RFC 308 (rfc308) - Page 1 of 4

ARPANET host availability data

Network Working Group                   Marc Seriff
Request for Comments 308                MIT-DMCG
NIC 9259                                13 MARCH 1972
References: RFC 254

                     ARPANET HOST AVAILABILITY DATA

     Several months ago a SURVEY program was implemented on the
MIT-DMCG ITS PDP-10 system to aid in gathering information on the
availability of various HOSTS on the ARPANET.  The purpose of this
Request for Comments is threefold:

     1. to inform the Network Working Group of the
        existence of this information gathering service
        and about getting access to it,

     2. to present the results of SURVEY for its first
        few months, and

     3. to correct errors in our data or collection methods.

     Briefly, the SURVEY program works as follows: At 15-minute
intervals whenever the MIT-DMCG ITS Time-Sharing system is in normal
operation, a SURVEY is started.  The SURVEY program attempts to
establish a connection to the LOGGER (socket 1) of each HOST listed in
its table.  The results of each connection attempt are recorded for
future reference.  The Initial Connection Protocol is aborted prior to
reading the transmitted socket number so as to cause the minimum
amount of processing at SURVEYed HOSTS.  If the LOGGER connection
succeeds, the average request-for connection response time (in
seconds) for the HOST is updated.  This information can later be
viewed in several formats using the MIT-DMCG server TELNET "NETWRK" as
described below.

     Each test results in the assignment of one of the following
five statuses:

     1.  LOGGER available - connection completed.

     2.  LOGGER not responding - RFC sent (HOST-HOST OK), but
         no response (20 seconds allowed).

     3.  LOGGER rejecting - CLOSE returned by NCP.

     4.  NCP not responding - RESET timed out (15 seconds allowed).

     5.  HOST dead - host-dead status returned by IMP.