Subject: Re: PIM hello option DR priority

From: Fred Bauer <[email-masked]>
Date: Thu, 25 May 2000 16:49:11 -0700

Liming,

My 2 cents worth is that option 3 makes the most sense given that
routers out there already honor DR-priority = 19. I am guessing 
that bidir is not yet widely established, so the impact will be
minimal.

Fred

>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]>
>> 
>> In message <[email-masked]> you write:
>> >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
>> 
>> 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
>> 
>

---

From: John Meylor <[email-masked]>
Date: Tue, 30 May 2000 14:01:06 -0700

Fred Bauer wrote:
> routers out there already honor DR-priority = 19. 

actually our implementation is using DR-priority = 18, and
we have fairly significant deployment using this.

I am guessing
> that bidir is not yet widely established, so the impact will be

probably true, I don't think the issue would be with bidir,
but rather with existing DR priority deployment.

 John

---

From: Bill Fenner <[email-masked]>
Date: Tue, 30 May 2000 14:23:08 -0700

I'm still interested in recreating the timeline.
draft-ietf-idmr-pimv2-dr-priority-00.txt was published in March of 1998,
with 2 cisco Systems authors, and specified option #19.  When did IOS
change to 18, and why?

Also, anyone with bidir implementations, how will your implementation
treat an option #19 with length 4?

  Bill

---

From: Yiqun Cai <[email-masked]>
Date: Tue, 30 May 2000 14:44:51 -0700 (PDT)

> treat an option #19 with length 4?

skip the 4 bytes and move on to the next TLV.

-- 
Yiqun

---

From: Liming Wei <[email-masked]>
Date: Tue, 30 May 2000 15:46:11 -0700 (PDT)

> From: Bill Fenner <[email-masked]>
> 

Ok ok. I'm not sure what to say, other than an apology (probably
useless). The code in 12.0T was actually Dino's code, while I edited
the draft. It must have been that the bi-dir code and dr priority code
were in the same place. When we came to consolidate the values, I took
them from the code, instead of from the expired drafts. I was not
aware of any non-cisco implementations, until a couple of weeks back.
(so much for a lesson for a draft editor.)
I won't go into more details in history, but would like to see a
resolution soon. Ravi/Fred's interop logic can be used as a short term
solution, and we better come to a clean solution considering
all factors.

-Liming

---

From: Dino Farinacci <[email-masked]>
Date: Tue, 30 May 2000 16:31:12 -0700

>> the draft. It must have been that the bi-dir code and dr priority code
   
    All that I recall is that the DR option ID was created first and the 
    Bidir ID, when implemented was a less mature draft. The original DR option
    ID was set to 19. I wondered why 18 was skipped and not assigned to
    any draft. I asked Liming, and he said he didn't know. So he said he 
    would change the draft to make the DR option 18, so I picked 19 for 
    Bidir and the implementation reflected this.

    When I originally did the Bidir code, I did the DR option code in the
    "same" feature release. So the code was self consistent but had the
    opportunity to be uninteroperable. I think we tried to get the ID updated
    before anyone else would have implemented the DR option.

    Tom probably snatch the 19 for the DR option before Liming had a chance to
    publish the new ID. Hence the problem.

Dino

---

From: Bill Fenner <[email-masked]>
Date: Tue, 30 May 2000 17:09:50 -0700

It feels to me like people are missing the fact that the value of
19 for DR-Priority was published for 19 months.  That is a pretty
large window for people to implement.  (The first spec renumbering
it to 18 was only published 7 months ago.)

  Bill

---

From: Liming Wei <[email-masked]>
Date: Tue, 30 May 2000 19:53:22 -0700 (PDT)

> Cc: [email-masked]

Hmmm, Bill, have you bought the wrong stock at the wrong time :-) ?
How does repeating this help the current situation ?

The updated PIM-SM draft was posted on the WG mailing list a couple of
times way before it was sent into the repository. The DR priority
draft expired a long time ago. The first time the updated PIM-SM draft
was posted on the PIM WG list could be early 1999 (or even late 98).

Plus, all IDs have the following disclaimer (Tom, this is only
to remind Bill):

   Internet-Drafts are draft documents valid for a maximum of six
   months and may be updated, replaced, or obsoleted by other
   documents at any time.  

I assume the above only applies to non-expired drafts.

Again, if we were aware of ANY implementations outside of cisco...

-Liming