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Chapter 25: Multicast

STANDARD Revision 1.0 C4® CMTS Release 8.3 User Guide

IGMP Implementation

IGMP is an Internet protocol (IP) for managing multicast groups on the Internet and for the IP Video feature. For an

overview of standards related to IGMP, see RFCs 2236, 2933, 3376, 4601, 4607, and 5790.

The C4/c CMTS supports IGMP version 2 for host and router functionality and IGMP version 3 for router functionality.

DOCSIS

Compliance for IGMP

The DOCSIS® Specifications (SP-RFIv2.0-106-040804 and SP-OSSIv3.0-I12-100611) describe IGMP DOCSIS® 3.0

requirements as either Passive or Active operation modes.

IGMP Terminology

The following definitions support the IGMP terminology:

IGMP Proxy Interface — forwards (proxies) IGMP membership reports on behalf of another interface when using an IGMP

proxy configuration. Typically, this is an C4/c CMTS network interface that proxies IGMP membership reports received

from a cable interface.

IGMP Host — sends the IGMP membership reports to request multicast data from an IGMP router, for example, the

ingress interface of the multicast data. The host function is configured on each C4/c CMTS interface by default and

operates in IGMP version 2 mode.

IGMP Router — provides the IGMP query function that is used to track IGMP group membership. The IGMP router must be

configured on those interfaces where IGMP group membership is expected to be the destination interface for the

forwarding of multicast data. The IGMP router operates in IGMPv2 mode by default once configured.

Note: IGMPv3 must be used in an MDF-enabled mac-domain for IGMP query signaling.

Source-Specific Multicast

The Source-Specific Multicast (SSM) service defines the capability to request multicast traffic from a single source. To

support this one-to-many model, two protocol standards have been defined: IGMPv3 and PIM-SSM. (PIM is Protocol

Arris C4C User Manual

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