A class of Software Architecture where processing is distributed among one or more information requesters (clients) and one or more information providers (servers), as well as in the interfaces (network, protocols, middleware) between them. Client/Server Architectures include both two-tier, where clients talk directly to servers, and three-tier, where a third software component provides interface services between the clients and the servers. Three-tier architectures are further categorized by the type of middleware employed. Multi-tier is used to describe architectures with multiple layers or types of middleware. Client/Server architectures are in contrast to a mainframe architecture where the processing is self-contained.