We recount some of the most significant and colorful findings of our four-year study of gender issues in the undergraduate computer science program at Carnegie Mellon. We also discuss the subsequent dramatic increase in the number of women in the program. We conclude with recommendations for the most generally useful and effective actions departments can take to attract and retain female students.

The Internet is rapidly evolving from a network that provides basic best-effort communication service to an infrastructure capable of supporting complex value-added services. These services typically have multiple fluffs with interdependent resource requirements. These dependencies provide opportunities to share the same set of resources among related flows over time leading to significant resource gains. We call this type of sharing temporal resource sharing. Exploiting temporal sharing requires support in the signaling protocol that performs resource allocation for the related flows. We examine the problem of supporting temporal sharing in a signaling protocol. This paper makes the case that temporal sharing support must be designed to be extensible, so that service providers can define and implement new sharing behaviors without having to modify the signaling protocol. We motivate the need for an extensible design by showing that the range of possible temporal sharing behaviors is large and supporting the most general forms of temporal sharing is computationally expensive. We then present a design for extensible signaling support for temporal sharing. We have implemented the temporal sharing design presented in this paper in the Beagle signaling protocol. We present an evaluation of the Beagle design and contrast it with other signaling protocols like RSVP and Tenet-2.

There is an emerging class of multi-party, multimedia, multi-flow applications that have a high-level structure that imposes dependencies between resource allocations for flows within the application. These applications are also capable of making intelligent decisions on how resource allocation should be controlled within the application. The development of such applications places new requirements on signaling protocols. This paper outlines these new requirements, discusses ways in which they can be supported and presents the design and implementation of an experimental signaling protocol that supports these requirements. This paper makes the case that for these structured applications, there is an advantage to allocating the resources in an integrated fashion, i.e. computation, storage and communication resources for all the flows are allocated at the same time in a coordinated fashion. The concept of a virtual mesh is introduced as a key abstraction that encapsulates the set of resources that are allocated and managed in an integrated fashion to meet the needs of applications. The paper presents two mesh setup algorithms and a performance evaluation comparing them. Temporal resource sharing within the virtual mesh is discussed in detail and signaling support for temporal sharing at setup and runtime is examined. It is important to characterize temporal sharing since it can significantly reduce the resource requirements for applications. We have implemented the Beagle signaling protocol that supports this integrated resource management model. Beagle representations and mechanisms for mesh setup and temporal sharing are described and a prototype implementation is presented.

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, 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 organizations sharing physical resources, and be customizable so services and applications can tailor resource usage to optimize their performance. The Darwin project is developing a set of customizable resource management mechanisms that support value-added services, In this paper we present these mechanisms, describe their implementation in a prototype system, and describe the results of a series of proof-of-concept experiments.

Multi-service ATM networks will be deployed in internetwork environment to relay IP traffic, including elastic packet flows generated by adaptive network applications. In light of this advance, we devise flow-aware traffic management framework for the better-than-best-effort support of long-duration adaptive IP flows over ATM. It requires the applications and the ATM gateways to periodically exchange hints indicating up-to-dated flow information. This two-way explicit indication mechanism facilitates improved interactions between applications and the network, and increased coordination between end-to-end and link-level traffic control. Network hints help an application to adapt and avoid congestion, while application hints enable an ATM gateway to selectively aggregate and map packet flows into ATM VCs, to regulate CBR bandwidth, and to interoperate with ABR rate-based flow control. Via simulation and experimentation, we demonstrate the feasibility and effectiveness of this framework in balancing application performance and bandwidth efficiency in the use of CBR VCs, and in improving ATM link utilization and avoiding gateway congestion in the use of ABR VCs.

A critical issue in the design of fast packet-switch-based networks is the avoidance of data loss due to congestion. In the context of ATM networks, many link-level congestion control mechanisms for ABR traffic have been proposed and simulated, and a few have been implemented. This paper presents, for the first time, an experimental comparison of several such mechanisms. To drive this comparison, we have developed a set of benchmarks that provide a quantitative characterization of congestion control performance. We also describe a simple but novel technique, the "virtual port card", for implementing both non-native switch behavior and long link delays in ATM networks. This technique allows us to compare a wide range of mechanisms on a single flexible hardware platform. Our measurements show that while several of the ATM flow control mechanisms can eliminate cell loss, there are still several unresolved problems. First, for some traffic scenarios we see very poor application-level performance, especially in the presence of bursty traffic. Second, the performance is very sensitive to the flow control parameters and identifying an appropriate set of parameters is difficult since it depends heavily on the traffic conditions.

For the past year, we have been studying the experiences of undergraduate women studying computer science at Carnegie Mellon University, with a specific eye toward understanding the influences and processes whereby they attach themselves to or detach themselves from the field. This report, midway through the two-year project, recaps the goals and methods of the study, reports on our progress and preliminary conclusions, and sketches our plans for the final year and the future beyond this particular project.

Commodityworkstations 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.

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.