topic Re: UCX in Operating System - OpenVMS

UCX

Sunil_uk — Wed, 05 Oct 2005 06:01:04 GMT

Can someone give a clue about the "quota"
in the output of UCX SHOW PORTOCOL TCP/PARAMETERS?. How it is affecting the performance?.

Sunil

Re: UCX

Wim Van den Wyngaert — Wed, 05 Oct 2005 06:44:20 GMT

"TCP also provides flow control. Each end of a TCP connection has a finite amount of buffer space. A receiving TCP only allows the other end to send as much data as the receiver has buffers for. This prevents a fast host from taking all the buffers on a slower host."

Note that this is a default value. Each program can overrule it. Use ucx show dev/fu to see the active values.

FTP benefits a lot with it on a slow network.

Also read this.
http://www.thinkingsecure.com/docs/TCPIP-Illustrated-1/tcp_int.htm#19_0

Wim

Re: UCX

Wim Van den Wyngaert — Wed, 05 Oct 2005 07:32:38 GMT

And you can set it at service level too (e.g. ftp). But it is up to the program to pick up that value so check if it was really used.

It can also be decreased to a low value to decrease the ftp thruput (e.g. to save the network from being overload).

BTW : not sure what the "total" fields stand for. Are there 4 buffers possible ???

Wim

Re: UCX

Michael Yu_3 — Wed, 05 Oct 2005 19:07:50 GMT

Hi Sunil,

The quota in the output of UCX show protocol TCP/param are the TCP send and receive window sizes.

Thanks and regards.

Michael