Q & A on TPC/IP Layering Model,

Q: why does the book, at pp. 230, show that the TCP/IP has 5 layers, while other books (e.g., Tanenbaum's and Hunt's books) say it is 4 layers? Is it network interface layer and physical layer?, or is it host-to-network layer?

A: When I wrote Volume 1 of Internetworking with TCP/IP, I was on the IAB working with the researchers who created the protocols. I documented what they had created: a 5-layer model. Furthermore, I used the names we commonly used for the layers (e.g., network interface layer). Since then, other authors have tried to rephrase the model (e.g., at least one author omits the hardware layer). I suppose they hope such changes will increase sales of their books.