[ih] TCP 2.5

[Noel Chiappa]

    > From: Bob Braden <braden at ISI.EDU>

    > I am glad to hear that I am not the only one who distinctly recalls
    > 2.5. But I have been unable to locate any documentation of it.
    > Perhaps it was quickly renumbered 3

Hmm. Well, RFC-750 contains the following number for protocol type:

      Decimal   Octal      Format                             References
      -------   -----      ------                             ----------
          0      0         Reserved
          1      1         raw internet                             [42]
          2      2         TCP-3                                    [36]
          3      3         DSP                                   [37,38]
          4      4         Gateway Monitoring Message               [41]
          5      5         TCP-3.1                                  [45]
          6      6         TCP-4                                    [46]

Not much help there... However, there's also a table of IP header version
numbers:

      Decimal   Octal      Version                            References
      -------   -----      -------                            ----------
          0      0         March 1977 version                       [35]
          1      1         January 1978 version                     [36]
          2      2         February 1978 version A                  [42]
          3      3         February 1978 version B                  [43]
          4      4         September 1978 version 4                 [44]

   [35]   Cerf, V. "Specification of Internet Transmission Control
          Program -- TCP (version 2)," March 1977.
   [36]   Cerf, V. and J. Postel, "Specification of Internetwork
          Transmission Control Program -- TCP Version 3,"
          USC-Information Sciences Institute, January 1978.

   [42]   Postel, J. "Draft Internetwork Protocol Specification --
          Version 2," USC-Information Sciences Institute, February 1978.
   [43]   Cerf, V. "A Proposed New Internet Header Format," Advanced
          Research Projects Agency, IEN 26, 14 February 1978.
   [44]   Postel, J. "Internetwork Protocol Specification -- Version 4,"
          IEN-54, USC-Information Sciences Institute, September 1978.
   [45]   Cerf, V. "A Proposal for TCP Version 3.1 Header Format,"
          Advanced Research Projects Agency, IEN 26, 14 February 1978.
   [46]   Postel, J. "Specification of Internetwork Transmission Control
          Protocol -- Version 4," IEN-55, USC-Information Sciences
          Institute, September 1978.

Now, this is interesting. "Internet" header version 0 was TCP 2, and
header version 1 was TCP 3. So either 2.5 got renamed to 3, or it was
just a paper exercise, or something, would be my guess.

	Noel