RLC protocol performance over TCP SACK

The Radio Link Control (RLC) protocol, used in Universal Mobile Telecommunication System (UMTS) networks, is one of the most advanced and complex link layer protocols. Among its notable features are the absence of retransmission timers, which makes it tolerant to contention for the link, and the ability to abandon persistently lost frames, which makes it suitable for reliable transport layers. In order to assess whether it makes sense to use RLC with non-UMTS wireless links, especially in the face of the enhanced error recovery offered by TCP with the Selective Acknowledgment (SACK) option, we implemented it in the ns-2 simulator and measured the throughput achieved by File Transfer and Web Browsing over RLC, either with or without contention from a Media Distribution application. While we found that RLC adapts well to the available bandwidth, providing considerable performance gains with random losses, with bursty losses RLC hardly improved upon TCP SACK.