[Pound Mailing List] When does pound decide to that the backend is "dead"?

I was doing a test of removing web servers from my backend to force the
load of the remaining web servers to go up and I noticed that I hit a point
where the remaining web servers were so overloaded that they fell out of
the load balancer.

These web servers were up and still capable of taking more load.  But pound
had removed them and put them right back in.

This is a problem because I use sticky sessions based on JsessionID, so if
pound removes a web server and puts it right back in, load does not go back
to that web server because the JsessionID has already been assigned to
another web server.

My question is:  How does pound determine that a backend web server is
"dead" (enough to remove it from the list and then add it right back in).

I have "TimeOut" set to 120.   And according to my logs the requests were
not hitting a 2 minute limit, so that's not it.

So how slow does the backend web server have to be before pound says that's
it's "dead" and removes it?

-brad