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Chapter 7 *

Basic Networking *

Certification Objectives *

Basic Networking Concepts *

Cabling *

Twisted Pair *

Coaxial *

Fiber Optic *

Cable Type *

Other Required Devices *

Network Interface Cards *

Network Access *

Carrier Sense Multiple Access/Collision Detection *

Token Passing *

Protocols *

TCP/IP *

IPX/SPX *

NetBEUI *

Ways to Network a PC *

Configuring Network Interface Cards *

Problems on the Network *

Reduced Bandwidth *

From the Field *

A Real-World Networking Lesson *

Loss of Data *

Network Slowdown *

Certification Summary *

Two-Minute Drill *

 

Chapter 7

Basic Networking

Certification Objectives

Basic Networking Concepts
Configuring Network Interface Cards
Problems on the Network

Networking is by far one of the most quickly expanding fields in the computer industry. With the surge in popularity of the Internet in the mid 1990’s, a great deal of interest in networking has arisen. Whenever two or more workstations are connected together, a Local Area Network (LAN) is created. Nearly every major company has, at a minimum, a LAN installed.

There are some basic networking concepts that you will run into time and time again as a technician. Whether you have an interest in networking or not, it will be in your best interest to be familiar with these basic concepts.

After you have a firm grasp of some basic networking concepts, it is also important to have a general understanding of how to configure a Network Interface Card (NIC). Configuration of a NIC is extraordinarily simple in most cases, and will be useful to you during your career.

Basic Networking Concepts

As a base for your networking abilities, you need to understand some basic networking concepts. Everything in the world of networking revolves around these concepts, and a firm grasp of them is extraordinarily important. These basic concepts include:

Cabling
Network Interface Cards
Full Duplex
Network Access
Protocols

Cabling

Obviously, in order to create a network, you have to somehow physically connect the devices that will be on the network. This is accomplished using cables. There are many different types of cables, each having it’s own advantages and disadvantages. In the next few sections, we discuss three types of cabling: Twisted Pair, Coaxial, and Fiber Optic.

Twisted Pair

Twisted pair is by far the most common type of network cable, primarily because of its low cost. Physically, twisted pair consists of pairs of wires, usually four. Each of the wires in a pair is wrapped around the other to help avoid interference. Twisted pair requires that each workstation be attached to a hub (see Figure 7-1). A hub receives data from one of its ports, and then transmits it to all of its ports. Twisted pair cable is considerably less expensive than the other types of cabling. In larger network installations, the lower price of cable offsets the cost of a hub and makes twisted pair the most cost-effective networking solution.

Fig10-1.tif (257723 bytes)

Figure 7-1: A hub is a device to which each device on a network connects

Twisted pair can be referred to by many different names. Some of these names include unshielded twisted pair, UTP, shielded twisted pair, 10BaseT, or 100BastT; UTP is the most popular. As shown in Figure 7-2, twisted pair is configured in a star topology, in which each device is connected to a central device, usually a hub. In the event of a cable being cut or broken, the device that is connected to that cable will no longer be able to communicate on the network, but will not effect any other devices on the network.

 

 

 

 

 

 

 

Figure 7-2: A twisted pair network is usually configured in a star topology

Coaxial

Coaxial, while not as common as twisted pair, is also a popular type of network cable. Physically, coaxial cable consists of a central wire that is surrounded by a screen of fine wires. Coaxial cable is most common in smaller networks, where it is cheaper to purchase the coaxial cable instead of purchasing both the UTP cabling and hubs. Like twisted pair, coaxial can also be referred to by many names. Some of these names include BNC, ThinNet, and 10Base2; ThinNet is the most popular. Each device must be connected to a T-connector, shown in Figure 7-3. Each T-connector is connected to the next with a coaxial cable. After all of the devices are connected, the ends of the cable must then be terminated with a 50W terminator. As shown in Figure 7-4, a coaxial network is configured in a bus topology. In the event of the cable being cut or broken, the network will cease to operate.

Fig8-2.tif (118447 bytes)

Figure 7-3: A T-connector is required between each device on a network utilizing coaxial cabling and the coaxial cable

EXAM WATCH: Coaxial cable requires that each device be connected to a T-connector, which is then connected to the coaxial cable. In addition, each end of the cable must have a 50W terminator installed

 

Figure 7-4: A coaxial network is usually configured in a bus topology with each device connected to a main cable or bus

Fiber Optic

Fiber optic is by far the least common of the three types of cabling. Fiber optic cabling is usually found where long cable lengths are required, where extremely high speed is desired (at extremely high cost), or where there is high EMI radiation or other environmental difficulties. Traditional copper-based cables such as twisted pair or coaxial cables are very susceptible to radiation and other environmental difficulties. Fiber optic cable is much less susceptible to these environmental difficulties because it uses light signals rather than electrical signals. Light signals offer much more protection from environmental interferences than electrical signals. Fiber optic is used when long lengths of cable are required because it is able to sustain longer distances without environmental interruption.

Fiber optic is usually referred to simply as fiber. Each segment of fiber optic cable must be connected at each end with a special fiber optic connector. As shown in Figure 7-5, a fiber optic network is configured in a ring topology. In the event that the fiber optic cable is cut or broken, the network will cease to operate. (Most fiber optic installations actually include two rings in order to provide redundancy and fault tolerance.) Table 7-1 lists and compares each of the cable types discussed in this section.

 

 

 

 

 

 

 

Figure 7-5: A fiber optic network is usually configured in a ring topology where a token is passed around a ring

Cable Type

Topology Maximum Distance Transmission Speed

Other Required Devices

Twisted Pair Star 100 Meters 10 or 100 Megabits per second Each networked device must connect to a port on a hub.
Coaxial Bus 180 Meters 10 Megabits per second Each networked device must be connected with a T-Connector and terminators must be connected to each end.
Fiber Optic Ring Theoretically no limit Theoretically no limit (100 Megabits per second most common) Each end of a cable segment must have a special fiber optic transmitter connected.

 

 

 

 

 

 

 

 

 

 

 

 

Table 1: Comparison of Important Characteristics of Cable Types

EXAM WATCH: Twisted pair cable is capable of transmitting a maximum of 100 meters, coaxial is capable of a maximum of 180 meters, and fiber optic cable theoretically has no limit

Network Interface Cards

Network interface cards (NICs) are the devices that, when installed in a PC, connect the PC to the network cable. NICs must be matched to the type of network and the type of network cable that you are using. It is important to choose a NIC that corresponds to your network. Recently, most NIC manufacturers have introduced models that can connect to either twisted pair or coaxial networks.

Full Duplex

Networking is described as full duplex when it is capable of transmitting in both directions at the same time. In simpler terms, a full duplex network medium has the capability of sending and receiving simultaneously. The most common application of true full duplex networking is in fiber optic cabling.

Network Access

Network access (or access methods as it is more commonly referred to) is the method by which devices communicate on the network. Without some type of control on the network, any device could transmit at any time, quite possibly at the same time as another device. As we humans have a problem when two people attempt to communicate simultaneously, devices on the network have a similar problem. Network access provides a standard that all devices that wish to communicate on the network must abide by in order to solve this problem. Common types of network access are:

Carrier Sense Multiple Access/Collision Detection
Token Passing

Carrier Sense Multiple Access/Collision Detection

Carrier Sense Multiple Access/Collision Detection (CSMA/CD) is somewhat similar to how we humans communicate. With CSMA/CD, a device transmits data onto the network. The device then detects if any other devices have transmitted onto the network at the same time. If it detects that another device has transmitted data onto the network, the device then waits an unspecified random amount of time and retransmits its data. CSMA/CD is most commonly found on Ethernet networks, which most commonly use twisted pair or coaxial cable as the physical cable type. CSMA/CD is one of the faster access methods available, but performance can become an issue on busier networks.

Token Passing

Token passing is a bit more organized than CSMA/CD. Using token passing, a token is passed from device to device around a virtual (and frequently physical) ring. Whenever a device receives the token, it is then allowed to transmit onto the network. Token passing is most commonly found on fiber optic and token ring (which we will not discuss because it is becoming less commonly used) networks. Token passing, although more organized than other methods, is a bit slower because it requires that devices wait until they hold the token prior to transmitting onto the network. In the event that the token were to be lost, the network could be rendered useless until a new token is created, which could take from a few seconds to a few hours. The use of token passing is advantageous where total organization is required, such as in fiber optic backbones.

Protocols

Data cannot simply be transmitted onto the network. Protocols establish standards for such transmission of data. Both the sending and receiving device must be capable of communicating using the same protocols. Some common protocols are:

TCP/IP
IPX/SPX
NetBEUI

TCP/IP

TCP/IP, Transmission Control Protocol/Internet Protocol, is the most common protocol used today; it’s the protocol upon which the Internet is built. TCP/IP was originally designed in the 1970's to be used by the Defense Advanced Research Projects Agency (DARPA) and the Department of Defense (DOD) to connect systems across the country. A requirement of this design was for the ability to cope with bad network conditions. An advantage of TCP/IP is that it is routable or can be passed beyond a router. A router is a network device that connects two or more networks together. The router that all traffic it allows to cross is destined for the network on the other side of the network prior to allowing it to cross. TCP/IP’s largest disadvantage is that it requires quite a bit of configuration prior to use.

IPX/SPX

IPX/SPX, Internetwork Packet Exchange/Sequenced Packet Exchange, is the protocol most commonly used with Novell Netware. IPX/SPX is a very fast and highly established protocol, but is not used on the Internet. Novell developed IPX/SPX for use in Netware. Like TCP/IP, IPX/SPX is routable and requires some configuration, though nowhere near as much as TCP/IP.

NetBEUI

NetBEUI, NetBios Extended User Interface, is a transport protocol that is commonly found in smaller networks. NetBEUI is an extremely quick protocol with very little overhead that was first implemented with LAN Manager products. NetBEUI is not routable and requires little configuration, if any at all.

Ways to Network a PC

So far, all of our discussion has involved using a NIC to connect two or more computers together. There are a few other ways to network workstations.

Dial-Up Networking is when a modem is used to connect two or more workstations together. The majority of people who connect to the Internet from home use Dial-Up Networking on a daily basis. It is considerably slower than using NICs, but can accomplish the same tasks.

A direct cable connection is when two computers are networked using either a serial or parallel cable. Direct cable connections are considerably faster than modem connections, but are still slower than networking using a NIC. Direct cable connections are limited to networking a maximum of two computers and are limited by physical cable restrictions.

Configuring Network Interface Cards

Network Interface Cards (NICs) are fairly simple to configure. Most NICs require an IRQ and an IO memory address. Once the resources that the NIC uses have been configured on the NIC (most newer NICs use a software utility rather than the more traditional jumpers or dip switches; consult your NIC’s documentation for exact specifications), the Network Operating System must be configured with the same settings (Consult your Network Operating Systems documentation for details, and see Chapter 11 of this book). Configuration will be a less difficult process if the same type of NIC is used in each workstation on your network.

Problems on the Network

As the saying goes, all good things must come to an end. Someday your beautiful network will not continue to operate exactly as it used to. This could be the result of many different things. Some common causes of network problems include:

Physically damaged cable
Damaged Network Interface Card
Excessive traffic on the network
Incorrectly operating hub
Missing or incorrectly operating terminator
Magnetic fields
Incorrectly configured network devices

Reduced Bandwidth

Reduced bandwidth occurs when users’ data transmissions across the network begin to take longer, and begin to be timed-out by the applications requesting the transmission. Reduced bandwidth can be caused any of the common network problems mentioned in the preceding section. The most likely cause of reduced bandwidth is excessive traffic on the network. Excessive traffic usually is not a result of an equipment failure, but instead a result of equipment success. The only solution to excessive traffic is to modify the network configuration in order to allow more traffic, or to separate high-traffic users from others. The most common method of modifying the network configuration to allow more traffic is to upgrade a 10 Megabits/Second LAN to 100 Megabits/Second by replacing hubs, NICs, and possibly the cabling.

From the Field

A Real-World Networking Lesson

It is very important to understand the limitations of the networks on which you work. Bandwidth costs money, and some corporations try to run their networks on the minimum amount of bandwidth. Once, I was swapping a computer with another computer for a user and I needed to transfer the user’s data to the new computer. Being naïve, I copied all the user data onto a network drive to copy back to the new computer. Because I assumed the network could handle this procedure, I did not ask anyone about bandwidth or server drive size. Well, guess what? My copying took over 25 percent of the network bandwidth and sent all sorts of server alerts to the administrators. Not only was the bandwidth a problem, the network drive I was copying to became totally full. Luckily, everything worked out okay. I deleted the copied data and the network only slowed down a bit rather than coming to a screeching halt. Always find out the capabilities and limitations of a network before doing any kind of work on it. By the way, I copied the data over by slaving the drives after that and it worked well.

From this example, even if you are on a network that can handle this, you must ask yourself a few questions before doing anything that might strain the network. Are there other people on the network doing something similar to what you want to do? If so, will the combined effect of your collective actions cause network problems? Are there people working on the network who might be slowing things down to a level that would be aggravated worse by your actions? Is there another way to do what you are trying to do without using the network? I’ve seen many techs carry around a portable hard drive with them all day to do data transfers and software installs. Not only are they saving valuable network bandwidth, but they are probably getting their data sent faster. In addition, they can carry all the drivers and repair software on this drive.

By Ted Hamilton, MCP, A+ Certified

Loss of Data

Loss of data can be a result of nearly any of the common network problems mentioned previously. Most methods of data transmission provide some type of assurance that the data has been transmitted successfully. Data loss is therefore usually caused by some type of failure, and not by excessive traffic. Excessive traffic results in slower delivery of data rather than loss of data in most cases.

Network Slowdown

Network slowdown occurs whenever users notice that the network is not operating as quickly as they are used to. In most cases, this is a sudden change, rather than a gradual change (a more gradual change would be a loss of bandwidth). Because the change appears to be sudden, it is more than likely a result of a hardware problem, rather than a result of excessive traffic.

Certification Summary

This chapter has offered you a general understanding of basic networking concepts, including the various methods by which networks operate and an overview of some of the more common networking problems. A firm grasp of networking fundamentals is becoming an increasing necessity in today’s growing network-oriented computer industry.

As you have learned, Local Area Networks (LANs) are most commonly created by connecting workstations that have Network Interface Cards (NICs). These workstations are usually connected using either twisted pair, coaxial, or fiber optic cabling. Communication on the network cable is governed by network access methods such as Carrier Sense Multiple Access/Collision Detection (CSMA/CD) or Token Passing.

Common network problems can be caused by a number of factors, including physically damaged cable, damaged NICs, excessive traffic on the network, an incorrectly operating hub, missing or incorrectly operating terminator, or magnetic fields. Results of some of these causes can include reduced bandwidth, loss of data, or network slowdown.

Two-Minute Drill

A Network Interface Card is more commonly known by its acronym, NIC.
Basic networking concepts include cabling, NICs, network access, and protocols.
Common cabling types include twisted pair, coaxial, and fiber optic.
Twisted pair cable is organized in a star topology, and requires that each network device be connected to a port on a hub.
Coaxial cable is organized in a bus topology, whereby each device is connected to a T-connector that is then connected to the cable that has a 50W terminator connected to each end.
Fiber optic cable is organized in a ring topology, and requires that each end of the cable be connected to a special fiber optic connector.
Twisted pair cable is capable of transmitting a maximum of 100 meters, coaxial is capable of a maximum of 180 meters, and fiber optic cable theoretically has no limit.
NICs are the devices that connect a PC to the network cable. NICs must be matched to the type of network cable that you are using.
Network access defines the methods by which devices can communicate across the network.
Some common network access methods include Carrier Sense Multiple Access/Collision Detection (CSMA/CD), which is commonly used with twisted pair and coaxial cable, and token passing, which is commonly used with fiber optic.
CSMA/CD is an access method by which a device transmits data onto the network and then detects if any other devices have transmitted onto the network at the same time.
Token passing is an access method by which a token is passed from device to device around a virtual ring, and the device can only transmit data when it receives a token.
Protocols, which ensure that both the receiver and the sender can understand the data that is sent, are used to define how devices communicate with each other.
Some common protocols include Transmission Control Protocol/Internet Protocol (TCP/IP), Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX), and NetBios Extended User Interface (NetBEUI).
Most Network Interface Cards require an IRQ address and an IO Memory address in order to operate correctly.
Common network problems can be caused by a physically damaged cable, a damaged NIC, excessive traffic on the network, an incorrectly operating hub, a missing or incorrectly operating terminator, or magnetic fields.
Common results of network problems can include reduced bandwidth, loss of data, or network slowdown.