Subject: [sfc] I-D Action: draft-ietf-sfc-nsh-ecn-support-06.txt

From: [email-masked]
Date: Mon, 13 Sep 2021 13:05:19 -0700

A New Internet-Draft is available from the on-line Internet-Drafts directories.
This draft is a work item of the Service Function Chaining WG of the IETF.

        Title           : Explicit Congestion Notification (ECN) and Congestion Feedback Using the Network Service Header (NSH) and IPFIX
        Authors         : Donald E. Eastlake
                          Bob Briscoe
                          Yizhou Li
                          Andrew G. Malis
                          Xinpeng Wei
	Filename        : draft-ietf-sfc-nsh-ecn-support-06.txt
	Pages           : 33
	Date            : 2021-09-13

Abstract:
   Explicit congestion notification (ECN) allows a forwarding element to
   notify downstream devices of the onset of congestion without having
   to drop packets. Coupled with a means to feed information about
   congestion back to upstream nodes, this can improve network
   efficiency through better congestion control, frequently without
   packet drops. This document specifies ECN and congestion feedback
   support within a Service Function Chaining (SFC) architecture domain
   through use of the Network Service Header (NSH, RFC 8300) and IP Flow
   Information Export (IPFIX, RFC 7011).

The IETF datatracker status page for this draft is:
https://datatracker.ietf.org/doc/draft-ietf-sfc-nsh-ecn-support/

There is also an htmlized version available at:
https://datatracker.ietf.org/doc/html/draft-ietf-sfc-nsh-ecn-support-06

A diff from the previous version is available at:
https://www.ietf.org/rfcdiff?url2=draft-ietf-sfc-nsh-ecn-support-06

Internet-Drafts are also available by anonymous FTP at:
ftp://ftp.ietf.org/internet-drafts/

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From: Donald Eastlake <[email-masked]>
Date: Mon, 13 Sep 2021 16:56:01 -0400

This revision has minor wording improvements.

To my mind there is one substantial issue with this draft: What to do
about SFs that add or remove packets from a flow or lengthen or
shorten such packets. If this is ignored, the document is much less
useful for such flows. The simplest solution seems to be that such SFs
should optionally signal forward in separate packets the changes they
have made, of this sort, to flows. I plan to look into adding such a
facility.

Thanks,
Donald
===============================
 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
 2386 Panoramic Circle, Apopka, FL 32703 USA
 [email-masked]

On Mon, Sep 13, 2021 at 4:06 PM <[email-masked]> wrote:
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From: "Joel M. Halpern" <[email-masked]>
Date: Mon, 13 Sep 2021 17:07:59 -0400

While such a facility (to inform about packet changes) has 
understandable value, I tend to doubt the likelihood of it being used. 
It seeems an unlikely upgrade for a SF builder to bother implementing, 
since it is likely to be significant effort.  And existing SF (including 
all those behind proxies) will not support it.

Yours,
Joel

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From: Donald Eastlake <[email-masked]>
Date: Wed, 15 Sep 2021 01:24:40 -0400

Hi Joel,

On Mon, Sep 13, 2021 at 5:08 PM Joel M. Halpern <[email-masked]> wrote:
> It seems an unlikely upgrade for a SF builder to bother implementing,
> since it is likely to be significant effort.  And existing SFs (including

The issue is covered in a Section in the draft so at least it isn't
just ignored. Would you recommend perhaps one more pass to polish the
draft and then proceed to a WG Last Call without adding such a
mechanism?

Thanks,
Donald