The Instant Messaging multiplexor component connects multiple instant messenger connections into one TCP (Transmission Control Protocol) connection, which is then connected to the Instant Messaging server. The multiplexor reads data from Instant Messenger and writes it to the server. Conversely, when the server sends data to Instant Messenger, the multiplexor reads the data and writes it to the appropriate connection. The multiplexor does not perform any end user authentication or parse the client-server protocol (IM protocol). Each multiplexor is connected to one and only one Instant Messaging server.
Although you can configure Instant Messaging without a multiplexor, production deployments should be configured to use the multiplexor. You can install multiple multiplexors based on your deployment requirements. For more information, Chapter 21, Developing an Instant Messaging Architecture.