Hi Chris,
> On Sep 12, 2016, at 4:04 PM, Chris Bowers <cbow...@juniper.net> wrote: > > As far as I can tell, this request for clarification of the text in > draft-ietf-spring-segment-routing-09 has not been addressed. > > Thanks, > Chris > > -----Original Message----- > From: spring [mailto:spring-boun...@ietf.org] On Behalf Of Chris Bowers > Sent: Wednesday, August 3, 2016 9:24 AM > To: spring@ietf.org > Subject: [spring] clarification of text in > draft-ietf-spring-segment-routing-09 > > SPRING WG, > > The following paragraph in section 3.2.1 of > draft-ietf-spring-segment-routing-09 is confusing. > > The ingress node of an SR domain validates that the path to a prefix, > advertised with a given algorithm, includes nodes all supporting the > advertised algorithm. In other words, when computing paths for a > given algorithm, the transit nodes MUST compute the algorithm X on > the IGP topology, regardless of the support of the algorithm X by the > nodes in that topology. As a consequence, if a node on the path does > not support algorithm X, the IGP-Prefix segment will be interrupted > and will drop packet on that node. It's the responsibility of the > ingress node using a segment to check that all downstream nodes > support the algorithm of the segment. > > I interpret the first, third, and fourth sentences in this paragraph as > saying that an ingress node should make sure that transit nodes on a path > install transit forwarding entries for prefix-SIDs for a given algorithm by > looking that > the SR-Algorithm (sub)-TLV advertised by the transit nodes before sending > traffic on that path. > > However, the second sentence in the paragraph confuses this interpretation. > > "In other words, when computing > paths for a > given algorithm, the transit nodes MUST compute the algorithm X on > the IGP topology, regardless of the support of the algorithm X by the > nodes in that topology." > > This sentence could be interpreted as saying that transit nodes must compute > all algorithms advertised by any node in the topology, even if the transit > node doesn't support the algorithm. This sentence doesn't make sense to me. > > A simple solution would be to delete this second sentence. I’d go for it. Thanks. s. > However, other clarifying text would be another solution. > > Thanks, > Chris > > _______________________________________________ > 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 _______________________________________________ spring mailing list spring@ietf.org https://www.ietf.org/mailman/listinfo/spring
