RFC 381 (rfc381) - Page 2 of 4
Three aids to improved network operation
Alternative Format: Original Text Document
RFC 381 Three Aids To Improved Network Operation 26 July 1972
2. IMP-to-Host Communication
There have long been complaints that the IMP-to-Host error messages
were not precise enough or were just plain ambiguous. In RFC #312 we
proposed some additional error messages. These and other IMP-to-Host
message changes will be made on August 14, 1972 and we encourage
Hosts to modify their NCP's as appropriate by then. Unmodified NCPs
will probably continue to work after this change, but each site
should look into this question carefully. The table below lists all
the IMP-to-Host messages and clearly indicates the changes which will
be made.
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
Mc Quillan, et. al.