performance: tcp window size not effective

[Brem Belguebli]

Hi,

I have a ftp transfer (4 GB of gzipped data) between 2 HP-UX boxes (IA 64 11iv2 and PA 11i) distant by 270 ms over a DS3 WAN.

Transfers do not go over 2Mb/s even after raising tcp window (recv and xmit) size to 157286 on both sides . (ndd -set /dev/tcp tcp_xmit_hiwater_def and tcp_recv_hiwater_def

When tcpdumping the connection I see a 39321 window size . Both machines are connected to the LAN with Gb fiber cards.

Ftpd is HP-Ux 11iv2 wu-ftp 2.6.1 (PHNE 34036).

Any idea ?

[Steven Schweda]

> [...] HP-UX [...]

You might get better answers faster in an
HP-UX forum than you will in this Tru64 forum.

http://forums1.itrc.hp.com/service/forums/familyhome.do?familyId=117

[Brem Belguebli]

yes,

Already done.

Thx

[Brem Belguebli]

Hi,

Still limited transfer rate to max 2Mb/s even if I have found out the "window scale" parameter to go over the 16 bits limit of the windows size TCP option.

[Ivan Ferreira]

Slow transfers rate normally are caused by incorrect speed/duplex negotiation between the switch and the network adapter.

Hoping you use Tru64 V5, you can check the current speed and duplex configuration with:

hwmgr get attr -cat network | grep -E "name|speed|duplex|auto"

If you manually set the switch speed to 100 MB FD, then force it also in the operating system:

/usr/sbin/lan_config -i -x 1 -s 100 -a 0

Add that line to /etc/inet.local also so it's persistent across reboots.

Speed and duplex problems cause slow tranfer rate and also, a lot of errors/collisions in the output of:

netstat -ni

Welcome to the forum and don't forget to assign points to the answers you get.

Have a nice day.