Re: [tcpm] Please review 793bis!

"Rodney W. Grimes" <4bone@gndrsh.dnsmgr.net> Tue, 30 July 2019 13:09 UTC

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From: "Rodney W. Grimes" <4bone@gndrsh.dnsmgr.net>
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To: mohamed.boucadair@orange.com
Date: Tue, 30 Jul 2019 06:09:30 -0700 (PDT)
CC: "Rodney W. Grimes" <4bone@gndrsh.dnsmgr.net>, Wesley Eddy <wes@mti-systems.com>, "tcpm@ietf.org" <tcpm@ietf.org>
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Subject: Re: [tcpm] Please review 793bis!
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Hello Med,
Replied inline, trying to get this style, so pardon any
mistakes I may be making.

Regards,
Rod

> Hi Rodney, 
> 
> Please see iline. 
> 
> Cheers,
> Med
> 
> > -----Message d'origine-----
> > De?: Rodney W. Grimes [mailto:4bone@gndrsh.dnsmgr.net]
> > Envoy??: lundi 29 juillet 2019 22:36
> > ??: 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.

 [RWG] If infact the author "moves" section 2.1 to be under 3
in the draft in effect 2.1 would either go away, or become
something different.

> > >
> > > 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:

 [RWG] Perhaps another cup of coffee?  :-)
 
> 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

 [RWG] This does look to be a section 2.1 to me, did you miss it?

>   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.  

 [RWG] I am concerned about historical references to this document in
such things as code, text books, and other RFC's, but without solid
evidence to that effect I have little ground to stand on.

On the other hand I should further investigate:
./sys/netinet/tcp_fsm.h: * Per RFC793, September, 1981.
./sys/netinet/tcp_input.c:    "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets");
./sys/netinet/tcp_input.c:    "Follow RFC793 instead of RFC5961 criteria for accepting RST packets");
./sys/netinet/tcp_input.c:               * is equivalent to the smoothing algorithm in rfc793 with
./sys/netinet/tcp_input.c:               * equivalent to rfc793 smoothing with an alpha of .75
./sys/netinet/tcp_input.c:               * rfc793's wired-in beta.
./sys/netinet/tcp_syncache.c:    * See RFC 793 page 65, section SEGMENT ARRIVES.
./sys/netinet/tcp_syncache.c:    * RFC 793 page 37:

I do understand that the document name is changing, but how to make
it clear to a person reading the code above and pulling up 793bis that they
should be looking to 793 is unclear to me at this point in time.

Is it possible to use the datatracker to see the changes
from rfc793 to rfc793bis?

What about a section on "what has changed, added, and/or removed",
usually when a specification evolves over time there is a history
section that itemizes the changes.  This may be asking for far too
much in this case though.

> > 
> > 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.   

 [RWG] Have it read "Unassigned" in the spec that has almost 40
years of running code that call it rsrvd is of equal
concern from an implementers standpoint.  Any attempt
to back port RFC8126 language into the prior 8000 RFC's seems
difficult.

Should RFC8126 apply to any RFC prior to it unless
explicitly stated in the header of RFC8126?  Or is it the
fact that chrnologically RFC793bis is after 8126 that should
be applied here.  That would require one to have a date order
of issue index to the rfcs?

> 
> > 
> > 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. 

 [RWG] I think it would be incorrect to do so, it would surely mess up 
the presentation of information in the:
https://www.iana.org/assignments/tcp-header-flags/tcp-header-flags.xhtml
page which has back references to the RFC that had the IANA consideration.

If rfc3168 had populated say the SYN code point, the reference at IANA would
be to rfc3168 and yet in that RFC I would find little information on
the definition of the SYN flag.

> 
> > 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.
 [RWG] We fully agree on that

> 
> > 
> > > > * 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

-- 
Rod Grimes                                                 rgrimes@freebsd.org