Rendezvous Point - Juniper ACX1000 Configuration Manual

Rendezvous Point

Copyright © 2017, Juniper Networks, Inc.
Chapter 22: Configuring Multicast Listener Discovery and Protocol-Independent Multicast
NOTE: If the number of PIM join messages exceeds the configured MTU, the
messages are fragmented in IPv6 PIM sparse mode. To avoid the
fragmentation of PIM join messages, the multicast traffic receives the
interface MTU instead of the path MTU.
The major characteristics of PIM sparse mode are as follows:
Routers with downstream receivers join a PIM sparse-mode tree through an explicit
join message.
PIM sparse-mode RPs are the routers where receivers meet sources.
Senders announce their existence to one or more RPs, and receivers query RPs to find
multicast sessions.
Once receivers get content from sources through the RP, the last-hop router (the router
closest to the receiver) can optionally remove the RP from the shared distribution tree
(* ,G) if the new source-based tree (S,G) is shorter. Receivers can then get content
directly from the source.
The transitional aspect of PIM sparse mode from shared to source-based tree is one
of the major features of PIM, because it prevents overloading the RP or surrounding
core links.
There are related issues regarding source, RPs, and receivers when sparse mode multicast
is used:
Sources must be able to send to all RPs.
RPs must all know one another.
Receivers must send explicit join messages to a known RP.
Receivers initially need to know only one RP (they later learn about others).
Receivers can explicitly prune themselves from a tree.
Receivers that never transition to a source-based tree are effectively running Core
Based Trees (CBT).
PIM sparse mode has standard features for all of these issues.
The RP router serves as the information exchange point for the other routers. All routers
in a PIM domain must provide mapping to an RP router. It is the only router that needs
to know the active sources for a domain—the other routers just need to know how to
reach the RP. In this way, the RP matches receivers with sources.
The RP router is downstream from the source and forms one end of the shortest-path
tree. As shown in Figure 35 on page
thus forms one end of the rendezvous-point tree.
678, the RP router is upstream from the receiver and
677