Adding Application Servers
Outside of relatively trivial uses, it's clear that an enterprise implementing Web services will probably require additional servers. For a while, most of these servers will be what we generically call application servers (see our tutorial "Web Servers vs. Application Servers: Making the Right Choice" for more information about using Web servers and application servers).
Application servers are the dedicated aggregators of data and processing for Web servers. They will play a key role in marshalling and managing Web service components -- a job that is too complex for the current generation of Web servers. Microsoft is weaving .Net features into BizTalk and other servers, and while this doesn't rule out using other application server products, it does give Microsoft an obvious advantage.