Which of the following is not a defined layer in the TCP/IP protocol model?

A.
Application layer

B.
Session layer

C.
Internet layer

D.
Network access layer

Explanation:
The TCP/IP reference model is the network model used in the current Internet architecture. It has its
origins back in the 1960’s with the grandfather of the Internet, the ARPANET. This was a research
network sponsored by the Department of Defense in the United States. The reference model was
named after two of its main protocols, TCP (Transmission Control Protocol) and IP (Internet
Protocol). They choose to build a packet-switched network based on a connectionless internet layer.
Here is a representation of it: “The TCP/IP Protocol Model is similar to the OSI model, but it defines
only the following four layers instead of seven: Application Layer. Consists of the applications and
processes that use the network. Host-to-Host Transport Layer. Provides end-to-end data delivery
service to the Application Layer. Internet Layer. Defines the IP datagram and handles the routing of
data across networks. Network Access or Link Layer. Consists of routines for accessing physical
networks and the electrical connection.” Pg 112 Krutz: The CISSP Prep Guide: Gold Edition.