[OT] Handling multiple UDP clients through NAT

plug.org at 2nerds.com plug.org at 2nerds.com
Tue Feb 6 18:05:52 MST 2007

On Tue, 6 Feb 2007, Bryan Sant wrote:
> You can't.  You can only handle 2^16 - n TCP connections at the same
> time.

Where does this limitation come from?  One might be tempted to relate the 
maximum number of TCP connections to the 16-bit size of a TCP port number, 
but that doesn't work because TCP connections are typically identified by 
a four-tuple which includes the source and destination IP addresses as 
well as the source and destination port numbers.  In theory, a TCP stack 
with only a single bound IP address can maintain ~64K independent 
connections to _every_ peer even when using only a single local port, so 
I'm guessing the 2^16 - n number must be coming from some other 
implementation-dependent limitation.  Or am I just up in the night? :-)


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