Reference document

Message Proxying Services
The Message Proxying Services are services that act as an intermediary for other services, hiding their actual location and implementation from the service consumers. The proxy services can communicate on a behalf of the underlying service. They offer a capability to expose a virtual endpoint of the underlying service. They supports the loose coupling and service abstraction principles of the SOA design. The Message Proxying Services tend to sit at the boundaries of organisations, either internal boundaries (between sites, before WAN links) or external boundaries (such as the Internet). They provide a number of benefits over the use of directly communicating through a router. A number of security features may be activated, such as content checking, authentication and authorisation, auditing and anonymity (as the identity of the client machine can be hidden). The Message Proxy Services can communicate with Message Caching Services to avoid having to make calls across sub-optimal WAN links, and can use other techniques (such as compression) to improve performance.
Message-Oriented Middleware Services