Subject: join(s,g) on shared tree

From: Arup Acharya <[email-masked]>
Date: Sun, 17 Jan 99 15:44:37 EST

Hi!
 
Reading through the PIM-SM specs, I could not figure out
if it allows a DR to send source-specific joins on the shared
tree (e.g. in response to a IGMPv3 host sending a (S,G) membership
report). Such a join could be merged with a join(*,G) upstream;
this way, SPT creation needn't be triggered even if members wish
to receive source-specific traffic.

                  RP
                  |join(*,G)
                  R 
     join(*,G) /    \  join(S,G) : join_list={S}, RPT=1, WC=0
	      R1     R2            (sent towards RP)

I am probably missing something..

Arup

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From: Rusty Eddy <[email-masked]>
Date: Mon, 18 Jan 1999 09:37:50 -0800 (PST)

> tree (e.g. in response to a IGMPv3 host sending a (S,G) membership

the rfc2362 spec rely's on igmp v2.  so DR's only switch on traffic
parameters.  although allowing DR's to switch due to a v3 request
will be straight forward (assuming v3 has been implemented of course).

>      join(*,G) /    \  join(S,G) : join_list={S}, RPT=1, WC=0

the SPT must be created, even if it does merge with a shared 
tree, since the intention of joining an SPT is to form an SPT.
(your suggesting a protocol that perfers a shared tree over
a shortest path, such as BGMP :)

- rusty