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124
A conceptual framework for network and client adaptation
, 2000
"... Modern networks are extremely complex, varying both statically and dynamically. This complexity and dynamism are greatly increased when the network contains mobile elements. A number of researchers have proposed solutions to these problems based on dynamic adaptation to changing network conditions a ..."
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Cited by 29 (0 self)
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Modern networks are extremely complex, varying both statically and dynamically. This complexity and dynamism are greatly increased when the network contains mobile elements. A number of researchers have proposed solutions to these problems based on dynamic adaptation to changing network conditions and application requirements. This paper summarizes the results of several such projects and extracts several important general lessons learned about adapting data flows over difficult network conditions. These lessons are then formulated into a conceptual framework that demonstrates how a few simple and powerful ideas can describe a wide variety of different software adaptation systems. This paper describes an Adaptation Framework in the context of the several successful adaptation systems and suggests how the framework can help researchers think about the problems of adaptivity in networks.
Adaptive Offloading for Pervasive Computing
"... Pervasive computing allows a user to access an application on heterogeneous devices continuously and consistently. However, it is challenging to deliver complex applications on resource-constrained mobile devices such as cell phones. Application-based or system-based adaptations have been proposed t ..."
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Cited by 28 (2 self)
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Pervasive computing allows a user to access an application on heterogeneous devices continuously and consistently. However, it is challenging to deliver complex applications on resource-constrained mobile devices such as cell phones. Application-based or system-based adaptations have been proposed to address the problem, but they often require application fidelity to be significantly degraded. We believe that this problem can be overcome by dynamically partitioning the application, and by offloading part of the application execution with data to a powerful nearby surrogate. This allows the application to be delivered in a pervasive computing environment without significant fidelity degradation or expensive application rewriting. Runtime offloading needs to adapt to different application execution patterns and resource fluctuations in the pervasive computing environment. Hence, we have developed an offloading inference engine to adaptively solve two key decision-making problems in runtime offloading: (1) timely triggering of offloading, and (2) efficient partitioning of applications. Both trace-driven simulations and prototype experiments show the effectiveness of the adaptive offloading system.
Adaptive Offloading Inference for Delivering Applications in Pervasive Computing Environments
- Proc. of IEEE International Conference on Pervasive Computing and Communications (PerCom 2003), Dallas-Fort
, 2003
"... Pervasive computing allows a user to access an application on heterogeneous devices continuously and consistently. However, it is challenging to deliver complex applications on resource-constrained mobile devices, such as cell phones and PDAs. Different approaches, such as application-based or syste ..."
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Cited by 26 (2 self)
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Pervasive computing allows a user to access an application on heterogeneous devices continuously and consistently. However, it is challenging to deliver complex applications on resource-constrained mobile devices, such as cell phones and PDAs. Different approaches, such as application-based or system-based adaptations, have been proposed to address the problem. However, existing solutions often require degrading application fidelity. We believe that this problem can be overcome by dynamically partitioning the application and offloading part of the application execution to a powerful nearby surrogate. This will enable pervasive application delivery to be realized without significant fidelity degradation or expensive application rewriting. Because pervasive computing environments are highly dynamic, the runtime offloading system needs to adapt to both application execution patterns and resource fluctuations. Using the Fuzzy Control model, we have developed an offloading inference engine to adaptively solve two key decision-making problems during runtime offloading: (1) timely triggering of adaptive offloading, and (2) intelligent selection of an application partitioning policy. Extensive trace-driven evaluations show the effectiveness of the offloading inference engine.
GPRSWeb: Optimizing the Web for GPRS Links
- In Proceedings of the ACM/USENIX MobiSys 2003, May 2003
, 2003
"... The General Packet Radio Service (GPRS) is being deployed by GSM network operators world-wide, and promises to offer users always-on data access at bandwidths comparable to that of conventional fixed-line telephone modems. Unfortunately, many users have found the reality to be rather different, expe ..."
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Cited by 23 (4 self)
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The General Packet Radio Service (GPRS) is being deployed by GSM network operators world-wide, and promises to offer users always-on data access at bandwidths comparable to that of conventional fixed-line telephone modems. Unfortunately, many users have found the reality to be rather different, experiencing very disappointing performance when, for example, browsing the web over GPRS. In this paper we show what causes the web and its underlying transport protocol TCP to underperform in a GPRS wide-area wireless environment. We examine why certain GPRS network characteristics interact badly with TCP to yield problems such as: link under-utilization for short-lived flows, excess queueing for long-lived flows, ACK compression, poor loss recovery, and gross unfairness between competing flows. We also show that many web browsers tend to be overly aggressive, and by opening too many simultaneous TCP connections can aggravate matters. We present the design and implementation of a web optimizing proxy system called GPRSWeb that mitigates many of the GPRS link-related performance problems with a simple software update to a mobile device. The update is a link-aware {\em middleware} (a local `client proxy') that sits in the mobile device, and communicates with a `server proxy' located at the other end of the wireless link, close to the wired-wireless border. The dual-proxy architecture collectively implements a number of key enhancements -- an aggressive caching scheme that employs content-based hash keying to improve hit rates for dynamic content, a preemptive push of web page support resources to mobile clients, resource adaptation to suit client capabilities, delta encoded data transfer of modified pages, DNS lookup migration, and a UDP-based reliable transport protocol that is specifically optimized for use over GPRS. We show that these enhancements results in significant improvement in web performance over GPRS links.
A Web Middleware Architecture for Dynamic Customization of Content for Wireless Clients
, 2001
"... We present a new Web middleware architecture that allows users to customize their view of the Web for optimal interaction and system operation when using non-traditional resource-limited client machines such as wireless PDAs (personal digital assistants). Web Stream Customizers (WSC) are dynamically ..."
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Cited by 22 (8 self)
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We present a new Web middleware architecture that allows users to customize their view of the Web for optimal interaction and system operation when using non-traditional resource-limited client machines such as wireless PDAs (personal digital assistants). Web Stream Customizers (WSC) are dynamically deployable software modules and can be strategically located between client and server to achieve improvements i n performance, reliability, or security. An important design feature is that Customizers provide two points of control in the communication path between client and server, supporting adaptive system-based and content-based customization. Our architecture exploits HTTP's proxy capabilities, allowing Customizers to be seamlessly integrated with the basic Web transaction model. We describe the WSC architecture and implementation, and illustrate its use with three non-trivial, adaptive Customizer applications that we have built. We show that the overhead in our implementation is small and tolerable, and is outweighed by the benefits that Customizers provide.
Multimedia Service Configuration and Reservation in Heterogeneous Environments
- In Proceedings of International Conference on Distributed Computing Systems
, 2000
"... Widely deployed multimedia services are expected to accommodate clients in a highly heterogeneous environment. Clients of a multimedia service may vary greatly in processing and communication capabilities. In addition, due to workload, location, and service time differences, the availability of end- ..."
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Cited by 20 (5 self)
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Widely deployed multimedia services are expected to accommodate clients in a highly heterogeneous environment. Clients of a multimedia service may vary greatly in processing and communication capabilities. In addition, due to workload, location, and service time differences, the availability of end-to-end resources between a client and a server may also vary. Current solutions tend to focus on either the qualitative heterogeneity (in client and resource types) or the quantitative heterogeneity (in resource availability) problem. In this paper, we present a framework for dynamic end-to-end multimedia service configuration and reservation - an integrated solution to both aspects of the heterogeneity problem. Service configuration is responsible for choosing appropriate service components to compose a customized service delivery to each client; while service reservation is responsible for reserving the end-to-end resources in a coordinated manner, and providing the best possible quality within the chosen configuration. We have implemented a prototype of this framework as part of the 2K operating system, and tested it by building a proof-ofconcept video streaming service on top of it. Our experiments show the soundness of this framework.
System Support for Scalable and Fault Tolerant Internet Services
- IN IFIP INTERNATIONAL CONFERENCE ON DISTRIBUTED SYSTEMS PLATFORMS AND OPEN DISTRIBUTED PROCESSING (MIDDLEWARE '98), LAKE DISTRICT
, 1998
"... Over the past few years, we have seen the proliferation of Internet-based services ranging from search engines and map services to video-on-demand servers. All of these kinds of services need to be able to provide guarantees of availability and scalability to their users. With millions of users on t ..."
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Cited by 17 (8 self)
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Over the past few years, we have seen the proliferation of Internet-based services ranging from search engines and map services to video-on-demand servers. All of these kinds of services need to be able to provide guarantees of availability and scalability to their users. With millions of users on the Internet today, these services must have the capacity to handle a large number of clients and remain available even in the face of extremely high load. In this paper, we present a generic architecture for supporting such Internet applications. We provide a substrate for Scalable Network Services (SNS), on top of which application developers can design their services without worrying about the details of service management. We back our design with three real-world services: a web distillation proxy, a proxy-based web-browser for PDAs, and an MBone archive server.
Session Level Techniques for Improving Web Browsing Performance on Wireless Links
- In Proc. of the 13th international conference on World Wide Web
, 2004
"... Recent observations through experiments that we have performed in current third generation wireless networks have revealed that the achieved throughput over wireless links varies widely depending on the application. In particular, the throughput achieved by file transfer application (FTP) and web br ..."
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Cited by 15 (2 self)
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Recent observations through experiments that we have performed in current third generation wireless networks have revealed that the achieved throughput over wireless links varies widely depending on the application. In particular, the throughput achieved by file transfer application (FTP) and web browsing application (HTTP) are quite different. The throughput achieved over a HTTP session is much lower than that achieved over an FTP session. The reason for the lower HTTP throughput is that the HTTP protocol is affected by the large Round-Trip Time (RTT) across Wireless links. HTTP transfers require multiple TCP connections and DNS lookups before a HTTP page can be displayed. Each TCP connection requires several RTTs to fully open the TCP send window and each DNS lookup requires several RTTs before resolving the domain name to IP mapping. These TCP/DNS RTTs significantly degrade the performance of HTTP over wireless links. To overcome these problems, we have developed session level optimization techniques to enhance HTTP download mechanisms. These techniques (a) minimize the number of DNS lookups over the wireless link and (b) minimize the number of TCP connections opened by the browser. These optimizations bridge the mismatch caused by wireless links between application-level protocols (such as HTTP) and transportlevel protocols (such as TCP). Our solutions do not require any client-side software and can be deployed transparently on a service provider network to provide 30 50% decrease in end-to-end user perceived latency and 50-100% increase in data throughput across wireless links for HTTP sessions.
ANTARCTICA: A Multiagent System for Internet Data Services in a Wireless Computing Framework
, 2001
"... Nowadays, the widespread use of wireless devices that can be connected to Internet allows users to access information from anywhere and at anytime. However, the management of Internet data services makes users of wireless devices face certain problems such as the inestability of the used media, the ..."
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Cited by 15 (14 self)
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Nowadays, the widespread use of wireless devices that can be connected to Internet allows users to access information from anywhere and at anytime. However, the management of Internet data services makes users of wireless devices face certain problems such as the inestability of the used media, the lack of suitability of existing services to the limited capabilities of some wireless devices (e.g., in the visualization of GUI's) and the high cost that their use implies. In this paper, we present the general features of ANTARCTICA, a system which provides users of wireless devices with a new environment to achieve their data management needs. The ANTARCTICA system is based on the use of proxies and agent technology and presents the following main features: 1) multiplicity, managing multiple data services, 2) scalability, allowing one to incorporate new services, 3) eciency, optimizing wireless communications, 4) exibility, supporting the mobility of users without restrictions, and 5) simplicity, making technical issues transparent to the users. We also report on the implementation of some services supported by ANTARCTICA and present experimental results associated to them.
Web&: An Architecture for Non-Interactive Web
- In Proceedings of the Nineth International World Wide Web Conference
, 2001
"... As the use of the world wide web grows, the profile of web use has changed significantly. Web use has gone from purely information access to e-commerce. The interactive (synchronous) model which the world wide web currently supports is time consuming. Web browsing can easily become a frustrating ..."
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Cited by 14 (0 self)
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As the use of the world wide web grows, the profile of web use has changed significantly. Web use has gone from purely information access to e-commerce. The interactive (synchronous) model which the world wide web currently supports is time consuming. Web browsing can easily become a frustrating experience if the network or servers incur delays, are not accessible, or the same interaction must be repeated many times. This model is even more painful for clients who are disconnected most of the time or are accessing the web via low bandwidth connections and resource constrained devices such as PDAs. Therefore, there is a legitimate need to support non-interactive, (asynchronous) transactions between client and servers on the web. A non-interactive model is more e#cient because (i) there is reduced sensitivity to network latencies /unavailability, (ii) web activities can be performed concurrently and (iii) client mobility can be easily supported. In this paper, we propose a n...
