Introduction

Through class loaders, the JavaJava is a trademark of Sun Microsystems. virtual machine (JVM) supports a flexible model for loading executable code and resources at runtime [8]. Network class loading is an important form of class loading, in which class files and resources are transferred to the client JVM over a network from a server.

Because networks are generally slower in bandwidth and latency than local disks, users can experience poor startup times and significant delays when running an application loaded from a network. It is therefore desirable to optimize the transfer of classes and resources over the network to minimize these delays. Specifically, we would like to find an approach that has the following properties:

• Only files needed by the client are sent over the network.
• Files arrive when needed, in the order they are needed.
• As few bytes as possible are transferred.
• The number of requests made to the server should be minimized, in order to reduce the delay due to network latency.

In addition, we would like to make the approach practical for `real-world' deployment:

• The server implementation should scale to a large number of clients.
• The client code should be small and efficient, and should use only standard parts of the Java runtime (i.e., no native code).
• The client code should have minimal overhead.

This paper describes a technique called bundling that can approximate all of these properties under realistic network conditions.

The document is structured as follows. Section 1 reviews existing network class loading mechanisms. Section 2 describes bundling. Section 3 presents some experimental results comparing the effectiveness of bundling to existing network class loading mechanisms. Section 4 describes related work. Finally, section 5 summarizes the contributions of this paper and suggests possibilities for future work.