A tremendous amount of research has been done toward improving transport-layer performance over wireless data networks. The improved transport layer protocols are typically application-unaware. In this paper, we argue that the behavior of applications can and does dominate the actual performance experienced. More importantly, we show that for practical applications, application behavior all but completely negates any improvement achievable through better transport layer protocols. In this context, we motivate an application-aware, but application transparent, solution suite called A^3 (application-aware acceleration) that uses a set of design principles realized in an application-specific fashion to overcome the typical behavioral problems of applications. We demonstrate the performance of A^3 through both emulations using realistic application traffic traces and implementations using the NetFilter utility.

Peer-to-peer (P2P) data networks dominate Internet traffic. In this work, we study the problems that arise when mobile hosts participate in P2P networks. We primarily focus on the performance issues as experienced by the mobile host, but also study the impact on other fixed peers. Using Bit Torrent as a key example, we identify several unique problems that arise due to the design aspects of P2P networks being incompatible with typical characteristics of wireless and mobile environments. We then present a wireless P2P (wP2P) client application that is backward compatible with existing fixed peer client applications, but when used on mobile hosts can significant improve performance.

Current popular web-browsers simply fetch the entire web-page from the server in a greedy fashion. This simple web fetching mechanism employed by browsers is inappropriate for use in low-bandwidth networks, since they cause large response times for users unneccesarily. In this paper, we first analyze the reasons that cause large response times by considering several factors including the properties of typical web-pages and browsers, the interaction of the HTTP and TCP protocols, and the impact of server-side optimization techniques. We then propose three easy-to-deploy browser-side optimization mechanisms to reduce the user response time. Through simulations, we compare the performance of our solution with that of current browsers and show that the proposed scheme brings significant performance benefits in terms of user-perceived response times.

Web-based information access suffers tremendously in low-bandwidth wireless data networks due to the non-correlation between the content transferred across the wireless links and the actual data that is used to serve the user requests. As a result, the current web-access mechanisms face such problems as unnecessary bandwidth consumption, large response times, no service for partial disconnections, and low system utilization in wireless networks. In order to solve these problems with web-transfer in wireless networks, we present a new middleware for wireless web-access called Cut-Load, which performs application unaware content-partitioning in the graphical domain residing at both the mobile client and the proxy server that the mobile client communicates with. Cut-Load uses dynamic mode selection, opportunistic hoarding, transparent mode transfer, and display caching for efficient wireless web-access. Through simulations, we compare the performance of Cut-Load with that of the current web-access mechanisms and show that the proposed middleware brings significant performance benefits both in terms of bandwidth consumption and user-perceived response times.

A tremendous amount of research has been done toward improving transport layer performance over wireless data networks. The improved transport layer protocols are typically application-unaware. In this paper, we argue that the behavior of applications can and do dominate the actual performance experienced. More importantly, we show that for practical applications, application behavior all but completely negates any improvements achievable through better transport layer protocols. In this context, we motivate an application-aware, but application transparent, solution suite called A 3 (application-aware acceleration) that uses a set of design principles realized in an application specific fashion to overcome the typical behavioral problems of applications. We demonstrate the performance of A3 through emulations using realistic application traffic traces.

The communication model typically assumed in wireless ad-hoc networks is based on a traditional "pipelined relay" (PR} strategy. In PR, an end-to-end flow has multiple outstanding packets (or data units) along the path from the source to the destination. In this paper, we argue that due to several unique properties of wireless ad-hoc networks, PR can be fundamentally improved upon. We present a new non-pipelined relay (nPR) strategy, where end-to-end flows have exactly one outstanding packet (or data unit) along the end-to-end path. We show that nPR has the following properties: (i) under idealized network conditions, it provides performance improvement, in terms of end-to-end throughput capacity and network transport capacity over PR, and achieves proportional fairness; and (ii) under practical network conditions, it further increases the above performance improvements, both in terms of the throughput achieved, and in terms of the fairness between flows. Finally, we present a forwarding protocol that practically realizes nPR. Through analysis and ns2 based packet level simulations, we evaluate the performance of the proposed strategy, and that of the forwarding protocol.

In this paper, we consider the problem of file synchronization when a mobile host shares files with a backbone file server in a network file system. Several diff schemes have been proposed to improve upon the transfer overheads of conventional file synchronization approaches which use full file transfer. These schemes compute the binary diff of the new file with respect to the old copy at the server and transfer the computed diff to the server for file-synchronization. However, Lee et al. have shown that the performance of diff can be significantly improved upon by shipping user operations as opposed to the data itself. Using this as motivation, we present a purely application-unaware approach called Mimic that relies on transferring raw user activity to the server for file synchronization. Through a simple prototype of the proposed approach, we show that Mimic can outperform diff under many common conditions. We also identify conditions under which diff based approaches do perform better than the proposed approach, but show that detection of such conditions is straightforward, thus enabling both schemes to be used in tandem with a mobile file system for bandwidth-efficient file synchronization.

The IEEE 802.11 standard provides fast recovery from frame losses using a rapid link level positive acknowledgment scheme. However, the adoption of positive acknowledgment leads to inefficient frame transmission. To improve efficiency of the acknowledgments mechanism in IEEE 802.11, we propose a novel link layer protocol for wireless LANs. The proposed protocol is an adaptation of an ATM-based protocol, the service specific connection oriented protocol (SSCOP), for use as a link layer protocol in wireless LANs. The protocol uses significantly less bandwidth on the return path and enhances the performance of data frame transmission. We evaluate and compare the performance of the protocol with IEEE 802.11. The results show that the proposed protocol has a much better performance in an error-prone wireless environment, even when the bit error rate is severely degraded.

Wireless networks are becoming very popular and the IEEE 802.11 devices are widely used everywhere nowadays. New concerns are raised when it comes to wireless security. Since the current security scheme in IEEE 802.11 namely wired equivalent privacy (WEP) is known to be quite insecure, virtual private network (VPN) is used to solve the security problems in wireless networks. However, the use of both WEP and VPN causes authentication redundancy at the mobile hosts. This paper proposes a novel lightweight authentication protocol, consisting of a lightweight synchronization algorithm and a statistical scheme. A complete analysis, detailed implementation issues and evaluation for the authentication protocol are included in the paper.