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
