Chapter 1: Down to the Networking Basics

Exam Objectives

Identifying network types

Understanding network topologies

Working with network cables

Becoming familiar with network architectures

Accessing the network

Installing a Small Office/Home Office (SOHO) Network

The A+ Certification exams cover two areas of networking: networking theory/networking hardware and networking at the operating system (OS) level. This chapter focuses on the networking theory and the networking hardware area of the A+ exams. For the exam, you are required to know popular terms and features of networking environments that you will encounter on the exams and in the real world — which is what this chapter will help you with. Networking at the OS level is covered in Chapter 3 of this minibook.

Identifying the Types of Networks

A network is a group of connected systems for sharing data or devices. This section provides an overview of the two major types of networks: peer-to-peer and server-based (client-server). I discuss the advantages and disadvantages of each type as well as how to implement them.

Peer-to-peer networks

In a peer-to-peer (P2P) network, all systems connected to the network can act as clients or servers. A client is a system that makes a request for a resource or service on the network; a server is the system providing the resource or service. In this type of networking environment, all systems are considered equal because they can all play the same roles on the ­network — either as client or server or as both client and server. The ­recommended number of systems in a P2P network usually involves ten or fewer systems because of the lack of centralized administration. As a network administrator working in a P2P environment, you will constantly run from machine to machine to perform administrative tasks. Typically, a P2P network involves each system running a desktop operating system, such as Windows XP, to provide network functionality (see Figure 1-1).

In Figure 1-1, notice that client A provides a network resource — a printer — as does client D. This shows that client A is acting as both a server and a client, which is the purpose of a P2P network.

Because a central machine doesn’t store files in a P2P network, your networking environment isn’t based on the centralized administration approach. With centralized administration, you (as network administrator) could perform network administration tasks for the entire network from one place. Looking back to Figure 1-1, you can see that because all four computers act as peer servers (meaning they all act as servers to one another), you need to do the administration on all four computers — a major disadvantage of P2P networking.

Some examples of the administration you must perform on each system are creating user accounts on each computer and managing file and folder sharing from each system. In Figure 1-1, for example, if you want Bob to log on to client A, you would create the Bob account on client A. At the same time, if you want Sue to log on to client B, you would create the Sue account on client B. Because the Bob account doesn’t exist on client B, Bob can’t log on to that computer even though he might be able to access the files on client B from client A. This leads to a distributed administration model because your work is spread across multiple machines.

The major advantage of P2P networking is that you save money by not needing to purchase a central server, which can cost thousands of dollars in hardware and software. Too, with a P2P network, you also don’t have to purchase a separate network operating system (NOS). A NOS, required on a server-based network (discussed in the next section), is designed for networking services (such as Dynamic Host Configuration Protocol [DHCP], Web, file, and print services) and allows the server to share its files and printers with clients on the network. The cost of the NOS, and the licenses to have clients connect to the server, is where a number of large companies spend most of their IT budget. Licensing is expensive!

Server-based (client-server) networks

Server-based networking, also known as client-server networking, is the networking model that most companies usually choose for ten or more workstations on a network. Unlike a P2P network, server-based networking uses a central machine (the server) that delivers network services to the workstations. Once again, these network services could be services such as file and print sharing, user account authentication, or Web services.

The benefit of a client-server configuration is that you can leverage centralized administration by performing the bulk of your work on the one server. For example, if you need to create user accounts for each of the ten users, you create the ten accounts on the one server. Compare that with a P2P network, where one account is created on each system. As the administrator of this network, you create all shared directories on the server along with user accounts so that the server may verify the credentials of a client who attempts to log on to the network. All users on the network connect to this server to save and retrieve files.

Tighter security is another benefit of using a server-based networking model. Creating a more secure environment is easier with a server-based network because your resources and user accounts are not spread across multiple machines. Looking at Figure 1-2, you can focus on the server because it contains the files, folders, and user accounts. When a user logs on to the network, the logon request is sent to the server, which verifies that the username and password are valid. After a user is logged on, the server allows the user access to resources, such as files and printers, that the user has permission to use. Figure 1-2 illustrates a server-based networking environment.

Notice in Figure 1-2 that the client systems connect to the server to access the printer. In this environment, all systems have a defined role: They are either a client or a server — but not both.

The disadvantage of using a server-based environment is the cost of purchasing the server hardware and the NOS. When designing your networking model, make sure that you work with someone familiar with software licensing so you get the best bang for your buck!

Additional networking terminology

Another set of terms you will hear when talking with other IT professionals about network concepts is local area network (LAN) and wide area network (WAN). The following outlines common networking terms you should understand when preparing for the A+ certification exams:

LAN: A local area network (LAN) is a network that typically involves one office building, or maybe even networked systems on one floor. The major point to remember when identifying a LAN is that there is not a lot of distance between the systems on the network.

WAN: Comparatively, a wide area network (WAN) is a network environment that involves connecting two or more LANs. Each LAN typically covers its own building or office location. Companies typically link each office location to network with the other office locations. Connecting all office locations creates the WAN.

MAN: A metropolitan-area network (MAN) is a network bigger than a LAN but not as big as a WAN environment. The MAN covers a small metropolitan area, while a WAN could cover areas across the country or the world.

PAN: A personal-area network (PAN) is a network created by smaller personal devices typically using Bluetooth.

Understanding Network Topologies

When building a network, be cognizant of some upfront decisions regarding the overall network setup. Building a network is like building a database: You have to understand the theory before you start the hands-on work.

Topology refers in a general sense to layout; similarly, a network topology defines the layout of the network. The three basic network topologies are bus, star, and ring. The following sections discuss the different network topologies and their characteristics.

Bus

A bus topology uses a main wire (or trunk) to connect all network devices so that they can communicate with one another. The main trunk is fairly cheap to install but expensive to maintain. Figure 1-3 shows a diagram of a bus topology; notice that all systems are connected to a main cable.

When a workstation sends data to another workstation in a bus topology, data (in the form of an electrical signal) is delivered across the full length of the trunk. Each workstation looks at all data that runs along the trunk. If the data is destined for a particular workstation, that workstation copies the data to the memory on its network adapter.

For example, Figure 1-3 shows what happens when client A sends information to client B.

1. The information runs along the trunk.

2. When it passes by client C, client C checks whether it is also a destination for the information; if not, client C ignores the data.

3. The information continues down the wire and makes its way to client B.

4. Client B looks at the data to determine whether the data is destined for it; if so, client B copies the data and stores it in the memory on the network card.

Note that because client B has made a copy of the data, the data is still on the wire. The data continues on the wire past the server and hits the terminator at the end of the trunk segment.

A terminator is a device that absorbs the electrical signal when it reaches the end of the network trunk. If there were no terminator at the end of the cable, the signal would bounce back in the other direction and collide with any new data being placed on the wire. So, to prevent this collision, the terminator grabs any signals that hit it and ensures that it is absorbed off the wire.

In a bus topology, any break in the wire creates a nonterminated end. When there is a nonterminated end on the bus signal bounce occurs and as a result the entire network collapses.

Star

One of the most popular types of network topologies today is the star topology. A star topology, shown in Figure 1-4, involves a central component, called a hub (older networks) or a switch (today’s networks), which connects all systems and is used to send the electrical signal to all connected systems.

With the star topology shown in Figure 1-4, if client A sends information to client D, the information first travels from client A to the hub. The hub sends the information through each port on the hub: as a result, reaching each workstation connected to the hub. Each workstation is responsible for determining whether it is the data’s intended destination. When client D receives the data, it checks the destination address of the packet, identifies itself as the recipient of the data, and then copies the data to the network adapter’s memory. If the data is not destined for the client, the client simply discards the packet.

Today’s networks use switches instead of hubs. Here’s an example of how a switch works. When client A sends data to client D, the information first travels from client A to the switch and then the switch forwards the information only to the port that client D resides on. The information does not get sent to all the clients connected to the switch, like what a hub does. This data path offers performance benefits and also security benefits. Find more on hubs and switches later in the “Working with Network Devices” section of this chapter.

One of the major benefits of using a star topology is that if a cable breaks, it doesn’t take down the entire network like it would with a bus topology; only the workstation connected to the broken cable is affected. If a hub device breaks, however, the entire network fails. In all fairness, though, the cost to implement a star topology might be a little more than a bus topology because of the price of the hub or switch device used.

Ring

In a ring topology, each computer is connected to the next computer, creating a physical ring. Although ring topologies are not common today, you still see them in IBM’s token ring architecture (see the section “Token ring,” later in this chapter). Figure 1-5 shows a ring topology.

In environments that use the ring topology, data is usually passed from workstation to workstation. Because data becomes distorted when it travels great distances, each workstation is responsible for reading the data, regenerating the data, and then passing the information on to the next workstation. Like with a bus topology, any break in the ring causes the entire network to fail.

Mesh

A mesh topology is a network topology that involves each system having a connection to every other system on the network. This is very costly because you need enough equipment such as network cables and network cards to connect all systems to one another. The benefit of a mesh topology is that you have multiple pathways to send data to any system on the network. This is a way to add fault tolerance to the communication system.

Hybrid

A hybrid topology is a mixture of two or all of the three basic topologies. For example, you could use a bus topology as a main trunk, connect hubs to the main trunk, and then connect the systems to the hubs. Figure 1-6 shows an example of this type of hybrid topology.

To be more accurate, the configuration shown in Figure 1-6 could be called a star-bus topology — a star topology mixed with a bus topology. Today, the most popular topology in use is the star topology — or maybe even a hybrid topology using a star-bus layout.

Wireless

Today’s networks allow more mobility for network clients by supporting wireless technologies. To implement a wireless solution, you build a wireless network that uses a wireless topology. A wireless topology typically involves a wired network with wireless clients connecting to the wired network through a wireless access point (WAP), which is a device that sends and receives signals to a wireless client via radio waves (shown in Figure 1-7).

Notice in Figure 1-7 that the wireless client sends data to the WAP, which has a connection to the wired network. The WAP sends the wireless data to the destination system by sending the signal through the wired media.

Connecting with Network Cabling

After choosing your network topology, it is time to connect all the network devices together, which means deciding the type of cabling to use. The following sections discuss and evaluate the different types of cabling available for standard networks.

Twisted pair

Twisted pair cabling, which is inexpensive and easy to use, is one of the most popular types of cabling used. It gets its name from the fact that it contains four pairs of wires twisted around each other inside the cable’s outer jacket, the outer covering of the cabling shown in Figures 1-8 and 1-9. Twisted pair cabling comes in two flavors — unshielded twisted pair (UTP) and shielded twisted pair (STP) — shown in Figure 1-8 and Figure 1-9, respectively.

The only difference between UTP and STP is that STP cabling has an extra layer of insulation, which helps prevent interference from outside devices or cabling. Such interference can distort the data traveling along the cable length.

UTP comes in a number of different flavors, called grades or categories. Table 1-1 lists the categories of UTP cabling, as well as their purpose and speed.

Table 1-1 UTP Category

Category	Purpose	Speed
Category 1 (CAT1)	Voice only
Category 2 (CAT2)	Data	4 Mbps
Category 3 (CAT3)	Data	10 Mbps
Category 4 (CAT4)	Data	16 Mbps
Category 5 (CAT5)	Data	100 Mbps
Category 5e (CAT5e)	Data	1 Gbps
Category 6 (CAT6)	Data	10 Gbps

Because twisted pair cabling does not have the layers of shielding found in other forms of cabling, the data is pretty much unreadable — or the integrity of the data is questionable — after 100 meters. For this reason, twisted pair cabling has a maximum length of 100 meters.

For the exam, you are expected to know the speeds of the different categories of UTP cabling. Also, remember that twisted pair cabling has a maximum distance of 100 meters regardless of whether it is a shielded or unshielded twisted pair.

Twisted pair cabling uses a special type of connector to connect the cable to the system or network devices. This connector is similar to those used to connect a telephone to a telephone jack. Network devices that use twisted pair cabling use the RJ-45 connector, and telephones use the RJ-11 connector. Figure 1-10 shows both.

Wiring standards

When looking at UTP cabling, two common standards have been defined that dictate the order of the wires within the UTP cable. The two common standards for twisted pair cabling are T568A and T568B. Each of these standards defines the order of the eight wires within the cable and has been developed to give the best-quality transmission.

Coaxial

Coaxial (coax) cabling is the type of cable you use for cable television. A copper wire in the center of the cable is responsible for transmitting information. Furthermore, the copper wire is protected by two levels of insulation and an exterior plastic covering, as shown in Figure 1-11.

Like UTP, coaxial cabling used for networking comes in different flavors — two, to be exact. Thinnet is only one-quarter-inch thick, and Thicknet is one-half-inch thick. Table 1-2 shows the difference between Thinnet and Thicknet.

Notice in Table 1-2 that the coaxial cable type is specified by a radio grade (RG). There are a number of grade standards for coaxial cable, and each standard has a specific purpose and connector type that will work with that type of cabling. For example, RG-58–grade cabling (Thinnet) uses BNC connectors (discussed in more detail in the next section), and an RG-8–grade cable uses an AUI connector.

Another popular grade of coaxial cable is RG-6 — the grade of coax used for television cable — which uses the F-type connector (also known as the F-connector) to connect the cable to the device. Figure 1-12 displays coaxial cables along with an F connector and a BNC connector. Another common-grade coax cable that is used by cable television is RG-59.

Connecting with Thinnet

When using Thinnet to connect to a workstation, you need to use a Bayonet Neill-Concelman (BNC) connector — also known as British Naval Connector (BNC), which comes in a few forms. You will most likely encounter the plain old BNC and the BNC-T.

The BNC connector connects Thinnet cable to a networking device, such as a network card, using the barrel connector on the back of the network card, as shown in Figure 1-13.

The BNC-T — shaped like the letter T — is used to continue the cable length while “T-ing” off to connect a system to the network, as shown in Figure 1-14.

Notice in Figure 1-14 that the BNC-T connects to a metal barrel–type port on the back of the network card. If you do not need to continue the cable length and this is your last workstation, you are required to terminate the end with a terminator on the T connector, as shown in Figure 1-15.

Connecting with Thicknet

A system or device connected to a Thicknet network uses an adapter unit interface (AUI) port (shown in Figure 1-16), which connects the system to the Thicknet cabling by using a transceiver known as a vampire tap.

The vampire tap gets its name by having small “teeth” that clamp to the cable and cut into the cable’s core, allowing the electrical signal to travel from the system to main network cable and beyond.

Fiber optic

Fiber optic cabling — one of the fastest types of network media available — is made of a glass fiber core (optical fiber) surrounded by a layer of glass cladding insulation that is then covered with an outer covering (jacket). There are two fiber channels in fiber optic cable: one for sending information and the other for receiving information. Figure 1-17 illustrates a fiber optic cable.

Fiber optic cabling can reach distances of 2 kilometers (km) or more, carrying a signal for a much greater distance than twisted pair and coaxial cabling. Fiber optic cabling is also fast, transmitting information at speeds of 1 Gigabit per second (Gbps) and higher. And, because fiber carries data in pulses of light instead of electronic signals, data cannot be corrupted by outside electronic interference.

You will be expected to know details regarding fiber optic cabling for the exam. Fiber carries data through pulses of light along its glass core and can reach distances of 2 km. Fiber optic cable transmits information at speeds that range from 100 Mbps to 10 Gbps.

The two implementations of fiber optic cabling are single-mode fiber (SMF) and multi-mode fiber (MMF):

Single-mode fiber (SMF): Uses only one ray of light, known as a mode, to carry the transmission over great distances.

Multi-mode fiber (MMF): Takes advantage of multiple rays of light, or modes, simultaneously. Each ray of light runs at a different reflection angle and is used to transmit data over short distances.

Fiber optic cabling uses a number of different types of connectors. The following list provides a few that you need to be familiar with for the A+ exam:

Straight tip (ST): The straight tip connector is derived from the BNC-style connector but uses a fiber optic cable instead of the copper cabling used with BNC. Figure 1-18 shows an SC and ST connector.

Subscriber connector (SC): The subscriber connector is rectangular and is somewhat similar to an RJ-45 connector.

Fiber local connector (LC) and mechanical transfer-registered jack (MT-RJ): These newer fiber optic connector types resemble the registered jack and fiber SC shape. The MT-RJ is a small connector similar in appearance to an RJ-45 connector. The LC is similar in appearance to the fiber SC connectors and is the preferred connector for transmissions exceeding 1 Gbps because of its small form factor.

The primary disadvantage of using fiber optic cabling is the implementation cost and the expertise required for the wiring.

Troubleshooting Networking Cables

Most network professionals use cable testers to test the cabling and verify that the cable is properly crimped and making contact with the networking devices. For example, cable testers for CAT5 cabling identify whether each of the eight wires is crimped properly and identify other problems, such as wires being crimped in the wrong order.

EMI

Another problem you need to be aware of when running cable throughout a building is that twisted pair and coaxial cables are susceptible to outside interference from other electrical components. For example, do not put networking cable alongside the electrical cabling because the electrical cabling could cause interference that could make the data on the network cable unreadable. For more information on cable testers and troubleshooting cabling problems, check out Book IV, Chapter 2.

Plenum

Here is one last point to make about cabling to help you prepare for the A+ certification exams. Plenum — the space between the ceiling tile and the floor above — is a popular place to run cables. If you are going to run cables in this area, make sure that you are use plenum-grade cabling, known as Teflon-covered cable. If you are using nonplenum-grade cabling, such as PVC cover cabling, in this space and a fire happens, the PVC coating can give off a toxin that could be spread throughout the building.

Examining Network Access Methods

Network access refers to the different methods that computers use to place data on the network. This section discusses these methods and identifies the advantages and disadvantages of each.

CSMA/CD

One of the most popular types of access methods is CSMA/CD (Carrier Sense Multiple Access/Collision Detection). Understanding this term is easier if you break it down into its individual parts and examine each part in detail:

Carrier sense: All computers on the network are watching, or sensing, the network for network traffic. If the network has data already on the wire, a system will wait until the wire is free of traffic.

Multiple access: All computers on the network have equal access to the network at any given time. In other words, anyone can place data on the network whenever he or she chooses. Note, however, that workstations on the network will try not to place data on the wire at the same time the wire is transmitting other data because the two pieces of data will collide, destroying the data. That’s why it’s so important for workstations to “sense” the wire.

To summarize, carrier sense multiple access suggests that all workstations have access to the network and are watching the network to make sure it is clear of data before they send out their information.

Collision detection: When two workstations send information at the same time, the data will collide and be damaged in transit. When two workstations have data that has been involved in a collision, they resend the information out on the network at variable intervals to prevent the data from colliding again.

The nice thing about CSMA/CD is that the workstations decide when to send data, trying to prevent collisions. However, there is always the possibility that multiple workstations will send data out at the exact same moment the network is clear, resulting in data collision.

CSMA/CA

Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) is similar to CSMA/CD except for one main difference: When a workstation senses that the wire is free, it sends out dummy data first instead of real data. If the dummy data collides with other information on the wire, the workstation has avoided a collision with the real data; if the dummy data does not collide, then the workstation sends the real data. Like CSMA/CD, if the real data collides and does not reach its destination, it will be resent by the sender.

CSMA/CA is not a popular access method, but it has been used in AppleTalk networks.

Token passing

You might have attended a meeting where a ball was passed around to indicate who had the authority to speak: In order to speak, you had to be holding the ball; if you didn’t have the ball, you had to wait your turn. Token passing is based on the same principle. A token — an empty container running around the network from computer to computer — must be in a computer’s possession before the computer can put data out on the wire.

When the token reaches a workstation, the workstation puts data out on the wire by filling the token with information and marking the token as being used. The token (with the information) is then released onto the network and travels toward its destination. Each workstation checks whether the token is destined for it when the token passes by. Each workstation regenerates the data and passes it to the next workstation.

When the token reaches the destination, the destination system reads the data and then sends a reply or confirmation message to the sending computer. When the sending computer receives the reply, it places a new, empty token on the wire.

Piecing Together the Network Architectures

A network architecture describes a network technology that uses a specific topology, cable type, and access method. This section describes the major types of architectures and their characteristics.

Many people use the term architecture to mean topology, stating that the three main types of architectures are bus, star, and ring. However, bus, star, and ring are properly defined as topologies, not architectures. Be careful not to confuse the two terms. A topology defines the network layout, whereas an architecture is made up of a topology, cable type, and access method.

Ethernet

Ethernet is probably the most popular type of network architecture in use. Ethernet is an example of a network architecture that comes in multiple flavors. If someone says to you, “I have an Ethernet network,” you are likely to ask, “What type of Ethernet?”

There are a number of types of Ethernet: 10BaseT, 10Base2, 10Base5, 100BaseT, and 1000BaseT being a few popular ones. All Ethernet architectures use CSMA/CD as the access method, but each type of Ethernet uses a different topology or cable type. The following sections outline the differences among them.

10 megabit Ethernet standards

The following outlines some of the popular 10 Mbps network architectures that have been popular in past years. You need to be familiar with these for the A+ Certification exams.

When trying to remember the names of these network architectures, start by looking at the number at the beginning of the name — it indicates the transfer rate. In this case, the transfer rate is 10 Mbps. You can then look at the tail end of the name to tell what type of cable the architecture uses. For example, in 10BaseT, the letter “T” at the end of the name implies “twisted pair.” The word “base” in the middle means baseband transmission, which means that the signal takes up the entire width of the media when sending and receiving data.

10BaseT: A network architecture that typically uses a star topology but can, in some cases, use a hybrid star-bus topology. 10BaseT networks primarily use CAT3 UTP cabling, which transfers information at 10 Mbps. 10BaseT uses the CSMA/CD access method for putting information on the network.

10Base2: A network architecture that uses a bus topology, but can sometimes use a hybrid star-bus topology. 10Base2 networks typically use Thinnet coaxial cabling, which transfers information at 10 Mbps. 10Base2 uses CSMA/CD as its access method.

10Base5: A network architecture that uses a bus topology. 10Base5 networks primarily use Thicknet coaxial cabling, which transfers information at 10 Mbps. Like 10Base2, 10Base5 uses CSMA/CD as its access method.

10BaseFL: An old Ethernet architecture that ran at 10 Mbps and used fiber optic cabling. 10BaseFL uses CSMA/CD as the access method.

Remember that 10BaseFL used fiber cables by the F in the name.

100 megabit Ethernet standards

You are unlikely to see a 10 Mbps network architecture on today’s networks, so it is more important that you have an idea of some of the popular 100 Mbps Ethernet architectures:

100BaseT: An improved network architecture over the 10BaseT networks. It uses a star topology, but can also be found using a hybrid star-bus topology. 100BaseT networks primarily use CAT5 UTP cabling, which transfers information at 100 Mbps. 100BaseT also uses CSMA/CD as its access method.

100BaseFX: Another Ethernet architecture that runs at 100 Mbps but is different than 100BaseT in that it uses fiber optic cabling instead of UTP cable. 100BaseT and 100BaseFX are referred to as the “Fast Ethernet” standards. 100BaseFX uses CSMA/CD as the access method.

Gigabit Ethernet standards

Today’s corporate networks are reaching 1 Gbps (1000 Mbps) and higher, so it is important that you are familiar with the Gigabit Ethernet standards for the A+ certification exams:

1000BaseT: Uses UTP cabling; uses CSMA/CD as the access method

1000BaseSX: Uses multimode, fiber optic cabling for short distances; uses CSMA/CD as the access method

Remember this architecture by the S in the name, meaning short ­distances.

1000BaseLX: Uses single-mode fiber optic cabling; uses CSMA/CD as the access method

Because single-mode fiber optic cabling is designed for long distances, it is the type of fiber optics used for 1000BaseLX. Remember this standard by the L in the name, implying long distances.

10 Gigabit Ethernet standards

Some of the fastest network standards today fall into the 10 Gbps Ethernet architectures. The 10 Gbps Ethernet architectures use fiber optic cabling, either SMF or MMF, depending upon the architecture. For example, the 10GBaseSR standards uses multimode fiber optic cabling that can reach a short distance of 100 meters, and 10GBaseLR uses single-mode fiber optic cabling that reaches a distance of 10 km.

Nowadays, you will probably purchase network cards that are marketed as 10/100 cards or maybe even 10/100/1000 cards. This means that the network card can be used with networking environments that transfer information at 10 Mbps, 100 Mbps, or 1000 Mbps.

Token ring

Token ring is a unique network architecture because it is completely different in design from Ethernet. As its name implies, token ring uses a ring topology with token passing as the access method. Although a token ring network can use almost any type of cabling, it typically uses CAT5 UTP.

Token ring, which comes in two flavors (4 Mbps and 16 Mbps), also has a special name for the hub that connects all the workstations together — multistation access unit (MAU). Because of this MAU, a token ring network appears to use a star topology, but internally, the MAU is connected as a ring, making a complete circle. Figure 1-19 shows a token ring MAU.

For the exam, remember that all Ethernet environments use CSMA/CD as an access method, and token ring architectures use token passing as their access method. Also remember that token ring was developed by IBM.

When IBM developed token ring architecture, the company also developed its own cable type and a proprietary connector: the IBM-type data connector (IDC) or universal data connector (UDC). Figure 1-20 shows an IBM proprietary cable with an IDC connector.

FDDI

The Fiber Distributed Data Interface (FDDI) network architecture uses token passing as an access method and fiber optic cabling as a cable type. FDDI also uses a ring topology like token ring does, but the difference is that with FDDI there are two rings: a primary ring and a secondary ring. The secondary ring is used for fault tolerance if the primary ring goes down, meaning that the second ring is only used if the primary ring fails.

Lab 1-1 helps you review the different network architectures. You can find Lab 1-1 on the companion website at www.dummies.com/go/aplusaio.

Understanding Network Protocols

To ensure that all the networking components work with one another, networking standards have been developed. If a company decides that it wants to develop something like a network card, it will ensure that the network card follows a standard so that it can communicate with all the other networking components. In this section, you find out about the different network standards that help each networking vendor develop networking components that function alongside other networking devices.

IEEE standards

The Institute of Electrical and Electronics Engineers (IEEE) has developed a number of LAN standards that define the physical components of networking technologies. In these standards, the IEEE has defined such things as how network cards place data on the wire and the type of cabling used in different types of LANs. The LAN standards are defined by Project 802, which was launched in February 1980. These 12 standards, shown in Table 1-3, define different networking architectures.

Table 1-3 Project 802 LAN Standards

Project	Description
802.1	Internetworking
802.2	Logical Link Control (LLC)
802.3	Ethernet (CSMA/CD)
802.4	Token Bus LAN
802.5	Token Ring LAN
802.6	Metropolitan Area Network
802.7	Broadband Technical Advisory Group
802.8	Fiber Optic Technical Advisory Group
802.9	Integrated Voice/Data Network
802.10	Network Security
802.11	Wireless Networks
802.12	Demand Priority Access LAN

A few of the networking standards that you should be familiar with are 802.3, 802.5, and 802.11:

802.3: This networking standard defines the Ethernet architecture, also known as CSMA/CD. This standard defines how data is placed on the wire. A system senses the wire to verify that it is free of data and then submits the data.

802.5: This IEEE standard defines the token ring network architecture. This architecture uses the token passing access method, which is a set of rules that control how a system submits data on the wire.

802.11: This IEEE standard defines wireless networking. Wireless networking has evolved over the past few years, and as a result, there are a few different types of wireless networks, wireless 802.11b and 802.11g being the two dominant standards:

• 802.11b: This wireless standard has a transfer rate of 11 Mbps and runs at the 2.4 GHz frequency range. 802.11b created the Wi-Fi ­standard.

• 802.11g: This wireless standard has a transfer rate of 54 Mbps and is backward compatible with 802.11b because it also runs at the 2.4 GHz frequency and is part of the Wi-Fi standard. This means that you can have an 802.11b WAP and have a system with a more current 802.11g wireless network card, and both systems will still be able to communicate. They will use the lower transmission rate of the two, though!

• 802.11n: This new wireless standard has a transfer rate of up to 300 Mbps and is compatible with 802.11b and 802.11g wireless networking environments because it runs at the 2.4 GHz frequency.

For the exam, you don’t need to memorize the entire list of standards. However, know that Ethernet is defined in project 802.3, token ring is defined in project 802.5, and 802.11 defines the wireless standards. You will be tested on them!

For more information on wireless networking, check out the next chapter.

The OSI model

The Open Systems Interconnect (OSI) model is a seven-layer model defined by the International Standards Organization (ISO) that provides a framework that manufacturers of networking components can use to develop networking hardware and software components.

Each layer of the OSI model is responsible for specific network functions. For example, the network layer is responsible for logical addressing, so any devices or protocols that provide logical addressing run at this layer — such as the IP protocol. Table 1-4 outlines the seven layers of the OSI model and provides examples of networking components that run at that layer.

Table 1-4 The OSI Model

Layer	Description
7, Application	Responsible for making or receiving a network request and is typically the networking software. For example, a Web server, FTP server, and DNS server run at this layer.
6, Presentation	Responsible for formatting the information so that the information is understood on the receiving system. Examples of formatting are compression and encryption.
5, Session	Responsible for opening, closing, and managing a connection (a session) to another system or device.
4, Transport	Responsible for breaking the information down into smaller pieces so that it can be sent along the network in parts. This layer is also responsible for ensuring that the information reaches the destination.
3, Network	Responsible for routing of information and logical addressing. A router runs at this layer, and the IP protocol runs at this layer, which provides a logical address (IP address).
2, Data Link	Prepares the information to hit the physical network by placing the data into packets. The data link layer also provides the physical addressing (MAC address), so any device that works with a MAC address runs at this layer (such as a network card, switch, and bridge).
1, Physical	Deals with the network media such as cabling and connectors. The physical layer is also responsible for sending the electrical signal on the wire. Any device that works with the electrical signal runs at this layer such as a hub or repeater.

Although the OSI model is more of a Network+ topic, you might receive a few questions on the OSI model with your A+ Certification exams. Be familiar with what layer of the OSI model a hub, switch, and router run at.

Voice over IP (VoIP)

Voice over IP (VoIP) is a fairly hot topic these days. VoIP deals with allowing subscribers to the VoIP service to have telephone conversations over a TCP/IP network, such as the Internet. The benefit of such a service is no more long-distance charges — just your monthly subscription to the service.

VoIP not only allows for the transmission of voice but also other types of data, such as video. VoIP has become a popular method of communication that supports PC-to-PC communication, essentially using the PC as a phone.

Working with Network Devices

A computer network is a lot more than just a few computers and a tangle of cables. A computer network needs a number of different types of devices to connect the systems or to connect the network to another network. This section identifies the different types of network devices popular in network environments today and covers the devices you will be tested on for the A+ exams.

Be familiar with these devices for the A+ exam and understand their benefits.

Network interface card (NIC)

The network interface card (commonly referred to as a network card) is responsible for connecting the computer or device to the network. More importantly, the network card on the sending computer is responsible for converting digital data into an electrical signal for copper or optical signal for fiber that can be placed on the wire. The network card on the receiving computer is responsible for picking up the electrical signal and then converting it back to digital data that can be understood by the computer system.

Each network card has a unique address burned into the ROM chip on the card. This unique address is considered the hardware address of the network card because the manufacturer of the card burns it into the card. The address uniquely identifies your system on the network. The hardware address is also known as the Media Access Control (MAC) address. An example of a MAC address is 00-20-3F-6B-25-13.

Looking at the example of a MAC address, notice that the MAC address is made up of hexadecimal addresses — not your typical decimal numerals or binary values. Of the six groups of digits, the first three pairs identify the manufacturer of the network card, and the last three pairs are a unique set of digits assigned to a particular card built by the manufacturer. So, 00-20-3F, which appears at the beginning of my example MAC address, represents the manufacturer of the card, and 6B-25-13 identifies the card.

The MAC address of the sending and receiving system is stored in the header of the network packet that travels the network wire. When each system sees the packet traveling by it, it looks at the destination MAC address to decide whether the data is destined for it. If a system finds that it is the intended recipient for the data, it copies the data to its buffer, which is memory used to store the information while it waits to be processed. Figure 1-21 shows a network interface card.

Two lights on the network card act as status indicators — the activity light and the link light. The link light is always lit when you have a connection to the network; the activity light blinks when the network card is sending or receiving information. When troubleshooting network problems, always check that the link light is on, indicating a connection to the network.

Repeater

One major concern with cabling is the maximum usable length of the cable. For example, UTP cabling has a maximum length of 100 meters, and Thinnet has a maximum length of 185 meters. The reason for putting a maximum distance on cable lengths is that the signal traveling along the cable becomes too weak to read at the destination system by the time the maximum length is reached. The receiving computer cannot read the information, and thus does not acknowledge that it received the data. When the sending computer does not receive an acknowledgment, it simply resends the data. This causes the information to be resubmitted, generating more network traffic.

One way to increase the distance of a cable length is to use a repeater, which regenerates a signal so it can travel the extra distance. For example, the repeater shown in Figure 1-22 joins two lengths of Thinnet coaxial cable. It joins the two cable lengths so that the signal can travel the distance from computer A to computer B. Note that this distance exceeds 185 meters, which is the maximum distance of Thinnet. When the signal hits the repeater, the repeater rebuilds the signal so that it can travel another 185 meters.

Bridge

Because all data passing through a repeater is regenerated and sent to all parts of the network, a great deal of network traffic is generated that affects the overall performance of the network.

To prevent this buildup of network traffic, you can use a bridge (as shown in Figure 1-23), which is a device that connects network segments and also regenerates the signal (like a repeater). A bridge also filters the data so that it is sent only to the proper portion of the network, cutting down on network traffic and increasing overall performance.

Figure 1-23 illustrates that when computer A sends information to computer C, the information travels along segment 1 and eventually reaches the bridge. The bridge looks at its bridging table (a list of MAC addresses and corresponding network segments that runs in memory) to see which network segment computer C exists on. In this example, it lives on segment 3. At this point, the bridge forwards the information only to segment 3, where computer C resides, and not to any other segment, thus filtering traffic and cutting down on network noise.

Bridges increase performance on the network by filtering the network traffic, which gives the network and all its devices and applications more bandwidth to work with. The less network traffic, the less chance of collision and retransmission.

Router

A router, which is responsible for sending information from one network to another, is an important network device because most companies are connected to the Internet. When a computer on your network wants to send information to a computer on another network, your computer passes the information to your router. Figure 1-24 shows three different networks, each connected to the Internet by a separate router. All computers on network A know that any information with an outside-network destination must be passed to the router because the router is the only device with a physical connection to the outside world.

Gateway

A gateway is a unique network device responsible for converting information from one format to another. Think of a gateway as a translator between two different languages: As information passes from one side to another, the gateway “translates” the information to a format that can be understood on the other side.

You might encounter questions on the exam in which you must identify the device based on a description. For the exam, remember that a gateway is a device or piece of software that translates data from one format to another.

Hub

A hub is a central device that acts as a connection point for all hosts on the network. A hub is a very basic device that passes all data that hits the hub to every port on the hub. This means that when a computer sends data to another computer, all systems will see the data on the network even though only the destination system for the data will process the data. Figure 1-25 shows a network hub.

As the number of hosts on the network grows, you can “cascade” or connect one hub to another. Any data that reaches a port on a hub will be sent to all ports on all connected hubs, which could congest the network with traffic.

As I mention earlier, today’s networks use switches instead of hubs. The term “hub” is used in this chapter only so that you know what a hub is in case you come across it in conversation or readings.

Switch

A network switch is a device that looks similar to a network hub but differs in that the switch does not forward the data to all ports like a hub would. Instead, the switch filters network traffic by only sending the data to the port that the destination system resides on. Figure 1-26 shows a network switch.

Switches can dramatically increase network performance because they filter the traffic by sending the data only to the destination port on the switch instead of to all ports on all hubs. Switches also offer security benefits because a system that is not the destination of the information does not receive a copy of the information, thus reducing the opportunity that someone other than the intended recipient can see your information.

Most switches today also offer security features such as port security, which enables you to limit which systems can connect to a port on the switch by MAC address. You can also control which ports a system can send data to!

Wireless access point (WAP)

A very popular network component today is a wireless access point. A WAP, typically connected to a wired network, is responsible for accepting data from wireless clients and then passing that data to systems on the wired network. The wireless access point can also receive information from the wired systems and then send that information to the wireless systems.

You can find a number of popular brands of wireless access points, such as Linksys, D-Link, and NetGear. Wireless access points that include additional features, such as firewall capabilities, are wireless routers. Figure 1-27 shows a wireless router used by home and small office networks.

A wireless router has an antenna that collects the radio waves that carry the data from the wireless client. The wireless router also has a WAN port on it so that you can connect your Internet cable into it and share the Internet connection with all systems on the network. The WAP in Figure 1-27 also has four additional RJ-45 ports to connect four wired systems.

The WAP is a multifunction device in the sense that it not only allows wireless clients to connect to the network, but it is also a four-port switch, allowing wired clients to connect to the network.

Other networking devices

You may find a wealth of different network devices out there on different networks. Some other common network devices you may find are

Modem: The modem is used to dial up across the phone line to another network and gives a remote user access to network resources.

NAS: Today’s networks have network attached storage (NAS) devices, which are an enclosure that contains a number of hard drives that connect to the network.

Firewall: Most networks and systems today have firewalls that are used to limit the type of traffic that can enter the network or system.

VoIP phones: To carry voice over an IP network using voice over IP (VoIP), many companies today have VoIP phones that are connected to a network.

Internet appliance: A number of different Internet appliances can exist on the network. These appliances can act as proxy servers that filter what websites users can visit and cache web content.

Using network troubleshooting tools

One of the challenging parts of supporting networks today is knowing how to troubleshoot them. You find so many aspects of the network that it is difficult to know where to start your troubleshooting. The following is a listing of some common troubleshooting tools you should be familiar with for the A+ Certification exams:

Crimper: A cable crimper is used to attach the connectors to the ends of the cable.

Multimeter: A multimeter is used to test voltage and current and can be used to diagnose problems with a cable.

Toner probe: A toner probe is used to locate cables in a mess of cables. You place the tone generator on one end of the cable and then place the toner probe on the other end of the cable to ensure that you have the right cable.

Cable tester: You can use a cable tester to verify connectivity from one end of the cable to another.

Loopback plug: A loopback plug is used to connect to a port and verifies that the port is actually working without sending data onto the network.

Punch-down tool: A punch-down tool is used by technicians to create the connections on a patch panel.

Understanding Communication Methods

Different network devices, such as network cards, support different methods of communication. The three major communication methods in the computer world are simplex, half-duplex, and full-duplex:

Simplex: A device that supports simplex communication can deliver information in only one direction. Typically, the device can send information but cannot receive information.

Half-duplex: A device that supports half-duplex communication can deliver information in two directions, but not at the same time. A typical example of a half-duplex device is a walkie-talkie or CB radio, which enables you to send and receive information but not at the same time. When you use a CB radio, you say “Over” to let the person on the other end know that you are done talking and that it is the other person’s turn to send information.

Full-duplex: A device that supports full-duplex communication is one that can send and receive information at the same time. Full-duplex is similar to talking on the phone: You are free to speak and to listen at the same time.

When purchasing networking or other types of devices for your computer, it is important to know whether you are buying a simplex, half-duplex, or full-duplex device to avoid problems later. For example, a musician friend of mine wanted to record his own material on the computer with recording software. After recording the first track, he had a problem recording a second track because his sound card was only a half-duplex device. He wanted to listen to the first track while playing along and recording the second track, which was impossible with his half-duplex sound card. He needed to have the sound card send and receive information at the same time, something that a half-duplex device can’t do. The solution: Get a new, full-duplex sound card.

Ways to Network a Computer

If you want to build a small network with four computers in the home and have each system connect to the Internet, the best thing to do is to buy a home router from D-Link or Linksys. After you buy the home router, which is also a four-port switch, connect the four computers to the ports on the router and then plug the Internet connection into the WAN port. All systems are now interconnected and also to the Internet. But what if you need to connect two systems and you cannot connect them by using a hub or switch? You need to be aware of the different and varied methods used to network two computers, including the following:

Installing network cards

Using serial or parallel ports

Using infrared ports

The following sections describe the different computer networking methods.

Network card

The first task when using network cards to network two computers is to find out what type of network card you need for each system. You will have to find out whether the network card will be an ISA, EISA, or PCI device. Open up the system and look at the different expansion slots that exist, or you can look at the documentation for the system.

After you purchase the network card and install it into your system, load the driver for the network card. If you’re lucky and the network card is a Plug and Play device, the driver might load automatically for you, or you might be prompted by the OS to provide a manufacturer diskette with the driver for the device.

After you install the driver, you might have to spend some time troubleshooting the device because of resource conflicts with other existing devices. Once again, if you have a Plug and Play device, this step will probably not happen because the resources will be assigned dynamically by the OS.

Serial and parallel ports

You may also network two computers via the serial or parallel ports of both systems. Using standard parallel or serial ports for networking two devices can be a lot slower than networking two computers via a network card. You will connect the parallel ports with a laplink cable, and you will use a null modem cable for serial ports (RS-232 ports).

Here are the two networking methods that use serial ports:

Connect a modem to each computer’s serial port and have the modems use the phone lines as the cabling.

Connect two computers directly by connecting the serial ports with a null modem cable.

If you try to connect two computers with a normal serial cable, the transmit data (TD) wire on one computer will be connected to the TD wire on the other computer, and the receive data (RD) wire on one computer will be connected to the RD wire on the other computer. No communication will occur in this situation. What you need is the TD wire on one computer connected to the RD wire on the other computer. A null modem cable is designed to do this, crossing the sending and receiving wires.

Infrared port

Devices can also use infrared ports that can be used to connect to other devices on the network over short distances. For example, you can print to a printer sans parallel cable by using infrared technology.

Infrared technology uses an infrared light beam to carry data between devices. It typically requires clear line-of-sight — a clear path between the two devices. Infrared is limited in distance to about 100 feet and can transfer information up to 10 Mbps.

Lab 1-2 gives you some practice creating a small office or home network. Lab 1-2 can be found on the companion website at www.dummies.com/go/aplusaio.

Installing a Small Office/Home Office (SOHO) Network

When installing a Small Office/Home Office (SOHO) network — a home office network or a network to be used by a small office with a few employees — you need a number of network components to get the network up and running. This section introduces you to the network components needed to build a small network.

The first major component that you need is a home router, which is a multifunctional device that provides you with all the network components that are needed for your SOHO. Then decide whether to go wired or wireless. If you opt for wired, you need the appropriate type of cabling. If you go wireless, make sure you get a wireless router. Finally, you might want to think about using a server. After the networking nuts and bolts are in place, think about security.

Functions and benefits of a home router

A home router has a WAN port that you use to connect to your high-speed Internet connection. This could connect to your cable modem or your DSL modem, and will be used to share the Internet connection with any users on the network.

The following is a list of benefits to having the home router in your SOHO network:

DHCP: The first feature of the home router that is important is that the home router is a DHCP server, which is responsible for assigning IP addresses to clients on the network so that they can gain network access.

Internet sharing: The home router will also share the Internet connection that is plugged into the WAN port to all the users on the network. This functionality is provided through Network Address Translation (NAT) capabilities.

Wireless capabilities: Most home routers are also wireless routers, which allow computers or devices with a wireless card to access the network. The wireless client sends data to the router, which will then be forwarded to the Internet through the WAN port.

Web site filters: Through the configuration of the home router, you can limit which Web sites users on your network can view. You can also put schedules in place that control when users can use the Internet. Today, home routers provide a number of filtering capabilities to control the type of content that can be surfed.

Network switch: A home router typically has a four-port switch built in to allow any wired clients to connect to the network. These clients will receive an IP address from the DHCP server built into the router as well so that they can use the network.

Firewall: A home router has firewall features built in to prevent persons on the Internet from connecting to the systems on your LAN. By default, the firewall is enabled!

To use a home router, simply connect the WAN port of the wireless router to your high-speed Internet connection and then connect your systems to any of the four LAN ports on the router. These systems will get an IP address from the DHCP server built into the router and then will be able to surf the Internet.

Running a server on a SOHO

You might eventually look at installing a server for your SOHO. The server performs many different functions, such as holding files that you want to share with other users on the network. The server could also be used to share a printer to all other users on the network.

This server doesn’t have to be a system running the Windows Server OS. It could be a Windows XP or Vista system with sharing enabled, and sharing a folder for everyone else to access or sharing a printer that everyone else on the network can access.

For more information on sharing printers and files, check out Book VIII, Chapter 3.

Wireless networking for a SOHO

A very simple way to allow systems to connect to your network without needing to run cables throughout the entire office or home is to use wireless networking. If you purchase a wireless router, it will allow computers with a wireless network card to connect to the wireless router and any systems connected to it. The wireless client will also be able to surf the Internet because the wireless router will share the Internet connection with not only the wired computers but the wireless systems as well.

To learn more about wireless networking, check out Book VIII, Chapter 2.

SOHO security practices

When building a SOHO network, you have to create a security network structure to protect your business assets. The three chapters in Book IX give you the foundation to network security, so be sure to read over those three chapters and incorporate them into your SOHO network.

Here is a summary of popular security best practices when creating a SOHO network and using a wireless router:

Wireless security: There are a number of steps to take to secure your wireless network. For more information on wireless networking check out Book VIII, Chapter 2.

• Change the Service Set Identifier (SSID)

• Disable SSID broadcasting

• Implement MAC filtering

• Enable an encryption protocol, such as WPA or WPA2

To learn more about wireless security, read Book VIII, Chapter 2.

Router security: Regardless of whether your router is wireless, look at disabling DHCP and statically assign an IP address to each system. The benefit is that if someone else connects to your network (especially if you have not secured the wireless), they will not get an IP address.

Firewall: Use a firewall to protect the network and to protect the systems. A home router has firewall features built in, but you might also look at installing personal firewall software on each system.

Administrator password: Change the usernames for any administrator accounts on your routers and servers if possible. Be sure to set a strong password on these accounts after they are renamed.

Update firmware: To make sure you are dealing with the most up-to-date features on the router, do a firmware update of the router. You can get any updates to the firmware from the manufacturer’s Web site.

Again, this section is definitely not designed to give you details on how to set up a SOHO network but rather to expose you to the term and some of the considerations with SOHO networking. You can incorporate all the networking and security features covered in Books VIII and Book IX in your SOHO network, so be sure to read those chapters carefully!

Getting an A+

This chapter introduces you to a number of key concepts in network terminology. Understanding networking and how to troubleshoot the network has become an important skill for an IT professional, and you will be asked a few networking questions on the A+ exam. Remember the following points when preparing for the exam:

The three types of cables used on networks are twisted pair, coax, and fiber optic.

The three basic types of network layouts (topologies) are bus, star, and ring.

An access method determines how a system places data on the wire. Two popular access methods are CSMA/CD and token passing.

Ethernet is the most popular network architecture used today. Other examples of network architectures are token ring and FDDI.

Some of the most popular networking devices are hubs, switches, and routers.

Switches filter network traffic by sending the data only to the port used by the destination system. Routers are responsible for sending data from one network to another.

Prep Test

1 What category of UTP cabling transmits data at 16 Mbps?

A Category 2

B Category 3

C Category 4

D Category 5

2 Which of the following defines simplex communication?

A Allows information to be sent and received, but not at the same time

B Allows information only to be sent

C Allows information to be sent and received at the same time

D Allows information to be sent, but only after dependent information is received

3 What is the transfer rate of Category 3 cabling?

A 2 Mbps

B 10 Mbps

C 16 Mbps

D 100 Mbps

4 What is the maximum distance of a Thinnet segment?

A 100 meters

B 500 meters

C 250 meters

D 185 meters

5 What is the recommended number of users for a peer-to-peer network?

A Fewer than 100

B More than 100

C Fewer than 10

D More than 10

6 What access method is used for Ethernet?

A Token passing

B CSMA/CA

C Twisted pair

D CSMA/CD

7 Which of the following defines half-duplex communication?

A Allows information to be both sent and received, but not at the same time

B Allows information only to be sent

C Allows information to be sent and received at the same time

D Allows information to be sent, but only after dependent information is received

8 What category of UTP allows for data transfer at 1 Gbps?

A Category 3

B Category 4

C Category 5

D Category 5e

9 Which topology must be terminated at both ends to prevent signal bounce?

A Ring

B Star

C Bus

D Coaxial

10 What access method best describes CSMA/CA?

A Data is placed out on the wire; the sending workstation detects whether there is an error and retransmits if there is.

B A token runs around the network; when a computer wishes to send data out on the network, it fills the token with information.

C Dummy data is placed on the wire; if the dummy data collides with other information, then the real information is not transmitted. If the dummy data does not collide, then the real data is delivered.

D Dummy data is placed on the wire; if the dummy data collides with other information, then the real information is transmitted. If the dummy data does not collide, then the real data is withheld.

11 Which of the following best describes a client-server environment?

A All users on the network connect to one another for the purpose of file sharing.

B All users on the network connect to a central server and access resources on that central server.

C All users on the network connect to one another for the purpose of printer sharing.

D Each user accesses only one other user’s computer.

12 What is the maximum distance of UTP cable?

A 100 meters

B 185 meters

C 250 meters

D 500 meters

13 Which of the following best describes token passing?

A Data is placed on the wire; the sending workstation detects whether there is an error and retransmits if there is.

B A token runs around the network; when a computer wishes to send data on the network, it fills the token with information.

C Dummy data is placed on the wire; if the data collides with other information, the real information is not transmitted. If the dummy data does not collide, the real data is delivered.

D Dummy data is placed on the wire; if the data collides with other information, the real information is transmitted. If the dummy data does not collide, the real data is withheld.

14 Which of the following sends data in the format of pulses of light?

A Fiber optic

B 100BaseT

C 10BaseT

D Coaxial

15 What is the maximum length of 10Base5 cabling?

A 100 meters

B 185 meters

C 250 meters

D 500 meters

16 Which of the following best describes full duplex communication?

A Allows information to be both sent and received, but not at the same time

B Allows information only to be sent

C Allows information to be sent and received at the same time

D Allows information to be sent, but only after dependent information is received

17 What Ethernet architecture transfers information at 1 Gbps over short distances and uses fiber optic cabling?

A 1000BaseSX

B 1000BaseLX

C 1000BaseTX

D 100BaseTX

18 What type of connector connects a Category 5e cable to a network card?

A BNC Barrel

B RJ-45

C RJ-11

D BNC

19 What is the maximum distance of fiber optic cabling?

A 100 meters

B 185 meters

C 500 meters

D 2 kilometers

20 What type of connector connects a 10Base2 cable to a network card?

A AUI

B RJ-45

C RJ-11

D BNC

Answers

1 C. Category 4 UTP cabling transfers data at 16 Mbps. See “Twisted pair.”

2 B. Simplex devices deliver information in only one direction. Review “Understanding Communication Methods.”

3 B. Category 3 cabling transfers information at 10 Mbps. Check out “Twisted pair.”

4 D. The maximum distance of a Thinnet segment is 185 meters. Peruse “Coaxial.”

5 C. The recommended number of computers in a peer-to-peer network is ten or fewer. Take a look at “Peer-to-peer networks.”

6 D. CSMA/CD is the access method that is used in all Ethernet environments. Token passing is used in token ring architectures, and CSMA/CA has been used in AppleTalk networks. Peek at “Ethernet.”

7 A. Half-duplex devices allow you to send and receive information, but not at the same time. Look over “Understanding Communication Methods.”

8 D. Category 5e UTP cabling transfers data at 1 Gbps. Study “Twisted pair.”

9 C. A bus topology must have all loose ends terminated to prevent signal bounce. Refer to “Bus.”

10 C. With CSMA/CA, your computer avoids a collision with the real data by placing dummy data on the wire first. If the dummy data collides, your computer knows that it isn’t safe to send the real information; if it doesn’t collide, then the real data is sent. Examine “CSMA/CA.”

11 B. Client-server environments are implemented for the purpose of centralized administration and security. It is much easier for an administrator to control resources if he is sitting at one computer and all users connect to that one computer. See “Server-based (client-server) networks.”

12 A. The maximum distance of UTP cable is 100 meters. Review “Twisted pair.”

13 B. With token passing, an empty token runs around the network, and when your computer wants to submit information on the wire, it fills the token with the information and releases the token onto the network. Check out “Token passing.”

14 A. Fiber optic cables send information in pulses of light on cabling with a glass core. Peruse “Fiber optic.”

15 D. 10Base5 is Thicknet that has a maximum distance of 500 meters. UTP cabling has a maximum distance of 100 meters, and Thinnet has a maximum cable distance of 185 meters. Take a look at “10 megabit Ethernet standards.”

16 C. Full-duplex devices can send and receive information at the same time. Peek at “Understanding Communication Methods.”

17 D. The 1000BaseSX Ethernet architecture can transfer information at 1 Gbps over fiber optic cabling using short distances. Look over “Gigabit Ethernet standards.”

18 B. RJ-45 connectors connect UTP cabling to the network card. Study “Twisted pair.”

19 D. Fiber optic cabling has a maximum distance of about 2 km. Refer to “Fiber optic.”

20 D. A BNC connector connects a 10Base2 cable to a network card. Examine “Connecting with Thinnet.”