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Increasing TCP's Initial Window (RFC2414)

IP.com Disclosure Number: IPCOM000002990D
Original Publication Date: 1998-Sep-01
Included in the Prior Art Database: 2000-Sep-13
Document File: 11 page(s) / 30K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

M. Allman: AUTHOR [+3]

Abstract

This document specifies an increase in the permitted initial window for TCP from one segment to roughly 4K bytes. This document discusses the advantages and disadvantages of such a change, outlining experimental results that indicate the costs and benefits of such a change to TCP.

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

Network Working Group M. Allman

Request for Comments: 2414 NASA Lewis/Sterling Software

Category: Experimental S. Floyd

LBNL

C. Partridge

BBN Technologies

September 1998

Increasing TCP's Initial Window

Status of this Memo

This memo defines an Experimental Protocol for the Internet

community. It does not specify an Internet standard of any kind.

Discussion and suggestions for improvement are requested.

Distribution of this memo is unlimited.

Copyright Notice

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

Abstract

This document specifies an increase in the permitted initial window

for TCP from one segment to roughly 4K bytes. This document

discusses the advantages and disadvantages of such a change,

outlining experimental results that indicate the costs and benefits

of such a change to TCP.

Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",

"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this

document are to be interpreted as described in RFC 2119 [RFC2119].

1. TCP Modification

This document specifies an increase in the permitted upper bound for

TCP's initial window from one segment to between two and four

segments. In most cases, this change results in an upper bound on

the initial window of roughly 4K bytes (although given a large

segment size, the permitted initial window of two segments could be

significantly larger than 4K bytes). The upper bound for the initial

window is given more precisely in (1):

min (4*MSS, max (2*MSS, 4380 bytes)) (1)

Equivalently, the upper bound for the initial window size is based on

the maximum segment size (MSS), as follows:

If (MSS <= 1095 bytes)

then win <= 4 * MSS;

If (1095 bytes < MSS < 2190 bytes)

then win <= 4380;

If (2190 bytes <= MSS)

then win <= 2 * MSS;

This increased initial window is optional: that a TCP MAY start with

a larger initial window, not that it SHOULD.

This upper bound for the initial window size represents a change from

RFC 2001 [S97], which specifies that the congestion window be

initialized to one segment. If implementation experience proves

successful, then the intent is for this change to be incorporated

into a revision to RFC 2001.

This change applies to the initial window of the connection in the

first round trip time (RTT) of transmission following the TCP three-

way handshake. Neither the SYN/ACK nor its acknowledgment (ACK) in

the three-way handshake should increase the initial window size above

that outlined in equation (1). If ...