How to modify TCP WINDOWS value in HP-UX

[KNC]

I want to modify the TCP WINDOWS value of a server and i don't know how it can be done. The HP-UX version installed is 11iV2.
Thanks

[Ivan Krastev]

Use ndd - http://docs.hp.com/en/B2355-90681/ndd.1M.html

For permanent changes add entries in /etc/rc.config.d/nddconf


regards,
ivan

[Andrew Young_2]

Hi.

You can list the supported (configurable) parameters by using:

ndd -h sup

You can set them using:

ndd -set

To make the changes permanant add the changes to /etc/rc.config.d/nddconf.

HTH.

Andrew Y

[SANTOSH S. MHASKAR]

Hi,

Use following command,

# ndd -set /dev/tcp


-Santosh

[George Liu_4]

ndd

[Jim Keeble]

The specific parameters you want to look at in most cases are:

tcp_xmit_hiwater_def
tcp_recv_hiwater_def

The default is 32K.

The best way to change the transmit and receive socket sizes is for the application to handle it using setsockopt() calls for the SO_SNDBUF and SO_RCVBUF settings, because changing the system default will use the larger buffers even for applications that don't need them. But if the application code can't be changed, and it doesn't already use the call to set a small buffer size, this parameter is an alternative.

The application will have to be retarted to take advantage of the new sizes, i.e., they only apply to new sockets.

Hope this helps. If you are using a high speed link like hyperfabric or infiniband, look at tcp_xmit_hiwater_lfp and tcp_recv_hiwater_lfp instead.

lfp = Long Fat Pipe.