Joel, There is no such thing as a Transit SID.
The functions that can be associated with a SID are described in section 4. All these functions are Endpoints functions, whose processing is only triggered by having the destination S registered as a local SID at node N. Section 5 describes the transit behaviours. These behaviours -which are not segments-, are behaviours on transit routers that neither inspect the SRH nor process it. Section 5.1 references RFC8200 on the fact that transit routers MUST NOT inspect or process the SRH. Sections 5.2-5.7 define the transit behaviours that allow steering any incoming traffic into an SR policy. As an example, section 5.4 defines T.Encaps, which states a transit router can steer incoming traffic into an SR policy. As a result, the incoming packet is encapsulated into a new IPv6 header an SRH containing the SIDs of the SR policy. (further details in 5.4). This behavior is triggered based on a local policy -i.e. it is not an SR SID what triggers T.Encaps-. In your example of section 5.2, this is exactly the same. The T.Insert behavior is triggered based on a local policy. B2 is not an SRv6 SID. Thanks, Pablo. On 17/07/2018, 08:00, "Joel M. Halpern" <[email protected]> wrote: I have read the text you quote. That text, which should as you say cause no SR processing in node N, is the exact text which introduces %.1 and 5.2. 5.2 for example is all about node N inserting a new SRH based on a Transit SID B2. WHich is not a local address of N nor a SID of N. I have no idea what SID in section 5 is a Transit SID, or how it can actually trigger the desired behavior in nodes which, as you say, ignore the SID. I presume that the transit SID has to actually be associated with the node N. But the texxt does not tell me how. Yours, Joel On 7/17/18 7:24 AM, Pablo Camarillo (pcamaril) wrote: > Hi Joel, > > Thank you for posting your question on the mailer. > > I believe you have missed the second part of that same sentence: > > As per [RFC8200], if a node N receives a packet (A, S2)(S3, S2, S1; > > SL=2) and S2 is neither a local address nor a local SID of N *then N* > > * forwards the packet without inspecting the SRH*. > > Cheers, > > Pablo > > On 16/07/2018, 14:45, "spring on behalf of Joel M. Halpern" > <[email protected] on behalf of [email protected]> wrote: > > To ampilfy my question, the text in section 5.1 reads: > > if a node N receives a packet (A, S2)(S3, S2, S1; > > SL=2) and S2 is neither a local address nor a local SID of N > > Which clearly reads as describing a case which according to the > segment > > routing header (and the 8200 rules) where the neither the SID nor the > > SRH will be processed by node N. > > Yours, > > Joel > > _______________________________________________ > > spring mailing list > > [email protected] > > https://www.ietf.org/mailman/listinfo/spring > _______________________________________________ spring mailing list [email protected] https://www.ietf.org/mailman/listinfo/spring
