and its brokerless ;-)
Quote from NetTecture:
It is a message bus / pping system. The idea core being that you can not do everything in one process / machine, so passing messages between a communication / dispather system (that talks upstream to the exchange) and machines running the processing loops (possibly 1 core per algo, hot - i.e. in a spinning loop) is needed, and that must be FAST.
ZeroMQ - MQ standing for Message Queue - is a middleware for passing messages.