Persistent SCTP timeout policy by using cross-layer mechanism

To meet various contingencies of operating wireless networks including for example the change of the state of the channel, cross-layer techniques facilitate the sharing of information between the OSI model layers and can be apply to all various protocols levels, if there are interactions for which the overall performance of the studied system can be improved. Reliable transport protocols use the retransmission timeout management mechanism (RTO-MM) when a bad state of the wireless channel occurs, which temporarily blocks the transmission of data. In this paper, we suggest a new policy of timeout applied to the Stream Control Transmission Protocol (SCTP) called persistent timeout policy. This policy is based on the use of the channel status provided by the 802.11 link layer, through the cross-layer mechanism. The principle of this timeout is that when a bad state of the wireless channel blocks the sending of data, SCTP continuously observes the evolution of this state to detect the next favorable change before sending its segments. We evaluate the following two timeout policies (persistent and traditional RTO-MM) of SCTP in an ad hoc network, and also in comparison with the Transmission Control Protocol (TCP). Section I of this paper presents an overview of the SCTP protocol. Section II presents the principle of the persistent timeout policy. Section III presents the simulation results that are used to compare the two timeout policies of the two reliable transport protocols SCTP and TCP.