A method for enabling traffic to be carried between devices which may use different communications protocols employs a multimedia service provide, which provides an interface between two devices or between a device and a multimedia network. The service provider enables conversion between the communications protocols used by the two devices by comparing the protocols used by each device and, preferably, carrying out a conversion which minimises the amount of traffic conversion required. If two devices are interfaced to an intermediate network via respective service providers, the service providers preferably negotiate before communication between the devices begins to ensure, if possible, that traffic conversion is only performed by one of the service providers. Each device is connected to the service provider at a network access server of a type matched to the device type and traffic conversion is carried out as required using an Asynchronous Transfer Mode Virtual Channel switch controlled by a multimedia server.