RFC 406

Scheduled IMP Software Releases ✨

okay bestie, so this is RFC 406 💖 written by John M. McQuillan at Bolt Beranek and Newman (NIC 12111), dated 10 October 1972. It's a Category B.1 doc 🎀 and it updates RFC 381, which is the one with the original scheduling procedures for IMP software maintenance 🦋

The vibe: RFC 381's procedures have been in effect for about two months now, and two things need a re-emphasis 💅

1. ngl this one is important 😭 We reserve the hour from 7 to 8 a.m. eastern time every Tuesday as the time when IMPs can be reloaded. We probably won't use that window every Tuesday, but we DO reserve it every Tuesday 🧚 And the software maintenance time is in addition to the hardware preventive maintenance scheduled at each site 🌸
2. this is giving communication 🫶 We now send an IMP - Going - Down message to all the Hosts at the site. It tells them when the IMP is going down, how long it'll be down, and why. We try to send it an hour before software releases, and five to ten minutes before scheduled preventive maintenance. We'll also notify the Hosts at a site whenever possible if the IMP has to stop on an unscheduled basis 👑 Then, 30 seconds before the IMP actually goes down, a second IMP - Going - Down message gets sent, saying it's going down immediately 💀

Here's the message format, and yes it's a whole thing 🍓

bits 1 - 4  -  all zero

bits 5 - 8  -  0010

bits 9 - 16 -  all zero

bits 17 - 32 -  coded as follows:


          All bits zero - going down in 30 seconds



          Bits 17, 18 = 01 - scheduled hardware PM

          Bits 17, 18 = 10 - scheduled software reload

          Bits 17, 18 = 11 - emergency reload on restart



          Bits 19 - 22 - how soon the IMP is going down,
                         in 5 minute units.



          Bits 23 - 32 - how long the IMP will be down, in
                         5 minute units.

bestie, bits 17 through 32 are where the reason and timing live, so don't skip them 🙈

[ This RFC was put into machine readable form for entry ] [ into the online RFC archives by BBN Corp. under the ] [ direction of Alex McKenzie. 1/97 ]