Creating and using a SipMessage
Computing 2543 transaction ids.
Transaction ids are used to map a message to the state of its transaction.
3261 uses assigned transaction ids carried in the branch parameter of the Via. 2543 uses a transaction id that is computed from the message.
The 2543 transaction is a hash of:
- top Via
- commutativeParameterHash (not sensitive to the order of the paramters)
- From tag
- To tag (if non-invite request)
- method (INVITE if ACK or CANCEL)
Once computed, the 2543 transaction id is cached on the message.