All Session Data Must Be Serializable
To support in-memory replication of SIP application call states, you must ensure that all objects stored in the SIP Servlet session are serializable. Every field in an object must be serializable or transient in order for the object to be considered serializable. If the Servlet uses a combination of serializable and non-serializable objects, Converged Application Server cannot replicate the session state of the non-serializable objects.