I recently followed a Computer Networking course, and the teachers actually went though pains to ensure those with older editions could follow the assigned exercises.
From what I could tell, the differences between the 6th, 5th and 4th editions were not discernible in the text, only the exercises had changed positions and had subtle variations in the numbers and wordings. That was my first experience with the textbook industry. The book, Computer Networking: A Top-Down Approach by Kurose and Ross was very good, but the obvious abuse of their monopoly by forcing students to buy the newer editions gave me my first look into how the textbook industry operates.
Still, I have great respect for my University (Utrecht University in the Netherlands) for (until now) either using syllabi that can be freely downloaded or cheaply bought for a hardcopy or accommodating students with older editions of textbooks.
From what I could tell, the differences between the 6th, 5th and 4th editions were not discernible in the text, only the exercises had changed positions and had subtle variations in the numbers and wordings. That was my first experience with the textbook industry. The book, Computer Networking: A Top-Down Approach by Kurose and Ross was very good, but the obvious abuse of their monopoly by forcing students to buy the newer editions gave me my first look into how the textbook industry operates.
Still, I have great respect for my University (Utrecht University in the Netherlands) for (until now) either using syllabi that can be freely downloaded or cheaply bought for a hardcopy or accommodating students with older editions of textbooks.
EDIT: Oh, and I recently found this link: http://www.textbooknova.com/.
It's probably not legal, but free textbooks!