The textbook for the course is Internetworking with TCP/IP Volume One (6th Edition) by Douglas Comer. Here are the ISBN numbers: ISBN-13: 978-0136085300 ISBN-10: 013608530X.
You will need to have the current edition of the book; the previous edition won’t do.
Unfortunately, the book is overpriced, like most academic textbooks. You can order the book from Amazon using this link. Another option is to look for a used book on bookfinders.com, where I buy most of my books.