Home // International Journal On Advances in Telecommunications, volume 4, numbers 3 and 4, 2011 // View article
Authors:
Stefan Gasterstädt
Markus Gusowski
Keywords: Voice over IP (VoIP), Session Initiation Protocol (SIP), Media Connectivity, Connectivity Awareness, SCTP.
Abstract:
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. We present and compare several approaches solving this problem that use both implicit and explict connectivity detection and notification mechanisms. Our favoured approach uses a set of behavioral rules for the user agents and implicit connectivity notification to achieve connectivity awareness. We also suggest SCTP for media transport and as an efficient connectivity detection mechanism. Besides conforming to the existing SIP standards and minimizing protocol changes, our solution is able to tolerate "lying" user agents. Measurements with our prototype SIP proxy implementation show that the impact on provider side call processing performance is negligible.
Pages: 276 to 292
Copyright: Copyright (c) to authors, 2011. Used with permission.
Publication date: April 30, 2012
Published in: journal
ISSN: 1942-2601