifications that users can receive.

SNMPv3 Diffie-Hellman Kickstart

To ensure SNMPv3 security, the Multi-Service Operator (MSO) must perform an initialization

procedure the first time the cable modem comes online. This procedure, which the DOCSIS 1.1

specification refers to as the SNMPv3 Diffie-Hellman Kickstart, sends a public key to the cable modem

as part of the DOCSIS configuration file. The cable modem creates a secret number and encrypts it using

the public key it received in the configuration file.

The cable modem then publishes the encrypted number to the CMTS, which uses its private key to

decrypt it so as to produce the cable modem’s secret number. This secret number becomes a shared secret

value that the CMTS and CM can use to exchange SNMPv3 encryption keys.

For information on the SNMPv3 Diffie-Hellman Kickstart configuration, see the “Configuring the

SNMPv3 Diffie-Hellman Kickstart Public Key” section on page 22.

MIB Enhancements

DOCSIS 1.1 also expands the MIB support for SNMP management, including the following changes and

additions to the DOCSIS 1.0 MIB structure:

• DOCS-BPI-PLUS-MIB—Describes the Baseline Privacy Interface Plus (BPI+) attributes and

replaces the DOCS-BPI-MIB, which was used in DOCSIS 1.0. This is revision 05 of the MIB.

• DOCS-QOS-MIB—Describes the quality-of-service (QoS) attributes. This is revision 04 of the

MIB.