In presenting this thesis in partial fulfillment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. AbstractReducing forwarding state overhead of multicast routing protocols is an important issue towards a scalable global multicast solution. In this paper, we propose a new approach, Dynamic Tunnel Multicast, which utilizes dynamically established tunnels on unbranched links of a multicast distribution tree to eliminate unnecessary multicast forwarding states. Analysis and simulation results show promising reduction in the state overhead of sparse mode multicast routing protocols.ii

In this paper, we address the problem of choosing a disk admission algorithm for continuous media streams where each stream may have a different bit rate, and more importantly, where the bit rate within a single stream may vary considerably. We evaluate several different Variable Bit Rate (VBR) disk admission control algorithms for continuous media. An algorithm which accepts too few streams under-utilizes the server resources, while an algorithm which accepts too many streams over-utilizes the resources resulting in inadequate service (i.e. missing or delayed data) to the clients. The evaluation process is based on a representative set of video streams encoded in MJPEG. We conclude that one particular algorithm, the VBR simulation algorithm, performs the best among realizable algorithms in terms of system utilization and delivery guarantees and performs close to an optimal algorithm,

In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the head of my department or by his or her representatives.It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. The University of British Columbia 1956 Main Mall Vancouver, Canada V6T 1Y3 Date jCf-DE-6(3/81) A b s t r a c tThis work describes the design and implementation details of a reliable group communication mechanism. The mechanism guarantees that messages will be received by all the operational members of the group or by none of them (atomicity). In addition, the sequence of messages will be the same at each of the recipients (order). The message ordering property can be used to simplify distributed database systems and distributed processing algorithms. The proposed mechanism continues to operate despite process, host and communication link failures (survivability). Survivability is essential in fault-tolerant applications. Elapsed time (mill! seconds) for ugsend and ogsend.Sending process ln the same host as the primary manager.Elapsed time (mllll seconds) for ugsend and ogsend.Sending process in the same host as a secondary manager.

roup communication is an operating-system-level abstraction that offers convenience and clarity to the programmer. Currently, only a few To design a general, essarily one-to-one.) Each group is viewed as a single logical entity, without exposing its internal structure and interactions to users. operating systems support this abstraction. coherent, and integrated Generally, objects are grouped for (1) However, a lack of understanding of group abstracting the common characteristics of communication requirements with respect group communication group members and the services they proto different classes of applications may be vide, (2) encapsulating the internal state equally responsible for the abstraction's

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