here is a flurry of activity in the networking community developing advanced services networks. Although the focus of these efforts varies widely from per-flow service definitions like integrated services (IntServ) [1,2] to service frameworks like Xbind [3], they share the overall goal of evolving the Internet service model from what is essentially a basic bitway pipe to a sophisticated infrastructure capable of supporting novel advanced services.In this article we consider a network environment that comprises not only communication services, but storage and computation resources as well. By packaging storage/computation resources together with communication services, value-added service providers will be able to support sophisticated services such as intelligent caching, video/audio transcoding and mixing, virtual private networking, virtual reality games, and data mining. In such a service-oriented network, value-added services can be composed in a hierarchical fashion: applications invoke high-level service providers, which may in turn invoke services from lower-level service providers. Providers in the top of the hierarchy will typically integrate and add value to lower-level services, while the lowest-level services will supply basic communication and computational support. Since services can be composed hierarchically, both applications and service providers will be able to combine their own resources with resources or services delivered by other service providers to create a high-quality service for their clients. The design of such a service-oriented network poses challenges in several areas, such as resource discovery, resource management, service composition, billing, and security. In this article we focus on the resource management architecture and algorithms for such a network.Service-oriented networks have several important differences from traditional networks that make existing network resource management inadequate. First, while traditional communication-oriented network services are provided by switches and links, value-added services will have to manage a broader set of resources that includes computation, storage, and services from other providers. Moreover, interdependencies between differ-0890-8044/01/$10.00 AbstractThe Internet is rapidly changing from a set of wires and switches that carry packets into a sophisticated infrastructure that delivers a set of complex value-added services to end users. Services can range from bit transport all the way up to distributed value-added services like video teleconferencing, virtual private networking, data mining, and distributed interactive simulations. Before such services can be supported in a general and dynamic manner, we have to develop appropriate resource management mechanisms. These resource management mechanisms must make it possible to identify and allocate resources that meet service or application requirements, support both isolation and controlled dynamic sharing of resources across services and applications sharing physical resources, a...

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We present a method for automatically extracting parallel prefix programs from sequential loops, even in the presence of complicated conditional statements. Rather than searching for associative operators in the loop body directly, the method rests on the observation that functional composition itself is associative. Accordingly, we model the loop body as a multivalued function of multiple parameters, and look for a closed-form representation of arbitrary compositions of loop body instances. Careful analysis of conditionals allows this search to succeed in cases where existing automatic methods fail. The method has been implemented and used to generate code for the iWarp parallel computer.

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Highly parallel VLSI computing structures consist of many processing elements operating simultaneously. In order for such processing elements to communicate among themselves, some provision must be made for synchronization of data transfer. The simplest means of synchronization is the use of a global clock. Unfortunately, large clocked systems can be difficult to implement because of the inevitable problem of clock skews and delays, which can be especially acute in VLSI systems as feature sizes shrink. For the near term, good engineering and technology improvements can be expected to maintain the feasibility of clocking in such systems; however, clock distribution problems crop up in any technology as systems grow. An alternative means of enforcing necessary synchronization is the use of self-timed, asynchronous schemes, at the cost of increased design complexity and hardware cost. Realizing that different circumstances call for different synchronization methods, this paper provides a spectrum of synchronization models; based on the assumptions made for each model, theoretical lower bounds on clock skew are derived, and appropriate or best-possible synchronization schemes for large processor arrays are proposed. One set of models is based on assumptions that allow the use of a pipelined clocking scheme, where more than one clock event is propagated at a time. In this case, it is shown that even assuming that physical variations along clock lines can produce skews between wires of the same length, any one-dimensional processor array can be correctly synchronized by a global pipelined clock while enjoying desirable properties such as modularity, expandability and robustness. This result cannot be extended to two-dimensional arrays, however—the paper shows that under this assumption, it is impossible to run a clock such that the maximum clock skew between two communicating cells will be bounded by a constant as systems grow. For such cases or where pipelined clocking is unworkable, a synchronization scheme incorporating both clocked and “asynchronous” elements is proposed.