Aravind Velayutham

A 3 : application-aware acceleration for wireless data networks

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.

Mimic: raw activity shipping for file synchronization in mobile file systems

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.

Application-Aware Acceleration for Wireless Data Networks: Design Elements and Prototype Implementation

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 A3 (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 both emulations using realistic application traffic traces and implementations using the NetFilter utility.

WebAccel: Accelerating Web access for low-bandwidth hosts

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 unnecessarily cause large response time for users. In this paper, we first analyze the reasons that cause large response time by considering several factors, including the properties of typical Web pages and browsers, the interaction between the HTTP and TCP protocols, and the impact of server-side optimization techniques. We then propose a new Web-acceleration solution called WebAccel, which consists of three easy-to-deploy browser-side optimization mechanisms to reduce the user response time. Through ns2 simulations and a prototype implementation, we compare the performance of our solution with that of current browsers and show that WebAccel brings significant performance benefits in terms of user-perceived response time.

Enhancing TCP for networks with guaranteed bandwidth services

In this paper, we consider TCP based applications with bandwidth guarantees, but can also benefit from any additional best-effort service offered by the network. Through simulations we show that default TCP cannot offer such applications the ideal throughput - the aggregate throughput of the reserved bandwidth and the best effort bandwidth. To illustrate the reasons for its degraded performance, we study TCPs congestion window adaptation and self-clocking mechanisms in detail. Based on the insights obtained from the study, we propose an adaptation of TCP called GTCP that employs changes to TCPs congestion control mechanisms to provide applications the optimal aggregate throughput of best-effort and reserved bandwidth. Compared with TCP, GTCP does not involve any additional implementation overhead, and only the sender need to be changed (the receiver remains to be a default TCP implementation). Through simulations and experiments over the Internet we show that GTCP achieves significantly better performance than default TCP in the target environment.

Mobile hosts participating in peer-to-peer data networks: challenges and solutions

Peer-to-peer (P2P) data networks dominate Internet traffic, accounting for over 60% of the overall traffic in a recent study. 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 BitTorrent 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. Using the insights gained through our study, we present a wireless P2P client application that is backward compatible with existing fixed-peer client applications, but when used on mobile hosts can provide significant performance improvements.

Client-side web acceleration for low-bandwidth hosts

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.

Cut-Load: Application-Unaware Content Partitioning for Web-based Information Access in Wireless Data Networks

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.

On transport layer adaptation in heterogeneous wireless data networks

Numerous transport protocols and protocol enhancements (e.g. TCP-ELN, WTCP, STP, etc) have been proposed for optimal performance in different types of wireless networks. In this paper, we define “transport layer adaptation” as the behavior of the transport protocol, with the goal of obtaining best performance, when a mobile host moves across different wireless networks. While defacto assumptions have been made in related work on the ideal characteristics of such transport layer adaptation, no explicit work has been performed in either identifying the nature of adaptation required, or the granularity at which the adaptation should occur. In this paper, we argue that : (i) Transport mechanism changes are how ideal transport adaptation should be performed. Neither transport protocol nor protocol parameter change is sufficient enough for optimal performance across heterogeneous wireless networks. (ii) Transport adaptation has to be performed at a granularity finer than interface handoffs. Ideal transport adaptation should change mechanisms even when the network characteristics change within the same wireless network. We then present the design and implementation of an adaptive transport layer framework called *TP that accommodates fine-grained runtime adaptation of transport mechanisms to achieve the best performance in a given wireless network.