[p2p-hackers] UDP Keep-alive

coderman coderman at peertech.org
Tue Jan 11 21:01:33 UTC 2005

Travis Kalanick wrote:

>Anybody have a good idea how long the average NAT/Gateway keeps alive a UDP
 From my personal experience: (meaning yours may vary :)

Most NAT's appear to give a 1-5 minute timeout since last
packet seen.  It would be nice to find a market summary of
various NAT behaviors.  Anyone know of such a thing?

The timeout is trivial to avoid with loose UDP NAT (simply
send / recv a packet from any peer within the few minute
window).  For symmetric NAT it is more of a pain. Each
session must send traffic within the timeout window which
raises overall communication significantly for large numbers
of logical NAT-UDP connections.


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