Publisher Summary This chapter focuses on switches that reside solely in the data plane and are controlled by external components using Internet Protocol (IP)-based protocols. The term “switch” has been used to refer to a node that runs routing and signaling code to control the behavior of hardware, which is responsible for switching data from one port to another based on some form of label. These Label Switching Routers (LSRs) are actually composites with a presence in the routing, control, and data planes. Version three of the General Switch Management Protocol (GSMP) is specifically designed for the management of label switches. Switches act as the servers and listen on the reserved port 6068. GSMP operates in an IP network using the Transmission Control Protocol (TCP). A controller opens a TCP connection to a switch and exchanges Adjacency messages to negotiate the GSMP version and operational parameters to use. Switches may also issue unsolicited status messages to the controllers to report on asynchronous events in the data plane. The Forwarding and Control Element Separation (ForCES) Working Group in the Internet Engineering Task Force(IETF) is chartered to investigate the separation of forwarding and control components of IP routers. Another important protocol discussed is LMP-WDM that is an extension to the Link Management Protocol (LMP) for use within Wave Division Multiplexing (WDM) switches.