SNR S2989G-24TX-UPS — настройка мультикаст-протоколов для эффективной передачи данных [253/553]

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S2989G-24TX Operation Manual

Chapter 5 Multicast Protocol Related Configuration

4-28

mode, Multicast data packet must be forwarded to a number of external interfaces to be

sent to all receiver sites in Multicast mode, thus Multicast transmission procedure is more

complicated than Unicast transmission procedure.

In order to guarantee that all Multicast packets get to the router via the shortest path,

the receipt interface of the Multicast packet must be checked in some certain way based

on Unicast router table; this checking mechanism is the basis for most Multicast Routing

Protocol to forward in Multicast mode --- RPF (Reverse Path Forwarding) check. Multicast

router makes use of the impressed packet source address to query Unicast Router Table

or independent Multicast Router Table to determine if the packet ingress interface is on

the shortest path from receipt site to source address. If shortest path Tree is used, then

the source address is the address of source host which sends Multicast Data Packets; if

Shared Tree is used, then the source address is the address of the root of the Shared-

Tree. When Multicast data packet gets to the router, if RPF check passes, then the data

packet is forwarded according to Multicast forward item, and the data packet will be

discarded else wise.

5.1.4

IP Multicast Application

IP Multicast technology has effectively solved the problem of sending in single point

and receiving in multipoint. It has achieved the effective data transmission from a point to

multiple points, saved a great deal of network bandwidth and reduced network load.

Making use of the Multicast property of network, some new value-added operations can

be supplied conveniently. In Information Service areas such as online living broadcast,

network TV, remote education, remote medicine, real time video/audio meeting, the

following applications may be supplied:

1) Application of Multimedia and Streaming Media

2) Data repository, finance application (stock) etc

3) Any data distribution application of “one point to multiple points”

In the situation of more and more multimedia operations in IP network, Multicast has

tremendous market potential and Multicast operation will be generalized and popularized.

5.2

IGMP

5.2.1

Introduction to IGMP

IGMP (Internet Group Management Protocol) is the protocol in TCP/IP protocol family

which is responsible for IP multicast member management. It is used to set up and