Date Added: Apr 2012
In SIP-based Voice over IP infrastructures, media data is usually exchanged directly between the endpoints using RTP without provider interaction. In contrast to the Public Switched Telephone Network where the delivery of all messages is the provider's responsibility, a SIP provider is not aware of media connectivity, i.e., whether a call was successful or not. This may lead to incorrect behavior when a Voice over IP provider offers services beyond signaling (for example, payment, prevention of Spam over Internet Telephony). Most existing mechanisms relating to media connectivity only aim at increasing the chance for connectivity or are endpoint centric and cannot achieve media connectivity awareness for the provider.