User's Manual

Table Of Contents
504
Users Manual of CS-6306R
Chapter 50. Multicast Configuration
Multicast Overview 50.1
The chapter describes how to cofigure the multicast routing protocol. For the details of the multicast routing
commands, refer to the part “Multicast Routing Commands”.
The traditional IP transmission allows only one host to communicate with a single host (unicast
communication) or to communicate with all hosts (broadcast communication). The multicast technology
allows one host to send message to some hosts. These hosts are called as group members.
The destination address of the message sent to the group member is a D-class address
(224.0.0.0~239.255.255.255). The multicast message is transmitted like UDP. It does not provide reliable
transmission and error control as TCP does.
The sender and the receiver make up of a multicast application. The sender can send the multicast message
without joining in a group. However, the receiver has to join in a group before it receives the message from the
group.
The relationship between group members is dynamic. The host can join in or leave a group at any time. There
is no limitation to the location and number of the group member. If necessary, a host can be a member of
multiple groups. Therefore, the state of the group and the number of group members varies with the time.
The router can maintain the routing table for forwarding multicast message by executing the multicast routing
protocol such as PIM-DM and PIM-SM. The router learns the state of the group members in the
directly-connected network segment through IGMP. The host can join in a designated IGMP group by sending
the IGMP Report message.
The IP multicast technology is suitable for the one-to-multiple multimedia application.
50.1.1 Multicast Routing Realization
In the router software of our router, the multicast routing includes the following regulations:
IGMP runs between the router and the host in the LAN, which is used to track the group member
relationship.
OLNK is a static multicast technology, which is used in the simple topology. It realizes the multicast
forwarding and effectively saves CPU and bandwidth.
PIM-DM, PIM-SM and DVMRP is dynamic multicast routing protocols. They run between routeres and
realizes the multicast forwarding by creating the multicast routing table.
The following figure shows the multicast protocols used in the IP multicast applications: