This document provides an overview of the TCP/IP model and its layers: 1) The application layer allows applications to access networked services and contains high-level protocols like HTTP, SMTP, and FTP. It uses both TCP and UDP depending on reliability needs. 2) The transport layer delivers application data using TCP and UDP, choosing the protocol based on reliability requirements. TCP provides error checking while UDP does not. 3) The internet layer handles data routing using IP. ICMP and IGMP are also used at this layer. 4) The network interface layer consists of device drivers and network interface cards that handle physical communication over cables or other media.