Subject: Re: [Isis-wg] draft-previdi-filsfils-isis-segment-routing

From: Patryk Konczyk <[email-masked]>
Date: Thu, 25 Apr 2013 16:31:22 +0100

Hello Stefano I've seen Clarence presentation about Segment Routing
at MWC in Paris. I like the concept of using IGP for signalling and to
simply use existing tools like remote LFA for traffic protection.
Traffic Engineering looks simple as well. My initial concern was
around large label stack  especially in cases where there is
significant amount of Traffic Engineering going on. Clarence pointed
out that this can be resolved with loose hops using just two labels in
majority of the cases.
 I was also chatting to Stewart Bryant and he suggested compressing
the label stack I belive you touched on that on page 6 in the ECMP
context. I was wondering if this could be extended for strict and
loose path signalled with single label only, so that we have the same
label stack as in LDP/RSVP based solution. This probably would require
additional signalling.
 IPv6 variant is looking interesting as well. I'm hoping that more
details will appear in the draft shortly and we will have more
discussion on the mailing list.

In Section 2.2 comparative study has been mentioned could your share
more details ?

 Also are there any plans to discuss segment routing in Berlin ?

Thanks Patryk Konczyk

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From: stefano previdi <[email-masked]>
Date: Mon, 29 Apr 2013 16:00:16 +0200

Hi Patryk,

> out that this can be resolved with loose hops using just two labels in

indeed. In current SP topologies, and with current HW capabilities, 
the label stack size is a non issue. Having said that, we shouldn't 
neglect mechanisms for stack compression anyway.

> label stack as in LDP/RSVP based solution. This probably would require

the question is whether (and how much more) do you need to compress 
the stack and what benefits it brings you (assuming my statement 
above).

> discussion on the mailing list.

yes, we're in the process of updating the draft and more details 
are to come soon.

> Also are there any plans to discuss segment routing in Berlin ?

Hopefully yes!

Thanks.
s.