From: Yasser Aly (blackyeyes00@hotmail.com)
Date: Sat Jan 03 2004 - 07:53:50 GMT-3
Thanks Scott, Katsuri, and Demtry, It's now much more clear.
A small comment: I posted this question 4 days ago and the server just
decided to show it today :)
Sometimes the groupstudy server acts in a wierd way.
Regards,
Yasser
>From: "Scott Morris" <swm@emanon.com>
>Reply-To: <swm@emanon.com>
>To: "'Yasser Aly'" <blackyeyes00@hotmail.com>,<ccielab@groupstudy.com>
>Subject: RE: Role of Rendezvouz point in multicast
>Date: Fri, 2 Jan 2004 21:06:36 -0500
>
>The RP is the "know it all" of the multicast network. It prevents every
>router from needing to maintain state for every single multicast group that
>exists. In our lab networks, we generally could care less about this, but
>in real life, this could get ugly!
>
>Yes, an edge multicast router may decide to not go with the RP. But only
>AFTER it joins the shared tree and starts to get multicast traffic. Only
>then does it learn where the source actually is, and can examine its
>routing
>table to determine whether it really is on the shortest path tree (SPT) or
>not. If not, then it will create a source distribution tree directly to
>the
>source.
>
>So while yes it's true, it's not always the case. Just depends on where
>source and receivers are located compared to the RP.
>
>So specifically to your questions:
>
>1. Only for the *,G tree and MAYBE for the S,G tree.
>2. Only after seeing multicast traffic and IF it determines that the
>source
>is closer to itself than the RP is.
>
>HTH,
>
>
>Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713, CISSP,
>JNCIS, et al.
>IPExpert CCIE Program Manager
>IPExpert Sr. Technical Instructor
>swm@emanon.com/smorris@ipexpert.net
>http://www.ipexpert.net
>
>
>-----Original Message-----
>From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
>Yasser Aly
>Sent: Monday, December 29, 2003 6:39 PM
>To: ccielab@groupstudy.com
>Subject: Role of Rendezvouz point in multicast
>
>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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