One of the challenges for future internetworks is that the design should deal with ever-increasing diversity of speeds, access protocols, and resource allocations. In this paper, various performance issues for interconnecting (a) local area networks with high-speed LANs and (b) high-speed LANs with wide-area networks are discussed. Throughput, delay, and buffering requirements at the local and extended-area access controllers are analyzed. For simulation model, two architectural candidates, (a) FDDI and (b) token ring backbones interconnected with Ethemets, are considered. The simulation results include throughput versus offered load, load versus delay, and mean queueing delay at the bridges.