RE: [Pce] Working Group Last Callon draft-ietf-pce-pcecp-interarea-reqs-04.txt
"LE ROUX Jean-Louis RD-CORE-LAN" <jeanlouis.leroux@orange-ftgroup.com> Fri, 29 December 2006 12:37 UTC
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Subject: RE: [Pce] Working Group Last Callon draft-ietf-pce-pcecp-interarea-reqs-04.txt
Date: Fri, 29 Dec 2006 13:37:35 +0100
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Thread-Topic: [Pce] Working Group Last Callon draft-ietf-pce-pcecp-interarea-reqs-04.txt
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From: LE ROUX Jean-Louis RD-CORE-LAN <jeanlouis.leroux@orange-ftgroup.com>
To: Dimitri.Papadimitriou@alcatel-lucent.be
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Hi Dimitri, > edit: on the SRLG comment for ensuring some level of > consistency identifiers should assigned and allocated from > the same entity - this would solve the issue mentioned Ok I'm going to submit v05 that accounts for your comments Thanks JL > -----Message d'origine----- > De : Dimitri.Papadimitriou@alcatel-lucent.be > [mailto:Dimitri.Papadimitriou@alcatel-lucent.be] > Envoyé : samedi 23 décembre 2006 00:17 > À : LE ROUX Jean-Louis RD-CORE-LAN > Cc : pce@ietf.org > Objet : RE: [Pce] Working Group Last Callon > draft-ietf-pce-pcecp-interarea-reqs-04.txt > > hi jean-louis > > i think we're converging beside one point about section 4.5 & > 4.6 as indicated here below > > edit: on the SRLG comment for ensuring some level of > consistency identifiers should assigned and allocated from > the same entity - this would solve the issue mentioned > > thanks, > - d. > > > > > > "LE ROUX Jean-Louis RD-CORE-LAN" <jeanlouis.leroux@orange-ftgroup.com> > 19/12/2006 00:48 > > To: <Dimitri.Papadimitriou@alcatel-lucent.be> > cc: pce@ietf.org > Subject: RE: [Pce] Working Group Last Callon > draft-ietf-pce-pcecp-interarea-reqs-04.txt > > > Hi Dimitri, > > Thanks for these clarifications. > > Please see in-line, > > > -----Message d'origine----- > > De : Dimitri.Papadimitriou@alcatel-lucent.be > > [mailto:Dimitri.Papadimitriou@alcatel-lucent.be] > > Envoyé : lundi 18 décembre 2006 10:25 > > À : LE ROUX Jean-Louis RD-CORE-LAN > > Cc : Dimitri.Papadimitriou@alcatel-lucent.be; JP Vasseur; > pce@ietf.org > > Objet : RE: [Pce] Working Group Last Callon > > draft-ietf-pce-pcecp-interarea-reqs-04.txt > > > > hi jean-louis > > > > see in-line for a couple of clarifications > > > > > > > > > > "LE ROUX Jean-Louis RD-CORE-LAN" > <jeanlouis.leroux@orange-ftgroup.com> > > 15/12/2006 19:29 > > > > To: <Dimitri.Papadimitriou@alcatel-lucent.be>, > > "JP Vasseur" > > <jvasseur@cisco.com> > > cc: <pce@ietf.org> > > Subject: RE: [Pce] Working Group Last Callon > > draft-ietf-pce-pcecp-interarea-reqs-04.txt > > > > > > Hi Dimitri, > > > > Sorry for this late answer. > > Thanks for your comments. > > > > Please see inline, > > > > > -----Message d'origine----- > > > De : Dimitri.Papadimitriou@alcatel.be > > > [mailto:Dimitri.Papadimitriou@alcatel.be] > > > Envoyé : mercredi 29 novembre 2006 09:35 À : JP Vasseur Cc : > > > pce@ietf.org Objet : Re: [Pce] Working Group Last Callon > > > draft-ietf-pce-pcecp-interarea-reqs-04.txt > > > > > > hi > > > > > > comment on this doc. > > > > > > 4.5. Inclusion of Area IDs in Request > > > > > > The knowledge of the areas in which the source and > > destination lie > > > would allow selection of appropriate cooperating PCEs. > > > > > > => so is there an assumption that the PCE-Area ID knowledge is > > > available - how come ? > > > > Yes this information can be made available with the discovery > > protocol, see [RFC4674] section 4.1.1.2. > > > > We can rephrase as follows: > > > > "The knowledge of the areas in which the source and destination lie > > would allow selection of appropriate cooperating PCEs. This > would be > > useful when the area ID(s) of a PCE (i.e. the area(s) where it has > > visibility) is/are known, which can be achieved by the PCE > Discovery > > Protocol (see [RFC4674]) or any other mean." > > > > > > > > A PCE may not > > > be able to determine the location of the source and > > destination and > > > in such a case it would be useful that a PCC indicates > > the source > > > and > > > destination area IDs. > > > > > > => not sure to see the reasoning - i guess the initial PCE > > referred to > > > here is an intermediate PCE that does not have any > > visibility of the > > > source/destination areas and potentially more > > > - the whole problem in this sentence is the interpretation > > of the term > > > - location - > > > > OK we can rephrase as follows > > > > "A PCE in a PCE chain, may not have any visibility of the > > source/destination area and hence may not be able to determine the > > area of the source/destination" > > > > > > > > For that purpose the request message MUST support the > > inclusion of > > > the source and destination area IDs. Note that this > information > > > could > > > be learned by the PCC through configuration. > > > > > > => how to be sure that the local area PCE is going only to be > > > contacted by local area PCC's > > > > Why do you need such assurance? > > > > [dp] because the PCC itself may be an area where PCE > learning and PCC > > learning are not identical (PCC knows less than the PCE) > > Again, we don't mandate the inclusion of source/dest area IDs > in any request. > In situations where the PCC is aware of this information this > may be useful to include it in the request. > > > > > I don't catch your point here. > > > > [dp] but this can also happen in the other way around, the issue is > > that this information is provided as helper to the PCE > looking at the > > different cases we've at hand even if this information is > provided it > > does not still guarantee that the "local PCE" will be able to > > determine the location of the destination and hence the > > next/downstream PCE > > If the request includes the destination area, then the PCE > becomes aware of it, it can then select a downstream PCE > based on advertised PCE information (PCE areas). > > > > > > > >- we're entering into a chicken > > > egg problem, from one side mandate knowledge of > source/destination > > >area > > > > We don't mandate knowledge of src/dest area. We say "the request > > message MUST support the inclusion", we don't say "MUST include" > > > > > but on the other there is no > > > guarantee about interpretation of this information before > > knowing the > > > PCC - area ID relationship > > > > > > Here we simply ask the PCECP to support the inclusion of source and > > destination area IDs in the request. > > When this information is known by the PCC (through configuration or > > any other means), then it may be included in the request > message, and > > this may facilitate selection of downstream PCEs. > > > > > > > > > > > > > 4.6. Area Inclusion/Exclusion > > > > > > In some situations it may be useful to include one or more > > > area(s) in > > > the path. > > > > > > => for inter-area it is certainly true that the actual path will > > > cross multiple areas but i wonder whether what you mean > is not the > > > request includes one or more areas to be followed by the > path to be > > > computed > > > > Yes it is, will be reworded as follows. > > > > "It may be useful that the request message indicate one or more > > area(s) that must be followed by the path to be computed. > > It may also be useful that the request message indicate one or more > > area(s) that must be avoided by the path to be computed." > > > > > > > > It may also be useful to exclude one or more area(s) from > > > the path (e.g. request for a path between LSRs in two > stub areas > > > connected to the same ABR(s), which must not cross the > backbone > > > area). Hence the request message MUST allow indicating > a set of > > > one > > > or more area(s) that must be explicitly included in > the path, and > > > a > > > set of one or more area(s) that must be explicitly > excluded from > > > the > > > path. > > > > > > => be prepared to incorporate a loop avoidance mechanism, in case > > > the request will have to cross multiple PCEs > > > > Yes a loop avoidance mechanism will be needed, > independantly of this > > area inclusion/exclusion by the way. > > I don't think this requires any specific text here. > > > > [dp] shouldn't that specific text be included in the > document, as it > > is meant to cover both PCC-PCE and PCE-PCE messaging ? > > OK, we can add the following section > > 4.9 Loop Avoidance > > In case of multiple-PCE inter-area path computation there may > be risks of PCECP request loops. > A mechanism MUST be defined to detect and supress PCECP > request message loops. This may rely, for instance, on the > recording, in the request message, of the set of traversed PCEs. > Also the returned path in a response message MUST be loop free. > > Would such a section make sense to you? > > > > > > > > > > other comments to follow > > > - d. > > > > OK, see below, > > > > > section 4.7 Inter-area Diverse Path computation > > > > > > o) wrt 6. Security Considerations "IGP areas are administrated by > > > the same entity. .." > > > > > > does the latter ensure uniqueness of the SRLG IDs ? > > > > YES > > > > [dp] in theory yes, in practice not - > > just think upon the > > > case where a > > single entity borrows fibers from two different plants each of them > > having chosen different SRLG IDs for two fibers lying in > the same duct > > - > > But when you build SRLGs for an IP network you also account > for the ducts. > By the way you can be aware of the duct that is actually > used, even if the fiber is rent (this can be provided in the > contract). > > Anyway, a requirement for SRLG diverse path computation makes > the assumption of consistent SRLGs...and there is nothing > specific to the PCE nor to the inter-area case here. > > Thanks, > > JL > > > > > > > > o) The response message MUST allow indicating the level > of diversity > > > of > > > a set of computed loose paths. > > > > > > do you mean partial disjointness ? or something equivalent ? > > > > This refers to link, node, SRLG diversity of a set of paths. > > > > We can add the following > > > > "The response message MUST allow indicating the level of > diversity of > > a set of computed inter-area loose paths (link, node, SRLG > diversity), > > globally and on a per-area basis (link, node, SRLG diversity of > > intra-area path segments). > > > > > > > > o) last sentence §3 unclear to me wrt to the next > sentence - is it > > > referring to a diversity of a given wrt to a set of resources but > > > the next sentence refers to the diversity of a given LSP wrt to a > > > set of other LSPs but also their SRLG set for inst. ? > > > > > > > It refers to the diversity of a set of paths. I agree that > this is not > > clear. > > > > Will rephrase as follows > > > > "It MUST allow indicating the required level of diversity > of a set of > > inter-area paths (link, node, SRLG diversity), as well as > the required > > level of diversity of a set of intra-area segments of inter-area > > paths(link, node, SRLG diversity) on a per-area basis. > > > > Thanks a lot for your comments Dimitri. > > Let us know if the proposed text is fine with you and we > will submit a > > new revision. > > > > Best Regards, > > > > JL > > > > > > > > > > > > > > > > > > > > > JP Vasseur <jvasseur@cisco.com> > > > 22/11/2006 15:51 > > > > > > To: pce@ietf.org > > > cc: > > > Subject: [Pce] Working Group Last Call on > > > draft-ietf-pce-pcecp-interarea-reqs-04.txt > > > > > > > > > Dear WG, > > > > > > A new revision of draft-ietf-pce-pcecp-interarea-reqs (rev > > > -04) has been posted that addresses the remaining issues/comments. > > > > > > This email initiates a Working Group Last Call on > > > draft-ietf-pce- pcecp-interarea-reqs-04.txt. The last > call will end > > > on December 8th at noon EST. > > > > > > Please send your comments to the mailing list. > > > > > > Thanks. > > > > > > JP. > > > > > > > > > _______________________________________________ > > > Pce mailing list > > > Pce@lists.ietf.org > > > https://www1.ietf.org/mailman/listinfo/pce > > > > > > > > > > > > _______________________________________________ > > > Pce mailing list > > > Pce@lists.ietf.org > > > https://www1.ietf.org/mailman/listinfo/pce > > > > > > > > > > > _______________________________________________ > Pce mailing list > Pce@lists.ietf.org > https://www1.ietf.org/mailman/listinfo/pce > > > _______________________________________________ Pce mailing list Pce@lists.ietf.org https://www1.ietf.org/mailman/listinfo/pce
- RE: [Pce] Working Group Last Callon draft-ietf-pc… LE ROUX Jean-Louis RD-CORE-LAN
- RE: [Pce] Working Group Last Callon draft-ietf-pc… Dimitri.Papadimitriou
- RE: [Pce] Working Group Last Callon draft-ietf-pc… LE ROUX Jean-Louis RD-CORE-LAN
- RE: [Pce] Working Group Last Callon draft-ietf-pc… Dimitri.Papadimitriou
- RE: [Pce] Working Group Last Callon draft-ietf-pc… LE ROUX Jean-Louis RD-CORE-LAN