This book constitutes the refereed proceedings of the 17th Conference onComputer Networks, CN 2009, held in Ustro\'{n}, Poland, in June 2010. The 37 revised full papers presented were carefully reviewed andselected for inclusion in the book. The papers are organized in thefollowing groups: new technologies applied in computer networks, particularly those related to nano, molecular and quantum technology;new standard technologies related to computer network structure; thefundamentals of computer networks, their architecture and programming;articles concerning the Internet in its broad meaning; papers related todata security in distributed systems; and a group of articles describingindustrial computer networks; and papers on applications.