[COFF] Fwd: [ih] NCP and TCP implementations

[Clem Cole]

s/Leah/Lead/   <-- finger  fumble/ROM clash (my daughters first name)

On Tue, Mar 10, 2020 at 2:30 PM Clem Cole <clemc at ccc.com> wrote:

>
> On Tue, Mar 10, 2020 at 2:23 PM Warner Losh <imp at bsdimp.com> wrote:
>
>> >>>  In addition to the Berkeley BSD work, I remember Gurwitz, Wingfield,
>> Nemeth, and others working on TCP implementation for the PDP-11/70 and Vax.
>>
>> This is new. I'd like more info The name Nemeth is interesting. Is that
>> Evi? And does that body of code still exist?
>>
> Alan Nemeth -- former BBN Fellow, later DEC CCE.  Leah Architect of the
> C30/C70 and the Bufferfly.
> This is the 'official' IP/TCP implementation for UNIX.  Joy would start
> with it.  A version of the code is in Warren's archives and on Kirk's
> larger disk.
>
>
>>
>> >>> I think I speak authoritatively here, since I wrote and debugged that
>> first Unix TCP code.   I still have an old, yellowing listing of that first
>> Unix TCP.
>>
>> I wonder if you could write him and see if this listing can be scanned /
>> preserved...
>>
> I have this AM in fact before I sent the message to you -- no response so
> far.
>
>>
>> Warner
>>
>> On Tue, Mar 10, 2020 at 11:52 AM Clem Cole <clemc at ccc.com> wrote:
>>
>>>
>>> Given the recent discussion of pipes and networking ...  I'm passing
>>> this along for those that might not have seen it.
>>>
>>> ---------- Forwarded message ---------
>>> From: Jack Haverty via Internet-history
>>> Date: Tue, Mar 10, 2020 at 1:30 PM
>>> Subject: Re: [ih] NCP and TCP implementations
>>> To: *Internet-History*
>>>
>>>
>>> The first TCP implementation for Unix was done in PDP-11 assembly
>>> language, running on a PDP-11/40 (with way too little memory or address
>>> space).   It was built using code fragments excerpted from the LSI-11
>>> TCP implementation provided by Jim Mathis, which ran under SRI's
>>> home-built OS.  Jim's TCP was all written in PDP-11 assembler.  The code
>>> was cross-compiled (assembled) on a PDP-10 Tenex system, and downloaded
>>> over a TTY line to the PDP-11/40.  That was much easier and faster than
>>> doing all the implementation work on the PDP-11.
>>>
>>> The code architecture involved putting TCP itself at the user level,
>>> communicating with its "customers" using Unix InterProcess
>>> Communications facilities (Rand "Ports").   It would have been
>>> preferable to implement TCP within the Unix kernel, but there was simply
>>> not enough room due to the limited address space available on the 11/40
>>> model.  Later implementations of TCP, on larger machines with twice the
>>> address space, were done in the kernel.  In addition to the Berkeley BSD
>>> work, I remember Gurwitz, Wingfield, Nemeth, and others working on TCP
>>> implementation for the PDP-11/70 and Vax.
>>>
>>> The initial Unix TCP implementation was for TCP version 2 (2.5 IIRC), as
>>> was Jim's LSI-11 code.  This 2.5 implementation was one of the players
>>> in the first "TCP Bakeoff" organized by Jon Postel and carried out on a
>>> weekend at ISI before the quarterly Internet meeting.  The PDP-11/40 TCP
>>> was modified extensively over the next year or so as TCP advanced
>>> through 2.5, 2.5+, 3, and eventually stabilized at TCP4 (which it seems
>>> we still have today, 40+ years later!)
>>>
>>> The Unix TCP implementation required a small addition to the Unix kernel
>>> code, to add the "await" and "capac" system calls.  Those calls were
>>> necessary to enable the implementation of user-level code where the
>>> traditional Unix "pipeline" model of programming
>>> (input->process->process...->output) was inadequate for use in
>>> multi-computer programming (such as FTP, Telnet, etc., - anywhere where
>>> more than one computer was involved).
>>>
>>> The code to add those new system calls was written in C, as was almost
>>> all of the Unix OS itself.  The new system calls added the functionality
>>> of "non-blocking I/O" which did not previously exist.  It involved very
>>> few lines of code, since there wasn't room for very many more
>>> instructions, and even so it required finding more space by shortening
>>> many of the kernel error messages to save a few bytes here and there.
>>>
>>> Randy Rettberg and I did that work, struggling to understand how Unix
>>> kernel  internals worked, since neither of us had ever worked with Unix
>>> before even as a user.   We did not try to "get it right" by making
>>> significant changes to the basic Unix architecture.  That came later
>>> with the Berkeley and Gurwitz efforts.  The PDP-11/40 was simply too
>>> constrained to support such changes, and our mission was to get TCP
>>> support on the machine, rather than develop the OS.
>>>
>>> I think I speak authoritatively here, since I wrote and debugged that
>>> first Unix TCP code.   I still have an old, yellowing listing of that
>>> first Unix TCP.
>>>
>>> FWIW, if there's interest in why certain languages were chosen, there's
>>> a very simple explanation of why the Unix implementation was done in
>>> assembler rather than C, the native language of Unix.  First, Jim
>>> Mathis' code was in assembler, so it was easy to extract large chunks
>>> and paste them into the Unix assembler implementation.  Second, and
>>> probably most important, was that I was very accustomed to writing
>>> assembler code and working at the processor instruction level.  But I
>>> barely knew C existed, and was certainly not proficient in it, and we
>>> needed the TCP working fast for use in other projects.  The choice was
>>> very pragmatic, not based at all on technical issues of languages or
>>> superiority of any architecture.
>>>
>>> /Jack Haverty
>>>
>>>
>>> On 3/9/20 11:14 PM, vinton cerf via Internet-history wrote:
>>> > Steve Kirsch asks in what languages NCP and TCP were written.
>>> >
>>> > The Stanford first TCP implementation was done in BCPL by Richard Karp.
>>> > Another version was written for PDP-11/23 by Jim Mathis but not clear
>>> in
>>> > what language. Tenex was probably done in C at BBN. Was 360 done in
>>> PL/1??
>>> > Dave Clark did one for IBM PC (assembly language/??)
>>> >
>>> > Other recollections much appreciated.
>>> >
>>> > vint
>>> --
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>>
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