Corey Kosak

An architecture for optimal all-to-all personalized communication

In all-to-all personalized communication (AAPC), every node of a parallel system sends a potentially unique packet to every other node. AAPC is an important primitive operation for modern parallel compilers, since it is used to redistribute data structures during parallel computations. As an extremely dense communication pattern, AAPC causes congestion in many types of networks and therefore executes very poorly on general purpose, asynchronous message passsing routers. We present and evaluate a network architecture that executes all-to-all communication optimally on a two-dimensional torus. The router combines optimal partitions of the AAPC step with a self-synchronizing switching mechanism integrated into a conventional wormhole router. Optimality is achieved by routing along shortest paths while fully utilizing all links. A simple hardware addition for synchronized message switching can guarantee optimal AAPC routing in many existing network architectures. The flexible communication agent of the iWarp VLSI component allowed us to implement an efficient prototype for the evaluation of the hardware complexity as well as possible software overheads. The measured performance on an 8 × 8 torus exceeded 2 GigaBytes/sec or 80% of the limit set by the raw speed of the interconnects. We make a quantitative comparison of the AAPC router with a conventional message passing system. The potential gain of such a router for larger parallel programs is illustrated with the example of a two-dimensional Fast Fourier Transform.

Automating the layout of network diagrams with specified visual organization

Network diagrams are a familiar graphic form that can express many different kinds of information. The problem of automating network-diagram layout has therefore received much attention. Previous research on network-diagram layout has focused on the problem of aesthetically optimal layout, using such criteria as the number of link crossings, the sum of all link lengths, and total diagram area. In this paper the authors propose a restatement of the network-diagram layout problem in which layout-aesthetic concerns are subordinated to perceptual-organization concerns. The authors present a notation for describing the visual organization of a network diagram. This notation is used in reformulating the layout task as a constrained-optimization problem in which constraints are derived from a visual-organization specification and optimality criteria are derived from layout-aesthetic considerations. Two new heuristic algorithms are presented for this version of the layout problem: one algorithm uses a rule-based strategy for computing a layout; the other is a massively parallel genetic algorithm. The authors demonstrate the capabilities of the two algorithms by testing them on a variety of network-diagram layout problems. >

Darwin: customizable resource management for value-added network services

The 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, and be customizable so services and applications can tailor resource usage to optimize their performance. The Darwin project has developed a set of customizable resource management mechanisms that support value-added services. We present and motivate these mechanisms, describe their implementation in a prototype system, and describe the results of a series of proof-of-concept experiments.

Network support for application-oriented QoS

Addresses a dilemma raised by recent advances in networking technology, which provide support both for a rich variety of qualities of service (QoSs) and for applications that connect many end-points. Together these features encourage the development of complex multi-party applications that use a diverse set of data types. This raises a two-fold problem: how do application designers choose and specify the many QoS parameters that drive the ultimate performance of their applications; and how does the network efficiently manage its resources to support such a rich application mix? Our approach to this problem is to allow applications to be built around value-added services that encapsulate a variety of simpler resources. This enables both the specification of QoS in terms meaningful to applications, and global optimization of resource allocation across multiple streams and data types. We present a network architecture and a preliminary implementation that explicitly support the notion of application-oriented QoS for complex network services. The key concept is that of service brokers, which applications and service providers use to identify the network resources needed to meet QoS and cost objectives. Service brokers can incorporate a detailed understanding of an application domain, allowing them to make intelligent tradeoffs and to interact with applications and service providers at a high level. They can be hierarchical, in the sense that one broker can invoke the services of another broker. Finally, they provide the ability to deal with heterogeneous networks and hierarchical resource management.

Fine grain parallel communication on general purpose LANs

Commodity workstations connected by commodity networks are increasingly viewed as an economically viable alternative to tightly coupled multiprocessors. In recent years, many scientific computing applications have been able to make effective use of various types of workstation clusters. The main difference between workstation clusters and the more traditional, tightly coupled distributedmemory systems is communication performance. In this paper we present a host-network interface architecture that supports efficient remote memory writes across standard ATM networks, bringing performance closer to that of special-purpose, tightly coupled systems for a large class of applications. We show that minimal hardware support is required on the adaptor, and that the required features are very similar to those already needed on adaptors for high-speed networks. We also describe an implementation of this architecture, and present measurements of communication performance indicating its effect on the breadth of applications that can use a general purpose network m an effective way.

Buffer management and flow control in the Credit Net ATM host interface

Among the many benefits of ATM networking are the potential for connections with negotiated quality-of-service (QoS) guarantees and application-specific data management at network endpoints. We describe the architecture of a PCI bus host adapter for OC-3 and OC-12 ATM, focusing on challenges in the areas of buffer management and flow control, since these are vital to realizing the bandwidth and QoS potential of ATM endpoint hosts.