MeGaDiP: A wide-area Media Gateway Discovery Protocol

In wide-area and heterogeneous environments, it is necessary to deploy media gateways at strategic locations within the networks, in order to deliver customized and compose-able multimedia services to individual users. In many cases, media gateways have to be dynamically discovered, because (1) a host may not know a priori all the media gateways it will possibly use, and (2) the change of host location or end-to-end resource condition can make a known media gateway no longer useful. However, current general service location mechanisms are not sufficient to perform media gateway discovery. In this paper, we present MeGaDiP, a wide-area Media Gateway Discovery Protocol. It is based on the same basic architecture of the general service location mechanisms, and can be seen as a discovery heuristics that will be invoked first when discovering a media gateway. The key properties of MeGaDiP include: (1) awareness of both source and destination end hosts: any discovered media gateway will not create an excessively long path between the end hosts via the gateway; (2) resource-awareness: any discovered media gateway is likely to have sufficient end-to-end resources to perform its service; (3) return of discovery results with low latency and high validity by caching and resource validation; (4) small amount of management traffic, regardless of the number of media gateways and end hosts in the environment. Furthermore, an extension to MeGaDiP using a hierarchical architecture is proposed to improve the discovery success rate. The initial performance results from both our prototype implementation and simulation show the soundness of MeGaDiP.