Brocade Multi-Service IronWare Multicast Configuration Guide (Supporting R05.6.00) - Manual (Page 15)

Multi-Service IronWare Multicast Configuration Guide 3
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Overview of IP multicasting
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• Protocol Independent Multicast Dense mode (PIM DM) V1 (draft-ietf-pim-dm-05) and V2
(draft-ietf-pim-v2-dm-03)
• PIM Sparse mode (PIM SM) V2 (RFC 2362)
• Distance Vector Multicast Routing Protocol (DVMRP) V2 (RFC 1075)
NOTE
Each multicast protocol uses IGMP. IGMP is automatically enabled on an interface when you
configure PIM or DVMRP, and is disabled on the interface if you disable PIM or DVMRP.
Overview of IP multicasting
Multicast protocols allow a group or channel to be accessed over different networks by multiple
stations (clients) for the receipt and transmission 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.
Brocade devices support two multicast routing protocols — Distance Vector Multicast Routing
Protocol (DVMRP) and Protocol-Independent Multicast (PIM) protocol, along with the Internet Group
Membership Protocol (IGMP).
PIM and DVMRP are broadcast and pruning multicast protocols that deliver IP multicast datagrams.
These protocols employ reverse path lookup check and pruning to allow source-specific multicast
delivery trees to reach all group members. DVMRP and PIM build a different multicast tree for each
source and destination host group.
Both DVMRP and PIM can concurrently operate on different ports of a device. The CAM can hold up
to 1535 IPv4 multicast entries.
Multicast terms
The following terms are commonly used in discussing multicast-capable devices. These terms are
used throughout this chapter:
Node: Refers to a device.
Root Node: The node that initiates the tree building process. It is also the device that sends the
multicast packets down the multicast delivery tree.
Upstream: Represents the direction from which a device receives multicast data packets. An
upstream device is a node that sends multicast packets.
Downstream: Represents the direction to which a device forwards multicast data packets. A
downstream device is a node that receives multicast packets from upstream transmissions.
Group Presence: Means that a multicast group has been learned from one of the directly
connected interfaces. Members of the multicast group are present on the device.
Intermediate nodes: Devices that are in the path between source devices and leaf devices.
Leaf nodes: Devices that do not have any downstream devices.
Multicast Tree: A unique tree is built for each source group (S,G) pair. A multicast tree is comprised
of a root node and one or more nodes that are leaf or intermediate nodes.