SCO Embedded Configuration Toolkit Whitepaper
Chapter 2, Embedded application environments

Client controllers

Client controllers

Client controllers are typically located between the clients and the server, and have the task of regulating traffic over the network and other functions related to supporting client applications. They can do this by acting as a gateway between sub-networks connecting locally grouped client machines. They can also provide data management facilities and act as repositories, and can provide CPU processing resources for distributed embedded applications. This prevents the network from becoming overloaded at times of high system load, at the same time protecting the server from being overloaded by client requests. Typically, a client controller will also take over the server's diskless client boot responsibilities. 

Figure 2-3 Client controllers as gateways

A client controller is a modified disk based client which can provide client and some server functionality. The images for client controllers are generated and loaded in the same way as for disk based clients. However, it should be noted that the configuration of client controllers will always be more complex than that of disk based clients due to the added server functionality.