Hi Amar,
Leasing is used by a Remoting server to detect network failures. A ping is periodically sent from the client to the server, and, if the ping doesn't arrive within a specified window, the server informs any registered listeners of a possible network failure. In particular, JBossMessaging registers a listener which will shut down a JMS connection when called.
"clientLeasePeriod" determines how often a ping is sent. It looks like you have the default value used by JBossMessaging, i.e., 10 seconds. If your network or server are particularly busy, you might want to increase the value.
-Ron