Subject: [pim] G without an RP owner

From: juan <[email-masked]>
Date: Wed, 5 Dec 2001 15:25:51 -0800 (PST)

Hi,

What should be done with various events associated with
a group-address G1 for which neither this router, nor any
other routers have claimed ownership?

Example:

- we receive a downstrem pim-join(*,G1)
  * downstream state machine transitions from NI to J
  * what about upstream (*,G1) state? Do we transition from
    "not joined" to "joined" without sending our upstream join?

- if later we receive a data packet (S1,G1), via the correct rpf(s)
  * do we forward the packet?

Thanks for any comments regarding this issue,
Juan

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From: John Zwiebel <[email-masked]>
Date: Wed, 5 Dec 2001 17:54:00 -0800

Let me try this.
What I think you are saying is you've received a (*,G) join sent
to an RP that is not in your RP map or cache or whatever you want to
call it.

PIMv1 would have assumed that the guy sending the join was smarter than
the receiving router and would have created (*,G) and forwarded it on.

You're better off though dropping it.

On Wednesday, December 5, 2001, at 03:25  PM, juan wrote:

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> Pim-external mailing list
> [email-masked]
> http://mailist.procket.com/mailman/listinfo/pim-external

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From: juan <[email-masked]>
Date: Wed, 5 Dec 2001 18:33:16 -0800 (PST)

> to an RP that is not in your RP map or cache or whatever you want to

Yep.  For some reason the downstream router sending the join(*,G1) knows
about the RP for G1, but the router receiving the join does not
know which RP maps to G1 (e.g router has recently come up and has not
yet received BSR info; or the router aged-out RP info before the downstream 
router).

Or I guess it doesn't even need to be the reception of a pim-join(*,G1);
receiving an igmp-join(*,G1), and not knowing which RP corresponds to G1
(e.g. CRP is down), would be a similar situation.

If we start receiving mcast data (S1,G1), where S1 could be from a subnet
to which the router is directly connected, is the router supposed to
forward the mcast data packets to the interface through which the join
was received?  If it does, then it'd have to keep track of these "orphan"
G's without RP owners, so that when/if we later do learn about the RP,
we can then update the outgoing-iface-list (e.g. start sending encapsulated
pim-regs to the RP), plus generate the upstream join(*,G1).

> You're better off though dropping it.

I agree; it's the easy thing to do.  Just want to make sure it's the 
right thing to do.