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