| Summary: | Group communication concerns sending messages to receiver groups in distributed systems.
A process group comprises a set of processes and encapsulates their internal interactions, thereby
simplifying the interactions between user programs and groups of receiving processes. Although
the basic idea was proposed a few years ago, few systems or applications take advantage of it
due to a lack of a comprehensive understanding of the requirements of group communication
with respect to different classes of applications, and a lack of operating system support to meet
those requirements. This dissertation consists of two parts that address these deficiencies.
The first part provides a comprehensive understanding of process groups by examining their
potential applications, and the requirements to the system support expected by these applications.
Groups are classified based on their structure and behavior. Also, a uniform treatment
of grouping transparency is presented.
The second part of this dissertation focuses on a particularly important aspect of group
communication — group naming in an internet. For the purposes of maintaining subnet autonomy
and reducing traffic on internet links, a nested group model is proposed to allow internet
groups to contain other groups as members. By formalizing this nested group model using
a name graph, two problems in group name resolutions are identified: resolution loops and
resolution duplications. After analyzing existing methods (centralized vs. distributed dynamic
methods) and identifying their deficiencies, we propose a novel distributed static method. Instead
of detecting loops at the time of name resolution, the static method transforms the system
view of the name graph into a special structure which is updated whenever there is a change
in group membership. To guarantee correctness, the name graph transformation preserves the
property that name resolutions based on the system's view of the name graph are consistent
with respect to the users' view. Based on the assumption that name graph updates occur
much less frequently than name resolutions, static method trades a higher overhead of name
graph updates for a better performance of name resolution to gain an improved over all group
message transport performance. In this part of the dissertation, a static shadow tree algorithm
is designed and analyzed. The correctness arguments for the algorithm are provided and aspects
such as concurrency control and failure handling in name graph updates are investigated
as well. A prototype implementation of the algorithm is conducted as an existence proof to
demonstrate implementation feasibility and to test the behavior of the algorithm. === Science, Faculty of === Computer Science, Department of === Graduate
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