Implementing IPv6 Multicast Information About Implementing IPv6 Multicast Routing, on page 1 How to Implement IPv6 Multicast, on page 9 Additional References, on page 31 Feature History for IPv6 Multicast, on page 32 Information About Implementing IPv6 Multicast Routing This chapter describes how to implement IPv6 multicast routing on the switch. Traditional IP communication allows a host to send packets to a single host (unicast transmission) or to all hosts (broadcast transmission). IPv6 multicast provides a third scheme, allowing a host to send a single data stream to a subset of all hosts (group transmission) simultaneously.
IPv6 Multicast Overview An IPv6 multicast group is an arbitrary group of receivers that want to receive a particular data stream. This group has no physical or geographical boundaries--receivers can be located anywhere on the Internet or in any private network. Receivers that are interested in receiving data flowing to a particular group must join the group by signaling their local switch. This signaling is achieved with the MLD protocol. Switches use the MLD protocol to learn whether members of a group are present on their directly attached subnets. Hosts join multicast groups by sending MLD report messages.
The network then delivers data to a potentially unlimited number of receivers, using only one copy of the multicast data on each subnet. IPv6 hosts that wish to receive the traffic are known as group members. Packets delivered to group members are identified by a single multicast group address. Multicast packets are delivered to a group using best-effort reliability, just like IPv6 unicast packets. The multicast environment consists of senders and receivers. Any host, regardless of whether it is a member of a group, can send to a group. However, only members of a group can listen to and receive the message. A multicast address is chosen for the receivers in a multicast group.
Senders use that address as the destination address of a datagram to reach all members of the group. Implementing IPv6 Multicast 1