SLACP: A Novel Link-Layer Protocol for Wireless WANs

In this paper, we discuss the design details of a TCP/IP- friendly link-layer protocol with novel design to improve TCP performance on network paths involving a Wireless Wide-Area Network (WWAN) link. Our link layer protocol utilizes a new hybrid error-recovery mechanism combining Automatic Repeat reQuests (ARQ) and Forward Error Correction (FEC) in a way that keeps the residual packet-error rate at a very low level and minimizes the additional delay due to ARQ at the same time. The protocol supports several QoS classes by implementing several logical channels over a single physical link and by allowing each channel to be configured with QoS parameters and error control strategy that best suit to the IP traffic directed over the channel. We analyze the error recovery behavior of the protocol using packet traces from our experiments with the real implementation of the protocol and evaluate the protocol performance and the effectiveness of the QoS support in emulated wireless link environments. The results show significant TCP performance improvement and that the QoS approach supports delay-sensitive traffic effectively.