Re: [trill] Shepherd's report on draft-ietf-trill-ecn-support-04

Donald Eastlake <d3e3e3@gmail.com> Mon, 05 February 2018 04:59 UTC

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From: Donald Eastlake <d3e3e3@gmail.com>
Date: Sun, 4 Feb 2018 23:59:16 -0500
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To: Bob Briscoe <ietf@bobbriscoe.net>
Cc: Susan Hares <shares@ndzh.com>, trill@ietf.org
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Subject: Re: [trill] Shepherd's report on draft-ietf-trill-ecn-support-04
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Hi Bob,

All your changes look good to me.

Thanks,
Donald
===============================
 Donald E. Eastlake 3rd   +1-508-333-2270 (cell)
 155 Beaver Street, Milford, MA 01757 USA
 d3e3e3@gmail.com


On Sat, Feb 3, 2018 at 8:31 PM, Bob Briscoe <ietf@bobbriscoe.net> wrote:
> Sue,
>
> Thanks for the editorial suggestions.
> Donald, I'm happy with Sue's specific suggestions if you are.
>
> Responses inline...
>
> On 22/01/18 15:18, Susan Hares wrote:
>
> As part of the shepherd’s duties, I’ve review
> draft-ietf-trill-ecn-support-04.txt to determine if it is ready for
> publication.
>
>
>
> Status: Ready with editorial nits
>
>
>
> General comment:  I’m thrilled to see an RBridge specification enacting aids
> for advanced congestion control mechanisms.
>
> What I’ve checked: normative references including
> draft-ietf-twvwg-enc-encap-guidelines-01/txt
>
> BTW, it's currently -09, not -01.
>
> I suggest the following changes to each occurrence of a citation of
> [ECNencapGuide]:
>
> 1. Introduction
> <No change to both citations, which are to the whole of [ECNencapGuide] in
> general>
>
> 3. ECN Support
>
> CURRENT:
>
>    ... which correspond to the recommended provisions of
>    [ECNencapGuide].
>
>
> SUGGESTED:
>
>    ... which correspond to the recommended provisions in section 3 and
> sections 5.1-5.4 of
>    [ECNencapGuide].
>
>
> 3.1. Ingress ECN Support
>
> CURRENT:
>
>       ... it MUST follow the guidelines in [ECNencapGuide]
>       to add a Flags Word to the TRILL Header.
>
>
> SUGGESTED:
>
>       ... it MUST follow the guidelines in Section 5.3 of [ECNencapGuide]
>       to add a Flags Word to the TRILL Header.
>
>
> 3.3 Egress ECN Support
>
> CURRENT:
>
>    Drop is the intended behavior for such a packet, as required by
>    [ECNencapGuide].
>
>
> SUGGESTED:
>
>    Drop is the intended behavior for such a packet, as required by Section
> 5.4 of
>    [ECNencapGuide].
>
>
> CURRENT:
>
>    o  When decapsulating a non-IP protocol frame with a means of
>       indicating ECN that is understood by the RBridge, it MUST follow
>       the guideines in [ECNencapGuide] when setting the ECN information
>       in the decapsulated native frame.
>
>
> SUGGESTED:
>
>    o  When decapsulating a non-IP protocol frame with a means of
>       indicating ECN that is understood by the RBridge, it MUST follow
>       the guideines in Section 5.4 of [ECNencapGuide] when setting the ECN
> information
>       in the decapsulated native frame.
>
>
>
>
>
> Editorial nits are below.  You can adopt or ignore the editorial nits.
>
>
>
> Sue Hares
>
> ===========
>
>
>
> Editorial nits:
>
>
>
> General – it may be helpful to specify section in the [ECNencapGuide] –
> document, and RFC7567.  While the way you specify it is correct, it may help
> the reader to narrow down the scope within the document.
>
>
>
> #1
>
>    Explicit congestion notification (ECN [RFC3168]) allows a forwarding
>
>    element, such as a router, to notify downstream devices, including
>
>    the destination, of the onset of congestion without having to drop
>
>    packets.
>
>
>
> The multiple commons in this sentence do not lend to easy reading of the
> initial sentence.
>
> One alternative is:
>
>
>
>    Explicit congestion notification (ECN [RFC3168]) allows a forwarding
>
>    Element (such as a router) to notify downstream devices, including
>
>    the destination, of the onset of congestion without having to drop
>
>    packets.
>
>
>
> However you may wish to revise the sentence in an alternative way.
>
>
>
>
>
> #2 – Section 2. Paragraph 2. Sentences 4
>
> Old/Extesnion Flags Word./
>
> New/Extension Flags Word./
>
>
>
>
>
> #3 – Section 3.3 is dense and thoughtful text.  I am not sure you can
> improve it, but it too me several reads to make sure I understood it
> correctly.
>
>
>
> I think it might help if we created two subsections within 3.3 for:
> 3.3.1: "Non-ECN Egress RBridge" the first para
> 3.3.2: "ECN Egress RBridge" for the rest of the section
>
> Also, it might make it clearer if the two bullets were explicitly flagged as
> mutually exclusive alternatives:
>
> CURRENT:
>
>    If an RBridge supports ECN, the egress behavior is as follows:
>
> SUGGESTED:
>
>    If an RBridge supports ECN, for the two cases of an IP and a non-IP inner
> packet,
>    the egress behavior is as follows:
>
>
> Then, instead of the two bullet symbols, perhaps use hanging indented
> headers:
>
>    Decapsulating an inner IP packet: The RBridge sets the ECN
>       ...
>    Decapsulating a non-IP protocol frame: If the frame has a means of
>       indicating ECN that is understood by the RBridge, the RBridge MUST
> follow
>       ...
>
>
>
> Other suggested edits to make the going easier:
>
> CURRENT:
>
>          In the case where the TRILL 3-bit ECN codepoint indicates
>       congestion experienced (CE) but the encapsulated native IP frame
>       indicates a not ECN-capable transport (Not-ECT), the RBridge MUST
>       drop the packet.
>
>
> SUGGESTED:
>
>          In the case where the TRILL 3-bit ECN codepoint indicates
>       congestion experienced (CE) but the encapsulated native IP frame
>       indicates a not ECN-capable transport (Not-ECT), it can be seen that
> the RBridge MUST
>       drop the packet.
>
> RATIONALE:
> To reassure the reader that this req't is already described in the table; it
> is not an additional req't.
>
> HTH
>
>
>
> Bob
>
>
>
>
>
>
>
> --
> ________________________________________________________________
> Bob Briscoe                               http://bobbriscoe.net/