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Stratatm IT FUNDAMENTALS

Lesson 3: Networking and Internetworking

Lesson Objectives In this lesson, you will examine various types of transmission media, networking hardware, Ethernet

and wireless networking standards and technologies, Internet protocols and Web browser

configurations. On completion, you will be familiar with:

Peer-to-peer and client/server networks.

LANs and WANs.

IP addressing.

Transmission media.

Function and characteristics of network hardware.

Protocols in the TCP/IP suite.

Data encapsulation.

Wireless networking technologies and standards.

Web browser configurations.

Exam Objectives

1.1 Identify basic IT vocabulary.

Lesson 3 Networking and Internetworking

62 8520-1 v1.00 © CCI Learning Solutions Inc.

What Constitutes a Network? A network is a group of two or more computers connected in such a way that they can communicate, share

resources and exchange data with one another. In a typical networked environment, computers are connected

to a network server, which acts as a central location for programs and data to which all users connected to the

network have access. Networks allow users to transfer data from one computer to another, share resources

such as printers, share storage locations for files, use e-mail and access the Internet.

Several types of networks are in common use today. Ethernet, token ring and ATM are a few of the network

types you may have heard of. Each type of network is based upon and controlled by a networking standard.

Later in this lesson, we will explore the characteristics of Ethernet networks and investigate portions of the

Ethernet standard. For now, it is enough to know that Ethernet is a family of networking technologies.

Client/Server vs. Peer-to-Peer Models The two networking models in common use today are the client/server model and the peer-to-peer model.

Many corporate networks are structured using the client/server model. These networks are also called

server-based networks. In a server-based network, individual computers and devices are called nodes. A node

is any addressable device on a network that can be managed or controlled. Nodes interact with one another

through a central server through which they are all connected.

In a typical server-based network, the individual PCs are client systems. These are the systems used to browse

the Internet, check e-mail or print to a network printer. The services requested by the client systems (e.g.,

Internet access, e-mail or access to network resources) are provided by the server. The server is more

powerful than the clients connected to it.

Server-based networks are generally more secure than peer-to-peer networks because a central server

controls access to all the network resources. To access the network from a client system, users must log on to

the network by providing a user name and password. Server-based networks are also more expensive to build

and maintain than peer-to-peer networks because they require server versions of a network operating system,

and may require a full-time network administrator to keep everything up and running.

Objective

1.1

Networking and Internetworking Lesson 3


A peer-to-peer network is one in which all the participating computers are more or less equal, and there is no

central server. In a peer-to-peer network, each computer connected to the network is called a host. Hosts in a

peer-to-peer network can share files, an Internet connection, a printer, a scanner or other peripheral devices. A

Windows 7 HomeGroup (or in previous versions of the Windows operating system, a Microsoft Windows

Workgroup) is an example of a peer-to-peer network.

The terms host and node are often inaccurately used interchangeably in both networking models. Although a

node is any network addressable device that can be managed, a host must have the capacity to provide a

resource (such as a file) or a service to other systems on the network. In networking terms, a host is always a

computer.

Local Area Networks (LANs) and Wide Area Networks (WANs) LANs and WANs form the basis for networking and internetworking. Internetworking is networking over the

Internet.

LAN A local area network (LAN) is a group of computers that are connected within a relatively small geographic

area, such as a home, office or small group of buildings. A LAN can consist of as few as two computers, or any

number of systems up to hundreds of computers and servers. LANs are commonly used for communication

between users within an office.

It is often useful to connect one LAN to another LAN. For example, if different divisions of a company within a

large business each have their own LAN, connecting the LANs allows the divisions to share data and

resources.

WAN A wide area network (WAN) consists of two or more LANs that cover a wide geographic area (for example, a

city, state or country). Consider a large business with offices in several locations worldwide. Each office has its

own LAN which it can use to share resources and data locally. However, if the company needs to share

resources with other offices, the LANs can be connected using communication lines provided by a public carrier

(such as the phone company or an Internet service provider). When two or more LANs are connected using a

public network, a WAN is created. The largest WAN on the planet is the Internet.

The main features that distinguish LANs from WANs are:

A LAN is confined to local cabling that you install in your home, or that an IT department has routed

through the office. In a LAN, the organization owns all the components. In a WAN, an organization usually

leases some of the necessary components that are required to transmit data (such as high-speed

telecommunications lines).

LANs are also usually much faster than WANs. For example, most Ethernet cards transfer data at 10 or

100 Mbps, and in installations using Gigabit Ethernet, data moves at 1 Gbps. A typical WAN connection

might run at 1.5 Mbps.



Network Operating Systems A network operating system manages resources on a network and offers services to one or more clients. It can

manage multiple users on a network; provide services such as Internet access, e-mail and security; and

provide access to resources. A network operating system is required on a server-based network; it must run on

the server and a compatible client version of the operating system must run on the clients. Microsoft Windows

and UNIX/Linux are two very popular network operating systems.

Major network operating systems can interoperate with one another, making it easier for businesses to create a

network even if not all their server or client systems are running the same operating system. Usually, software

must be installed on the server and client to ensure interoperability.

Microsoft Windows Microsoft Windows first released the New Technology (NT) family of network operating systems in the early

1990s. The Windows 2000 Server family (released in 2000) introduced new features and services. This family

of server operating systems includes Windows 2000, Windows Server 2003 and Windows Server 2008.

All operating systems in the Windows 2000 Server family use a protocol called Transmission Control

Protocol/Internet Protocol (TCP/IP) as the default network protocol. A protocol is a set of specific rules that

control how communication takes place between various systems or devices.

UNIX/Linux UNIX was first developed in 1969. The essential part of the operating system that provides basic services is

called the kernel. Today, many versions of UNIX have evolved from the original kernel, and there is no single

version. These different versions known as "flavors," include Linux, Sun Solaris and BSD.

For many years, most servers on the Internet ran one form of UNIX or another, and UNIX is still in wide use

today. UNIX also uses TCP/IP as its default networking protocol.

Linux, one of the many flavors of UNIX, is an open-source operating system, which means the source code

must be freely distributed and anyone is allowed to make copies for their own use. If changes are made to the

kernel, those changes must be made freely available. Linux can operate as a client or a server and supports

many common Internet protocols, including TCP/IP.

Networking Protocols — a short history You have already seen references to the networking protocol named TCP/IP. A networking protocol is a set of

rules that computers, servers and other network devices use to communicate with each other. Various

protocols exist for LANs and WANs, and proprietary protocols are specific to given operating systems.

For example, the AppleTalk protocol is used on Macintosh computers, and is also supported by Windows NT

and Windows 2000. The Mac OS X (10.2 and later) operating systems, however, support TCP/IP. Novell

NetWare (another network operating system) used a proprietary protocol named IPX/SPX (Internetwork Packet

Exchange/Sequence Packet Exchange) in its early versions. Later versions of NetWare also support TCP/IP.

TCP/IP is a non-proprietary networking protocol supported by most major operating systems. TCP/IP is also the

de facto networking protocol of the Internet.

Introducing TCP/IP TCP/IP is the current de facto standard for both local and wide area networking. In addition to being used on

private networks, TCP/IP is required for Internet access. Currently the Internet fully supports TCP/IP version 4.

However, version 6 (known as IPv6) is gaining support.

TCP/IP is a collection or suite of protocols that provide services for many things users do on the Web — from

downloading e-mail to following hyperlinks and downloading data from an FTP site. Right now, we will briefly

examine Internet Protocol (IP), which is responsible for addressing.



For one computer to communicate with another over a TCP/IP network, it must know the other computer's

Internet address. Each computer on a TCP/IP network (or on the Internet) has an Internet address that uniquely

identifies it and distinguishes it from all other computers on the Internet. This Internet address is called an IP

address.

Internet Protocol Version 4 (IPv4) The two versions of Internet Protocol are version 4 (IPv4) and version 6 (IPv6). These versions differ in the

format of IP addresses. (They differ in other ways too, but those are beyond the scope of this course.) The

most widely used version of IP today is IPv4.

An IPv4 address is 32 bits long and is written as a series of numbers divided into four segments, with each

segment separated by a dot. This format is often referred to as a "dotted quad." Each segment is a number

between 0 and 255. A sample IPv4 address is shown below:

192.168.1.103

Roughly 256 x 256 x 256 x 256 different IP addresses are possible — approximately four billion. However, the

current supply of IP addresses will eventually be depleted because IP address demand continues to increase.

Network and host portions IP addresses include a network portion and a host portion. In a 32-bit address, a certain number of bits (starting

from the left-most bit) identify the network where the host is located. These bits are the network identifier or

network ID; that is, they form the network portion of the address (the network portion always precedes the host

portion). The remaining bits are used to identify the specific host on the network. For example, in the IP

address 192.168.1.102, the network portion is 192.168.1, and the host portion is 102.

Subnet masks A subnet mask is a 32-bit number (similar to an IP address), that distinguishes the network and host portions of

an IP address. It also helps determine if a destination system is local (on the same LAN) or remote. If an

incorrect subnet mask is specified in a system's network configuration settings, the system will not be able to

communicate with other systems on the network.

Internet Protocol Version 6 (IPv6) A revised addressing scheme in IPv6 was developed to keep up with the demand for IP addresses. Instead of

using 32 bits (as an IPv4 address does), an IPv6 address uses 128 bits. The IPv6 address space supports 2128

addresses (more than 340 trillion). The format for this 128-bit address uses hexadecimal numbers instead of

decimal numbers, and separates each hexadecimal integer of the address using colons Following is an

example of an IPv6 address:

2E22:4F00:000E:00D0:A267:97FF:FE6B:FE34

Most major operating systems now include support for IPv6, and IPv6 is expected to gradually replace IPv4,

with the two coexisting for a number of years during a transition period. Most new networking equipment also

supports IPv6, but old networking equipment probably does not.

Standard Configuration Information For a system to participate in a network and/or to be able to access the Internet, it requires basic networking

configuration setttings. These include:

An IP adress, the 32-bit address that identifies a computer as a unique entity on a network. You can

configure this address manually, but it is much more common to lease an address automatically through a

network service called Dynamic Host Configuration Protocol (DHCP). DHCP will be discussed later in this

lesson.

A subnet mask, the 32-bit number that is used to distinguish the network and host portions of an IP

address.



The IP address of the default gateway. The default gateway is a networking device that provides access

outside the local LAN. The default gateway is usually a router (routers are discussed later in this lesson). If

you need Internet access, you must specify the address of the default gateway.

IP addresses are not permanent. A computer participating on a network usually leases an IP address for a

specified period of time. When a lease is expired, another computer may lease that IP address, or the original

computer may renew the lease.

Even on a computer where a network address is entered manually (this is called a static IP address because it

does not change), once a computer is removed from the network, the IP address it once used may be assigned

to another system, and the computer that was removed from the network is free to join another network and

obtain an IP address specific to that new network.

Exercise 3-1 Identifying Your IP address

In this exercise, you will use a Windows utility and a TCP/IP utility to examine your IP address

1. Click the Start button, then click Control Panel to open the Control Panel window.

2. In the Control Panel window, click Network and Internet, then click Network and Sharing Center to open

the Network and Sharing Center window.

3. In the View your active networks section of the Network and Sharing Center window, click Local Area

Connection to open the Local Area Connection Status window.

4. In the Local Area Connection Status window, click the Details button to open the Network Connection

Details window.



5. Write your system's IP address and subnet mask in the space provided:

_________________________________________________

6. Close all open windows.

You can use the command prompt window to access TCP/IP utilities.

7. Click the Start button, type: cmd in the Search programs and files text box, then press to open a

command prompt window, such as the one shown:

8. In the command prompt window, type: ipconfig, then press to display information about your

current IP configuration, including the IP address, subnet mask and default gateway settings.

You can release your IP address.

9. Type: ipconfig /release and press . Your system releases its IP address.

IP Address Subnet Mask



Many systems use a TCP/IP service called Automatic Private IP Addressing (APIPA) when they require an

IP address and cannot obtain one from a DHCP server.

10. Type: ipconfig and press once more.

Notice that your IP address is now listed as an Autoconfiguration IPv4 address, similar to the one shown.

This is an example of an APIPA address.

You can also renew your IP address. When you use the renew option with the ipconfig command, your system

contacts the DHCP server to obtain its configuration settings.

11. Type: ipconfig /renew and press .

Notice that your system renews its IP address.

12. Close the command prompt window.

In this exercise, you used a Windows utility and a TCP/IP utility to view your IP address.



Networking Models Several models exist for networking and for networking over the Internet. Although it is not necessary to

understand all of their intricacies, a basic familiarity with these models will help you understand how networking

hardware and protocols work. The two models we will investigate in this course are the Open Systems

Interconnection reference model (OSI/RM) and the TCP/IP four-layer model.

The OSI Reference Model The Open Systems Interconnection reference model (OSI/RM) is a seven-layer networking function

model. Adherence to the model ensures that systems from various vendors will be able to communicate

with one another. As you will see shortly, the model also describes the sequence of data encapsulation.

The model was defined by the International Organization for Standardization (ISO).

The seven layers of the OSI/RM are briefly described in the following table.

Layer # Layer Name Comments

7 Application The user interface resides at this layer. Web browsers and e-mail clients work at

this layer of the model. This is the only layer a user actually sees; the functions

of the other layers are transparent to the user.

6 Presentation User input and other information is transformed at this layer into a standardized

format recognized by all operating systems.

5 Session Connections between systems that are communicating with each other are set

up and torn down at this layer.

4 Transport Mechanisms that ensure data is accurately and completely sent and received

between communicating systems operate here.

3 Network Data is organized into discrete units called packets at this layer, and in addition

to the original data, each packet includes addressing information that is required

to deliver the packet to its intended destination.

2 Data Link At this layer, packets are divided into discrete units called frames before being

sent across the transmission medium. The transmission medium is the physical

wire that connects the devices on the network. This layer also controls access to

the transmission medium.

1 Physical At this layer, frames are transmitted across the transmission medium in a

bitstream, that is, as a series of 1s and 0s.

Data Encapsulation Networking models remind us of the processes that must take place for systems to communicate with one

another. For example, consider two computer systems on a network. One belongs to Ed and one belongs to

Ron. If Ed's computer needs to send data to Ron's computer, Ed's computer must first "package" that data to

prepare it for transport across the network. This process is called data encapsulation.

To properly encapsulate the data to be sent across the network to Ron's computer, Ed's computer will pass the

data down through each of the seven layers of the OSI/RM. Each layer adds its own packaging information and

passes it to the next layer below. Once the data reaches Layer 2, it is prepared to be sent across the physical

transmission medium used on the network (e.g., copper wire or fiber-optic cable).

Ed's encapsulated data is sent across the transmission medium and received at Ron's computer. Ron's

computer then takes the data off the transmission medium and passes it up through the seven layers of the

OSI/RM. As the data is passed up through the OSI/RM on Ron's computer, the data is de-encapsulated until it

reaches Layer 7, where it is once again in a usable form.

MMM The OSI In-Depth



The following figure illustrates this process:

At various stages during the encapsulation process, the data being encapsulated is referred to by different

names, as illustrated in the following figure.

As you learn more about protocols and networking technologies, you may see data at various stages of

encapsulation referred to by these names: data, segment, packet and frame. In some literature, you may find

data at all stages of encapsulation referred to simply as "packets."

Layer 7

Layer 6

Layer 5

Layer 4

Layer 3

Layer 2

Layer 1

Data

Segment

Packet

Frame

Bits – 1s and 0s

Layer 7

Layer 6

Layer 5

Layer 4

Layer 3

Layer 2

Layer 1

Layer 7

Layer 6

Layer 5

Layer 4

Layer 3

Layer 2

Layer 1

Sending system

Receiving system

Transmission Medium

MMM The Data Encapsul-

ation Process



The TCP/IP Four-Layer Model The TCP/IP architecture uses a four-layer model, and each layer coincides with layers of the OSI/RM, as

shown in the following illustration. Each layer in the architecture has its own specific functions.

OSI/RM TCP/IP Protocols

Layer 7

Application

Application Layer

HTTP, FTP, SSL, POP3, SMTP, IMAP4, DNS,

DHCP

Layer 6

Presentation

Layer 5

Session

Layer 4

Transport

Transport Layer

TCP, UDP

Layer 3

Network

Internet Layer

IP

Layer 2

Data Link

Network Interface/Access Layer

Ethernet, Wireless LAN Layer 1

Physical

Various protocols are mapped to specific layers. You will investigate these protocols later in this lesson.

Application layer The application layer of the TCP/IP architecture corresponds to the application, presentation and session layers

of the OSI/RM. The TCP/IP application layer interacts with the transport-layer protocols to send or receive data.

Transport layer The transport layer of the TCP/IP architecture corresponds to the transport layer of the OSI/RM. This layer

accepts application-layer data and divides the data into segments. Each segment is passed to the Internet

layer.

Internet layer (or network layer) The Internet layer of the TCP/IP architecture corresponds to the network layer of the OSI model. A segment

received from the transport layer is encapsulated in an IP packet.

Network interface layer (or access layer) The access layer of the TCP/IP architecture corresponds to the physical and data link layers of the OSI model.

This layer accepts higher-layer packets, creates frames and transmits them in bitstreams over the attached

network.

Networking Devices Now that you have an idea of the seven layers of the OSI model, you can understand how networking devices

function. Each device is designed to operate at a specific layer (or layers) of the model, and thus, is designed to

work with data at various stages of encapsulation.

Network Interface Card (NIC) Each node in a network contains a network interface card (NIC), often called a network adapter card. The NIC

is the interface between the computer and the network (that is, it is the physical connection between the

computer and the network cabling).



Many modern computers include NIC hardware integrated into the motherboard, but it is quite common to find

NICs that reside in a motherboard PCI expansion slot too. NICs also come with USB and FireWire interfaces as

well. Laptops often use PCMCIA NICs. NICs provide a connection port for network cabling, and also come in

wireless varieties.

A NIC communicates with the computer through a NIC device driver,

which is a computer program that allows the operating system to

interact with a hardware device. A network cable connects the NIC to

the network. This physical interface to the network is defined at

physical layer (Layer 1) of the OSI model.

MAC addresses Every NIC has a unique physical address that identifies it on a network. This address is called the Media

Access Control (or MAC) address. Even though this address is also called the physical address or the

hardware address, the address itself is defined at the data link layer (Layer 2) of the OSI model.

MAC addresses are unique addresses burned into a NIC by the manufacturer. They are designed to allow

systems to provide unique addressing information on a network. A MAC address uses 12 hexadecimal digits to

form a 48-bit address (6 bytes). The address is divided into two halves. The first 24 bits identify the vendor that

created the NIC. This portion is known as the Organizationally Unique Identifier (OUI), or the vendor code.

Popular NIC vendors include 3COM, Cisco, Dell, Intel and so on.

The remaining 24 bits constitute the serial number of the NIC. The serial number, called the interface serial

number, is unique to the vendor, and no two MAC addresses are identical.

MAC addresses are displayed in varying forms. For example, they may be shown in:

six groups of two hexadecimal digits separated by hyphens 00-14-1C-40-B0-80

six groups of two hexadecimal digits separated by colons 00:14:1C:40:B0:80

three groups of four hexadecimal digits separated by dots 0014.1C40.B080

MAC addresses are used for addressing only by devices within the same LAN, not outside the LAN. For data to

be sent outside the LAN, an IP address is used. The network portion of an IP address indicates on which

network a particular host resides.

Exercise 3-2 Viewing the MAC address on your system

In this exercise, you will use a Windows utility and a TCP/IP utility to view the MAC address on your system.

1. Click the Start button, then click Control Panel to open the Control Panel window.

2. In the Control Panel window, click Network and Internet, then click Network and Sharing Center to open

the Network and Sharing Center window.

3. In the View your active networks section of the Network and Sharing Center window, click Local Area

Connection to open the Local Area Connection Status window.

4. In the Local Area Connection Status window, click the Details button to open the Network Connection

Details window.



5. Write your system's MAC address in the space provided:

_________________________________________________

6. Close all open windows.

7. Click the Start button, type: cmd in the Search programs and files text box, then press to open a

command prompt window.

8. In the command prompt window, type: ipconfig /all, then press to display information about

your current network settings, including the MAC address of your NIC.

Notice that window displays a wealth of information about your network settings, including the MAC address

and probably the vendor of your NIC. You may need to scroll up through the results in the command prompt

window to view the MAC address.

9. Close the command prompt window.

In this exercise, you used a Windows utility and a TCP/IP utility to view the MAC address on your system.

MAC Address Vendor

MAC Address

Vendor



Networking Concepts Before exploring other types of networking devices, you should first understand some basic networking

concepts:

Network segments Large networks are frequently broken into manageable pieces called segments. A

segment is a portion of a network on either side of a router or bridge (these devices will

be discussed shortly). Within a given network segment, devices can send data to each

other using a MAC address. Breaking networks into segments keeps the network

functioning efficiently. In an Ethernet network, a network segment is called a collision

domain.

Collision domain An area in a network where a group of network devices compete for access to the

transmission medium. In traditional Ethernet networking, only one device can transmit

at any time. When two devices attempt to transmit at the same time, their transmitted

frames collide and are destroyed. The more collisions there are, the less efficient the

network is.

Access methods Rules by which networking devices abide to avoid a high number of collisions. Some

technologies use collision avoidance, whereas others use collision detection. The

access method is determined at Layer 2 of the OSI model.

Broadcast A transmission from one network node that is intended to reach all other nodes on the

local network segment. Broadcasts are used whenever a device needs to send out

information, but does not know which device to address it to. Broadcasts are important

to the function of a network, but must be handled carefully because they generate a lot

of traffic.

Broadcast domain A logical area in a network in which any connected device can transmit to any other

device in the domain without having to go through a routing device. Broadcast traffic is

limited to the confines of a broadcast domain. If a network has been broken into

segments, each separate segment is a broadcast domain.

Simplex

communication

A mode of communication in which the data can flow in one direction only (similar to a

public address system).

Half-duplex

communication

A mode of communication in which the data can flow in two directions, but in only one

direction at a time, similar to a walkie-talkie.

Full-duplex

communication

A mode of communication in which data can flow in two directions simultaneously,

similar to a telephone conversation.

Authentication The process of verifying the identity of a user who logs on to a system, or the integrity

of transmitted data. Users logging on to a network authenticate themselves by

providing a username and password.

Hubs A hub connects computers in a network so they can exchange information. A hub has several ports and each

node attached to the network plugs into a port on the hub using a network cable. Hubs operate at the physical

layer (Layer 1) of the OSI model.

Technically, a hub connects multiple devices into the same collision domain and allows frame collision. All

hosts connected to the hub must share the bandwidth and only one host can transmit at a time. Each host is

responsible for detecting collisions and retransmitting frames if some were lost in a collision. This traditional

setup is called shared Ethernet.

In a shared Ethernet network, transmission is half-duplex. That is, data can be transmitted in only one direction

at a time. Hubs have been widely replaced by switches in modern networks.



Bridges Bridges are networking devices that determine whether a frame belongs on a local network segment, or on

some other network segment. Bridges make this determination by examining the destination hardware address

(MAC address) encapsulated in each frame. Bridges operate at the data link layer (Layer 2) of the OSI model.

Bridges are commonly used to divide a network into separate segments, thereby reducing traffic by creating

smaller collision domains. Bridges have also been largely replaced by switches in modern networks.

Routers Routers are similar to bridges, but they operate at the network layer (Layer 3) of the OSI model. Instead of

using MAC addresses, routers use the network portion of the IP address to determine where data should be

forwarded or "routed."

Routers can be used to connect separate network segments on a LAN, or to connect separate LANs, thereby

forming a WAN. Routers identify the destination machine's network address, then determine the most efficient

route for sending the data to the destination. Because routers direct data packets between different networks or

network segments, they do not forward broadcast traffic.

An organization typically has one router that connects to a public carrier's lines to access the Internet. This type

of router is called an access router because it provides access to the Internet. The access router provides the

path outside the LAN. Because it acts as a gateway to the Internet, this router is referred to on the network as

the "default gateway."

Switches A switch is a networking device that can connect either individual systems or multiple networks. Switches

include multiple Ethernet ports, with different sized switches offering a varying number of ports. A switch directs

the flow of data directly from one node to another. In contrast to routers, switches forward broadcast traffic. The

following figure shows a 24-port switch.

A switch is much faster than a hub or a bridge because it cross-connects all hosts connected to it, thereby

providing a separate connection between any two nodes that need to communicate. For any given connection,

the collision domain consists of only the two nodes that are communicating. For this reason, the switch can give

each sender/receiver pair the line's entire bandwidth; this is in contrast to communication in a hub, in which all

connected devices must share the bandwidth.

Switches also provide full-duplex communication. A switch can handle multiple simultaneous communications

between the computers attached to it, whereas a hub can handle only one at a time. Ethernet networks that use

switches instead of hubs are called Full Ethernet networks.

By definition, a switch operates at the data link layer (Layer 2) of the OSI model. However, there are several

types of switches that operate at different layers.

A Layer 2 switch (also called a LAN switch) forwards traffic based on MAC addresses.

A Layer 3 switch (also called a routing switch) forwards traffic based on network address information as

well as based on MAC addresses.



Firewall A firewall is a security barrier that controls the flow of information between the Internet and a private network. It

can be a dedicated computer system, or it can be implemented on a networking device such as a router. In a

home or small office networking environment where a broadband router is used, a firewall is usually built in to

the broadband router.

Firewalls can also be created by software. Staring with Windows XP, the Windows firewall (which was also

included with Windows 2000) was turned on by default. Aside from operating systems firewalls, you can use

third-party software firewall products, including ZoneAlarm, Komodo Firewall and PC Tools Firewall Plus. No

two software firewall products should be used at the same time, however, as they tend to interfere with one

another.

A firewall protects your network from malicious activity coming from outside your network, and provides a

"door" through which people can communicate between a secured network and the open, unsecured Internet.

A network firewall is most commonly placed between a corporate LAN and the Internet. When a company

connects its LAN to the Internet through a firewall, no computer on the LAN is actually connected directly to the

Internet – all requests for information, and all transmissions coming back to the corporate network, must pass

through the firewall, which inspects packets before allowing them through.

Modems At one time, the term modem referred specifically to a device that translated digital data into analog signals and

then back again. Today, the term is widely used and refers to any device that adapts a computer to a phone

line or cable TV network.

Modem history At one time, the most common way to access the Internet was to use a dial-up connection. Such connections

are very slow and rarely used anymore. However, some users still use dial-up because it is the least expensive

method of obtaining Internet access.

Although the public switched telephone network (PSTN) is almost entirely digital in nature, the connections to

users’ homes and offices is usually analog. Dial-up connections use a modem, or modulator/demodulator,

which enables computers to transmit data over standard analog telephone lines. A modem converts

(modulates) digital data from a computer into an analog signal which is transmitted over the phone line to

another modem. The receiving modem converts the analog signal back into a digital signal (demodulates) and

transmits it to the receiving computer. This type of modem is called a traditional or analog modem.



When you use a dial-up connection, your computer uses the modem to dial a phone number that connects your

computer with your Internet Service Provider (ISP), which in turn connects your computer to the Internet. When

you finish your online session, you disconnect from the ISP. The speed of the connection is determined

primarily by the speed of the two modems involved in the session; however, the maximum possible speed for

data transfer over a standard analog telephone line is 56 Kbps.

Modern connections and modems Analog modems and phone lines are impractical for transferring the large audio and video files that make the

Internet a rich medium. As a result, telephone companies, cable TV services and other suppliers offer high-

speed direct connections to the Internet. These connections provide continuous access to the Internet through

permanent network connections, eliminating the need to establish a connection each time you want to use the

Internet. Direct connections are available via a number of connection methods, including (but not limited to)

cable and digital subscriber lines (DSL).

A digital subscriber line (DSL) is a high-speed all-digital connection

offered by the phone company. The digital service is configured on the

phone lines and a DSL modem is used to connect to the digital

telephone circuit using a telephone cable. The modem also includes an

Ethernet port. You attach the modem to your computer using an

Ethernet cable by plugging one end of the cable into the Ethernet port

on the modem and the other end of the cable into the Ethernet port on

your NIC. (Some DSL modems also include a USB port for connecting

to the computer.) The picture on the right shows a typical DSL modem.

A cable TV system uses coaxial (“coax”) cables to transmit signals. You

can connect to the Internet through your cable TV system using a cable modem. A cable modem connects to

the cable TV system's Internet server, which is in turn connected to the Internet backbone. A cable modem

attaches to the cable service via a coaxial cable (the same type of cable you attach to your television set). The

cable modem includes a jack for the coax cable and it also includes an Ethernet port. You attach the modem to

your computer using an Ethernet cable by plugging one end of the cable into the Ethernet port on the modem

and the other end of the cable into the Ethernet port on your NIC.

The picture to the left shows a cable modem. Although you cannot see the

ports, the modem is connected to the cable service through a standard cable

TV coaxial cable.

As you can see, DSL and cable modems are not really modems at all because

they do not modulate digital signals into analog ones, nor do they demodulate

analog signals back into digital ones. These devices are more accurately

described as terminal adapters because they provide a connection point

between a computer system and a public carrier's service.

Because these components are used as a gateway to connect to the Internet,

they are often referred to as residential gateways when they are used in a

home setting.

Broadband Routers The term broadband is commonly used to describe any high-speed data transmission that provides services at

1.54 Mpbs or higher. DSL and cable modems can technically be considered routers because they connect a

computer or network to the Internet. Remember, a router creates a connection between a local network and an

outside network.

In many cases, DSL modems and cable modems manage connection sharing, allowing several users to share

one Internet connection. These modems have more than one Ethernet port (or support wireless connections),

allowing multiple users to plug in an Ethernet cable and connect to the Internet.



However, the term broadband router generally applies to any device that combines the features of a switch, a

firewall and a DHCP server. If your DSL or cable modem includes only one Ethernet port (allowing just one

connection), you can purchase a separate broadband router and use it on your network to allow multiple users

to share one Internet connection.

A broadband router, such as the one shown in the following figure, includes several Ethernet ports. One port is

designated as the WAN port (or Internet port). You connect the router to your modem by attaching one end of

an Ethernet cable to the router's WAN port, and the other end of the cable to the Ethernet port on your DSL or

cable modem. This connection allows the router access to your

Internet service.

The other Ethernet ports on the broadband router are LAN

ports. When you want to connect other computers to the

network, you attach them (via Ethernet cable) to the LAN ports.

Transmission Media To transmit data across a network, a medium must exist. Often the transmission medium is a type of wire or

cabling, although free space can also serve as a transmission medium in wireless networking. Wireless

networking will be discussed later in this lesson.

Wiring is the part of a network that is most vulnerable to interference and other performance problems which

can be caused by improper handling or installation practices.

The types of transmission media we will discuss in this section include fiber-optic and twisted-pair cable.

Fiber-Optic Cable Fiber-optic cables consist of two small glass (or plastic) strands: one that sends signals and one that receives

signals. These strands are called the core. Each core is surrounded by glass cladding. Each core and cladding

element is wrapped with a plastic casing. Laser transmitters send light pulses through the core and optical

receivers receive them.

Fiber-optic cable can accommodate data transmissions much faster than copper wire cable. Because they

send data as pulses of light over threads of glass, the transmissions can travel for miles without any signal

degradation. No electrical signals are carried over the fiber-optic line, so the lines are free of electromagnetic

interference as well.

The two major types of fiber-optic cable are:

Single-mode fiber

(SMF)

Supports a single transmission path. The cable's core diameter is 8 to 10 microns. It

permits signal transmission at extremely high bandwidth and allows very long

transmission distances (up to 70 km, or 43 miles). Single-mode fiber is often used for

intercity telephone trunks and video applications.

Multi-mode fiber

(MMF)

Uses a large number of frequencies (or modes). The cable's core is larger than that of

single-mode fiber, usually 50 microns to 100 microns, and it allows for the use of

inexpensive light sources. It is used for short to medium distances (less than 200 m, or

656 feet). Multi-mode fiber is the type usually specified for LANs and WANs.

Fiber-optic cable is also used as the backbone for networks. It had been predicted by experts in the optical

networking industry that fiber-to-the-desktop (that is, a fiber-optic connection at the NIC) would become

common. However, advances in copper cabling and the expensive nature of fiber-optic cable have at least

delayed this occurrence.



Twisted-Pair Cable Twisted-pair cable is perhaps the most widely used cabling system in Ethernet networks. It comes in two basic

types – unshielded twisted-pair (UTP) and shielded twisted-pair (STP). Both types of cable are composed of

four pairs of copper wires. The wires in each pair are twisted around each other, and the pairs are twisted

together and bundled inside a covering. This figure shows a section of

UTP cable with the covering pulled back and the wire pairs separated

for easy viewing.

UTP cable is available in specific categories. Each category has a

specific use and a specific number of twists per foot, and is capable of

a specific bandwidth. The more twists there are per foot of cable, the

less that interference affects the data traveling on the cable.

The most commonly used grades today are Categories or "Cat" 5, 5e,

6 and 6a. A Cat7 cable exists, but it is still an emerging standard. The following table describes the most

popular grades of twisted-pair, and lists both the data transfer rate (in Mbps) and the MHz value of the wire.

Standard Ethernet requires a cable that supports at least 10 MHz; Fast Ethernet requires a cable that can

support 100 MHz.

Cable Grade Bandwidth Uses

Cat 5 100 Mbps

Rated at 100 MHz

Can be used for both standard Ethernet (10 Mbps) and Fast

Ethernet (100 Mbps).

Cat 5e 1 Gbps

Rated at up to 100 MHz

Can be used for Fast Ethernet and Gigabit Ethernet and other

high-speed networks. Has largely replaced Cat 5.

Cat 6 2.5 Gbps


Supports Gigabit Ethernet. Unlike other categories of twisted

pair, Cat 6 is not particularly durable and can cease to function if

it is improperly bent.

Cat 6a 10 Gbps


Suitable for 10-Gigabit Ethernet.

A twisted-pair cable cannot be longer than100 meters.

Registered Jack-45 (RJ-45) connector Twisted-pair cabling uses four types of connectors: RJ-11, RJ-14, RJ-25 and RJ-45. The "RJ" in each

connector's name stands for "registered jack," and the number refers to the specific wiring pattern used for the

jacks and connectors. Usually RJ-11, RJ-14 and RJ-25 are used for telephone connections.

Twisted-pair network cables use RJ-45 connectors. An RJ-45 connector (shown in the following figure) is

slightly larger than the RJ-11 standard telephone connector. The RJ-45

connector holds up to eight wires, although only four of the wires are used

for transmitting and receiving signals in a standard Ethernet or Fast

Ethernet installation. Gigabit Ethernet and Power over Ethernet (PoE)

installations use all four pairs of wires. A standard RJ-45 cable and

connector is shown.

Straight-through cables In twisted-pair wiring, two wires send data and two wires receive data. In a straight-through cable, both ends of

the cable are wired into the connectors the same way. In other words, the same wires in the cable are

connected to the same pins in the connectors at each end. Straight-through cables are used for Ethernet patch

cables. You would use a patch cable to connect workstations to a hub or switch, for example.

MMM Optional Activity

3-1: Understanding Ethernet Wiring

MMM Optional Exercise

3-1: Wiring an RJ-45 Connector



You cannot use a straight-through cable to directly connect two computers. If Computer A is connected directly

to Computer B with a straight-though cable (that is, a standard RJ-45 patch cable) and sends data to Computer

B, then Computer B would receive the data on the wires intended for transmitting, not receiving. Hubs and

switches translate these wiring sets. When a wire is plugged into a hub, the transmit wires are remapped to

connect to the receiving wires on other cables connected to the hub.

Crossover cables A crossover cable for Ethernet networks is a specialized cable that allows you to connect two computers

directly without using an intermediary device such as a hub or switch. The crossover cable reverses, or crosses

over, the respective PIN contacts. Whereas straight-through cables are wired the same way on both ends,

crossover cables use the standard wiring on one end, and the reverse wiring for the transmit and receive pins

on the other end.

HomePlug Another option for wiring a home network is to use your home's electrical wiring system as your transmission

medium. Also referred to as Ethernet over Power, HomePlug is a standard for adapter devices that can be

plugged directly into a wall electrical outlet.

A HomePlug adapter looks something like a power transformer. After plugging the HomePlug adapter into an

outlet, you plug your computer into the HomePlug device using an Ethernet cable, and you can then connect to

other network devices in the house that are also plugged into HomePlug adapters. Some network devices plug

in using a cable; others have HomePlug technology built in and can be plugged directly into the adapter.

To learn more about HomePlug, visit the HomePlug Alliance Web site at www.homeplug.org. To view a

YouTube video about HomePlug, visit http://www.youtube.com/watch?v=93qPlc8yjb8.

IEEE LAN Standards As you learned in Lesson 2, the IEEE is an organization of professionals that creates standards for computers

and communications. The IEEE 802 series of standards specifies various LAN technologies, including Ethernet,

token ring and wireless technologies. The 802.3 group of standards defines Ethernet networks.

Ethernet The original Ethernet standard offers throughput of 10 Mbps. Although coaxial and fiber-optic cable can be

used, this standard is most commonly implemented using twisted-pair cable. A standard Ethernet network over

twisted-pair cable is also referred to as 10BaseT. This designation signifies the theoretical maximum data

transfer speed (10 Mbps), the type of transmission – (baseband, a form of transmission in which the entire

media bandwidth is used for a single channel), and the type of transmission media (twisted-pair cable).

All networks that use Ethernet use an access method called Carrier-Sense Multiple Access/Collision Detection

(CSMA/CD). In this access method, a system that wants to transmit data across the transmission medium must

first ensure that no other transmission is already in progress. If no other system is transmitting, the sender can

begin transmitting immediately. If another system is using the medium, the potential sender must wait.

Collisions occur when two or more systems sense that the medium is idle and begin to transmit simultaneously.

In the event of a collision, all transmission ceases while the colliding systems are notified. The colliding systems

then wait a random amount of time before retransmitting.

IEEE 802.3 series Several standards of Ethernet are in use today. Each is distinguished from the others primarily by its theoretical

maximum transfer rate. When devices using different standards connect, they exchange information about their

data transfer capabilities, such as their maximum speed, and whether they support half-duplex or full-duplex

communication. After exchanging information, they determine the most efficient way to communicate. This

process is called auto-negotiation.



Standard Name Speed Comments

802.3 Ethernet 10 Mbps Can use coaxial cable, twisted-pair or fiber.

802.3u Fast Ethernet 100 Mbps Can use twisted-pair or fiber.

Most NICs support speeds of 10 Mbps and 100 Mbps

and are designated as 10/100 Mbps.

802.3z Gigabit Ethernet 1 Gbps This specification is for fiber.

802.3ab Gigabit Ethernet 1 Gbps This specification is for twisted-pair. This specification

uses all four twisted pairs in the cable.

802.3ae 10-Gigabit Ethernet 10 Gbps This specification is for fiber.

802.3an 10-Gigabit Ethernet 10 Gbps This specification is for twisted-pair and requires Cat 6,

Cat 6a or Cat 7 cable.

Case Scenario 3-1 When Sharing Isn't Good

Sparks, Inc., a small subsidiary of DreamPages, LLC, is having network problems. As the office has grown, and

more people have been hired, the network has been slowing steadily. It is slow enough now that many

employees are extremely frustrated.

Ken, one of the IT technicians from the DreamPages corporate office, has come to investigate what the problem

might be. He checks the wiring, the network adapter cards and the networking devices in the office and finds the

following conditions:

All the wiring is Cat 5.

All the NICs are 10/100 Mbps cards.

The networking devices include several hubs and one router that provides access to the Internet.

As a class, discuss Ken's findings and decide upon a solution that might speed things up. Is the wiring

substandard? Does this office need more networking equipment?

Wireless Technologies Wireless technologies use free space as a transmission medium. The four main free space transmission

options are infrared, microwave, satellite and short-range wireless. Infrared, microwave and satellite are briefly

described in the following table.

Technology Description

Infrared Uses low-frequency infrared light to transmit signals. These signals have a very limited range

and require a clear path (referred to as line of sight) between the transmitter and the receiver.

PCs often use infrared signals to communicate with cordless mouse devices.

Microwave Microwave signals line-of-sight signals sent by dish-shaped antennas mounted on towers.

Higher towers allow for greater signal range. Towers that are 100 meters high can transmit

100-km distances between towers. Because the signals are line of sight, they can be

adversely affected by storms.

Satellite Satellites make it possible to transmit information between two stations that are not within

each other’s line of sight. Satellites receive a transmission from one earth station, regenerate

the signal (weakened by the distance), and transmit it to another earth station.



Radio Waves Wireless (mobile) phones and most wireless NICs and access points are radios, and they rely on the sending

and receiving of radio waves. A vast variety of radio-wave dependent devices are in common use today,

including:

cell phones

garage door openers

microwave ovens

wireless microphones

care key/keyless remote controls

baby monitors

wireless access points and NICs

Bluetooth devices

Radio Frequency (RF) Radio waves have different frequencies. To pick up a specific frequency, you tune in to it on a receiver. Radio

frequencies (RF) range from around 3 Hz to 300 GHz. A frequency band is a group of radio frequencies that

are adjacent to one another.

Frequency band usage is controlled by governments in most countries, and wireless devices are designed to

operate within their assigned frequency band. For example, the 2.4-GHz band has been designated for

lower-power unlicensed use. Many consumer devices operate in this band.

Range and interference Short-range wireless does not require line-of-sight transmissions, so it can operate through office walls in most

buildings. However, the environment in which a wireless device operates limits its range. For example, a

2.4-GHz device out in the open air has a range of between 120 and 200 meters. In a closed environment where

the signals must pass through wood or brick walls, the range is reduced to between 15 and 25 meters. In an

obstructed environment where the signal must pass through metal reinforced walls, ceilings and elevator

shafts, the signal range is reduced to 10 meters, and may not be able to sustain a connection at all.

Wireless communications are also subject to interference from other devices operating on the same frequency.

For example, the 2.4-GHz frequency is very popular, and various wireless devices such as cordless phones,

Bluetooth devices and microwave ovens use it. These devices can interfere with wireless LANs.

Bluetooth Bluetooth is a short-range wireless protocol that was developed for peripheral device communication. The

technology is named for King Harald Blaatand ("Bluetooth") of Denmark, who united Denmark and part of

Norway into a single kingdom in the late 900s.

Bluetooth allows you to form personal area networks. These are networks in which Bluetooth-enabled devices

in close proximity to each other can communicate directly without cables. Bluetooth-enabled devices can

include personal computers, portables, mobile phones, PDAs, headsets, etc.

Bluetooth operates in the 2.4-GHz frequency band, is easy to configure and is especially useful for short-range

connections, such as those within a single room.

Currently, the three classifications for Bluetooth devices are as shown in the following table.

Bluetooth Class Range

Class 1 Up to 328 feet (100 meters)

Class 2 Up to 33 feet (10 meters)

Class 3 Less than 10 meters

Bluetooth is not designed to replace wireless LAN technologies because its range is too limited. Its main

purpose is to simplify the process of connecting computer devices within a confined area, such as a home.

You can learn more about Bluetooth by visiting www.bluetooth.com.



Wireless Networking Modes The two types of wireless networking modes are:

Ad-hoc, in which systems use only their NICs to connect with one another. This mode is also known as

peer-to-peer mode, and is not a secure mode for networking. It also does not give the wireless clients

access to the Internet.

Infrastructure, in which systems connect via a centralized access point, called a wireless access point

(AP). From a network administration standpoint, infrastructure mode is preferable to ad-hoc mode because

it offers at least some degree of control. The AP can control which wireless systems are allowed to

connect. If the AP is connected to a wired network and that network provides Internet access, then the

wireless clients also have access to the Internet.

The following figure illustrates the ad-hoc and infrastructure modes.

Wireless access point (AP) The wireless access point acts much like a standard hub or switch in that it allows wireless systems to connect

to it so they can communicate with one another. If the wireless AP is attached to a standard Ethernet switch or

router, the wireless clients are also connected to the wired network.

The wireless AP is configurable, usually through a Web-based interface. You can configure the AP in order to

enable encryption, set the network name, specify whether or not to advertise the AP's availability, or allow only

specific wireless clients to connect.

Most modern wireless APs are wireless broadband routers. As such, they include firewall and DHCP server

functionality. In addition to providing wireless access, they often include several Ethernet ports that can be used

to connect standard (that is, non-wireless) clients to the network. You connect the wireless router to the rest of

your wired network by attaching one end of an Ethernet cable to the wireless router's WAN port, and the other

end of the cable into the Ethernet port on a DSL or cable modem, or an Ethernet port on a corporate

networking device, such as a hub, switch or router.



Service Set Identifier (SSID)

and Basic Service Set

Identifier (BSSID)

Every access point creates a wireless cell; to differentiate one wireless cell

from another, the access point provides an identifier called the Basic Service

Set Identifier (BSSID). The BSSID is usually the MAC address of the access

point, and its only function is to differentiate one wireless cell from another.

A Service Set Identifier (SSID) is a text string that identifies the wireless

network created by the access point. It is the wireless network name. An SSID

is 32 bits long; that is, it can include up to 32 characters. The SSID, or network

name, is used in the wireless authentication process. Any wireless device

attempting to connect to an access point must know the correct SSID. A

wireless device (client) is not permitted to join the wireless cell unless it can

provide the unique SSID.

The default SSID is often the vendor’s name, and it is highly recommended

that you change the default SSID to begin securing your wireless network.

Beaconing

When an access point is ready to accept connections from wireless clients, it

broadcasts its SSID so wireless clients within range will know of its presence.

This process is referred to as beaconing. (As a measure for tightening

wireless security, you can disable beaconing in the access point.)

Wireless Ethernet Elements The following table describes the basic elements found in a wireless Ethernet network.

Wireless Element Description

Wireless NIC The wireless NIC is installed on the PC or laptop to make it a wireless client.

These come in numerous forms and can be inserted PCI or PCMCIA cards, or as

USB or FireWire devices.

Configuration software

for the wireless NIC

Wireless NICs must be properly configured to work with the wireless access point,

so they include configuration software. Many wireless NICs include self-

configuration capabilities as well.

Wireless access point

(AP)

This is the wireless counterpart to a standard Ethernet hub or switch. The access

point provides centralized access to multiple wireless clients. If the wireless AP is

connected to a standard (wired) Ethernet hub, switch or router, the wireless clients

also have a connection to the wired network.

Configuration software

for the access point

Wireless access points can be configured to suit the needs of your network. Most

access points are configurable through a Web-based interface. To set the initial

configuration of an access point, you would connect it to a PC or portable using a

network cable.

Antenna Wireless clients and access points require an antenna. The antenna can be

encased inside the device or attached to the outside. Often, it is possible to attach

more powerful antennae to increase the range at which the wireless network will

function.

Service Set Identifier

(SSID)

The unique name of the wireless network. SSIDs are case-sensitive and 32 bits

long.

Beacon When a wireless AP is ready to accept connections, it sends a special Ethernet

frame called a beacon management frame to inform clients of its availability. The

beacon includes the SSID, which is required for any client to access the AP. The

beacon can be turned off to increase security.

MMMOptional Exercise 3-2: Configuring a Wireless Network

Wireless network security will be covered in detail later in this course.



Wireless LAN (WLAN) Standards The IEEE 802.11 specification for wireless Ethernet was introduced in 1997. It standardizes wireless LAN

equipment and speeds. The following table summarizes the most commonly implemented specifications for

wireless LANs.

You will note in the table that the term "WiFi" (which is short for wireless fidelity) at one time applied only to

products adhering to the 802.11b specification. However, today the term WiFi applies to all products that use

the 802.11 standard. The 802.11 specifications are a set of evolving wireless standards called the 802.11

family. The particular specification under which a wireless network operates is called its "flavor."

Specification Speed Frequency

Range

Comments

802.11a 54 Mbps 5-GHz band Offers stronger encryption and more authentication features

than 802.11b, and includes error correction to guard against

data loss. Not compatible with 802.11b or 802.11g.

802.11b 11 Mbps 2.4-GHz band Subject to interference from microwave ovens, cordless

phones and Bluetooth devices, which operate in the same

band. Uses weak encryption and authentication, but is

inexpensive and easy to install.

802.11g 54 Mbps 2.4-GHz band Backward-compatible with 802.11b (but only at 802.11b

speeds). Offers security features similar to those provided

by 802.11a networks.

802.11n 300 Mbps 2.4-GHz band

and

5-GHz band

Offers higher speed, more capacity, more security and

twice the range of 802.11g equipment. Enables high-

bandwidth applications such as streaming video.

IEEE 802.11 amendments To improve security and to help ensure high-quality service, the following amendments have been added to the

802.11 standard:

802.11e Provides Quality of Service (QoS) standards for wireless networks, enabling them to

carry delay-sensitive packets, such as those for Voice over Wireless LAN (VoWLAN)

and streaming media.

802.11h Solves problems with wireless networks operating in the 5-GHz band from interfering

with satellites and radar, thereby making them acceptable in Europe and in several

other countries.

802.11i Specifies security mechanisms for wireless networks. This specification, also known as

WiFi Protected Access (WPA and WPA2), provides improved encryption for networks

that use 802.11a, 802.11b and 802.11g. The original security mechanism for wireless

networks was Wired Equivalent Privacy (WEP), but WEP had severe security

weaknesses. WPA was developed as an intermediate solution for the weaknesses in

WEP. WPA uses a security protocol called Temporal Key Integrity Protocol (TKIP),

which could be implemented (through a firmware upgrade) on older wireless NICs that

had been used as far back as 1999. WPA2 uses a security protocol based on the AES

encryption cipher. New wireless devices support WPA2.

IEEE 802.11 access method In contrast to wired Ethernet, which uses Carrier-Sense Multiple Access/Collision Detection (CSMA/CD), the

access method for the IEEE 802.11 specifications is Carrier-Sense Multiple Access/Collision Avoidance

(CSMA/CA), which specifies that each node must inform other nodes of an intent to transmit. When the other

nodes have been notified, the information is transmitted. This arrangement prevents collisions because all

nodes are aware of a transmission before it occurs.



Case Scenario 3-2 Wireless in the Workplace

Dean, the IT manager for DreamPages LLC, has been asked to give three sales employees wireless access to

the corporate network. Each of the three has a laptop and none of the three has a permanent office space in the

building.

Dean has some old 802.11b wireless USB NICs and an old wireless access point on hand.

After researching wireless standards and equipment on the Internet, Dean decides the best way to provide

wireless access to the network and the Internet while still protecting the corporate network is to take the following

steps:

He discards the 802.11b NICs and buys three new 802.11n NICs for the laptops.

He buys a new 802.11n wireless access point.

As he configures each wireless client, he disables their ability to participate in ad-hoc networks.

As a class, discuss each of Dean's decisions. Why do you think he took these particular steps? Do you agree

with his decisions? What else might Dean do to protect the corporate network?

How the Internet Works Every computer connected to the Internet uses TCP/IP, which enables computers to establish a communication

link and exchange packets of data. Most client systems are connected to the Internet through gateways, which

connect their LANs to the Internet backbone. Computers access information from the Internet in the following

sequence:

You request data through your LAN from a server connected to the Internet.

1. The request is divided into packets (and then frames), then sent onto the transmission medium.

2. The packets pass through your LAN, and potentially through other networks, to the Internet backbone.

3. The packets are routed from the Internet backbone through one or more networks until they reach the

destination server containing the requested information.

4. The destination server sends information in response to your request using the same process, although

possibly following a different route.

TCP/IP ensures that your information is transferred quickly and reliably. Internet routers determine the best

route for the packets to travel; they also recognize damaged connections and send data through alternative

routes. If a packet is lost, TCP/IP re-sends the missing packet. The destination computer collects the packets

and reassembles them into your original data.

Internet Service Providers (ISPs) An Internet Service Provider (ISP) is an organization that provides access to the Internet, and usually e-mail as

well. Most ISPs charge a flat monthly rate. Some basic-service ISPs offer Internet connectivity for free, such as

NetZero (www.netzero.net) and Juno (www.juno.com) in the United States.

Some providers offer dial-up connection, and most offer direct connection through DSL cable or wireless

connection such as satellite.

Objective

1.1



Internet Protocols Now that you are familiar with networking equipment and services, you may better understand how some of the

Internet protocols work. Protocols and services are usually associated with a specific port number. A port

number is used by the receiving computer to identify which specific process a given packet requires. For

example, a Web server typically "listens" on port 80 for incoming requests for a Web page. The following table

describes several protocols that are part of the TCP/IP suite. Two additional protocols, Dynamic Host Control

Protocol (DHCP) and Domain Name System (DNS), are discussed in sections following this table.

Protocol Description

Hypertext Transfer

Protocol (HTTP)

The protocol used to transfer Web pages from a Web server to a client, usually a Web

browser. HTTP can also be used to upload information to a server, for example,

through filling out a Web form. The default port for HTTP is port 80.

HTTP over Secure

Sockets Layer

(HTTPS)

A secured version of HTTP used to transfer Web pages from a secure Web server to

a Web client. HTTPS is often used for payment transactions. When you access a

secure Web page, the URL starts with https://. The default port for HTTPS is port 443.

Secure Sockets

Layer (SSL)

A protocol that provides security for communication across the Internet. Most servers

use SSL for secure exchanges. SSL authenticates using digital certificates and

provides for data encryption. (Digital certificates are equivalent to ID cards, and help

prevent fraudulent use or misrepresentation of your personal or company information,

and that of other Internet-based entities.) All major browsers, such as Microsoft

Internet Explorer, Mozilla Firefox, NCSA Mosaic and Lotus Personal Web Browser,

support SSL 3.0.

File Transfer

Protocol (FTP)

This protocol is used to transfer files between computers. It includes commands for

uploading and downloading files, and for requesting directory listings from remote

servers. FTP is implemented in standalone programs (for example, FileZilla or

CuteFTP), as well as in Web browsers. FTP can transfer text, images, audio, video

and binary files. Binary files are executable programs. Many Web browsers and e-mail

clients do not allow binary files to be transferred because of security risks, but FTP

does not restrict the file type. The default port for FTP is port 21.

Simple Mail

Transfer Protocol

(SMTP)

SMTP is the Internet standard protocol for transferring e-mail messages between

e-mail servers. It is also used by e-mail clients to send messages to an e-mail server.

SMTP is responsible only for sending messages; it is not used to retrieve e-mail

messages. Other protocols, such as Post Office Protocol version 3 (POP3) or Internet

Message Access Protocol (IMAP4) are used to retrieve mail. The default port for

SMTP is port 25.

Post Office

Protocol version 3

(POP3)

POP3 stores incoming e-mail, and includes commands for downloading messages

and deleting them from the server. You must download your messages to read them.

By default, most e-mail clients copy messages to the local hard disk and then delete

the messages from the server, although you can change the configuration to leave

messages on the server for either a specified number of days or until you delete them

manually. The default port for POP3 is port 110.

Internet Message

Access Protocol

version 4 (IMAP4)

In addition to allowing you to retrieve e-mail messages, IMAP4 allows you to store and

manage your messages on the e-mail server. You are not required to download

messages to read them. The default port for IMAP4 is port 143.



Dynamic Host Control Protocol (DHCP) Dynamic Host Control Protocol (DHCP) automatically assigns IP addresses to nodes on a TCP/IP network.

Additional information, such as the subnet mask and the default gateway’s IP address, are also assigned.

DHCP can save network administrators a great deal of time because it frees them from having to manually

configure each computer on the network.

When DHCP is used, a client system receives its TCP/IP configurations when it starts up or reboots. DHCP

assigns these configurations on a lease basis. For instance, your computer receives an IP address that may

expire after 24 hours. After the lease expires, the IP address can then be leased to another computer on the

network, or it may be renewed by the same computer.

In Windows 2000/XP/Vista and Windows 7, you can release and renew your IP address using the ipconfig

command. (You have already observed this in an exercise you completed earlier in this lesson.)

The two versions of DHCP are DHCPv4 and DHCPv6. DHCPv4 works with IPv4, and DHCPv6 is designed to

work with IPv6. The default port number for a DHCPv4 server is port 67; the default port for the client is port 68.

The default port number for a DHCPv6 server is port 546; the default port for the client is port 547.

Domain Name System (DNS) To access any site on the Internet, you must enter its address in your browser. You could enter an IP address,

but because these are difficult to remember, the Domain Name System (DNS) provides a solution. The Domain

Name System (DNS) maps unique names to specific IP addresses.

DNS resolves IP addresses into their text-based names. For example, you can access the CCI Learning

Solutions Web server at IP address 96.53.76.108 by typing www.ccilearning.com in your browser's Address

box. In other words:

96.53.76.108 = www.ccilearning.com

Both the domain name and the IP address refer to the same resource, but the domain name is easier to

remember. Without DNS, you would need to enter an IP address any time you wanted to access a resource on

the Internet.

A good way to remember a domain name is to understand its naming hierarchy. A typical DNS name is

composed of three parts: a server (host) name, a registered company domain name and a top-level domain

name. The following figure illustrates the various parts of a domain name.

Read from right to left, a domain name signifies general divisions, then specific departments or individual

computers within a company. For example, reading right to left, the domain name www.ccilearning.com can be

interpreted that:

The Web site is a commercial site (.com is the top-level domain for businesses).

The registered domain name for the company is ccilearning (each domain name is unique and registered

with the Internet Corporation for Assigned Names and Numbers (ICANN)).

The name of the Web server hosting the site is "www".

The DNS service is made possible through domain name servers, which are servers on the Internet whose sole

function is to resolve domain names into their IP addresses. For example, when you enter a URL such as

www.ccilearning.com into your browser's Address bar, the browser contacts a domain name server to obtain

the IP address related to this domain name. When the browser receives the IP address 96.53.76.108 from the

domain name server, the CCI Learning Solutions site displays on the screen. The default port for DNS is

port 53.

www.ccilearning.com

Server Name Company Domain Name Top-level Domain



Top-level domains The right-side component of a domain name categorizes domains into groups by common type (for example,

company, educational institution) or geography (country, state). These categories are called top-level domains.

The original top-level domains are as follows:

com commercial or company sites

edu educational institutions

org organizations (originally limited to nonprofit groups)

mil military organizations

gov government organizations

net Internet organizations (hosting companies and ISPs)

int international organizations

Other top-level domain names use a two-letter abbreviation to indicate states and countries. A few examples of

geographic domain names are listed here:

au Australia

ca Canada

dk Denmark

fr France

jp Japan

mx Mexico

uk United Kingdom

Additional top-level domain names were created to keep up with the demands of a growing Internet. These are

categorized by topic and include the following:

aero travel industry

biz businesses

coop cooperatives

info content and research-related sites

museum museums

name personal Web addresses

pro professional

Web Browsers Web browsers (or browsers) are software applications that enable users to easily access, view and navigate

Web pages on the Internet. You may be familiar with several browsers, such as Microsoft Internet Explorer,

Mozilla Firefox, Google Chrome, Apple Safari and Opera.

As you most likely know, a Web browser’s primary function is to retrieve pages from a Web server and display

those pages on your screen. Millions of people use browsers every day for research, shopping, entertainment,

etc. While just about anybody can open a browser and browse the Web, an IT professional can understand the

processes at work, identify and avoid potential risks, and configure a browser to suit the working styles of

employees and conform to any corporate standards.

Installing a Web Browser Microsoft Windows 7 comes with Internet Explorer 8.0 installed. Other browsers offer the same functions as

Internet Explorer, but present slightly different interfaces. Often the arrangement of menus and toolbars differs

and some users may prefer one over another. You can download and install other browsers from the Web.

Usually, an installation wizard guides you through the necessary steps. A wizard is a tool that provides step-by-

step instructions for completing a task.



Exercise 3-3 Installing a Web browser

In this exercise, you will download and install the Mozilla Firefox Web browser. This browser is created and

supported by the Mozilla foundation.

1. Open Internet Explorer, click in the address bar, type: www.mozilla.com and press (if necessary) to

go to the Mozilla Web site. Your browser screen should resemble the following figure:

2. On the Mozilla Web page, click the Download Firefox - Free button.

3. When the File Download - Security Warning box appears, click the Run button to begin downloading the

necessary files.



4. When the Internet Explorer - Security Warning box appears, click the Run button to extract the files and

begin the installation.

5. If the User Account Control warning box appears prompting you to verify that you want to allow the listed

program to make changes to the computer, click the Yes button to display the first screen of the Firefox

installation wizard.

6. Click the Next button to display the Setup Type screen.

7. Make sure Standard is selected, then click the Next button to display the Summary screen.

Click Yes whenever the Use Account Control warning box appears during the performance of this exercise.



8. Deselect Use Firefox as my default web browser, then click the Install button.

9. When the installation is complete, click the Finish button.

10. When the Import Settings and Data screen appears, click Don't import anything, then click the Next button

to open the Firefox browser.

If the Default Browser message box appears, deselect Always perform this check when starting Firefox,

then click No. Both the Welcome to Firefox and the Mozilla Firefox Start Page pages display in separate

tabs.

11. Close the Firefox browser, and click the Quit button to close both open tabs.

12. Close Internet Explorer. Notice that the Firefox installation program created a shortcut on your Desktop for

Firefox.

In this exercise, you installed a browser. Did you find it to be a complicated process or an easy one? Do you think

you might install other browsers?

Configuring Web Browser Preferences Although browsers in their default configurations are easy to use, you can change your browser's configuration

to accommodate your personal working style, or to ensure it complies with standards implemented by your

organization. The mechanics of configuring a browser differ slightly from one browser to another, but all are

generally equally configurable.

Browser fonts Adjusting the size of the fonts used within the browser window can help a user work comfortably. This setting is

important for users who have high-resolution monitors, such as 1024 x 768, 1280 x 1024 or larger. Adjusting

font size can improve readability on any monitor. This setting can be especially important for a user who is

visually impaired.



Browser home page The home page is the first Web page that appears in the browser window when you open a browser. Most

browsers come with a preset default home page. For example, in Internet Explorer, the default home page is

the MSN page. In Firefox, the default home page is the Mozilla Firefox Start page.

Many users set their home pages to search engines or favorite Web sites. However, many corporations prefer

that employees set their browser home pages to the company's Web site.

History folder The History folder stores the URLs of sites you have accessed within a defined period of time, and provides a

convenient way to revisit Web sites, especially if you cannot remember the exact URL. In Internet Explorer, the

default amount of time to keep pages in History is 20 days. If you use the Web for a lot of tasks, the History

folder can become unmanageably large. A large History folder can be difficult to use, uses considerable disk

space (which slows down disk maintenance tasks), and can slow the browser speed. You can, however, adjust

the time period for storing pages, and you can empty the folder manually.

Anti-phishing features Phishing is the process of trying to gather sensitive information such as a password, or credit card details from

an unsuspecting victim by pretending to be a trustworthy entity. Typically, a phisher sends a legitimate-looking

e-mail message that directs the recipient to visit a fake Web site that looks identical to a legitimate site. Victims

are then asked to update personal information (such as password, credit card, or bank account numbers) on

the fake Web site. The phisher can then use the captured information for malicious purposes.

Many browsers include anti-phishing features which analyze Web pages and display a warning message if a

Web site contains characteristics that make it appear suspicious. Internet Explorer checks Web pages against

a dynamic list of reported phishing sites. You can also report a Web site that you suspect might be unsafe.

Firefox receives updates on Web site forgeries every half hour.

Pop-up blocker A pop-up is a small browser window that suddenly opens in front of the page you are viewing. Pop-ups contain

command buttons or options that must be selected before you can continue with the current task. Pop-ups can

remind a visitor to log on or to enter required information, but they are also used extensively for advertising on

the Web, and many users find them annoying because they remain open until you click an option or manually

close them.

Many browsers include built-in pop-up blockers. In Internet Explorer, the pop-up blocker is enabled by default.

However, it is important to know how to fine-tune the function of the pop-up blocker so important messages (for

example, log on windows, or session time-out warnings) are allowed to display.

Browser cache size The browser cache is a folder on your hard drive that stores downloaded files (such as Web pages, images,

fonts, etc.). The cache improves your browser’s performance because it allows you to view previously

accessed Web pages without having to request them from the server again. For example, if you click a

hyperlink on a Web page, then click the browser's Back button, the browser can pull the previously viewed

page from the cache.

When you enter a URL, your browser checks the cache to see if the page is already stored there. If the cache

contains a recent version of the page, it will display the cached version instead of downloading the page from

the Web again. Loading cached pages is much faster than downloading them from a server.



A cache that is too large or too small can slow the browser. The browser cache should be large enough to

speed performance, but not so large that it slows down your computer. Finding the optimum size is usually a

matter of trial and error. If the cache is too small, you spend a lot of time waiting for pages to download from the

server. On the other hand, if the cache is too large, the browser must search through hundreds of cached files

to locate a specific page. A very large cache can also slow down other tasks such as disk defragmentation or

virus scans. You can adjust the size of the browser cache on the Temporary Internet Files and History Settings

dialog box in Internet Explorer, as shown in the following figure.

In Firefox, you can configure this setting on the Network tab of the Advanced Options dialog box, as shown in

the following figure.



Deleting temporary Internet files Because a browser automatically deletes old cached files when the cache is full, it is theoretically unnecessary

to manually delete the temporary files. However, you may want to delete these temporary files:

before running a virus scan or a disk defragmentation

when you want to free up disk space

before beginning a new browser session to ensure that you get the most current pages

Exercise 3-4 Working with Browser settings

In this exercise, you will work with browser settings in Internet Explorer 8.0.

First you will adjust the font size and zoom setting.

1. Open Internet Explorer, click in the address bar, type: www.msn.com and press

(if necessary) to go to the MSN Web site.

2. Take note of the text size on the page. In the toolbar that appears in the upper-right corner of the browser window, click Page, then point to Text Size. Notice that the

default text size is Medium.

3. In the Text Size sub-menu, click Larger, as shown in the following figure. Notice

how the text size increases on your screen.

4. Click Page, point to Text Size, then click Largest and observe the result.

5. Click Page, point to Zoom, then click Zoom In and observe the result.

6. Close Internet Explorer, then reopen it. Notice that your adjusted settings are still in effect.

If you are outside the U.S., you may need to choose a local MSN site before continuing.



7. Click in the address bar, type: www.desertschools.org, and press to view the Desert Schools

Federal Credit Union page. Notice that text on this page also reflects the modified settings.

8. Return the Zoom setting to 100%, then return the Text Size setting to Medium.

Next, you will specify a new home page.

9. Go to www.ccilearning.com.

10. In the toolbar, click Tools, then click Internet Options to open the Internet Options dialog box.

11. In the Home page section, click the Use current button to specify the CCI Learning Solutions Web site as

your new home page. The Internet Options dialog box should resemble the following figure.

12. Click Apply, then click OK to apply the new setting and close the Internet Options dialog box.

13. Visit your favorite Web site, then click the Home button in the toolbar to verify that the new setting has been

applied.

Next, you will examine the anti-phishing function, which is part of the SmartScreen Filter.

14. In the toolbar click Safety, point to SmartScreen Filter, then click Check This Website. Internet Explorer

should display the message box shown, indicating that the site has been analyzed and no threats were

found.

15. In the SmartScreen Filter dialog box, click OK.

Next, you will examine the pop-up blocker settings.



16. In the toolbar, click Tools, point to Pop-up Blocker, then click Pop-up Blocker Settings to open the

Pop-up Blocker Settings dialog box.

Notice that you can allow pop-ups from specific Web sites by adding their URLs to the list of allowed sites.

For each site that you wish to allow, click in the Address of website to allow text box, type the URL and

click the Add button.

17. In the Blocking level section, display the drop-down list. Notice that you can set your level of protection to

Low, Medium or High.

18. Close the dialog box without making any changes.

Finally, you will examine settings for the History folder and browser cache, and you will delete your browsing

history and temporary files.

19. In the toolbar at the upper-left of the browser window, click the Favorites button, click the History tab, then

click Today to display your browsing history.

20. In the toolbar, click Tools, then click Internet Options to open the Internet Options dialog box.



21. In the Browsing history section, click the Settings button to open the Temporary Internet Files and History

Settings dialog box.

22. Notice the size of the browser cache. Do you think it is large? Small? About right?

23. Click the View files button to open the Temporary Internet Files folder in Windows Explorer and scroll

through the files. Are there more files than you expected to see?

24. Close the Windows Explorer window, then close the Temporary Internet Files and History Settings dialog

box without making any changes.

25. In the Browsing history section of the Internet Options dialog box, click the Delete button to open the Delete

Browsing History dialog box.

Notice that you can specify which types of files to delete or retain.

26. In the Delete Browsing History dialog box, click the Delete button to delete the history and the files in your

browser cache.

27. Close the Internet Options dialog box, then redisplay the History folder. Were any items retained?

28. Close any open dialog boxes if necessary, then close Internet Explorer.

In this exercise, you worked with browser settings in Internet Explorer 8.0.

Cookies Cookies are small text files placed on your computer when you visit a Web site. Cookies are simple files that

store information about your preferences. For example, a cookie might be used to store information about your

actions, such as the options you clicked on the Web page, or which browser you used when you accessed the

site.

If you configure your browser to allow cookie downloads from Web sites, then each time you revisit a site, your

computer will send the cookie to the Web server. Once a cookie is saved on a computer, only the Web site that

created the cookie can read it.

MMMOptional

Exercise 3-3: Configuring Settings in

Firefox



The different types of cookies are outlined in the following table:

Cookie type Comments

Persistent cookie Stored on your computer; remains there after you close your browser.

Session cookie Stored only during the current browsing session; is deleted when you close your

browser.

First-party cookie Comes from the Web site you are currently viewing.

Third-party cookie Comes from a Web site other than the one you are currently viewing, such as from a

Web site that provides advertising content on the site you are currently viewing.

Cookies cannot collect personal information about you unless you specifically register with a Web site and

provide that information. However, they are often viewed as a threat to privacy.

Because cookies are useful and harmless, both Internet Explorer and Firefox allow them by default. However,

you can control how cookies are handled in each browser. Depending on security settings, the browser warns

users before accepting a cookie, and allows users to view, restrict or disable cookies completely.

Controlling cookies In Internet Explorer, you can use the Privacy tab of the Internet Options dialog box (shown in the figure below)

to specify the level of privacy you want to maintain. This setting controls when and from whom cookies are

accepted. You can also use the advanced privacy settings to configure your browser to override automatic

cookie handling and instead display warnings, or accept or block first-party and third-party cookies.

Exercise 3-5 Controlling cookies in Internet Explorer

In this exercise, you will use the Privacy tab of the Internet Options dialog box to control how cookies are handled

in Internet Explorer.

1. Open Internet Explorer.

2. In the toolbar, click Tools, click Internet Options, then click the Privacy tab to open the Internet Options

dialog box.



3. In the Settings section, drag the slider bar up and down to view how each level affects cookie handling in

the browser. Notice that different settings will present warnings or options, or block cookies completely.

4. In the Settings section, click the Advanced button to open the Advanced Privacy Settings dialog box.

5. Select Override automatic cookie handling to make the options available.

6. Select Prompt for both First-party and Third-party cookies to specify that you want to be notified when a

Web site tries to give you a cookie.

7. Click OK twice to close the open dialog boxes.

8. Go to www.desertschools.org. Before the page loads, the Privacy Alert dialog box appears.

9. In the Privacy Alert dialog box, select Apply my decision to all cookies from this website, then click the

Allow Cookie button to accept the cookie and display the page.

10. In the toolbar click Tools, click Internet Options, click the Privacy tab and click the Advanced button.

Deselect Override automatic cookie handling, then click OK twice to close the open dialog boxes.

11. Close Internet Explorer.

In this exercise you controlled how Internet Explorer handles cookies.

Controlling Active Content You can configure your browser for added security by controlling active content downloading. Active content

includes any active or moving objects on a Web page. ActiveX controls and Java applets are examples of

active content. Both allow information to be downloaded and run on your system. Some corporate IT

departments require the disabling of active content as part of their security policy.

MMMOptional

Exercise 3-4: Working with

cookies in Firefox



You can use the Safety tab of the Internet Options dialog box to control the safety level for the Internet zone.

The safety levels determine whether certain types of active content are allowed, are allowed with a warning, or

are not allowed at all. The effects of the three safety levels are summarized in the following table.

Security level Effect on active content

High Active content will not display and a notification appears.

Medium-High Warning messages appears when you begin to download active content. You can elect to

open the file, save it to disk or cancel the download.

Medium Same as Medium-High, but more elements are allowed through than with the higher

setting. Exercise 3-6 Controlling active content in Internet Explorer

In this exercise, you will change safety levels for the Internet zone and observe the effects on a Web page that

contains active content.

1. Open Internet Explorer and go to www.desertschools.org. Notice the active content on the page.

2. In the toolbar, click Tools, click Internet Options, then click the Security tab to open the Internet Options

dialog box.

3. Make sure that Internet is selected in the Select a zone to view or change security settings area, then

drag the security level slider up and down to read how each level affects active content.

4. Return the security level slider to the Medium-High position, then click the Custom level button to open the

Security Settings dialog box.

You can use this window to examine how various types of content are handled by the browser at the current

security setting.

5. Scroll through the settings. Are there more types of content than you might have thought?



6. In the Reset custom settings section, display the Reset to drop-down list, select High, then click the Reset

button.

7. Click Yes when the warning box appears. Click OK, click Apply, then click OK once more to apply the

setting and close the open dialog boxes.

8. Click the Refresh button or press . What happens to the active content on the screen?

9. Click Tools, click Internet Options, then click the Security tab. Click the Custom level button, display the

Reset to drop-down list, then select Medium-High. Click the Reset button, then click Yes to reset the safety

level back to the default setting of Medium-High.

10. Click OK, click Apply, then click OK.

11. Click the Refresh button or press .

12. Ensure that active content displays once again, then close Internet Explorer.

In this exercise, you controlled how active content is handled in Internet Explorer.

Plug-Ins In order to present the interactive multimedia so abundant on the Web today, a browser requires applications

called plug-ins. Plug-ins are programs that extend the capabilities of Web browsers. When you visit a Web site

and your browser encounters a file type that it cannot natively support, you may be prompted to download and

install a plug-in so you can view the Web page properly.

Plug-ins are associated with a specific operating system (such as Windows or Macintosh) and sometimes with

a specific browser (such as Firefox or Internet Explorer). In Firefox, plug-ins are generally referred to as

Add-ons. Adobe Flash Player, Windows Media Player, and Real Networks RealPlayer are examples of popular

plug-ins.

Plug-ins generally have a particular file type associated with them. For example, Windows Media Player can be

used to play files that include the .wma (Windows media audio) and .wmv (Windows media video) file name

extensions. The player also supports several video and audio file formats (such as .avi, .mpeg, .midi, .wav).

Plug-in installation Internet Explorer and Firefox both include several native plug-ins. These are automatically installed with the

browser. However, as you browse the Web, you may be prompted to download and install new plug-ins or

update the plug-ins that are already installed. It is good practice to occasionally upgrade plug-ins because

upgrades frequently include increased functionality and security updates.

To install or upgrade a plug-in, it is often best to go to the vendor's site because that is where you will find the

latest version of the plug-in. Vendor sites also usually include information on the minimum system requirements

(operating system version, hard disk space, RAM, processor speed, etc.) required for the plug-in as well as

installation instructions.

Exercise 3-7 Installing Adobe Flash Player

In this exercise, you will visit the Adobe Web site, and download and install the Adobe Flash Player plug-in.

1. Open Internet Explorer and go to www.adobe.com to view the Adobe home page.

2. Click the Get Adobe Flash Player button to open the Adobe Flash Player installation page. Notice the

available links for information about the application, system requirements and installation instructions.

3. Click the System requirements link to open the Adobe Flash Player system requirements page in a

separate window.



4. Read the system requirements. Can your system run this application?

5. Close the Adobe Flash Player system requirements window, then click the Installation instructions link to

open the Adobe Flash Player installation instructions page in a separate window.

6. Notice that the page includes instructions for installing the plug-in on the Windows, Mac, Linux and Sun

Solaris operating systems. Read the brief instructions for Windows. Does the installation seem fairly

straightforward?

7. Close the Adobe Flash Player installation instructions window, then on the Adobe Flash Player installation

page, deselect the Free Google Toolbar (optional) option, then click the Agree and install now button to

begin the download process.

8. If an alert appears in a yellow bar at the top of the browser window, click inside the yellow bar and select

Install This Add-on for All Users on This Computer in the sub-menu that appears. Click the Yes button in

the User Account Control warning box. If the Adobe Download Manager window appears, click the Close

Download Manager button. When the installation is complete, a message will inform you that the Adobe

Flash Player was successfully installed.

9. Go to www.adobe.com/showcase to view a listing of Web sites that use Flash technology. Explore the

showcase, or click the link listed under SITE OF THE DAY.

10. Close Internet Explorer. Was it easy to install the Flash Player plug-in? What did you think about the

multimedia you viewed in the Flash showcase?

In this exercise, you installed the Flash Player plug-in in Internet Explorer.

You may be very familiar with plug-ins or they may be new to you. As you can see, installing and using plug-ins

is easy and it can greatly enhance a Web browsing experience. Whether or not you decide to pursue a career

as an IT professional, you should explore installing and updating plug-ins.

Lesson Summary In this lesson, you looked at various types of transmission media, networking hardware, Ethernet and

wireless networking standards and technologies, Internet protocols, and Web browser configurations. You

should now be familiar with:

Peer-to-peer and client/server networks.

LANs and WANs.

IP addressing.

Transmission media.

Function and characteristics of network hardware.

Protocols in the TCP/IP suite.

Data encapsulation.

Wireless networking technologies and standards.

Web browser configurations.

Exam Objectives

1.1 Identify basic IT vocabulary.



Review Questions 1. An IP address consists of:

a. 32 bits c. 128 bits

b. 64 bits d. 256 bits

2. The 32-bit number that is used to distinguish the network and host portions of an IPv4 address is called a(n):

a. default gateway c. switch

b. subnet mask d. dynamic host screen

3. Which of the following is an advantage of using IPv6 instead of IPv4?

a. IPv6 addresses are shorter and easier to remember.

b. The IPv6 address space is much larger than the IPv4 address space.

c. All network equipment, even legacy network equipment, supports IPv6, but not all network equipment

supports IPv4.

d. Systems on an IPv6 network can obtain IP addresses automatically, whereas systems on an IPv4 network

must be configured with a static IP address.

4. Which of the following statements concerning MAC addresses is accurate?

a. MAC addresses are used for addressing only by devices within the same LAN.

b. MAC addresses are leased for a certain period of time.

c. MAC addresses are 128 bits long.

d. MAC addresses include a network portion and a host portion.

5. A twisted-pair cable cannot be longer than:

a. 10 meters.

b. 100 meters.

c. 1,000 meters.

d. 10,000 meters.

6. Which of the following wireless networking specifications provides throughput of 300 Mbps?

a. 802.11a

b. 802.11b

c. 802.11g

d. 802.11n

7. Which of the following Internet protocols is responsible for sending e-mail messages?

a. Post Office Protocol 3 (POP3)

b. Internet Message Access Protocol 4 (IMAP4)

c. Simple Mail Transfer Protocol (SMTP)

d. File Transfer Protocol (FTP)

8. Which of the following is true of wireless ad-hoc mode?

a. In ad-hoc mode, clients connect to a central access point.

b. Ad-hoc mode is more secure than infrastructure mode.

c. In ad-hoc mode, clients connect directly to each other using only their NICs.

d. Internet access is always faster through ad-hoc mode.

9. Which of the following describes how devices on a wired Ethernet network access the transmission medium?

a. They alert other devices when they intend to transmit.

b. They transmit when they sense the medium is idle.

c. They transmit only when the processor sends a message indicating that it is permissible to do so.

d. All of the above.

10. Which of the following is true of cookies?

a. Cookies can read files on your hard disk in order to collect personal information about you.

b. Cookies are dangerous and are disallowed by most major browsers by default.

c. Cookies are text files.

d. Cookie files are very large.

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