Cisco Systems A9014CFD PIM Source Specific Multicast, Source Specific Multicast Mapping for IPv6

Chapter 42 IPv6 Multicast

Feature Overview

PIM Source Specific Multicast

PIM SSM is the routing protocol that supports the implementation of SSM and is derived from PIM SM. However, unlike PIM SM where data from all multicast sources are sent when there is a PIM join, the SSM feature forwards datagram traffic to receivers from only those multicast sources that the receivers have explicitly joined, thus optimizing bandwidth utilization and denying unwanted Internet broadcast traffic. Further, instead of the use of RP and shared trees, SSM uses information found on source addresses for a multicast group. This information is provided by receivers through the source addresses relayed to the last-hop devices by MLD membership reports, resulting in shortest-path trees directly to the sources.

In SSM, delivery of datagrams is based on the (S, G) channels. Traffic for one (S, G) channel consists of datagrams with an IPv6 unicast source address S and the multicast group address G as the IPv6 destination address. Systems receive this traffic by becoming members of the (S, G) channel. Signaling is not required, but receivers must subscribe or unsubscribe to (S, G) channels to receive or not receive traffic from specific sources.

MLD version 2 is required for SSM to operate. MLD allows the host to provide source information. Before SSM runs with MLD, SSM must be supported in the Cisco IPv6 device, the host where the application is running, and the application itself.

For more information on PIM Source-Specific Multicast, see the IP Multicast: PIM Configuration Guide at: http://www.cisco.com/en/US/docs/ios-xml/ios/ipmulti_pim/configuration/xe-3s/ip6-mcast-pim-ssm.ht ml

Source Specific Multicast Mapping for IPv6

SSM mapping for IPv6 supports both static and dynamic Domain Name System (DNS) mapping for MLD version 1 receivers. This feature allows deployment of IPv6 SSM with hosts that are incapable of providing MLD version 2 support in their TCP/IP host stack and their IP multicast receiving application.

SSM mapping allows the device to look up the source of a multicast MLD version 1 report either in the running configuration of the device or from a DNS server. The device can then initiate an (S, G) join toward the source.

For more information on IPv6 Source Specific Multicast Mapping, see the IP Multicast: PIM Configuration Guide at: http://www.cisco.com/en/US/docs/ios-xml/ios/ipmulti_pim/configuration/xe-3s/ip6-mcast-ssm-map.ht ml

PIM-Sparse Mode

PIM-SM uses a pull model to deliver multicast traffic. Only network segments with active receivers that have explicitly requested the data receive the traffic.

PIM-SM distributes information about active sources by forwarding data packets on the shared tree. Because PIM-SM uses shared trees (at least, initially), it requires the use of a rendezvous point (RP). The RP must be administratively configured in the network.

For more information on PIM Sparse Mode, see the IP Multicast: PIM Configuration Guide at: http://www.cisco.com/en/US/docs/ios-xml/ios/ipmulti_pim/configuration/xe-3s/ip6-mcast-pim-sm.htm l

	Cisco ASR 901 Series Aggregation Services Router Software Configuration Guide
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