Design and implementation of a measurement and alert system of QoS parameters in SIP based Internet telephony

This paper proposes a measurement system of QoS parameters for a SIP based Internet telephony service. This system is called QoS agent and will allow telephony user to receive alerts in real time if network conditions are not suitable to make a call. Two complementary types of measurement methods will be used. The first one is called incall method which uses RTCP packets statistics obtained during the first seconds of a call in progress. The second one is called outcall method. It periodically uses the SIP OPTIONS method to obtain delay statistics out of a call. This system constitutes an alternative solution of QoS management for IP telephony service providers that use third party´s infrastructure to provide the service