Voice over IP and over Wireless/Wired Local Area Networks (VoWLAN).
Modern networks built for both data and telecommunication are increasingly being configured for mainly IP traffic rather than the older switched telephony networks. The internet has been built around best effort quality of service which is sometimes usable but unreliable for multi media data such as voice and video. For example, most data transfers use the TCP/IP protocol which given reliable data transfer but with no promises about when the data will be delivered. In fact TCP/IP may hold back latter packets of data if an earlier packet was lost for some reason. Hence most multi-media applications use unicast or multicast UDP packets and mange the application requirements in the application layer rather than for example in the transport layer.
The design of protocols and their configuration for networks carrying multi media and other types of traffic is an open topic. New protocols need to be tested in many different scenarios to ensure they behave as designed and to measure how much better or worse the network's performance is. Protocols exist at all the levels in the network architecture from the application layer through to the physical layer. For many multi media formats, the way in which they are packaged as packets and transmitted can have a very large effect on the efficiency and behaviour of the network. All these and other aspects are good research topics.