Chapter 21 Ipv4 Multicast Protocol; Ipv4 Multicast Protocol Overview; Introduction To Multicast; Multicast Address - Planet Networking & Communication WGSW-50040 Configuration Manual

50-port 10/100/1000mbps with 4 shared sfp managed gigabit switch

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This chapter will give an introduction to the configuration of IPv4 Multicast Protocol. All IPs in this chapter are

IPv4.

Various transmission modes can be adopted when the destination of packet (including data, sound and video)

transmission is the minority users in the network. One way is to use Unicast mode, i.e. to set up a separate

data transmission path for each user; or, to use Broadcast mode, which is to send messages to all users in

the network, and they will receive the Broadcast messages no matter they need or not. For example, if there

are 200 users in a network who want to receive the same packet, then the traditional solution is to send this

packet for 200 times separately via Unicast to guarantee the users who need the data can get all data wanted,

or send the data in the entire domain via Broadcast. Transferring the data in the whole range of network .The

users who need these data can get directly from the network. Both modes waste a great deal of valuable

bandwidth resource, and furthermore, Broadcast mode goes against the security and secrecy.

The emergence of IP Multicast technology solved this problem in time. The Multicast source only sends out

the message once, Multicast Routing Protocol sets up tree-routing for Multicast data packet, and then the

transferred packet just starts to be duplicated and distributed in the bifurcate crossing as far as possible. Thus

the packet can be sent to every user who needs it accurately and effectively.

It should be noticed that it is not necessary for Multicast source to join in Multicast group. It sends data to

some Multicast groups, but it is not necessarily a receiver of the group itself. There can be more than one

source sending packets to a Multicast group simultaneously. There may exist routers in the network which do

not support Multicast, but a Multicast router can encapsulate the Multicast packets into Unicast IP packets

with tunnel mode to send them to the Multicast router next to it, which will take off the Unicast IP header and

continue the Multicast transmission process, thus a big alteration of network structure is avoided. The primary

advantages of Multicast are:

1. Enhance efficiency: reduce network traffic, lighten the load of server and CPU

2. Optimize performance: reduce redundant traffic

3. Distributed application: Enable Multipoint Application

The destination address of Multicast message uses class D IP address with range from 224.0.0.0 to

239.255.255.255. D class address can not appear in the source IP address field of an IP message. In the

process of Unicast data transmission, the transmission path of a data packet is from source address routing to

destination address, and the transmission is performed with hop-by-hop principle. However, in IP Multicast

Chapter 21 IPv4 Multicast Protocol

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