Narrow Results

Real time Internet traffic such as Voice over IP (VoIP) is difficult to estimate and simulate. Since the process is non-ergodic we must use ensemble averages rather than time averages, and for combinations of sources the simulation time can be excessive. We give some analytical results for Constant Bit Rate (CBR) traffic for the n*D/D/I queue, and for a CBR queue with varying source rates we present an expression for the Interval of Significance (IoS). This is the minimum number of time slots necessary to simulate the traffic, important because of the considerable computation time often involved in simulating this queue. Our results help in dimensioning networks for CBR services.

The purpose of this paper is to evaluate the performance of H.323 handoff methods that use ad hoc multipoint conference, transfer, and third party rerouting signaling respectively. This performance is evaluated in terms of inter-operability and signaling delay. The inter-operability specification includes multipoint conference messages, H.450.2 messages, and null TerminalCapabilitySet message. The delay of each signaling is analyzed into number of TCP connections and number of logical channel setup procedures. The results of our experiment show that third party rerouting signaling has better result than other signalings in inter-operating with terminals of four vendors, since it uses only H.323 mandatory messages. Also it requires fewer number of TCP connections and logical channel setup procedures than the others do, so it can reduce the signaling delay by 1.4 sec in average.

This paper presents a comparative analysis of call set up times, MOS (Mean Opinion Score), packet end to end delay and packet loss for the H.323 and SIP (Session Initiation Protocol) signaling schemes used in Voice Over IP (Voice over Internet Protocol) calls. We compare voice performance parameters like MOS, delay, jitter and call set up times and establish the differences in performance of these two VoIP protocols through an opnet simulation. This detailed simulation study is performed over H.323 and SIP networks where we have shown that the H.323 network performed better in terms of call set up time and packet end to end delay for the signaling messages. However, MOS for the voice packets in both the networks was expectedly the same as the same network topology was used for both the signaling protocols. There has been an influx of a large number of signaling and transport protocols over IP networks, giving rise to unacceptably large delays, most unsuitable for real time applications. SIP and H.323 are used for establishment and release of Voice aver IP calls as well as Video and Media calls. Both these protocols play a very important role in terms of optimizing the call set up time and call reliability and flexibility over IP networks for real time applications like voice and video.