From mboxrd@z Thu Jan 1 00:00:00 1970 From: imp at bsdimp.com (Warner Losh) Date: Tue, 10 Mar 2020 12:23:41 -0600 Subject: [COFF] Fwd: [ih] NCP and TCP implementations In-Reply-To: References: Message-ID: >>> 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? >>> 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... Warner On Tue, Mar 10, 2020 at 11:52 AM Clem Cole 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 at elists.isoc.org > https://elists.isoc.org/mailman/listinfo/internet-history > _______________________________________________ > COFF mailing list > COFF at minnie.tuhs.org > https://minnie.tuhs.org/cgi-bin/mailman/listinfo/coff > -------------- next part -------------- An HTML attachment was scrubbed... URL: