[manet] undirectional or bidirectional (Was Re: I-D Action: draft-ietf-manet-dlep-da-credit-extension-00.txt)

Lou Berger <lberger@labn.net> Thu, 09 February 2017 22:26 UTC

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To: "Ratliff, Stanley" <sratliff@idirect.net>
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From: Lou Berger <lberger@labn.net>
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Date: Thu, 9 Feb 2017 17:25:49 -0500
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Subject: [manet] undirectional or bidirectional (Was Re: I-D Action: draft-ietf-manet-dlep-da-credit-extension-00.txt)
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Thanks Stan.


    So one of the basic differences in the drafts is that this document
only supports flow control in one direction, i.e., for traffic sent from
a router to a modem, while the other credit-window draft supports it in
both directions.  We'd like feedback from the WG on which approach to

We (authors of the DA draft) made a conscious choice to limit the DA
credit based flow control to one direction out of the desire to keep the
extension as simple as possible and to provide what is really expected
to be used.

Clearly the reason for being able to control traffic that is sent from
the router to the modem/radio is pretty easily understood.  Also, while
bidirectional flow control existed in pre-dlep solutions, it wasn't
really used -- and in one reported bug/case resulted in traffic dropped
unnecessarily.  That said, it at first seemed appealing to define a
symmetric approach that supports flow control in either direction, but
when getting into the details of DLEP message formats ( and different
message types in general, based on sender type) the result was a
symmetric solution that used non-symmetric messaging - which in the
authors opinion was fairly complex. So, given:
    (a) the added complexity of document/protocol/code needed to support
        bidirectional credit control and
    (b) no one has ever used or currently expects to use credit flow
        control for traffic destined to a router

We concluded that unidirectional definition was the right place to aim
*at this time*.  This of course doesn't preclude someone from defining a
companion definition for modem to router traffic flow control down the
road -- when there is an actual need.

So the question for the WG is:

Should the merged / future credit window definition support (1)
bidirectional (credit) flow control, or (2) flow control for only
traffic from a router to a modem?

Said another way: does anyone wish to advocate the position that we need
credit window flow control for traffic received over the air, and sent
from modem to router, *now*?

On 2/9/2017 4:39 PM, Ratliff, Stanley wrote:
> WG Participants, 
> Please note that there is already agreement to merge this draft with the existing credit-windowing draft. 
> Regards,
> Stan
>> -----Original Message-----
>> From: manet [mailto:manet-bounces@ietf.org] On Behalf Of internet-
>> drafts@ietf.org
>> Sent: Thursday, February 09, 2017 4:38 PM
>> To: i-d-announce@ietf.org
>> Cc: manet@ietf.org
>> Subject: [manet] I-D Action: draft-ietf-manet-dlep-da-credit-extension-
>> 00.txt
>> A New Internet-Draft is available from the on-line Internet-Drafts directories.
>> This draft is a work item of the Mobile Ad-hoc Networks of the IETF.
>>         Title           : DLEP DiffServ Aware Credit Windowing Extension
>>         Authors         : Bow-Nan Cheng
>>                           David Wiggins
>>                           Lou Berger
>> 	Filename        : draft-ietf-manet-dlep-da-credit-extension-00.txt
>> 	Pages           : 15
>> 	Date            : 2017-02-09
>> Abstract:
>>    This document defines an extension to the DLEP protocol that enables
>>    a DiffServ aware credit-windowing scheme for destination-specific
>>    flow control.
>> The IETF datatracker status page for this draft is:
>> https://urldefense.proofpoint.com/v2/url?u=https-
>> 3A__datatracker.ietf.org_doc_draft-2Dietf-2Dmanet-2Ddlep-2Dda-2Dcredit-
>> 2Dextension_&d=DwICAg&c=LlUvidvlhStGUSxQl0giOA&r=QzgCKlK-
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>> There's also a htmlized version available at:
>> https://urldefense.proofpoint.com/v2/url?u=https-
>> 3A__tools.ietf.org_html_draft-2Dietf-2Dmanet-2Ddlep-2Dda-2Dcredit-
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