Re: [tcpm] 793bis and RFC3168

Gorry Fairhurst <gorry@erg.abdn.ac.uk> Thu, 07 October 2021 07:56 UTC

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To: tom petch <ietfa@btconnect.com>, Wesley Eddy <wes@mti-systems.com>, "tcpm@ietf.org" <tcpm@ietf.org>
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From: Gorry Fairhurst <gorry@erg.abdn.ac.uk>
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Subject: Re: [tcpm] 793bis and RFC3168
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On 06/10/2021 13:00, tom petch wrote:
> Does 793bis warrant an
> Updates 3168?
>
> It does change the format of the IANA registry as created by RFC3168 and so would seem an update.  I realise that the IANA registry will point to 793bis; I am unclear whether the revised registry will have any mention of RFC3168 not that it changes my view on Updates.
>
> Tom Petch
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> tcpm@ietf.org
> https://www.ietf.org/mailman/listinfo/tcpm

Thanks for asking, I looked at this.

RFC 3168 gave initial contents of the registry and stated:

    The Transmission Control Protocol (TCP) included a 6-bit Reserved
    field defined inRFC 793  <https://datatracker.ietf.org/doc/html/rfc793>, reserved for future use, in bytes 13 and 14
    of the TCP header, as illustrated below.  The other six Control bits
    are defined separately byRFC 793  <https://datatracker.ietf.org/doc/html/rfc793>.


This could have been handled more elegantly, but  I think the RFC3168 
text remains correct, in that the base TCP spec (RFC793, or it's bis) 
define the 6 other bits.  To me, there is no change to the meaning of 
RFC3168 intended by 793bis, and I think updating a reference would not 
need to be flagged as an update.

Best wishes,

Gorry Fairhurst

(as co-chair tsvwg).