There are a number of known architectural patterns for TCP/IP server design. I present a survey of design choices based on some of the most common of these patterns. I have demonstrated, with working code samples, that most of these architectural patterns are readily portable between UNIX and Windows NT platforms without necessarily incurring significant performance penalties. / Computing / M. Sc. (Computer Science)

Bandwidth management is a topic which is often discussed, but on which relatively little work has been done with regard to compiling a comprehensive set of techniques and methods for managing traffic on a network. What work has been done has concentrated on higher end networks, rather than the low bandwidth links which are commonly available in South Africa and other areas outside the United States. With more organisations increasingly making use of the Internet on a daily basis, the demand for bandwidth is outstripping the ability of providers to upgrade their infrastructure. This resource is therefore in need of management. In addition, for Internet access to become economically viable for widespread use by schools, NGOs and other academic institutions, the associated costs need to be controlled. Bandwidth management not only impacts on direct cost control, but encompasses the process of engineering a network and network resources in order to ensure the provision of as optimal a service as possible. Included in this is the provision of user education. Software has been developed for the implementation of traffic quotas, dynamic firewalling and visualisation. The research investigates various methods for monitoring and management of IP traffic with particular applicability to low bandwidth links. Several forms of visualisation for the analysis of historical and near-realtime traffic data are also discussed, including the use of three-dimensional landscapes. A number of bandwidth management practices are proposed, and the advantages of their combination, and complementary use are highlighted. By implementing these suggested policies, a holistic approach can be taken to the issue of bandwidth management on Internet links.

SMTP, the current protocol for sending electronic mail (e-mail) over the Internet, has for many years suffered from several problems and limitations. When it was designed, well over twenty years ago, the requirements for e-mail were very different from those of today. A message was a text message in English, and both user and machine were explicitly named in the address. The protocol was not designed to transfer other types of messages, and no mechanism was included to verify the identity of the sender. In order to solve these shortcomings, a new e-mail protocol needs to be defined. This report specifies a basis for what such a protocol may look like. The protocol has been designed to be easy to modify and expand, as well as to benefit from more recent ideas and technology. Binary message content is transferred without conversion, sender addresses are verified, and the address format is flexible. Along with the specification of the protocol, a sample implementation has been provided.

The Named Data Networking (NDN) is a new Internet architecture that changes the network semantic from packet delivery to content retrieval and promises benefits in areas such as content distribution, security, mobility support, and application development. While the basic NDN architecture applies to any network environment, local area networks (LANs) are of particular interest because of their prevalence on the Internet and the relatively low barrier to deployment. In this dissertation, I design NDN protocols and implement NDN software, to make NDN communication in LAN robust and efficient. My contributions include: (a) a forwarding behavior specification required on every NDN node; (b) a secure and efficient self-learning strategy for switched Ethernet, which discovers available contents via occasional flooding, so that the network can operate without manual configuration, and does not require a routing protocol or a centralized controller; (c) NDN-NIC, a network interface card that performs name-based packet filtering, to reduce CPU overhead and power consumption of the main system during broadcast communication on shared media; (d) the NDN Link Protocol (NDNLP), which allows the forwarding plane to add hop-by-hop headers, and provides a fragmentation-reassembly feature so that large NDN packets can be sent directly over Ethernet with limited MTU.

M.Sc. / Using the Internet for communication purposes constitutes a high risk, considering the security of such information. The protocol suite used on the Internet is the TCP/IP protocol suite, which consists of the Transmission Control Protocol (TCP) and the Internet Protocol (IP). In a bid to create a basis to support the newly conceptualised ideas, various areas of networking are briefly discussed in this dissertation. The first in this series of areas is that of the OSI layers. This model forms the basis of all networking concepts. The model describes seven layers, of which each performs a certain networking function. The TCP/IP protocol suite fits into this model. Network security and encryption methods are applied and followed to secure information on the Internet. These methods have been used over a long period of time and will also be used to support the newly conceptualised ideas. The main focus of this dissertation falls on the securing of certain parts of the information contained in the headers of both the Transmission Control Protocol (TCP) and the Internet Protocol (IP) in a bid to minimise the amount of data that may be inferred about the communicating parties from these headers. In addition, where multiple routes exist between hosts, the possibility of the deliberate distribution of a single message across these routes is examined. Such distribution will further complicate the task of a hacker attempting to gather information from TCP and IP headers. In addition, such distribution will minimise the possibility that a hacker may assemble a complete message from its constituent parts and that he/she may infer information about the message that cannot be inferred from the isolated parts. The length of a message sent between hosts is one simple example of such information.

Voice over IP (VoIP) is a key enabling technology for the migration of circuit-switched PSTN architectures to packet-based IP networks. However, this migration is successful only if the present problems in IP networks are addressed before deploying VoIP infrastructure on a large scale. One of the important issues that the present VoIP networks face is the problem of unwanted calls commonly referred to as SPIT (spam over Internet telephony). Mostly, these SPIT calls are from unknown callers who broadcast unwanted calls. There may be unwanted calls from legitimate and known people too. In this case, the unwantedness depends on social proximity of the communicating parties. For detecting these unwanted calls, I propose a framework that analyzes incoming calls for unwanted behavior. The framework includes a VoIP spam detector (VSD) that analyzes incoming VoIP calls for spam behavior using trust and reputation techniques. The framework also includes a nuisance detector (ND) that proactively infers the nuisance (or reluctance of the end user) to receive incoming calls. This inference is based on past mutual behavior between the calling and the called party (i.e., caller and callee), the callee's presence (mood or state of mind) and tolerance in receiving voice calls from the caller, and the social closeness between the caller and the callee. The VSD and ND learn the behavior of callers over time and estimate the possibility of the call to be unwanted based on predetermined thresholds configured by the callee (or the filter administrators). These threshold values have to be automatically updated for integrating dynamic behavioral changes of the communicating parties. For updating these threshold values, I propose an automatic calibration mechanism using receiver operating characteristics curves (ROC). The VSD and ND use this mechanism for dynamically updating thresholds for optimizing their accuracy of detection. In addition to unwanted calls to the callees in a VoIP network, there can be unwanted traffic coming into a VoIP network that attempts to compromise VoIP network devices. Intelligent hackers can create malicious VoIP traffic for disrupting network activities. Hence, there is a need to frequently monitor the risk levels of critical network infrastructure. Towards realizing this objective, I describe a network level risk management mechanism that prioritizes resources in a VoIP network. The prioritization scheme involves an adaptive re-computation model of risk levels using attack graphs and Bayesian inference techniques. All the above techniques collectively account for a domain-level VoIP security solution.

No description available.

Network virtualization is a technology that enables multiple virtual instances to coexist on a common physical network infrastructure. This paradigm fostered new business models, allowing infrastructure providers to lease or share their physical resources. Each virtual network is isolated and can be customized to support a new class of customers and applications. To this end, infrastructure providers need to embed virtual networks on their infrastructure. The virtual network embedding is the (NP-hard) problem of matching constrained virtual networks onto a physical network. Heuristics to solve the embedding problem have exploited several policies under different settings. For example, centralized solutions have been devised for small enterprise physical networks, while distributed solutions have been proposed over larger federated wide-area networks. In this thesis we present a policy-based architecture for the virtual network embedding problem. By policy, we mean a variant aspect of any of the three (invariant) embedding mechanisms: physical resource discovery, virtual network mapping, and allocation on the physical infrastructure. Our architecture adapts to different scenarios by instantiating appropriate policies, and has bounds on embedding efficiency, and on convergence embedding time, over a single provider, or across multiple federated providers. The performance of representative novel and existing policy configurations are compared via extensive simulations, and over a prototype implementation. We also present an object model as a foundation for a protocol specification, and we release a testbed to enable users to test their own embedding policies, and to run applications within their virtual networks. The testbed uses a Linux system architecture to reserve virtual node and link capacities.

This thesis describes a protocol for the multiple data collection system and his implementation into Network Simulator 2 environment. The system defines two communication units. CU central unit and measuring unit MU. The units operate according to the rules defined by communication protocol. The content of this work is as follows. At the beginning is described the simulation tool, namely a system NS-2 and a tool for visualization of simulation results, the NAM. This is followed by a description of the proposed protocol, his principle of functions, units description and communication messages. The method of communication between units. Mainly was described the multicast and the types of multicast ASM and SSM. Additionally, was described the principle of unicast communication. This is followed by chapter describing methods of enlargement simulator. Adding an own protocol and support of multicast communication SSM. Adding a new protocol is represented by programming a new agent, a new application and a new protocol header definition. In this chapter are also described the necessary changes in the source files that are need to the recompilation. The main objective of this thesis is own implementation of the proposed protocol. In the programming language C++ were created two agents who represent a central and a measuring unit. These agents were compiled into a simulator and by using a simple script have been tested for functionality. The simulation script define MU 200 and one unit CU. Conclusion of work is devoted to simulation the load line between the central unit and "access" node. It was examined whether the use the method of cumulative acknowledgement saves the transmission capacity of line compared to normal method acknowledgement.

The primary contributions to the area of electronic business integration, propounded by this thesis, are (in no particular order):  A novel examination of global Business-to-Business (B2B) interoperability in terms of a "multiplicity paradox" and of a "global electronic market-space" from a Complex Systems Science perspective.  A framework for an, integrated, global electronic market-space, which is based on a hierarchical, incremental, minimalist-business-pattern approach. A Web Services-SOA forms the basis of application-to-application integration within the framework. The framework is founded in a comprehensive study of existing technologies, standards and models for secure interoperability and the SOA paradigm. The Complex Systems Science concepts of "predictable structure" and "structural complexity" are used consistently throughout the progressive formulation of the framework.  A model for a global message handler (including a standards-based message-format) which obviates the common problems implicit in standard SOAP-RPC. It is formulated around the "standardized, common, abstract application interface" critical success factor, deduced from examining existing models. The model can be used in any collaboration context.  An open standards-based security model for the global message handler. Conceptually, the framework comprises the following:  An interoperable standardized message format: a standardized SOAP-envelope with standardized attachments (8-bit binary MIME-serialized XOP packages).  An interoperable standardized message-delivery infrastructure encompassing an RPC-invoked message-handler - a Web service, operating in synchronous and/or asynchronous mode, which relays attachments to service endpoints.  A business information processing infrastructure comprised of: a standardized generic minimalist-business-pattern (simple buying/selling), comprising global pre-specifications for business processes (for example, placing an order), standardized specific atomic business activities (e.g. completing an order-form), a standardized document-set (including, e.g. an order-form) based on standardized metadata (common nomenclature and common semantics used in XSD's, e.g. the order-form), the standardized corresponding choreography for atomic activities (e.g. acknowledgement of receipt of order-form) and service endpoints (based on standardized programming interfaces and virtual methods with customized implementations). / Theoretical Computing / PHD (INFORMATION SYSTEMS)