[TUHS] Re: when did v8 or later get networking?

[Paul Ruizendaal <pnr@planet.nl>]

Universal Receiver Protocol, the protocol that Sandy Fraser invented for Datakit. The best description of it (imho) is the patent:

https://patentimages.storage.googleapis.com/37/a9/70/46f8c44ebd4e3a/US4852127.pdf

At first the patent is very focused on hardware implementation, but towards the end it gives the algorithms in pseudo-code.

Sandy Fraser wrote a 1993 retrospective paper “Early Experiments with Asynchronous Time Division Networks”. This paper includes a short summary of the origins of the universal receiver protocol, and how it evolved through 3 main steps. Unfortunately behind a paywall.

The implementation for 8th edition (some 750 lines) is here:
https://www.tuhs.org/cgi-bin/utree.pl?file=V8/usr/sys/dev/dkp.c

I think early Plan9 had an implementation of URP as well.


> On 12 Aug 2023, at 17:24, Dan Cross <crossd@gmail.com> wrote:
> 
> On Sat, Aug 12, 2023 at 11:20 AM Warner Losh <imp@bsdimp.com> wrote:
>> On Sat, Aug 12, 2023, 4:29 AM Paul Ruizendaal <pnr@planet.nl> wrote:
>>>> URP is smaller, but if I remember well it does not handle out-of-order packets or packet duplicates (both of which do not occur in a (virtual) line switched context).
>>> 
>>> Upon reflection, duplicates of course can occur when an ACK is lost.
>> 
>> What's URP? Sounds a little like UDP, is it a typo or something else?
> 
> I thought that might be a typo for UDP, but that doesn't have ACKs.