Igmp; Multicast Tree - Zte ZXR10 8900 Series User Manual

ZXR10 8900 Series User Manual (IPv4 Routing Volume)
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ticast source. The multiple receivers of the same packet are
identified by using a single ID, which is called multicast group
address. In IP address allocation scenario, addresses of Class-D
(224.0.0.0~239.255.255.255) are multicast group addresses.
224.0.0.0~224.0.0.255
used for research and management.

IGMP

IGMP allows multicast router to learn information of multicast
group members. IGMP runs between host and multicast router.
A multicast router sends group member query messages to all
hosts periodically to learn which group members exist in the con-
nected networks. Each host returns a group member report mes-
sage. The message contains multicast group information and it
reports which group the host belongs to. When a host wants to be
added to a new group, it sends a group member report message
immediately instead of waiting for a query.
When a host begins to receive information as a group member, the
multicast router queries the group periodically to learn whether
this member is still in the group. If members of the group still
exist on an interface, the multicast router continues to forward
data. When the host leaves the group, it sends a leaving message
to the multicast router. The multicast router immediately queries
whether the group still contains active members or not. If yes, the
multicast router continues to forward data; if no, it stops forward-
ing data.
There are two versions of IGMP in practical applications, IGMP V1
and IGMP V2. IGMP V2 has more enhanced features than IGMP V1.
It uses 4 types of messages to accomplish information interaction
between hosts and router.
� Group member query
� V2 member report
�
Leave report
� V1 member report
V1 member report is used to be compatible with IGMP V1.

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:
� Packets are sent to different receivers along the tree branches
in parallel.
� Packets are copied only on crotches, which minimizes the num-
ber of packets transmitted in the networks.
and 239.0.0.0~239.255.255.255 are