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

On Tue, Mar 10, 2020 at 2:23 PM Warner Losh <imp(a)bsdimp.com> wrote: 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 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(a)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 >> -- >> Internet-history mailing list >> Internet-history(a)elists.isoc.org >> https://elists.isoc.org/mailman/listinfo/internet-history >> _______________________________________________ >> COFF mailing list >> COFF(a)minnie.tuhs.org >> https://minnie.tuhs.org/cgi-bin/mailman/listinfo/coff >> >