Loss Differentiation And Recovery In Tcp Over Wireless Wide-Area Networks

The increasing speed and coverage of wireless widearea networks (WWAN) has made technologies such as GPRS, UMTS, or HSDPA a popular way to access the Internet for both mobile and stationary users. However, depending on the scenario, WWAN can suffer from severe IP packet loss due to corruption, which is mistaken by TCP as an indication of path congestion. This paper presents an approach to solve the loss differentiation problem for the widespread scenario of wireless networks being used as access networks to the Internet. Our solution allows TCP to distinguish between congestion and corruption loss and to properly react to both phenomena. Loss differentiation is achieved by placing an assisting agent on the WWAN's base station, which replies a TCP sender in the wired Internet with a new type of acknowledgement. Without harming TCP's end-toend semantics, these acknowledgements provide feedback about congestion on the wired path and corruption on the wireless path and support the sender in taking remedial action. Results from simulations indicate that our proposed corruption recovery algorithm significantly improves the TCP goodput. In addition, excessive RTO growth and pauses in the TCP flow that result from repeated packet corruption are considerably reduced.