Internet Delay Experiments (RFC0889)
Original Publication Date: 1983-Dec-01
Included in the Prior Art Database: 2019-Feb-13
Internet Society Requests For Comment (RFCs)
This memo reports on some measurements of round-trip times in the Internet and suggests some possible improvements to the TCP retransmission timeout calculation. This memo is both a status report on the Internet and advice to TCP implementers.
Network Working Group D.L. Mills Request for Comments: 889 December 1983
Internet Delay Experiments
This memo reports on some measurement experiments and suggests some possible improvements to the TCP retransmission timeout calculation. This memo is both a status report on the measurements and advice to implementers of TCP.
This memorandum describes two series of experiments designed to explore the transmission characteristics of the Internet system. One series of experiments was designed to determine the network delays with respect to packet length, while the other was designed to assess the effectiveness of the TCP retransmission-timeout algorithm specified in the standards documents. Both sets of experiments were conducted during the October - November 1983 time frame and used many hosts distributed throughout the Internet system.
The objectives of these experiments were first to accumulate experimental data on actual network paths that could be used as a benchmark of Internet system performance, and second to apply these data to refine individual TCP implementations and improve their performance.
The experiments were done using a specially instrumented measurement host called a Fuzzball, which consists of an LSI-11 running IP/TCP and various application-layer protocols including TELNET, FTP and SMTP mail. Among the various measurement packages is the original PING (Packet InterNet Groper) program used over the last six years for numerous tests and measurements of the Internet system and its client nets. This program contains facilities to send various kinds of probe packets, including ICMP Echo messages, process the reply and record elapsed times and other information in a data file, as well as produce real-time snapshot histograms and traces.
Following an experiment run, the data collected in the file were reduced by another set of programs and plotted on a Peritek bit-map display with color monitor. The plots have been found invaluable in the indentification and understanding of the causes of netword glitches and other "zoo" phenomena. Finally, summary data were extracted and presented in this memorandum. The raw data files, including bit-map image files of the various plots, are available to other experimenters upon request.
The Fuzzballs and their local-net architecture, called DCN, have about two-dozen clones scattered worldwide, including one (DCN1) at the Linkabit Corporation offices in McLean, Virginia, and another at the Norwegian Telecommunications Adminstration (NTA) near Oslo, Norway. The DCN1 Fuzzball is connected to the ARPANET at the Mitre IMP by means of 1822 Error Control Units operating over a 56-Kbps line. The NTA Fuzzball is connected to the NTARE Gateway by an 1822 interface and then via VDH/HAP operating over a 9.6-Kbps line to SATNET at the Tanum (Sweden) SIMP. For most experiments described below, these details of the local connectivity can be ignored, since only relatively small delays are involved...