Multicast information policies on the 7750 SR and 7450 ESS serve multiple purposes. In the context of a service with video services, the multicast information policy assigned to the service provides configuration information for the multicast channels and defines video policy elements for a video interface.
This section describes the base elements of a multicast information policy in support of a video service. Specific video service features require additional configuration in the multicast information policy which are described in the sections dedicated to the video feature.
Multicast information policies are named hierarchically structured policies composed of channel bundles which contain channels which contain source-overrides.
Bundles are assigned a name and contain a collection of channels. Attributes not defined for a named bundle are inherited from the special default bundle named ‟default”.
*A:ALA-48configmcast-mgmtmcast-info-plcy# info
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bundle "default" create
exit
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*A:ALA-48configmcast-mgmtmcast-info-plcy#
Channels are ranges of IP multicast address identified by a start IP multicast address (GGstart) and optional end IP multicast address (Gend), so the channels encompasses (*,Gstart) through (*,Gend). A channel attribute is inherited from its bundle unless the attribute is explicitly assigned in which case the channel attribute takes precedence.
A source-override within a channel are IP multicast addresses within the channel with a specific source IP address (Soverride), so the source-override encompass (Soverride,Gstart) through (Soverride,Gend). A source-override attribute is inherited from its channel unless the attribute is explicitly assigned in the source-override channel in which case the source-override channel attribute takes precedence.
For a IP multicast channel (*,G) or (S,G), the most specific policy element in the hierarchy that matches applies to that channel.
A multicast information policy is assigned to a service instance. For video services, the multicast information policy assigned to the service determines the video group for a given IP multicast channel. When a channel is assigned to a video group, the channel is sent to the video group for buffering or processing as appropriate depending on the video services enabled on the video group. If no video group is assigned to a channel, the channel is still distributed within the service instance, but no video services are available for that channel.
In addition to bundles, channels and source-overrides, multicast information policies also include video policies. Video policies define attributes for the video interfaces within the service instance.
Video policy attributes are specific to the video feature and are covered in detail in the applicable video feature section. Video policies are mentioned here because they are an element of the multicast information policy and provide the link to configuration for a video interface.