Configuring TCP/IP tunable parameters

Using ifconfig to change parameters for a network card

You can use the ifconfig(ADMN) command to reconfigure performance parameters for a single network interface. If you wish to make this change permanent you must edit the entry for the interface in the /etc/tcp script.

The metric, onepacket, and perf parameters affect performance.

metric can be used to artificially raise the routing metric of the interface used by the routing daemon, routed(ADMN). This has the effect of making a route using this interface less favorable. For example, to set the metric for the sme0 interface to 10, enter:

/etc/ifconfig sme0 inet metric 10

onepacket enables one-packet at a time operation for interfaces with small buffers that are unable to handle continuous streams of back-to-back packets. This parameter takes two arguments that allow you to define a small packet size, and the number of these that you will permit in the receive window.
This deals with TCP/IP implementations that can send more than one packet within the window size for the connection. Set the small packet size and count to zero if you are not interested in detecting small packets. For example, to set one-packet mode with a small packet threshold of one small packet of 512 bytes on the e3A0 interface, enter:

/etc/ifconfig e3A0 inet onepacket 512 1

To turn off one-packet mode for this interface, enter:

/etc/ifconfig e3A0 inet -onepacket

perf allows you to tune performance parameters on a per-interface basis. The arguments to perf specify the receive and send window sizes in bytes, and whether TCP should restrict the data in a segment to a multiple of 1KB (a value of 0 restricts; 1 uses the full segment size).

The following example sets the receive and send window size to 4KB, and uses the maximum 1464-byte data size available in an Ethernet frame:

/etc/ifconfig sme0 inet perf 4096 4096 1

NOTE: Segment truncation does not change the size of the Ethernet frame; this is fixed at 1530 bytes.

Next topic: Using inconfig to change global TCP/IP parameters
Previous topic: Configuring TCP/IP tunable parameters

© 2003 Caldera International, Inc. All rights reserved.
SCO OpenServer Release 5.0.7 -- 11 February 2003