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)

published_or_final_version / abstract / Electrical and Electronic Engineering / Doctoral / Doctor of Philosophy

This study examines the role of traditional computing performance measures when used in a client/server system (C/SS) environment. It also evaluates the effectiveness of traditional computing measures of mainframe systems for use in C/SS. The underlying problem was the lack of knowledge about how performance measures are aligned with key business goals and strategies. This research study has identified and evaluated client/server performance measurements' importance in establishing an effective performance evaluation system. More specifically, this research enables an organization to do the following: (1) compare the relative states of development or importance of performance measures, (2) identify performance measures with the highest priority for future development, (3) contrast the views of different organizations regarding the current or desired states of development or relative importance of these performance measures.

Leung Wai Tak. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2002. / Includes bibliographical references (leaves 58-60). / Abstracts in English and Chinese. / Acknowledgement --- p.I / Abstract --- p.II / 摘要 --- p.III / Chapter Chapter 1 --- Introduction --- p.1 / Chapter Chapter 2 --- Related Works --- p.5 / Chapter 2.1 --- Previous Works --- p.5 / Chapter 2.2 --- Contributions of this Study --- p.7 / Chapter Chapter 3 --- Architecture --- p.9 / Chapter 3.1 --- Data Placement Policy --- p.10 / Chapter 3.2 --- Retrieval and Transmission Scheduling --- p.13 / Chapter 3.3 --- Fault Tolerance --- p.20 / Chapter Chapter 4 --- Performance Modeling --- p.22 / Chapter 4.1 --- Storage Requirement --- p.22 / Chapter 4.2 --- Network Bandwidth Requirement --- p.23 / Chapter 4.3 --- Buffer Requirement --- p.24 / Chapter 4.4 --- System Response Time --- p.27 / Chapter Chapter 5 --- System Reliability --- p.29 / Chapter 5.1 --- System Failure Model --- p.29 / Chapter 5.2 --- Minimum System Repair Capability --- p.32 / Chapter 5.3 --- Redundancy Configuration --- p.35 / Chapter Chapter 6 --- System Dimensioning --- p.37 / Chapter 6.1 --- Storage Capacity --- p.38 / Chapter 6.2 --- Network Capacity --- p.38 / Chapter 6.3 --- Disk Access Bandwidth --- p.39 / Chapter 6.4 --- Buffer Requirement --- p.41 / Chapter 6.5 --- System Response Time --- p.43 / Chapter Chapter 7 --- Multiple Parity Groups --- p.45 / Chapter 7.1 --- System Failure Model --- p.47 / Chapter 7.2 --- Buffer Requirement --- p.47 / Chapter 7.3 --- System Response Time --- p.49 / Chapter 7.4 --- Redundancy Configuration --- p.49 / Chapter 7.5 --- Scalability --- p.51 / Chapter Chapter 8 --- Conclusions and Future Works --- p.53 / Appendix --- p.55 / Chapter A. --- Derivation of the Artificial Admission Delay --- p.55 / Chapter B. --- Derivation of the Receiver Buffer Requirement --- p.56 / Bibliography --- p.58

Ip Tak Shun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 95-101). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iv / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.1 / Chapter 1.1.1 --- Media Streaming --- p.1 / Chapter 1.1.2 --- Incentive Mechanism --- p.2 / Chapter 1.2 --- Cooperative and Incentive-based Proxy-and-Client Caching --- p.4 / Chapter 1.2.1 --- Cooperative Proxy-and-Client Caching --- p.4 / Chapter 1.2.2 --- Revenue-Rewarding Mechanism --- p.5 / Chapter 1.3 --- Thesis Contribution --- p.6 / Chapter 1.4 --- Thesis Organization --- p.7 / Chapter 2 --- Related Work --- p.9 / Chapter 2.1 --- Media Streaming --- p.9 / Chapter 2.2 --- Incentive Mechanism --- p.11 / Chapter 2.3 --- Resource Pricing --- p.14 / Chapter 3 --- Cooperative Proxy-and-Client Caching --- p.16 / Chapter 3.1 --- Overview of the COPACC System --- p.16 / Chapter 3.2 --- Optimal Cache Allocation (CAP) --- p.21 / Chapter 3.2.1 --- Single Proxy with Client Caching --- p.21 / Chapter 3.2.2 --- Multiple Proxies with Client Caching --- p.24 / Chapter 3.2.3 --- Cost Function with Suffix Multicast --- p.26 / Chapter 3.3 --- Cooperative Proxy-Client Caching Protocol --- p.28 / Chapter 3.3.1 --- Cache Allocation and Organization --- p.29 / Chapter 3.3.2 --- Cache Lookup and Retrieval --- p.30 / Chapter 3.3.3 --- Client Access and Integrity Verification --- p.30 / Chapter 3.4 --- Performance Evaluation --- p.33 / Chapter 3.4.1 --- Effectiveness of Cooperative Proxy and Client Caching --- p.34 / Chapter 3.4.2 --- Robustness --- p.37 / Chapter 3.4.3 --- Scalability and Control Overhead --- p.38 / Chapter 3.4.4 --- Sensitivity to Network Topologies --- p.40 / Chapter 4 --- Revenue-Rewarding Mechanism --- p.43 / Chapter 4.1 --- System Model --- p.44 / Chapter 4.1.1 --- System Overview --- p.44 / Chapter 4.1.2 --- System Formulation --- p.47 / Chapter 4.2 --- Resource Allocation Game --- p.50 / Chapter 4.2.1 --- Non-Cooperative Game --- p.50 / Chapter 4.2.2 --- Profit Maximizing Game --- p.52 / Chapter 4.2.3 --- Utility Maximizing Game --- p.61 / Chapter 4.3 --- Performance Evaluation --- p.74 / Chapter 4.3.1 --- Convergence --- p.76 / Chapter 4.3.2 --- Participation Incentive --- p.77 / Chapter 4.3.3 --- Cost effectiveness --- p.85 / Chapter 5 --- Conclusion --- p.87 / Chapter A --- NP-Hardness of the CAP problem --- p.90 / Chapter B --- Optimality of the Greedy Algorithm --- p.92 / Bibliography --- p.95

Leung Siu Kuen. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 67-68). / Abstracts in English and Chinese. / Abstract --- p.i / Acknowledgement --- p.iii / Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Motivation --- p.1 / Chapter 1.1.1 --- A Story --- p.1 / Chapter 1.2 --- Overview --- p.2 / Chapter 1.2.1 --- Introduction of SQL Injection --- p.4 / Chapter 1.3 --- The importance of SQL Injection --- p.6 / Chapter 1.4 --- Thesis organization --- p.8 / Chapter 2 --- Background --- p.10 / Chapter 2.1 --- Flow of web applications using DBMS --- p.10 / Chapter 2.2 --- Structure of DBMS --- p.12 / Chapter 2.2.1 --- Tables --- p.12 / Chapter 2.2.2 --- Columns --- p.12 / Chapter 2.2.3 --- Rows --- p.12 / Chapter 2.3 --- SQL Syntax --- p.13 / Chapter 2.3.1 --- SELECT --- p.13 / Chapter 2.3.2 --- AND/OR --- p.14 / Chapter 2.3.3 --- INSERT --- p.15 / Chapter 2.3.4 --- UPDATE --- p.16 / Chapter 2.3.5 --- DELETE --- p.17 / Chapter 2.3.6 --- UNION --- p.18 / Chapter 3 --- Details of SQL Injection --- p.20 / Chapter 3.1 --- Basic SELECT Injection --- p.20 / Chapter 3.2 --- Advanced SELECT Injection --- p.23 / Chapter 3.2.1 --- Single Line Comment (--) --- p.23 / Chapter 3.2.2 --- Guessing the number of columns in a table --- p.23 / Chapter 3.2.3 --- Guessing the column name of a table (Easy one) --- p.26 / Chapter 3.2.4 --- Guessing the column name of a table (Difficult one) . --- p.27 / Chapter 3.3 --- UPDATE Injection --- p.29 / Chapter 3.4 --- Other Attacks --- p.30 / Chapter 4 --- Current Defenses --- p.32 / Chapter 4.1 --- Causes of SQL Injection attacks --- p.32 / Chapter 4.2 --- Defense Methods --- p.33 / Chapter 4.2.1 --- Defensive Programming --- p.34 / Chapter 4.2.2 --- hiding the error messages --- p.35 / Chapter 4.2.3 --- Filtering out the dangerous characters --- p.35 / Chapter 4.2.4 --- Using pre-complied SQL statements --- p.36 / Chapter 4.2.5 --- Checking for tautologies in SQL statements --- p.37 / Chapter 4.2.6 --- Instruction set randomization --- p.38 / Chapter 4.2.7 --- Building the query model --- p.40 / Chapter 5 --- Proposed Solution --- p.43 / Chapter 5.1 --- Introduction --- p.43 / Chapter 5.2 --- Natures of SQL Injection --- p.43 / Chapter 5.3 --- Our proposed system --- p.44 / Chapter 5.3.1 --- Features of the system --- p.44 / Chapter 5.3.2 --- Stage 1 - Checking with current signatures --- p.45 / Chapter 5.3.3 --- Stage 2 - SQL Server Query --- p.45 / Chapter 5.3.4 --- Stage 3 - Error Triggering --- p.46 / Chapter 5.3.5 --- Stage 4 - Alarm --- p.50 / Chapter 5.3.6 --- Stage 5 - Learning --- p.50 / Chapter 5.4 --- Examples --- p.51 / Chapter 5.4.1 --- Defensing BASIC SELECT Injection --- p.52 / Chapter 5.4.2 --- Defensing Advanced SELECT Injection --- p.52 / Chapter 5.4.3 --- Defensing UPDATE Injection --- p.57 / Chapter 5.5 --- Comparison --- p.59 / Chapter 6 --- Conclusion --- p.62 / Chapter A --- Commonly used table and column names --- p.64 / Chapter A.1 --- Commonly used table names for system management --- p.64 / Chapter A.2 --- Commonly used column names for password storage --- p.65 / Chapter A.3 --- Commonly used column names for username storage --- p.66 / Bibliography --- p.67

In recent years, multi-tier architectures have become the standard computing environment for web- and enterprise applications. The application server tier is often the heart of the system embedding the business logic. Adaptability, in particular the capability to adjust to the load submitted to the system and to handle the failure of individual components, are of outmost importance in order to provide 7/24 access and high performance. Replication is a common means to achieve these reliability and scalability requirements. With replication, the application server tier consists of several server replicas. Thus, if one replica fails, others can take over. Furthermore, the load can be distributed across the available replicas. Although many replication solutions have been proposed so far, most of them have been either developed for fault-tolerance or for scalability. Furthermore, only few have considered that the application server tier is only one tier in a multi-tier architecture, that this tier maintains state, and that execution in this environment can follow complex patterns. Thus, existing solutions often do not provide correctness beyond some basic application scenarios. / In this thesis we tackle the issue of replication of the application server tier from ground off and develop a unified solution that provides both fault-tolerance and scalability. We first describe a set of execution patterns that describe how requests are typically executed in multi-tier architectures. They consider the flow of execution across client tier, application server tier, and database tier. In particular, the execution patterns describe how requests are associated with transactions, the fundamental execution units at application server and database tiers. Having these execution patterns in mind, we provide a formal definition of what it means to provide a correct execution across all tiers, even in case failures occur and the application server tier is replicated. Informally, a replicated system is correct if it behaves exactly as a non-replicated that never fails. From there, we propose a set of replication algorithms for fault-tolerance that provide correctness for the execution patterns that we have identified The main principle is to let a primary AS replica to execute all client requests, and to propagate any state changes performed by a transaction to backup replicas at transaction commit time. The challenges occur as requests can be associated in different ways with transactions. Then, we extend our fault-tolerance solution and develop a unified solution that provides both fault-tolerance and load-balancing. In this extended solution, each application server replica is able to execute client requests as a primary and at the same time serves as backup for other replicas. The framework provides a transparent, truly distributed and lightweight load distribution mechanism which takes advantage of the fault-tolerance infrastructure. Our replication tool is implemented as a plug-in of JBoss application server and the performance is carefully evaluated, comparing with JBoss' own replication solutions. The evaluation shows that our protocols have very good performance and compare favorably with existing solutions.

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Thesis (M. App. Sc.)--Carleton University, 2001. / Includes bibliographical references (p. 126-130). Also available in electronic format on the Internet.