On Fault Identification In Networks by Passive Testing - On Fault Identification in Networks by Passive Testing Raymond E Miller1 Department of Computer

On Fault Identification In Networks by Passive Testing - On...

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On Fault Identification in Networks by Passive Testing Raymond E. Miller 1 Khaled A. Arisha Department of Computer Science Department of Computer Science University of Maryland, University of Maryland, College Park, MD 20742 College Park, MD 20742 [email protected] [email protected] 1 Some of this work was done while consulting for Bell Laboratories, Lucent Technologies. Abstract In this paper, we employ the finite state machine (FSM) model for networks to investigate fault identification using passive testing. First, we introduce the concept of passive testing. Then, we introduce the FSM model with necessary assumptions and justification. We introduce the fault model and the fault detection algorithm using passive testing. Extending this result, we develop the theorems and algorithms for fault identification. An example is given illustrating our approach. Then, extensions to our approach are introduced to achieve better fault identification. We then illustrate our technique through a simulation of a practical X.25 example. Finally future extensions and potential trends are discussed. 1 Introduction Due to the rapid growth in Telecommunication networks and the fast evolution in technology, the need for a more efficient and effective network management approach becomes more urgent. The International Standard Organization (ISO) has defined network management for the Open System Interconnection (OSI) seven-layer model in terms of five functional areas: fault management, configuration management, accounting management, performance management, and security management [7]. A considerable effort has been made to standardize network management protocols and develop network management systems, such as the Simple Network Management Protocol (SNMP) and the Common Management Information Protocol (CMIP) [6]. However, there is much to be done towards formally specifying problems in network management and developing formal techniques to solve these problems. Our work models the network using the formal approaches of Finite State Machine (FSM) as is done in [1], however we study the fault identification problem rather than simply the fault detection. The work presented here focuses on one critical functional area of network management; namely fault management. There are two approaches to test a network for fault management: active testing and passive testing. The most commonly used approach for fault management is active testing, which gathers information actively. By “actively” we mean injecting test messages into the network to aid in finding network faults. Active testing has techniques in common with conformance testing of protocols. Conformance testing is used to test protocols off-line to insure that a protocol implementation conforms to its specification. Test sequences are generated from the specification. These input sequences are applied to the implementation to see whether the produced output sequence matches the expected one given by the specification. In contrast, fault management for networks takes place while the network is in use. Because of this, it
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