Because this edition is out of print (superseded by newer ones), you will not find it at major retail chains like Barnes & Noble. However, it is widely available in the secondary market:
The 4th edition is celebrated for making technical subjects accessible to beginners without sacrificing depth. Data Communication And Networking Forouzan 4th Edition
Finally, the book explains the protocols we use daily: Because this edition is out of print (superseded
Complex formulas are often replaced or supplemented by clear, step-by-step linguistic explanations, making it a favorite for diverse student backgrounds. Key Content and Chapter Breakdown step-by-step linguistic explanations