We have an ASA 5550 v8 installed to provide nothing more than one to one dynamic nat in a large college residence hall. (One public IP is reserved for PAT in the event that the public one to one pool is depleted).
As a college residence facility, we get a good number of copyright violations and need to maintain logs that enable us to associate a user with an private IP and its translated public IP.
We keep the xlate timeout short and for the most part the logs are easy to work with.
The exception appears to be when our users establish a connection with bitorrent. Even after the computer that initiates the connection leaves the network, the connection persists. Aside from making sorting through logs problematic it has other odd effects such as generating arp traffic for hosts that are no longer on the network.
From my readings, this type of connection is sometimes describes as "half-open" as opposed to embryonic.
Any direction to a web page that would provide some clarification about managing half-open v embryonic connectiuons, or some other pointers on how to terminate these half-open connections would be appreciated.