The stream control transmission protocol is a new standard for generalpurpose transport proposed by the Internet Engineering Task Force. SCTP addresses application and security gaps left open by its predecessors, TCP and UDP.

Abstract-We previously evaluated five retransmission schemes in non-failure scenarios for transport protocols that support multihoming. In this paper, we introduce five additional retransmission schemes, and evaluate all ten schemes under both non-failure and failure scenarios. We show that the best retransmission policy dictates that (a) new data transmissions and fast retransmissions should be sent to the same peer IP address, and (b) timeout retransmissions should be sent to an alternate peer IP address. This policy performs best if combined with our Multiple Fast Retransmit algorithm.

We document a potential flaw in the current SCTP retransmission policy. The current scheme intends to improve the chance of success by exploiting the redundant paths between multihomed endpoints, but we have found that the current SCTP retransmission policy often degrades performance. We comparatively evaluate an alternative retransmission policy and show that the current SCTP retransmission policy unexpectedly performs worse under certain conditions. Our analysis exposes the problem and we discuss three possible solutions.

Abstract-We evaluate several retransmission policies for transport protocols that support multihoming, such as SCTP. We find that schemes that attempt to improve the chance of success by retransmitting to an alternate peer IP address often degrade performance. Our results show that for better performance, new data transmissions and retransmissions should be sent to the same peer IP address. We also find that our Multiple Fast Retransmit algorithm further improves performance by reducing the number of timeouts. Since our results assume reachability of all peer IP addresses, we conclude with suggestions for scenarios where failures are possible. We suggest compromising some of the performance improvements to avoid performance degradation during failures.

We have created a sensor-sharing protocol that uses cognition to increase performance by choosing protocol parameters based on the current environment and the past relationships between environment and performance. We have constructed a prototype of the protocol, and experimented with it in a four-node outdoor testbed. Our testbed is part of a larger effort, ADROIT, which seeks to create cognitive teams of software-defined radios [1]. 1