RFC 611 (rfc611) - Page 2 of 4

Two changes to the IMP/Host Protocol to improve user/network communications

RFC 611               Changes to IMP/Host Protocol         February 1974


All three of the above or to be specified in Universal time (i.e.,
G.M.T.).  The Host may indicate that it will be coming back up more than
a week away by setting bits 17-28 all to ones.  Setting all bits 17-27
to one and bit 28 to zero means it is unknown when the host is coming
back up.

    Bits 29-32 of the Host-Going-Down message should be used by the Host
to specify the reason it is going down.  These bits are coded as
follows:

Value     Meaning
-----     -------

0-4       Reserved for IMP use (see Section 3 below)
5         Scheduled P.M.
6         Scheduled Hardware Work
7         Scheduled Software Work
8         Emergency Restart
9         Power Outage
10        Software Breakpoint
11        Hardware Failure
l2-15     Currently Unused

    It is assumed that as the time for the Host to go down approaches,
the Host itself will send warning messages to its network users.  Just
before going down, the Host should send the Host-Going-Down message to
its IMP.  The IMP will store this message and return it to the source
Host along with Destination (Host) Dead messages.  The IMP will try to
preserve this message over IMP reloads where appropriate.  The NCC will
be able to update manually the stored copy of this message in response
to a phone call from the Host site in the event the Host is going to be
down longer than it said or if it didn't have time to say before going
down.

3.  Addition of the Dead Host Status Message

    The type 7, destination dead, message described on page 3-16 of BBN
Report 1822, does not allow for providing the reason for the Destination
Host's being "dead".  An additional IMP to Host message is therefore
being added which provides status information on the dead Host.  This
message is type 6, Dead Host Status, and will provide the additional
information as follows:

    Bits 17-28 have the same meanings as bits 17-28 in the Host-Going-
    Down message described in Section 2 above.






Walden