Hi, Peng
>I agreed with the following: > > "... we need to look more closely at the scenarios. I don't >>> think we have given enough thought to the nested domains case (i.e. >>> areas in ASes) given that both pd-path and brpc (largely) treat the >>> nested case as simply a flat sequence. >> >> Looking at the nested case, what would be the point of domain-scope >> since all TE-related info for the intra-area links have an area scope ?" > > I guess following the thinking line of this draft, we might need > another extension so as to advertising "inter-area" TE links into > non-backbone areas, or, just treat one area as a "domain"? Not sure if there really are inter-area TE links. Apart from the inter-AS links, all physical links exist exactly in one area for sure. > > And in Renhai's "[ZRH]I try to give an answer.", last line, how to > perform this inter-area computation? per-area? or Backward Recursive > Path Computation in a multi-area AS? Currently, there is no limitation of computation method, I think this is not what is intended to be discussed in this draft. However, this draft does provide the necessary info no matter which method is deployed. Thanks, Zhang Renhai > > Regards, > Peng > > On 2/6/07, Zhang Renhai <[EMAIL PROTECTED]> wrote: >> Hi, JP >> >> See in-line please. >> >> > Hi Adrian, >> > >> > On Feb 5, 2007, at 7:11 PM, Adrian Farrel wrote: >> > >> >> Hi Greg, >> >> >> >>> - would you agree that usually ASBRs are eBGP speakers >> >>> and are fully mesh connected. In that case eBGP can be >> >>> viable solution for the inter-AS TE links computation by >> >>> ASBR. >> >> >> >> So the question has to be: >> >> Do other nodes apart from ASBRs need this information? >> >> >> >> What about an ingress LSR trying to compute a path out of the AS? >> >> >> >> If we require that the ingress LSR always consults an external PCE >> >> that is a BGP speaker, then I guess this is fine, but most LSRs >> >> today are capable of path computation and could handle this case >> >> (for example, for the pd-path scenario) without needing to consult >> >> an external PCE. >> >> >> >>> - I'm concerned with scaling aspect of flooding inter-AS TE >> >>> information throughout both AS and an area >> >> >> >> I have this concern, too, but I wonder how many TE links we are >> >> talking about, and how this compares with the number of TE links >> >> within an area. >> >> >> > >> > It is probably negligible ... Note that by contrast with the approach >> > proposing to flooding Inter-ASBR TE LSP, we're only looking at >> > flooding the TE information of the inter-ASBR *links*. >> > >> >>> and I see that you're concerned as well (SHOULD for Type >> >>> 10 and MAY for Type 11). I think that it would be >> >>> helpful if use of both Type 10 and Type 11 for inter-AS >> >>> TE Link advertisement be illustrated by scenarios. I think >> >>> that use of area scope makes these OSPF extensions less >> >>> applicable to inter-AS path computation by the head-end >> >>> LSR/LER. >> >> >> >> Yes, that would be the case. >> > >> >> I agree that we need to look more closely at the scenarios. I don't >> >> think we have given enough thought to the nested domains case (i.e. >> >> areas in ASes) given that both pd-path and brpc (largely) treat the >> >> nested case as simply a flat sequence. >> > >> > Looking at the nested case, what would be the point of domain-scope >> > since all TE-related info for the intra-area links have an area scope ? >> [ZRH]I try to give an answer. >> With a new sub-tlv(remote AS number)and a new link type >> (inter-AS link type) are specified, in a multi-areas AS, the entry ASBR >> when receving a path mesg can get the exit ASBR(in another area) with >> this AS-scope advertisement and the path mesg(downstream AS number >> is given in ERO). then, the inter-area computation can be performed. >> >> Regards, >> Zhang Renhai >> >> > >> >> >> >>> - Could you please illustrate which links are excluded by the >> >>> following: >> >>> " Routers or PCEs that are capable of processing advertisements of >> >>> inter-AS TE links SHOULD NOT use such links to compute paths that >> >>> exit an AS to a remote ASBR and then immediately re-enter the AS. >> >>> Such paths would constitute extremely rare occurrences and MUST >> >>> only >> >>> be allowed as the result of specific policy configuration at the >> >>> router or PCE computing the path." >> >>> Are there two links that interconnect a pair of ASBRs that belong >> >>> to two >> >>> different neighboring ASes? >> >> >> >> Renhai can comment, but I assumed that this meant that two ASes are >> >> linked by more than two TE links. The LSP should not under normal >> >> circumstances leave AS1 to AS2 through TE link 1 and return to AS1 >> >> from AS2 through TE link 2. >> >> >> >> The example you give (ASBR1 in AS1 connects to ASBR2 in AS2 with >> >> two links, the LSP goes out on one and back on the other) would be >> >> detected as a loop in RSVP-TE, and would not offer any benefit anyway. >> > >> > Thanks. >> > >> > JP. >> > >> >> >> >> Regards, >> >> Adrian >> > >> > >> >> > _______________________________________________ Pce mailing list [email protected] https://www1.ietf.org/mailman/listinfo/pce
