Home > Articles > Cisco Certification > CCNA Routing and Switching > The TCP/IP and OSI Networking Models

The TCP/IP and OSI Networking Models


  1. "Do I Know This Already?" Quiz
  2. Foundation Topics
  3. Exam Preparation Tasks

Chapter Description

This chapter explains the terminology and concepts behind the world’s most popular networking model, TCP/IP, including several example protocols: HTTP, TCP, IP, and Ethernet. It also explains the terminology behind the OSI networking model in comparison to TCP/IP.

Exam Preparation Tasks

Review All the Key Topics

Review the most important topics from inside the chapter, noted with the key topics icon in the outer margin of the page. Table 2-6 lists a reference of these key topics and the page number on which each is found.


Table 2-6 Key Topics for Chapter 2

Key Topic Elements


Page Number

Table 2-3

Provides definitions of same-layer and adjacent-layer interaction


Figure 2-8

Shows the general concept of IP routing


Figure 2-9

Depicts the data-link services provided to IP for the purpose of delivering IP packets from host to host


Figure 2-12

Shows the meaning of the terms segment, packet, and frame


Figure 2-13

Compares the OSI and TCP/IP network models



Lists the benefits of using a layered networking model


Complete the Tables and Lists from Memory

Print a copy of Appendix L, “Memory Tables,” (found on the DVD) or at least the section for this chapter, and complete the tables and lists from memory. Appendix M, “Memory Tables Answer Key,” includes completed tables and lists to check your work.

Definitions of Key Terms

Define the following key terms from this chapter, and check your answers in the Glossary:

adjacent-layer interaction, decapsulation, encapsulation, frame, networking model, packet, protocol data unit (PDU), same-layer interaction, segment

OSI Reference

You should memorize the names of the layers of the OSI model. Table 2-7 summarizes the OSI functions at each layer, along with some sample protocols at each layer.

Table 2-7 OSI Functional Summary


Functional Description

Application (7)

Interfaces between network and application software. Also includes authentication services.

Presentation (6)

Defines the format and organization of data. Includes encryption.

Session (5)

Establishes and maintains end-to-end bidirectional flows between endpoints. Includes managing transaction flows.

Transport (4)

Provides a variety of services between two host computers, including connection establishment and termination, flow control, error recovery, and segmentation of large data blocks into smaller parts for transmission.

Network (3)

Logical addressing, routing, and path determination.

Data link (2)

Formats data into frames appropriate for transmission onto some physical medium. Defines rules for when the medium can be used. Defines means by which to recognize transmission errors.

Physical (1)

Defines the electrical, optical, cabling, connectors, and procedural details required for transmitting bits, represented as some form of energy passing over a physical medium.