Re: [manet] Magnus Westerlund's Discuss on draft-ietf-manet-dlep-pause-extension-06: (with DISCUSS)
Lou Berger <lberger@labn.net> Mon, 06 May 2019 10:49 UTC
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To: Magnus Westerlund <magnus.westerlund@ericsson.com>, "Ratliff, Stanley" <sratliff@idirect.net>, The IESG <iesg@ietf.org>
Cc: "draft-ietf-manet-dlep-pause-extension@ietf.org" <draft-ietf-manet-dlep-pause-extension@ietf.org>, "manet@ietf.org" <manet@ietf.org>, Bob Briscoe <ietf@bobbriscoe.net>, "manet-chairs@ietf.org" <manet-chairs@ietf.org>
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From: Lou Berger <lberger@labn.net>
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Date: Mon, 06 May 2019 06:49:13 -0400
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Subject: Re: [manet] Magnus Westerlund's Discuss on draft-ietf-manet-dlep-pause-extension-06: (with DISCUSS)
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Thanks Magnus. I'll upload a rev with the change today (was waiting on AD/Shepherd, but now assume they will ask for the upload)... Lou On 5/6/2019 3:56 AM, Magnus Westerlund wrote: > Thanks Lou, > > I think that clarifies my issue. I will clear with the assumption that > you will include this. > > Thanks > > Magnus > > On 2019-05-06 02:40, Lou Berger wrote: >> Hi Magnus/Bob, >> I've updated the intro to try to address your points, while also trying >> to bring in Stan's point, : >> >> The base DLEP specification does not include any data plane flow >> control capability. The extension defined in this document supports >> flow control of data traffic based on explicit messages sent via DLEP >> by a modem to indicate when a router should hold off sending traffic, >> and when it should resume. This functionality parallels the flow >> control mechanism found in PPP over Ethernet (PPPoE) per [RFC5578]. >> The extension also optionally supports DSCP (differentiated services >> codepoint) aware flow control for use by DiffServ-aware modems. (For >> general background on Differentiated Services see [RFC2475].) This >> functionality is very similar to that provided by Ethernet Priority >> flow control, see [IEEE.802.1Q_2014]. The extension defined in this >> document is referred to as "Control Plane Based Pause". Other flow >> control methods are possible with DLEP, e.g., see >> [I-D.ietf-manet-dlep-da-credit-extension] and >> [I-D.ietf-manet-dlep-credit-flow-control]. >> >> Please let me/us know what you think. >> >> Lou >> >> >> On 4/11/19 8:12 AM, Magnus Westerlund wrote: >>> Hi, >>> >>> I don't have a text proposal. I think if you work with Bob to detail out >>> the use case and >>> clarifications on the limitations with the protocol that should solve my >>> issue here. >>> >>> Cheers >>> >>> Magnus >>> >>> On 2019-04-11 13:47, Lou Berger wrote: >>>> Magnus, >>>> >>>> On 4/5/2019 5:11 AM, Magnus Westerlund wrote: >>>>> Hi, >>>>> >>>>> Thanks for the replies. >>>>> >>>>> I think the main point here is if one should treat router + modem as one >>>>> common queue when it comes to meeting PHBs or treat them as two in >>>>> sequence queues. If one treat them as two queues then you get the same >>>>> behavior as two routers in sequence. And that is acceptable from one >>>>> angle, but it also results in additional jitter and latencies. >>>> I think Stan's response already covered the above. From my perspective, >>>> I agree with stan that a modem that reports DSCPs should be expected to >>>> honor them like any other transit IP device (router, middlebox, etc.). >>>> I think that the following is possible in the non-diffserv modem aware >>>> case - but another approach would be to not deploy such limited modems >>>> in a network that requires DSCP support - just like you wouldn't deploy >>>> a router that doesn't support a particular PHB in network that expects >>>> to support it. >>>> >>>>> If we take the Expedited Forwarding PHB (RFC 3246) treating this as two >>>>> queue results in that the error is E_a1 (router) + E_a2 (mode) rather >>>>> than a E_a for the combined queue. The question is if E_a actually will >>>>> be smaller than E_a1+E_a2 when one uses this type of control? In the >>>>> combined case if the modem queue is so shallow that E_a2 << E_a1 as well >>>>> as that time for performing the DLEP signalling is so short that the >>>>> main variations ends up being in the router queue where one can apply >>>>> suitable policies to control queue load to prevent violation of the >>>>> targets. >>>>> I think my main concern will be what happens if one attempts to >>>>> implement L4S dual queues or DETNET and have DLEP in the path. Will this >>>>> require additional extensions to provide more detailed flow control >>>>> information so that lower latency or more deterministic behavior can be >>>>> achieved? >>>> Quite likely -- I think this is not the flow control you'd want with >>>> DetNet (I can't speak to L4S), i'd personally use something like what's >>>> covered in ietf-manet-dlep-da-credit-extension. >>>> >>>> >>>>> I noticed that TSVART reviewer Bob Briscoe asked for a use case >>>>> description of the case when the main queue is pushed to the router. I >>>>> think that appears to be a good idea. I think what I am wondering is if >>>>> there need to be some applicability statement here due the limitations >>>>> of the technology? >>>> I certainly have no objection to such, particularly given >>>> ietf-manet-dlep-da-credit-extension. If you have any suggested text, >>>> that would be helpful. Otherwise, as I mentioned in response to Bob, if >>>> really needed I can work with the Shepherd/WG on some applicability text. >>>> >>>> Lou >>>> >>>>> Cheers >>>>> >>>>> Magnus >>>>> >>>>>
- [manet] Magnus Westerlund's Discuss on draft-ietf… Magnus Westerlund via Datatracker
- Re: [manet] Magnus Westerlund's Discuss on draft-… Lou Berger
- Re: [manet] Magnus Westerlund's Discuss on draft-… Ratliff, Stanley
- Re: [manet] Magnus Westerlund's Discuss on draft-… Magnus Westerlund
- Re: [manet] Magnus Westerlund's Discuss on draft-… Lou Berger
- Re: [manet] Magnus Westerlund's Discuss on draft-… Magnus Westerlund
- Re: [manet] Magnus Westerlund's Discuss on draft-… Lou Berger
- Re: [manet] Magnus Westerlund's Discuss on draft-… Magnus Westerlund
- Re: [manet] Magnus Westerlund's Discuss on draft-… Lou Berger
- Re: [manet] Magnus Westerlund's Discuss on draft-… Ratliff, Stanley