M. Ranganathan, A. Acharya, S. Sharma, and J. Saltz. Network-aware Mobile Programs. In Proceedings of the USENIX 1997.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....restoring Java execution context. In the past, many different approaches have been studied and developed to capture and restore execution context. For example, execution context can be captured by inserting code into the program, which can be done manually [17,18,21,22] or via some pre processor [3,4,5,6,23]. These methods tend to incur significant overhead during execution, even when no migration actually occurs. Execution context can also be captured by extending the JVM to make thread state accessible from Java programs. But modification of the JVM can be difficult [1,7,8] Execution context can ....

....process in the heavily loaded node was migrated to an idle node. The execution time came out to be 180s. This shows that considerable performance gain can be achieved by using the migration facility of our system. 6. Related Work Them are systems, such as JESSICA [1] Ara [6] and among others [5,7], that provide state capturing and restoring of Java programs, but these systems need to modify the JVM. Some work [4,23] has been done to allow state capturing and restoring via pre processing of bytecode. Our approach is different from this in that MJavaMPI uses pre processing only to add code ....

M.Ranganthan, A. Acharya, S. D. Sharma and J Saltz. Network-aware Mobile programs. Proceedings of the USENIX Annual Technical Conference, Anaheim, California, 1997.

....service (its implementation is mainly native) Since the thread state capture restoration service has many applications, we believe that it is a basic functionality which must be integrated within the JVM. This solution has been used in the implementation of the Sumatra mobile agent platform [Ranganathan97]. Unlike Sumatra which supplies a mobility service, our implementation provides a generic service intended for other uses than mobility, like persistence [Bouchena99] The recently proposed Merpati system also follows this approach [Suezawa00] It makes the whole JVM mobile or persistent, with all ....

M. Ranganathan, A. Acharya, S. D. Sharma and J. Saltz. Network-aware Mobile Programs. Proceedings of the USENIX Annual Technical Conference, Anaheim, California, USA, January 1997. http://searchpdf.adobe.com/proxies/0/38/54/9.html

....application, videoconference, benefits of the advantages provided by code mobility by exhibiting the capability to adapt to network conditions by exploiting mobility through a MA paradigm, and providing flexibility through the COD paradigm. The approach is inspired by the work described in [89] concerning a chat server that migrates to adapt to the position of the participants. That work focuses on the benefits of the network aware positioning of the server with respect to a traditional fixed displacement. In our work the potential of code mobility and active networks have been ....

Ranganathan, M., Acharya, A., Sharma, S., and Saltz, J. Network-Aware Mobile Programs. In Proc. of the USENIX 1997.

....the Internet. Another paper discussing additional work on adapting to network bandwidth variations for wide area data access has been submitted to the 1997 International Conference on Distributed Computing Systems and will soon also be available as a University of Maryland technical report. See [43, 70, 69, 44, 72, 71, 1]. 19 5 Indiana University Report The work at Indiana University can be divided into three areas of development: 1. Support for HPC runtime in heterogeneous environments, 2. Development of Java compilation tools to support parallelism in Java and interoperability between Java and HPC 3. ....

M. Ranganathan, Anurag Acharya, Shamik Sharma, and Joel Saltz. Network aware mobile programs. In Proceedings of the USENIX

....to take architecture independent checkpoints, which are currently in a format that can only be recorded by another instrumented Ka e machine. This checkpointing facility is adequate for our purposes but was not available at the time of developing our distributed checkpointing service. Sumatra [14] is an extension of the JVM that supports resource aware mobile threads but it does not provide Java thread persistence. PJama [13] extends the JVM by adding a persistent object pool alongside the original transient object heap. The current release of PJama does not support persistent thread ....

M. Ranganathan, A. Acharya, S. D. Sharma, y J. Saltz. Network-aware mobile programs. Proceedings of the USENIX Annual Technical Conference, January 1997.

....the corresponding author. Address: PQ712, Department of Computing, Hong Kong Polytechnic University, Hung Hom, KLN, Hong Kong; Email: cspfsum comp.polyu.edu.hk; Tel: 852) 2766 7246. # I. Introduction To meet the requirement of rapid growth of the network centric programming [6] 8] 12] 15] [22], 29] and applications due to the widespread availability of the Internet and popularity of the WWW [19] 20] 30] use of mobile agents appears to be one of the most promising new techniques evolved recently. A mobile agentisa program that acts on behalf of a user to perform intelligent ....

M. Ranganathan, Anurag Acharya, Shamik Sharma, and Joel Saltz. Network-aware Mobile Programs. In ########### ## ###### '97, Winter 1997.

....column shows how the code is executed, that in the heterogeneity column shows whether or not the system allows migration between machines di#ering in processor and underlying OS, and that in the noncooperation column shows whether or not the system allows noncooperative migration. Sumatra[11] and TeleScript[16] are the systems most similar to MOBA. They di#er in programming language TeleScript has its own language, whereas MOBA and Sumatra adopt Java but their mechanisms are similar. The code is executed by an interpreter, and the execution context can migrate. Only MOBA, ....

....Most JVMs have a runtime compiler called a Just in time compiler (JIT) It translates bytecode to processor native code at runtime. A runtime system that supports the capturing of execution context, however, is incompatible with existing JIT compilers. Because the approach of MOBA and Sumatra[11] provides a runtime system supporting execution context capture, they cannot work with existing JIT compilers. Heterogeneous migration needs a machine independent representation of execution context, but most existing JIT compilers don t preserve a program counter on bytecode. Only the counter on ....

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Ranganathan, M., Acharya, A., Sharma, S., and Saltz, J. Network-aware mobile programs. In Proceedings of USENIX'97 (Jan. 1997).

....thread migration, remote thread cloning and thread persistence. A description of these experiments can be found in [Bouchenak99a] Performance figures are given in section 4.3. 4.2. 2 Sumatra D Agents The JVM extension technique has also been used to implement the Sumatra mobile agent platform [Ranganathan97], which provides strong migration for its agents. The D Agents mobile agent platform [Gray99] which supports agents in many programming languages like Tcl, Python and Scheme, uses a similar technique to integrate Java agents to its platform. For the Ara mobile agent platform [Peine97] which ....

M. Ranganathan, A. Acharya, S. D. Sharma et J. Saltz. Network-aware Mobile Programs. Proceedings of the USENIX Annual Technical Conference, Anaheim, California, 1997. http://www.javasoft.com/products/jdk/1.1/docs/

....migrated or cloned will have its reference redirected to an alias. This alias contains information on how to relocate the object. Objects that wish to obtain references to the migrated object for the first time can obtain a direct network reference through the name server. 2.2. 6 Sumatra Sumatra [1, 151] is a Java based mobile object system that supports resource awareness. Sumatra supports the ability to monitor the levels and quality of resources at a location, the ability to react to changes in resource levels, and the ability to control (as far as possible) the way that resources are used by ....

....within a system lifetime. The requirement that names are never reused must be met through the provision of a system that can ensure that each name is globally unique, which is in itself a di#cult problem. Other systems that have this requirement include Aglets, Telescript [120, 184] Sumatra [1, 151] and MOLE [14] CHAPTER 4. CLASSIFICATION OF EXISTING SYSTEMS 78 4.1.2 Knowledge Most systems support the concept of a dynamic domain or dynamic knowledge, enabling a system to grow by integrating new objects and new services. Accordingly, the name space of such a system must also be able to ....

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M. Ranganathan, A. Acharya, D.D. Sharma and Saltz J. Network-aware Mobile Programs. In Proceedings of the USENIX

....storing it in a Java object (which can be later stored in a file or sent to another machine) This extension must also provide a facility for building a new thread initialised with a previously captured state. This solution has been used in the implementation of the Sumatra mobile agent platform [Ranganathan97] 3 . This is the approach we followed for two reasons: It reduces the overhead on applications performance and reduces also the cost of the capture restoration mechanism. Since this mechanism has many applications, we believe that it is a basic functionality which must be integrated within ....

M. Ranganathan, A. Acharya, S. D. Sharma et J. Saltz. Network-aware Mobile Programs . Proceedings of the USENIX Annual Technical Conference, Anaheim, California, 1997. http://www.cs.umd.edu/~acha/

....means to monitor the availability and quality of resources, either on demand or continuously. This monitoring can be easily performed through standard Klava operations, taking advantage of timeouts, so implementing both synchronous and asynchronous monitoring. Like Sumatra, other systems, such as [11, 32, 35], implement strong mobility in Java, by modifying the Java Virtual Machine, to access, save and restore the execution state of threads; however, this solution can jeopardize one of the most desirable advantages of Java: portability across platforms. Indeed, one needs to run the modi ed version of ....

M. Ranganathan, A. Acharya, S. Sharma, and J. Saltz. Network-aware Mobile Programs. In Proc. of the USENIX Annual Technical Conf., pages 91-103. USENIX, 1997.

....was achieved inside the language interpreter; however Telescript does not provide migration of multiple threads. The successor of Telescript, Odyssey [11] which is implemented in Java, does not provide strong mobility transparently. There are systems providing strong mobility in Java, such as [5, 19, 20], that modify the Java Virtual Machine, to access, save and restore the execution state of threads; however this solution puts at risk one of the most desirable advantages of Java: portability across platforms. Indeed one needs to run the modi ed version of the JVM in order to use such agents. ....

M. Ranganathan, A. Acharya, S. Sharma, and J. Saltz. Network-aware Mobile Programs. In Proc. of the USENIX Annual Technical Conf., pages 91-103. USENIX, 1997.

....when required, the thread state must be extracted from the process checkpoint independently. In Java, object serialization allows the objects to be saved independently. The thread stacks are not exposed by the Java VM. In order to save thread stacks, existing schemes either modify the Java VM [12], or instrument the Java code [6] An important issue in implementing shared objects is defining what exactly a shared object access is. This has impact on the number of accesses, o. As we have just seen, the smaller the value of o, the lower would be the overhead in the balanced protocol. ....

M. Ranganathan, A. Acharya, S. D. Sharma, and J. Saltz. Network-aware Mobile Programs. Proc. of Usenix '97 Anaheim, CA, 1997.

....the network and carry out tasks on their behalf [1] An agent can be defined as a whole computational component together with its state, the code it needs, and some resources required to carry out its task. Telescript [2] Aglets [3] Agent TCL [4] Concordia [5] Mole [6] TACOMA [7] Sumatra [8], Ara [9] MOA [10] and Voyager [11] are some of the most recent and advanced enabling technologies for mobile agents. It is a natural question to ask if or how mobile computation can be smoothly integrated with a previously existing paradigm. By smoothly we mean without having to make ....

M. Ranganathan, A. Acharya, S.D. Sharma, and J. Saltz. Network-aware mobile programs. In Proceedings of the USENIX 1997 Annual Technical Conference, pages 91--103, January 1997.

....computable function may be used. This is similar in spirit with the work of Blaze and Feigenbaum [10] except that by unifying the agent language and the trust speci cation language, the programmer s work is simpli ed. 5 Mobile Java Other approaches to providing mobility to Java programs [26] requires modifying the interpreter. In Sanctuary, we intend to provide a mechanism to migrate Javabased agents that can run on unmodi ed Java interpreters [15] This strategy will enable wider acceptance of mobile agents, leveraging o of the work done by Sun Javasoft and other companies. This ....

Mudumbai Ranganathan, Anurag Acharya, Shamik D. Sharma, and Joel Saltz. Network-aware mobile programs. In Proceedings of the Usenix 1997 Annual Technical Conference. Usenix, 1997.

....words, they are able to handle asynchronous events and possibly react by moving the code to a di erent site. Sumatra provides strong mobility. The use of Sumatra in creating network aware mobile programs which can adapt to variations in network conditions has been documented by Ranganathan et al. [25]. In this application, Adaptalk, a Java based Internet chat application takes advantage of the agent support to dynamically place the server, hence reducing the response time. TACOMA: The TACOMA (Tromso And Cornell Mobile Agents) 11] mobile agent system focuses upon the provision of operating ....

M. Ranganathan, A. Acharya, S. D. Sharma and J. Saltz, "Network-aware Mobile Programs" Proc. of the USENIX Annual Technical Conference, Anaheim, California, 1997.

....their browser, the applet is downloaded and executed on their machine, where it typically presents some complex interface for interacting with back end databases and other Web resources. A more complex example is the chat server that was implemented on top of the Sumatra mobile agent system [RASS97, RAS96] A chat server simply allows multiple users to chat online; each user types whatever they want, and what they type is displayed on the screens of all the other users. The Sumatra chat server is written as a mobile Java agent. It monitors network latencies, and continually moves to the ....

.... xed location server were tested in a local area network (using Internet traces to introduce Internet sized transmission delays) the maximum latency between the moving Sumatra server and any of its clients was two to four times smaller than between the xed location server and its clients [RASS97] 2.2.4 Disconnected operation and mobile computing A mobile computer often disconnects from the network, and when it reconnects, it might nd itself with a radically di erent network connection in terms of bandwidth, latency or reliability. The simple ability of agents to migrate to the other ....

[Article contains additional citation context not shown here]

M. Ranganathan, Anurag Acharya, Shamik Sharma, and Joel Saltz. Network-aware mobile programs. In Proceedings of the 1997 USENIX Technical Conference, pages 91-104, 1997.

.... ability to save and restore the state of an executing object (e.g. there is no access to the program counter or stack) Therefore, it is not possible to fully support the migration of actively executing objects without modifying the implementation of the virtual machine (i.e. the interpreter) [22] or without preprocessing [8] the Java source code. As a result, Ajents supports the immediate migration of objects which are currently executing methods by using checkpointing and roll back. Ajents is able to accomplish this by checkpointing the object before beginning each remote method ....

M. Ranganathan, A. Acharya, S. Sharma, and J. Saltz. Network-aware mobile programs. In Proceedings of USENIX'97, 1997.

....to the user s personal environment and preferences, and to the general system environment on the two machines, can make providing a consistent execution environment challenging. We hope to obtain insight on this problem from projects that execute processes remotely for different purposes [12] [17], 18] These and similar projects have dealt successfully with these challenges. 24 Mobile Computing and Communications Review, Volume 2, Number 1 Fourth, the infrastructure will need to assist the user in determining when to execute a task remotely. As the results in Section 3 show, only jobs ....

....servers to run major processes. Local computing is not possible here, even when it is less powercostly. For many years, process migration and delegation have been discussed in the computer community for various purposes: dynamic load balancing, improved reliability, reduced network traffic. 18] [17], and [12] discuss these issues. However, power consumption has not previously been identified as a benefit of process migration. VI. Conclusions The experimental results presented in this paper demonstrate that portable computers that execute their large tasks remotely can save significant ....

M. Ranganathan, Anurag Acharua, Shamik D. Sharma and Joel Saltz, "Network-Aware Mobile Programs," USENIX 1997 Annual Technical Conference, January 1997.

....mobility [3] the agent must make its own arrangements for preserving its execution state on transport. We believe strong mobility is preferable but is currently too difficult to implement in Java. There are a couple of experimental systems that achieve strong mobility by modifying the JavaVM [14] [22], but a standard mechanism has yet to be defined. Some of the advantages of mobile agents are well understood [7] 18] If an agent is using lots of bandwidth or needs low latency access to a resource, then it can be more efficient for the agent to move to the resource s cell than to communicate ....

M. Ranganathan, Anurag Acharya, Shamik Sharma, and Joel Saltz. Network-aware Mobile Programs. In Proceedings of the 1997 USENIX Technical Conference, pages 91--104, 1997. http://www.cs.umd.edu/  acha/papers/ usenix97-submitted.html

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M. Ranganathan, A. Acharya, S. Sharma, and J. Saltz. Network-aware Mobile Programs. In Proceedings of the USENIX 1997.

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M. Ranganathan, A. Acharya, S. Sharma, and J. Saltz. Network-aware Mobile Programs. In Proceedings of the USENIX 1997.

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M. Ranganathan, A. Acharya, S. Sharma, and J. Saltz. Network-aware mobile programs. In Proceedings of USENIX'97, 1997.

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Ranganathan, M., Acharya, A., Sharma, S., Saltz, J.: Network-aware Mobile Programs. In: Proceedings of the USENIX 1997 Annual Technical Conference. (1997)

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Ranganathan, M., Acharya, A., Sharma, S., Saltz. J.,., "Network-aware Mobile Programs", Proceedings of the Annual Usenix 1997 Conf., January 6-10, Anaheim, California, USA.

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