Due to its bandwidth efficiency, multicast makes a group-centric communication more viable in wireless ad hoc networks with limited radio resources. PIM-SM, a de facto standard multicast protocol known for its high scalability, is a good fit for a large-scale ad hoc network. However, it does not provide a robust multicast communication under RP outage and host mobility. In this paper, we propose a robust way of configuring PIM-SM using Anycast RP in wireless ad hoc networks. We analyze the impact of cardinality and locations of anycast RPs on the network performance under node mobility. Based on these observations, we find metrics for near-optimal cardinality of anycast RPs and propose a novel RP selection scheme. The proposed scheme is proven to make PIM-SM robust against mobility while satisfying QoS requirements and maintaining the scalability of PIM-SM.

A set of graph augmentation algorithms is introduced to model a class of timing faults in timed-EFSM models. It is shown that the test sequences generated based on our models can detect 1 -clock andn-clock timing faults and incorrect timer setting faults in an implementation under test (IUT). It is proven that the size of the augmented graph resulting from our augmentation algorithms is on the same order of magnitude as that of the original specification.

Virtual backbone structures are of fundamental importance in mobile ad hoc networks (MANET) as they are essential to support various applications such as service discovery and provision, multicast, routing, etc. In this paper we consider a very natural approach for the creation of virtual backbones, based on weakly-dominating sets, and investigate its security properties against Byzantine adversaries that can corrupt up to a given threshold of nodes. We formalize the notion of secure protocols for the creation and management of virtual backbones, and design a distributed protocol generating weakly-dominating virtual backbones, that is both efficient, according to standard MANET metrics, and secure against Byzantine adversaries corrupting up to a given threshold of nodes

The existing naming schemes for pooling resources are suitable only for static networks. We propose dynamic survivable resource pooling (DSRP) that provides a survivable naming scheme to the pool users in mobile ad-hoc networks. DSRP dynamically places the name servers (NSs) on a virtual backbone (VB): a highly distributed, scalable, and survivable mesh network formed and maintained through one-hop beacons. In this paper, DSRP focuses on pooling resources such as servers and services that are common in robotics and battlefield applications. It provides an abstraction of all the functionally equivalent servers, whereby the client can access these servers as a single entity, termed server pool. A distributed backbone mesh of NSs is used to propagate service registrations, requests, and replies.

The current SCTP specification is not aware of QoS provided by a network. As a result, it is unable to support preferential treatment of the individual streams. We introduce the concept of dividing an association into subflows (SFs) so that the modified SCTP can support different levels of QoS. We define the necessary modifications to the current SCTP for this capability: namely, new data and SACK chunk formats to implement congestion control for each SF. To avoid the problem of false sharing, we modify SCTP such that each SF has its own congestion control mechanism. Using analytic models, we show that the modified SCTP is expected to perform better than the original SCTP. We verify these results through simulation experiments, where we observed that modified SCTP is able to take advantage of the diff-serv network and provides a better throughput.

Reliable server pooling (RSP) allows a pool of redundant information sources to be viewed as a single transport endpoint and, therefore, it is able to provide persistent connections and balanced traffic for different applications. The Internet Engineering Task Force RSerPool Working Group has proposed an architecture to implement the RSP; it defines an overlay network providing an upper layer protocol or an application with a range of reliability services, from simple server selection to a fully automatic session-failover capability. The simulation experiments conducted in both wired and wireless environments show that the current version of the RSerPool works well in fixed and relatively reliable environments, but its performance worsens rapidly as the networks become more unreliable or mobile. The issues we have identified in wireless mobile ad hoc networks include network partition, high signaling overhead, difficulty in synchronization among name servers, and excessive aggressiveness in handling failures. Alternative design options for the RSP in wireless and mobile environments are introduced and evaluated.

The reliable server pooling is a framework to handle session failures and increase the system's availability by providing several reliability services: from simple server selection to a full session-failover capability. In the IETF RSerPool, servers with equivalent functionality are pooled together; when a particular server becomes unavailable, a client application can transparently switched over to another server in the pool. Extensive simulation experiments identified two main shortcomings of the RSerPool in wireless mobile networks: the inaccuracy of the failure-detection mechanism for pooled servers, and high overhead of finding name servers. We introduce and evaluate alternative mechanisms that tackle these problems.

The reliable server pooling allows redundant information sources to be viewed as a single transport endpoint, and therefore is able to provide persistent connections and balanced traffic. The IETF RSerPool Working Group has proposed an architecture to implement the reliable server pooling. We conducted a number of simulation experiments with the current definitions of the RSerPool protocols to quantify their performance in both wired and wireless environments. The simulation results show that the RSerPool works well in fixed and relatively reliable environments, but its performance worsens rapidly as the networks become more unreliable or mobile. The issues we identified in wireless mobile ad-hoc networks include network partitioning, high signaling overhead, and excessive aggressiveness in handling failures. These problems are partly due to the heavy reliance of the RSerPool architecture on the reliability of the underlying network,, which is unlikely to be guaranteed in a wireless mobile ad-hoc environment.

We present a new model for testing real-time protocols with multiple timers, which captures complex timing dependencies by using simple linear expressions involving timer-related variables. This new modeling technique, combined with the algorithms to eliminate inconsistencies, allows generation of feasible test sequences without compromising their fault coverage. The model is specifically designed for testing to avoid performing full reachability analysis, and to control the growth of the number of test scenarios. Based on extended finite state machines, it is applicable to languages such as SDL, VHDL, and Estelle. The technique models a realistic testing framework in which each I/O exchange takes a certain time to realize and timers can be arbitrarily started or stopped. A software tool implementing this technique is used to generate test cases for the US Army wireless standard MIL-STD 188-220.

We present experience with improving the requirements engineering process for a telecommunications electronic clearinghouse that connects multiple trading partners. Software failures and faults were traced back to problems in the semi-structured requirements, which were written as message specifications (called "business rules") in a nonstandardized format using MS Word. To remedy these problems, we first designed a highly structured representation of the. essential information in Extensible Markup Language (XML), supported by XML Schema for precisely defining the requirements structure. Second, we developed XLEdit-a custom GUI for editing the XML documents in a friendly way while preserving their information structure. Third, to assist the requirements engineers with automated migration of the existing business rules, we developed a converter for translating from MS Word to the target XML format. The investment in the technology for structured requirements editing and validation is expected to increase customer satisfaction and dramatically improve the efficiency of the clearinghouse service.

Abstract We present experience gained in automating tests for an operations support system. A major portion of the effort was devoted to extending a commercial test tool so that testers could easily manipulate graphical user interface (GUI) objects on two implementations of the application. For this purpose, we developed a test automation library as support infrastructure for writing tests. The challenges and tradeoffs are discussed such as simplicity/complexity for a tester versus a library developer, hiding/exposing window hierarchy to the tester, providing common methods for different types of GUI objects, transparently manipulating custom GUI widgets, and coping with data‐dependent test cases. We discuss the requirements of test code reusability, maintainability, and portability, and describe the solutions we found. In addition, we offer observations about benefits and pitfalls of test automation, our recommendations for maximizing return on investment, and results from automating a variety of tests. Copyright © 2002 John Wiley & Sons, Ltd.