Subject: PIM-SM RP discovery

From: [email-masked] (Tim Dorcey)
Date: Thu, 9 Jan 1997 18:03:25 -0800

I'm not sure I understand how RP's work in Sparse Mode PIM.  From reading
draft-ietf-idmr-pim-arch-04 and draf-ietf-idmr-pim-sm-spec-09 it sounds
like the following:

A set of routers within a PIM routing domain are configured to be RP
candidates, and this set is made known to all PIM routers in the routing
domain.  PIM routers are able to uniquely resolve any multicast address to
one of the RP candidates by some hash function.  Hence, all PIM routers in
the routing domain can settle on the same RP for any given multicast
address.

Is that correct?  How would PIM routing occur among an arbitrary set of
hosts on the Internet?  E.g., how does a receiver in one PIM routing domain
discover a source that is in another?  Or is the entire Internet going to
be a single PIM routing domain?

Thanks for any clarification, or pointers to relevant documents.

Tim

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From: Dave Thaler <[email-masked]>
Date: Thu, 9 Jan 1997 23:01:23 -0500 (EST)

> domain.  
> PIM routers are able to uniquely resolve any multicast address to

Correct, with the proviso that the set made known to all PIM routers need not
necessarily be all the candidates.  (The Bootstrap Router in the domain is 
free to limit the size of the set everyone uses if it wants to.)

> How would PIM routing occur among an arbitrary set of hosts on the Internet?
> E.g., how does a receiver in one PIM routing domain

No to the last question.  Each PIM domain has its own RP.  The border
routers between the PIM domain and other domains (which could be DVMRP, 
PIM-DM, MOSPF, CBT, or whatever else) take care of making sure that
things work between domains.  See
   http://ds.internic.net/internet-drafts/draft-thaler-interop-00.{txt,ps}
for more info on rules for border routers.

-Dave

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From: Petri Helenius <[email-masked]>
Date: Fri, 10 Jan 1997 11:20:58 +0200 (EET)

> things work between domains.  See

Why cannot the border routing function between two PIM-SM domains?

Pete

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From: Dave Thaler <[email-masked]>
Date: Fri, 10 Jan 1997 10:12:02 -0500 (EST)

> Why cannot the border routing function between two PIM-SM domains?

It can.  (I guess that was included in "whatever else" :)

-Dave