On Thursday, June 2, 2016, Brian Trammell <ietf(_at_)trammell(_dot_)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(_at_)ietf(_dot_)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(_at_)ietf(_dot_)org <javascript:;> mailing lists by 2016-05-31.
Exceptionally, comments may be
sent to iesg(_at_)ietf(_dot_)org <javascript:;> instead. In either case,
please
retain the
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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