Optimizing Operating Systems for High Latency Networks

David Pashley

Revision History
Revision 0.1 20 May 2002
First draft

Table of Contents

Linux 2.4

Abstract

Most operating systems are not configured with High Latency networks in mind. The effect of this is that maximum downloads are constrained by the latency. This tutorial will show you how to improve network performance over high latency networks.

Linux 2.4

Timestamping, Selective Acknowledgements and Window Scaling are enabled by default. so al that needs to be done is to change the TCP Window Size. This setting can be changed using the /proc/sys/net/ipv4/tcp_rmem and /proc/sys/net/ipv4/tcp_rmem files. These files contain 3 values in min default max order. The defaults are below.

david root% cat /proc/sys/net/ipv4/tcp_rmem
4096    87380   174760
david root% cat /proc/sys/net/ipv4/tcp_wmem
4096    16384   131072
david root% 

Table 1. Default settings

File Minimum Default Maximum
tcp_rmem 4K 85K 170K
tcp_wmem 4K 16K 128K