Mld Protocol; Multicast Tree - Zte ZXR10 5900E Series User Manual

ZXR10 5900E Series User Manual (IPv6 Volume)
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MLD Protocol

Multicast Listener Discovery (MLD) can enable each IPv6 router to
discover multicast group members on its own local links (namely,
those nodes receiving multicast packets) and those adjacent nodes
which are interested in specified multicast addresses. To ensure
that all multicast packets are sent to all interested receivers (group
members), the information is provided to any multicast protocol
used in this router (other protocols).
MLD is an unsymmetrical protocol. IPv6 multicast members (hosts
or routers) and IPv6 multicast routers have different protocol be-
haviors. The purpose is to make IPv6 routers discover directly
connected IPv6 multicast monitors by using MLD. MLD collects and
maintains the group member relationship and provides the infor-
mation to the links where IPv6 monitors exist. Those routers, to
which multicast addressing one router (they are receivers them-
selves), execute two parts of the protocol, including messages re-
turned to themselves.
If more than one interfaces of a multicast router are connected
to a link, it is only necessary to execute MLD protocol routing on
one interface. For multicast members, it is necessary to execute
receiver of MLD protocol.

Multicast Tree

To enable multicast communication in the networks, the multicast
source, receivers and the paths of multicast packets should be
available. The most commonly used routing method is to establish
tree routes, which provides the following two advantages:
1. Packets are sent to different receivers along the tree branches
in parallel.
2. Packets are copied only on crotches, which minimizes the num-
ber of packets transmitted in the networks.
A multicast tree is a set that comprises a series of incoming inter-
faces and outgoing interfaces on router. It determines a unique
forwarding path between the subnet to which the multicast source
belongs and all the subnets that contain the group members.
There are two ways to construct a multicast tree: per-source mul-
ticast tree and shared multicast tree.
� Per-Source Multicast Tree
Per-source multicast tree is also called source shortest path
tree. It establishes a spanning tree to all receivers for each
source. This spanning tree takes the subnet to which the
source belongs as the root node. This tree reaches the subnets
to which the receivers belong. A multicast group may include
multi multicast sources.
corresponding multicast tree.
The method to construct a per-source multicast tree is reverse
path forwarding (RPF). Each router can find the shortest path to
the source and the corresponding outgoing interface according
Each source or pair (S, G) has a