The Signaling Protocol

A signaling protocol establishs and maintains a communication session. The ICEBERG signaling protocol contains two phases: Call Session Establishment and Call Session Maintenance .

Call Session Establishment

In this version, call session establishment takes the form of Ninja RMI calls (our next version will follow the design in our architecture paper). The establishment process goes through the following steps:

• Caller IAP obtains a Call Agent to service its endpoint, then issue an "handleOutgoingCall" RMI call to the Call Agent.
• The Call Agent performs the following actions to set up the session:
  • Look up callee's ICEBERG Unique ID and his iPOP through the Name Mapping Service (NMS).
  • Ask the callee iPOP to dispatch a Call Agent to serve the callee.
  • Issues the "handleIncomingCall" RMI to the callee Call Agent.
• Callee Call Agent handles the incoming call through the following actions:
  • Look up the callee's preference registry for desireable call receiving endpoint
  • Locate the IAP for the callee's endpoint.
  • Alert the IAP, and feedback to the caller Call Agent.

Call Session Maintenance

At the end of the call session establishment, the Call Agents of both the caller and the callee will start their periodic announcement (period set to be 1 second) of their call state to the Call Session which is represented by an IP multicast address in this release. The call state includes the call party and the device the Call Agent is serving, and the data path endpoint info such as the IP address and port number where to receive the data stream from. The Call Agents interacts with the Automatic Path Creation (APC) service whenever receiving a new or modified call state. Upon the timeout (set to be 5 seconds) of the periodic announcement on a call state, that endpoint is considered network partitioned or removed from the current session, then the Call Agent interacts with the APC to tear down the path with that endpoint.

For the philosophy and details of our signaling protocol, please refer to the paper "A Signaling System Using Lightweight Call Sessions" [ ps.gz ], Proceedings of IEEE INFOCOM 2000, Tel-Aviv, Israel. March 2000.