Overview - HP ProCurve Secure Router 7203 dl Advanced Management And Configuration Manual

Overview

In order to receive multicast packets from one network and route them to
hosts in different networks, a router must implement a multicast routing
protocol. The ProCurve Secure Router supports Protocol Independent Multi-
cast-Sparse Mode (PIM-SM).
Working with whatever unicast routing protocols the routers implement, PIM-
SM allows routers in a PIM domain to construct a shared, unidirectional tree
for each multicast group active in the network. The shared tree is rooted at a
rendezvous point (RP) router, which is the router responsible for drawing
multicast traffic from a new source to receivers in the associated group.
PIM-SM then allows a router to construct a more efficient, source-specific tree
after it actually begins to receive multicast traffic.
PIM-SM also regulates the selection of:
A designated router (DR) for each multi-access network—The DR for-
wards join/prunes for the subnet. It also forwards multicast traffic from
any sources on the subnet.
An RP for each multicast group—The RP acts as the root of the multicast
tree; it receives join/prunes for the group, as well as receives multicasts
from sources and forwarding them as needed.
To construct the unidirectional multicast trees, routers send PIM join/prune
packets to RPs (or, for a source-specific trees, to the sources' DRs). A join/
prune packet includes joins for the groups for which a router needs to receive
multicasts. The packet also includes prunes for the groups for which the router
no longer needs to forward multicasts to connected hosts or downstream
routers.
Routers construct their multicast routing table based on the PIM join/prune
packets that they receive and based on the Internet Group Management
Protocol (IGMP) joins and leaves that they receive from connected hosts. An
IGMP join for a group indicates that at least one host in a subnet is a member
of that group. (See Chapter 10: Configuring Multicast Support for a Stub
Network for more information on IGMP.)
Configuring Multicast Support with PIM-SM
Overview
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