Network Working Group                                          D. Cantor
Request for Comments: 565                Computer Corporation of America
NIC: 18777                                                28 August 1973


            Storing Network Survey Data at the Datacomputer

   In November, 1972, Computer Corporation of America (CCA) and the
   Programming Technology Division of the Dynamics Modeling System (DMS)
   at M.I.T.'s Project MAC began planning to transmit to CCA's
   datacomputer [1] information about the behavior of ARPA network hosts
   collected by DMS's program SURVEY [2].  The information was to be
   stored at the datacomputer and retrieved by an interactive program
   that would address the datacomputer from DMS's PDP-10.

   One goal of this joint project was to enable DMS to retain all of the
   information that SURVEY collects: SURVEY had been running since late
   1971, saving only a short daily summary of its findings and
   discarding potentially useful details.  A second goal was to discover
   and remove shortcomings in the interface between CCA's datacomputer
   and a program running at a remote host.

   The project was completed last month, and the programs described in
   this document have been operating successfully with the datacomputer
   since July 10.

   Part 1, below, describes SURVEY's output.  Part 2 describes a program
   that retrieves portions of that output from the datacomputer.

Part 1: The Survey Database

   Every twenty minutes, DMS's program SURVEY wakes up and performs the
   initial connection protocol from the PDP-10 at DMS to the logger
   socket (socket 1) of each 28 network hosts.

   SURVEY records a date time, host, status,and response time for each
   host.  A host may be in one of these states:

      undetermined or not surveyed

      disconnect from the network or dead

      network control program not responding

      ICP to logger aborted by the host

      ICP to logger timed out by SURVEY after 20 seconds




Cantor                                                          [Page 1]

RFC 565               Storing Network Survey Data         28 August 1973


      logger available and responding within 20 seconds

   SURVEY records response times responding in tenths of seconds.

   When the data for all 28 hosts has been assembled, SURVEY transmits
   that data to CCA's datacomputer.  If for some reason the datacomputer
   cannot accept the information, it is held at DMS and sent another
   time.

   The datacomputer's survey database is inverted by host, status,
   month, and year.  That is to say that the datacomputer maintains
   several indices to records of one attempt to establish a full duplex
   connection to one host's logger: it maintains one such index for each
   host, one for each status, one for each month, and one for each year.
   The datacomputer can select records that are specified in boolean
   expressions by performing boolean operations on the inversion, and
   without consulting the data itself.  The inversion thus facilitates
   rapid interaction between the survey retrieval program described
   below and the survey database at the datacomputer.

   SURVEY expresses the record of each attempt to access one host in 17
   ASCII characters.  The record of one survey then occupies 17 * 28 =
   476 characters, and each day the datacomputer receives 3 * 24 * 476 =
   34,272 characters from DMS.

Part 2: Retrieving Survey Data

   A Program called SURRET, written at DMS in the language MUDDLE,
   allows one to selectively retrieve material from the survey data base
   stored at the datacomputer [3].  Its user may specify values, groups
   of values, or, where appropriate, upper and lower bounds for values
   of each of five fields: host name, date, time, response time, and
   host status.  In addition, one may request that all five fields or
   any subset of the five be retrieved.  A sample interaction with
   SURRET is reproduced below.

    $
    "OK"
    $
    "OK"