From nobody Sat Feb 5 14:59:45 2022 Return-Path: X-Original-To: tcpm@ietfa.amsl.com Delivered-To: tcpm@ietfa.amsl.com Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id CF2B43A1E83 for ; Sat, 5 Feb 2022 14:59:42 -0800 (PST) X-Virus-Scanned: amavisd-new at amsl.com X-Spam-Flag: NO X-Spam-Score: -2.675 X-Spam-Level: X-Spam-Status: No, score=-2.675 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.576, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, URIBL_BLOCKED=0.001] autolearn=ham autolearn_force=no Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (2048-bit key) header.d=apple.com 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 urNfLm9v1o03 for ; Sat, 5 Feb 2022 14:59:37 -0800 (PST) Received: from rn-mailsvcp-ppex-lapp14.apple.com (rn-mailsvcp-ppex-lapp14.rno.apple.com [17.179.253.33]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 69B683A1E82 for ; Sat, 5 Feb 2022 14:59:37 -0800 (PST) Received: from pps.filterd (rn-mailsvcp-ppex-lapp14.rno.apple.com [127.0.0.1]) by rn-mailsvcp-ppex-lapp14.rno.apple.com (8.16.1.2/8.16.1.2) with SMTP id 215MpKTL005793; Sat, 5 Feb 2022 14:59:33 -0800 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=apple.com; h=content-type : content-transfer-encoding : from : mime-version : subject : date : message-id : references : cc : in-reply-to : to; s=20180706; bh=vH9owh7pC0d4sY3hC9qrbjz6jn0qJNGu8rysPOZHFwk=; b=muNB0khFm5yYU3hDMShzzPWVjYSeSm+XjbkIgvYckPw21XmQITuDsOEjy9fzOahyDLh1 TNpIWvnsEhQct2LPPUzYKwyB9lwp7O4v4z3dva6Bcpidr/6xD/8Jpt2sng8I5w2d+OH4 b9+IHys9HhTvMXYtrpO4MxsUOcQKku7maoBQq7lxPo0MEu6y8UIpeqR5nHodCMdo8qKB grdopO8RuNrHfDp/4pJXdohHY2l1VtVCxZHyPIDsnF9gIFTpTp9AAJHSHAdy7kL9ECaL N1YfVa0n1k7wSSV7/aQLpHzbKddSx6G+9VcqKpLBIivks/EFsIi2UzZYc7CaL1sXbLdg sQ== Received: from ma-mailsvcp-mta-lapp04.corp.apple.com (ma-mailsvcp-mta-lapp04.corp.apple.com [10.226.18.136]) by rn-mailsvcp-ppex-lapp14.rno.apple.com with ESMTP id 3e1q0dntsx-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128 verify=NO); Sat, 05 Feb 2022 14:59:33 -0800 Received: from ma-mailsvcp-mmp-lapp01.apple.com (ma-mailsvcp-mmp-lapp01.apple.com [17.32.222.14]) by ma-mailsvcp-mta-lapp04.corp.apple.com (Oracle Communications Messaging Server 8.1.0.12.20210903 64bit (built Sep 3 2021)) with ESMTPS id <0R6U002CFT78C000@ma-mailsvcp-mta-lapp04.corp.apple.com>; Sat, 05 Feb 2022 14:59:32 -0800 (PST) Received: from process_milters-daemon.ma-mailsvcp-mmp-lapp01.apple.com by ma-mailsvcp-mmp-lapp01.apple.com (Oracle Communications Messaging Server 8.1.0.12.20210903 64bit (built Sep 3 2021)) id <0R6U00900SI9O900@ma-mailsvcp-mmp-lapp01.apple.com>; Sat, 05 Feb 2022 14:59:32 -0800 (PST) X-Va-A: X-Va-T-CD: 81ca60fce39c2560b6c4a7e5841f9b8f X-Va-E-CD: d27b0bf1ec5e225c315eb75773194505 X-Va-R-CD: 7f6ba7ce084ea0aad2ff4f136dfa7fc9 X-Va-CD: 0 X-Va-ID: 9a0b082f-20cb-4682-929d-fd5e1b1c4790 X-V-A: X-V-T-CD: 81ca60fce39c2560b6c4a7e5841f9b8f X-V-E-CD: d27b0bf1ec5e225c315eb75773194505 X-V-R-CD: 7f6ba7ce084ea0aad2ff4f136dfa7fc9 X-V-CD: 0 X-V-ID: 9b210405-7100-4f09-8b7c-6694241a158e X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.425, 18.0.816 definitions=2022-02-05_12:2022-02-03, 2022-02-05 signatures=0 Received: from smtpclient.apple (unknown [17.10.30.3]) by ma-mailsvcp-mmp-lapp01.apple.com (Oracle Communications Messaging Server 8.1.0.12.20210903 64bit (built Sep 3 2021)) with ESMTPSA id <0R6U00P7FT77LI00@ma-mailsvcp-mmp-lapp01.apple.com>; Sat, 05 Feb 2022 14:59:32 -0800 (PST) Content-type: text/plain; charset=utf-8 Content-transfer-encoding: quoted-printable From: Vidhi Goel MIME-version: 1.0 (1.0) Date: Sat, 05 Feb 2022 14:59:31 -0800 Message-id: References: <1cbe3dbe-241b-3f24-096f-f1a2ffe17d98@gmx.at> Cc: Richard Scheffenegger , "tcpm@ietf.org Extensions" , Mirja Kuehlewind In-reply-to: <1cbe3dbe-241b-3f24-096f-f1a2ffe17d98@gmx.at> To: "Scheffenegger, Richard" X-Mailer: iPhone Mail (19B5060d) X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.425, 18.0.816 definitions=2022-02-05_12:2022-02-03, 2022-02-05 signatures=0 Archived-At: Subject: Re: [tcpm] I-D Action: draft-ietf-tcpm-accurate-ecn-16.txt X-BeenThere: tcpm@ietf.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: TCP Maintenance and Minor Extensions Working Group List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Sat, 05 Feb 2022 22:59:43 -0000 > As a middle ground, perhaps having these descriptions in a non-normative > section, clearly stating these to be examples of what an impemented > could choose to do? This draft already covers some of the path mangling detection so it would be= good to cover all of it. I agree with your middle ground suggestion. Vidhi > On Feb 5, 2022, at 4:02 AM, Scheffenegger, Richard wrote:= >=20 > =EF=BB=BFVidhi, >=20 > Thanks for reading the draft very closely! >=20 > Well, in the non-ECT SYN case, where the SYNACK indicates an ECT (ect0, > ect1, ce) is the obvious - and fully semantically correct - use case of > that possible use. >=20 > For the set of three codepoints (ECT0, ECT1, CE) the only other possible > valid detection scenario would be if a SYN+CE is sent (deliberately, > althought one can argue that a sender should not originate CE-marked > packets), but a SYNACK without CE is returned (full or partial > bleaching). At least under the current RFC3168 definition of IP ECN > codepoints. >=20 > allowed transitions: > nonECT -> nonECT >=20 > ECT0 -> ECT0 > ECT0 -> ECT1 > ECT0 -> CE >=20 > ECT1 -> ECT1 > ECT1 -> ECT0 (possibly) > ECT1 -> CE >=20 > CE -> CE >=20 >=20 > Thinking about this aspect more, I am now unsure, if the higher level > functions, such as detection of IP ECN codepoint mangling, or validating > across multiple RTTs, should be in this document - or not rather be in a > separate draft, in order to facilitate independent implementation and > improvement of mechanisms in that space. >=20 > However, the above table of allowed IP ECN transistions may be updated > independently of AccECN - and performing extensive checks as part of a > signal protocol ossifies this IMHO. >=20 > As a middle ground, perhaps having these descriptions in a non-normative > section, clearly stating these to be examples of what an impemented > could choose to do? >=20 > Richard >=20 >> Am 05.02.2022 um 02:14 schrieb Vidhi Goel: >> I like your response for all the points. I can review the diff for the >> proposed changes, if you=E2=80=99d like before committing them to the dra= ft. >>=20 >> Sorry, I want to add a new comment for this text, >>=20 >> If a TCP client has set the SYN to Not-ECT, but >> receives feedback that the IP-ECN field on the SYN arrived with a >> different codepoint, it can detect such middlebox interference and >> send Not-ECT for the rest of the connection. >>=20 >>=20 >> This statement holds good for Not-ECT but doesn=E2=80=99t if lets say the= SYN >> was ECT0 or ECT1 as those could be marked CE and still be valid. Should >> we add a statement for ECT marked SYN as well? >>=20 >> Thanks, >> Vidhi >>=20 >>> On Feb 4, 2022, at 5:44 AM, Bob Briscoe >> > wrote: >>>=20 >>> Vidhi, >>>=20 >>> I've increased the table of contents to tocdepth =3D "4" which might >>> help find the relevant sections better, because a lot of the meat in >>> this draft is under sections 3.2.2 (ACE) and 3.2.3 (Option). >>>=20 >>> I've responded below, but I'd prefer it if you would say these things >>> on the list, so we have a better justification for changing the draft. >>> Reviewing a draft that has just be re-posted shouldn't imply anything >>> about whether Apple is implementing the draft or not. >>>=20 >>> (BTW, regarding the proposed change to the initial value of r.e1b, I >>> was going to send that to the list once co-authors agreed to it. But >>> it would be nice if some of the edits were not self-generated.) >>>=20 >>> See [BB] inline for responses (which I'll repeat if you send to the list= ). >>>=20 >>> On 04/02/2022 07:37, Vidhi Goel wrote: >>>> Hello Bob and authors, >>>>=20 >>>> I have read the draft a few times and will send my extensive review >>>> at a later point. But right now, I want to ask some critical things >>>> that an implementation could benefit from. >>>>=20 >>>> The draft says, >>>> /If a TCP client has set the SYN to Not-ECT, but/ >>>> / receives feedback that the IP-ECN field on the SYN arrived with a/ >>>> / different codepoint, it can detect such middlebox interference and/= >>>> / send Not-ECT for the rest of the connection/ >>>>=20 >>>> 1. On the forward path from client to server, the client will revert >>>> to Not-ECT when it sees for example, that it sent a Non-ECT SYN but >>>> received ACE encoding other than 0 1 0. What does the client do in >>>> the last ACK of the 3WHS - >>>> a. does it stay in AccECN mode and still send AccECN encoding based >>>> on the IP code point of SYN-ACK (Table 4)? This would mean that >>>> client won=E2=80=99t participate in ECN on the sender half of the conne= ction >>>> and only provide AccECN feedback to the server as a receiver. >>>> b. does it disable AccECN mode and set ACE=3D 0 0 0 so that a server >>>> in AccECN mode can disable ECN based on Table4? >>>>=20 >>>> While writing this, I realized that the intention is probably a. >>>> Could you confirm? Also, when the sender sets Not-ECT in its data >>>> packets, it should also disable acting upon any ACE feedback as we >>>> could still receive false ACE feedback from the server if the >>>> network, lets say, changed 00 (not ECT) to 01(ECT1). If you agree, we >>>> should add some text around this. Based on the current text, the >>>> sender will always respond to the ACE feedback even if it sends Not-ECT= . >>>>=20 >>>> TBH, this is a complicated scenario, where sender said to the network >>>> - I don=E2=80=99t trust you so I can=E2=80=99t use ECN. Feel free to dr= op my packets. >>>> And the network mangles the IP to ECT1 and then set CE (when >>>> congested) which would be feedback=E2=80=99ed from the receiver. Now, t= he >>>> packet wasn=E2=80=99t dropped which it should have been. So, is it bett= er to >>>> just ignore this feedback because sender doesn=E2=80=99t trust the netw= ork or >>>> just act on it and reduce cwnd in order to reduce congestion in the >>>> network somewhere. >>>=20 >>> [BB] Your points are all good ones. >>> I'll address this last complex scenario first, because it has >>> implications for the earlier questions. First I'll define some >>> terminology: >>>=20 >>> Simple mangling scenario: >>>=20 >>> * some network function, e.g. broken Diffserv ToS-byte remarking, >>> illegally remarks a Not-ECT SYN to CE. >>>=20 >>> Your complex mangling scenario, repeated here: >>>=20 >>> * some network function, e.g. broken Diffserv ToS-byte remarking, >>> illegally remarks a Not-ECT SYN to ECT0 or ECT1, >>> * then congestion at a subsequent bottleneck is marking some packets CE= >>>=20 >>> Then potentially the client could tailor its behaviour after sending a >>> Not-ECT SYN, If the SYN/ACK feedback is >>>=20 >>> 1. ECT: disable sending ECT, but continue responding to ECN feedback >>> 2. CE, disable sending ECT, and disable response to ECN feedback >>>=20 >>> However, this is uncertain, because CE feedback on the SYN/ACK could >>> indicate either the simple or the complex mangling scenario. >>>=20 >>> A simpler alternative would be to always continue responding to ECN >>> feedback. Rationale: >>>=20 >>> * Whether case #1 or #2, assume that mangling of the SYN might have >>> been Not-ECT to ECT, even if the feedback off the SYN is CE. >>> * Then as the connection progresses, if /all/ feedback is CE, >>> there's already a recommendation to fall-back to disabling >>> congestion response. >>>=20 >>> If we do this, I think we ought to say "SHOULD continue to respond to >>> ECN feedback", not "MUST". >>>=20 >>> And we'll need to put this all to the WG. >>>=20 >>> 1.a) Now back to the beginning of your point. The text you quote is >>> from =C2=A72.5 which is in the non-normative "Overview and Rationale" >>> section (=C2=A72). >>> You really need the normative text from: >>>=20 >>>=20 >>> 3.2.2.3. >>> Testing >>> for Mangling of the IP/ECN Field >>> >>>=20 >>>=20 >>> where it says (end of 1st para): >>>=20 >>> " ...for the remainder of the connection the client MUST NOT send >>> ECN-capable packets, but it MUST continue to feed back any ECN >>> markings on arriving packets." >>>=20 >>> So, you're right, the answer is (a). >>> It can't be (b), because, once in AccECN mode, 000 on the ACE field >>> just becomes a counter value, and no longer negotiates the feedback mode= . >>>=20 >>> 1.b) As per the above, let's conservatively assume complex mangling. >>> So, at the end of the first para quoted above I suggest we add: >>>=20 >>> " ...for the remainder of the connection the client MUST NOT send >>> ECN-capable packets *but**it**SHOULD continue to respond to ECN >>> feedback even though **it **is no longer sending ECN-capable >>> packets (see reasoning below)**. T**he client**MUST remain in the >>> same feedback mode and***it MUST continue to feed back any ECN >>> markings on arriving packets." >>>=20 >>> I'll do the same for next para about the server. >>> I'll work out some text for the reasoning, but I won't give it here. >>>=20 >>> There are two other cases where it disables sending ECT, which don't >>> say whether it continues to respond to congestion: >>>=20 >>> * "Testing for Mangling" section, penultimate para, where it's >>> receiving solid CE: >>> "Once a Data Sender has entered AccECN mode it SHOULD check >>> whether all feedback received for the first three or four rounds >>> indicated that every packet it sent was CE-marked. If so, for the >>> remainder of the connection, the Data Sender SHOULD NOT send >>> ECN-capable packets*and it SHOULD NOT respond to ECN feedback*, >>> but *it MUST remain in the same feedback mode and *it MUST >>> continue to feed back any ECN markings on arriving packets*(in its >>> role as Data Receiver)*." >>> * Next section "Zeroing of the ACE Field", 2nd para: >>> "If the value of this ACE field is zero (0b000), the Data Sender >>> disables sending ECN-capable packets for the remainder of the >>> half-connection by setting the IP/ECN field in all subsequent >>> packets to Not-ECT, *but**it**SHOULD continue to respond to ECN >>> feedback even though **it **is no longer sending ECN-capable >>> packets.* *It MUST also remain in the same feedback mode and it >>> MUST continue to feed back any ECN markings on arriving packets >>> (in its role as Data Receiver).*" >>>=20 >>> I'll also add reasoning (in the zeroing section, it already says that >>> ACE=3D0b000 is not an unambiguous indication of mangling). >>>=20 >>> And this prompts me to edit the bullet in an earlier section about the >>> obligation of a sender to respond to congestion feedback: >>>=20 >>>=20 >>> 3.1.5. >>> Implications >>> of AccECN Mode >>> >>>=20 >>>=20 >>> "It is still obliged to respond appropriately to AccECN feedback >>> that indicates there were ECN marks on *ECN-capable *packets it >>> had previously sent." >>>=20 >>> And I'll add a bullet: >>>=20 >>> "*If the sender chooses not to send ECN-capable packets (e.g. >>> because path traversal of the ECN field is suspect), it can ignore >>> any **ECN **feedback about those packets if it is certain that it >>> cannot be valid (see Section 3.2.2, which gives normative >>> requirements for certain specific cases).*" >>>=20 >>> I've said 'can' rather than 'MUST' because it's hard to cover all >>> cases, e.g. single packets without ECT when it's not clear whether the >>> feedback covered another packet that was ECT. >>>=20 >>> How does all this sound? >>>=20 >>>> 2. On the reverse path from server to client, if a server sends a >>>> Not-ECT SYN-ACK and receives ACE handshake encoding on last ACK other >>>> than 0 1 0, there is no text like above that says server should send >>>> Not-ECT for the rest of the connection (or at least I didn=E2=80=99t fi= nd >>>> it). I think the server should also do same as client as the two >>>> paths could be different. One could make it more complicated by >>>> saying, if both client and server decide to not use ECN on their >>>> corresponding sender half, then ECN should be disabled but let=E2=80=99= s talk >>>> about that later. >>>=20 >>> [BB] It's in the second para of: >>>=20 >>>=20 >>> 3.2.2.3. >>> Testing >>> for Mangling of the IP/ECN Field >>> >>>=20 >>>=20 >>>> 3. In general, not setting the ECT (ECT0 or ECT1) code point on an >>>> outgoing packet is different from supporting AccECN right as in the >>>> host can still provide AccECN feedback on the receive path. >>>=20 >>> [BB] Yup. >>>=20 >>> Do you think any further explanation is needed in the above sections? >>>=20 >>>=20 >>> Bob >>>=20 >>>> =E2=80=A6. >>>>=20 >>>> To be continued if more questions come to my mind. >>>>=20 >>>>=20 >>>> Thanks, >>>> Vidhi >>>>=20 >>>>> On Feb 3, 2022, at 7:24 AM, Bob Briscoe wrote: >>>>>=20 >>>>> tcpm folks, >>>>>=20 >>>>> This rev to accurate-ecn is the first of two. The second will >>>>> hopefully follow on its heels in the next couple of days. >>>>>=20 >>>>> Diffs between this first rev (-16) and -15: >>>>>=20 >>>>> 1. switches round two fairly large sections, so I've deferred other >>>>> changes to a second rev so the diffs won't be masked by the switch >>>>> round of sections. >>>>> Suggested by Ilpo to match the order in which the tests in these >>>>> sections will be executed: >>>>> * Test for mangling the IP-ECN field (now 3.2.2.3), >>>>> * Then test for zeroing the ACE field (now 3.2.2.4). >>>>>=20 >>>>> 2. Ilpo suggested some clarifications in "3.2.3.2.5. Consistency >>>>> between AccECN Feedback Fields", which is about the receiver of >>>>> feedback ensuring consistency between the mandatory 3-bit ACE field >>>>> and the optional 24-bit counters. In brief (paraphrasing) it >>>>> previously only said "MUST consider both fields", when it is now >>>>> clearer that it actually meant "MUST reconcile both fields", so that >>>>> there is always a consistent baseline for subsequent ACKs. >>>>>=20 >>>>> 3. A minor point is added in an appendix about the details that the >>>>> pseudocode doesn't cover. >>>>>=20 >>>>>=20 >>>>>=20 >>>>> Bob >>>>>=20 >>>>> PS. #2 & #3 were added to the XML ages ago (Jul '21), so you will >>>>> have seen them in the HTML. However, prob due to my clumsiness, the >>>>> posted TXT didn't include them whereas the posted XML did (ironic >>>>> for a section about consistency). In turn, inconsistency was only >>>>> possible because I am having to manually post the TXT for this >>>>> draft, due to an unresolved issue with v3 RFC XML tables. >>>>>=20 >>>>>=20 >>>>> On 03/02/2022 14:43, internet-drafts@ietf.org wrote: >>>>>> A New Internet-Draft is available from the on-line Internet-Drafts >>>>>> directories. >>>>>> This draft is a work item of the TCP Maintenance and Minor >>>>>> Extensions WG of the IETF. >>>>>>=20 >>>>>> Title : More Accurate ECN Feedback in TCP >>>>>> Authors : Bob Briscoe >>>>>> Mirja K=C3=BChlewind >>>>>> Richard Scheffenegger >>>>>> Filename : draft-ietf-tcpm-accurate-ecn-16.txt >>>>>> Pages : 60 >>>>>> Date : 2022-02-03 >>>>>>=20 >>>>>> Abstract: >>>>>> Explicit Congestion Notification (ECN) is a mechanism where networ= k >>>>>> nodes can mark IP packets instead of dropping them to indicate >>>>>> incipient congestion to the end-points. Receivers with an ECN- >>>>>> capable transport protocol feed back this information to the sende= r. >>>>>> ECN was originally specified for TCP in such a way that only one >>>>>> feedback signal can be transmitted per Round-Trip Time (RTT). >>>>>> Recent >>>>>> new TCP mechanisms like Congestion Exposure (ConEx), Data Center T= CP >>>>>> (DCTCP) or Low Latency Low Loss Scalable Throughput (L4S) need mor= e >>>>>> accurate ECN feedback information whenever more than one marking i= s >>>>>> received in one RTT. This document specifies a scheme to provide >>>>>> more than one feedback signal per RTT in the TCP header. Given TC= P >>>>>> header space is scarce, it allocates a reserved header bit >>>>>> previously >>>>>> assigned to the ECN-Nonce. It also overloads the two existing ECN= >>>>>> flags in the TCP header. The resulting extra space is exploited t= o >>>>>> feed back the IP-ECN field received during the 3-way handshake as >>>>>> well. Supplementary feedback information can optionally be provid= ed >>>>>> in a new TCP option, which is never used on the TCP SYN. The >>>>>> document also specifies the treatment of this updated TCP wire >>>>>> protocol by middleboxes. >>>>>>=20 >>>>>>=20 >>>>>> The IETF datatracker status page for this draft is: >>>>>> https://datatracker.ietf.org/doc/draft-ietf-tcpm-accurate-ecn/ >>>>>>=20 >>>>>> There is also an htmlized version available at: >>>>>> https://datatracker.ietf.org/doc/html/draft-ietf-tcpm-accurate-ecn-16= >>>>>>=20 >>>>>> A diff from the previous version is available at: >>>>>> https://www.ietf.org/rfcdiff?url2=3Ddraft-ietf-tcpm-accurate-ecn-16 >>>>>>=20 >>>>>>=20 >>>>>> Internet-Drafts are also available by rsync at rsync.ietf.org >>>>>> ::internet-drafts >>>>>>=20 >>>>>>=20 >>>>>> _______________________________________________ >>>>>> tcpm mailing list >>>>>> tcpm@ietf.org >>>>>> https://www.ietf.org/mailman/listinfo/tcpm >>>>>=20 >>>>> -- >>>>> ________________________________________________________________ >>>>> Bob Briscoe http://bobbriscoe.net/ >>>>>=20 >>>>> _______________________________________________ >>>>> tcpm mailing list >>>>> tcpm@ietf.org >>>>> https://www.ietf.org/mailman/listinfo/tcpm >>>>=20 >>>=20 >>> -- >>> ________________________________________________________________ >>> Bob Briscoehttp://bobbriscoe.net/ >>=20 >>=20 >> _______________________________________________ >> tcpm mailing list >> tcpm@ietf.org >> https://www.ietf.org/mailman/listinfo/tcpm