Internet Protocol (IP) Telephony has many issues that have to be overcome before it can be considered a rival to the existing telephony infrastructure. One such issue is the quality of service. The use of play-out buffering at the receiver helps to improve the quality of Voice over IP (VoIP). A buffering algorithm has been proposed by Narbutt, which uses a dynamic approach to buffering. This algorithm is adjusted automatically according to an estimate of the network delay. This is more suitable to the changing network conditions usually experienced. The buffer has been implemented using the H.323 signalling protocol.

The aim of this project is to incorporate Narbuttâ„¢s adaptive buffering algorithm into the Session Initiation Protocol (SIP). SIP has been shown to be much easier to implement and update than H.323. The integration of the algorithm was doing using VOCAL, a VoIP software library based around SIP. This report describes IP telephony and the protocols surrounding it, and the software used is also described. The manipulation of VoIP software to implement the play-out buffer and the issues involved in doing this are discussed.

http://ziddudownload/5195976/AndrewQuinn-FinalReport.pdf.html