An Analysis of Alterations to the SCTP RTO Calculation Mechanism for WLAN Environments

As a connection oriented transport layer protocol the Stream Control Transmission Protocol (SCTP) inherits many of the features of the Transmission Control Protocol (TCP) including the mechanism by which Retransmission Timeout (RTO) is calculated. Previous investigations have established that the mechanism through which SCTP calculates RTO is inappropriate in Wireless LAN (WLAN) environments. This paper investigates the performance implications of changes to the SCTP RTO calculation mechanism. In particular alterations to the parameters α, the smoothing factor, and β, the delay variance factor are investigated. Results indicate that performance improvements are achievable through careful selection of α and β values. Throughput improvements of 63% over the default mechanism defined in RFC 4960 are described. These performance improvements however, while significant, still can not address the switchover delays which result from the distortions caused by continuously increasing RTT values in WLAN environments.