Application- and Network-Cognizant Proxies
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Sponsor: Department of Energy   Next Generation Internet Program

Project  Summary:
Current networks show increasing heterogeneity both in terms of their bandwidths/delays and the applications they are required to support. This is a trend that is likely to intensify in the future, as real-time services, such as video, become more widely available and networking access over wireless links becomes more widespread.  For this reason we propose that application-specific proxies, intermediate network nodes that broker the interactions between server and client, will become an increasingly important network element. These proxies will allow adaptation to changes in network characteristics without requiring a direct intervention of either server or client.  Moreover, it will be possible to locate these proxies strategically at those points where a mismatch occurs between subdomains (for example, a proxy could be placed so as to act as a bridge between a reliable network domain and an unreliable one.)  This design philosophy favors scalability in the sense that the basic network infrastructure can remain unchanged while new functionality can be added to proxies, as required by the applications. While proxies can perform numerous "generic'' functions, such as caching or security, we concentrate here on media-specific, and in particular video-specific, tasks. Our goal is to demonstrate that application- and network-specific knowledge at a proxy can improve overall performance especially under changing network conditions.  We consider four major scenarios, each concentrating on specific mismatches between the network functions available at either side of the proxy (i.e. in its connection with server and client, respectively). These deal with mismatches in service provisioning capabilities, in bandwidth, in reliability and in application level features. We then outline a series of tools that will be useful in improving performance under these mismatches.  These include networking tools such as models to extract relevant information from the observed environment at a proxy, or service selection strategies that will allow mapping of the streams into different classes of service. From the perspective of the source we will establish another set of tools, including transcoding, rate control algorithms, caching and error protection techniques based on multiple description coding, that will enable an application-cognizant proxy to perform some of the tasks required under mismatch situations.

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