Welcome to the proceedings of Networking 2005, the fourth conference in what is now an annual series. This was the ?rst time the conference was held outside Europe, and the University of Waterloo is proud to be the institutional host. Networking is the ?agship conference of Technical Committee 6, Com- nication Systems, of the International Federation for Information Processing (IFIP TC 6). The conference is sponsored by four of the eleven working groups in TC 6: Network and Internetwork Architectures (WG 6.2), Performance of Communication Systems (WG 6.3), Wireless Communications (WG 6.8), and Photonic Networking (WG 6.10). Previously unpublished technical papers were solicited and peer-reviewed in three tracks: Networking Technologies, Services and Protocols, Performance of ComputerandCommunicationNetworks, andMobileandWirelessCommuni- tion Systems. The ?nal program re?ected this organization as much as possible. In addition, four proposals for high-quality workshops were accepted, there were three keynote speeches and three panel sessions, and a program of tutorials was put in place. The Organizing Committee endeavored to complement the exciting technical program with an attractive social program. TheTechnicalProgramCommittee, leadbyRaoufBoutaba, accepted105full papersand36posterpapersfrom430submissions, originatingin26countrieson four continents. This placed a large load on the TPC and track chairs, the 199 membersoftheTPC, andmorethan600reviewerswhowroteover1800reviews.