Hi Julien, I will work with Olivier to prepare a proposed text to address the below issues in draft-ietf-pce-stateful-pce. We will post it for the authors and the WG to enhance.
Regards, Mustapha. > -----Original Message----- > From: EXT Julien Meuric [mailto:[email protected]] > Sent: Tuesday, May 03, 2016 8:32 AM > To: Aissaoui, Mustapha (Nokia - CA); [email protected] > Subject: Linking Stateful and Stateless Capabilities [Was: Whither Stateless > PCE?] > > Hi all, > > [New title to help editors of stateful I-Ds to catch up.] > > It appears that there is still some shadow on the main stateful I-D. We > should make > sure that any reader has a good understanding of what is history behavior and > what is not, without assuming incremental extensions of IETF protocols is > known- > enough to guarantee backward compatibility. > > Mustapha, if you have a couple of clarifying sentences to share, so as to > address > your concerns, that would be valuable. > > Thanks, > > Julien > > > Apr. 18, 2016 - [email protected]: > > > Hi Olivier, > > It is one option for sure. In general, > implementations of stateful > PCE should be able of caching the constraints > received in the PCReq > message for some period of time to give a chance for a > potential > follow-up PCRpt message. Even if you set the D-flag in the PCReq > > message, there is no guarantee that a PCRpt will follow and as such a > PCE > implementation will have to flush that information from its cache > at some > point in > time. > > > > In addition, I think it is worth considering sending the > constraints > in > a PCRpt message in duplicate Metric/LSPA objects with the P-flag > set. This > is in > addition to the same objects containing the > operational values. > This can be useful in the case where the initial > path was computed by the > router > and it is active and the user is > delegating it. The PCE at that point in > time will not > compute a path > immediately but will save the original constraints in the > PCRpt > > message for the next time it needs to update the path. > > > > Regards, > > > Mustapha. > > > > *From:*EXT Olivier Dugeon > [mailto:[email protected]] *Sent:* > Monday, April 18, 2016 8:58 AM > > > > > > Dear Mustapha, > > You catch a good point regarding the original > > > constraints > that are > not carry by the PCRpt message. Thus, if we used a standard PCReq > > message without the D-delegate flag set, there is a risk that the PCE > > considers > this request as a stateless one and don't keep track of the > original > request, and > consequently, original constraints. > > So, is it preferable to set de > D-delegate > flag in the PCReq message > to tell the PCE to keep in memory the original > constraints for > further usage, or, is the 'STATEFUL-PCE-CAPABILITY' TLV in > Open > message is sufficient for the PCE to know that it must keep track of > > any > requests? I prefer the first option as it allows a per request > > configuration while > the second enables the memorization globally for > all requests. > > Regards, > > > > Olivier > > Le 08/04/2016 19:26, Aissaoui, Mustapha (Nokia - CA) a écrit > : > > Hi Olivier, > > Good summary indeed. I was worried about interop testing > when I sent > the original email to the list in December 2014. > > > > > I just wanted to comment on a couple of things: > > > > 1. > You are correct that the LSP object which has the D-delegate > flag is > allowed in > the PCReq message as per > draft-ietf-pce-stateful-pce. I however think it is > more > appropriate > to do the delegation in the subsequent PCRpt message once the > LSP > path is programmed by PCC following the PCRep message from PCE. This > > is because it is at that time that the LSP is being synchronized with > the > > PCE > LSP database. > > > > > 2. The PCRpt message does not carry the original constraints > of > the LSP (Bandwidth, Metric, and LSPA objects). It can carry the > > operational > values of the Bandwidth and Metric objects used by the > last computed path in > the router. So, even if you have a PCE which > reacted to the PCRpt message > and > computed a new path, it will not get > the appropriate constraints included. > That is > why the PCReq/PCRep > sequence before delegating the LSP is needed. > > > > > Regards, > > Mustapha. > > > > *From:*EXT [email protected] > > <mailto:[email protected]> > [mailto:[email protected]] > *Sent:* Friday, April 08, 2016 > 12:29 PM > > > > Hello all, > > IMHO the > discussion must be split into is 2 different subjects: > > 1/ PCInit message > could > be seen as an independent message compared to > other PCReq/PCRep, PCRpt > and PCUp. Indeed, the PCE uses the PCInit > message after a request that comes > from another interface (e.g. a > RestConf > API) instead of PCReq that comes from the router itself > through PCEP. > In fact, when you configure a tunnel on the router, > only the path > computation part > is requested to the PCE. Complements > of tunnel configuration still remain > in the > router configuration. In > case of PCInit, all information must be provided > to the > router. This > could be for example the traffic steering. So, IMHO, it is > normal > > that the PCInit message evolves through extensions different from the > other > PCEP messages, and in particular PCReq, as it is not triggered > by the same > entity, i.e. an external component instead the PCC router > itself. > > > 2/ But, this will not make PCReq message obsolete. Indeed, RFC5440 > > will > continue to be mandatory for stateful both passive and active > mode even if > it > needs clarification in the draft. Let me explain. In > passive stateful, a > PCReq/PCRep sequence is drawn in Figure 7 of the > pce stateful draft prior to > the PCRpt message Now, the ambiguity > comes from the active stateful mode > and figure 8. Why is the > PCReq/PCRep sequence not mentioned? Of course the > tunnel is delegated > in this mode, but, the delegation object has been added > as > an > extension to the PCReq message in the same draft. So, IMHO, at the > > creation of the tunnel, the draft must precise that a PCReq/PCRep > exchange > with > delegation=1 must be used prior to the PCRpt to be > coherent with RFC > 5440 and passive stateful mode. > > The problem occured during our evaluation > of > commercial products on > which we made interoperability tests. Indeed we > observed different > behaviours that are due to the draft ambiguity and > conduct to > some > interoperability issues. The different cases are as follow: - a/ - > > PCReq/PCRep exchange to obtain a valid ERO before the PCRpt message - > b/ - > PCReq message to obtain a valid ERO but with no reaction from > the PCE which > is not conform to > RFC5440 - c/ - PCRpt with empty ERO > (looks strange. What is the meaning of > an > Empty ERO ? a loose path ? > no path ? )/PCupd to get a valid path which > overlaps with standard > RFC5440 PCReq/PCRep. - d/ - PCRpt with empty ERO > and no PCUpd leaving > the tunnel down. > > Thus, PCC/PCE that used > PCRpt/PCupd messages for active stateful mode > are incompatible with > PCC/PCE that used standard PCReq/PCrep > exchange. We could not mix both > behaviours (PCC that use PCReq > message with PCE that react to PCRpt with > empty ERO and > reciprocally). The problem occurs only at the creation of the > tunnel. > Once created and up the tunnel is reported and updated by means of > > PCRpt / PCupd messages correctly in all cases. > > To summarize: PCInit > message could leave independently from other > messages. PCReq is the basis > of PCE and is mandatory in all use cases > included the active stateful mode, > but > this need to be clarify in the > pce stateful draft. > > Regards > > Olivier > > > Le > 07/04/2016 23:22, Aissaoui, Mustapha (Nokia - CA) a écrit : > > Hi Adrian, > > > I > raised in December 2014 the technical issue in > draft-ietf-pce-stateful-pce > that a > PCC must be able to convey the > original parameters (constraints) of the LSP > path (Bandwidth, Metric, > and LSPA objects) using a PCReq message to a PCE > and subsequently > delegate the LSP to PCE using the PCRpt message. > Otherwise, when the > LSP is delegated to PCE only the operational values of > these > parameters can be included in the PCRpt message. The latter means > > that > the PCE will update the path without knowing exactly the > original > parameters. > > > > > For me, PCReq/PCRep are an integral part of operating an LSP in > stateful > mode. > > > > Here is the link to the archived thread: > > > https://mailarchive.ietf.org/arch/search/?email_list=pce&so=- > date&q=%22+Path+Computation+Request+in+Active+Stateful+PCE%22 > > > > > > Regards, > > Mustapha. > > > > *From:*Pce [mailto:pce- > [email protected]] *On Behalf Of *EXT Adrian > Farrel *Sent:* Thursday, April > 07, > 2016 12:48 AM > > > > I think you are probably right, Dhruv. > > > > But > referencing the ways in which customers deploy may be a little > limiting. > > > To > say PCE is widely deployed (even after all these years) may be an > > exaggeration. > > > Although we do have some clues about what is currently being pushed > for > deployment. > > > > I think you have mainly grasped my point, however. We > need > to > understand which extensions are definitely only needed in one mode or > > another, and which should be done in all modes (either because they > are > needed > or because we don't know). > > > > OTOH, I suppose TLVs are just TLVs. Once > you specified the TLV it is > not rocket science to include it in a message. > In fact, > it is > probably one line of text to include it and only a short paragraph to > > > describe additional processing in other modes once you have described > how it > is used in one mode. > > > > Where does that leave us? > > > > Adrian > > > > > *From:*[email protected] <mailto:[email protected]> > > [mailto:[email protected]] *On Behalf Of *Dhruv Dhody *Sent:* 06 > April > 2016 23:07 > > > > Hi Adrian, > > > > Even in the brave new world of Stateful > PCE, PCReq and PCRep messages > do play a role in the passive stateful PCE > mode. PCReq/PCRep also > play a crucial role in the inter-domain and > inter-layer > context in > the new proposal like stateful H-PCE. > > > > At the same time > mandating that every extension (say SFC) must also > be specified in a > stateless > manner when no customer deploy in such a > way, might be overkill. > > > > > Perhaps we need to look at it case by case! > > > > Dhruv > > > > On Wed, Apr > 6, > 2016 at 4:00 PM, Adrian Farrel <[email protected] > > <mailto:[email protected]>> > wrote: > > Once upon a time, in a working group far, far away, PCE was > basically > > stateless. PCE acted in response to questions asked by PCCs. > > > These days, everyone is excited by stateful PCEs and there is a lot > of > initiation (of LSPs or of control of LSPs). > > In the jabber room during > today's > meeting Ravi noted that not a lot > of the new drafts (maybe none of them) > talk > about PCReq messages. > This raises the question in our minds as to whether > stateless PCE is > obsolete. > > If (and only if) this mode of PCE usage has > gone > out of fashion, we > > *might* consider cleaning up the protocol and architecture so that we > don't > need > to make protocol extensions to PCReq and PCRep messages > when we make > extensions to PCInit messages. > > Thoughts? > > Adrian > > _______________________________________________ Pce mailing list [email protected] https://www.ietf.org/mailman/listinfo/pce
