Re: [tsvwg] Last Call: <draft-ietf-tsvwg-rfc5405bis-13.txt> (UDP Usage Guidelines) to Best Current Practice

Ca By <cb.list6@gmail.com> Fri, 03 June 2016 15:15 UTC

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Date: Fri, 3 Jun 2016 08:15:33 -0700
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Subject: Re: [tsvwg] Last Call: <draft-ietf-tsvwg-rfc5405bis-13.txt> (UDP Usage Guidelines) to Best Current Practice
From: Ca By <cb.list6@gmail.com>
To: Brian Trammell <ietf@trammell.ch>
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On Thursday, June 2, 2016, Brian Trammell <ietf@trammell.ch> wrote:

> Greetings, all,
>
> Apologies for the late last call comment; I have only one, relatively
> minor. I hope it's still useful.
>
> I understand that Section 3 was written to encourage application
> developers not to roll their own transports ("trust us when we say this is
> hard, this document is a list of reasons why") but as written it would seem
> to discourage transport innovation atop UDP (e.g. QUIC, the RTCWEB data
> channel, anything-over-PLUS), which I very much hope was not the intent.
> The problematic recommendation is in the second paragraph:
>
>    These mechanisms are difficult to implement correctly.  For most
>    applications, the use of one of the existing IETF transport protocols
>    is the simplest method of acquiring the required mechanisms.  Doing
>    so also avoids issues that protocols using a new IP protocol number
>    face when being deployed over the Internet, where middleboxes that
>    only support TCP and UDP are not rare.  Consequently, the RECOMMENDED
>    alternative to the UDP usage described in the remainder of this
>    section is the use of an IETF transport protocol such as TCP
>    [RFC0793], Stream Control Transmission Protocol (SCTP) [RFC4960], and
>    SCTP Partial Reliability Extension (SCTP-PR) [RFC3758], or Datagram
>    Congestion Control Protocol (DCCP) [RFC4340] with its different
>    congestion control types [RFC4341][RFC4342][RFC5622].
>
> First, this paragraph ignores potential deployment issues with any of
> these other than TCP, which risks seeming out of touch, but this is a minor
> point and probably not worth a late edit. Second, I'm concerned this
> recommendation could be taken as broader than intended, against the
> definition of any new transport protocol encapsulated within UDP that
> performs substantially the same function as the listed protocols.
>
> I think this can be made clearer by simply adding to the list of examples:
>
> NEW:
>
>    These mechanisms are difficult to implement correctly.  For most
>    applications, the use of one of the existing IETF transport protocols
>    is the simplest method of acquiring the required mechanisms.  Doing
>    so also avoids issues that protocols using a new IP protocol number
>    face when being deployed over the Internet, where middleboxes that
>    only support TCP and UDP are not rare.  Consequently, the RECOMMENDED
>    alternative to the UDP usage described in the remainder of this
>    section is the use of an IETF transport protocol such as TCP
>    [RFC0793], Stream Control Transmission Protocol (SCTP) [RFC4960], and
>    SCTP Partial Reliability Extension (SCTP-PR) [RFC3758], or Datagram
>    Congestion Control Protocol (DCCP) [RFC4340] with its different
>    congestion control types [RFC4341][RFC4342][RFC5622], or transport
>    protocols specified by the IETF in the future.
>
> and removing the examples from the summary in section 7:
>
> OLD:
>
>    | SHOULD use a full-featured transport (TCP, SCTP, DCCP)  |         |
>
> NEW:
>
>    | SHOULD use a full-featured transport                    |         |
>
> Thanks, cheers,
>
> Brian
>
>
> > On 18 May 2016, at 02:17, The IESG <iesg-secretary@ietf.org
> <javascript:;>> wrote:
> >
> >
> > The IESG has received a request from the Transport Area Working Group WG
> > (tsvwg) to consider the following document:
> > - 'UDP Usage Guidelines'
> >  <draft-ietf-tsvwg-rfc5405bis-13.txt> as Best Current Practice
> >
> > The IESG plans to make a decision in the next few weeks, and solicits
> > final comments on this action. Please send substantive comments to the
> > ietf@ietf.org <javascript:;> mailing lists by 2016-05-31.
> Exceptionally, comments may be
> > sent to iesg@ietf.org <javascript:;> instead. In either case, please
> retain the
> > beginning of the Subject line to allow automated sorting.
> >
> > Abstract
> >
> >
> >   The User Datagram Protocol (UDP) provides a minimal message-passing
> >   transport that has no inherent congestion control mechanisms.  This
> >   document provides guidelines on the use of UDP for the designers of
> >   applications, tunnels and other protocols that use UDP.  Congestion
> >   control guidelines are a primary focus, but the document also
> >   provides guidance on other topics, including message sizes,
> >   reliability, checksums, middlebox traversal, the use of ECN, DSCPs,
> >   and ports.
> >
> >   Because congestion control is critical to the stable operation of the
> >   Internet, applications and other protocols that choose to use UDP as
> >   an Internet transport must employ mechanisms to prevent congestion
> >   collapse and to establish some degree of fairness with concurrent
> >   traffic.  They may also need to implement additional mechanisms,
> >   depending on how they use UDP.
> >
> >   Some guidance is also applicable to the design of other protocols
> >   (e.g., protocols layered directly on IP or via IP-based tunnels),
> >   especially when these protocols do not themselves provide congestion
> >   control.
> >
> >   This document obsoletes RFC5405 and adds guidelines for multicast UDP
> >   usage.
> >
> >
> >
> >
> > The file can be obtained via
> > https://datatracker.ietf.org/doc/draft-ietf-tsvwg-rfc5405bis/
> >
> > IESG discussion can be tracked via
> > https://datatracker.ietf.org/doc/draft-ietf-tsvwg-rfc5405bis/ballot/
> >
> >
> > No IPR declarations have been submitted directly on this I-D.
> >
> >


I disagree.  The text as-is is best and represents a prudent period of
review in the WG.  As suggested many times to both spud and quic, extending
udp is not recommended. We have multiple L4 transport protocols for a
reason, you should innovative in that space without UDP.

CB