Re: [Isis-wg] Request for WG adoption of draft-xu-isis-mpls-elc-00

"Bragg, Nigel" <nbragg@ciena.com> Thu, 05 June 2014 15:43 UTC

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From: "Bragg, Nigel" <nbragg@ciena.com>
To: Robert Raszuk <robert@raszuk.net>
Date: Thu, 5 Jun 2014 11:42:39 -0400
Thread-Topic: [Isis-wg] Request for WG adoption of draft-xu-isis-mpls-elc-00
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Subject: Re: [Isis-wg] Request for WG adoption of draft-xu-isis-mpls-elc-00
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I agree with you, Robert, for fundamental reasons.   When you stand back there are two ways of mitigating network congestion :
-	spread the offered load over the widest range of routes available,  or
-	place load onto routes specifically selected to minimize the chance of conflict for resources.
ECMP mechanizes one of these, SR the other;  they are bookends.

So, launch with entropy immediately under the top (i.e.  egress node) label -- goes ECMP route;
Anything else is parsed as an SR label stack ?
-	far too simple  :-), but might be a start.
Nigel

-----Original Message-----
From: Isis-wg [mailto:isis-wg-bounces@ietf.org] On Behalf Of Robert Raszuk
Sent: 05 June 2014 15:50
To: Nobo Akiya (nobo)
Cc: draft-xu-isis-mpls-elc@tools.ietf.org; isis-chairs@tools.ietf.org; isis-wg@ietf.org
Subject: Re: [Isis-wg] Request for WG adoption of draft-xu-isis-mpls-elc-00

> always advertise _max_ number of SIDs for ECMP.

I meant that. No point to go lower at all.

> Still, in an SR network consisting of 100 nodes ... each network node used to have 100 node SID forwarding entries (assuming one SID advertised per node) but now each network node will have 3200 or 6400 or 12800 node SID forwarding entries. That's a huge increase.

Assume no aggregation it looks huge, but it's tiny if you compare it with state required on ingress as example where all of your overlay services reside.

> Sure the forwarding table can do some aggregation but number of "resources" reserved, consumed, advertised and OAM requires to support them are still enlarged significantly.

I do not agree. Assume v6 SR where I advertise instead of single SID say a block of /96. It is still one prefix for all what forwarding needs to care about.  What would be different for that prefix vs /128 prefix from the point of view of  "resources" reserved, consumed, advertised and OAM ?

> I still see tackling EL to be appealing :)

Is this still more appealing then say mpls over UDP draft ;-) ?
http://tools.ietf.org/html/draft-ietf-mpls-in-udp-05

Cheers,
R.

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