Abstract

The Session Initiation Protocol is an application layer signaling protocol designed for the session establishment between end users. These SIP sessions are established based on a request-response paradigm between the client and server components of the user agent. Proxy servers may exist within the network, which serve as a bridge between two user agents who are either within different domains or are unregistered and unaware of each others' location. The entities however are not always reliable and may encounter faults. First, this thesis aims to identify the locations within a SIP session where faults can occur and the effect on the system. The current mechanisms used to handle these faults were analyzed and it was determined that the user agents were forced to recover from faults by means of restarting the session. A novel approach was then proposed which detects and recovers from faults dynamically