11.0.1 Chapter Introduction

In this chapter, we will examine the process for connecting and configuring computers, switches, and routers into an Ethernet LAN.

We will introduce the basic configuration procedures for Cisco network devices. These procedures require the use of the Cisco Internetwork Operating System (IOS) and the related configuration files for intermediary devices.

An understanding of the configuration process using the IOS is essential for network administrators and network technicians. The labs will familiarize you with common practices used to configure and monitor Cisco devices.

Learning Objectives

Upon completion of this chapter, you will be able to:

• Define the role of the Internetwork Operating System (IOS).
• Define the purpose of a configuration file.
• Identify several classes of devices that have the IOS embedded.
• Identify the factors contributing to the set of IOS commands available to a device.
• Identify the IOS modes of operation.
• Identify the basic IOS commands.
• Compare and contrast the basic show commands.

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10.0 Chapter Introduction

10.0.1 Chapter Introduction

Before using an IP phone, accessing instant messaging, or conducting any number of other interactions over a data network, we must connect end devices and intermediary devices via cable or wireless connections to form a functioning network. It is this network that will support our communication in the human network.

Up to this point in the course, we have considered the services that a data network can provide to the human network, examined the features of each layer of the OSI model and the operations of TCP/IP protocols, and looked in detail at Ethernet, a universal LAN technology. The next step is to learn how to assemble these elements together in a functioning network.

In this chapter, we will examine various media and the distinct roles they play with the devices that they connect. You will identify the cables needed to make successful LAN and WAN connections and learn how to use device management connections.

The selection of devices and the design of a network addressing scheme will be presented and then applied in the networking labs.

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9.0 Chapter Introduction

9.0.1 Chapter Introduction

Up to this point in the course, each chapter focused on the different functions of each layer of the OSI and TCP/IP protocol models as well as how protocols are used to support network communication. Several key protocols – TCP, UDP, and IP – are continually referenced in these discussions because they provide the foundation for how the smallest of networks to the largest, the Internet, work today. These protocols comprise the TCP/IP protocol stack and since the Internet was built using these protocols, Ethernet is now the predominant LAN technology in the world.

Internet Engineering Task Force (IETF) maintains the functional protocols and services for the TCP/IP protocol suite in the upper layers. However, the functional protocols and services at the OSI Data Link layer and Physical layer are described by various engineering organizations (IEEE, ANSI, ITU) or by private companies (proprietary protocols). Since Ethernet is comprised of standards at these lower layers, generalizing, it may best be understood in reference to the OSI model. The OSI model separates the Data Link layer functionalities of addressing, framing and accessing the media from the Physical layer standards of the media. Ethernet standards define both the Layer 2 protocols and the Layer 1 technologies. Although Ethernet specifications support different media, bandwidths, and other Layer 1 and 2 variations, the basic frame format and address scheme is the same for all varieties of Ethernet.

This chapter examines the characteristics and operation of Ethernet as it has evolved from a shared media, contention-based data communications technology to today’s high bandwidth, full-duplex technology.

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8.0 Chapter Introduction

8.0.1 Chapter Introduction

Upper OSI layer protocols prepare data from the human network for transmission to its destination. The Physical layer controls how data is transmitted on the communication media.

The role of the OSI Physical layer is to encode the binary digits that represent Data Link layer frames into signals and to transmit and receive these signals across the physical media – copper wires, optical fiber, and wireless – that connect network devices.

This chapter introduces the general functions of the Physical layer as well as the standards and protocols that manage the transmission of data across local media.

In this chapter, you will learn to:

• Explain the role of Physical layer protocols and services in supporting communication across data networks.
• Describe the purpose of Physical layer signaling and encoding as they are used in networks.
• Describe the role of signals used to represent bits as a frame is transported across the local media.
• Identify the basic characteristics of copper, fiber, and wireless network media.
• Describe common uses of copper, fiber, and wireless network media.

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7.0 Chapter Introduction

7.0.1 Chapter Introduction

To support our communication, the OSI model divides the functions of a data network into layers.

To recap:

• The Application layer provides the interface to the user.
• The Transport layer is responsible for dividing and managing communications between the processes running in the two end systems.
• The Network layer protocols organize our communication data so that it can travel across internetworks from the originating host to a destination host.

For Network layer packets to be transported from source host to destination host, they must traverse different physical networks. These physical networks can consist of different types of physical media such as copper wires, microwaves, optical fibers, and satellite links. Network layer packets do not have a way to directly access these different media.

It is the role of the OSI Data Link layer to prepare Network layer packets for transmission and to control access to the physical media.

This chapter introduces the general functions of the Data Link layer and the protocols associated with it.

Learning Objectives

Upon completion of this chapter, you will be able to:

• Explain the role of Data Link layer protocols in data transmission.
• Describe how the Data Link layer prepares data for transmission on network media.
• Describe the different types of media access control methods.
• Identify several common logical network topologies and describe how the logical topology determines the media access control method for that network.
• Explain the purpose of encapsulating packets into frames to facilitate media access.
• Describe the Layer 2 frame structure and identify generic fields.
• Explain the role of key frame header and trailer fields, including addressing, QoS, type of protocol, and Frame Check Sequence.

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6.0 Chapter Introduction

Addressing is a key function of Network layer protocols that enables data communication between hosts on the same network or on different networks. Internet Protocol version 4 (IPv4) provides hierarchical addressing for packets that carry our data.

Designing, implementing and managing an effective IPv4 addressing plan ensures that our networks can operate effectively and efficiently.

This chapter examines in detail the structure of IPv4 addresses and their application to the construction and testing of IP networks and subnetworks.

In this chapter, you will learn to:

• Explain the structure IP addressing and demonstrate the ability to convert between 8-bit binary and decimal numbers.
• Given an IPv4 address, classify by type and describe how it is used in the network.
• Explain how addresses are assigned to networks by ISPs and within networks by administrators.
• Determine the network portion of the host address and explain the role of the subnet mask in dividing networks.
• Given IPv4 addressing information and design criteria, calculate the appropriate addressing components.
• Use common testing utilities to verify and test network connectivity and operational status of the IP protocol stack on a host.

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5.0 Chapter Introduction

We have seen how network applications and services on one end device can communicate with applications and services running on another end device.

Next, as shown in the figure, we will consider how this data is communicated across the network – from the originating end device (or host) to the destination host – in an efficient way.

The protocols of the OSI model Network layer specify addressing and processes that enable Transport layer data to be packaged and transported. The Network layer encapsulation allows its contents to be passed to the destination within a network or on another network with minimum overhead.

This chapter focuses on the role of the Network layer – examining how it divides networks into groups of hosts to manage the flow of data packets within a network. We also consider how communication between networks is facilitated. This communication between networks is called routing.

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4.0 Chapter Introduction

Data networks and the Internet support the human network by supplying seamless, reliable communication between people – both locally and around the globe. On a single device, people can use multiple services such as e-mail, the web, and instant messaging to send messages or retrieve information. Applications such as e-mail clients, web browsers, and instant messaging clients allow people to use computers and networks to send messages and find information.

Data from each of these applications is packaged, transported, and delivered to the appropriate server daemon or application on the destination device. The processes described in the OSI Transport layer accept data from the Application layer and prepare it for addressing at the Network layer. The Transport layer is responsible for the overall end-to-end transfer of application data.

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3.0 Chapter Introduction

3.0.1 Chapter Introduction

Most of us experience the Internet through the World Wide Web, e-mail services, and file-sharing programs. These applications, and many others, provide the human interface to the underlying network, enabling us to send and receive information with relative ease. Typically the applications that we use are intuitive, meaning we can access and use them without knowing how they work. However, for network professionals, it is important to know how an application is able to format, transmit and interpret messages that are sent and received across the network.

Visualizing the mechanisms that enable communication across the network is made easier if we use the layered framework of the Open System Interconnection (OSI) model. In this chapter, we will focus on the role of one layer, the Application layer and its components: applications, services, and protocols. We will explore how these three elements make the robust communication across the information network possible.

In this chapter, you will learn to:

• Describe how the functions of the three upper OSI model layers provide network services to end user applications.
• Describe how the TCP/IP Application Layer protocols provide the services specified by the upper layers of the OSI model.
• Define how people use the Application Layer to communicate across the information network.
• Describe the function of well-known TCP/IP applications, such as the World Wide Web and email, and their related services (HTTP, DNS, SMB, DHCP, SMTP/POP, and Telnet).
• Describe file-sharing processes that use peer-to-peer applications and the Gnutella protocol.
• Explain how protocols ensure services running on one kind of device can send to and receive data from many different network devices.
• Use network analysis tools to examine and explain how common user applications work.

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2.0 Chapter Introduction

2.0.1 Chapter Introduction

More and more, it is networks that connect us. People communicate online from everywhere. Efficient, dependable technology enables networks to be available whenever and wherever we need them. As our human network continues to expand, the platform that connects and supports it must also grow.

Rather than developing unique and separate systems for the delivery of each new service, the network industry as a whole has developed the means to both analyze the existing platform and enhance it incrementally. This ensures that existing communications are maintained while new services are introduced that are both cost effective and technologically sound.

In this course, we focus on these aspects of the information network:

• Devices that make up the network
• Media that connect the devices
• Messages that are carried across the network
• Rules and processes that govern network communications
• Tools and commands for constructing and maintaining networks

Central to the study of networks is the use of generally-accepted models that describe network functions. These models provide a framework for understanding current networks and for facilitating the development of new technologies to support future communications needs.

Within this course, we use these models, as well as tools designed to analyze and simulate network functionality. Two of the tools that will enable you to build and interact with simulated networks are Packet Tracer 4.1 software and Wireshark network protocol analyzer.

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