Chapter 21 Fall 2007... · Web viewMost fiber optic Ethernet networks use 62.5/125 multimode fiber...

Mike Meyers’ A+ Guide to Managing and Troubleshooting PCs Instructor’s Manual Chapter 21

Chapter 21

Local Area Networking

Learning ObjectivesIn this lesson, you will learn how to set up and use a basic network. At the end of the lesson, you should

be able to do the following:

Explain network technologies

Explain network operating systems

Understand how to install and configure wired networks

Understand how to install and configure wireless networks

Troubleshoot networks

Pre-Test1. In the most basic terms, what is a computer network?

2. What is a router?

3. How fast is Bluetooth?

4. What is peer-to-peer networking? What is a client/server network?

5. At what layer of the OSI model does MAC addressing occur? At what layer, does the link light

occur?

Lecture Outline

Discussion Point

Networking

This chapter is long and includes complicated topics, even though it covers only some

networking concepts. There are entire courses designed around networking

technologies, such as CompTIA’s Network+. There are advanced certifications such as

the Microsoft Certified System Engineer (MCSE) and Certified Novell Engineer (CNE)

courses. There are entire courses for single networking topics such as TCP/IP. This

Copyright © 2007 by The McGraw-Hill Companies of 24


chapter will only familiarize you with the networking concepts and help you set up

simple networks, as per the requirements of the CompTIA A+ certification.

Historical/Conceptual

I. Networking technologies

A. The Big Questions. When network designers first sat down to design a system where two or

more PCs could share data and peripherals, they had to resolve many issues.

1. How will each computer be identified?

2. What kind of wire and connectors will be used? What are their limitations?

3. How can files be protected?

4. How can access to data and peripherals be controlled?

B. A few basics

1. A client machine is used to request information or services.

2. A network interface card (NIC) is used to identify the network client and break files into

smaller units called packets. The NIC sends data across the network and helps to

reassemble the data into whole files.

3. A medium is needed for delivering the packets: cable or wireless method.

4. A PC operating system is required to communicate with its own networking hardware and

other machines on the network.

5. A server machine needs to provide information and services.

C. Topology. The computers need to be connected in some logical or ordered way.

1. Bus topology. All computers connect to the network via a main line called a bus cable.

2. Ring topology. All computers connect to a central ring of cable.

3. Star topology. Computers on the network connect to a central wiring point (often a hub or

switch).

4. Mesh topology. Each computer has a dedicated line to every other computer.

Essentials



D. Packets/frames and NICs

1. PCs transfer data in the form of chunks called packets or frames.

2. Every network interface card (NIC) has a built-in identifier called the Media Access

Control (MAC) address. This address is unique to the specific network card.

3. The MAC is a 48-bit long identifier (provides more than 281 trillion MAC addresses). The

sender and recipient MAC addresses are added to the packet so each packet knows where it

came from and where it needs to go.

4. A packet contains the MAC address of the NIC for the recipient and the MAC address of

the sender, the data itself, and some kind of data check or cyclic redundancy check (CRC).

5. Networks must use the same hardware protocol to define everything necessary to transfer

data from one computer to another. The dominant hardware protocol today is Ethernet,

although Token Ring contended for many years.

a) Ethernet. Ethernet is a set of standards developed in the mid 1970s by Digital

Equipment, Intel, and Xerox. The standards included everything needed to get data

from one computer to another computer.

(1) The standard was released to the IEEE standards body, which named Ethernet the

IEEE 802.3 standard in 1980.

(2) Ethernet comes in three main flavors defined by cabling type: coaxial, unshielded

twisted pair, and fiber optic.

b) Token Ring. Developed in the 1980s by IBM. Has some limited use today, but

Ethernet has a far larger market share. Token Ring requires special equipment.

E. Coaxial Ethernet. Previously, Ethernet networks used coaxial (coax) cable. Coax consists of a

solid copper-core wire surrounded by an insulator. A shield of braided wire is wrapped around

the insulator. Another insulator is wrapped around the shielding. There are two different types

of coaxial cable used in networks: Thick Ethernet and Thin Ethernet.

3. Thick Ethernet—10Base5

a) Original Xerox Ethernet specification, also known as Thicknet. This coax cable called

RG-8 (Radio Grade) is about ½ inch in diameter.



b) The standard 10Base5 indicates a 10 Mbps transfer speed and a maximum segment

length of 500 meters. (All PCs attach to a single cable called a segment or bus. The

10Base5 standard supports up to 100 devices on each segment.)

(1) Bus topology. Thick Ethernet uses a bus topology or a physical layout that

consists of a single cable running to all PCs in the network, meaning they all

share the same bandwidth or transfer capacity as the wire.

(2) Ethernet uses carrier sense multiple access/collision detection (CSMA/CD). When

two cards talk (send packets at the same time), a collision occurs. This is also

called a contention-based network, which indicates collisions are possible.

(3) Reflection and termination. At each end of the segment, a 50-ohm terminator

must be used to prevent the signal from bouncing back or reflecting and

destroying the data. If a cable breaks, the network is no longer available and the

data transfer stops.

(4) Connections. Thicknet connections are marked every 2.5 meters showing where

to connect devices. Devices connect to Thicknet with a vampire connector

(actually a transceiver) that pierces the cable. Thicknet also requires an external

transceiver, often called an access unit interface (AUI)—a 15-pin DB connector

called an AUI port on the NIC.

(5) Disadvantages of Thicknet. It is expensive and difficult to work with. A single

break can bring down the entire network.

4. Thin Ethernet—10Base2

a) Also known as Thinnet or Cheapernet. It uses a thinner kind of Coax cable, the RG-58

cable (similar in size to the RG-6 used for cable TV).

b) Thin Ethernet also runs at 10 Mbps, but supports only 30 devices per segment. Each

segment can be a maximum of 185 meters long. (The “2” in 10Base2 originally meant

200 meters, but the actual length was reduced to only 185 meters.)

c) Each network card is connected to a bus cable with a T connector. Thinnet has twist-

on connectors, called BNC connectors, that attach to the T connector. Each end of the



network must have a terminator. Again, a break in the wire brings down the entire

network.

d) Thinnet is cheaper and easier to work with than Thicknet. Thinnet was popular for

small office/home office (SOHO) networks, but is rarely used with modern networks.

F. UTP Ethernet—10/100/1000BaseT

1. Modern Ethernet networks are likely to be 10BaseT, 100BaseT, or 1000BaseT. The “10”

stands for 10 Mbps, “100” for 100 Mbps, and “1000” for Gigabit Ethernet running at 1000

Mbps or 1 Gbps.

2. 10/100/1000BaseT networks use a star bus topology and connect via unshielded twisted

pair (UTP) cable.

3. Star bus. The 10BaseT network uses a star bus topology and unshielded twisted pair (UTP)

cable. Sometimes a switch, a far superior alternative, is used instead of a hub. This

topology looks like a star, but logically it acts like a bus because of the central hub or

switch that allows 4 to 32 devices to attach to it.

4. While the hub does not solve bandwidth problems, the switch does by making each port a

separate Ethernet network, and as a result, each network gets full bandwidth. A switch also

eliminates many collisions.

5. Another advantage of the star bus topology is that a single break in the wire does not bring

down the network. The central point of failure, the hub or the switch, will bring down the

network, but it rarely occurs.

6. Unshielded twisted pair (UTP) cables are rated by categories that fall under the

Telecommunication Industry Association/Electronics Industries Alliance (TIA/EIA).

Currently, most networks use CAT5e or CAT6 to take advantage of the faster transfer

speeds. These cables use an RJ-45 connector that is similar to but wider than the RJ-11

connector that phones use. The wires in UTP are numbered and color-coded.

Discussion Point

Building Cables

When building network cables, it is important to follow the 568 standards all the time. Even

though 10BaseT uses only two pairs of cables (you can actually omit the other two



pair), it is a good practice to build the cable the right way all the time. Doing this is

useful for two reasons: first, you will always be in the habit of making cables the right

way; and second, if the network upgrades to 100BaseT, you will not have to rebuild all

those cables.

Discussion Point

Crossover Cables

If you want to connect two computers, but do not have a hub, you can connect them directly

with a crossover cable. The crossover cable “crosses over” the transmission and

receiving wires to enable two computers to be directly connected. The crossover cable

will work only if connected to two NIC cards directly and will not work if connected to a

hub. A normal cable will not work when connecting two computers directly. You can

purchase a crossover cable, or you can build one

7. Implementing 10/100/1000BaseT network. This network can run on Cat3, Cat4, or Cat5

cable. Cables use an RJ-45 connector. RJ-11 is used for the telephone with two pairs of

wires (though most phones use only one pair). RJ-45 has four pairs of wires.

8. Combo cards. Some NICs are specifically for 10BaseT while others are for 100BaseT and

others for 1000BaseT. Some combo cards are 10/100 and are able to sense speed

automatically. These cards are referred to as autosensing cards.

9. Hubs and switches. Each PC connects to a hub or a switch with a 10/100/1000BaseT

network. The maximum distance from the hub to any device is 100 meters. Only one PC

may attach to each segment with a theoretical maximum of 1,024 devices attached to a

single hub. Most hubs have 24 or fewer ports. 10BaseT hubs are powered hubs that act as

repeaters, amplifying the signals between devices.

10. Duplex and half-duplex. All modern NICs can run in full-duplex mode; that is, they are

able to send and receive data at the same time. Some older devices ran in half-duplex

mode, meaning they were able to send or receive data, but not at the same time. However,

you will rarely find a half-duplex device today.

G. Fiber optic Ethernet



1. Uses light instead of electricity to send signals. Fiber optic cables are immune to

electromagnetic interference (EMI). The fiber optic signal travels much farther, up to 2000

meters with some standards. Most fiber optic Ethernet networks use 62.5/125 multimode

fiber optic cable.

2. Uses SC and ST connectors. Fiber connectors are half-duplex (data flows only one way),

so you need two cables.

3. Two common fiber optic standards are 10BaseFL and 100BaseFX.

4. Fiber optic cable is expensive and difficult to work with, so it is usually reserved for data

centers.

H. Token Ring. Developed by IBM, Token Ring networks use a combination of ring and star

topologies.

1. Ring topology. The ring topology connects all PCs together in a circle and uses a

transmission method called token passing. The token is an electronic packet that circulates

from one NIC to the other around the ring. A PC may transmit only when it has a free

token—that is, one that does not have data packets attached to it.

2. Implementing Token Ring. Older Token Ring ran at 4 Mbps or 16 Mbps, depending on the

equipment. Token Ring can use STP or UTP cabling. Like UTP, STP cables are also

divided into categories or types defined by IBM.

3. A Token Ring connector is a unique hermaphroditic connector called an IBM-type Data

Connector (IDC) or a Universal Data Connector (UDC). These cables are neither male nor

female and can plug into each other. Token Ring uses a multistation access unit (MSAU or

MAU) instead of a hub.

4. Token Ring can support up to 260 PCs using STP and up to 72 PCs using UTP. The

maximum distance from the MAU to the PC is 45 meters with UTP and 100 meters with

STP. A repeater can increase the functional distance between MAUs to 360 meters with

UTP and 720 meters with STP.

I. Parallel/serial. You can directly connect two computers using a crossover version of the IEEE

1284 cable for parallel and the RS-232 cable for serial.



J. FireWire. FireWire was designed to be network aware so plugging in two computers allows

them to recognize each other.

K. USB. You can also connect two computers with USB though it doesn’t work as easily as with

FireWire.

IT Technician

II. Network operating system (NOS)

A. A network operating system (NOS) communicates with the PC hardware and makes the

connections among multiple machines on a network.

B. The NOS enables one or more PCs to act as a server machine and share data and services over

a network. You then need to run software on client computers to enable those computers to

access the shared resources on the server machine.

C. Network organization. Networks are broken into three organizational groups: client/server,

peer-to-peer, and domain-based.

1. Client/server networks have a hierarchical design with at least one PC dedicated as a

server. All the other computers are called clients or workstations. Servers require special

network operating system software, such as Novell NetWare or Windows 2000 Server.

2. Peer-to-peer networks do not have dedicated servers. All computers connected to the

network can act as servers to the connected resources. Each computer controls access to its

resources. Peer-to-peer networks are very inexpensive but have are limitations. A peer-to-

peer network can connect not more than 10 or 15 PCs and is not too secure. All versions of

Windows include the capabilities to set up a peer-to-peer network.

3. Domain-based networks allow users to log on to the entire network at once, instead of one

server at a time as in the client/server model. A domain-based network has one or more

dedicated servers called domain controllers that contain the security database for all

systems.

a) Modern domain-based networks use a common database of information called a

directory service to store user and computer account information.

(1) Novell NetWare uses NetWare Directory Services (NDS).



(2) Windows 2000 and 2003 use Active Directory (AD).

b) Domain-based networks provide a central point of administration. Windows

NT/2000/XP sets up an administrator account automatically with absolute power over

the entire system.

Discussion Point

Administrator

All NOSs have a special account called Administrator. Some NOSs may have a different name

for that account, such as Root, but they all have one thing in common: they have

access to anything and everything on the network. These super accounts control the

entire network. Anyone who has access to this account can bring down an entire

network. If you have an account with this privilege, you must not disclose the password

to others. If you forget the password, you will need to reinstall the NOS completely.

D. Protocols

1. Each packet adds the sending and receiving MAC addresses to the data. This is how each

computer knows if a packet belongs to it or not. In addition to the MAC address, a unique

machine name is identified with the MAC address. This way, if a MAC address is changed

(NIC card replaced), the network still knows where to send the packets. Devices on the

network (all or some) maintain a list of all the MAC addresses and machine names on the

network.

2. A network protocol is a set of common rules that all devices on the network follow

regarding how computers are named and identified and how data is organized, sent, and

received.

3. To communicate, all devices on the network must use the same protocol, but there are

some main protocols in use.

a) NetBIOS Extended User Interface or NetBEUI (Microsoft). Relatively small and fast

and the default networking protocol for Windows systems. NetBEUI is self-

configuring, but it cannot be used for routing. Therefore, NetBEUI can be used only

on small peer-to-peer networks.



b) Internetwork Packet Exchange/Sequenced Packet Exchange or IPX/SPX (Novell).

Relatively small and fast, uses few resources, and works well with routers. While

IPX/SPX is used exclusively by NetWare, Microsoft implements a version called

NWLink.

c) Transmission Control Protocol/Internet Protocol or TCP/IP (UNIX/Internet).

Originally designed for the predecessor to the Internet, the Advanced Research

Projects Agency Network (ARPANET). TCP/IP then became the standard for UNIX

systems and for networks with more than 200 devices. (You can use TCP/IP on all

sized networks, even networks with two or three devices.) It is the standard for the

Internet. Although it is not as fast as other protocols and uses more RAM, TCP/IP is

more robust and universally supported.

d) AppleTalk (Apple). Similar to IPX, AppleTalk is a small and fast proprietary protocol

that Apple computers use to communicate. Except for small Macintosh-only networks,

it is rarely used anymore. Most Apple computers easily use Ethernet and TCP/IP to

connect to multiplatform networks using other protocols. Windows NT and 2000

provide native support for AppleTalk. Windows 9x can provide AppleTalk support

with third-party add-ons.

F. Client software. A PC must have client software to communicate with a server. Windows

installs Client for Microsoft Networks when you install a NIC and drivers. If you are using

NetWare, you need to add Client Service for NetWare.

G. Server software. By enabling sharing of files, folders, and printers, you can turn a

Windows PC into a server. To share your files, you need to enable Microsoft’s File and

Print Sharing

III. Installing and configuring a wired network

A. For network connectivity, you need three things:

1. Network interface card

2. Protocol

3. Network client



B. Installing a NIC first requires that you select a NIC appropriate to the specific media and

network type. With Windows 2000 or XP, all recent NICs install easily with plug and play by

using the Add Hardware Wizard. Other OSs may require special drivers from the NIC’s

manufacturer.

C. Configuring a network client. You need a client for each type of server NOS you connect to.

The two most commonly used network clients are Client for Microsoft Networks and Client

Service for NetWare.

D. Configuring simple protocols. To enable communication between two computers, they must

use the same protocol. If the computers are part of an existing network, the network

administrator will determine which protocol to use. Windows supports NetBEUI (except for

Windows XP), NWLink (IPX/SPX), and TCP/IP.

1. NetBEUI is easy to configure because it does not require network or logical addresses. In

Windows 2000, select Start | Settings | Network and Dial-up Connections. Double-click

the Local Area Connection Status icon in the Network and Dial-up Connections dialog

box. The Local Area Connection Status dialog box appears. You can now configure

NetBEUI.

2. NWLink (IPX/SPX) can be installed using the same steps as NetBEUI. You will need to

specify the internal network number and the frame type, but usually the default values

work fine.

E. Configuring TCIP/IP. TCP/IP is the primary protocol of modern networks and is required for

access to the Internet. This powerful protocol is a challenge to set up. The basic sections of

TCP/IP include the following:

1. Network addressing involves two pieces of information: the IP address identifies the PC,

and the subnet mask helps determine the subnet within the network where the machine

resides.

a) IP addresses. TCP/IP uses a dotted-decimal notation. It consists of four sets of binary

numbers (octets), each set separated by a period (dot). You will recognize the address

by its form: four sets of digits (numbered 0 to 255) separated by dots (i.e.,

207.46.230.229), otherwise called an IP address.



(1) Class A networks use the first octet to identify the network address and the

remaining three octets to identify the host. The address range will be from 1–126.

(2) Class B networks use the first two octets to identify the network address and the

last two to identify the host. The address range will be from 128–191.

(3) Class C networks use the first three octets to identify the network and the last to

identify the host. The address range will be from 192–223.

(4) The address 127.0.0.1 is reserved for network testing (loopback) operations.

(5) Certain ranges within each class are reserved for private networks that do not get

routed to the Internet. These ranges are 10.0.0.1 to 10.255.255.254 for Class A

and 172.16.0.1 to 172.16.255.254 for Class B. Class C has two ranges of private

addresses, 192.168.0.0 to 192.168.255.254 for manually configured addresses and

169.254.0.1 to 169.254.255.254 for the Automatic Private IP Addressing

(APIPA) function.

b) Subnet mask. Distinguishes which part of the IP address is the network address and

which part is the host address. Some subnet masks are defined by default. There are

three main classes of IP addresses: Class A (with a subnet mask of 255.0.0.0), Class B

(with a subnet mask of 255.255.0.0), and Class C (with a subnet mask of

255.255.255.0).

Discussion Point

Octets

The root of the word “octet” is “oct” meaning eight. Why is a three-digit number called an

octet? Because each octet is a representation of an 8-bit binary number consisting of

1s or 0s. Starting from the right, the first digit has a value of 1, the next digit to the left

has a value of 2, the next digit has a value of 4, and so on. Each number is double the

previous one. You merely add the values of the digits together for the octet number.

Value: 128 64 32 16 8 4 2 1

Binary: 0 1 0 0 1 1 1 0

Now add the value of each 1: 2 + 4 + 8 + 64 = 78



So, 01001110 equals 78. By converting each octet (1s and 0s) to its decimal form, you get a

recognizable IP number such as 207.46.230.229. By adding the values of the 1s and

0s, you can quickly see that if you have all 1s, you have 255 (128 + 64 + 32 + 16 + 8 +

4 + 2 + 1 = 255) and if you have all 0s, you have 0.

2. TCP/IP services. Another way of viewing TCP/IP is as a suite of protocols, instead of as a

single protocol. Services include the following:

a) Hypertext Transfer Protocol (HTTP), which allows the display of Web pages

b) File Transfer Protocol (FTP), which allows a computer to connect to a server to

upload or download files and others services

c) TCP/IP is able to link together hosts (computers), local area networks (LANs), and

wide area networks (WANs) by using routers.

3. TCP/IP settings. You must configure a number of TCP/IP settings for proper network

functioning. Windows 2000/XP unifies them under My Network Places properties.

a) The default gateway, usually a local router, is the device all computers on the network

use to contact the outside world—any place outside the LAN..

b) TCP/IP on the Internet requires a domain name service (DNS) to provide a database

of computer names and their corresponding IP addresses (www.microsoft.com equals

207.46.230.229).

(1) DNS provides name resolution for host names. Host names are a part of a fully

qualified domain name. For example, in www.microsoft.com, the host name is

www (the World Wide Web server) and www.microsoft.com is the fully qualified

domain name.

(2) Domain names are regulated. A top level domain (TLDs) identifies the basic

function of the organization. The first TLDs

included .com, .edu, .mil, .int, .org, .gov, and .net. There are also domain names

for countries, such as .uk for United Kingdom or .us for United States. Because of

the tremendous growth of the Internet, the Internet Corporation for Assigned

Names and Numbers (ICANN) has announced new domains,

including .name, .biz, and .info.


http://www.microsoft.com/



c) TCP/IP networks require Windows Internet Name Service (WINS) and dynamic host

configuration protocol (DHCP).

d) Windows Internet Naming Service (WINS). WINS is much like DNS, except WINS

maps Windows computer names (also known as NetBIOS names), instead of network

computer names (also known as host names), to an IP address. Many Windows 2000

and XP networks do not use WINS; instead, they use an improved “dynamic” DNS

that supports both Internet and Windows names. However, the death of WINS has

been greatly exaggerated. It still exists in many networks today to support applications

that rely on NetBIOS name resolution.

e) DHCP provides for automatic assigning of an IP address and other TCP/IP

configuration information such as a default gateway, subnet mask, DNS server, WINS

server, and more to a network computer.

(1) IP addresses may be assigned statically (manually by a tech) or dynamically via

DHCP.

(2) A DHCP server draws from a pool of IP addresses and assigns one to a PC

temporarily and then reassigns that IP address when it is no longer being used.

This is handy for laptops that only connect temporarily.

(3) Additionally, manually assigning all systems IP addresses can be very time

consuming and costly (in terms of manpower) for many networks. DHCP

automates the process.

4. TCP/IP tools. A wide variety of tools are available for diagnosing and maintaining the

TCP/IP network.

a) Ping. A small utility that sends out a small packet to a targeted addressed computer.

The packet is received by the target computer and sent back to the sending computer.

The time it takes is measured and reported. You can ping an IP address or a DNS

(207.46.230.229 or www.microsoft.com), and you can even ping yourself using a

loopback address (127.0.0.1). At a DOS prompt or command prompt, type ping /? to

find the correct usage.

Discussion Point



Ping

It is widely believed that Ping (an important network utility) is an acronym for Packet Internet

Groper. This is not so. According to the author of Ping, Mike Muuss (who died in a car

crash on November 21, 2000), he wrote the Ping program in 1983 to help track down a

network disconnect. The computer he was working on would send out a small packet,

and when it reached the destination, it would bounce back. He named it Ping because it

reminded him of the ping sound of a submarine’s sonar.

(Source: http://ftp.arl.mil/~mike/ping.html)

b) IPCONFIG (Windows 2000). Displays network information. You can use the /all

switch to see all of your TCP/IP settings.

c) NSLOOKUP. Enables you to determine the name of a DNS server and verify much of

the information on the DNS server. From a very basic perspective, you can enter

nslookup www.microsoft.com at a command prompt to get the IP address. Many

more sophisticated commands will determine a lot more information from the DNS

server.

d) TRACERT. Shows the route a packet takes to get to its destination

5. Configuring TCP/IP

a) By default, a DHCP server will automatically assign an IP address and subnet mask.

To configure TCP/IP in Windows XP, use the Network Connections applet. In

Windows 2000, use Network and Dial-up Connections to get to the network settings.

b) You will need to enter the IP address, the subnet mask, and the default gateway. You

may also enter the address of a primary and secondary DNS server.

6. Automatic Private IP Addressing (APIPA) is a feature that is available with Windows

2000 and Windows XP. It helps assign an IP address automatically to the system when the

client cannot obtain an IP address automatically. APIPA addresses are always in the range

of 169.254.0.1 to 169.254.255.254, with a subnet mask of 255.255.0.0 and with no other

TCP/IP settings entered. The network ID is 169.254.0.0.

F. Sharing and security



http://ftp.arl.mil/~mike/ping.html


1. Windows systems can share all kinds of resources including files, folders, drives, printers,

faxes, and Internet connections.

2. To share a drive or folder, right-click the drive or folder, click Properties, and then click

the Sharing tab. When you share a drive, you need to set a share name, without spaces.

Discussion Point

Share Names

Simply naming a shared drive with C is usually not a good idea because a network user could

confuse your C with someone else’s C. Give the drive a unique name. You can name it

for the person using that computer all the time (Dave), by content (MP3s), the desk

position (Desk4), or anything else, so long as network users can easily figure out what

drive it is.

a) You then need to determine the permissions. Windows 2000/XP provides for two sets

of permissions: Network permissions and NTFS permissions. Network permissions

offer Full Control, Change, and Read settings. If you are on NTFS and want to control

the permissions even further, you need to configure the NTFS permissions in addition

to the network permissions.

b) Once you share the drive, a small hand appears on the icon.

3. To access shared drives/directories, you have a few choices.

a) You can browse to them through My Network Places (though this involves a lot of

clicking).

b) You can map a network drive to your system. This means the network drive shows up

in My Computer as a drive. The icon will look different, and it will have a letter, but

the letter is not part of the network drive.

c) Universal naming convention (UNC). All computers have a name, and all shared

resources have a name. The UNC name uses the computer name and the share name

as \\serverName\shareName. All files and folders have a pathname. For example,

C:\FREDC\INSTALL-FILES\SETUP.EXE



All network drives and their shared resources also have a pathname beginning with

double backslashes, the server name, a single backslash, the share name, and the rest

of the path. For example,

\\SERVER\FREDC\INSTALL-FILES\SETUP.EXE

4. Sharing printers

a) Sharing a printer is similar to sharing a drive. Right-click the printer, select Properties,

and then Sharing. Select Share As and give the printer a name.

b) To access a shared printer, install a network printer on a workstation. Use the Add

Printer Wizard and select Network Printer when prompted. Browse to the network

printer using the UNC. Usually, setup will just copy the printer drivers from the

network computer. If not, it will prompt you for the driver disk.

Essentials

IV. Installing and configuring a wireless network

A. Wireless networks are growing in popularity. Instead of cables, wireless networks use either

radio waves or beams of infrared light to communicate with each other.

B. Wireless networking components

1. Infrared transceiver ports have been around on portable PCs, PDAs, and high-end printers

for years.

2. Wireless networking adapters can be Ethernet or Bluetooth. They can be PCs or handheld

computers or PDAs.

3. Wireless Ethernet networks use a wireless access point (WAP) to connect wireless network

nodes. They can also connect to a wired network or a high-speed Internet connection.

IT Technician

C. Wireless networking software

1. Wireless devices use CSMA/CA. The CA stands for collision avoidance. The wireless

node listens to make sure no other node is communicating. If a node is communicating, it

waits for a random amount of time and tries again. By using the Request to Send/Clear to



Send (RTS/CTS) protocol, it avoids collisions, but it adds significant overhead to the

process and can impede performance.

2. Wireless adapters are plug and play and may be installed in a PCI, PCMCIA slot, or a

USB port. You will need a utility to set parameters such as the Service Set Identifier

(SSID), also called a network name. Windows XP has built-in tools for configuring these,

but if you are using any other Windows versions, you will need to use the tools provided

by the wireless network adapter vendor.

D. Wireless networks work in two different modes: Ad-hoc mode and infrastructure mode.

1. Ad-hoc mode, also called peer-to-peer mode, allows each wireless node to have direct

contact with each other node. When two or more nodes communicate in an ad-hoc manner,

it is called an Independent Basic Service Set (IBSS). Limited to less than a dozen

computers, this mode is good for temporary networks.

2. Infrastructure mode involves one or more WAPs that connect the wireless network nodes

to a wired network segment. A single WAP that provides services to a specific area is

called a Basic Service Set (BSS), and when the service is extended using two or more

WAPS, it is called an Extended Basic Service Set (EBSS). Infrastructure mode is better

suited for business networks because it enables the wireless node to access the wired

network.

E. Wireless networking security has been a serious concern. To secure access to the network and

its data, wireless networks use three methods, though all of these are beatable with off-the-shelf

software.

1. SSID. Although wireless nodes and access points may be assigned a default SSID name,

this still makes them vulnerable. It is better to configure a unique SSID name. The SSID

name is included in the packet header, and if the SSID name is not correct, the packets will

be discarded. Turning off SSID broadcasting makes it harder for people to determine your

SSID name.

2. MAC filtering lets you limit access to your wireless network based on the MAC address or

the physical address of the wireless NIC.

3. WEP encryption uses a 40-bit encryption to scramble data packets. Some use 104-bit

encryption and a few even advertise 128-bit encryption. Note, however, that WEP does not



provide end-to-end encryption because it works at only the two lowest layers of the OSI

model, the Data Link and the Physical layers. The encryption is stripped from the data as it

travels up the subsequent network layers.

4. WPA (Wi-Fi Protected Access) is more secure than WEP. It uses the encryption key

integrity-checking feature and user authentication through the Extensible Authentication

Protocol (EAP). Even this technique, however, is not a complete security solution. WPA

was considered an interim security solution until the IEEE 802.11i was formulated.

5. WPA2. Also known as IEEE 802.11i, WPA2 is an improvement over WPA. It uses

Advanced Encryption Standard (AES) and other security features to protect data

transmission.

F. Speed and range issues

1. Depending on the wireless standard used, throughput speeds range from 2 Mbps to 54

Mbps. Speed decreases as distance between the wireless nodes and centralized access

points increases. Other wireless devices may interfere, blocking the signal or interfering

with it. Best speed is achieved with a limited range of 25 feet or less.

2. Under ideal circumstances, wireless networks range from about 150 feet to 300 feet.

G. Wireless networking standards

1. The IEEE 802.11 standard defines wireless Ethernet using spread-spectrum radio waves.

This technique broadcasts in discrete chunks over different frequencies within a certain

frequency range.

2. All 802.11-based wireless technologies can broadcast and receive data at 2.4 GHz (except

for 802.11a that uses 5 GHz.) The original 802.11 standard has been extended to include

three variations.

a) 802.11a was developed after 802.11b. It offers speeds up to 54 Mbps with a top range

of about 150 feet. It uses the 5-GHz range and is different from other 802.11-based

standards. Although it is faster than 802.11b, it has not been widely used.

b) 802.11b is the most widely used. It supports data throughput up to 11 Mbps with a

range of 300 feet. 802.11b can be secured using WEP and WPA encryption. Its 2.4-

GHz frequency is already crowded and other wireless devices interfere with it.



c) 802.11g is the newest standard that offers transfer speeds up to 54 Mbps with a 300-

feet range. It is backward-compatible with 802.11b and also uses the 2.4-GHz range.

3. Infrared wireless networking is an easy way to transfer data, but it is slow. Using the

Infrared Data Association (IrDA) protocol, data is transferred at 4 Mbps for a maximum

distance of 1 meter. It requires direct line of sight. IrDA devices communicate in half-

duplex mode, and it offers no encryption or authentication.

4. Bluetooth. Designed to create small wireless personalized area networks (PAN) that link

PCs to peripheral devices, such as PDAs and printers, and input devices, such as keyboards

and mice.

a) Poised to replace infrared as a means to connect PCs to peripherals. Not meant to be a

full-functioning network or compete with Wi-Fi

b) Uses the FHSS spread-spectrum broadcast method and 79 frequencies available in the

2.45-GHZ range

c) Transfers data between 723 Kbps to 1 Mbps. High-powered Bluetooth devices can

reach 2 Mpbs and a maximum range of up to 300 feet.

d) Maximum range of 10 meters

e) Hardware is integrated into the devices and requires very little setup.

f) Can be networked using access points to bridge the LAN segments with the Bluetooth

PAN segments

5. Cellular. Enable you to connect to the Internet through a network-aware PDOA or cell

phone. By adding PC cards, you can connect any laptop to a cellular network.

H. Configuring wireless networking is similar to setting up a wired network.

1. Install the wireless adapter, and let PnP handle the resource allocation. Windows XP

includes a wireless configuration utility, while the previous versions of Windows do not,

so you will need to use the utility that comes with the adapter.

2. When configuring wireless devices, ensure that only specific wireless nodes use it and

secure the data being sent through the air.

3. Wi-Fi supports ad-hoc and infrastructure mode.



a) Ad-hoc mode does not need WAP. Instead each wireless node is configured using the

same network name (SSID) but a unique IP address.

b) Infrastructure mode connects one or more wireless network WAPs to a wired network

segment. All nodes and WAPs must use the same SSID, and the feature that

broadcasts the SSID should be disabled. By enabling MAC filtering and turning on

encryption, you can make it even more secure.

4. Wireless networking security

a) SSID. All nodes and WAPs must use the same SSID. Several systems ship with

default SSIDS; these should always be changed. The SSID is automatically broadcast,

allowing any wireless NIC to identify the name of the SSID; disable this feature.

However, the SSID is still included in each packet, so if packets are captured, the

SSID can be discovered.

b) MAC address filtering. By enabling MAC filtering, you can limit access to computers

that can connect. However, because the MAC addresses are included in each packet,

the MAC address can be discovered, and packets altered to impersonate the authorized

MAC.

c) Encryption. By enabling encryption, you have a better chance of stopping intruders,

however…

(1) WEP. Initial attempt at wireless encryption with significant security flaws

(2) WPA. Interim measure as WPA2 (802.11i) was being developed

(3) WPA2. Significant improvements and strongly recommended as an upgrade to

WPA

5. Although infrared is fully supported in the latest versions of Windows, it offers limited

choices for networking. It is designed to connect only two systems in an ad-hoc mode for

simple file transfer.

a) Infrared can also be used as direct-connection mode (similar to a crossover cable) to

allow an Ethernet LAN access using IrDA. IrDA requires line of sight. An infrared

access point combines an infrared transceiver with an Ethernet NIC to translate the

IrDA protocol into an Ethernet signal.



b) Transferring files via infrared. Once connected, simply point and shoot.

c) Networking via infrared. Similar to using a null-modem cable to connect two

computers via the serial port. Devices set up to use this feature typically have a

wizard.

d) Bluetooth configuration is completely plug and play. If required, install the drivers.

(1) Bluetooth devices automatically seek other Bluetooth devices and establish a

master/slave relationship without any intervention.

(2) Bluetooth vendors have specialized software that can be used to connect between

Bluetooth PANs.

IV. Troubleshooting networks

A. Networks add an additional layer of complexity with their network hardware and resource

sharing. Compare a problem of not being able to print with a non-networked PC.

1. Non-networked situation

a) Printer not connected

b) Printer out of ink

c) Doesn’t have the proper driver loaded

d) PC using different printer

2. Networked situation. All the previous possible problems, plus the following:

a) Print server is down.

b) Printer is locked by another user.

c) Client PC doesn’t have network connectivity.

d) NIC driver is bad.

e) Client PC doesn’t have print drivers for networked printer.

f) One of the network cables is bad.

g) Port is bad.

h) Switch or hub failed.



B. Some steps to take when troubleshooting a PC or a network include the following:

1. Verify the symptoms.

2. Check when it happened.

3. Check what has changed.

4. Check the environment.

5. Reproduce the problem.

6. Isolate the symptom.

7. Separate hardware from software.

a) Replace suspected hardware with known good hardware.

b) Uninstall/reinstall.

c) Download patches and upgrade drivers.

d) Check for viruses and keep the antivirus up-to-date.

8. Research the problem. (Hint: Type the error into a search engine and you may get an

automatic fix.)

9. Make the fix and test. Before you fix a problem, create a backup or warn the user about

any risks. After you fix it, test the system to check whether or not it is working properly.

C. OSI seven-layer model. The OSI model is intended as a model or guideline to help technicians

isolate problems.

There a couple of popular mnemonics to help people remember the seven layers of the OSI

model. Please Do Not Throw the Sausage Pizza Away is one that starts at Layer 1 and

goes to Layer 7. All People Seem To Need Data Processing is another that starts at

Layer 7 and goes to Layer 1.

1. Layer 1, Physical. Defines format of data on the cable and through devises such as NICs

(link light), hubs, and switches. Ones and zeroes used here.

2. Layer 2, Data Link. Defines rules for accessing and using the Physical layer. MAC

addresses and CSMA/CD operate here.



3. Layer 3, Network. Defines rules for adding information to the data packet. The IP protocol

works here.

4. Layer 4, Transport. Breaks up data into smaller pieces. TCP and UDP protocols operate

here.

5. Layer 5, Session. Manages connections between machines

6. Layer 6, Presentation. Presents data in format the receiving system can understand and

often done with same software-handling Layer 7 functions

7. Layer 7, Application. This is the layer where the user interacts with the system.

D. Mike’s Four-Layer Model defines four categories to help isolate symptoms and make the right

fix:

1. Hardware. Make sure the hardware is connected and operating correctly.

2. Protocols. Make sure protocols are installed and configured correctly.

3. Network. Look at both servers and clients and try to determine which is causing the

problem.

4. Shared resources. Resources need to be shared to be accessible over the network.

Permissions need to be set to allow access.


Chapter 21 Fall 2007... · Web viewMost fiber optic Ethernet networks use 62.5/125 multimode fiber...

Documents

Transcript of Chapter 21 Fall 2007... · Web viewMost fiber optic Ethernet networks use 62.5/125 multimode fiber...