A systems approach to synchronization and naming in a distributed computing environment

This thesis describes the development of a distributed computer architecture that supports the interconnection of loosely-coupled computing resources (sites) by heterogeneous communication networks. The internetwork system, named the intelligent message transport system, provides for reliable delivery of intersite messages even though the interconnecting networks may use a probabilistic ( best-effort ) delivery scheme. Processors are interfaced to each other by a network gateway processor. The gateway processors are autonomous network controllers that provide a simple and consistent site interface to the internetwork system. The gateway processors also provide for high level functions at the Transport Layer of the system rather than burdening the user with networking details at the Application Layer. These high-level functions include the synchronization of concurrent updates to replicated data objects, and the management of the system-wide name space for shared data

MENU: multicast emulation using netlets and unicast

High-end networking applications such as Internet TV and software distribution have generated a demand for multicast protocols as an integral part of the network. This will allow such applications to support data dissemination to large groups of users in a scalable and reliable manner. Existing IP multicast protocols lack these features and also require state storage in the core of the network which is costly to implement. In this paper, we present a new multicast protocol referred to as MENU. It realises a scalable and a reliable multicast protocol model by pushing the tree building complexity to the edges of the network, thereby eliminating processing and state storage in the core of the network. The MENU protocol builds multicast support in the network using mobile agent based active network services, Netlets, and unicast addresses. The multicast delivery tree in MENU is a two level hierarchical structure where users are partitioned into client communities based on geographical proximity. Each client community in the network is treated as a single virtual destination for traffic from the server. Netlet based services referred to as hot spot delegates (HSDs) are deployed by servers at "hot spots" close to each client community. They function as virtual traffic destinations for the traffic from the server and also act as virtual source nodes for all users in the community. The source node feeds data to these distributed HSDs which in turn forward data to all downstream users through a locally constructed traffic delivery tree. It is shown through simulations that the resulting system provides an efficient means to incrementally build a source customisable secured multicast protocol which is both scalable and reliable. Furthermore, results show that MENU employs minimal processing and reduced state information in networks when compared to existing IP multicast protocols

Multicast communications in distributed systems

PhD ThesisOne of the numerous results of recent developments in communication networks and distributed systems has been an increased interest in the study of applications and protocolsfor communications between multiple, as opposed to single, entities such as processes and computers. For example, in replicated file storage, a process attempts to store a file on several file servers, rather than one. MUltiple entity communications, which allow one-to-many and many-to-one communications, are known as multicast communications. This thesis examines some of the ways in which the architectures of computer networks and distributed systems can affect the design and development of multicast communication applications and protocols.To assist in this examination, the thesis presents three contributions. First, a set of classification schemes are developed for use in the description and analysis of various multicast communication strategies. Second, a general set of multicast communication primitives are presented, unrelated to any specific network or distributed system, yet efficiently implementable on a variety of networks. Third, the primitives are used to obtain experimental results for a study ofintranetwork and internetwork multicast communications.Postgraduate Scholarship, The Natural Sciences and Engineering Research Council of Canada: Overseas Research Student Award: the Committee of Vice-Chancellors and Principals of the Universities of the Uni ted Kingdom

SDN management layer: design requirements and future direction

Computer networks are becoming more and more complex and difficult to manage. The research community has been expending a lot of efforts to come up with a general management paradigm that is able to hide the details of the physical infrastructure and enable flexible network management. Software Defined Networking (SDN) is such a paradigm that simplifies network management and enables network innovations. In this survey paper, by reviewing existing SDN management layers (platforms), we identify the general common management architecture for SDN networks, and further identify the design requirements of the management layer that is at the core of the architecture. We also point out open issues and weaknesses of existing SDN management layers. We conclude with a promising future direction for improving the SDN management layer.This work is supported in part by the National Science Foundation (NSF grant CNS-0963974)

Parallel Programming Using Shared Objects and Broadcasting

The two major design approaches taken to build distributed and parallel computer systems, multiprocessing and multicomputing, are discussed. A model that combines the best properties of both multiprocessor and multicomputer systems, easy-to-build hardware, and a conceptually simple programming model is presented. Using this model, a programmer defines and invokes operations on shared objects, the runtime system handles reads and writes on these objects, and the reliable broadcast layer implements indivisible updates to objects using the sequencing protocol. The resulting system is easy to program, easy to build, and has acceptable performance on problems with a moderate grain size in which reads are much more common than writes. Orca, a procedural language whose sequential constructs are roughly similar to languages like C or Modula 2 but which also supports parallel processes and shared objects and has been used to develop applications for the prototype system, is described

Identifying mechanisms (naming) in distributed systems: goals, implications and overall influence on performance

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