Re: [Dart] [tsvwg] Comments on draft-ietf-tsvwg-rtcweb-qos-00
"Bless, Roland (TM)" <roland.bless@kit.edu> Tue, 24 June 2014 08:30 UTC
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Date: Tue, 24 Jun 2014 10:30:24 +0200
From: "Bless, Roland (TM)" <roland.bless@kit.edu>
Organization: Institute of Telematics, Karlsruhe Institute of Technology
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To: "Subha Dhesikan (sdhesika)" <sdhesika@cisco.com>, "tsvwg@ietf.org" <tsvwg@ietf.org>
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Subject: Re: [Dart] [tsvwg] Comments on draft-ietf-tsvwg-rtcweb-qos-00
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Hi Subha, thanks for you reply, see comments inline: > An authorization mechanism alone is probably not sufficient, because > DS boundary nodes may need to police (e.g., remark/drop) incoming > traffic according to some agreed/negotiated traffic profile for some > of the PHBs, e.g., the EF PHB does not work properly if its traffic > class is overloaded (see below). > > SD: Agreed. The previous line states: " Therefore, the DSCP value > may be remarked at the network edge through policy to any other DSCP > value, including best effort.". There is already a mention that > apckers may be remarked or dropped and any additional mitigation is > outside the scope of this draft. Unfortunately, this doesn't address my comment. DSCP remarking by provider policy is somewhat different from having policers installed (e.g., a token bucket w/ marker and dropper) that perform traffic conditioning according to some installed traffic profile. Static remarking of DSCPs may be caused by using a different DCSP/PHB mapping or lack of DiffServ support etc. which is slightly different. > The problem with using EF is that if too many EF marked packets are > injected into a DS domain, they probably void the EF properties for > other users within this domain (background is that the service rate of > EF packets on a given output interface must exceed their arrival rate at > that interface over long and short time intervals - this is usually > checked by admission control before use and policing at DS boundary > nodes during use). Therefore, maybe some discussion w.r.t. RFC5865 > http://tools.ietf.org/html/rfc5865 may be useful. > SD: Agreed that admission control is very useful and relevant. This > draft is intended for the selection and use of the right DSCP for > webrtc media flows. There is a mention of over-subscription in the > beginning. Sure, however, my point was that simply injecting traffic marked with a DSCP for a PHB that normally requires prior admission control is somewhat problematic: either guarantees for already admitted flows are violated or such traffic has to be dropped. > If a packet enters a QoS domain that has no support for the above > defined Data Types/Application (service) classes, then the network > node at the edge will remark the DSCP value based on policies. > > Yes, but even if there is support for these classes traffic > conditioning (e.g., remarking/dropping etc.) may be necessary and > applied. Remarking to different PHBs may also lead to packet > reordering within a media flow?! >SD: Remarking/dropping may occur, which is mentioned in the draft. Same issue as above: remarking caused by a static DS domain policy (PHBx -> PHBy) is different from remarking and other actions that boundary nodes may perform for individual flows according to traffic profiles. Regards, Roland
- [Dart] Comments on draft-ietf-tsvwg-rtcweb-qos-00 Bless, Roland (TM)
- Re: [Dart] [tsvwg] Comments on draft-ietf-tsvwg-r… Subha Dhesikan (sdhesika)
- Re: [Dart] [tsvwg] Comments on draft-ietf-tsvwg-r… Bless, Roland (TM)
- Re: [Dart] [tsvwg] Comments on draft-ietf-tsvwg-r… Gorry Fairhurst
- Re: [Dart] [tsvwg] Comments on draft-ietf-tsvwg-r… Brian E Carpenter
- Re: [Dart] [tsvwg] Comments on draft-ietf-tsvwg-r… gorry