Disclosed is a communication system—for effecting communication events between a computer system, comprising first and second computer devices, and additional endpoint(s) connected via a communication network—comprising processing units, each having access to computer storage holding executable code modules for managing a communication event configured to implement a media modality controller configured to manage media modality of an established communication event and a call controller configured to establish the communication event. An instance of the media modality controller is assigned responsive to an instruction initiated to the media controller by the call controller to convey media modality control signals of the communication event to a media agent on the first device without accessing a call agent on the second device. The initiation of the instruction by the call controller is responsive to an instruction received via the network from the call agent on the second device.