CANOGA PERKINS CanogaOS Configuration Guide - Manual (Page 175)

CanogaOS Configuration Guide
Proprietary & Confidential Canoga Perkins Metro Ethernet Switches Page 175 of 350
24 Configuring IP Multicast-Routing
24.1 Multicast Overview
Multicast protocols allow a group or channel to be accessed over different networks by multiple
stations (clients) for the receipt and transmit of multicast data.
Distribution of stock quotes, video transmissions such as news services and remote classrooms,
and video conferencing are all examples of applications that use multicast routing.
• Internet Group Management Protocol (IGMP) is used among hosts on a LAN and the routers
(and multilayer switches) on that LAN to track the multicast groups of which hosts are members.
• Protocol-Independent Multicast (PIM) protocol is used among routers and multilayer switches
to
track which multicast packets to forward to each other and to their directly connected LANs.
PIM has two mode: Sparse-mode and Dense-mode. Currently, we only support Sparse-mode
24.2 IGMP Configuration
To participate in IP multicasting, multicast hosts, routers, and multilayer switches must have the
IGMPoperating. This protocol defines the querier and host roles:
• A querier is a network device that sends query messages to discover which network devices are
members of a given multicast group.
• A host is a receiver that sends report messages (in response to query messages) to inform a querier
of a host membership.
A set of queriers and hosts that receive multicast data streams from the same source is called a
multicast group. Queriers and hosts use IGMP messages to join and leave multicast groups.
Any host, regardless of whether it is a member of a group, can send to a group. However, only
the members of a group receive the message. Membership in a multicast group is dynamic; hosts
can join and leave at any time. There is no restriction on the location or number of members in a
multicast group.
A host can be a member of more than one multicast group at a time. How active a multicast
group is and what members it has can vary from group to group and from time to time. A
multicast group can be active for a long time, or it can be very short-lived. Membership in a
group can constantly change. A group that has members can have no activity.
IGMP packets are sent using these IP multicast group addresses:
• IGMP general queries are destined to the address 224.0.0.1 (all systems on a subnet).
• IGMP group-specific queries are destined to the group IP address for which the switch is querying.
• IGMP group membership reports are destined to the group IP address for which the switch is
reporting.
• IGMP Version 2 (IGMPv2) leave messages are destined to the address 224.0.0.2
(all-multicast-routers on a subnet). In some old host IP stacks, leave messages might be destined to
the group IP address rather than to the all-routers address.
24.2.1 References
The IGMP module is based on the following RFC :
RFC 1112