Server virtualization

The client/server paradigm is a common means of implementing an application over a computer network. Servers provide services, such as access to files, directories, or web pages, and clients make use of those services. The communication between the clients and servers takes the form of a network protocol. These network protocols are often rigid and inflexible due to standardization, and because they are often implemented in the operating system kernels of the clients and servers. It is difficult to add new features to existing services without having complete control of all the clients and servers in question. Virtualization is a technique that can be used to alter the properties of a network service without requiring any modifications to the clients or servers. Virtualization is typically performed on an intermediate computer that is interposed between the clients and servers, such as a programmable router. This dissertation motivates the need for virtualization and presents several different examples of successful virtualizations. These virtualizations include translation, aggregation, replication and fortification. Virtualization is demonstrated both on commodity hardware, which has the advantage of low cost, and on a specialized network processor, which offers the advantage of high performance.