This title constitutes the refereed proceedings of the 5th IFIP TC6 International Symposium INTERWORKING 2000 on Next Generation Networks. The 33 revised papers presented are organized in topical sections on strategic views on future network architecture and services, Internet everywhere and on every network, preparing for the information society with performing networks, European perspective of next generation networks, quality of service and resource management, traffic management and control, bandwidth broker and IP net- works, and selective topics in networks.