From: Yasser Aly (blackyeyes00@hotmail.com)
Date: Mon Dec 29 2003 - 20:39:00 GMT-3
Dear All,
I am confused about the role of RP in multicast sparse-mode. I thought
that a shared distribution tree will be created where sources register
themselves with the RP and receivers send request to RP.
However after reading the following lines from a PDF speaking about
configuring RP, I got confused.
Kindly have a look at the lines below and let me hear your feedback.
My questions mainly are:
1) Will multicast traffic pass by the PR all the time on its way from source
to receiver or not ?
2) Is it true that after the first hop router of the receiver learns about
the source, it will send a join message directly to the source, creating a
source-based distribution tree ??
Your thoughts are highly appreciated
---------
An RP acts as the meeting place for sources and receivers of multicast data.
In a PIM-SM network,
sources must send their traffic to the RP. This traffic is then forwarded to
receivers down a shared
distribution tree. By default, when the first hop router of the receiver
learns about the source, it will send
a join message directly to the source, creating a source-based distribution
tree from the source to the
receiver. This source tree does not include the RP unless the RP is located
within the shortest path
between the source and receiver.
In most cases, the placement of the RP in the network is not a complex
decision. By default, the RP is
needed only to start new sessions with sources and receivers. Consequently,
the RP experiences little
overhead from traffic flow or processing. In PIM-SM version 2, the RP
requires less processing than in
PIM-SM version 1 because sources must only periodically register with the RP
to create state.
-----------------------
Regards,
Yasser
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