|  | 2.3 | Comparison of the OSI Model and the TCP/IP Model
| 2.3.3 | TCP/IP protocol graph
The diagram shown in the Figure is called a protocol graph. It illustrates some of the common protocols that are specified by the TCP/IP reference model. At the application layer, you will see different network tasks you may not recognize, but as a user of the Internet, probably use every day. You will examine all of these during the course of the curriculum. These applications include the following: FTP - File Transport Protocol HTTP - Hypertext Transfer Protocol SMTP - Simple Mail Transport protocol DNS - Domain Name Service TFTP - Trivial File Transport Protocol The TCP/IP model emphasizes maximum flexibility, at the application layer, for developers of software. The transport layer involves two protocols - transmission control protocol (TCP) and user datagram protocol (UDP). You will examine these, in detail, later in the CCNA curriculum. The lowest layer, the network layer, refers to the particular LAN or WAN technology that is being used. In the TCP/IP model, regardless of which application requests network services, and regardless of which transport protocol is used, there is only one network protocol - internet protocol, or IP. This is a deliberate design decision. IP serves as a universal protocol that allows any computer, anywhere, to communicate at any time.
| Web Links
| Introduction to the Internet Protocols