In-line [Uma]: -- Uma C.
-----Original Message----- From: spring [mailto:[email protected]] On Behalf Of Jon Mitchell Sent: Wednesday, November 04, 2015 5:47 PM To: Lizhenbin Cc: [email protected] Subject: Re: [spring] Implementation Report on draft-ietf-spring-segment-routing-ldp-interop On 03/11/15 01:21 +0000, Lizhenbin wrote: > Hi Folks, > > I proposed my concern on the implementation of interoperability between LDP > and SR again in IETF. I also would like to remind you of my draft again: > > https://tools.ietf.org/html/draft-li-spring-compare-sr-ldp-rsvpte-00 > With the hopes of clarifying Lizhenbin's comments which I found a bit hard to follow both at the mic and in this email I went through this draft and found the most applicable section to be 4.2 (proxy egress) in the draft above versus Section 6 which he referenced. I believe this is the concern he is raising (Lizhenbin - please feel free to correct me). In inter-as option C and like technologies, there are two ways to distribute received label information from ASBR/PE to other PE's, either via BGP label-unicast or IGP (make other networks PE's look similar to this network's PE from label stack standpoint by redistribute prefixes into IGP and have PE advertise via LDP which results in a 2 label approach versus 3 label in BGP case). I'll refer to these as C1 (IGP) and C2 (BGP). draft-ietf-spring-segment-routing-ldp-interop-00 already does a good job of describing that option C/CsC/Seamless MPLS can be supported in it's Section 6 (using C2), but it could add a bit more text I think admitting that it can't support using a C1 model as many providers have deployed and therefore an extra label will be incurred. At least I can't think of an easy way to support having multiple ASBR's handle mapping these dynamically learned prefixes from the other AS to the same SID... [Uma]: "easy way" - fair description. Two not so easy ways for Option C- 2 labels with SR: 1. Make sure all your ASBRs have same SRGB provisioned and make sure same global index is assigned for redistributed PE prefixes from other AS - Only way is to use same vendor nodes( if possible) 2. Use context labels/recursive label lookups using anycast segments - All vendors may not support and support is limited to few platforms even with the same vendor Apart from the above Section 6 of this draft alludes to few practical issues with LFA/RLFA when LDP-SR interworking in place.. -- Uma C. _______________________________________________ spring mailing list [email protected] https://www.ietf.org/mailman/listinfo/spring
