Performance Enhancement Proxy for Heterogeneous Networks

Abstract

Transmission Control Protocol (TCP) is widely used in data communications for newlinevarious types of applications. Application layer protocols like Hyper Text Transfer newlineProtocol (HTTP), File Transfer Protocol (FTP), use TCP as transport layer protocol newlineover heterogeneous networks. Links like wired, wireless (e.g., Wi-Fi, WLAN, WiMAX, newline3G), and satellite constitute the heterogeneous networks which have varied Round newlineTrip Time (RTT) and a mixture of congestive losses and link losses due to Bit Error newlineRate (BER). A variety of TCP variants exist that address the issues pertaining to newlinespeci_c link characteristics or application environments. On a wireless link, BER is newlinenormally in the range of 10and#1048576;6 to 10and#1048576;11 which is very high as compared to that of newlinewired link (i.e., 10and#1048576;12 to 10and#1048576;14 ). RTT also varies from 1 ms to 1500 ms for di_erent newlinelink types. However, a protocol addressing the requirements of TCP for links with newlinevariable RTT and BER is equally desirable. In the present research work, this issue newlineis addressed by designing a new TCP variant named as Tarang and a dynamic TCP newlinelayer architecture named as ADYTIA. ADYTIA addresses the issue of single variant newlineusage for all networking scenarios and application environments. newlineTarang is a new TCP protocol designed for the link with variable RTT and newlineBER. It improvises the start-up performance on high RTT link by using the concept newlineof normalized round trip time and a modi_ed approach to increase the congestion newlinewindow (cwnd) in slow-start phase. When congestion occurs, instead of halving cwnd newlineas per the traditional Additive Increase Multiplicative Decrease (AIMD) approach, newlineTarang uses the utilized link bandwidth to set the value of cwnd and slow-start newlinethreshold (ssthresh). This way, Tarang can provide better throughput as compared to newlinethe default TCP variant (Cubic in Linux and NewReno in Windows family operating newlinesystems) and can replace the default TCP variant in various operating systems. newlineTarang outperforms other existing TCP variants in most of the cases and also newlinemaintains fairness.