Our publisher: Pearson
Our publisher's page for the rental version of the 8th edition of our book is here; Our publisher's page for the e-version of the 8th edition (which is not yet available as of mid-July 2021) of our book is here; the Amazon page for the 7th edition is here and we'll soon post an Amazon page for the 8th edition.
If you're an instructor, you can request a desk copy of the text from your Pearson representative here. Instructors can also request a copy of the solutions to the end of the chapter problems, Wireshark labs, and programming assignments from their rep. Let the authors know if you have problems obtaining these materials. We'd also recommend that you check out the "Instructor Resources" page on this website.