1. A method of operating an internal market using a software process executing on a computer, the method comprising: automatically causing a portion or all of an order to be simultaneously available for execution in both the internal market and an external market, wherein the internal and external markets each have a plurality of market participants and are each separately capable of executing trades between the market participants, and wherein the same portion or all of the order is simultaneously available to the market participants in each of the respective internal and external markets to complete a trade; and automatically controlling execution of the order such that the simultaneously available portion or all of the order is executed in at most one of the internal market and the external market; wherein the automatically controlling includes providing a mechanism for coupling the internal and external markets such that only one of the internal and external markets maintains the order for execution by a market participant at either of the internal market or the external market; and wherein when one of the internal and external markets is operating in a fast symbol mode, the other of the internal and external markets operates as a router and routes the order to the market operating in fast symbol mode without posting the order at the other of the internal and external markets, and the order can be executed at only the market operating in fast symbol mode.