Window Size

[pushpak.lele]

can we spcify window size on interface?

[Danilo Dy]

Hi,

From the system side, there is a way to optimize the TCP Protocol Stack. In Windows, this can be done by editing the REGISTRY. There is an available utility for Windows which is called "TCP Optimizer", Google it - use it in your own risk.

From the network side, Jumbo/Giant Frames (up to 9000 MTU) is supported in some Switch models. There are servers (NICs) and softwares that supports Jumbo/Giant Frames as well. Jumbo/Giant Frames are very useful in Database/Backup Environment

Jumbo/Giant Frames

http://www.cisco.com/en/US/products/hw/switches/ps700/products_configuration_example09186a008010edab.shtml

Jumbo frames should be set only if all the components in the network configuration support jumbo frames from source to destination. For example;

Apps Server | Switch | Database Server

All Servers | Switch | Backup Server

Regards,

Dandy

[Joseph W. Doherty]

If you're thinking of Cisco routers, don't believe so per interface, but you often can enlarge the TCP receive window globally. (Does seems to speed up FTP flash upgrades across high BDP links.) Not sure about Cisco switches. Those running L3 might also support a global TCP window setting.

When it comes to hosts, believe it depends on the implementation. Also believe Danilo is correct, that for Windows hosts it can be defined per interface, along with globally (or set by the socket, I recall).

Also for Windows, Windows defaults vary based on the interface speed. Further, Vista's defaults are much different from prior Windows' versions. Besides usually being larger, they activate large window support (> 64 KB), which can be manually activated on some of prior Windows TCP implementations.