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Abstract : |
The Application Level Framing (ALF) protocol architecture [2] encourages application control over mechanisms that traditionally fall within the "transport layer", e.g., loss detection and recovery. Traditional ARQ-based reliable protocols for unicast (e.g., TCP) as well as multicast (e.g., Horus [30], RMTP [15], etc.) number data units sequentially to detect losses. Unfortunately, these transport-level sequence numbers do not permit receivers to flexibly tailor their reliability semantics. Achieving receiver-driven reliability is cumbersome in the existing "layered " architecture of the network protocol stack where the receiving application has no knowledge of how application-level objects map onto transport level sequence numbers. In this paper, we propose a new data naming scheme that exposes the structure of application data to the transport layer, thereby enhancing the expressibility of an applications ' reliability and ordering semantics. We apply this data naming scheme to a reliable multicast protocol framework to achieve receiver-tailored reliability that enhances its scalability. To demonstrate the efficacy of our scheme, we have designed and implemented our scalable naming and announcement protocol (SNAP) in the multimedia application toolkit MASH [17] as a reusable protocol module., |
