Ad Hoc mobile networks are constituted of nodes that move freely without a centralized administration. These nodes contribute in the routing of data packets that are sent by a source. This happens when the latter is not capable of reaching its destination. On the other hand, their mobility causes recurrent breakdowns of the routing paths notably with sparse MANET. In order to optimize the performance of such networks, we suggest a new extension of protocols: Stream Control Transmission Protocols (SCTP) named SCTP-MANET. Their main function is therefore to improve the availability of the links in sparse MANET protocols. This could be achieved by a better integration of Multihoming. With this aim in mind, this new extension is based on a cross-layer interface between transport and routing layers as well as the use of specific messages.