Thesis (M.S.)--Virginia Polytechnic Institute and State University, 1994. / Vita. Abstract. Includes bibliographical references (leaves 83-89). Also available via the Internet.

D.Phil. (Computer Science) / Please refer to full text to view abstract

Over the past few years there has been an increasing tendency to carry voice on IP networks as opposed to the PSTN and other switched circuit networks. Initially this trend was favoured due to reduced costs but occurred at the expense of sacrificing the quality of the voice communications. Switched circuit networks have therefore remained the preferred carrier-grade voice communication network, but this is again changing. The advancement in improved quality of service (QoS) of real-time traffic on the IP network is a contributing factor to the anticipated future of the IP network supplying carrier-grade voice communications. Another contributing factor is the possibility of creating a new range of innovative, state-of-the-art telephony and communications services that acquire leverage through the intelligence and flexibility of the IP network. The latter has yet to be fully explored. Various protocols exist that facilitate the transport of voice and other media on IP networks. The most well known and widely supported of these is H.323. This work presents and discusses H.323 version 4 service creation. The work also categorises the various H.323 services and presents the mechanisms provided by H.323 version 4 that have facilitated the development of the three services I have developed, EmailReader, Telgo323 and CANS.

Formal Description Techniques allow for the use of automated tools during the specification and development of communication protocols. Estelle is a standardized formal description technique developed by ISO to remove ambiguities in the specification of communication protocols and services. The UBC Estelle-C compiler automates the implementation of protocols by producing an executable C implementation directly from its Estelle specification. In this thesis, we investigate the automated protocol implementation methodology using the Estelle-C compiler. First, we describe the improvements made to the compiler to support the latest version of Estelle. Then, we present and discuss the semiautomated implementations of the LAPB protocol in the CCITT X.25 Recommendation and the RTS protocol in the CCITT X.400 MHS series using this compiler. Finally, we compare the automatic and manual protocol implementations of LAPB and RTS protocols in terms of functional coverage, development time, code size, and performance measure. The results strongly indicate the overall advantages of automatic protocol implementation method over the manual approach. / Science, Faculty of / Computer Science, Department of / Graduate

A compiler which achieves automatic implementation of network protocols by transforming specifications written in FDT into C programs is presented. A brief introduction to the the fundamentals of FDT, a standard language developed by ISO/TC97/SC 16/WG 1 Subgroup B for specifying network protocols, is given. We then present an overview of the compiler and discuss the problem of PASCAL to C translation. Transformation of a FDT specification into code is explained and illustrated by two implementation examples. The first example illustrates the implementation strategy by tracing the processing of a simple protocol. The second example demonstrates the validity of using automatically generated implementations by showing how a communication path was established between two hosts using code generated for the alternating bit protocol. / Science, Faculty of / Computer Science, Department of / Graduate

Different computer systems have their own ways of representing, storing and managing files. One approach to facilitate file transfers among systems in a heterogeneous networked environment is for each system to locally map files for transfer onto a virtual filestore (VFS). Conceptually, a virtual filestore provides a universal model for describing files and how they can be manipulated. The ISO File Transfer, Access and Management (FTAM) protocol offers one such virtual filestore model. This thesis reports on the prototype implementation of a useful subset of the ISO FTAM protocol for the UNIX 4.2 BSD¹ file system. We call this implementation ubcFTAM. UNIX files, ordinarily regarded as unstructured, can be endowed with some internal structure thereby allowing the transfer of selective portions of a file. Furthermore, the implementation offers several file attributes not supported by UNIX. ubcFTAM runs on several Sun Workstations² interconnected by a 10 Mbps Ethernet. Some performance data of ubcFTAM are also presented. This thesis also identifies several aspects of the specifications that are ambiguous or that are inadequate, warranting further studies. Resolutions for these issues are discussed. We hope this experience will be useful to others planning to implement FTAM for UNIX systems. ¹UNIX is a registered trademark of American Telephone and Telegraph Bell Laboratories. BSD denotes Berkeley Standard Distribution ²SUN Workstation is a trademark of Sun Microsystems, Inc. / Science, Faculty of / Computer Science, Department of / Graduate

This thesis addresses the problem of conformance testing of communication protocol implementations. Test sequence generation techniques for finite state machines (FSM) have been developed to solve the problem of high costs of an exhaustive test. These techniques also guarantee a complete coverage of an implementation in terms of state transitions and output functions, and therefore provide a sound test of the implementation under test. In this thesis, we have modified and applied three test sequence generation techniques on the class 0 transport protocol. A local tester and executable test sequences for the ISO class 0 transport protocol have been developed on a portable protocol tester to demonstrate the practicality of the test methods and test methodologies. The local test is achieved by an upper tester residing on top of the implementation under test (IUT) and a lower tester residing at the bottom of the IUT. Tests are designed based on the state diagram of an IUT. Some methodologies of parameter variations have also been used to test primitive parameters of the implementation. Some problems encountered during the implementation of the testers and how they are resolved are also discussed in the thesis. / Science, Faculty of / Computer Science, Department of / Graduate

Movable-slot time-division multiplexing (MSTDM) is a medium access control protocol for the integration of voice and data in local area networks. In this thesis, the performance of this protocol is evaluated through mathematical analysis and simulation. Its application in metropolitan area networks is also studied. For the performance evaluation, a non-pre-emptive priority queuing model is first proposed for analysing the mean data delay characteristic of the slotted non-persistent carrier-sense multiple access with collision detection (CSMA/CD) protocol. Then this analytical approach is extended to the slotted MSTDM protocol with non-persistent data packet transmission, and its mean data delay performance is obtained. Numerical results from the analysis are shown and discussed. Moreover, simulation study of the MSTDM protocol is performed. Through the simulation results, the effects of this protocol on the general delay performances of voice and data are discussed. It is found that if first voice packets, which are generated at the beginning of talkspurts, are given a shorter retransmission delay than data packets, the channel-acquisition delay for voice sources can be reduced without sacrificing the data delay performance significantly. The simulation results are also used to verify the analytical results. As the comparisons show, the accuracy of the analysis is high although it is based on a simple approximate model. For the application of MSTDM in metropolitan area networks, a scheme which alleviates the distance and transmission rate constraints associated with this protocol is described. The approach is to divide the stations in a large area into regional groups, each operating in a different frequency band. Each group forms a sub-network which is part of the metropolitan area network. An access protocol is proposed for interconnecting these sub-networks. Also an analysis which finds the optimum number of sub-networks for interconnection is presented. The criterion is to minimize the mean data delay for communications in a sub-network. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

M.Comm. / In manufacturing companies where raw material is transformed into an endproduct, data pertaining to that transformation process are transported from the physical machine (workstation) to a central database and visa versa. To ensure a successful end-product creation, the company needs to ensure that the data being transported is correct, accurate and trustworthy at all times. As unreliable data seems to be a general problem for large manufacturing companies an investigation was launched to establish what integrity problems are being experienced and possible solutions to these problems in manufacturing companies such as Columbus Stainless Steel. On completion of the investigation it was found that the main causes for late deliveries and data fixes being performed was that the data being transmitted at the source was not always the same data received at the destination, hence a lack of data integrity during data transmission was identified. As it was decided to reduce or eliminate the integrity causes rather than correcting the incorrect results the data transportation process was analyzed. During the analysis the main causes for data integrity problems (errors) were identified. In the environment being investigated, data strings (messages) were created at the workstation and then transported via the use of a transporter (protocol) over an established network to the destination database. The more complex the contents of the message (data string), the more advanced features were needed within the functionality of the protocol to ensure the accurate and correct transmission and processing. Once the main causes for these data integrity errors were identified the investigation was broadened to incorporate the search for various protocols with the ability to reduce or eliminate the causes identified previously.

Master's thesis deals with selection of attributes proper for classification of encrypted traffic, with the extension of NetFlow entries with these attributes and with creating a tool for classify encrypted TLS traffic. The following attributes were selected: size of packets, inter-packet arrival times, number of packets in flow and size of the flow. Selection of attributes was followed by design of extending NetFlow records with these attributes for classifying encrypted traffic. Extension of records was implemented in language C for exporter of the company Flowmon Networks a.s.. Classifier for collector was implemented in language Python. Classifier is based on a model, for which training data were needed. The exporter contains the classifying algorithm too, the place of the classification can be set. The implementation was followed by creation of testing data and evaluation of the accuracy. The speed of the classifier was tested too. In the best case scenario 47% accuracy was achieved.