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Mean round-trip times in the ARPANET (RFC0619)

IP.com Disclosure Number: IPCOM000003691D
Original Publication Date: 1974-Mar-07
Included in the Prior Art Database: 2000-Sep-13
Document File: 11 page(s) / 29K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

W. Naylor: AUTHOR [+2]

Abstract

In one of our current measurement projects we are interested in the average values of important network parameters. For this purpose we collect data on the network activity over seven consecutive days. This data collection is only interrupted by down-time or maintenance of either the net or our collecting facility (the "late" Sigma-7 or, in future, the 360/91 at CCN).

This text was extracted from a ASCII document.
This is the abbreviated version, containing approximately 10% of the total text.

Network Working Group W. Naylor

Request for Comment: 619 H. Opderbeck

NIC 21990 UCLA-NMC

March 7, 1974

Mean Round-Trip Times in the ARPANET

In one of our current measurement projects we are interested in the

average values of important network parameters. For this purpose we

collect data on the network activity over seven consecutive days. This

data collection is only interrupted by down-time or maintenance of

either the net or our collecting facility (the "late" Sigma-7 or, in

future, the 360/91 at CCN).

The insight gained from the analysis of this data has been reported in

Network Measurement Group Note 18 (NIC 20793):

L. Kleinrock and W. Naylor

"On Measured Behavior of the ARPA Network"

This paper will be presented at the NCC '74 in Chicago.

In this RFC we want to report the mean round-trip times (or delays) that

were observed during these week-long measurements since we think these

figures are of general interest to the ARPA community. Let us first

define the term "round trip time" as it is used by the statistics

gathering program in the IMPs. When a message is sent from a source

HOST to a destination HOST, the following events, among others, can be

distinguished (T(i) is the time of event i):

T(1): The message is passed from the user program to the NCP in the

source HOST

T(2): The proper entry is made in the pending packet table (PPT) for

single packet messages or the pending leader table (PLT) for

multiple packet messages after the first packet is received by

the source IMP

T(3): The first packet of the message is put on the proper output

queue in the source IMP (at this time the input of the second

packet is initiated)

T(4): The message is put on the HOST-output queue in the destination

IMP (at this time the reassembly of the message is complete)

T(5): The RFNM is sent from the destination IMP to the source IMP

T(6): The RFNM arrives at the source IMP

T(7): The RFNM is accepted by the source HOST

The time intervals T(i)-T(i-1) are mainly due to the following delays

and waiting times:

T(2)-T(1): -HOST processing delay

-HOST-IMP transmission delay for the 32-bit leader

-Waiting time for a message number to become free (only

four messages can simultaneously be transmitted between

any pair of source IMP - destination IMP)

-Waiting time for a buffer to become free (there must be

...