QoS and Admission Probability Study for a SIP-Based Central Managed IP Telephony System

This work presents a study of a SIP-based IP telephony system in terms of Quality of Service (QoS) and admission probability. The system is designed for an enterprise with offices in different countries. A software IP PBX maintains the dial plan, and SIP proxies are used in order to implement Call Admission Control (CAC) and to allow the sharing of the gateways' lines. The system is implemented in a testbed where QoS parameters like One Way Delay (OWD), packet loss, jitter and ITU's R-factor are measured. Simulation is also used in order to build a scenario with a big number of offices in which establishment delays and admission probability are measured.