This book constitutes the refereed proceedings of the 4th International IFIP-TC6 Networking Conference, NETWORKING 2005, held in Waterloo, Canada in May 2005.The 105 revised full papers and 36 posters were carefully reviewed and selected from 430 submissions. The papers are organized in topical sections on peer-to-peer networks, Internet protocols, wireless security, network security, wireless performance, network service support, network modeling and simulation, wireless LAN, optical networks, Internet performance and Web applications, ad-hoc networks, adaptive networks, radio resource management, Internet routing, queuing models, monitoring, network management, sensor networks, overlay multicast, QoS, wirless scheduling, multicast traffic management and engineering, mobility management, bandwith management, DCMA, and wireless resource management.