Re: [tsvwg] TCP Prague's RFC 5033 guidelines status?

Wesley Eddy <wes@mti-systems.com> Mon, 11 November 2019 22:12 UTC

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To: "Black, David" <David.Black@dell.com>, "tsvwg@ietf.org" <tsvwg@ietf.org>
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From: Wesley Eddy <wes@mti-systems.com>
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Date: Mon, 11 Nov 2019 17:11:43 -0500
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Subject: Re: [tsvwg] TCP Prague's RFC 5033 guidelines status?
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On 11/11/2019 11:06 AM, Black, David wrote:
> Well, L4S imposes strict requirements on end-host algorithms for traffic that uses the low-latency service.  TCP Prague is the only known transport protocol that satisfies those requirements, i.e., no other existing TCP or DCTCP code satisfies those requirements, as far as I am aware (please correct this statement if it's wrong).
>
> For that reason, decisions about deploying L4S and TCP Prague appear to be linked, as it would be silly to deploy a network service (L4S) that cannot be used by end-systems, and end-system usage of L4S appears to require TCP Prague.


I believe you're referring to the congestion response requirements in 
the L4S ID draft.  I think those are a start to requiring an end-host 
algorithm to have good properties with regard to 5033 guidelines, rather 
than requiring some bad behavior (e.g. the first one is "MUST coexist 
safely with Reno" which speaks right to 5033 guideline 1 "Impact on 
Standard TCP, SCTP, and DCCP").  So, I'm not sure why those are a 
concern (i.e. which L4S ID congestion response requirements do we have 
5033 concerns with?).

If really needed, it seems like the 5033 guidelines could be mapped to 
sections of the L4S documents where the topics are discussed, but I'm 
not sure how meaningful it could be without regard to specific scalable 
end-host algorithms (e.g. Prague).