Subject: PIM hello option DR priority

From: Fred Bauer <[email-masked]>
Date: Thu, 25 May 2000 11:04:01 -0700

At Interop in Las Vegas this year I noticed that Junipers running
JunOS release 4.0 were sending PIM hello option 19 with a length
of 4 (Invalid Bidirectional PIM capable option). Presumably what
the coder was trying to do was specify DR priority, but was following
the older spec, draft-ietf-idmr-pimv2-dr-priority-00.txt. Has anyone
else seen similar behavior on this or other manufacturers' routers?

By the way, if anyone from Juniper is listening, I imagine that
you'd like to fix this.

Fred

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From: Tom Pusateri <[email-masked]>
Date: Thu, 25 May 2000 12:27:17 -0700

>By the way, if anyone from Juniper is listening, I imagine that

Actually, that code has been in there since the DR priority draft came
out and is the same in all JUNOS releases shipping for the past few
years.

So was the DR priority draft wrong because the option was already
used or did the option get re-assigned?

Thanks,
Tom

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From: Liming Wei <[email-masked]>
Date: Thu, 25 May 2000 16:13:43 -0700 (PDT)

Sigh, this was due to the code assignment conflict with other options.
It was discovered only later when the drafts were consolidated. I
thought I was the only coder who implemented the DR priority option at
that time, and it would only involve myself if I changed it..

It was an oversight that this was not included in the "significant
changes" section of the later PIM-SM draft, since we were only doing
diffs against a previous RFC, not against the previous
Internet-Drafts...

It could have been worse, but the positive side of this is that the DR
election mechanism is robust enough to not cause havoc. If not all
neighbors are DR-priority capable, they will drop down to the old
address-comparison-only mode, and DR-priority will become active again
when the "non-capable" neighbors all disappear.

It is hard to guess how much deployment has been done with
the DR election priority option and the Bi-dir option. I can
think of the following few options to move forward:

 1) Deprecate both values of 19 and 18 as valid Hello options.
    Assign new values to both DR-prio and Bi-Dir options. Everyone
    needs to switch;

 2) Keep the current PIM-SM option value assignment, and let those
    who implemented draft-ietf-idmr-pimv2-dr-priority-00.txt
    change their code;

 3) Deprecate the current Bi-Dir option code 19, making it the
    DR priority election priority code again. Make code 18 an
    invalid option, and reassign a new code for Bi-Dir option

    This probably is acceptable if Bi-dir PIM is not widely
    deployed yet. But I will understand if people don't want to
    say so here.

 Comments ?

-Liming

> Date: Thu, 25 May 2000 12:27:17 -0700
> From: Tom Pusateri <[email-masked]>
>

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From: Tom Pusateri <[email-masked]>
Date: Sat, 27 May 2000 19:24:28 -0700

My vote is for #3 since it is deployed.

Tom