John Dilley

Evaluating content management techniques for Web proxy caches

The continued growth of the World-Wide Web and the emergence of new end-user technologies such as cable modems necessitate the use of proxy caches to reduce latency, network traffic and Web server loads. Current Web proxy caches utilize simple replacement policies to determine which files to retain in the cache. We utilize a trace of client requests to a busy Web proxy in an ISP environment to evaluate the performance of several existing replacement policies and of two new, parameterless replacement policies that we introduce in this paper. Finally, we introduce Virtual Caches, an approach for improving the performance of the cache for multiple metrics simultaneously.

Web server performance measurement and modeling techniques

Abstract The popularity of the Internet, and the usage of the world wide web in particular, has grown rapidly in recent years. Thousands of companies have deployed Web servers and their usage rates have increased dramatically. Our research has focused on measuring, analyzing and evaluating the performance of Internet and Intranet Web servers with a goal of creating capacity planning models. We have created layered queuing models (LQMs) and demonstrated their superiority to traditional queuing network models since they incorporate layered resource demands. Along the way we built a tool framework that enables us to collect and analyze the empirical data necessary to accomplish our goals. This paper describes the custom instrumentation we developed and deployed to collect workload metrics and model parameters from large-scale, commercial Internet and Intranet Web servers. We discuss the measurement issues pertaining to model parametrization and validation. We describe an object-oriented tool framework that significantly improves the productivity of analyzing the nearly 100 GBs of measurements collected during this workload study interval. Finally, we describe the LQM we developed to estimate client response time at a Web server. The model predicts the impact on server and client response times as a function of network topology and Web server pool size. We also use it to consider the consequences of server system configuration changes such as decreasing the HTTP object cache size.

Measurement Tools and Modeling Techniques for Evaluating Web Server Performance

The past few years have seen a rapid growth in the popularity of the Internet and the World Wide Web. Many companies are deploying Web servers and seeing their usage rates climb rapidly over time. Our research focused on analyzing and evaluating the performance of Internet and intranet Web servers with a goal of creating a Layered Queueing Model to allow capacity planning and performance prediction of next generation server designs. To achieve this we built a tool framework that enables us to collect and analyze empirical data necessary to accomplish our goals.

The effect of consistency on cache response time

This report analyzes the impact of cache consistency on the response time of client requests. The analysis divides cache responses into classes according to whether or not the cache communicated with a remote server and whether or not object data was served from the cache. Analysis of traces from deployed proxy cache servers demonstrates that a round-trip to a remote server is the dominant factor for response time. This study concludes that improving cache consistency will reduce response time and allow a cache to serve more user requests.

Object-Oriented Distributed Computing with C++ and OSF DCE

This paper suggests a method for developing object-oriented distributed applications using the C++ and DCE technologies. It presents the benefits provided by the use of object-oriented design and development techniques when writing distributed applications. It describes a model to map DCE onto C++, a structure for distributed C++ applications and it presents a set of challenges we encountered while integrating C++ with DCE, along with the solutions we chose for them. Through this approach we saw a significant decrease in application code size as well as an increase in developer productivity.

Development of distributed and client/server object-oriented applications (panel): industrial solutions

The panel will discuss emerging “industrial” solutions that help programmers to develop distributed and client/server applications based on objects supporting so-called openness and heterogeneity. The goal of the panel is to help answer the question whether there can be one single solution or whether various (integrated) approaches are needed. The panel will also compare industrial solutions such as COM, DSOM, CORBA and OODCE with results that came out of academia. Finally, a set of questions will be answered by each panelist according to the approach he will propose.

Using OMG IDL to write OODCE applications

The Object Management Groups Interface Definition Language (OMG IDL) provides a standard for specifying object-oriented interfaces for distributed applications. This paper describes a compiler that allows specification of object interfaces using OMG IDL and implementation using the Open Software Foundations Distributed Computing Environment (OSFDCE). Using this approach application developers are able to use OMG IDL to define their distributed object interfaces while using the facilities of OSF DCE for remote communications, including the DCE Security Service and DCEs object location service (CDS). This provides a very low-cost infrastructure for the development and deployment of (CORBA-based) object oriented distributed applications.

Experiences With the OSF Distributed Computing Environment

This paper describes the Open Software Foundation’s Distributed Computing Environment (OSF DCE) in the context of the ISO Reference Model of Open Distributed Processing (RMODP). It presents a critical assessment of the DCE technology, and suggests future work for both DCE and ODP. We suggest how DCE can support Open Distributed Processing, summarize the experiences we had building a DCE-based prototype, and discuss the lessons we learned from this activity. As a result of the prototype effort we built a set of DCE services to improve the usability and utility of DCE, including an object-oriented programming system, an event notification service, and a name space browser/editor for the DCE directory service. Current research efforts are underway to study fault tolerance and to provide generic data replication.