Hi Sasha, sorry for being late. See below.
> On Jul 10, 2016, at 11:07 AM, Alexander Vainshtein > <alexander.vainsht...@ecitele.com> wrote: > > Hi all, > I have read the SR Resiliency Use Cases draft and I have an issue with the > path protection use case. > > The draft defines this use case with the following constrains/qualifiers > (quoting from Section 2): > · The operator configures two SPRING paths T1 and T2 from A to Z > · Initially, the customer traffic (e.g., PW traffic) is sent from A > to Z via T1. When T1 fails, the traffic is sent via T2. > · The two paths are made disjoint using the SPRING architecture > · The two configured paths T1 and T2 MUST NOT benefit from local > protection > > The draft does not go into any detail regarding the type of segments that the > operator uses when specifying T1 and T2, and the example given in the draft > can be interpreted in two ways: > · T1 and T2 are specified using only adjacency SID > · T1 and T2 are specified using node SIDs (or a mix of node SIDs and > adjacency SIDs). this is intentional. It’s a use case draft where we describe the various protection requirements and strategies for protection. It has never been intended to describe a specific solution. > If T1 and T2 are specified using node SIDs, there is no guarantee that these > paths, even if initially disjoint, will remain disjoint when the underlying > network topology changes. It all depends on various factors among which the topology and how these paths have been computed (i.e.: for which failure: link/node/srlg). IOW, you _can_ compute disjoint paths taking into account a given srlg failure. For sure, a path expressed through an exhaustive (list of adj-sid will give you the best guarantee on the path the packet will take in all cases but it is not the point of the draft. > Further, if TI FRR is enabled in the network for protection of non-TE SR > LSPs, the fragments of T1 and T2 that are specified using node SIDs will not > be excluded from local protection. > > So it seems that path protection for SR LSPs as specified in the draft is > only applicable to paths that are specified using only adjacency SIDs. I don’t disagree while I believe it mostly depends on the topology. More important is the fact that the document should not focus on one specific way of computing protection paths. s. > > Did I miss something substantial? > > Regards, and lots fo thanks in advance, > Sasha > > Office: +972-39266302 > Cell: +972-549266302 > Email: alexander.vainsht...@ecitele.com > > _______________________________________________ > spring mailing list > spring@ietf.org > https://www.ietf.org/mailman/listinfo/spring _______________________________________________ spring mailing list spring@ietf.org https://www.ietf.org/mailman/listinfo/spring
