Subject: A modest proposal: get rid of (*,*,RP) state

From: Bill Fenner <[email-masked]>
Date: Thu, 8 Jun 2000 18:35:37 -0700 (PDT)

Dear PIM'ers,

  As part of our rewrite of the PIM-SM spec, we would like to get
rid of (*,*,RP) state.  It was introduced for interoperability with
dense-mode protocols in the "upside-down" mode of a dense-mode
backbone and PIM-SM stubs.  In today's Internet, this mode doesn't
exist, and MSDP and Domain-Wide Reports are a much better way to
attach a dense-mode stub site.

  Given this, we'd like to ask the following questions:
1) Does anyone handle receiving and propagating (*,*,RP) joins?
2) Does anyone implement the PMBR functionality that initiates
   (*,*,RP) joins?
3) Most importantly, does anyone have any objections to eliminating
   the (*,*,RP) functionality?

Thanks,
  Bill & Mark & Hugh & Isidor

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From: Tom Pusateri <[email-masked]>
Date: Fri, 09 Jun 2000 12:37:48 -0700

>1) Does anyone handle receiving and propagating (*,*,RP) joins?

Juniper does not.

>2) Does anyone implement the PMBR functionality that initiates

Juniper does not.

>   the (*,*,RP) functionality?

No objections.

Thanks,
Tom

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From: Ravi Puvvala <[email-masked]>
Date: Fri, 09 Jun 2000 13:32:33 -0700

| In message <[email-masked]> you write:
| >  Given this, we'd like to ask the following questions:
| >1) Does anyone handle receiving and propagating (*,*,RP) joins?

We (Nokia) do support this option.

| >2) Does anyone implement the PMBR functionality that initiates
| >   (*,*,RP) joins?

We do not currently have this support.

| >3) Most importantly, does anyone have any objections to eliminating
| >   the (*,*,RP) functionality?

No problem.. In lieu of DWR and MSDP, I think this is the right thing 
to do.

Ravi

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From: Chirayu Shah <[email-masked]>
Date: Fri, 09 Jun 2000 17:06:36 -0400

>1) Does anyone handle receiving and propagating (*,*,RP) joins?

Ericsson (Torrent) does not support it.

>2) Does anyone implement the PMBR functionality that initiates

We do not.

>   the (*,*,RP) functionality?

No objection from our side.

>  Bill & Mark & Hugh & Isidor

Chirayu.

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From: Nimesh Ray <[email-masked]>
Date: Fri, 09 Jun 2000 14:57:39 -0700

> >1) Does anyone handle receiving and propagating (*,*,RP) joins?

Cabletron Systems (Riverstone Networks) does not

> >2) Does anyone implement the PMBR functionality that initiates

No.

> >   the (*,*,RP) functionality?

No objection from our side..

Nimesh

-- 
Nimesh Ray				email:	[email-masked]
Member of Technical Staff		Office: (408) 878-6516
Yago Systems, Inc./Cabletron Systems	Fax:    (408) 878-6501

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From: Nair Venugopal <[email-masked]>
Date: Fri, 9 Jun 2000 18:11:22 -0700 (PDT)

> 1) Does anyone handle receiving and propagating (*,*,RP) joins?

The 3Com implementation does not.

> 2) Does anyone implement the PMBR functionality that initiates

The 3Com implementation does not.

No objections.

thanks 
--Venu

--------------------------------------------------------------------
Nair Venugopal  --- [email-masked] --- 3Com WAP Engineering

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From: Pavlin Ivanov Radoslavov <[email-masked]>
Date: Mon, 12 Jun 2000 04:04:57 -0700

> 1) Does anyone handle receiving and propagating (*,*,RP) joins?

(For whatever worths mentioning it):
pimd implements it, but it was never tested.

> 2) Does anyone implement the PMBR functionality that initiates

pimd does not.

>    the (*,*,RP) functionality?

If we can get away without (*,*,RP) in the long term (i.e. with BGMP
in mind, but see my question below), I would prefer (*,*,RP) support
to be optional (only if compatibility with PMBR is needed, for
example). PIM-SM without (*,*,RP) will simplify significantly
the protocol.
It is hard for me to believe that in the future someone would want
to use (*,*,RP) to "push" the data from all PIM-SM domains to the
dense-mode domains, because this simply won't scale. Dense-mode
domains should use Domain-Wide Reports instead, and only those
domains should "pay" the protocol complexity price (i.e. running one
more protocol: DWR) instead the rest of the world.

In another email Dave Thaler wrote:
===
  As a co-author of the BGMP spec, I'd respond (to the chair of the BGMP
  WG... :) that when PIM-SM is used as the IGP, while the recommended scenario
  is to have the BR's be RPs, some people have suggested that they would
  prefer the luxury of having the RPs and BRs be separate (go figure).

  To allow this, I think you either have to use MSDP internally (with its 
  potential encapsulation problems) or (*,*,RP) from the best exit router 
  back to the RP.  Removing (*,*,RP) would have the effect of leaving only 
  two options: MSDP and RP=BR.  This is probably acceptable but it's worth
  knowing.
===

I am probably missing something in the picture, but why do we need
(*,*,RP) if the RP is not a border router?
To "push" the data from the internal sources over the BGMP trees to
the dense-mode domains? (again, Domain-Wide Reports running in the
dense-mode domains will eliminate the need for this).

A more detailed example here would be helpful :)

Pavlin

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From: Dave Thaler <[email-masked]>
Date: Mon, 12 Jun 2000 10:57:57 -0700 (PDT)

> A more detailed example here would be helpful :)

Technically one would only need a bunch of (*,Gprefix,RP) joins per RP
but those aren't specified, so a single (*,*,RP) per RP works :)

The exit router for Gprefix (i.e. the one towards the root domain
for Gprefix) needs to receive all data from the subtree under it
for all groups G in Gprefix.  If it's the RP for all such groups, 
there's no problem, all packets travelling uptree automatically
get sent to it.

If it's not the RP, it needs a way to join to all RPs that serve
groups in Gprefix.  (And any other Gprefix'es for which it is
the best exit router.)  DWRs don't help here, since this is a border
router needing to set up a path to an internal RP.

So to repeat, solutions I'm aware of are:
1) Don't run PIM-SM... run BGMP as the M-IGP (as Dino hinted, I think)
2) Run PIM-SM with RPs=BRs.
3) Run PIM-SM with MSDP for internal peerings only, between RPs & BRs.
4) Run PIM-SM with (*,*,RP) joins from exit BRs to RPs.

-Dave

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From: Ardas Cilingiroglu <[email-masked]>
Date: Sun, 11 Jun 2000 13:58:03 -0400

> 1) Does anyone handle receiving and propagating (*,*,RP) joins?

Marconi (FORE) does...

> 2) Does anyone implement the PMBR functionality that initiates

Marconi does...

>    the (*,*,RP) functionality?

same concerns with other people...