TCP over Wireless Links: Mechanisms and Implications
Sonia Fahmy, Venkatesh Prabhakar, Srinivas R. Avasarafa, Ossama Mohamed Younis · 2003
Abstract — In wireless networks, the implicit assumption which TCP makes that losses indicate network congestion is no longer valid. Losses in wireless networks can result from bit errors, fading and handoffs. There are two different approaches to improve TCP performance in case of wireless losses: (1) hide non-congestion-related losses from the TCP sender, using either TCP-aware or TCP-unaware reliable link layer protocols, or using split connections with separate wireline and wireless TCP connections, or (2) adapt the TCP sender to realize that some losses are not due to congestion, e.g., using selective acknowledgments or explicit loss notification. In this paper, we classify popular mechanisms that have been recently proposed to solve the wireless transport problem, and contrast them according to their complexity, ease of deployment, and performance in different scenarios. We conclude that some TCP sender adaptations work well for certain environments only, while others are generally useful. Local recovery works best when the wireless link delay is small, and split connection schemes allow application/transport level optimizations, but exhibit overhead and lack robustness. Keywords — TCP/IP, congestion control, wireless networks, satellite networks I.