Re: [tcpm] Further comments on draft-ietf-tcpm-accurate-ecn

Bob Briscoe <ietf@bobbriscoe.net> Tue, 17 July 2018 12:42 UTC

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To: "Scharf, Michael (Nokia - DE/Stuttgart)" <michael.scharf@nokia.com>, "draft-ietf-tcpm-accurate-ecn@ietf.org" <draft-ietf-tcpm-accurate-ecn@ietf.org>, "tcpm@ietf.org" <tcpm@ietf.org>
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From: Bob Briscoe <ietf@bobbriscoe.net>
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Subject: Re: [tcpm] Further comments on draft-ietf-tcpm-accurate-ecn
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Michael,

I've written the proposed edits into a local copy of draft-08, which 
we'll post after this IETF.

Wile writing the last point, I thought it best to add an extra sentence.

    It is RECOMMENDED that the AccECN protocol is implemented along with

    the experimental ECN++ protocol [I-D.ietf-tcpm-generalized-ecn 
<https://tools.ietf.org/html/draft-ietf-tcpm-accurate-ecn-07#ref-I-D.ietf-tcpm-generalized-ecn>].
    [I-D.ietf-tcpm-generalized-ecn] is a proposed alternative to another
    experimental scheme [RFC5562] so there is no need to implement RFC
    5562 along with AccECN.



Bob

On 17/07/18 01:05, Scharf, Michael (Nokia - DE/Stuttgart) wrote:
>
> This would for for me.
>
> Thanks
>
> Michael
>
> *From:*Bob Briscoe [mailto:ietf@bobbriscoe.net]
> *Sent:* Tuesday, July 17, 2018 1:34 AM
> *To:* Scharf, Michael (Nokia - DE/Stuttgart) 
> <michael.scharf@nokia.com>om>; draft-ietf-tcpm-accurate-ecn@ietf.org; 
> tcpm@ietf.org
> *Subject:* Re: [tcpm] Further comments on draft-ietf-tcpm-accurate-ecn
>
> Michael,
>
> On 15/07/18 16:54, Scharf, Michael (Nokia - DE/Stuttgart) wrote:
>
>     Hi all,
>
>     While reading draft-ietf-tcpm-accurate-ecn-07, I noticed the following:
>
>     Section 1. Introduction
>
>         It is likely (but not required) that the AccECN protocol will be
>
>         implemented along with the following experimental additions to the
>
>         TCP-ECN protocol: ECN-capable TCP control packets and retransmissions
>
>         [I-D.ietf-tcpm-generalized-ecn], which includes the ECN-capable SYN/
>
>         ACK experiment [RFC5562]; and testing receiver non-compliance
>
>         [I-D.moncaster-tcpm-rcv-cheat].
>
>     [ms] I have commented on this section before. And I still dislike the term "likely". To me, "likely" is speculation. A neutral phrasing would be "... it is possible..." or "... it is useful...". Having said this, I observe that draft-moncaster-tcpm-rcv-cheat-03 was last updated in 2014. How "likely" is it that the AccECN protocol will be implemented along with a mechanism documented in an ID that has been written more than 10 years ago and not been updated for about 4 years? Are implementers indeed so interested in draft-moncaster-tcpm-rcv-cheat that an implementation is "likely"?
>
>
> I agree. For ECN++, I think something like your suggestion of 
> "useful", or even RECOMMENDED is what is needed here. I think the 
> testing receiver compliance one could be removed from the intro. It's 
> mentioned under testing for unexpected interference and under 
> integrity checking, which are sufficient.
>
> Also, this makes me notice that the word "includes" is wrong. ECN++ 
> intends to obsolete RFC5562, but I don't think we need to mention that 
> here (cos it might change before ECN++ gets published).
>
> CURRENT TEXT:
>
>     It is likely (but not required) that the AccECN protocol will be
>     implemented along with the following experimental additions to the
>     TCP-ECN protocol: ECN-capable TCP control packets and retransmissions
>     [I-D.ietf-tcpm-generalized-ecn 
> <https://tools.ietf.org/html/draft-ietf-tcpm-accurate-ecn-07#ref-I-D.ietf-tcpm-generalized-ecn>], which includes the ECN-capable SYN/
>     ACK experiment [RFC5562 <https://tools.ietf.org/html/rfc5562>]; and testing receiver non-compliance
>     [I-D.moncaster-tcpm-rcv-cheat 
> <https://tools.ietf.org/html/draft-ietf-tcpm-accurate-ecn-07#ref-I-D.moncaster-tcpm-rcv-cheat>].
>
> PROPOSED TEXT:
>
>     It is RECOMMENDED that the AccECN protocol is implemented along with
>     the experimental ECN++ protocol [I-D.ietf-tcpm-generalized-ecn 
> <https://tools.ietf.org/html/draft-ietf-tcpm-accurate-ecn-07#ref-I-D.ietf-tcpm-generalized-ecn>].
>
>
>
>     Section 2.1.  Capability Negotiation
>
>         
>
>         The TCP server sends the AccECN
>
>         Option on the SYN/ACK and the client sends it on the first ACK to
>
>         test whether the network path forwards the option correctly.
>
>     [ms] According to Section 3.2.6, options are RECOMMENDED. While Section 2 is not normative, the whole Section 2 does not really describe well the actual requirements regarding options. This paragraph in Section 2.1 is one example for that. It would make sense to be more explicit in Section 2 to which extent options have to be supported.
>
> OK, we need to review section 2, to ensure it is consistent with 
> changes that have been made in the normative section 3 since it was 
> written.
>
> In this particular case, we already promised to check (offlist with an 
> implementer) that there was no text that contradicted the optionality 
> of the option stated at the end of Section 3.2.6.
>
> I have already started this with a list I prepared (also offlist) of 
> which middlebox checking sections an implementer could ignore if they 
> were only reading but not sending the TCP options.
>
>
>
>
> Bob
>
>
>
> -- 
> ________________________________________________________________
> Bob Briscoehttp://bobbriscoe.net/

-- 
________________________________________________________________
Bob Briscoe                               http://bobbriscoe.net/