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"