Showing papers by "Kenneth L. Calvert published in 1998"

Directions in active networks

Abstract: Active networks represent a significant step in the evolution of packet-switched networks, from traditional packet-forwarding engines to more general functionality supporting dynamic control and modification of network behavior. However, the phrase "active network" means different things to different people. This article introduces a model and nomenclature for talking about active networks, describes some possible approaches in terms of that nomenclature, and presents various aspects of the architecture being developed in the DARPA-funded active networks program. Potential applications of active networks are highlighted, along with some of the challenges that must be overcome to make them a reality.

Self-organizing wide-area network caches

Abstract: A substantial fraction of all network traffic today comes from applications in which clients retrieve objects from servers. The caching of objects in locations "close" to clients is an important technique for reducing both network traffic and response time for such applications. In this paper we consider the benefits of associating caches with switching nodes throughout the network, rather than in a few locations. We also consider the use of various self-organizing or active cache management strategies for organizing cache content. We evaluate caching techniques using both simulation and a general analytic model for network caching. Our results indicate that in-network caching can make effective use of cache space, and in many cases self-organizing caching schemes yield better average round-trip latencies than traditional approaches, using much smaller per-node caches.

Payoff adaptation of communication for distributed interactive applications

Abstract: Present distributed applications are not typically designed to adapt to changes in network conditions. In addition, network-based adaptation does not typically consider the requirements of specific applications and, therefore, may take actions contradictory to applications needs. This paper presents a cooperative solution in which a configurable communication layer is used to adapt communication in response to both application requirements and network resource availability. Adaptation decisions are based on (1) payoff functions which capture the application requirements in a functional form, and (2) service availability curves which represent network resource availability. Experimentation with multimedia applications and a variable reliability protocol demonstrates the benefit of using payoff-based adaptation.

Implementing protocols in Java: the price of portability

Abstract: As the number and variety of Web- and network-based applications continues to increase, so does the need for flexible communication protocols and services to support them. Traditionally, a major impediment to deployment of new protocols is the need to upgrade millions of end-systems with compatible implementations. At the same time, Java-a language explicitly designed to support development and distribution of new applications via the Web-is emerging as a (potentially) ubiquitous system platform. It is therefore natural to consider whether Java might speed the introduction of protocols to better support new applications. We investigate the tradeoffs involved in using Java for protocol implementation and deployment. Using insights from a Java-based protocol suite and supporting subsystem we have implemented, we describe the benefits of using the Java language and quantify the performance cost of implementing a protocol in Java for various combinations of interpretation and compilation. We find that the present performance cost of using Java-based protocols is roughly equivalent to four years of hardware performance gains, i.e., interpreted, Java-based protocol performance on current hardware is roughly equivalent to the performance of compiled C code on four-year-old hardware.

Implementing communication protocols in Java

Abstract: As the number and variety of Web- and network-based applications continues to increase, so does the need for flexible communication protocols and services to support them. Traditionally, a major impediment to deployment of new protocols and services is the need to upgrade millions of end systems with compatible implementations. At the same time, Java-a language explicitly designed to support development and distribution of new applications via the Web-is emerging as a (potentially) ubiquitous system platform. It is therefore natural to consider whether Java might speed the introduction of protocols to better support new applications. We discuss the suitability of Java as an environment for implementing and deploying communication protocols. Using insights from a Java-based protocol suite and supporting protocol subsystem we have implemented, we describe the benefits of using Java for protocol development and deployment, and how protocol programmers can implement protocols taking advantage of those benefits.

Network Support for Multicast Video Distribution

Abstract: Multicast video distribution in a best-eeort environment presents challenges to system designers, including heterogeneity in the bandwidth availability on the paths from the sender to the receivers and dynamic behavior in the network and set of receivers over time. Classic approaches to dealing with dynamic conditions involve adaptation at the sender (for unicast) and adaptation driven by the receivers (for multi-cast). Both approaches have limitations that aaect the quality of video received. In this paper, we consider a third option for the location of adaptation, namely: in the network. Since the adaptation is applied inside the network, the time and place for adaptation can better match network conditions. Further , the adaptation can occur more rapidly, without the need for route changes. Finally, the adaptation can occur at ner granularity, providing better quality and more graceful degradation to receivers. The point of this paper is to quantify the potential bene-ts of in-network adaptation for multicast video distribution .

Payoff-based communication adaptation based on network service availability

Abstract: Interactive applications will continue to push the limits of available network bandwidths, processing speeds, and other computing resources These applications present challenges concerning the specification of service requirements for their multiple types of data transfer and the online management of service quality We present a cooperative solution in which a configurable communication layer is used to adapt communication in response to both application requirements and network resource availability Adaptation decisions are based on: (1) payoff functions which capture the requirements of the application in a functional form, and (2) service availability curves which represent network resource availability Experimentation with representative multimedia applications demonstrates the benefit of using such payoff based adaptation

Reasoning about active network protocols

Abstract: Active networks allow users to "program" the network infrastructure, by injecting information that describes or controls a distributed algorithm to be executed for the user by the network infrastructure. The nature of the services that can be implemented with such a facility is determined by the programming interface to the active network, i.e. the set of abstractions it exposes to users. The complexity of this interface may range from a few simple parameters to a completely general programming language. We present a model that supports reasoning independently about the correctness of both the underlying active network platform and the algorithms injected into it, in a manner that admits the full range of possible programming interfaces. The model is described without relying on any particular formalism. The interaction between the underlying platform and the user injected program is captured in a specialized form of program composition that allows properties of each to be preserved. The use of the model is illustrated via an example dealing with mobility. For the example, we use the UNITY formalism to be more precise about the programs and properties that are preserved.