There is considerable interest in programs that can migrate from one host to another and execute.... more There is considerable interest in programs that can migrate from one host to another and execute. Mobile programs are appealing because they support efficient utilization of network resources and extensibility of information servers. However, since they cross administrative domains, they have the ability to access and possibly misuse a host’s protected resources. In this paper, we present a novel approach for controlling and protecting a site’s resources. In this approach, a site uses a declarative policy language to specify a set of constraints on accesses to resources. A set of code transformation tools enforces these constraints on mobile programs by integrating the access constraint checking code directly into the mobile program and resource definitions. Because our approach does not require resources to make explicit calls to a reference monitor, it does not depend upon a specific runtime system implementation.
Abstract: With the advent of WWW, there is considerable interest in programs that can migrate fro... more Abstract: With the advent of WWW, there is considerable interest in programs that can migrate from one host to another and execute. For instance, Java programs are increasingly being used to add dynamic content to a web page. When a user accesses the web page ...
Modern software must evolve in response to changing conditions. In the most widely used programmi... more Modern software must evolve in response to changing conditions. In the most widely used programming environments, code is static and cannot change at runtime. This poses problems for applications that have limited down-time. More support is needed for dynamic evolution. In this paper we present an approach for supporting dynamic evolution of Java programs. In this approach, Java programs can evolve by changing their components, namely classes, during their execution. Changes in a class lead to changes in its instances, thereby allowing evolution of both code and state. The approach promotes compatibility with existing Java applications, and maintains the security and type safety controls imposed by Java’s dynamic linking mechanism. Experimental analyses of our implementation indicate that the implementation imposes a moderate performance penalty relative to the unmodified virtual machine.
Applications that are distributed, fault tolerant, or perform dynamic load balancing rely on redi... more Applications that are distributed, fault tolerant, or perform dynamic load balancing rely on redirection techniques, such as network address translation (NAT), DNS request routing, or middleware to handle Internet scale loads. In this paper, we describe a new connection redirection mechanism that allows applications to change end-points of communication channels. The mechanism supports redirections across LANs and WANs and is application-independent. Further, it does not introduce any central bottlenecks. We have implemented the redirection mechanism using a novel end-point control session layer. The performance results show that the overhead of the mechanism is minimal. Further, Internet applications built using this mechanism scale better than those built using HTTP redirection.
Page 1. Supporting Quality Of Service in HTTP Servers Raju Pandey J. Fritz Barnes Ronald Olsson P... more Page 1. Supporting Quality Of Service in HTTP Servers Raju Pandey J. Fritz Barnes Ronald Olsson Parallel and Distributed Computing Laboratory Computer Science Department University of California, Davis, CA 95616 {pandey, ba.rnes, olsson}Qcs.ucdavis.edu Abstract ...
Web caching has emerged as one solution for improving client latency on the web. Cache effectiven... more Web caching has emerged as one solution for improving client latency on the web. Cache effectiveness depends on the policies used to route requests to other caches and servers, to maintain up-to-date web objects and to remove objects from the cache. Traditional caches apply one set of policies, which determines the eciency as well as the effectiveness of the caches.
Virtual machines (VM) are promising as system software in networks of embedded systems and pervas... more Virtual machines (VM) are promising as system software in networks of embedded systems and pervasive comput- ing spaces. VMs facilitate the development of platform- independent applications with small footprints to enable low cost application distribution and evolution. A major im- pediment to their more widespread acceptance is the per- formance overhead of interpretation. Compiling VM byte- code to native instructions addresses this issue, but can in- crease footprint and code distribution costs. Thus, there is an important tradeo between cost of computing, and cost of communication due to code distribution. In this paper, we describe a remote Just-In-Time (JIT) compilation ser- vice for the VMF framework that is eectiv e in combining interpretation with native execution to arrive at an ecien t hybrid execution conguration. The principles apply to any VM or middleware used to develop applications in sensor networks.
Sensor networks have received wide attention in recent years for their revolutionary impact in nu... more Sensor networks have received wide attention in recent years for their revolutionary impact in numerous fields. To harness their full potential, researchers are beginning to build end-to-end solutions that integrate het- erogeneous sensor deployments with traditional networks. While such efforts will bring true value to the use of sensor networks, there are several challenges that need to be kept in
Resource constrained systems often are programmed using an event-based model. Many applications d... more Resource constrained systems often are programmed using an event-based model. Many applications do not lend themselves well to an event-based approach, but preemptive multithreading pre-allocates resources that cannot be used even while not in use by the owning thread. In this paper, we propose a hybrid approach called Y-Threads. Y-Threads provide separate small stacks for blocking portions of applications, while allowing for shared stacks for non-blocking computations. We have implemented Y-Threads on Mica and Telos wireless sensor network platforms. The results show that Y-Threads provide a preemptive multithreaded programming model with resource utilization closer to an event-based approach. In addition, relatively large memory buffers can be allocated for temporary use with less overhead than conventional dynamic memory allocation methods.
There is considerable interest in programs that can migrate from one host to another and execute.... more There is considerable interest in programs that can migrate from one host to another and execute. Mobile programs are appealing because they support efficient utilization of network resources and extensibility of information servers. However, since they cross administrative domains, they have the ability to access and possibly misuse a host’s protected resources. In this paper, we present a novel approach for controlling and protecting a site’s resources. In this approach, a site uses a declarative policy language to specify a set of constraints on accesses to resources. A set of code transformation tools enforces these constraints on mobile programs by integrating the access constraint checking code directly into the mobile program and resource definitions. Because our approach does not require resources to make explicit calls to a reference monitor, it does not depend upon a specific runtime system implementation.
Abstract: With the advent of WWW, there is considerable interest in programs that can migrate fro... more Abstract: With the advent of WWW, there is considerable interest in programs that can migrate from one host to another and execute. For instance, Java programs are increasingly being used to add dynamic content to a web page. When a user accesses the web page ...
Modern software must evolve in response to changing conditions. In the most widely used programmi... more Modern software must evolve in response to changing conditions. In the most widely used programming environments, code is static and cannot change at runtime. This poses problems for applications that have limited down-time. More support is needed for dynamic evolution. In this paper we present an approach for supporting dynamic evolution of Java programs. In this approach, Java programs can evolve by changing their components, namely classes, during their execution. Changes in a class lead to changes in its instances, thereby allowing evolution of both code and state. The approach promotes compatibility with existing Java applications, and maintains the security and type safety controls imposed by Java’s dynamic linking mechanism. Experimental analyses of our implementation indicate that the implementation imposes a moderate performance penalty relative to the unmodified virtual machine.
Applications that are distributed, fault tolerant, or perform dynamic load balancing rely on redi... more Applications that are distributed, fault tolerant, or perform dynamic load balancing rely on redirection techniques, such as network address translation (NAT), DNS request routing, or middleware to handle Internet scale loads. In this paper, we describe a new connection redirection mechanism that allows applications to change end-points of communication channels. The mechanism supports redirections across LANs and WANs and is application-independent. Further, it does not introduce any central bottlenecks. We have implemented the redirection mechanism using a novel end-point control session layer. The performance results show that the overhead of the mechanism is minimal. Further, Internet applications built using this mechanism scale better than those built using HTTP redirection.
Page 1. Supporting Quality Of Service in HTTP Servers Raju Pandey J. Fritz Barnes Ronald Olsson P... more Page 1. Supporting Quality Of Service in HTTP Servers Raju Pandey J. Fritz Barnes Ronald Olsson Parallel and Distributed Computing Laboratory Computer Science Department University of California, Davis, CA 95616 {pandey, ba.rnes, olsson}Qcs.ucdavis.edu Abstract ...
Web caching has emerged as one solution for improving client latency on the web. Cache effectiven... more Web caching has emerged as one solution for improving client latency on the web. Cache effectiveness depends on the policies used to route requests to other caches and servers, to maintain up-to-date web objects and to remove objects from the cache. Traditional caches apply one set of policies, which determines the eciency as well as the effectiveness of the caches.
Virtual machines (VM) are promising as system software in networks of embedded systems and pervas... more Virtual machines (VM) are promising as system software in networks of embedded systems and pervasive comput- ing spaces. VMs facilitate the development of platform- independent applications with small footprints to enable low cost application distribution and evolution. A major im- pediment to their more widespread acceptance is the per- formance overhead of interpretation. Compiling VM byte- code to native instructions addresses this issue, but can in- crease footprint and code distribution costs. Thus, there is an important tradeo between cost of computing, and cost of communication due to code distribution. In this paper, we describe a remote Just-In-Time (JIT) compilation ser- vice for the VMF framework that is eectiv e in combining interpretation with native execution to arrive at an ecien t hybrid execution conguration. The principles apply to any VM or middleware used to develop applications in sensor networks.
Sensor networks have received wide attention in recent years for their revolutionary impact in nu... more Sensor networks have received wide attention in recent years for their revolutionary impact in numerous fields. To harness their full potential, researchers are beginning to build end-to-end solutions that integrate het- erogeneous sensor deployments with traditional networks. While such efforts will bring true value to the use of sensor networks, there are several challenges that need to be kept in
Resource constrained systems often are programmed using an event-based model. Many applications d... more Resource constrained systems often are programmed using an event-based model. Many applications do not lend themselves well to an event-based approach, but preemptive multithreading pre-allocates resources that cannot be used even while not in use by the owning thread. In this paper, we propose a hybrid approach called Y-Threads. Y-Threads provide separate small stacks for blocking portions of applications, while allowing for shared stacks for non-blocking computations. We have implemented Y-Threads on Mica and Telos wireless sensor network platforms. The results show that Y-Threads provide a preemptive multithreaded programming model with resource utilization closer to an event-based approach. In addition, relatively large memory buffers can be allocated for temporary use with less overhead than conventional dynamic memory allocation methods.
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