Multicast CAC policies

Overview

Multicast CAC policies control the bandwidth consumed by BTV distribution services. Bandwidth control helps manage network congestion and maintain QoS standards. The multicast CAC function is supported on IGMP, PIM, or MLD interfaces, IGMP or MLD group interfaces, and in the case of BTV distribution, on VPLS SAPs and SDPs where IGMP snooping is enabled.

A multicast CAC policy manages the bandwidth consumed by BTV services on both the access node link and specific links in the aggregation network. Routers in the path are configured to maintain certain limits on broadcast bandwidth and can limit the number of channels simultaneously sent on both the second mile link and the network link.

The total bandwidth usage of an IGMP host is calculated using the following logic:

1. Retrieve all channels (i.e. groups) from the IGMP host.

2. For each channel (i.e group), find the corresponding MCAC policy channel object defined with a matching source address.

   The logic functions on the best match for the channel with the source address and prefix in the MCAC policy channel object. If the match fails, bandwidth is calculated from a matched MCAC channel object with a default (null) source address.

3. Retrieve the bandwidth assigned to each of the corresponding MCAC channels.

4. The sum of all bandwidth values is the total bandwidth usage of the host.