Development & Performance Evaluation of a Measurement-Based Admission Control Technique for VoIP Services

Voice over IP (VoIP) has become a popular service in the internet as well as in enterprise intranets. However, IP networks were originally designed to provide best-effort services. They lack stringent Quality of Service (QoS) control. Moreover, congestion in these networks is inevitable and may result in packet loss, delay, and delay jitter, which directly impact the quality of the new real time applications of VoIP. So the connectionless IP network architecture must be enhanced by some guaranteeing mechanisms in order to ensure QoS. Since the realization of that, many techniques have been proposed and/or used to support QoS in IP networks. Our thesis is concerned with a set of those techniques called Admission Control of voice flows or what is called Call Admission Control (CAC) for IP telephony applications. In this thesis, we propose a real time measurement based local CAC technique (RMBLAC). The proposed technique utilizes a variation of some conventional traffic policing mechanisms of ATM networks in order to measure instantly at real time the actual superposed packet rate that is resulted from all flows in progress whenever needed. This measured rate will be used in making the decision of a new call requests’ admission. We define, describe, implement, and evaluate our proposed technique using five selected algorithms. Namely: Open Window(OW), Jumping Window(JW), Triggered Jumping Window(TJW), Exponentially Weighted Moving Average(EWMA), and Leaky Buket(LB). We use simulation to evaluate the proposed technique. We derive various conclusions about RMBLAC’s performance, and carry out a comparison between the five implementations used. In general, we concluded throughout our study that RMBLAC could achieve excellent results once care is taken in choosing its parameters