Re: [tcpm] Please review 793bis!

<mohamed.boucadair@orange.com> Tue, 30 July 2019 05:38 UTC

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From: <mohamed.boucadair@orange.com>
To: "Rodney W. Grimes" <4bone@gndrsh.dnsmgr.net>, Wesley Eddy <wes@mti-systems.com>
CC: "tcpm@ietf.org" <tcpm@ietf.org>
Thread-Topic: [tcpm] Please review 793bis!
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Date: Tue, 30 Jul 2019 05:38:38 +0000
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Subject: Re: [tcpm] Please review 793bis!
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Hi Rodney, 

Please see iline. 

Cheers,
Med

> -----Message d'origine-----
> De : Rodney W. Grimes [mailto:4bone@gndrsh.dnsmgr.net]
> Envoyé : lundi 29 juillet 2019 22:36
> À : Wesley Eddy
> Cc : tcpm@ietf.org; BOUCADAIR Mohamed TGI/OLN
> Objet : Re: [tcpm] Please review 793bis!
> 
> > Many thanks for your comments; my thoughts are below:
> >
> > On 7/29/2019 5:35 AM, mohamed.boucadair@orange.com wrote:
> > > Hi all,
> > >
> > > Please find below some very minor comments to enhance the readability
> of the document:
> > >
> > > * Consider moving Section 2.1 to be listed under Section 3.
> >
> > Either way is fine with me; does anyone have strong preference? The
> > section numbering is closer to the original 793 numbering currently, and
> > this would probably bump that, but that is a very trivial concern.
> 
> I would counter that section renumbering breaks all external
> references to this document by section number and should probably
> be avoided at all cost.
> 
> As an example if someone wrote someplace "See section 2.1 of rfc793",
> that reference would be broken, other than the new document is called
> rfc793bis, that may be lost on the seeker of the information.

[Med] Hmm, there is no such 2.1 in RFC793:

RFC793

1.  INTRODUCTION ..................................................... 1

  1.1  Motivation .................................................... 1
  1.2  Scope ......................................................... 2
  1.3  About This Document ........................................... 2
  1.4  Interfaces .................................................... 3
  1.5  Operation ..................................................... 3

2.  PHILOSOPHY ....................................................... 7

  2.1  Elements of the Internetwork System ........................... 7
  2.2  Model of Operation ............................................ 7
  2.3  The Host Environment .......................................... 8
  2.4  Interfaces .................................................... 9
  2.5  Relation to Other Protocols ................................... 9
  2.6  Reliable Communication ........................................ 9
  2.7  Connection Establishment and Clearing ........................ 10
  2.8  Data Communication ........................................... 12
  2.9  Precedence and Security ...................................... 13
  2.10 Robustness Principle ......................................... 13

3.  FUNCTIONAL SPECIFICATION ........................................ 15


RFC793bis

   1.  Purpose and Scope . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.1.  Key TCP Concepts  . . . . . . . . . . . . . . . . . . . .   5
   3.  Functional Specification  . . . . . . . . . . . . . . . . . .   5

I think that Wes tried to preserve the overall structure of Section 3.  

> 
> A search of the RFCs for section references to 793 could be attempted.
> 
> > > * Rsrvd - Reserved:  s/Reserved/Unassigned. This is to be aligned with
> https://tools.ietf.org/html/rfc8126#section-6 (reserved in 8126 has a
> special meaning: "Reserved:  Not assigned and not available for
> assignment.")
> >
> > Thanks; I'll have to look at this in all cases and make sure we "do the
> > right thing".? I hadn't really been aware of 8126.
> 
> Though I am new here and may be wrong on this,
> 8126 is about IANA considerations and should, if I am
> reading it correctly, only be apply to text in the IANA
> consideration section of an RFC and not to the whole
> body of it.

[Med] It will be weird to use "Reserved" in the main text and "Unassigned" in the IANA section. Following RFC8126 would be my favorite here.   

> 
> I especially do not like the definition of
> Reserved as stated in 8126, that is more than reserved,
> it is immutable.  But that is for the topic of another
> draft.
> 
> >
> > > * Add a pointer to the "TCP Header Flags" registry:
> https://www.iana.org/assignments/tcp-header-flags/tcp-header-flags.xhtml
> > >
> > > * Add an IANA action to update the above registry to include all TCP
> flags, not only those in 3168. Also, the description text in that page
> should be reworked, IMHO. Unassigned bits should also be indicated as such
> in that page.
> > >
> > > I would like to have those referenced in that page rather than having
> documents requiring access to these bits to duplicate the effort: see for
> example  RFC8519 (look for "reserved" and "flags" in Page 33).
> >
> > Good point.? 3168 created the registry, but then didn't fully populate
> > it with the bits that 793 had defined.
> 
> This is probably of historical cause, 793 being a very early RFC.
> It would be wrong of 3168 to populate anything

[Med] There is nothing wrong with another RFC than 793 to create and initialize the flags registry. 

> other than 3168 bits, but I see 793bis as populating
> the other bits of TCP as a proper and needed update.

[Med] Hence the need to fix the registry rather than leaving it incomplete.

> 
> > > * Position titles right after figure #, e.g.,
> > >
> > > OLD:
> > >
> > >                                 TCP Header Format
> > >
> > >               Note that one tick mark represents one bit position.
> > >
> > >                                   Figure 1
> > >
> > > NEW:
> > >
> > >               Note that one tick mark represents one bit position.
> > >
> > >                                   Figure 1: TCP Header Format
> >
> > Also a good idea ... I will make this change, unless anyone shouts.
> >
> >
> > > * Introduce some notations used in the document (and a pointer to
> Appendix B), e.g.,
> > >
> > >       The window size MUST be treated as an unsigned number, or else
> > >       large window sizes will appear like negative windows and TCP
> will
> > >       now work (MUST-1) .  It is RECOMMENDED that implementations will
> > >                ^^^^^^^^
> > >       reserve 32-bit fields for the send and receive window sizes in
> the
> > >       connection record and do all window computations with 32 bits
> (REC-
> > >
> ^^^^
> > >       1 ).
> > >
> > > Idem for SHLD-, etc.
> >
> > Good point.? It seems like explaining this in the introduction will
> work.
> >
> >
> > > * Section 3.1
> > >
> > > OLD:
> > >
> > >       The checksum also covers a pseudo header conceptually prefixed
> to
> > >       the TCP header.  The pseudo header is 96 bits for IPv4 and 320
> bits
> > >       for IPv6.  For IPv4, this pseudo header contains the Source
> > >       Address, the Destination Address, the Protocol, and TCP length.
> > >
> > > NEW:
> > >       The checksum also covers a pseudo header conceptually prefixed
> to
> > >       the TCP header.  The pseudo header is 96 bits for IPv4 and 320
> bits
> > >       for IPv6.  For IPv4, this pseudo header contains the Source
> > >       Address, the Destination Address, the Protocol (PTCL), and TCP
> length.
> > >                                                      ^^^^^^
> > >
> > > * Section 3.1: Add missing figure legend, e.g.,
> > >
> > >                     +--------+--------+--------+--------+
> > >                     |           Source Address          |
> > >                     +--------+--------+--------+--------+
> > >                     |         Destination Address       |
> > >                     +--------+--------+--------+--------+
> > >                     |  zero  |  PTCL  |    TCP Length   |
> > >                     +--------+--------+--------+--------+
> > >
> > > * Section 3.3:
> > >
> > > OLD:
> > >   The synchronization requires each side to send it's own initial
> > >
> > > NEW:
> > >   The synchronization requires each side to send its own initial
> >
> > Many thanks; all of the above suggestions look good to me.
> 
> Indeed.
> 
> > _______________________________________________
> > tcpm mailing list
> > tcpm@ietf.org
> > https://www.ietf.org/mailman/listinfo/tcpm
> 
> --
> Rod Grimes
> rgrimes@freebsd.org