RE: [bmwg] Comments for OSPF Convergence Benchmarking Terminology
"Manral, Vishwas" <VishwasM@netplane.com> Tue, 11 March 2003 16:13 UTC
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From: "Manral, Vishwas" <VishwasM@netplane.com>
To: 'Scott Poretsky' <sporetsky@avici.com>, Russ White <riw@cisco.com>
Cc: bmwg@ietf.org
Subject: RE: [bmwg] Comments for OSPF Convergence Benchmarking Terminology
Date: Tue, 11 Mar 2003 11:15:55 -0500
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Hi Scott, Sorry to budge in, but I would like to comment on this. We initially had only a white-box test for SPF capculations, which used show commands(which are readily available in most routers). However as in the working group we use black-box measurements, we added another test to measure the SPF time thru black-box methods(which is the same test as in the paper I have referred to in previous mails). In the 53rd meeting of IETF in MNP, it was decided(if I understood it right) that we keep the test more from the perspective of actually checking white-box measurements against the actual black-box measurements. We have used both these methods in our measurements, and have left both the methods in the draft. Thanks, Vishwas -----Original Message----- From: Scott Poretsky [mailto:sporetsky@avici.com] Sent: Tuesday, March 11, 2003 9:08 PM To: Russ White Cc: bmwg@ietf.org Subject: Re: [bmwg] Comments for OSPF Convergence Benchmarking Terminology Kevin, I thought BMWG drafts are not permitted to have White Box test coverage. Is this correct? I also thought that existing terminology should either be excluded or referenced in the Existing Terms section. Is this correct? Scott At 06:24 PM 3/10/03 -0500, Russ White wrote: > > Internal Measurements - This is a redefinition of White Box measurement. > > Recommend it be removed. > >The definition is not the major point of this defintion, but rather the >discussion about internal measurements, that they can impact the >performance of the box being measured, etc. I don't know if there is a >"generic" draft which covers these sorts of things, or if one is planned, >but it could go there just as well as here. In the meantime, it seems like >a useful discussion to have on paper. > > > External Measurements - This is a redefinition of Black Box measurement. > > Recommend it be removed. In the Discussion section for External > > Measurements it states: "when a downstream device receives complete > > routing information from the DUT, it can be inferred that the DUT has > > transmitted all of the routing information available". How can tests be > > built so that it is not "inferred", but instead "known"? > >You can't do more than infer, in most cases. You can state that it is >"known" that the DUT has finished sending information, but you don't know >if you are going to, for instance, drop the last ack, and force the DUT to >retransmit. > > > Multi-Device Measurement - This is a definition describing a test with > > multiple DUTs. This term serves no purpose. In fact, it does not even > > appear in the companion methodology. Recommend it be removed. > >Actually, in our definition, a multi-device test requires measurement of >the test results on several devices, not necessarily several DUTs. For >instance, you may need to measure the timestamp on both the route generator >and the DUT, which means it's a multi-device mesasurement (not a >multi-device test, which would imply something different). I don't argue >that we didn't use the term in the methodology, but we certainly described >some multi-device measurements in some of the tests. > >Again, the discussion is important here, in how some of these issues >surrounding multi-device measurements. > > > Point-to-Point Link - Term was already defined by the Point-to-Point > > Protocol Working Group. See RFC 1171, The Point-to-Point Protocol for > > the Transmission of Multi-Protocol Datagrams over Point-to-Point Links. > > Recommend it be removed. > >First, the concept of a point-to-point link encompasses more link types >that the PPP working group covers. For instance, there is a draft in the >IS-IS and OSPF working groups which discusses point-to-point ethernet >links, and how these protocols should treat these links different than a >normal ethernet link. In this case, I'm not certain the duplicate defintion >is a bad thing, an the discussion about convergence times in OSPF vis-a-vis >point-to-point links needs a home. > > > Broadcast Link - While this term is not defined, but frequently used, in > > IETF documents, it is a well-known term defined in IEEE 802 documents. > > Recommend it be removed. > >Note the definition is in terms of OSPF, and the benchmark draft. Again, it >may be a commonly known term, but the concept of a DR being elected on the >link is something which is specific to OSPF. > > > SPF Time - This is a white box parameter that is not externally > > observable. RFC 2328 already defines SPF. Recommend it be removed. > >There are tests included which discuss how to measure SPF time from outside >the box, and inside the box. I'm fairly certain the methodology draft >includes white box measurements, so I'm not certain why white box >measurements shouldn't be included in the terminology draft? > > > Hello Interval - This is a term already defined in RFC 2328, OSPFv2, > > Section 9, The Interface Data Structure and its use described in detail > > RFC 2328, OSPFv2, in Section 9.5, Sending Hello Packets and Section 10 > > Neighbor Data Structure. Recommend it be removed. > >The discussion here is just as important as the definition, and applies to >all tests discussed in the methodology draft. Suggestions on where else we >would put this discussion? > > > Router Dead Interval - This is a term already defined in RFC 2328, > > OSPFv2, Section 9, The Interface Data Structure and its use described in > > detail RFC 2328, OSPFv2, Section 10 Neighbor Data Structure. Recommend > > it be removed. > >See above, on hello interval. > > > Incremental-SPF - This is a white box component of OSPF. Implementation > > of this feature is optional. Superior Convergence times can be obtained > > without Incremental-SPF (as two vendors have demonstrated). Black box > > measurements cannot indicate if Incremental-SPF is internally implemented > > in the DUT. RFC 2328 makes one reference to Incremental-SPF as an > > example algorithm to improve SPF run-time. It does not require it nor > > indicate it to be the _most_ efficient algorithm. If we were to > > standardize internal SPF execution algorithms then we should also include > > PRC, RTC, and others. There would be no reason to choose just > > Incremental-SPF. Recommend it be removed. > >I don't see it used in either draft, so this is fine. > > > Convergence - Measured by Time to Flood, Run SPF, and Update RIB. This > > is a partial measurement of router components that contribute to > > Convergence time. Time to update FIB is certainly a missing component. > > Also, network operators speak of "Convergence" as the time it takes for > > all nodes in the network to converge. I propose that this term be > > renamed "Protocol Convergence" or "Control-Plane Convergence". > >Either way is fine with me.... Of course, this definition draft only sets >the meaning of words for the accompanying methods and applicability drafts, >and not in general. Others have defined convergence differently, so.... I >suppose that we, as a working group, can go one of two directions on this: > >-- We come up with a new name for convergence, prepending it with some >other word, to imply different things in different places. This could >probably lead to large and protracted arguments, and perhaps >overspecification of the meaning of words. > >(for instance, we've already added "SR" to the front of convergence for a >similar objection, so now we'll have: > >-- SR-CP-Convergence, Single Router Control Plane >-- N-CP-Convergence, Network Control Plane >-- SR-DP-Convergence, Single Router Data Plane >-- N-DP-Convergence, Network Data Plane > >as a base set of variants, with, I assume, many many more to come). > >-- We allow each draft to use the word "convergence" within it's bounding >limits (the dictionary definition), and just make certain that each draft >discusses its definition of convergence at some point, to clarify for the >readers of that draft. always remembering to have a flexible mind, and seek >out the meaning of convergence before reading any given BMWG draft. > >I'll defer to the working group for that discussion and decsion, though I >prefer the latter. > > > 2. Measuring Traffic Convergence Section > > Three measurements are listed. Here are the concerns: > > A. LSA Propagation > > B. SPF Execution - This is a White Box Measurement > >A test is included in the methods draft, so I'm not certain why this >shouldn't be here? > > > C. RIB Update - How can this be measured in isolation from 1 and 2 > > without it being a white-box test? > >We don't include a test for this, so whether it is white box or black box >makes no difference? It's just noted as a part of overal convergence times, >to be complete in the discussion of the elements of convergence time. > > > 3. Type of Network Events Section > > Next-Hop change (e.g. due to metric change) is a unique event because no > > packet loss is expected, so this should also be listed. The other events > > listed - Link Up/Down, Session Initialization, and Adjacency Down > > produce packet loss. > >We didn't discuss packet loss in any section, since we are concerned with >contorl plane convergence, rather than data plane convergence (?). We can >add next-hop change, although I'm not certain we base any tests on it, and >making this list exhasutive would, well, unless we want to do that as a >generic document, we probably don't want to go there. :-) > > > 4. LSA and Destination Mix > > No new terminology. Methodology related information. Recommend move to > > methodology document. > >This could also be moved to the applicability document, but we tried to >move these sorts of discussions outside either one of those docs, since >they didn't seem to match the flow of the documents themselves. I don't >know, actually, where we would put them in the methdology draft--it would >have to either go in the front, in a general considerations section of some >type, or it would have to go in the individual tests, repeated as needed, >or at the end, where it likely wouldn't get read. > >I'll defer to the working group on this one--I see no compelling reason to >move them or to leave them. > > > 5. Tree Shape and SPF algorithm > > These are White Box items. Neither is externally observable. Tree shape > > is already described in RFC 2328. I recommend that this section be > > removed. It could be added as an appendix to the methodology document, but > > that is not worth it since it is already covered in RFC 2328. > >First, I'm not certain where we are defining these drafts as black box >only? We refer to a paper on black box measurements, but I don't think >this methodology draft is confined to black box measurements. There are >specific warnings in various discussions about using white box >measurements, and the problems you can have with them. > >Second, the concept of tree depth and tree breadth might be considered in >RFC2328, but I'm not certain it's not worth discussing it again, from the >point of view of the impact the shape of the topology you feed to the >routers can have on the test results. > >As for where it should be, again, I see no reason to move it or not move >it.... I'll defer to the chair and the rest of the working group on this >one. > >:-) > >Russ > _______________________________________________ bmwg mailing list bmwg@ietf.org https://www1.ietf.org/mailman/listinfo/bmwg
- [bmwg] Comments for OSPF Convergence Benchmarking… Scott Poretsky
- Re: [bmwg] Comments for OSPF Convergence Benchmar… Russ White
- Re: [bmwg] Comments for OSPF Convergence Benchmar… Scott Poretsky
- RE: [bmwg] Comments for OSPF Convergence Benchmar… Manral, Vishwas
- Re: [bmwg] Comments for OSPF Convergence Benchmar… Kevin Dubray
- Re: [bmwg] Comments for OSPF Convergence Benchmar… Russ White
- Re: [bmwg] Comments for OSPF Convergence Benchmar… Kevin Dubray
- Re: [bmwg] Comments for OSPF Convergence Benchmar… Russ White
- Re: [bmwg] Comments for OSPF Convergence Benchmar… David Newman
- Re: [bmwg] Comments for OSPF Convergence Benchmar… Russ White