A broker is an N:N device that connects many (an indefinite number of) nodes to many other nodes. Its primary purpose is message routing, although it may use local store as a message pool. Messages will be routed according to a local policy, part of which will be determined by the specific brokering module used and part of which will be configured in some manner, usually by a configuration table. Where necessary, a broker will perform protocol translation in routing a message.

Where a node is behind a organizational firewall, it may be that messages to and from that node may have to be routed indirectly, through a nearby broker.

A broker has much the same functionality as an Internet router. It would be possible for brokers to exchange routing information, exactly as Internet routers do.

Throughout this document, the term broker will always mean an XLattice broker as described in this section, except where otherwise qualified.