Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-behaviour-08
"David Harrington" <ietfdbh@comcast.net> Fri, 13 January 2012 23:30 UTC
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From: David Harrington <ietfdbh@comcast.net>
To: 'Tom Taylor' <tom111.taylor@bell.net>, "'Joel M. Halpern'" <jmh@joelhalpern.com>
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Date: Fri, 13 Jan 2012 18:30:01 -0500
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Cc: gen-art@ietf.org, draft-ietf-pcn-sm-edge-behaviour@tools.ietf.org, 'Steven Blake' <slblake@petri-meat.com>
Subject: Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-behaviour-08
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Hi Tom, If you change this to Experimental, then the Intro should have a discussion of the experiment, including some guidance about how to judge success. The current IESG has been a stickler on that point. dbh > -----Original Message----- > From: Tom Taylor [mailto:tom111.taylor@bell.net] > Sent: Sunday, January 01, 2012 2:49 PM > To: Joel M. Halpern > Cc: Mary Barnes; gen-art@ietf.org; Steven Blake; David > Harrington; draft-ietf-pcn-sm-edge-behaviour@tools.ietf.org > Subject: Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-behaviour-08 > > Thanks for the review, Joel. Comments below, marked with [PTT]. > > On 31/12/2011 4:50 PM, Joel M. Halpern wrote: > > I am the assigned Gen-ART reviewer for this draft. For background on > > Gen-ART, please see the FAQ at > > <http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>. > > > > Please resolve these comments along with any other Last > Call comments > > you may receive. > > > > Document: draft-ietf-pcn-sm-edge-behaviour-08 > > PCN Boundary Node Behaviour for the Single Marking (SM) Mode of > > Operation > > Reviewer: Joel M. Halpern > > Review Date: 31-Dec-2011 > > IETF LC End Date: 13-Jan-2012 > > IESG Telechat date: N/A > > > > Summary: This documents is almost ready for publication as an > > Informational RFC. > > > > Question: Given that the document defines a complex set of > behaviors, > > which are mandatory for compliant systems, it seems that > this ought to > > be Experimental rather than Informational. It describes > something that > > could, in theory, later become standards track. > > [PTT] OK, we've wobbled on this one, but we can follow your > suggestion. > > > > Major issues: > > Section 2 on Assumed Core Network Behavior for SM, in the > third bullet, > > states that the PCN-domain satisfies the conditions specified in RFC > > 5696. Unfortunately, look at RFC 5696 I can not tell what conditions > > these are. Is this supposed to be a reference to RFC 5559 > instead? No > > matter which document it is referencing, please be more > specific about > > which section / conditions are meant. > > [PTT] You are right that RFC 5696 isn't relevant. It's such a > long time > since that text was written that I can't recall what the > intention was. > My inclination at the moment is simply to delete the bullet. > > > > It would have been helpful if the early part of the > document indicated > > that the edge node information about how to determine > > ingress-egress-aggregates was described in section 5. > > In conjunction with that, section 5.1.2, third paragraph, seems to > > describe an option which does not seem to quite work. After > describing > > how to use tunneling, and how to work with signaling, the > text refers to > > inferring the ingress-egress-aggregate from the routing > information. In > > the presence of multiple equal-cost domain exits (which > does occur in > > reality), the routing table is not sufficient information > to make this > > determination. Unless I am very confused (which does > happen) this seems > > to be a serious hole in the specification. > > [PTT] I'm not sure what the issue is here. As I understand > it, operators > don't assign packets randomly to a given path in the presence of > alternatives -- they choose one based on values in the packet header. > The basic intent is that packets of a given microflow all follow the > same path, to prevent unnecessary reordering and minimize jitter. The > implication is that filters can be defined at the ingress nodes to > identify the packets in a given ingress-egress-aggregate > (i.e. flowing > from a specific ingress node to a specific egress node) based > on their > header contents. The filters to do the same job at egress nodes are a > different problem, but they are not affected by ECMP. > > > > Minor issues: > > Section 3.3.1 states that the "block" decision occurs when the CLE > > (excess over total) rate exceeds the configured limit. > However, section > > 3.3.2 states that the decision node must take further stapes if the > > excess rate is non-zero in further reports. Is this inconsistency > > deliberate? If so, please explain. If not, please fix. (If it is > > important to drive the excess rate to 0, then why is action only > > initiated when the ratio is above a configured value, > rather than any > > non-zero value? I can conceive of various reasons. But none > are stated.) > > [PTT] We aren't driving the excess rate to zero, but to a > value equal to > something less than (U - 1)/U. (The "something less" is because of > packet dropping at interior nodes.) The assumption is that (U > - 1)/U is > greater than CLE-limit. Conceptually, PCN uses two > thresholds. When the > CLE is below the first threshold, new flows are admitted. Above that > threshold, they are blocked. When the CLE is above the second > threshold, > flows are terminated to bring them down to that threshold. In the SM > mode of operation, the first threshold is specified directly on a > per-link basis by the value CLE-limit. The second threshold > is specified > by the same value (U - 1)/U for all links. With the CL mode > of operation > the second threshold is also specified directly for each link. > > > > > > Nits/editorial comments: > > > > >
- [Gen-art] Review: draft-ietf-pcn-sm-edge-behaviou… Joel M. Halpern
- [Gen-art] A *new* batch of IETF LC reviews - 2011… Mary Barnes
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Tom Taylor
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Joel M. Halpern
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Tom Taylor
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Joel M. Halpern
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Tom Taylor
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Michael Menth
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Joel M. Halpern
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Michael Menth
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Joel M. Halpern
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… David Harrington
- [Gen-art] Review: draft-ietf-pcn-sm-edge-behaviou… Joel M. Halpern
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Russ Housley
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Joel M. Halpern
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Tom Taylor
- Re: [Gen-art] Review: draft-ietf-pcn-sm-edge-beha… Tom Taylor
- [Gen-art] Gen-Art review of draft-ietf-sipcore-rf… Alexey Melnikov
- Re: [Gen-art] Gen-Art review of draft-ietf-sipcor… Adam Roach
- Re: [Gen-art] Gen-Art review of draft-ietf-sipcor… Alexey Melnikov