[Dart] AF - DSCPs, PHBs and remarking

"Black, David" <david.black@emc.com> Mon, 16 June 2014 21:58 UTC

Return-Path: <david.black@emc.com>
X-Original-To: dart@ietfa.amsl.com
Delivered-To: dart@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id 9C0F51A0286 for <dart@ietfa.amsl.com>; Mon, 16 Jun 2014 14:58:36 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.752
X-Spam-Level:
X-Spam-Status: No, score=-2.752 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, J_CHICKENPOX_21=0.6, RCVD_IN_DNSWL_LOW=-0.7, RP_MATCHES_RCVD=-0.651, SPF_PASS=-0.001] autolearn=ham
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id nC2JhZ8O4XjE for <dart@ietfa.amsl.com>; Mon, 16 Jun 2014 14:58:32 -0700 (PDT)
Received: from mailuogwhop.emc.com (mailuogwhop.emc.com [168.159.213.141]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 43ECF1A0278 for <dart@ietf.org>; Mon, 16 Jun 2014 14:58:31 -0700 (PDT)
Received: from maildlpprd05.lss.emc.com (maildlpprd05.lss.emc.com [10.253.24.37]) by mailuogwprd03.lss.emc.com (Sentrion-MTA-4.3.0/Sentrion-MTA-4.3.0) with ESMTP id s5GLwUkF032286 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Mon, 16 Jun 2014 17:58:30 -0400
X-DKIM: OpenDKIM Filter v2.4.3 mailuogwprd03.lss.emc.com s5GLwUkF032286
DKIM-Signature: v=1; a=rsa-sha1; c=relaxed/relaxed; d=emc.com; s=jan2013; t=1402955910; bh=JygJz1agOHYrCRRD9JAalQJ40eU=; h=From:To:CC:Date:Subject:Message-ID:Content-Type: Content-Transfer-Encoding:MIME-Version; b=W0nQWJv0ZaZYrL4s3PfOErz/PEkPsg9v9fn3PEWlwjK/LqKdGUXdeMNZhS423/nTI WwR4XCmdSR0GNJorGwSTMB/0HR9k5NNHCxu6/FB6ca4a/sA/dCI3nyHqJiEhPLZtTp U04GGDzoS3rjR8Wjyk/0YeOryY64ZHs+4B8BvnYM=
X-DKIM: OpenDKIM Filter v2.4.3 mailuogwprd03.lss.emc.com s5GLwUkF032286
Received: from mailusrhubprd52.lss.emc.com (mailusrhubprd52.lss.emc.com [10.106.48.25]) by maildlpprd05.lss.emc.com (RSA Interceptor); Mon, 16 Jun 2014 17:58:11 -0400
Received: from mxhub38.corp.emc.com (mxhub38.corp.emc.com [128.222.70.105]) by mailusrhubprd52.lss.emc.com (Sentrion-MTA-4.3.0/Sentrion-MTA-4.3.0) with ESMTP id s5GLwANv021633 (version=TLSv1/SSLv3 cipher=AES128-SHA bits=128 verify=FAIL); Mon, 16 Jun 2014 17:58:10 -0400
Received: from mx15a.corp.emc.com ([169.254.1.248]) by mxhub38.corp.emc.com ([128.222.70.105]) with mapi; Mon, 16 Jun 2014 17:58:10 -0400
From: "Black, David" <david.black@emc.com>
To: "Ruediger.Geib@telekom.de" <Ruediger.Geib@telekom.de>
Date: Mon, 16 Jun 2014 17:58:09 -0400
Thread-Topic: AF - DSCPs, PHBs and remarking
Thread-Index: Ac+Jrg91Wx6GNA7VR2CrgHbx5skqHw==
Message-ID: <8D3D17ACE214DC429325B2B98F3AE712076FF26B09@MX15A.corp.emc.com>
Accept-Language: en-US
Content-Language: en-US
X-MS-Has-Attach:
X-MS-TNEF-Correlator:
acceptlanguage: en-US
Content-Type: text/plain; charset="iso-8859-1"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
X-Sentrion-Hostname: mailusrhubprd52.lss.emc.com
X-RSA-Classifications: public
Archived-At: http://mailarchive.ietf.org/arch/msg/dart/i4Teb521A8AttwLfaBdwu2i0KCs
Cc: "dart@ietf.org" <dart@ietf.org>
Subject: [Dart] AF - DSCPs, PHBs and remarking
X-BeenThere: dart@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: "\"DiffServ Applied to RTP Transports discussion list\"" <dart.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/dart>, <mailto:dart-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/dart/>
List-Post: <mailto:dart@ietf.org>
List-Help: <mailto:dart-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/dart>, <mailto:dart-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 16 Jun 2014 21:58:36 -0000

Hi Ruediger,

> Incoming AF4n -> outgoing AF4 with a cost of 1 local PHB is (for example):
> 
> Incoming DSCP 100 010 -> outgoing DSCP 100 010    PHB AF41
> Incoming DSCP 100 100 -> outgoing DSCP 100 010    PHB AF41
> Incoming DSCP 100 110 -> outgoing DSCP 100 010    PHB AF41
>
> The other option, with a cost of 3 local PHBs is
> 
> Incoming DSCP 100 010 -> outgoing DSCP 100 010    PHB AF41
> Incoming DSCP 100 100 -> outgoing DSCP 100 100    PHB AF42
> Incoming DSCP 100 110 -> outgoing DSCP 100 110    PHB AF43

Well, what ought to happen (based on the original design of AF)
is neither 1-1 PHB mapping nor classification by only the first
three bits of the DSCP, as the latter approach would also run
CS4 (DSCP 100 000) through the same queue as AF4x.

The desired treatment is to classify by DSCP, but put inbound
traffic with three DSCPs for AF4x into one queue preserving
packet order.  The DiffServ term for this set of traffic that
uses the three AF4x PHBs (with a DSCP for each) is "ordered
aggregate" - see Section 5 of RFC 3260.

After initial classification has separated out the ordered
aggregate, it can be run through an AF remarker in order to
condition the outbound proportions of AF41/42/43 to match
some desired distribution.  For examples of AF remarkers
that can be used for this purpose, see RFC 2697 and RFC 2698.

Thanks,
--David


> -----Original Message-----
> From: Dart [mailto:dart-bounces@ietf.org] On Behalf Of
> Ruediger.Geib@telekom.de
> Sent: Monday, June 16, 2014 2:54 AM
> To: Black, David
> Cc: dart@ietf.org
> Subject: Re: [Dart] Commentary on draft-york-00
> 
> Hi David,
> 
> to make sure we mean the same thing on AF, re-marking and PHB consumption:
> 
> If a network provider just supports aggregated classes and that provider must
> use DSCP based classification then
> 
> Incoming AF4n -> outgoing AF4 with a cost of 1 local PHB is (for example):
> 
> Incoming DSCP 100 010 -> outgoing DSCP 100 010    PHB AF41
> Incoming DSCP 100 100 -> outgoing DSCP 100 010    PHB AF41
> Incoming DSCP 100 110 -> outgoing DSCP 100 010    PHB AF41
> 
> The other option, with a cost of 3 local PHBs is
> 
> Incoming DSCP 100 010 -> outgoing DSCP 100 010    PHB AF41
> Incoming DSCP 100 100 -> outgoing DSCP 100 100    PHB AF42
> Incoming DSCP 100 110 -> outgoing DSCP 100 110    PHB AF43
> 
> If there was an additional possibility to classify based on
> DSCP bits 0-2, the second option can be configured with a cost
> of 1 local PHB (results in an aggregate / single local PHB for
> the provider and 3 DSCPs for an application or a device closer
> to the network edge).
> 
> Regards,
> 
> Ruediger
> 
> -----Ursprüngliche Nachricht-----
> Von: Black, David [mailto:david.black@emc.com]
> Gesendet: Freitag, 13. Juni 2014 15:24
> An: Geib, Rüdiger
> Cc: dart@ietf.org
> Betreff: RE: [Dart] Commentary on draft-york-00
> 
> Hi Ruediger
> 
> Many thanks for the additional information.  I have a few comments:
> 
> > - there used to be a possibility to ignore the lower DSCP
> >   bits 3-6, but there's no standard to that. Some vendors
> >   removed this option and with IPv6, each PHB must be
> >   classified and completely configured individually by DSCP.
> 
> That's a good thing, since that behavior (per DSCP traffic
> handling) is a core element of the DiffServ architecture, and is required by
> RFC 2474 (Section 3).
> 
> >   Please be aware, if it comes to a re-write, a single DSCP
> >   is set for all incoming DSCPs matching this PHB. Keep in
> >   mind the possible restrictions on the number of PHBs.
> 
> Full AF support should classify all 3 PHBs that make up an AF class into a
> single aggregate on the node, with remarking applied to that aggregate, not
> DSCP by DSCP.
> 
> > If end-to-end DiffServ PHBs are what you look for, standardize what is
> > really required and be clear on how to use it.
> 
> As noted earlier, that's not the goal of the dart WG, as I understand it.  I
> believe the goal of this short term WG is to describe what exists and provide
> guidance on how to use it, particularly for RTCWEB.
> 
> Thanks,
> --David
> 
> 
> > -----Original Message-----
> > From: Ruediger.Geib@telekom.de [mailto:Ruediger.Geib@telekom.de]
> > Sent: Friday, June 13, 2014 4:05 AM
> > To: Black, David
> > Cc: dart@ietf.org
> > Subject: AW: [Dart] Commentary on draft-york-00
> >
> > Hi David,
> >
> > to answer the question related to implementations and configurations
> > at least from the viewpoint of one network provider
> >
> > - you can support a multi-vendor strategy. This makes sense
> >   from an economical point of view, but limits
> >   deployments to the minimum common denominator.
> >
> > - to configure a PHB, there are classifiers, policers,
> >   schedulers, AQM and re-markers.
> >   Implementations differ to some aspects (e.g. on
> >   supported number of classes and ingress/egress remarking).
> >   Limits like less than 20 PHBs may apply today.
> >   I'd be interested, whether there are offers of any
> >   complete AF class as part of a single product.
> >
> > - there used to be a possibility to ignore the lower DSCP
> >   bits 3-6, but there's no standard to that. Some vendors
> >   removed this option and with IPv6, each PHB must be
> >   classified and completely configured individually by DSCP.
> >   Please be aware, if it comes to a re-write, a single DSCP
> >   is set for all incoming DSCPs matching this PHB. Keep in
> >   mind the possible restrictions on the number of PHBs.
> >
> > - many IP/MPLS backbone networks and also many Ethernet
> >   based access networks support 3-4 PHBs for retail services.
> >   I'm not aware of any two providers using exactly the
> >   same DSCPs. I'm also not aware of any two standards using fully
> >   matching DSCPs for their PHBs (IETF, GSMA, MEF).
> >
> > - There's something I'd call enterprise philosophy, that is
> >   making use of a large set of internal PHBs. I never saw
> >   any of these philosophies remotely resembling the other.
> >   PHBs or classes are used to identify products,
> >   access types, stream types and so on. These usually just
> >   consume PHBs with sometimes at best loose relation to
> >   standards.
> >
> > If end-to-end DiffServ PHBs are what you look for, standardise what is
> > really required and be clear on how to use it. If a network provider
> > is expected to support these PHBs, there must be a convincing reason
> > to do so. Take EF as an example for a well specified DiffServ standard.
> >
> > Regards,
> >
> > Ruediger
> >
> > -----Ursprüngliche Nachricht-----
> > Von: Dart [mailto:dart-bounces@ietf.org] Im Auftrag von Black, David
> > Gesendet: Freitag, 13. Juni 2014 07:43
> > An: Harald Alvestrand; dart@ietf.org
> > Betreff: Re: [Dart] Commentary on draft-york-00
> >
> >    Harald,
> >
> >    Many thanks for the review and commentary, especially for the discussion
> >    of real time traffic sensitivity to reordering.  This note is an attempt
> >    to pick up non-editorial items that haven't been dealt with in other
> >    messages on the list. I see four of them:
> >
> > RG: [snip]
> >
> >    [4]
> >    > 2.4 DSCP remarking
> >    >
> >    > The discussion of token-bucket-based remarkers leaves me a bit
> confused.
> >    > To me, it's obvious (?) that token-bucket-based remarkers would
> >    > operate in color-blind mode on a network boundary, and in
> >    > color-sensitive mode only when they had assurance that incoming
> >    > markings were already indicating color. Thus, flows from an end-user
> >    > system should only hit color-blind remarkers; the real question is:
> >    > will a color-blind remarker use the incoming DSCP codepoint to decide
> >    > which of a group of remarking treatments it chooses for the packets?
> >
> >    I'm not sure about the "obvious" point - anyone care to comment on what's
> >    actually deployed/configured in practice?
> >
> >    The answer to the final question about choice of remarking treatment is
> >    "yes" although the PHBs in an AF class should receive the same treatment.
> >    The fact that the question was asked suggests that the discussion of
> >    traffic classifiers needs some additional clarity and explanation.
> >
> >    Thanks,
> >    --David
> >
> 
> _______________________________________________
> Dart mailing list
> Dart@ietf.org
> https://www.ietf.org/mailman/listinfo/dart