This paper presents congestion avoidance protocols in high speed interconnected LANs carrying both voice and data traffic. The networks are assumed to be interconnected by bridges. The protocols proposed rely on the periodic transmission of MAC control frames, called congestion notification frames, from the bridge to the source stations. Information concerning the current bridge data buffering capacity and bridge voice queueing delay is carried by these frames. On the basis of that information, the source stations may block their data input traffic to the network, thus allocating more bandwidth to voice and data traffic during periods of bridge overload. The performance of the protocols has been evaluated using simulation tools. Simulation results have shown that the proposed protocols can effectively prevent the bridge congestion, thus providing improved bridge performance for both voice and data traffic.