Cisco Systems 78-11741-02 Enabling TCP Time Stamp, Setting the TCP Maximum Read Size, IPC-114

Configuring IP Services

Configuring TCP Performance Parameters

Enabling TCP Time Stamp

The TCP time-stamp option provides better TCP round-trip time measurements. Because the time stamps are always sent and echoed in both directions and the time-stamp value in the header is always changing, TCP header compression will not compress the outgoing packet. To allow TCP header compression over a serial link, the TCP time-stamp option is disabled.

Refer to RFC 1323 for more detailed information on TCP time stamp.

To enable TCP time stamp, use the following command in global configuration mode:

Command	Purpose
Router(config)# ip tcp timestamp	Enables TCP time stamp.

If you want to use TCP header compression over a serial line, TCP time stamp and TCP selective acknowledgment must be disabled. Both features are disabled by default. To disable TCP selective acknowledgment once it is enabled, see the previous “Enabling TCP Selective Acknowledgment” section.

Setting the TCP Maximum Read Size

By default, for Telnet and rlogin, the maximum number of characters that TCP reads from the input queue at once is a very large number (the largest possible 32-bit positive number). We do not recommend that you change this value. However, to change that value, use the following command in global configuration mode:

Command	Purpose
Router(config)# ip tcp chunk-size	Sets the TCP maximum read size for Telnet or rlogin.
characters

Setting the TCP Window Size

The default TCP window size is 2144 bytes. We recommend you keep the default value unless you know your router is sending large packets (greater than 536 bytes). To change the default window size, use the following command in global configuration mode:

Command	Purpose
Router(config)# ip tcp window-size	Sets the TCP window size.
bytes

Cisco IOS IP Configuration Guide

IPC-114