Re: [tcpm] RFC793bis AD review

Joseph Touch <touch@strayalpha.com> Wed, 07 July 2021 05:25 UTC

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From: Joseph Touch <touch@strayalpha.com>
In-Reply-To: <59e1d10e-542c-3f1f-7098-4f1d8932da5b@mti-systems.com>
Date: Tue, 6 Jul 2021 22:25:04 -0700
Cc: Martin Duke <martin.h.duke@gmail.com>, draft-ietf-tcpm-rfc793bis.all@ietf.org, "tcpm@ietf.org Extensions" <tcpm@ietf.org>
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To: Wes Eddy <wes@mti-systems.com>
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Subject: Re: [tcpm] RFC793bis AD review
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Hi, all,

> On Jun 30, 2021, at 2:50 PM, Wesley Eddy <wes@mti-systems.com> wrote:
> 
>> (3.7.2) In the first paragraph it says
>> RFC 1122 <https://datatracker.ietf.org/doc/html/rfc1122> recommends an IP-layer default
>>    effective MTU of less than or equal to 576 for destinations not
>>    directly connected
>> In the last it says
>> RFC 1191 <https://datatracker.ietf.org/doc/html/rfc1191> discusses this implication of many older TCP
>>    implementations setting MSS to 536 for non-local destinations, rather
>>    than deriving it from the MTUs of connected interfaces as
>>    recommended.
>> Could we unify these comments in the same location? Implementers browsing the spec should see the old recommendation and its drawback in the same place.
> Good idea; I think we can.
> 
Two things that might be useful to include

- first, these are intended to refer to the same number; one is an IP MTU, the other a TCP MSS
- for the second, it’s useful to refer to RFC 6691 as well as to note that this value is for TCP over IPv4

Joe