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Simulation Studies of Increased Initial TCP Window Size (RFC2415)

IP.com Disclosure Number: IPCOM000002991D
Original Publication Date: 1998-Sep-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 8 page(s) / 22K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

K. Poduri: AUTHOR [+2]

Abstract

An increase in the permissible initial window size of a TCP connection, from one segment to three or four segments, has been under discussion in the tcp-impl working group. This document covers some simulation studies of the effects of increasing the initial window size of TCP. Both long-lived TCP connections (file transfers) and short-lived web-browsing style connections were modeled. The simulations were performed using the publicly available ns-2 simulator and our custom models and files are also available.

This text was extracted from a ASCII Text document.
This is the abbreviated version, containing approximately 13% of the total text.

Network Working Group K. Poduri

Request for Comments: 2415 K. Nichols

Category: Informational Bay Networks

September 1998

Simulation Studies of Increased Initial TCP Window Size

Status of this Memo

This memo provides information for the Internet community. It does

not specify an Internet standard of any kind. Distribution of this

memo is unlimited.

Copyright Notice

Copyright (C) The Internet Society (1998). All Rights Reserved.

Abstract

An increase in the permissible initial window size of a TCP

connection, from one segment to three or four segments, has been

under discussion in the tcp-impl working group. This document covers

some simulation studies of the effects of increasing the initial

window size of TCP. Both long-lived TCP connections (file transfers)

and short-lived web-browsing style connections were modeled. The

simulations were performed using the publicly available ns-2

simulator and our custom models and files are also available.

1. Introduction

We present results from a set of simulations with increased TCP

initial window (IW). The main objectives were to explore the

conditions under which the larger IW was a "win" and to determine the

effects, if any, the larger IW might have on other traffic flows

using an IW of one segment.

This study was inspired by discussions at the Munich IETF tcp-impl

and tcp-sat meetings. A proposal to increase the IW size to about 4K

bytes (4380 bytes in the case of 1460 byte segments) was discussed.

Concerns about both the utility of the increase and its effect on

other traffic were raised. Some studies were presented showing the

positive effects of increased IW on individual connections, but no

studies were shown with a wide variety of simultaneous traffic flows.

It appeared that some of the questions being raised could be

addressed in an ns-2 simulation. Early results from our simulations

were previously posted to the tcp-impl mailing list and presented at

the tcp-impl WG meeting at the December 1997 IETF.

2. Model and Assumptions

We simulated a network topology with a bottleneck link as shown:

10Mb, 10Mb,

(all 4 links) (all 4 links)

C n2_________ ______ n6 S

l n3_________\ /______ n7 e

i \\ 1.5Mb, 50ms // r

e n0 ------------------------ n1 v

n n4__________// \ \_____ n8 e

t n5__________/ \______ n9 r

s s

URLs --> <--- FTP & Web data

File downloading and web-browsing client...