[quagga-users 5667] Re: OT again, but still interesting

Matt Brown matt at mattb.net.nz
Wed Oct 19 10:40:33 IST 2005

On Tue, 2005-10-18 at 14:13 +0200, Ralf Guenthner wrote:

> Protocol is TCP. Files are transferred via ftp but also via Netbios e. 
> g. network shares. For latency I can only offer the fact that an average 
> ping reply is taking 8ms. The OSes involved include UNIX/Linux and Windows.

OK. 8ms is probably accurate enough for our purposes.

> Does that mean I have to change the TCP window sizes on the respective 
> hosts doing the transfer and/or on the two Linux routers as well? On one 
> of the sites you referred me to it says that the default window size of 
> Linux is 65535.

TCP is end to end so you need to adjust the window sizes on the two
hosts doing the transfer. The routers in the middle don't touch the TCP
connection at all (apart from routing the IP packets carrying the TCP

Two linux hosts should have no problems saturating a 10Mbps link with
8ms of latency. Even Windows 98 which only has a window size of 8192
bytes by default can theoretically transfer 8Mbps on such a link.
Increasing the window size is probably not going to hurt although I'm
less convinced that it is your problem  now. 

You might want to look into a utility such as tcptrace to perform a more
detailed diagnosis on the connection in question. 

This is probably getting really, really off topic for this list now :)


Matt Brown
matt at mattb.net.nz
Mob +64 275 611 544 www.mattb.net.nz

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