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From Colm MacCarthaigh <>
Subject Re: [users@httpd] Getting 5000 concurrent connections and 400 requests per second with Apache
Date Thu, 26 Jul 2007 21:06:37 GMT
On Tue, Jul 24, 2007 at 08:48:40PM +0200, Torsten Foertsch wrote:
> Please forgive me the stupid question but I thought a port number is a 16 bit 
> integer. How can one get more than 64k connections to one IP address then?

There's no port exhaustion involved, TCP stacks distinguish between
sockets based on source-ip source-port tuple. The destination port
remainds the same. Only if you get 64k connections from the same
source-ip would there be a problem.

That said, in one of our variants - as a reverse proxy - we did hit this
problem and just started using multiple IP addresses.

> Can you provide any more direct pointers to the papers you refer?

I think the most recent online version is at;

The main constrain is memory. Are you running out?

Colm MacCárthaigh                        Public Key:

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