Steve R. Wilbur

Lighthouses for Scalable Distributed Location

This paper introduces Lighthouse, a scalable location mechanism for wide-area networks. Unlike existing vector-based systems such as GNP, we show how network-location can be established without using a fixed set of reference points. This lets us avoid the communication bottlenecks and single-points-of-failure that otherwise limit the practicality of such systems.

Building distributed systems with remote call

Remote procedure call is gaining popularity assimple, transparent and useful paradigm for building distributed systems. Ideal transparency means that remote procedure calls are in distinguishable from local ones. This is usually only partially achievable. This paper discusses those implementation decisions which affect transparency and intrude on the design of distributed applications built using remote procedure call.

Secure automated document delivery

A model for secure delivery of documents is proposed, and a prototype system based on earlier work on secure electronic mail and automated document delivery systems is described. In the proposed architecture, security protection is provided for both document requests and the actual documents delivered. Electronic mail protocols are used for document requests and delivery, although file transfer protocols could be used in some circumstances. The document delivery system background is discussed, and the client-server model for the secure system is presented. The security philosophy, requirements, policy, and techniques are dealt with next. The criterion for validation is analyzed, the relationship to OSI (Open systems interconnection) is shown, implementation issues are discussed, and the direction of future efforts is pointed out.<<ETX>>

Securing the Internet metering and billing

In the near future, billing for network services will not only be concerned with time or volume based accounting but also in ways of measuring the quality of the service provided. Dynamic price schemes, such as congestion-based charging, have been proposed. In some of these models, the charging infrastructure relies on the distribution of electronic tariffs to end-users machines. The tariff structure includes the price information and an algorithm to calculate the charge. Thus, the monitoring of network usage according to this tariff is essential within these frameworks. However, little attention has been given to the security issues associated with Internet metering in these schemes. This has had a great impact on the new models proposed today, since security has become a major concern in open networks. Systems that naturally have incentive to fraud, such as metering systems used for billing purposes, must deal with security threats in large scale environments. The article compiles the security issues of a dynamic networked system where electronic tariffs and service level agreement (SLA) structures are distributed among service providers and customers. To address these issues, a set of security protocols is outlined.

A fair guaranteed down-link sharing scheme for cellular packet switched networks

In this paper, we study a fair down-link sharing scheme to control wireless link congestion in cellular packet switched networks. We analyse the unbounded fairness problems and disordered packet delivery induced by a handover in which we apply the weighted fair queueing (WFQ) discipline in a base station (BS). Based on the analysis, we propose a bounded fair scheduling discipline for BSs to distribute guaranteed bandwidth fairly to a mobile host (MH) regardless of congestion and handovers. We also propose a new handover protocol associated with the proposed scheduling discipline to remedy the disordered packet delivery phenomenon. The simulation results show that an increase in unfairness from a handover is cumulative and disordered packet delivery may occur during a handover. Finally, the simulation results also show that our proposed scheme can solve these observed problems.

Privacy enhanced electronic mail

The progress of work at University College of London in implementing a prototype model of a privacy-enhanced messaging (PEM) system is reported. The design of model is specified by the DARPANET IAB Privacy Task Force RFC 1040. The model is one which provides privacy, integrity, and authentication of messages transmitted in a typical electronic-mail system. The design and implementation experience of the prototype model is set out and several potential refinements to the model are suggested for future development.<<ETX>>

Authentication in a heterogeneous environment

This paper considers how a mechanism might be set up to provide authentication of users and servers. The scheme proposed aims to deal with simple processors which are unmanaged, as well as managed timesharing systems. It would provide authentication tokens which can be included in the applications protocols. Much of the difficulty of the scheme is concerned with building a distributed secure database for private keys.

Supporting Asynchronous Collaboration in Academia

Numerous groupware products are now in use in many commercial environments. These systems typically integrate a number of tools for communication, workflow, database-sharing, contact management, and group scheduling, and operate across a variety of environments. This chapter looks at the use of groupware in organisations, and looks at a range of groupware which supports asynchronous collaboration. It identifies three categories of asynchronous collaboration in an academic environment: teaching; research; and support for teaching and research. It then looks at how the groupware tools could be used to support asynchronous collaboration in academia.

Performance evaluation of dynamic supporting algorithms

The widely used performance measures for replicated file systems are file availability and reliability. The authors compare such measures for the dynamic supporting algorithm, the dynamic supporting (G) algorithm, and other algorithms, e.g., the available copies and the majority voting algorithms. Since replicas and votes are conceptually separated, the two dynamic supporting algorithms could achieve very high availability and reliability while still keeping storage cost very low, especially with only two replicas. Both stochastic analysis and simulation results are reported. The performance improvement of the dynamic supporting algorithms is demonstrated by the results.<<ETX>>

EdgeMeter: distributed network metering model

In this paper we give an overview of work in progress to propose a distributed metering model using Active Network concepts. The business model which motivates this work poses accounting requirements between different kind of providers and customers. However, security issues also need to be addressed. We briefly describe the problems being investigated which relate to the business model used. We have split the problem mainly into four subtopics. They are concerned with questions of how to control the system through high level policies, how to translate from such policies (tariff/SLA) to a low level device dependent configuration. Other questions are concerned with what threats a system like this may be exposed to and what the limitations are in terms of system performance when measuring network traffic.