The OSI (Open System Interconnection) reference model is the basis of modern data network design, but it underlines the public switched telephone network (PSTN)... » 

The OSI (Open System Interconnection) reference model is the basis of modern data network design, but it underlines the public switched telephone network (PSTN) as well. This book covers roles, functions, definitions and the fundamentals that are required of entry-level personnel. «