12 Aug
2023
12 Aug
'23
10:12 p.m.
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/US48521…
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(a)gmail.com> wrote:
On Sat, Aug 12, 2023 at 11:20 AM Warner Losh <imp(a)bsdimp.com> wrote:
On Sat, Aug 12, 2023, 4:29 AM Paul Ruizendaal
<pnr(a)planet.nl> wrote:
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. 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.