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  information about the behavior of ARPA network hosts
collected by DMS's program SURVEY . 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
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 . 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.