A Realtime Network Simulation Platform Based On NS

With the advances in the broadband networking technology, real-time audio-visual communications (termed as media communications for simplicity) are possible even in the current best-effort IP networks. However, their requirements on end-to-end throughput, delay, delay variations, packets loss rate and etc. cannot be fulfilled in a constant manner, therefore the quality of the communications is not stable and could be easily impaired. In order to support real-time audio-visual communications, clearly characterizing network performance is very essential. And the performance metrics are able to directly reflect the QoS of the network. It is possible to predict, control and assign the network resource by measuring, analyzing and modeling communications.Firstly, a media control mechanism named as MACOM, which is with the introduction of a special type of hosts (termed as MA), media devices and related ALC mechanisms is introduced in this paper. MA is a persistent component. The basic tasks of MA include measurements and QoS evaluations, based on which admission controls and harmony controls are conducted. Due to its persistency, MA can provide more accurate information regarding network features for the initialization and elaboration of the ALC mechanisms being managed. In order to measure the available bandwidth of the network, an adaptive probing mechanism (LOMA) was developed. With the ability to adapt automatically the ways of measurement to network conditions, LOMA restrains the probing streams sufficiently and maintains minimum the potential impairments. Owing to these features, being a network of MAs, the MACOM system can be used to provide soft guarantees on the quality of the media communications in the current best-effort IP networks.