Subject: [Idr] advertising more than one route to a destination

From: Yakov Rekhter <[email-masked]>
Date: Mon, 15 Aug 2005 09:09:44 -0700

Folks,

As you know the basic BGP spec currently restricts a BGP speaker
to advertise at most a single route to a given destination (given
address prefix).

The purpose of this e-mail is to solicit opinions on (a) what
applications could benefit if the above restriction is relaxed, as
to allow a BGP speaker to advertise multiple routes to a given
destination, and (b) whether the IDR WG should start work on extending
BGP to support these applications.

With this in mind, please answer the following two questions:

1. What applications could benefit from allowing a BGP speaker
to advertise multiple routes to a destination ? 

2. Should the IDR WG start work on extending BGP to support
such applications ?

The deadline for response is August 29.

Yakov.

_______________________________________________
Idr mailing list
[email-masked]
https://www1.ietf.org/mailman/listinfo/idr

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From: Paul Jakma <[email-masked]>
Date: Mon, 15 Aug 2005 17:17:09 +0100 (IST)

On Mon, 15 Aug 2005, Yakov Rekhter wrote:

> destination, and (b) whether the IDR WG should start work on 
> extending BGP to support these applications.

a) eBGP Route-servers at IXes, to act as 'dumb'
   (non-best-path-selecting) reflectors so as to reduce eBGP 'mesh'
   between IX users.

   iBGP reflectors, to reduce route-oscillations (see Walton, et al).

b) Yes.

    Note: there's at least one private draft examining this.

regards,
-- 
Paul Jakma	[email-masked]	[email-masked]	Key ID: 64A2FF6A
Fortune:
Consultant, n.:
 	An ordinary man a long way from home.

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From: Enke Chen <[email-masked]>
Date: Mon, 15 Aug 2005 10:59:38 -0700

Hi, Yakov:

>to advertise multiple routes to a destination ?

Two important ibgp applications:

a) for eliminating persistent route oscillations by route reflection or 
confederation.
b) for eliminating forwarding loops with ibgp multipath and route 
reflection.

>2. Should the IDR WG start work on extending BGP to support
Yes.

-- Enke

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From: Olivier Bonaventure <[email-masked]>
Date: Tue, 16 Aug 2005 12:06:00 +0200

Yakov,
> to advertise multiple routes to a destination ? 

In addition to the other applications mentionned by Enke and Paul :

* Route-server type applications such as :
  - a monitoring server that learns via iBGP sessions both the active
and candidate routes available inside an AS
  - a PCE could use such an iBGP extension to collect multiple routes to
external destinations from the RR or border routers. This will aid in
the establishment of interdomain LSPs, see
http://www.info.ucl.ac.be/~cpe/Pelsser_IPOM.pdf

* Load-balancing situations where route reflectors advertise multiple
routes to their clients to allow them to load-balance their traffic

* Fast-convergence situations where route reflectors advertise both the
best paths and alternate paths to their clients to allow them to react
quickly (i.e. without waiting for an iBGP convergence) to failures

> 2. Should the IDR WG start work on extending BGP to support

Yes

Best regards,

Olivier

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From: "Manav Bhatia" <[email-masked]>
Date: Tue, 16 Aug 2005 18:07:20 +0530

Yes.

Manav