[TUHS] when did v8 or later get networking?

Paul Ruizendaal pnr at planet.nl
Sun Aug 13 02:12:32 AEST 2023

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


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:

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

> On 12 Aug 2023, at 17:24, Dan Cross <crossd at gmail.com> wrote:
> On Sat, Aug 12, 2023 at 11:20 AM Warner Losh <imp at bsdimp.com> wrote:
>> On Sat, Aug 12, 2023, 4:29 AM Paul Ruizendaal <pnr at 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.

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