Zte ZXR10 GER, Руководство пользователя

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ZXR10 GER (V2.6.03) General Excellent Router User Manual Volume-I
330 Confidential and Proprietary Information of ZTE CORPORATION
Topic Page No
PIM-SM Maintenance and Diagnosis 352
MSDP Maintenance and Diagnosis 356
Static Multicast Maintenance and Diagnosis 358
Multicast Configuration Example 358
Overview
In a multicast network, the sender sends a packet to multiple
receivers in a multicast mode. In such a situation, the sender is
called the multicast source. Multiple receivers for the same
packet are identified by same ID. This is called the multicast
group address. In the IP address allocation scheme, class D IP
address, 224.0.0.0-239.255.255.255, is just the multicast
address. The 224.0.0.0-224.0.0.255 and the 239.0.0.0-
239.255.255.255 are used for the purpose of research and
management.
If a host expects to receive multicast packets sent to a specific
group, it should intercept all the packets sent to the specific
group. When a host begins to receive multicast packet as a local
member of a certain group, the multicast router will sent queryig
message periodically to check if there is any local member still in
this multicast group.
If the router receives no Membership Reports in response, it
assumes that the multicast group has no local members and
does not forward any multicast packets addressed to this group.
The Internet group management protocol (IGMP) is used in
multicasts to complete this task. In this way, multicast routers
can know the members of multicast groups over networks and
there out determine whether to forward multicast packets to
their networks. When a multicast router receives a multicast
packet, it checks the multicast destination address of the packet
and will forward the packet only when its interface has members
of that group.
IGMP provides information that is required when packets are
forwarding to the destination (the last stage). Multicast routers
and the hosts that receive multicast data exchange information
mutually, is collected from the group members of the hosts that
directly connect to multicast routers.
IGMP is the protocol that is used by multicast routers to know
about information about multicast group members. Generally, it
employs two kinds of packets: group member enquiry packets
and group member report packets.
A multicast router periodically sends query messages of group
members to all hosts to know which specific group members
exist in the connected networks. The mainframe returns a report
Multicast
Address
IGMP
Multicast
Usage
Multicast
Group
Members