(For clarity: I’m not wearing any hats other than “WG contributor”.) Hi All,
Since there hasn’t been any definitive answer from the authors, nor any update to the draft to address the issue, and given that the disputed statement seems to be an important premise for evaluation of the fitness of the draft for adoption (at least, the authors considered it fundamental enough to put in the abstract): I’m opposed to adoption of the draft until this question has been settled, or at least meaningfully addressed. Regards, —John P.S.: I will also follow up to the main adoption thread to assist with issue tracking. > On Oct 13, 2021, at 6:28 PM, John Scudder <jgs=40juniper....@dmarc.ietf.org> > wrote: > > > Hi Folks, > > I’m struggling with the claim repeated throughout the beginning of > draft-filsfilscheng-spring-srv6-srh-compression-02 (Abstract, §1, §3) that > “this solution does not require any SRH data plane change”. > > I’m not aware of a standardized formal definition of “data plane”, it seems > to follow Justice Stewart’s maxim of “I know it when I see it”. However, > here’s an attempt, cribbed from some Washington University course slides: a > “local, per-router function that determines how a datagram arriving on a > router input port is forwarded to a router output port”. Seems reasonable. > > I also am not aware of a standardized formal definition of the term “SRH data > plane”, in fact this draft, its predecessors, some associated blog posts, and > Clarence’s dissertation, are the only places a search finds the phrase (but > it’s not formally defined in any of them). So I’m just going to assume it > means the data plane, as applied to packets that include an SRH. (I’m not > sure why we should disregard packets that are encoded using NEXT-C-SID that > omit the SRH, but let’s overlook that for now.) > > If this solution does not require any SRH data plane change, presumably it > would be true that if I take a packet that includes an SRH and place within > it a series of SIDs encoded with (for example) the REPLACE-C-SID flavor, then > that packet would be able to successfully traverse a network of routers that > support plain vanilla RFC 8754. That is, it would arrive at its first hop > router which according to a local, per-router function, would determine how > to take the datagram arriving on the router input port and forward it to (the > correct) router output port. Then that process would be repeated across the > rest of the network. > > But that is patently incorrect: when it’s delivered to the first hop, the > plain vanilla RFC 8754 router will be unable to apply the REPLACE-C-SID > behavior, and forwarding to the next hop will fail. It seems that a different > local, per-router function is required (in fact, the local, per-router > function defined in the draft) in order for the forwarding to succeed. By the > definitions I’m using here, that is exactly a data plane change. > > What, precisely, is then being claimed? > > Thanks, > > —John > _______________________________________________ > spring mailing list > spring@ietf.org > https://urldefense.com/v3/__https://www.ietf.org/mailman/listinfo/spring__;!!NEt6yMaO-gk!S7rbnYg6aV2s3cyoTCL3wwWX4bpbFoawPLt6yLeYsms82sLl9tUpRU1X5c-D9A$ _______________________________________________ spring mailing list spring@ietf.org https://www.ietf.org/mailman/listinfo/spring
