MMTP - Protocolo de transporte multimedia multiplexado

Multimedia data has special requirements that are hard to be met on mobile hosts due to potentially low bandwidth and disruptions due to host mobility. Such limited communication capabilities of mobile hosts can be offset by the simultaneous use of multiple link layer technologies. MMTP is a member of a suite of protocols that share the novel characteristic of aggregating bandwidth from multiple linklayer channels. The use of multiple channels to transport user data provides five key benefits: (1) a fatter pipe,(2) a fast feedback path, (3) the retransmission of selected lost messages, without delaying the playout of the data stream, (4) less sensitivity to minor bandwidth fluctuations on any one individual channel, and (5) smooth vertical handoffs for active data streams. MMTP is a rate-based protocol designed for transferring multimedia data on mobile systems, and makes simultaneous use of every communication channel available to send data at the required rate. Transmission in MMTP is governed by two m echanisms. The first is a set of rate control protocols associated with each outgoing channel. The second is a scheduling algorithm that places incoming packets on the appropriate channel. MMTP is link-layer aware protocol that uses bandwidth estimation for congestion control, and relays to the application information needed for rate adaptation. In this paper, we show that the quality of data transmission can be improved through the use of MMTP through experimental comparisons with data transmitted via UDP. We also demonstrate the economy of bandwidth: MMTP only sends packets that it estimates will arrive within the packet deadline, thus decreasing the number of late packets that will be discarded at the receiver.