[TUHS] Datakit early end-to-end protocol(s)

Paul Ruizendaal pnr at planet.nl
Sat Feb 15 02:22:37 AEST 2020

I’m looking for the end-to-end datakit network protocol as it existed in 7th Edition.

Context is as follows:

- The Spider network guaranteed reliable, in-order delivery of packets at the TIU interface. There does not seem to have been a standard host end-to-end protocol, although applications did of course contain sanity checks (see for instance the ‘nfs’ source here: http://chiselapp.com/user/pnr/repository/Spider/tree?ci=tip)

- Datakit dropped the reliable delivery part (although it did retain the in-order guarantee) and moved this responsibility to the host. It is the (early) evolution of the related protocol that I’m trying to dig up.

- 7th Edition appears to have had a (serial line based) Datakit connection. Datakit drivers are not in the distributed files, but its tty.h file has defines for several Datakit related  constants. Also, as the first Datakit switches became operational at Murray Hill in ’78 or ’79, it seems a reasonable assumption that the Research code base included drivers & protocols for it around that time.

- After that the trail continues with the 8th edition which has a stream filter (dkp.c) for the “New Datakit Protocol”: http://chiselapp.com/user/pnr/repository/v8unix/artifact/01b4f6f05733aba5  This suggests that there was an “Old Datakit Protocol” as well - if so, this may have been the protocol in use at the time of 7th Edition.

The “New Datakit Protocol” appears to be (more or less) the same as what was later called URP (Universal Receiver Protocol). At the time of Plan9 its IL/IP protocol appears to have been designed as an equivalent for URP/Datakit. The early protocols where apparently (co-)designed by Greg Chesson and maybe also stood at the base of his later XTP protocol work.

Any recollections about the early history and evolution of this Datakit protocol are much appreciated. Also, if the source to the 7th Edition Datakit network stack survived I’d love to hear.


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