RFC 381
Three aids to improved network operation
RFC 381 is from the Network Working Group, written by J. McQuillan and D. Walden at Bolt Beranek and Newman Inc. It's dated 26 July 1972 and has NIC number 11151. The header doesn't list a category or status, and it doesn't say it obsoletes or updates anything. It's three little fixes for running the network better, and it's giving "we're cooking" energy 🧚💖
1. Scheduled Software Maintenance
Okay so the ARPA Network got SO big, and now it's hard to find a time to slide new software in without wrecking someone's day 😭 There's always intrasite traffic between the machines at MIT, and there's almost always traffic between the AMES TIP and IMP. The sun literally never sets on this network 🌞 So to cut down on surprise disruptions while still getting our work done, we want to schedule 7 A.M. - 8 A.M. eastern time every Tuesday as a window where the IMPs can be reloaded. We probably won't use that window every single Tuesday, but we're reserving it every Tuesday anyway 🎀 This is on top of the several hours a month each site already has scheduled for hardware preventative maintenance.
Bestie, not everyone knows when their machine is going down for maintenance, and some people forget and just keep working through that Tuesday morning software window 🙈 So we want to level up the IMP-Going-Down IMP-to-Host control message so it can remind users too. The message (we'll get into the details below) will say that the IMP is going down in m times five minutes, for n times 5 minutes, for a given reason. Hosts (and the TIP) should use that info to remind all their Network users that the IMP will go down after the stated interval 💅
Sometimes there's an emergency and an IMP has to be restarted or reloaded. For example, three Hosts at a site are doing fine, but one Host can't talk to the IMP at all 😬 That kind of situation can mean the IMP has to restart. A restart like that gets preceded by an IMP-Going-Down Message a few minutes ahead, so working users can save their stuff and get back in once the IMP is up again 💾
In both of these cases, and also when an IMP is performing so poorly that it must be shut down quickly, a type 2 IMP-to-HOST message gets sent to the HOST about 30 seconds before the IMP goes down ⏳ And yes, sometimes the IMP crashes so fast there's no warning at all. But the IMP will never be shut down on purpose that way 🫶
2. IMP-to-Host Communication
Okay, the people have been complaining for ages that the IMP-to-Host error messages weren't precise enough, or were just plain confusing 🙃 In RFC #312 we proposed some extra error messages. These and other IMP-to-Host message changes go live on August 14, 1972, and we're encouraging Hosts to update their NCPs as needed before then 🗓️ NCPs that aren't updated will probably keep working after the change, but each site should look into this carefully. The table below lists every IMP-to-Host message and clearly shows what's changing 👑
Type Old Meaning New Meaning
0 Regular Messages Same
1 Error without Error in Leader of Host-to-
identification IMP Message
Bits 31,32=00 - IMP's
error flip-flop set on
the first 32 bits of a
Host-to-IMP message which
the IMP therefore cannot
identify
Bits 31,32=01 - Host-to-IMP
message too short (less
than 32 bits)
Bits 31,32=10 - illegal
Host-to-IMP code
2 IMP Going Down IMP Going Down
Bits 17-32 coded as follows:
All bits zero - going down in
30 sec.
Bits 17,18=01 - scheduled
hardware PM
Bits 17,18=10 - scheduled
software reload
Bits 17,18=11 - emergency
reload or 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
3 Blocked Link Unassigned
4 NOF Same
5 RFNM Same
6 Link Table Full Unassigned
7 Destination Dead Destination Dead
Bit 32=0 - the destination
IMP is dead, or cannot be
reached, or does not exist
Bit 32=1 - the destination
Host is dead or does not
exist
8 Error with identi- Error in Data of Host-to IMP
fication Message
IMP's error flip-flop set
on the data bits of a Host-
to-IMP message identified
by the given source and link
9 Incomplete Transmission Incomplete Transmission
Bits 31,32=00 - the destination
Host did not take the message
for a long time
Bits 31,32=01 - Host-to-IMP
message too long (more
than 8095 bits)
Bits 31,32=10 - Host-to IMP
message too slow. The
last message took more
than 15 secs. between
the first bit and the
last bit, and was discarded
Bits 31,32=11 - Host-to-
IMP message lost in the
subnet
10 Unassigned IMP-Host Interface Reset
The IMP's ready line has
been dropped and pending
output to the Host discarded
(probably because the Host
has not taken messages from
the IMP for a long time).
The IMP will return a type 1
message of subtype 0 at the
completion of the next Host-
to-IMP message.Here's the TL;DR of these changes 🍓
- There's now one and only one IMP-to-Host message in response to each Host-to-IMP regular message.
- Message types 1, 2, 7 and 9 now carry additional information.
- Message type 10 has been added.
- Message types 3 and 6 have been discarded.
3. Network News Service
We've launched a Network news service, and it's lowkey so cute 📰 TIP users can get the news by typing the TIP command @NEWS. Users on other Hosts can get the news by ICPing to socket 15600031 (octal) at the BBN Tenex 🦋
If you have more ideas for making the Network run better, we want to hear your comments 💜
[ This RFC was put into machine readable form for entry ] [ into the online RFC archives by Lorrie Shiota 08/00]
📦 where this page comes from
- ietf: rfc381 1972-07
- 💖 girlified by claude-haiku-5-5 on : a language model's rewrite of the original, under its terms