The MPLS WG Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] TR : I-D ACTION:draft-ietf-tewg-interarea-mpls-te-req-00.txt
hi jp, see in-line: > Thanks for your useful comments here. See below, > > At 02:18 PM 3/30/2004 +0200, Dimitri.Papadimitriou@alcatel.be wrote: > >> hi jl, here below several comments on this updated version of the >> document: >> >> 1) section 5.3.1 mentions: >> >> "The solution MUST entirely preserve the concept of IGP hierarchy. In >> other words, flooding of TE link information across areas MUST be >> precluded." >> >> section 5.3.2 mentions: >> >> "The solution MUST also not increase IGP load which could compromise >> IGP scalability. In particular, a solution satisfying those >> requirements MUST not require for the IGP to carry some unreasonable >> amount of extra information and MUST not unreasonably increase the >> IGP flooding frequency." >> >> but section 7.12 tells: >> >> "The discovery mechanism SHOULD >> be applicable across multiple IGP areas, and SHOULD not impact the >> IGP scalability, provided that IGP extensions are used for such a >> discovery mechanism." >> >> -> would it be possible to align these requirements, i get the >> impression (please confirm) that you preclude TE link information but >> you would allow for node information (auto-mesh) ? note also that the >> section 7.12 doesn't tell us a lot about the expected distribution of >> the mesh > > > The solution MUST preclude to flood TE-related link information and MUST > not compromise the IGP scalability in any circumstances. That being > said, IGP based mechanisms can be used for the discovery which will > respect the requirement mentioned above, i understand to what you're referring, but please make it clear imho it would help if in section 7.12 the exact meaning of the following "*some* discovery mechanisms" was detailed so that the reader can more accurately assess the scope of the above >> 2) section 7.3 >> >> " In the context of this requirement document, an optimal path is >> defined as the shortest path across multiple areas taking into >> account either the IGP or TE metric. " >> >> are you referring here to >> <http://www.ietf.org/internet-drafts/draft-ietf-tewg-te-metric-igp-02.txt> >> >> >> would you clarify ? > > > Sure, we will add some text. The reason for this clarification is that > there are a multitude of definitions for an optimal path: paths that > minimize the max link utilization, call set up failure, ... here we just > refer to the ability to compute a shortest path (using either the IGP or > TE metric). ok >> 3) section 7.3 >> >> it is not clear for me what is behind the last part of the following >> sentence >> >> "So a solution should support both mechanisms, and SHOULD allow >> the operator to select by configuration, and on a per-LSP basis, the >> required level of optimality. " >> >> what is meant by "level of optimality" ? is it simply "optimal - >> sub-optimal" or do you have something else in mind ? > > > We will clarify. The idea is that the ability to compute an end to end > shortest path may not be required for all inter-area TE LSPs. Hence the > solution should allow the operator to select the appropriate path > computation method. ok, would be interesting to see whether operators would like to have selection based on the computational method (allow for intermediate computation or any other option suitable in this context) or based on the optimality level (then the solution itself selects the appropriate computational method) or simply both >> 4) section 7.4 >> >> "Another example is the requirement to set up multiple TE LSPs between >> a pair of LSRs residing in different IGP areas in case a single TE >> LSP satisfying the set of requirements could not be found. " >> >> why in such a case diversity would be desirable ? > > > for either path protection or load balancing while minimizing the impact > in case of failure. > >> got the impression that if a single path would have been feasible it >> would have been selected in this case - isn't it ? > > > That being said, we need to rephrase, I agree with you that this > paragraph is not clear. It should read: > > "Another example is the requirement to set up multiple TE LSPs between a > pair of LSRs residing in different IGP areas. For instance, this would > occur if TE LSP satisfying for instance the bandwidth requirement could > be found, hence, requiring to set up multiple TE LSPs" the former point(s) seem clearer, is it "could be found" or "could not be found" ? >> 5) section 7.7 >> >> "This may reduce the recovery delay, but with the risk of >> multiple crankbacks, and sub-optimality. " >> >> i agree, but this is valid iff the head-end has initially computed an >> end-to-end optimal path, > > > more exactly this applies to contiguous LSP. For sub-optimality this > applies to any kind of LSP. well i think that a contiguous LSP can still be sub-optimal hence i would suggest to not implicitly attach the crankback functionality to the signaling method, but to make clear what are the potential issues in terms of optimality as said "iff the path was initially computed as an end-to-end optimal" >> also unclear if you refer also here to the provisioning delay ? >> >> editorially speaking it is also a bit unclear why you've splitted >> section 7.7 and section 7.8 both refers to inter-area lsp recovery i don't know if this could be taken into account, this would simplify reading and subsequent utilisation of the document >> 6) section 7.11 >> >> would it be possible to mention what's expected (or not expected) in >> terms also of hard preemption ? > > > ok just a hint here, is my understanding correct that the following sentence "The lower priority LSP is not torn down and can continue to forward traffic on a best-effort basis." infers that you would have to priority high/low only so i'd would instead be more generic here in terms of priorities >> 7) section 8.2 >> >> what's meant by stability ? ie stability of what ? (for instance, as i >> read the document, but please correct me, stability and >> re-optimization are imho two features that are going in somehow >> opposite directions so a trade-off has to be found here) > > > We will clarify. ok > thanks for your comments ! hope to see the next version soon, would also be interesting to see other people commenting here thanks, - dimitri. > JP. > >> thanks in advance, >> - dimitri. >> >> LE ROUX Jean-Louis FTRD/DAC/LAN wrote: >> >>> Hi all, >>> Thanks in advance for your comments on this new revision of inter-area >>> TE requirements. >>> Regards, >>> JL >>> >>>> A New Internet-Draft is available from the on-line Internet-Drafts >>>> directories. This draft is a work item of the Internet Traffic >>>> Engineering Working Group of the IETF. >>>> >>>> Title : Requirements for Inter-area MPLS Traffic >>> >>> Engineering >>> >>>> Author(s) : J. Le Roux, et al. >>>> Filename : draft-ietf-tewg-interarea-mpls-te-req-00.txt >>>> Pages : 20 >>>> Date : 2004-3-26 >>>> >>>> This document lists a detailed set of functional requirements for the >>>> support of inter-area MPLS Traffic Engineering (inter-area MPLS TE) >>>> which could serve as a guideline to develop the required set of >>>> protocol extensions. >>>> >>>> A URL for this Internet-Draft is: >>>> http://www.ietf.org/internet-drafts/draft-ietf-tewg-interarea-mpls-te-r >>> >>> eq-00.txt >>> >>>> To remove yourself from the IETF Announcement list, send a message to >>>> ietf-announce-request with the word unsubscribe in the body of the >>>> message. >>>> >>>> Internet-Drafts are also available by anonymous FTP. Login with the >>>> username "anonymous" and a password of your e-mail address. After >>>> logging in, type "cd internet-drafts" and then >>>> "get draft-ietf-tewg-interarea-mpls-te-req-00.txt". >>>> >>>> A list of Internet-Drafts directories can be found in >>>> http://www.ietf.org/shadow.html or >>>> ftp://ftp.ietf.org/ietf/1shadow-sites.txt >>> >>> >> >> -- >> Papadimitriou Dimitri >> E-mail : dimitri.papadimitriou@alcatel.be >> E-mail : dpapadimitriou@psg.com >> Webpage: http://psg.com/~dpapadimitriou/ >> Address: Fr. Wellesplein 1, B-2018 Antwerpen, Belgium >> Phone : +32 3 240-8491 >> >> > -- Papadimitriou Dimitri E-mail : dimitri.papadimitriou@alcatel.be E-mail : dpapadimitriou@psg.com Webpage: http://psg.com/~dpapadimitriou/ Address: Fr. Wellesplein 1, B-2018 Antwerpen, Belgium Phone : +32 3 240-8491
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