QoS tradeoffs using an application-oriented transport protocol (AOTP) for multimedia applications over IP

Traditionally, the provided service of Internet transport protocols is reliable/ordered or unreliable/unordered service, respectively. It has been widely accepted that a variety of applications (e.g. multimedia) can tradeoff reliability mechanisms to achieve higher throughput. Such a solution, which additionally respects user preferences for QoS characteristics (e.g. reliability, cost, throughput, delay) is a current demand. We propose an application-oriented transport protocol (AOTP) to handle partially or completely reliable transport service favoring throughput at the expense of reliability, or dropping the reliability level in order to keep the cost at a desired level. The protocol can be applied to cases where resource reservation is not possible or desired. Our approach does not use forward error correction to save bandwidth, but uses instead, a receiver-based retransmission mechanism. Therefore, the protocol is appropriate for applications that tolerate losses and thus, the need for retransmission (additional RTTs) does not arise often. We present encouraging initial results tested over Ethernet links; we compare AOTP with TCP and a TCP-like protocol without congestion control (TCPWCC), contrasting throughput results for different levels of reliability requirements.