Re: [conex] ConEx Dest Opt
Bob Briscoe <bob.briscoe@bt.com> Mon, 21 October 2013 18:41 UTC
Return-Path: <bob.briscoe@bt.com>
X-Original-To: conex@ietfa.amsl.com
Delivered-To: conex@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id C7EAE11E8222 for <conex@ietfa.amsl.com>; Mon, 21 Oct 2013 11:41:07 -0700 (PDT)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -3.351
X-Spam-Level:
X-Spam-Status: No, score=-3.351 tagged_above=-999 required=5 tests=[AWL=0.248, BAYES_00=-2.599, RCVD_IN_DNSWL_LOW=-1]
Received: from mail.ietf.org ([12.22.58.30]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id 3LIhabJVz2Jz for <conex@ietfa.amsl.com>; Mon, 21 Oct 2013 11:41:02 -0700 (PDT)
Received: from hubrelay-rd.bt.com (hubrelay-rd.bt.com [62.239.224.99]) by ietfa.amsl.com (Postfix) with ESMTP id DCB9B11E8235 for <conex@ietf.org>; Mon, 21 Oct 2013 11:40:54 -0700 (PDT)
Received: from EVMHR72-UKRD.domain1.systemhost.net (10.36.3.110) by EVMHR67-UKRD.bt.com (10.187.101.22) with Microsoft SMTP Server (TLS) id 8.3.297.1; Mon, 21 Oct 2013 19:40:53 +0100
Received: from EPHR02-UKIP.domain1.systemhost.net (147.149.100.81) by EVMHR72-UKRD.domain1.systemhost.net (10.36.3.110) with Microsoft SMTP Server (TLS) id 8.3.279.1; Mon, 21 Oct 2013 19:40:52 +0100
Received: from bagheera.jungle.bt.co.uk (132.146.168.158) by EPHR02-UKIP.domain1.systemhost.net (147.149.100.81) with Microsoft SMTP Server id 14.2.347.0; Mon, 21 Oct 2013 19:40:51 +0100
Received: from BTP075694.jungle.bt.co.uk ([10.111.172.154]) by bagheera.jungle.bt.co.uk (8.13.5/8.12.8) with ESMTP id r9LIeot7024405; Mon, 21 Oct 2013 19:40:50 +0100
Message-ID: <201310211840.r9LIeot7024405@bagheera.jungle.bt.co.uk>
X-Mailer: QUALCOMM Windows Eudora Version 7.1.0.9
Date: Mon, 21 Oct 2013 19:40:49 +0100
To: Mirja Kuehlewind <mirja.kuehlewind@ikr.uni-stuttgart.de>
From: Bob Briscoe <bob.briscoe@bt.com>
In-Reply-To: <201310211929.05331.mirja.kuehlewind@ikr.uni-stuttgart.de>
References: <201310191353.14159.mirja.kuehlewind@ikr.uni-stuttgart.de> <201310191602.r9JG2NjW010985@bagheera.jungle.bt.co.uk> <201310211929.05331.mirja.kuehlewind@ikr.uni-stuttgart.de>
MIME-Version: 1.0
Content-Type: text/plain; charset="iso-8859-1"; format="flowed"
Content-Transfer-Encoding: quoted-printable
X-Scanned-By: MIMEDefang 2.56 on 132.146.168.158
Cc: conex@ietf.org
Subject: Re: [conex] ConEx Dest Opt
X-BeenThere: conex@ietf.org
X-Mailman-Version: 2.1.12
Precedence: list
List-Id: Congestion Exposure working group discussion list <conex.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/conex>, <mailto:conex-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/conex>
List-Post: <mailto:conex@ietf.org>
List-Help: <mailto:conex-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/conex>, <mailto:conex-request@ietf.org?subject=subscribe>
X-List-Received-Date: Mon, 21 Oct 2013 18:41:07 -0000
Mirja, At 18:29 21/10/2013, Mirja Kuehlewind wrote: >Hi Bob, > >I cc'ed the list. > >Thanks for you reply, see comments below. > >On Saturday 19 October 2013 18:02:22 Bob Briscoe wrote: > > Mirja, > > > > Cc any reply to the list if you want. > > > > At 12:53 19/10/2013, Mirja Kühlewind wrote: > > >Hi, > > > > > >I'm currently working on the CDO draft. If have two questions where I'm > > > not sure about the right answer at the moment (independent of crediting > > > actually). Maybe someone of you already has an answer: > > > > > >1) Should ConEx marked packets preferentially not be dropped? This could > > > help the audit but it would overestimate the congestion level. > > > -> I would say no, because chances that marked packets get drop are > > > anyway lower (?) because marks are usually sent after a window reduction. > > > And this could potentially be exploited negatively...? > > > > You're thinking only in terms of what a compliant > > TCP will do, not what an attacker might do... > > > > Optionally, preferential drop should discard with > > the following drop pref (1 means drop first): > > Not-ConEx or no destopt: 1 > > X (but not L,E or C): 2 > > X and L,E or C: 3 > > > > Otherwise a DDoS source can just not re-echo > > ConEx and flood the queues before the first audit > > function without being limited by an ingress policer. > > > > There is no known way to game this - Mark > > Handley, me and others thought through this when > > we were first considering re-ECN as a mitigation of DDoS. > > > > See > > <http://tools.ietf.org/html/draft-briscoe-conex-re-ecn-tcp-02#section-5.3> > > for useful wording on preferential discard (but with re-ECN codepoints). > > > > However, this has to be OPTIONAL because it's not > > so neat to expect a queue to drop based on a > > destopt, which is meant to be e2e. We should ask > > on the list whether this is likely to be > > controversial with the IESG. I think OPTIONAL should be OK. >Okay, agree, but should this be described/discussed in the ConEx Dest Opt >document? It's the only place it can be discussed. So yes. It's experimental, so the IESG should be able to allow it through. > > > > >2) ConEx marks should be immutable. What to do or how to detect if someone > > >changed the marking on the path. > > > > You can borrow the words from the last para of > > the re-ECN Security Considerations if you want: > > <http://tools.ietf.org/html/draft-briscoe-conex-re-ecn-tcp-02#section-8.1> > > > > This would require some future modification to > > the L4 transport, so the receiver can feed back > > ConEx markings to the sender (re-re-feedback) - > > only random ones - don't need it all the time. We > > don't have to do this now, just allow for it in future. >Not sure, if I even want to mention this option in the CDO draft (or anywhere >else)...? The requirement is already stated in abstract-mech, so no need to say it elsewhere yet. If it were put anywhere, it would be in a ConEx transport spec. But there's no need to mention this even in conex-tcp-mods at this stage. It's definitely not relevant to conex-dest-opt. All you have to say there is that the field is immutable. > > > > Alternatively, an IPsec authentication header > > could be used, because the destopt would > > automatically be covered by e2e IPSec AH. > > However, the text says it's better not to reveal > > to the network whether the endpoints are > > protecting against changes to ConEx fields. > > Otherwise a network will just attack packets that > > aren't protected. it is preferable for random > > checks to tend to protect everyone, rather than > > just protecting those doing the checks. >Not sure I get your point here. If you want to >be protected, use IPSec AH, no? >I don't see a problem here. Don't worry - it's not important. It's a subtle point that there are two ways to protect yourself: - an obvious and visible way (AH) - a randomised stealth way that also has the nice effect that the network cannot see who is protected, so it doesn't risk its reputation and avoids attacks anyone, in case it attacks someone who can detect the attack. Bob > > > > >Furthermore, should invalid bit combinations > > >be ignored or should the packet get dropped or something else...? > > > -> Don't know... > > > > I think the only invalid bit combination is not-X with L,E or C. > > > > This could be solved by just not having the X > > flag. The existence of the destopt could imply > > ConEx-capable. However, that would make header overhead variable within a > > flow. > > > > Easiest to say L,E or C implies ConEx-capable, even if X is off. > > Then you have to say the packet should be > > forwarded unchanged and the inconsistency > > ignored. This would allow some future meaning to > > be assigned to L,E or C with X off. >Currently the drafts says if X is off, L, E and C are undefined. Yes, that >allows for future usage but would imply to ignore L, E or C if X is off. This >contradicts your first sentence which is saying that L, E or C implies >ConEx-capable. > >I believe I tent to leave it as it is, saying that E, L, and C should be >ignored if X is off and additionally saying explicit that no action (drop) >should be take if this case occurs. Okay? > >Mirja > > > > > > > Bob > > > > >Any ideas? > > > > > >Mirja > > > > ________________________________________________________________ > > Bob Briscoe, BT > > > >-- >------------------------------------------------------------------- >Dipl.-Ing. Mirja Kühlewind >Institute of Communication Networks and Computer Engineering (IKR) >University of Stuttgart, Germany >Pfaffenwaldring 47, D-70569 Stuttgart > >tel: +49(0)711/685-67973 >email: mirja.kuehlewind@ikr.uni-stuttgart.de >web: www.ikr.uni-stuttgart.de >------------------------------------------------------------------- ________________________________________________________________ Bob Briscoe, BT
- Re: [conex] ConEx Dest Opt Mirja Kuehlewind
- Re: [conex] ConEx Dest Opt Bob Briscoe