[TUHS] Unix with TCP/IP for small PDP-11s

Paul Ruizendaal pnr at planet.nl
Tue May 23 21:35:02 AEST 2017


>> There are two other routes to TCP/IP on a PDP11 without split I/D:
>> ...
>> DCEC's adaptation of the Wingfield TCP/IP library, designed to work
>> with V6. It is mostly a user space daemon, but requires some kernel
>> enhancements.
> 
> I wonder what the performance would be like, since the TCP is in a user
> process (a different one from the application), i.e. there's a process switch
> every time the application goes to send or receive data. This wouldn't have
> been such an issue when the code was written, since ARPANet-type networks
> were not very fast, but with a better network, it would have been limiting.

IEN98 (http://www.rfc-editor.org/rfc/ien/ien98.txt, page 2) has the answer: about 10kb/s.

The DCEC version used shared memory instead of rand ports and was claimed to be
a bit more performant, but I have no number. I'd be surprised if it was twice as fast,
so perhaps 15kb/s.

Paul



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