A new receiver adaptation method for congestion control in layered multicast transmissions

The paper focuses on a congestion control algorithm to be used in receiver adaptation for layered multicast transmissions. Its main benefit is to allow multimedia transmissions in heterogeneous environments, such as the Internet, providing access to receivers with different bandwidths and adapting automatically to the network´s capacity. The proposed algorithm is called ALM (adaptive layered multicast), and the adaptation occurs at the receiver side, ensuring great simplicity for the system, as the only responsibility of the transmitter is to send data in different layers (multicast groups), without any need of confirmation or response from the receivers. The internal elements of the network do not need any modification, and the protocol runs over today´s Internet. To validate the method the ns2 software (see VINT Project - Virtual InterNetwork Testbed, http://www.isi.edu/nsnam/vint, 2001) was used, with modifications where required. Various simulations were undertaken to prove the algorithm´s functionality using tail drop and RED discarding policies, with CBR and exponential traffic types. An implementation is in progress, and the simulation results are compared with the ones obtained in a real controlled environment.