Network+ CoursePrep · PDF filerelating to client connectivity,remote...

Network+ CoursePrepExamGuide

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NETWORK+ OBJECTIVES

The following descriptions of the Network+ Objective domains are taken from the Comp-TIA Web site at www.comptia.org. Each objective belongs to one of four domains (or broadareas) of networking knowledge. For example, the objective of recognizing an RJ-45 connec-tor belongs to the “Media and Topologies” domain, which accounts for 20 percent of theexam’s content.

DOMAIN 1.0: MEDIA AND TOPOLOGIES — 20 PERCENT OF EXAMINATION

This domain requires knowledge of transmission media and connector types, physical topolo-gies (such as the star topology), and access methods (such as Ethernet and Token Ring) thatmake up a network. It also includes an understanding of network connectivity devices such ashubs, routers, switches, gateways and wireless access points. Many of the topics in this domaincomply with industry standards, such as IEEE’s working group standards for Physical and DataLink layer network access.Although the topics in this domain are highly technical, they are alsorelatively straightforward.

DOMAIN 2.0: PROTOCOLS AND STANDARDS — 20 PERCENT OFEXAMINATION

This domain requires knowledge of protocols and standards, the means by which twocomputers communicate. Given that the most popular network protocol currently used onnetworks isTCP/IP, this domain pays particular attention to the protocols and subprotocols inthe TCP/IP suite of protocols. In addition to protocols, this domain covers the OSI Model, apopular theoretical construct used to describe computer-to-computer communication.Muchof the knowledge in this domain refers to networking at the most fundamental, data-bit level.

DOMAIN 3.0: NETWORK IMPLEMENTATION — 25 PERCENT OF EXAMINATION

This domain requires understanding of the most popular networking software clients andNOSs (network operating systems). It covers the features of each,plus methods for connectingmultiple types of clients with each NOS. In addition, this domain requires knowledge ofnetworking best practices to ensure that data is safe and always available and that networkaccess is never interrupted.

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DOMAIN 4.0: NETWORK SUPPORT — 35 PERCENT OF EXAMINATION

This domain requires the ability to diagnose and troubleshoot common network problemsrelating to client connectivity, remote connectivity, topology, hardware, and media. It requiresknowledge of troubleshooting utilities and methodology. This domain emphasizes practicalknowledge that will prove invaluable in a networking career.

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1.1 Recognize the following logical or physical network topologies given adiagram, schematic or description:

STAR PHYSICAL TOPOLOGYUNDERSTANDING THE OBJECTIVE

Every network depends on a physical layout, or topology.The physical topology describeshow servers, workstations, printers, and other devices are physically connected in a LAN(local-area network) or WAN (wide-area network). While most modern networkscontain a combination of topologies, all combinations rely on a few fundamental topologies:bus, star, and ring. Because each individual topology has particular advantages and disadvan-tages, different situations may require different topologies. The most common physicaltopology used on modern networks is a star topology.

WHAT YOU REALLY NEED TO KNOW◆ In a star topology, every node on the network is connected through a central

device, such as a hub, in a star configuration, as shown in the following diagram:

◆ In a star topology network, each device transmits its data to the hub, whichrepeats the data to all other devices on the segment. The recipient node then picksup the data addressed to it.

◆ Any single physical wire on a star network only connects two devices, so a cablingproblem will only affect two nodes. Devices such as workstations or printers trans-mit data to the hub, which then retransmits the data to the network segmentwhere the destination node is located, so the destination node can pick it up.

◆ Star topologies are more fault-tolerant and provide better performance than busor ring topologies. On Ethernet networks, a single cable or node fault will notimmobilize a star-wired network. However, star networks require more cabling anddevices and are generally more expensive than bus or ring networks.

◆ Star networks can be easily upgraded, moved, and interconnected with othernetworks.

◆ Star topology networks that divide workstation groups and connectivity devicesinto layers are known as hierarchical.

OBJECTIVES ON THE JOB

The star topology forms the basis of the most popular type of network in use today. Becauseit is so popular, you should be familiar with the way connectivity devices and nodes arearranged in this topology.As your experience with star topology networks increases, you willalso learn how to troubleshoot and add to them.

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4 NETWORK+ COURSEPREP

PRACTICE TEST QUESTIONS

1. Which of the following is an advantage to using star topology networks over using bus or ringtopology networks?

a. Star topology networks are more scalable.b. Star topology networks are less expensive to install.c. Star topology networks are easier to install.d. Star topology networks are more secure.

2. What would happen if a node in a star-wired Ethernet network failed?a. Performance over the entire network would suffer slightly.b. Only the failed node would be unable to transmit or receive data.c. Data could no longer be transmitted or received at any point in the network.d. The failed node would broadcast errors to the rest of the network.

3. What is the function of a hub in a star-wired network?a. to reduce RF emissions that may result in security breachesb. to increase available bandwidth by sending multiplexed signalsc. to arbitrate addressing conflicts between sending nodesd. to repeat signals to all nodes on the segment

4. In a network using the star topology, five workstations and a hub would be connected via howmany physical cables?

a. threeb. fourc. fived. six

5. In which of the following networks would it make the most sense to implement a star topology?(Choose all that apply)

a. a home network that connects two computersb. a WAN that connects freelance writers across the nationc. a LAN that connects a dozen computers in an insurance companyd. a WAN that connects multiple churches within a city

6. What would happen to a star network if one of its workgroup hubs failed?a. All nodes connected to that hub would be unable to communicate with nodes on other seg-

ments, but they could communicate with each other.b. All nodes connected to that hub would be unable to communicate with nodes on other seg-

ments as well as nodes on their own segment.c. Nodes would be able to communicate with the network, as they would automatically connect

to an alternate hub on the backbone.d. Communication on the entire LAN would halt.

7. What type of terminator is used on a star-wired network?a. 20-ohm resistorb. 50-ohm resistorc. 100-ohm resistord. Terminators are not used on star-wired networks.

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5NETWORK+ COURSEPREP

1.1 Recognize the following logical or physical network topologies given adiagram, schematic or description (continued):

BUS PHYSICAL TOPOLOGY

UNDERSTANDING THE OBJECTIVE

A bus topology is one in which multiple nodes share a single channel.By sharing that channel,they also share a fixed amount of bandwidth. Bus topologies are commonly found on olderEthernet networks using coaxial cable media.

WHAT YOU REALLY NEED TO KNOW◆ A bus topology consists of a single cable connecting all nodes on a network with-

out intervening connectivity devices and appears as follows in a network diagram:

◆ Since every node on a bus topology network shares the same channel for datatransmission, adding nodes on a bus network impairs performance.

◆ A bus topology can be considered a peer-to-peer topology because every device onthe network shares the responsibility for getting data from one point to another.

◆ Bus topologies require terminators at each end of the bus to prevent signalbounce, a phenomenon in which data travels endlessly between the two ends ofthe network.

◆ The bus topology is the least fault-tolerant of any topology, because one break inthe cable can take down the entire network, and bus topology faults are difficultto find.

◆ A bus topology is the least expensive and simplest topology to install.


If you use a bus topology, chances are you are working on an older Ethernet network usingcoaxial cable. Bear in mind that if one of the nodes fails, the entire network will loseconnectivity. For this reason, and because the addition of more nodes will cause performanceproblems, it may be wise to upgrade a bus topology network to a star topology network.

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1. On a bus topology, terminators eliminate the possibility of .a. crosstalkb. noisec. signal bounced. EMI

2. How many nodes share a single channel on a bus topology?a. all connected nodesb. onec. twod. four

3. Which type of cable are you most likely to find on networks that use a bus topology?a. UTP cableb. STP cablec. Coaxial cabled. Fiber-optic cable

4. What is one advantage of using a network based on the bus topology over a network based on thestar or mesh topologies?

a. Bus topologies are more fault tolerant.b. Bus topologies allow faster throughput.c. Bus topologies are more secure.d. Bus topologies are simpler to install and maintain.

5. What type of device is used at either end of a bus network?a. Terminatorb. Ohmmeterc. Transceiverd. Tracker

6. You are the administrator for a LAN that uses the bus topology to connect seven workstations. Eachworkstation runs Windows XP. What would you need to do if you wanted to add a workstation tothe network and enable other workstations to read data from the new workstation’s hard disk?

a. Apply shared access to the appropriate folders on the new workstation.b. Modify the sharing services parameters in the domain controller’s operating system.c. Modify the file sharing properties on each workstation on the network so that each can read

from the added workstation.d. Add the new workstation’s account to a folder-sharing group on the network.

7. What would happen to the entire network if one of the nodes in a bus-wired network failed?a. Performance would suffer slightly.b. The failed node could not transmit data, but other nodes would be fine.c. Data would no longer be transmitted to or from any node.d. Errors would be broadcast to every node.

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MESH PHYSICAL TOPOLOGY


In a LAN,a mesh topology is one in which at least some of the nodes are connected via more thanone link.In aWAN,a mesh topology is one in which some of the locations are connected via morethan one link. Mesh topologies are most commonly used in WANs.

WHAT YOU REALLY NEED TO KNOW◆ A mesh topology is one in which nodes or locations are directly interconnected

with multiple other nodes or locations on the network.◆ A network may use a full mesh topology, in which each node is connected directly

to each other node, as shown in the following diagram:

◆ Full mesh topologies are the most expensive physical topologies because theyrequire the most equipment, connectivity, setup, and maintenance. However, theyare also the most fault-tolerant physical topologies.

◆ A less expensive, yet still fault-tolerant alternative to full mesh topologies is apartial mesh topology, in which only some of the nodes on a network are directlyconnected to other nodes, as shown in the following diagram:

◆ Mesh topologies are typically used in the context of WANs. A location in a WANtopology is equivalent to a node in a LAN topology.


If you are designing a WAN that must be fault tolerant, a mesh topology is a wise choice. Indesigning a partial mesh, arrange the redundant links so that they connect the most criticallocations on the network.

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1. Which of the following advantages does a partial mesh topology provide?a. All nodes have multiple connections to the network.b. At least some nodes have multiple connections to the network.c. Any node can be taken down without affecting network performance.d. Network performance will be similar, no matter what kind of link is used between nodes.

2. Which of the following is the most fault-tolerant WAN topology?a. partial-meshb. full-meshc. ringd. bus

3. If a full-mesh WAN consists of four locations, how many separate connections does it contain?a. twob. fourc. sixd. eight

4. If a partial-mesh WAN consists of four locations, how many separate connections might it contain?(Choose all that apply.)

a. twob. threec. fourd. five

5. Which of the following organizations is most likely to use a full-mesh WAN?a. a school districtb. a regional charitable organizationc. a regional power companyd. a local chain of grocers

6. What would happen to the entire network if one of the nodes in a full-mesh WAN failed?a. Performance for all locations on the WAN would suffer.b. The failed location would be unable to transmit or receive data, but other locations could

communicate without a problem.c. Data would no longer be transmitted to or from any of the locations.d. The failed location would broadcast errors to every other location.

7. A mesh WAN could connect LANs that use the bus topology. True or False?

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RING PHYSICAL TOPOLOGY


A ring topology connects nodes using a single channel in a ring. In order to determine whichnode can transmit data at any given time, ring networks use tokens that circulate on thenetwork and are reserved by the transmitting node.

WHAT YOU REALLY NEED TO KNOW◆ In a ring topology, each node is connected to the two nearest nodes so that the

entire network forms a circle, as shown in the following diagram:

◆ Data is transmitted in one direction (unidirectionally) around the ring. Each work-station accepts and responds to packets addressed to it, then forwards the otherpackets to the next workstation in the ring.

◆ Because there are no ends to a ring network and because data stop at their desti-nation, ring networks do not require terminators.

◆ Ring topologies often use the token passing technique, in which a node thatwants to send data picks up the constantly circling token, adds its data, sends thepacket, and when the recipient accepts the packet, releases the token so that othernodes can transmit.

◆ A disadvantage of the ring topology is that one defective node can take down thenetwork.

◆ Another disadvantage with the ring topology is that, as with a bus topology, add-ing more nodes to a ring network can diminish performance.

◆ A popular hybrid topology used on Token Ring networks is the star-ring hybridtopology. In this configuration, the physical topology is a star while the logicaltopology is a ring.


If you work with a Token Ring network, bear in mind that it will use the star-ring hybridtopology, not a simple ring topology. Still, you must be aware of the scalability limitations ofthis type of topology.

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1. In which two of the following topologies will the addition of more nodes detrimentally affect thenetwork’s performance?

a. busb. starc. ringd. mesh

2. At any given time, how many tokens circulate on a simple ring network?a. oneb. fivec. tend. There are no limits on the number of tokens that may circulate.

3. What is the function of a token on a token-passing ring network?a. It signals to the rest of the network to listen for traffic.b. It signals to the rest of the network that the MAU is receiving an excessive number of errors.c. It enables multiple nodes on the network to transmit data simultaneously.d. It enables one node on the network to transmit data at any one time.

4. A modern day Token Ring network actually uses which of the following hybrid topologies?a. star-busb. ring-busc. ring-treed. star-ring

5. In how many directions is data transmitted on a ring network?a. oneb. twoc. It depends on the number of nodes on the network.d. It depends on the location of the nodes on the network.

6. What would happen to the entire network if one of the nodes in a simple ring network failed?a. Performance over the entire network would suffer slightly.b. The failed node would be affected, but other nodes would be fine.c. Data would no longer be transmitted to or from any nodes.d. Errors would be broadcast to every node.

7. What ring element must a node possess before it is able to transmit over a ring network?a. sender codeb. transcenderc. tokend. A node on a ring network can transmit at any time without restriction.

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1.2 Specify the main features of 802.2 (Logical Link Control), 802.3 (Ethernet),802.5 (Token Ring), 802.11 (wireless) and FDDI (Fiber Distributed DataInterface) networking technologies, including: Speed; Access method(CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) andCSMA/CD (Carrier Sense Multiple Access/Collision Detection)); Topology;and Media:

802.2 (LOGICAL LINK CONTROL)


Everything in the networking field, from hardware to protocols, relies on standards to ensurethat components from different manufacturers can be easily integrated. IEEE (Institute ofElectrical and Electronic Engineers) is the body that sets standards at the Physical and DataLink layers of the OSI Model for computer networking.The most well-known IEEE standardsare those set by the 802 Committee.

WHAT YOU REALLY NEED TO KNOW◆ The IEEE, or “I-triple-E,” is an international society composed of engineering

professionals. It maintains a standards board that establishes its own standards forthe electronics and computer industry and contributes to other standards-settingbodies, such as the ANSI (American National Standards Institute).

◆ IEEE’s committees set standards that apply to different layers of the OSI Model,including the Physical and Data Link layers, and therefore correspond to differentnetwork access methods and network media.

◆ The most well-known IEEE committee is the 802 committee. Among its popularstandards are 802.2, which governs the LLC (Logical Link Control) of the OSI modelData Link layer; 802.3, which governs Ethernet networks; 802.5, which governsToken Ring networks; and 802.11, which governs wireless networks.

◆ To accommodate shared access for multiple network nodes (as opposed to simplepoint-to-point communication), the IEEE expanded the OSI Model by separating theData Link layer into two sublayers: the LLC sublayer and the MAC (Media AccessControl) sublayer.

◆ The 802.2 standards apply to the LLC, the upper sublayer in the Data Link layer,which provides a common interface and supplies reliability and flow controlservices.

◆ The MAC sublayer, the lower sublayer within the Data Link layer, appends thephysical address of the destination to data frames.

◆ IEEE’s specifications for Ethernet (802.3) and Token Ring (802.5) technology applyto the MAC sublayer of the Data Link layer. Thus, the 802.2 standards are indepen-dent but work in tandem with the 802.3 and 802.5 specifications.


All modern networks rely on the foundation of 802.2 LLC standards in order to frame dataand ensure reliable delivery.You should be aware of how these standards are applied in yourparticular network, whether it uses Ethernet or Token Ring MAC sublayer standards.

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1. The 802.2 standards apply to what sublayer of the Data Link layer?a. the MAC sublayerb. the Logical Link Control sublayerc. the Access Method sublayerd. the Network Transmission sublayer

2. To which other standards body does IEEE contribute its recommendations?a. ISOb. OSIc. ITUd. ANSI

3. In what year was the IEEE 802 committee formed?a. 1980b. 1990c. 1995d. 1998

4. Which of the following MAC sublayer specifications can work with the 802.2 sublayerspecification? Choose all that apply.

a. 802.2b. 802.3c. 802.5d. 802.15

5. Which of the following functions is handled by the 802.2 sublayer?a. issuing electrical signals onto the wireb. appending a physical address to a data framec. appending a logical address to a data framed. ensuring appropriate flow control for a group of data frames

6. The 802.2 specifications apply to the lower sublayer of the Data Link layer of the OSI Model. Trueor False?

7. What was the primary reason the IEEE divided the OSI Model’s Data Link layer into two sublayers?a. to account for the variety of functions required for point-to-point data communicationb. to simplify the process of ensuring proper addressing between sending and receiving nodesc. to better articulate the difference between transmission and receptiond. to accommodate evolving encryption techniques

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1.2 Specify the main features of 802.2 (Logical Link Control), 802.3 (Ethernet),802.5 (Token Ring), 802.11 (wireless) and FDDI (Fiber Distributed DataInterface) networking technologies, including: Speed; Access method(CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) andCSMA/CD (Carrier Sense Multiple Access/Collision Detection)); Topology;and Media (continued):

802.3 (ETHERNET)

UNDERSTANDING THE OBJECTIVEIEEE 802.3 standards specify the MAC sublayer requirements for Ethernet standards, including itsnetwork access method,CSMA/CD (Carrier Sense Multiple Access/Collision Detection),whichallows multiple nodes to share a single channel on an Ethernet network.

WHAT YOU REALLY NEED TO KNOW◆ The 802.3 standards define elements of Ethernet networks in the MAC sublayer (of

the Data Link layer)◆ 802.3 specifies the CSMA/CD method of network access, allowing multiple nodes to

share a single Ethernet channel.◆ The term “Carrier Sense” refers to the fact that Ethernet NICs listen on the net-

work and wait until they detect (or sense) that no other nodes are transmittingdata over the signal (or carrier) on the communications channel before they beginto transmit. The term “Multiple Access” refers to the fact that several Ethernetnodes can be connected to a network and can monitor traffic, or access the media,simultaneously.

◆ In CSMA/CD, when a node wants to transmit data, it must first access the transmis-sion media and determine whether the channel is free. If the channel is not free, itwaits and checks again after a random (but brief) amount of time. If the channel isfree, the node transmits its data. If two nodes simultaneously check the channel,determine that it’s free, and begin to transmit, their two transmissions will inter-fere with each other; this is known as a collision. In this event, the network per-forms a series of steps known as the collision detection routine. If a station’s NICdetermines that its data has been involved in a collision, it will first propagate thecollision throughout the network by using a jamming signal, ensuring that noother station attempts to transmit. Then the NIC remains silent for a randomperiod of time. After waiting, the node will determine if the line is again available;if it is available, the line will retransmit its data.

◆ In CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance), when a node wantsto transmit data, it sends out a jamming signal, then waits a specific period of timefor all nodes to receive the jam. The node then transmits its data. During the datatransmission, if the node detects another node’s jamming signal, it stops transmit-ting, waits a random period of time, then tries to transmit again. Networks thatimplement CSMA/CA are AppleTalk and wireless 802.11 RTS/CTS.

◆ IEEE’s 802.3 standards apply to all wire-bound Ethernet network types, including10BASE-T (10 Mbps), 100BASE-TX (100 Mbps), 1000BASE-T (1 Gpbs) and 10GBASE-xR (10 Gbps) Ethernet. These networks may use bus, star, or star-wired busphysical topologies.

OBJECTIVES ON THE JOBSince the IEEE 802.3 standard forms the basis of the most popular networks in use today, youshould be thoroughly familiar with its specifications. In particular, you should understandCSMA/CD, its advantages and disadvantages, and how it pertains to network performance onall Ethernet networks.

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1. Which network access method is defined by IEEE 802.3?a. CSMA/CAb. demand priorityc. token passingd. CSMA/CD

2. A network that follows 802.3 specifications would use which of the following topologies? Chooseall that apply.

a. busb. starc. ringd. cube

3. At what sublayer of the Data Link layer do 802.3 standards operate?a. MMC sublayerb. LLC sublayerc. MAC sublayerd. Ethernet sublayer

4. In the network access method specified by 802.3, which of the following are likely to occur?a. collisionsb. sagsc. multiplexingd. token arbitrations

5. What network component is responsible for applying 802.3 standards to an electrical signal?a. RJ-45 connectorb. RJ-11 connectorc. NICd. multimeter

6. Which of the following networks would use 802.3 standards? Choose all that apply.a. 10BASE-Tb. Token Ringc. wireless LANd. 100BASE-TX

7. At what data transmission speed is a modern 802.3-based Fast Ethernet network likely to run?a. 1 Mbpsb. 4 Mbpsc. 10 Mbpsd. 100 Mbps

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802.5 (TOKEN RING)


IEEE 802.5 specifications describe the MAC sublayer elements of Token Ring networks,including its network access method known as token passing.

WHAT YOU REALLY NEED TO KNOW◆ The 802.5 standards define the MAC sublayer (of the Data Link layer) elements of

networks using the Token Ring transmission method.◆ Traditional Token Ring networks transmit data at either 4 Mbps or 16 Mbps over

shielded or unshielded twisted-pair wiring.◆ The 100 Mbps Token Ring standard, finalized in 1999, is known as HSTR (high-

speed Token Ring). HSTR can use either twisted-pair or fiber-optic cable as its trans-mission medium. While it is as reliable and efficient as Fast Ethernet, it is lesscommon because of its more costly implementation.

◆ Token Ring networks use the token-passing network access method and a star-ringhybrid physical topology.

◆ According to the 802.5 standards, on a Token Ring network, one workstation,called the active monitor, acts as the controller for token passing. Specifically, theactive monitor maintains the timing for ring passing, monitors token and frametransmission, detects lost tokens, and corrects errors when a timing error or otherdisruption occurs. Only one workstation on the ring can act as the active monitorat any given time.

◆ In token passing, a 3-byte token circulates around the network. When a station hassomething to send, it picks up the token, changes it to a frame, and then adds theheader, information, and trailer fields. Each node reads the frame as it traversesthe ring to determine whether it is the intended recipient. If a node is the recipi-ent, it picks up the data, then retransmits the frame to the next node on the ring.When the frame reaches the originating station, it reissues a free token that canthen be reused.

◆ The token-passing control scheme ensures high data reliability (no collisions) andan efficient use of bandwidth. It also does not impose distance limitations on thelength of a LAN segment, unlike CSMA/CD.


In the early 1990s, the Token Ring architecture competed strongly with Ethernet to be themost popular logical topology. Since that time, the economics, speed, and reliability ofEthernet have greatly improved, making Token Ring less desirable.Thus, you are much morelikely to work with Ethernet networks than Token Ring networks.

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1. Which of the following data transmission speeds would be used on 802.5 networks? Choose allthat apply.

a. 1 Mbpsb. 4 Mbpsc. 10 Mbpsd. 16 Mbps

2. What network access method is specified by the 802.5 standard?a. CSMA/CAb. demand priorityc. token-passingd. CSMA/CD

3. What type of media could be used by a network that relies on the 802.5 standard? Choose allthat apply.

a. coaxial cableb. UTPc. STPd. single-mode fiber

4. At which sublayer of the Data Link layer do 802.5 standards operate?a. MMC sublayerb. MAC sublayerc. LLC sublayerd. TMC sublayer

5. What network component is responsible for applying 802.5 standards to an electrical signal?a. RJ-45 connectorb. RJ-11 connectorc. cablingd. NIC

6. Why is the 802.3 standard more popular than the 802.5 standard?a. The 802.3 standard is more reliable than the 802.5 standard.b. The 802.3 standard is not subject to collisions and, therefore, suffers less data corruption than

the 802.5 standard.c. The 802.3 standard can offer greater speed at lower overall cost than can the 802.5 standard.d. The 802.3 standard is more compatible with evolving security standards than the 802.5

standard.

7. What type of physical topology would be used on an 802.5 network?a. busb. star-wired busc. star-wired ringd. cube

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802.11 (WIRELESS)UNDERSTANDING THE OBJECTIVE

The IEEE 802.11 group of standards specifies wireless access methods using one or morefrequency bands for LAN communications.Wireless standards were first proposed by IEEE in 1997with the aim of facilitating interoperability between different manufacturers’ wireless networkingdevices.

WHAT YOU REALLY NEED TO KNOW◆ The IEEE 802.11 standards define protocols necessary for atmospheric-based trans-

mission between nodes on a LAN. As with 802.3 and 802.5, the 802.11 specifica-tions apply to data transmissions between the MAC sublayer and the LLC sublayerof the Data Link layer.

◆ Typically, wireless LAN communication is issued by a radio NIC to an access point,such as a base station. Application of the 802.11 standards takes place at the NIC.

◆ The 802.11 standards support the continuation of service according to other MACsublayer standards, such as Ethernet (802.3). This enables those parts of a LAN thatrely on wireless transmission to connect with a wire-bound Ethernet LAN, forexample.

◆ Wireless standards are designed to be used within buildings, such as warehouses,hospitals, office buildings, malls, and residences. The 802.11 specifications are par-ticular to LANs, but may be used in small WANs, such as outdoor parks.

◆ Wireless LANs transmit data across a broad area (unlike wire-bound LANs). There-fore, data privacy is a concern with this type of transmission. Using spread-spectrum radio frequency and standard security measures addresses this concern.

◆ The 802.11 standards use the CSMA/CA network access method, not CSMA/CD, asin Ethernet. Nodes using CSMA/CA signal their intent to transmit before actuallydoing so. In this way, collisions and the need for data retransmittals are (mostly)avoided.

◆ The 802.11 base standard has been enhanced in several implementations, the mostcommercially popular of which are: 802.11a, which operates in the frequency range5.725 to 5.850 GHz at up to 54 Mbps; 802.11b, which operates in the frequencyrange 2.400 to 2.4835 GHz at up to 11 Mbps; and, 802.11g, which operates in thefrequency range 2.4 – 2.4835 GHz up to 54 Mbps.

◆ The spectrum range for 802.11 spread spectrum transmission was selected becauseit is available license-free in most parts of the world.

OBJECTIVES ON THE JOBAlthough IEEE’s 802.11 standards have been established for some years, wireless networkingequipment is still evolving.When specifying or purchasing such equipment, it is best to be certainthat it is 802.11b- or 802.11g-compliant and interoperable with your existing networkcomponents. Some vendors offer equipment that is both 802.11b- and 802.11g-compliant.

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1. What networking component is responsible for applying 802.11 standards to an electrical signal?a. NICb. portalc. base stationd. antenna

2. Which of the following media is the least secure?a. fiber-optic cableb. UTPc. direct infraredd. spread-spectrum RF

3. What is the theoretical maximum throughput of an 802.11b wireless LAN?a. 2.4 Mbpsb. 5 Mbpsc. 11 Mbpsd. 54 Mbps

4. Which radio frequency band is specified for use by the 802.11b standard?a. 1.5 GHzb. 2.4 GHzc. 5.5 GHzd. 6.2 GHz

5. Which of the following network access methods do 802.11 devices use?a. CSMA/CAb. demand priorityc. token-passingd. CSMA/CD

6. In which of the following situations would the use of 802.11 standards be most appropriate?a. a WAN that connects 25 university department buildingsb. a LAN that connects 50 inventory control personnel in a warehouse to a database serverc. a WAN that connects 120 mobile sales people with their corporate headquartersd. a MAN that connects four bank branches across a large metropolitan area

7. At what layer of the OSI Model do 802.11 standards operate?a. Physical layerb. Data Link layerc. Network layerd. Transport layer

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1.2 Specify the main features of 802.2 (Logical Link Control), 802.3 (Ethernet),802.5 (Token Ring), 802.11 (wireless) and FDDI (Fiber Distributed DataInterface) networking technologies, including: Speed; Access method(CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) andCSMA/CD (Carrier Sense Multiple Access/Collision Detection); Topology;and Media (continued):

FDDI (FIBER DISTRIBUTED DATA INTERFACE)


FDDI (Fiber Distributed Data Interface) is a logical topology whose standard was originallyspecified by ANSI in the mid-1980s. It uses a double fiber-optic ring to transmit data at speedsof up to 100 Mbps.

WHAT YOU REALLY NEED TO KNOW◆ FDDI is a logical topology whose standard was originally specified by ANSI in the

mid-1980s and later refined by ISO.◆ FDDI (pronounced “fiddy”) uses a double ring of multimode or single-mode fiber

to transmit data at speeds of up to 100 Mbps.◆ FDDI was developed in response to the throughput limitations of Ethernet and

Token Ring technologies used at the time. In fact, FDDI was the first network trans-port system to reach the 100 Mbps threshold. For this reason, you will frequentlyfind it supporting network backbones that were installed in the late 1980s andearly 1990s.

◆ A popular implementation of FDDI involves connecting LANs located in multiplebuildings, such as those on college campuses. FDDI links can span distances as faras 62 miles.

◆ Because Ethernet technologies have developed faster transmission speeds and aremore compatible with other existing network technologies, FDDI is no longer themuch-coveted technology that it was in the 1980s.

◆ Its reliance on fiber-optic cable ensures that FDDI is more reliable and more securethan transmission methods that depend on copper wiring. Another advantage ofFDDI is that it works well with Ethernet 100BASE-TX technology.

◆ One drawback to FDDI technology is its high cost relative to Fast Ethernet (costingup to 10 times more per switch port than Fast Ethernet).

◆ FDDI is based on a ring physical topology similar to a Token Ring network. It alsorelies on the same token-passing routine that Token Ring networks use. However,unlike Token Ring technology, FDDI runs on two complete rings. During normaloperation, the primary FDDI ring carries data, while the secondary ring is idle. Thesecondary ring will assume data transmission responsibilities should the primaryring experience Physical layer problems.


If you work on a university or other campus-wide network,you may be required to work withFDDI technology. FDDI is a separate standard from Ethernet or Token Ring, and as such, ituses different network access methods, connectivity equipment, and signaling techniques.

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1. On what type of physical topology is a FDDI network based?a. starb. ringc. busd. tree

2. Why is FDDI considered more reliable than Ethernet or Token Ring?a. It uses more sophisticated error-checking protocols.b. It uses more reliable sequencing and flow-control techniques.c. It is designed to better withstand data collisions.d. It uses duplicate sets of transmission media.

3. On which of the following networks is FDDI most likely to be found today?a. a VPN that connects 120 satellite sales offices with a company’s headquartersb. a LAN that connects 200 workstations, 5 servers, and 15 printers within an office buildingc. a WAN that connects seven manufacturing plants across the nationd. a WAN that connects 18 buildings on a college campus

4. Which of the following agencies originally specified the FDDI standard?a. ANSIb. IEEEc. ISOd. ITU

5. Which of the following network technologies is the most compatible with FDDI?a. Token Ringb. 10BASE-Tc. 100BASE-TXd. 100BASE-FX

6. Why is Ethernet preferred over FDDI for modern networks?a. It can achieve faster throughput at lower overall cost.b. It works better with today’s popular TCP/IP protocol.c. It is more reliable.d. It is better suited for evolving security measures.

7. Which of the following would be found on a FDDI network?a. collisionsb. tokensc. amplifiersd. UTP cable

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1.3 Specify the characteristics (for example: speed, length, topology, and cabletype) of the following cable standards:

10BASE-T AND 10BASE-FLUNDERSTANDING THE OBJECTIVE

The Ethernet (802.3) standard, including the specification of CSMA/CD as a network accessmethod, applies to several types of networks, including 10BASE-T and 10BASE-FL.

WHAT YOU REALLY NEED TO KNOW◆ All types of wire-bound Ethernet use the CSMA/CD network access method.◆ 10BASE-T uses baseband transmission (thus the “BASE” in its name) and twisted-

pair cabling (thus, the letter “T” in its name) and a star topology to transmit dataat 10 Mbps (thus, the “10” in its name).

◆ As with all Ethernet networks, 10BASE-T follows a set of communication rulescalled Carrier Sense Multiple Access with Collision Detection (CSMA/CD). CSMA/CDallows multiple nodes to share one data channel while minimizing the possibilitiesfor data collisions.

◆ 10BASE-T networks use unshielded twisted-pair, including Category 3, 4, 5, andhigher cables. Unshielded twisted-pair is the same kind of wiring used for tele-phone connections, and for this reason, 10BASE-T networks usually fit well into anorganization’s existing physical infrastructure.

◆ Nodes on a 10BASE-T Ethernet network connect to a central hub or repeater in astar fashion. Typical of a star topology, a single network cable only connects twodevices. This characteristic makes 10BASE-T networks more fault tolerant than olderEthernet networks, which used the bus topology.

◆ Because 10BASE-T networks use a star topology, they are easier to troubleshootthan older Ethernet bus networks, because you can better isolate problems.

◆ Each node on a 10BASE-T network uses RJ-45 connectors to connect the networkcable with the NIC at the workstation end and with the hub at the network end.

◆ The maximum distance a 10BASE-T segment can traverse is 100 meters.◆ 10BASE-T networks may connect up to five network segments with up to four con-

nectivity devices. Only three of the connected segments can contain hosts. Thisguideline, known as the 5-4-3 rule, is intended to minimize signal delay betweennodes. However, on a switched Ethernet network the rule would not apply becauseswitches are capable of buffering signals and all network nodes have simultaneousaccess to the switched Ethernet LAN. The maximum segment length on a 10BASE-Tnetwork is 100 meters.

◆ 10BASE-FL is the most popular implementation of 10 Mbps fiber technology, fre-quently used in conjunction with 10BASE-T networks to function as an extendeddistance backbone carrier.

◆ 10BASE-FL normally uses 62.5-micron duplex multimode fiber-optic cable to estab-lish segments lengths up to 2 km with a maximum of two devices per segment.10BASE-T to 10BASE-FL media converters are used to produce a fiber-optic linkbetween the twisted-pair cable and the fiber-optic cable in a network (hence thedesignation FL for fiber link).

OBJECTIVES ON THE JOBOn any modern network, you will probably find some type of Ethernet technology. Youshould be familiar with the differences between Ethernet versions, and most importantly,which versions are incompatible with one another.

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1. What type of cable media does 10BASE-FL use?a. CAT3 cableb. CAT5 cablec. SMF (single-mode Fiber) cabled. MMF (multimodefiber) cable

2. All wired Ethernet technologies use CSMA/CD. True or false

3. 10BASE-T and 10BASE-FL share the same maximum segment length. True or false

4. Which of the following Ethernet technologies uses fiber-optic cable? Choose all that apply.a. FDDIb. Token Ringc. 10BASE-Td. 10BASE-FL

5. Which of the following Ethernet technologies uses a star-wired bus physical topology? Choose allthat apply.

a. FDDIb. Token Ringc. 10BASE-Td. 10BASE-FL

6. Which of the following IEEE standards specifies CSMA/CD?a. 802.2b. 802.3c. 802.5d. 802.11

7. Which of the following apply to both 10BASE-T and 10BASE-FL? Choose all that apply.a. their network access method is CSMA/CDb. their maximum throughput is 10 Mbpsc. they both use two wire pairsd. they both transmit electrical pulses

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1.3 Specify the characteristics (for example: speed, length, topology, and cabletype) of the following cable standards (continued):

100BASE-TX AND 100BASE-FXUNDERSTANDING THE OBJECTIVE

Both 100BASE-TX and 100BASE-FX are Ethernet specifications that use baseband transmissionand enable data rates of up to 100 Mbps. 100BASE-TX networks can use unshielded or shieldedtwisted-pair cable, both of which require RJ-45 connectors. 100BASE-FX uses multimode fibercable and either SC, ST, LC, or MT-RJ fiber connectors. 100BASE-TX is limited to a maximumsegment length of 100 meters and uses a star topology. 100BASE-FX has a maximum segmentlength of 400 m with a maximum of two repeaters allowed to connect segments.

WHAT YOU REALLY NEED TO KNOW◆ 100BASE-TX achieves its speed by sending the signal 10 times faster than 10BASE-T

and condensing the time between digital pulses as well as the time a station mustwait and listen for a signal.

◆ 100BASE-TX is part of the IEEE 802.3u Ethernet specification requiring CAT5 orhigher unshielded twisted-pair cabling, using two cable pairs. 100BASE-TX iscapable of full duplexing.

◆ 100BASE-FX is also an IEEE 802.3u version of Ethernet, but uses fiber-optic cable asits transmission medium. It uses two strands of multimode fiber cable per link. Onestrand is used for data transmission, while the other strand is used for reception,making 100BASE-FX a full-duplex technology.

◆ The 100BASE-FX standard uses a star topology, with its repeaters connectedthrough a bus. The star topology makes this standard highly scalable andfault-tolerant.

◆ 100BASE-FX and 100BASE-TX, both of which are considered Fast Ethernet, maycoexist on the same network. They both use the standard CSMA/CD Ethernet mediaaccess method.

◆ Organizations converting from UTP to fiber media can combine 100BASE-TX and100BASE-FX within one network. For this to occur, connectivity devices must haveboth RJ-45 and SC or ST ports. Alternatively, a 100BASE-TX to 100BASE-FX mediaconverter may be used at any point in the network to interconnect the differentmedia and convert the signals of one standard to signals that work with the otherstandard.

◆ Since fiber does not conduct electrical current to transmit signals, 100BASE-FX isunaffected by EMI.

◆ 100BASE-FX is more expensive than 100BASE-TX because the media, the NICs andthe connectivity devices are all more expensive for the fiber based system. Also,hiring skilled fiber-optic cable installers costs more than hiring twisted-pair cableinstallers.

OBJECTIVES ON THE JOBModern networks often can combine the functionality of 10BASE-T, 100BASE-TX and100BASE-FX on the same network. Bear in mind that all NICs and ports on such connec-tivity devices as routers or hubs must be compatible with the transmission technology yournetwork uses (such as 10BASE-T). Even if your network runs only 10BASE-T now, it is wiseto purchase devices that can automatically sense whether the network is running at a higherthroughput rate (speed) and then adjust to that rate. If you work on a network that uses100BASE-FX, it is likely that some parts of the network will be fiber-based (such as thebackbone) and others will be UTP-based 100BASE-TX technology (such as workstationconnections).You should be familiar with integrating the different types of hardware requiredfor these different Fast Ethernet standards.

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1. What is the maximum segment length for a 100BASE-TX network?a. 100 metersb. 85 metersc. 10 metersd. 10 feet

2. Which type of cable is used on a 100BASE-TX network?a. CAT5b. CAT3c. CAT2d. fiber-optic

3. What does the “BASE” in 100BASE-TX represent?a. basicb. basalc. base 10d. baseband

4. What kind of connector is used in a 100BASE-FX network?a. SCb. RJ-11c. RJ-45d. RJ-52

5. On what topology are 100BASE-TX networks based?a. busb. starc. ringd. mesh

6. Which IEEE specification standardizes 100BASE-FX technology?a. IEEE 802.2b. IEEE 802.3uc. IEEE 802.5d. IEEE 802.11

7. What is the maximum segment length of a 100BASE-FX network?a. 100 metersb. 400 metersc. 1000 metersd. 2000 meters

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1000BASE-T, 1000BASE-CX, 1000BASE-SX AND 1000BASE-LX

UNDERSTANDING THE OBJECTIVE1000BASE-T, 1000BASE-CX, 1000BASE-SX and 1000BASE-LX are Ethernet transmissiontechnologies that can achieve data throughput rates up to 1000 Mbps (1 Gigabit).

WHAT YOU REALLY NEED TO KNOW◆ Like Fast Ethernet, a fiber-based, 1 Gigabit Ethernet network uses the CSMA/CD

network access method, relies on the star physical topology, and is capable of fullduplexing.

◆ 1000BASE-T is specified in the IEEE 802.3ab (Ethernet) standard. It uses basebandtransmission, twisted-pair cabling, and transmits data at 1000 Mbps.

◆ 1000BASE-T requires CAT5 or better cable and operates over all four cable pairsusing an advanced modulation technique to achieve gigabit throughput rates.

◆ 1000BASE-CX is specified in the IEEE 802.3z standard and uses a copper cable (thus,the “C” in the name). It is intended for short haul distances (25 meters or less)within wiring closets, using a special shielded copper cable called twinax. To date,this standard has rarely been implemented.

◆ 1000BASE-SX and 1000BASE-LX are the fiber-optic specifications standardized underIEEE 802.3z. The “S” in 1000BASE-SX indicates the use of short wavelength lasers(770 to 860 nanometers) to send light signals through the multimode fiber-opticcable. The “L” in 1000BASE-LX indicates the use of long wavelength lasers (1270 to1355 nanometers) to send light signals through the fiber. 1000BASE-LX is standard-ized on both single-mode and multimode fiber-optic cable.

◆ A longer wavelength, such as that of 1000BASE-LX, can transmit signals overgreater distances than the short wavelength light signals. The tradeoff, however, isthat more costly transceivers make 1000BASE-LX more expensive to implement on anetwork.

◆ Using multimode fiber cable, IEEE specifies a minimum distance of 550 meters for1000BASE-SX. Using single-mode fiber, 1000BASE-LX has a minimum distance spanof 5000 meters. These are conservative minimum distances specified by IEEE whichcould be exceeded by three or four times. However, most network administratorsuse the IEEE minimum figures as their maximum, to be on the safe side.

◆ Both 1000BASE-SX and 1000BASE-LX are compatible with 1000BASE-T and can beinterconnected on a network using media converters.

◆ The 1- and 10-Gigabit technologies compete directly with other fast networkingsolutions, such as ATM (Asynchronous Transfer Mode).

OBJECTIVES ON THE JOBMost networks today use some form of Fast Ethernet over copper or fiber-optic media.However, Fast Ethernet technologies are being replaced by Gigabit Ethernet, which is capableof data transmission rates up to 1 Gbps. Most new desktop computers come with gigabitEthernet NICs built right into the motherboard of the computer. Gigabit Ethernet on thecorporate network backbone is a reality and 10Gbps Ethernet implementation is not far off.As a network administrator should be familiar with the best practices for integrating Gigabittechnology into your Fast Ethernet network.

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1. What type of fiber-optic cable can be used with 1000BASE-SX?a. multimode fiberb. single-mode fiberc. both multimode and single-mode fiberd. it does not use fiber-optic cable

2. What is the most likely network scenario for using 1000BASE-CX Ethernet?a. To connect two corporate buildings on a campus.b. To connect two routers in a LAN closet.c. To connect a workstation to a central LAN closet.d. To connect two distant corporate regional offices to a corporate headquaters.

3. What is the IEEE minimum segment length on a 1000BASE-SX network?a. 10 metersb. 85 metersc. 100 metersd. 550 meters

4. Which of the following network access methods is used by 1000BASE-LX?a. demand priorityb. CSMA/CAc. CSMA/CDd. token-passing

5. What type of connector is used on a 1000BASE-T network?a. RJ-11b. RJ-45c. AUId. SC

6. Which of the following cable types must be used for a 1000BASE-T network?a. CAT6b. CAT5ec. CAT5d. CAT3

7. How many wire pairs does the 1000BASE-T standard require?a. oneb. twoc. fourd. eight

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10GBASE-SR, 10GBASE-LR, AND 10GBASE-ERUNDERSTANDING THE OBJECTIVE

Through its 802.3ae project, IEEE established specifications for an Ethernet version that runs at 10Gbps, called 10 Gigabit Ethernet.The 10 Gigabit Ethernet standard encompasses media types forLAN, MAN and WAN implementation and is based entirely on the use of fiber-opticcable—although another IEEE working group is studying the possible standardization of 10Gigabit Ethernet over twisted-pair cable.Three IEEE 802.3ae standards that have gained com-mercial popularity are: 10GBASE-SR, 10GBASE-LR, and 10GBASE-ER.

WHAT YOU REALLY NEED TO KNOW◆ The 10 Gigabit Ethernet standards, designated “R”, all share a common family of

physical layer implementations for imparting light signals to the fiber-optic cable.◆ 10GBASE-SR Ethernet has been standardized over relatively short distances

although it could be deployed over a longer range. The “S” designation refers tothe “short” wavelength (850 nanometers). 10GBASE-SR is intended for use in hori-zontal wiring, building backbone and campus backbone environments. It supportsmultimode fiber-optic cable types of 50 and 62.5 microns, and depending on themodal bandwidth (MHz-km), has operating ranges up to 82 meters (at 500MHz*km) and 2000 meters (at 2000MHz*km).

◆ 10GBASE-LR Gigabit Ethernet has been standardized over longer distances than10GBASE-SR. The “L” designation refers to the “long” wavelength (1310nanometers). 10GBASE-LR is intended for use in horizontal wiring, building back-bone and campus backbone environments. It supports multimode fiber types of 50and 62.5 microns or single-mode 10 micron fiber, and has an IEEE minimum speci-fied operating range of 2 meters to 10 km. (Although this is a “minimum” stan-dardized range most conservative network administrators treat it as a maximumwhen configuring their networks.)

◆ 10GBASE-ER Gigabit Ethernet has the longest standardized range of all of the“10GBASE-R” series versions. The “E” designation refers to the “extra long” wave-length (1550 nanometers). 10GBASE-ER is intended for use in horizontal wiring,building backbone and campus backbone environments. It supports single-modefiber 10 microns, and has an IEEE minimum specified operating range of 2 metersto 402 km. (Although this is a “minimum” standardized range most conservativenetwork administrators treat it as a maximum when configuring their networks.)

◆ 10 Gigabit Ethernet is defined by IEEE’s 802.3ae committee.◆ A 10 Gigabit Ethernet network using fiber-optic cable requires either SC or ST con-

nector types.◆ The 10 Gigabit Ethernet Technology competes directly with other fast networking

solutions, such as ATM.

OBJECTIVES ON THE JOB10 Gigabit Ethernet is well suited to running a vertical backbone through an entire multi-storybuilding or connecting multiple buildings on a single campus.Although this scheme would notcurrently be appropriate for single network segments connecting workstations to hubs,PCs will beequipped with adequate hardware and processing power to take advantage of 10 Gigabit Ethernet.

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1. Which of the following media is for 10 Gigabit Ethernet? (Choose all that apply)a. coaxial cableb. UTPc. STPd. fiber-optic cable

2. Which of the following IEEE committees is responsible for establishing 10 Gigabit Ethernetstandards?

a. 802.3aeb. 802.3zc. 802.5d. 802.11b

3. Which of the following network access methods does a 10 Gigabit Ethernet network use?a. CSMA/CDb. CSMA/CAc. demand priorityd. token-passing

4. Which of the following technologies compete directly with 10 Gigabit Ethernet?a. FDDIb. Token Ringc. SONETd. ATM

5. What is the segment for a 10GBASE-LR Gigabit Ethernet network?a. 2 to 50 metersb. 2 to 550 metersc. 2 to 5000 metersd. 2 to 10000 meters

6. What part of a network is most likely to use 10 Gigabit Ethernet?a. work areab. wiring closetc. backboned. drop cables

7. Which principal characteristic differentiates the versions SR, LR and ER of 10 Gigabit Ethernet?a. maximum throughput capacityb. wavelength of propagated lightc. CSMA/CD versus CSMA/CA access technologyd. Their characteristics are all the same. Any differences are for marketing purposes only and are

not technical differences.

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1.4 Recognize the following media connectors and describe their uses:

RJ-11 (REGISTERED JACK-11), RJ-45 (REGISTERED JACK-45), AND F-TYPE


Networks will typically use of many different types of cabling and connectors to bind theircomplex equipment together. The most common types of cable are copper twisted-pair andfiber-optic cable. Many networks include coaxial cable for certain functions. Different Ethernettechnologies require different connectors.The most common is the RJ-45 connector, used on10BASE-T, 100BASE-TX and 1000BASE-T LANs. RJ-11 connectors are used as telephonecable connectors. F-Type connectors are used as coaxial cable connectors.

WHAT YOU REALLY NEED TO KNOW◆ Connectors are the pieces of hardware that connect the wire to a network device.

Every networking medium requires a specific kind of connector. The types of con-nectors you use will affect the cost of installing and maintaining the network, theease of adding new segments or nodes to the network, and the technical expertiserequired to maintain the network.

◆ RJ-11 (registered jack-11) is the standard inter-face for phone (or modem) connections and isillustrated at right, with a front and side view,respectively.

◆ An RJ-11 jack contains four or six wires. Prior to the advent of CAT5 cabling, RJ-11plugs and jacks with CAT3 cable were used for LAN communications as well asphone communications. The RJ-11 LAN and phone wiring schemes are not compat-ible and cannot be interchanged.

◆ RJ-45 (registered jack-45) identifies the Ethernet 10BASE-T, 100BASE-TX and1000BASE-T interfaces.

◆ An RJ-45 jack, illustrated at right with afront and side view, respectively, typicallycontains eight color coded wires (fourwire pairs) and looks like a large tele-phone jack.

◆ The commonly accepted standard for wiring the color coded RJ-45 jack is EIA/TIA568, either A or B (Electronic Industries Alliance/Telecommunications IndustryAssociation). The wire colors are orange, green, blue and brown, each with apaired striped wire (for example: orange and orange/white)

◆ The F-Type connector is used to terminate coaxial cable and may be found on olderLAN segments where that type of cabling might have been used. It is also suitablefor high-speed coaxial broadband video, data and telephone applications where ahigh degree of EMI protection is required.

◆ F-Type connectors are threaded and screw together like a nut and boltassembly as illustrated below. The pin of the connector, shown at right, isactually the center conductor core of the coaxial cable.


Most modern networks use twisted-pair copper wire with RJ-45 connectors.You should be ableto recognize these plugs, and terminate a UTP patch cable with one,using the proper networkingtools. Often you will find dual purpose wall plates with a combination of RJ-45 and RJ-11receptacles, or perhaps even a combination of RJ-45, RJ-11 and F-Type receptacles.

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1. What type of technology is mostly likely to use an RJ-11 interface?a. LANb. telephonec. FDDId. WAN

2. What type of UTP could be used on a legacy LAN that had RJ-11 connectors on the ends of itspatch cables?

a. CAT3b. CAT5c. CAT6d. CAT7

3. How many wire pairs are typically terminated in an RJ-45 connector?a. twob. threec. fourd. five

4. What kind of connector would you find on the end of a CAT5e patch cable?a. RJ-11b. RJ-45c. SCd. ST

5. How many colors are specified in the EIA/TIA 568 wiring stanadard?a. twob. fourc. sixd. eight

6. What type of connection mechanism is used with an F-Type connector?a. friction fit connectionb. snap on connectionc. quarter twist connectiond. screw on connection

7. The F-Type connector is commonly found on networks using UTP cabling. True or false

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1.4 Recognize the following media connectors and describe their uses(continued):

ST (STRAIGHT TIP) AND SC (SUBSCRIBER CONNECTOR OR STANDARD CONNECTOR)


Networks that use fiber-optic cabling may use any of several different types of connectors.Currently, the two most popular connector types for fiber-optic–based networks are ST andSC connectors.

WHAT YOU REALLY NEED TO KNOW◆ An ST (straight tip) connector terminates multimode fiber media and is illustrated

below, with a front and side view, respectively. It uses a bayonet type mount forconnection.

◆ An SC (subscriber connector or standard connector) connector terminates multi-mode and single-mode fiber media and is illustrated below, with a front and sideview, respectively. It uses a snap fit for connection.

◆ ST and SC connectors are used with fiber-based networks, such as 100BASE-FX.◆ When used with 100BASE-FX networks, each cable is terminated with a pair of SC

or ST connectors, as illustrated below. One of the connectors handles data trans-mission while the other handles data reception, allowing for a full-duplexconnection.

◆ Although fiber-optic cable may be terminated with one of several differenttypes of connectors, SC or ST connectors are the most popular ones in use onmodern LANs.


Bear in mind that most networks currently use fiber-based technologies only on parts of theirnetworks, and 100BASE-FX is likely to coexist with 100BASE-T on the same network.Whencombining 100BASE-FX and 100BASE-T technologies on the same network, you must useequipment capable of accepting both SC or ST connectors and RJ-45 connectors.

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1. Why do ST connectors terminate in pairs?a. Half of the pair is used for transmission, while the other half is used for reception.b. Half of the pair is used for transmission and reception, while the other half is used as a fail-

over cable for greater reliability.c. Both connectors in the pair are used to transmit and receive data simultaneously, resulting in

higher throughput.d. One-half of the pair is used for CSMA/CD network access and the other half is used for

CSMA/CA network access.

2. Which of the following types of networks might use an SC connector?a. 10BASE-Tb. 1000BASE-Tc. 100BASE-TXd. 100BASE-FX

3. Which of the following connectors is most likely to be found on a network that uses STconnectors?

a. RJ-11b. RJ-45c. F-Typed. none of the above

4. A network could use both ST and SC connectors. True or False?

5. What kind of fiber-optic cable is likely to be found inside an ST connector?a. duplex-modeb. single-modec. iso-moded. multimode

6. Which of the following physical topologies would most likely be used with SC and ST connectors?a. busb. star-wired busc. star-wired ringd. ring

7. ST and SC connectors are the only types of connectors that may be used on 100BASE-FX networks.True or False?

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IEEE 1394 (FIREWIRE) AND USB (UNIVERSAL SERIAL BUS)

UNDERSTANDING THE OBJECTIVEPeripheral bus standard jacks such as IEEE 1394 (FireWire) and USB (universal serial bus) canbe used in a networking environment to connect peripheral hardware devices such as NICs.These connectors allow for easy installation of external NICs, frequently on a hot swappable,plug-and-play basis (depending on the computer’s operating system).

WHAT YOU REALLY NEED TO KNOW◆ FireWire was introduced by Apple Computer and standardized as IEEE 1394

standard in 1995. It is a common installation jack on both Macintosh computersand PCs.

◆ Traditional FireWire connections support a maximum of 400 Mbps. However, anewer version of the standard supports potential throughput rates of 3 Gbps.

◆ FireWire can be used with computers to connect a variety of peripheral devices,including digital cameras, VCRs, external hard drives, and CD-ROMs. It can also beused to connect two or more computers on a small network using a bus topology.Such a network can support a maximum of 63 devices, with no more than 4.5meters between devices, and with an overall maximum network length of 72meters end to end.

◆ FireWire connectors come in 4-pin and 6-pin version. The 6-pin version uses 2 pinsto supply power to the peripheral device and is the connector that is used mostlyfrequently for interconnecting computers. FireWire connectors are small and theircables are thin. Both 4-pin and 6-pin versions are illustrated below.

◆ USB connectors are more commonly found on PCs than are FireWire connectors.USB is a standard interface for many peripheral devices, such as modems, mice,audio players, scanners, external hard drives, and NICs. The original USB standardwas developed in 1995, and since 1998 USB connectors have been supplied asmotherboard connectors on most laptop and desktop computers.

◆ There are two USB standards currently in use. USB 1.1has a maximum data transferrate of 12 Mbps. USB 2.2 has a maximum data transfer rate of 480 Mbps. Thephysical configuration of both connectors is identical. Peripheral devices rated atUSB 2.0 can work on a USB1.1 connector, but only at the slower 12 Mbps speed. Atypical USB plug and receptacle illustrated below.

OBJECTIVES ON THE JOBUSB connections are very common on PC based networks, particularly on peripheral devices.Newer desktop computer cases have front-mounted USB 2.0 ports. On older devices, thesemounts are found on the back. The solution for making the back-mount connections moreconvenient to the user is to run a USB cable from the back of the machine to the desktop.You arenot likely to find or use peripheral mount NICs on desktop computers.These will most often beused on laptop machines.

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1. FireWire was first introduced for which computer system?a. UNIXb. Windows 2000c. Macitoshd. Linux

2. Which type of jack is used with FireWire and USB plugs?a. serial busb. parallel portc. 9 pin seriald. 25 pin serial

3. What identifying number has IEEE given to FireWire standard?a. IEEE 1249b. IEEE 1349c. IEEE 1394d. IEEE 1934

4. What principal feature differentiates USB 1.1 and USB 2.0?a. speedb. cable lengthc. connector sized. There is no difference. They are essential the same.

5. The current version of FireWire has a higher maximum throughput that USB 2.0. True or False?

6. What is the main purpose of the extra 2 pins in the 6-pin FireWire connector?a. They allow for duplex data transmission.b. They provide for a high bandwidth.c. They supply power to connected devices.d. They provide a more secure connection.

7. In which of the following connections are you most likely to encounter a FireWire or USBconnection?

a. between two switches on a network backboneb. between an external hard drive and a laptop computerc. between a network swith and a routerd. between a keyboard and a computer

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FIBER LC (LOCAL CONNECTOR) AND MT-RJ(MECHANICAL TRANSFER REGISTERED JACK)


As networks mature and data transfer rates accelerate new innovations are becoming available tonetwork administrators almost daily. Because fiber-optic cable is becoming less expensive as analternative to copper cable for high speed network traffic,newer methods of cable termination arebeing offered as alternatives to SC and ST.Two of the more popular alternatives are the LC (localconnector) and the MT-RJ (mechanical transfer registered jack) connectors.They offer a smallerprofile and generally easier manageability and maintainability in the network environment.Because of their generally compact size, these newer connectors have been dubbed (SFF) smallform factor connectors.

WHAT YOU REALLY NEED TO KNOW◆ LC is a newer type of connector that uses a ceramic ferrule that is about half the

size of that used by the ST connector. This smaller LC connector allows for a higherdensity of connectors at termination points such as wall plates and LAN closets. Itis popular for use with both single-mode and multimode fiber cable.

◆ The LC connector has an RJ-45 style snap-in interface. It is used in a variety ofapplications where high bandwidth signal delivery is essential, such as Gigabit Eth-ernet, video, and multi-media. Duplex (on the left) and simplex (on the right) con-nectors are illustrated below.

◆ The TIA/EIA-604-12 standard provides a set of minimum attributes for the commer-cial production of MT-RJ connectors. The MT-RJ connector has a small form andhouses two strands of multi-mode fiber in a single polymer ferrule, giving duplexfunctionality. Because of the two strand configuration, it is a bit wider than the LC.

◆ The difficulty of assembling cables in the field is a big problem associated withfiber cable maintenance. To minimize this problem, the MT-RJ connector wasdesigned as a no-epoxy, no-polish type of connector. An MT-RJ connector is illus-trated below.

OBJECTIVES ON THE JOBThe use of fiber-optic cable in networks is spreading from backbones into LAN closets and todesktop connections. Higher data throughput requirements and reduced cable costs have driventhis migration.You need to be aware of the different connectors you are likely to encounter onexisting fiber cable and on new fiber installations.Traditional SC and ST connectors are beingreplaced by newer, smaller, more versatile connectors, called small form factor (SFF) connectors.

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1. What is the size of an LC connector in relation to a ST connector?a. An LC connector is half the size of an ST connector.b. An LC connector is twice the size of an ST connector.c. An LC connector LC is one third the size of an ST connector.d. They are about the same size.

2. What is one advantage of MT-RJ and Fiber LC connectors over ST and SC connectors?a. They are smaller and thus provide more flexibility in a wiring closet.b. They are larger and therefore more robust and less susceptible to damage.c. They are made of better quality steel which has improved electromagnetic qualities.d. They are the original fiber optic connectors and are therefore more readily accepted by net-

work administrators.

3. LC can be used with which of the following cables? (Select all that apply)a. single-mode fiber cableb. multimode fiber cablec. unshielded twisted-pair cabled. shielded twisted-pair cablee. coaxial cable

4. LC and MT-RJ connectors are standardized to be interchangeable. True or False?

5. What functionality do the dual cable strands in MT-RJ provide?a. redundancyb. fault tolerancec. duplexingd. higher strength

6. What style of connector is LC and MT-RJ?a. screw-on typeb. snap-in typec. bayonet twist typed. friction fit type

7. Which organization has standardized MT-RJ connectors?a. ANSIb. OSIc. TIA/EIAd. IEEE

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1.5 Recognize the following media types and describe their uses:

CATEGORY 3, 5, 5E, AND 6 CABLE, UTP (UNSHIELDED TWISTED-PAIR), AND STP(SHIELDED TWISTED-PAIR)

UNDERSTANDING THE OBJECTIVECategory 3, 5, 5e and 6 twisted-pair, copper cabling are the most used media in today’snetworks.These cables generally come in two varieties—STP (shielded twisted pair) and UTP(unshielded twisted pair).They are typically referred to as CAT3, CAT5, and so on.

WHAT YOU REALLY NEED TO KNOW◆ Twisted-pair cabling comes in several numbered versions, or categories, depending

on its physical characteristics and its intended use. The two most popular installedcategories are CAT3 (Category 3) and CAT5 (Category 5). In all twisted-pair catego-ries, the wire pairs are color coded to ease cable assembly. The standard colors areorange/orange-stripe, green/green-stripe, blue/blue-stripe, and brown/brown-stripe.In each case, the solid and striped wires are twisted together, with all four twisted-pairs housed in an outer sheath.

◆ STP cable has a layer of metallic foil insulation embedded beneath the outersheath to protect the data signals from EMI (electromagnetic interference). UTPand STP can both transmit data at 10, 100, and 1000 Mbps, and both types are ter-minated with the RJ-45 connector.

◆ CAT3 cable has four twisted cable pairs. It has a maximum rated throughput of 16Mbps. It can be used for both voice and data transmission. Ethernet technology10BASE-T has been standardized for transmission over CAT3 cable and can also beused with CAT5 cable. Not all technologies make use of all four twisted pairs. Forinstance, 10BASE-T technology uses only two pairs.

◆ CAT5 cable has four twisted cable pairs. It supports a throughput of up to 100Mbps and a 100 MHz signal rate, Both Fast Ethernet (100BASE-TX) using two wirepairs, and Gigabit Ethernet (1000BASE-T) using all four wire pairs have been stan-dardized with CAT5 cable.

◆ CAT3 and CAT5 cable may look alike but they are not tested to the samestandards—CAT5 testing being more rigorous and demanding. The main differencebetween the two categories is the number of twists in the cable over a specificdistance. CAT5 has a twist ratio that is about twelve times as tight as CAT3 makingit more resistant to crosstalk interference, thus offering better performance. Also,CAT5 cable is usually stamped with the type and category on the outer sheath.

◆ CAT5e (Category 5e or Enhanced CAT5) cable differs from CAT5 in that it has ahigher grade of copper, a higher twist ratio, and more advanced methods forreducing crosstalk. It supports a signal rate of up to 350 MHz.

◆ CAT6 (Category 6) cable has four wire pairs, each wrapped in metal foil. The fourpairs are bundled, and wrapped in another metal foil, which is then covered witha fire resistant plastic sheath. The added EMI shielding enables CAT6 cable to sup-port a signal rate of 250 MHz and a throughput of at least six times that of regu-lar CAT5 cable. One drawback to CAT6 is its decreased flexibility and increasedcable weight due to the added EMI protection.

OBJECTIVES ON THE JOBMost new copper cabling installed today is either CAT5 or CAT5e UTP. One major benefit forthe CAT5 installed base is that 1000BASE-T Ethernet has been standardized with this cable.Youmight encounter legacy CAT3 installations still running voice and 10BASE-T technologies.CAT5e and CAT6 may be encountered in areas where extra EMI resistance is called for, such ascable installed near main building power lines or near fluorescent light fixtures.

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1. What is the main different between Category 3 and Category 5 cable?a. Category 3 has 3 wire pairs and Category 5 has 5 wire pairs.b. Category 3 wire is thicker than Category 5 wire.c. Category 3 has a lower twist ratio than Category 5.d. Category 3 wires are one color and Category 5 wires are five colors.

2. How many wire pairs are there in Category 5 cable?a. twob. fourc. sixd. eight

3. What colors are used to code Category 6 wire pairs?a. orange / red / yellow / whiteb. blue / white / red / blackc. black / tan / white / greend. orange / green / blue / brown

4. What is the main difference between UTP and STP cable?a. STP cable has EMI Shielding whereas UTP cable does not.b. UTP cable always has a higher twist ratio than STP cable.c. The sheath material for STP cable is metallic whereas the sheath material for UTP cable is

plastic.d. UTP cable wire is always thicker than the wire for STP cable.

5. 1000BASE-T technology is able to effectively use CAT3 cable. True or False?

6. How does CAT5e cable differ from CAT5 cable? (Select all that apply)a. CAT5e has a higher twist ratiob. CAT5e has a better grade of copperc. CAT5e is less expensived. CAT5e has more EMI shielding

7. What does the “T” in 1000BASE-T stand for?a. terrestrialb. terminatedc. technicald. twisted-pair

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1.5 Recognize the following media types and describe their uses (continued):

COAXIAL CABLE


One of the lesser used yet still visible media in modern networks is coaxial cable. It may stillbe found in some backbone situations and in areas where well-shielded transmission with highthroughput is required and cable flexibility is not a concern. Legacy Ethernet networks maystill have some coaxial cable installed.

WHAT YOU REALLY NEED TO KNOW◆ Coaxial cable (usually called “coax”) consists of a solid or multi-stranded copper

wire core which serves as the electrical conductor. The core is surrounded by insu-lating PVC or Teflon, which in turn is covered by braided copper (that serves as anEMI shield and ground), and an outer waterproofing sheath. The cable is termi-nated at either end by an F-Type connector. A coaxial cable is illustrated below:

◆ Different specifications and materials apply to coaxial cable. Most have an RG(Radio Guide) designation, such as RG-6 or RG-58A/U.

◆ Initial installations of cable for Cable TV were copper coax. These are now beingreplaced by higher quality fiber-optic cable. Nonetheless, homes in the UnitedStates are still connected to their cable companies via copper coax. Most homeusers also connect to the Internet via coax cable if they use cable modems.

◆ When coaxial cable is used in a bus topology, either end of the network bus mustbe terminated with a resistor to attenuate signals that reach the end of the cable,thus preventing the signals from being reflected back into the cable and causingnetwork congestion.

◆ Coaxial cable is used on networks for short distances requiring high bandwidth,maximum EMI protection and data reliability. Typical uses include video distributionor connection between backbone devices.


You will most likely encounter coaxial cable on older Ethernet or Token Ring networks.Youmay also come across installations of shorter coax patch cables, perhaps between networkdevices like routers or switches in a LAN closet.The coax connector you will likely encounteris the F-Type screw-fit connector like the one that connects your cable outlet to your TV.

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O B J E C T I V E S



1. Which connector is used with coaxial cable?a. RJ-45b. RJ-11c. RG-45d. F-Type

2. Which physical topology is typically associated with coaxial cable LANs?a. busb. starc. meshd. hybrid

3. What is used to construct the core of a coaxial cable?a. steel wireb. fiber strandsc. PVC extrusiond. copper wire

4. Where would you likely find coaxial cable installed on a modern network?a. connecting a workstation to a switchb. connecting a video recorder to a multiplexerc. connecting two hubs togetherd. connecting two corporate buildings in different cities

5. Why has coaxial cable been replaced as a preferred media for modern LANs?a. It does not have the bandwidth capacity.b. It is too unmanageable to handle.c. It cannot adequately protect signals from high electromagnet interference.d. Its component materials are in short supply.

6. Cable TV companies use coaxial cable to connect your home cable modem to the Internet. Trueor False?

7. In a coaxial cable, what is the main purpose of the metal shield layer covering the innerinsulating layer?

a. It serves to strengthen the cable.b. It prevents Ultraviolet rays from deteriorating the PVC insulator.c. It acts as a moisture barrier.d. It serves as an EMI shield and electric ground.

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1.5 Recognize the following media types and describe their uses (continued):

SMF (SINGLE-MODE FIBER) OPTIC CABLE AND MMF (MULTIMODE FIBER)OPTIC CABLE

UNDERSTANDING THE OBJECTIVEFiber-optic cable is getting less expensive and thus more prevalent in the LAN environment. Itshigh bandwidth capabilities coupled with high resistance to outside interference makes it themedia of choice in many high traffic areas, such as the network backbone and distribution channelsto work areas needing extra throughput capacity.

WHAT YOU REALLY NEED TO KNOW◆ Fiber-optic cable consists of an inner core of single or multiple fine, continuous

strands of glass or plastic. The inner fiber strand (or strands) is covered with a glassor plastic cladding material of greater density than the inner fiber, thus serving asa reflector to keep light waves from escapingthe cable. A protective layer of Kevlar coversthe cladding and a further protective plasticcoating seals the cable. An illustration of afiber-optic cable is shown at night:

◆ Data is transmitted through the fiber-optic cable via light waves that are sent intothe cable using either a laser or a light emitting diode (LED).

◆ Fiber-optic cable falls into two categories: SMF (single-mode fiber) and MMF (multi-mode fiber). A mode is a beam of light. Therefore, single-mode fiber conveyssingle light beams, and multimode fiber conveys multiple light beams simulta-neously, each reflecting off the wall of the inner core at different angles.

◆ SMF uses a narrow inner core of about 10 microns in diameter. Laser light sentthrough the core travels a single path. Because there is little reflection, the lightdoes not disperse. This high degree of continuity allows single-mode fiber toaccommodate high bandwidths and long distances with very little optical loss.Single-mode fiber is used to connect carrier’s facilities, but it is too costly for nor-mal LAN connectivity.

◆ MMF contains a core whose diameter ranges from 50 to 115 microns. The mostpopular diameter is 62.5 microns. A laser or LED is used to send light waves intothe fiber. The light waves enter the fiber core at different angles, thus requiringdiffering times to traverse the cable. This results in some signal degradation, calledmodal dispersion, over distance, making multimode fiber unsuitable for long dis-tance data communication.

◆ Fiber cable has nearly unlimited throughput capacity. It is not susceptible to EMI orother forms of atmospheric interference, nor can it be easily intercepted andtapped.

◆ The principal drawback to fiber cable is its cost compared to UTP and its difficultmaintenance in the field.

◆ Fiber has proved reliable for data transmission rates in excess of 10 Gbps. Depend-ing on the fiber specification, segment lengths range from 150 meters to 40kilometers. Optical loss is one of the few factors that limits segment length andsignal quality.

OBJECTIVES ON THE JOBYour first encounter with fiber will likely be at your entrance facility,where your service providerpasses the network signal off to your LAN.You’ll also find fiber in main computer rooms wherenetwork connectivity devices such as routers and switches are chained together on your networkbackbone.These high traffic areas require the bandwidth that fiber can easily support.

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O B J E C T I V E S



1. What is the signal carrier that passes through a fiber-optic cable?a. lightb. electrical currentc. infrared radiationd. ultraviolet radiation

2. What differentiates multimode from single-mode fiber?a. the number of fibers in the cable bundleb. the color of light sent through the cablec. the number of light beams simultaneously sent through the fiberd. the material from which the fiber is constructed

3. What is the nominal diameter of a typical single-mode fiber strand?a. 1 millimeterb. 10 millimetersc. 1 micrond. 10 microns

4. What is the most popular diameter for multimode fiber strands?a. 10 micronsb. 50 micronsc. 62.5 micronsd. 115 microns

5. Which device is used to impart a signal to a single-mode fiber?a. light emitting diode (LED)b. strobe lightc. eectric sparkd. laser

6. Multimode fiber is better than single-mode fiber for long distance data transmission. True or False?

7. Which of the following affects signal transmission through a fiber cable the most?a. optical lossb. electrical impedancec. EMId. atmospheric disturbances

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1.6 Identify the purpose, features, and functions of the following networkcomponents:

HUBS


Hubs are simple connectivity devices that belong to the Physical layer of the OSI Model.Theirprimary purpose is to regenerate (or repeat) digital signals from one node to the rest of anetwork segment. Because they do not perform sophisticated functions, such as those that arouter performs, hubs are less intricate and less expensive than higher-layer connectivitydevices.

WHAT YOU REALLY NEED TO KNOW◆ At its most primitive, a hub is a multiport repeater, or a device that regenerates

the digital signals it receives from one node to the rest of the nodes on a networksegment. A hub often connects multiple workstations to each other and to thenetwork’s backbone.

◆ Hubs belong to the Physical layer of the OSI Model.◆ On Ethernet networks, hubs typically serve as the central connection point for

branches of a star or star-based hybrid topology.◆ On Token Ring networks, hubs are called MAUs (Multistation Access Units) and are

used to connect nodes in a star-based ring topology.◆ Hubs come in many different varieties and are specific to the type of technology a

network uses—for example, 10BASE-T versus Token Ring.◆ On a hub, the uplink port is the receptacle used to connect one hub to another

hub in a daisy chain or hierarchical fashion.◆ On a hub, the backbone port is the receptacle used to connect a hub to the net-

work’s backbone, and it should only be used for this purpose.◆ Some hubs have internal processing capabilities that allow them to process data,

provide troubleshooting information, and monitor traffic. Such hubs are known asintelligent hubs or managed hubs.

◆ On Ethernet networks, hubs have collision lights (or LEDs), which can indicate thevolume of collisions that segment is experiencing by blinking.

◆ The link LED is the light on a port that indicates whether it is in use. If a connec-tion is live, this light should be solid or blinking green.


Hubs can be found on even the smallest networks, and they certainly perform many functionson larger networks.While working as a networking professional, you should be familiar withspecifying, installing, maintaining, and troubleshooting hubs.As with all network equipment,hub functionality varies from one model and manufacturer to another, so be certain to read thedocumentation that ships with the hub in order to properly perform these functions.

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O B J E C T I V E S



1. What is the main difference between a hub and switch?a. Hubs can extend a network, while switches cannot.b. Switches can be used in a star-bus topology, while hubs cannot.c. Hubs broadcast signals to all connected nodes, while switches direct signals only to an

intended recipient.d. Because of their multiport design, hubs are more fault-tolerant than switches.

2. What can you view to determine whether a hub port is receiving information from aworkstation’s NIC?

a. the uplink LEDb. the collision LEDc. the link LEDd. the backbone LED

3. Which of the following characteristics do hubs and switches share?a. Both can connect multiple workstations to the network’s backbone.b. Both can translate between IPX and IP traffic.c. Both forward and/or filter frames based on their MAC address.d. Both interpret Network layer addresses to determine where to deliver data.

4. Which of the following is probably the least expensive connectivity device?a. switchb. routerc. bridged. hub

5. What is used to connect one hub to another hub in a daisy-chain fashion?a. their uplink portsb. their backbone portsc. their punch-down portsd. their collision ports

6. In which two of the following types of networks would viewing a hub’s collision LED be useful fortroubleshooting?

a. 10BASE-Tb. FDDIc. Token Ringd. 100BASE-FX

7. What is the maximum number of hubs that can be connected in serial on a 10BASE-T network?a. twob. threec. fourd. five

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1.6 Identify the purpose, features, and functions of the following networkcomponents (continued):

SWITCHES AND BRIDGES

UNDERSTANDING THE OBJECTIVESwitches are connectivity devices that subdivide a network into smaller logical segments bycreating individual channels for each device connected to it.Bridges are devices that connect twoLANs or LAN segments using one port per segment.

WHAT YOU REALLY NEED TO KNOW◆ Switches are devices that subdivide networks into smaller pieces (or collision

domains) can be described as multi-port bridges. They interpret MAC addressing tosend data to their intended destinations. Traditional switches operate in the DataLink layer of the OSI Model and are often referred to as a Layer 2 device. However,switch technology is evolving and some switches are now capable of operating atLayers 3 and 4.

◆ A switch creates a separate logical communication channel for each device con-nected to it. For an Ethernet network, each of these channels represents a collisiondomain, thus limiting the potential for packet collisions on the network. Becausethey are more efficient, more intelligent devices, switches and replacing hubs asnetwork connectivity devices.

◆ One disadvantage of switches is that they buffer data to accommodate bursts oftraffic and thus they can become overwhelmed in heavy network traffic causingdata to be lost and network traffic to slow down significantly. However, throughhardware and software improvements, switch performance is still better than thatof hubs and is steadily improving.

◆ Bridges are devices that move frames between two LANs or LAN segments. Theyoperate in the Data Link layer, which encompasses physical addressing.

◆ Bridges are similar to repeaters in that they do not modify the contents of apacket. But they are more sophisticated than repeaters, because they interpretaddressing information and filter packets.

◆ Because they can selectively filter packets, bridges can be useful for separating LANsegments, thus reducing the possibility that errors on one segment will affecttransmission on the other segment.

◆ Bridges read the destination MAC address of each frame and decide whether toforward (retransmit) the packet to another segment on the network or, if itbelongs to the same segment as the source address, filter (discard) it.

◆ As nodes on a network transmit data through the bridge, the bridge establishes afiltering database (also called a forwarding table) of known MAC addresses andtheir location on the network. It uses the filtering database to determine whethera packet should be forwarded or filtered.

OBJECTIVES ON THE JOBSince bridges and switches only interpret addressing information at the Data Link layer of the OSIModel, they can connect networks that use different Network layer protocols (for example, IPXand IP).Both can be useful for extending and interconnecting multiple LAN segments.Bridges arebecoming obsolete in modern networks because their functionality is being built into othernetwork devices, such as switches.As a network administrator, you are likely to replace networkhubs with more efficient switches.

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O B J E C T I V E S



1. Which of the following do bridges and hubs have in common?a. Both operate at the Physical layer of the OSI Model.b. Both can interpret MAC addresses and forward or filter frames based on this information.c. Both repeat signals in order to allow data to reach their destination.d. Both can interpret Network layer addresses to efficiently forward data to their destination.

2. Which of the following is associated with a MAC address in a bridge’s filtering database?a. bridge port numberb. IP addressc. protocold. subnet mask

3. Why is a switch generally faster than a router?a. because it does not interpret Data Link layer informationb. because it does not acknowledge data transmission errorsc. because it accepts only connectionless protocolsd. because it does not pay attention to Network layer information

4. What IEEE standard describes bridging?a. 802.1b. 802.2c. 802.3d. 802.5

5. What is one advantage of using a switch over a bridge?a. Since switches have multiple ports, fewer are necessary to make the same number of connec-

tions between multiple segments.b. Switches are less expensive to install and maintain.c. Switches are inherently more secure than bridges.d. Since switches can interpret Network layer addresses, they can more efficiently forward data

to their destination.

6. Under what conditions will a bridge filter a packet?a. when it detects an incorrect checksumb. when it detects a damaged headerc. when the packet’s destination MAC address belongs to the port on which the bridge

received itd. when the packet’s source MAC address belongs to the port on which the bridge received it.

7. Switches provide the foundation for which of the following types of networks?a. VPNsb. VLANsc. MANsd. WANs

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ROUTERS


Routers use Network layer addressing information to intelligently route data between LANs.They are used to connect dissimilar LANs in the case of WANs or LAN segments in the caseof LANs.

WHAT YOU REALLY NEED TO KNOW◆ Routers are devices that connect multiple LANs or LAN segments and direct data

between nodes using the best possible route. A router has multiple ports and canconnect dissimilar LANs and WANs running at different transmission speeds andusing a variety of protocols.

◆ Routers belong to the Network layer of the OSI Model. In order for a protocol tobe routable, it must contain Network layer information. IPX/SPX, TCP/IP, and Apple-Talk are routable protocols, while SNA and NetBEUI are nonroutable.

◆ The best path between nodes on a network depends on the number of hopsbetween nodes, the current network activity, unavailable links, varying networktransmission speeds, and topology.

◆ When used in networking, the term route means to intelligently direct data basedon addressing, patterns of usage, quality of service, and network availability.

◆ Unlike bridges, routers are protocol-dependent. They must be designed or config-ured to recognize protocols on the network.

◆ A typical router has an internal processor, its own memory and power supply, inputand output jacks for different types of network connectors (depending on the net-work type), and usually, a management console interface.

◆ To determine the best path between two nodes, routers communicate with eachother through routing protocols. Examples of routing protocols are RIP, OSPF,EIGRP and BGP.

◆ In static routing, a router contains routing tables (instructions on how to forwardpackets) that are manually programmed by a network administrator. Since the loca-tion of devices on a network and the best paths between them can change often,static routing is not a flexible or efficient technique.

◆ In dynamic routing, a router calculates the best path between nodes and automati-cally updates its routing tables if it detects network congestion or failures. Dynamicrouting is faster and more reliable than static routing.


Routers are common devices used to connect two different LANs.They are sophisticated andflexible. However, the more sophisticated the device, the more complex it is to install,configure, and maintain. Careful thought must be put into designing a network with routers.

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1. What resource does a router use to help it determine the best path between two nodes?a. filtering databaseb. routing tablec. SNMP databased. DNS records

2. What is one advantage of dynamic routing over static routing?a. It is more reliable.b. It is more secure.c. It prevents network administrators from having to configure the router.d. It can interpret both IP and IPX addresses.

3. Which of the following addresses could a router interpret?a. 506.78.34.110b. AE:09:35:00:BF:34c. AA:01:01:46:34:29:80d. 128.92.35.117

4. Which two of the following factors do routers consider when selecting the best path for data totravel between two nodes?

a. network transmission typeb. network congestionc. network protocold. data priority

5. What is the function of a routing protocol?a. to enable communications between routersb. to facilitate translation between the Network and Transport layers of the OSI Modelc. to convert nonroutable protocols into routable protocolsd. to ensure that encapsulated protocols are routed properly

6. Which of the following cannot forward NetBEUI packets?a. repeaterb. bridgec. brouterd. router

7. What is one of a router’s primary functions?a. to determine the best path for forwarding data to its destinationb. to regenerate attenuated signalsc. to separate groups of network devices into broadcast domainsd. to filter traffic according to subnet

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GATEWAYS


Gateways connect two dissimilar networks or subnetworks. Gateways are combinations ofsoftware and hardware, and as such, they operate at multiple layers of the OSI Model.

WHAT YOU REALLY NEED TO KNOW◆ Gateways do not fall neatly into any specific hardware category. In general, a

gateway is a computer running special software or a connectivity device that actsas a translator between two dissimilar systems. It may connect networks runningdifferent protocols, architecture, or formatting.

◆ Gateways operate at multiple layers of the OSI Model, including Application, Ses-sion, Transport, and Network. They repackage incoming information so the destina-tion network can read it. They may also perform security and filtering functions.

◆ Gateways can exist on servers, PCs, or mainframes. In the case of connecting twolarge networks, a gateway is often a specialized router or router interface.

◆ Gateways are much slower than bridges or normal routers because of the complextranslations they conduct. Because they are slow, gateways have the potential tocause extreme network congestion.

◆ The most common type of gateway is the e-mail gateway, which translates mes-sages from one type of system to another.

◆ An Internet gateway allows and manages access between LANs and the Internet. Itcan restrict the kind of access LAN users have to the Internet and vice versa.

◆ A LAN gateway allows segments of a LAN running different protocols or networkaccess methods to communicate with each other.


Chances are, if you work on a LAN that connects to the Internet (two dissimilar networks),you will need to understand gateways. Since gateways can be very different, you must becertain to understand the functions and requirements of your particular gateway beforeinstalling, configuring, or maintaining it.

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1. Why are gateways slower than bridges?a. because they must read the source and destination MAC addressesb. because they must manage sessions, translate encoded data, and interpret logical and physi-

cal addressesc. because they must assign new IP addresses to every packetd. because they must interpret application programming interface output

2. What type of gateway would connect Token Ring and Ethernet networks within one building?a. e-mail gatewayb. IBM host gatewayc. LAN gatewayd. Internet gateway

3. Which two of the following could be considered gateways?a. routerb. switchc. bridged. firewall

4. Which two of the following could host an e-mail gateway?a. serverb. PCc. bridged. hub

5. When acting as an e-mail gateway, in which OSI Model layers does a gateway perform most of itsfunctions?

a. Data Link and Physicalb. Transport and Networkc. Transport and Sessiond. Application and Presentation

6. On a client/server network, what device initiates the process of assigning an IP addressthrough DHCP?

a. the DHCP serverb. the Gatewayc. the client’s primary authentication serverd. the client

7. Which of the following statements is true? (Choose all that apply)a. A gateway is an NOS software component that operates exclusively in the top two OSI

layers.b. A gateway can function on a PC server and a router, but not on a mainframe computer.c. A gateway is a combination of hardware and software.d. A firewall is a form of gateway.

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CSU/DSU (CHANNEL SERVICE UNIT/DATA SERVICE UNIT)


A combination of a CSU (channel service unit) and a DSU (data service unit) serves as aconnection point for a T1 line at a customer’s site. Most modern CSU/DSUs also contain amultiplexer.A CSU/DSU may be a separate device or an expansion card in another device,such as a router.

WHAT YOU REALLY NEED TO KNOW◆ Although CSUs and DSUs are actually two separate devices, they are typically com-

bined into a single box called a CSU/DSU. On some implementations, the CSU/DSUis integrated with a router or switch as an expansion card. This integration offersfaster signal processing and better network performance. In most cases it is also aless expensive and lower-maintenance solution than a separate CSU/DSU device.

◆ The CSU provides termination for the digital signal from the carrier and ensuresconnection integrity through error correction and line monitoring. It converts theT-carrier frames into frames the LAN can interpret.

◆ The DSU converts the digital signal used by bridges, routers, and multiplexers intothe digital signal sent via the T-carrier media. The DSU usually incorporates amultiplexer. In some T-carrier installations, the multiplexer can be a separate deviceconnected to the DSU.

◆ An outgoing signal from a LAN will first pass through the multiplexer, thenthrough the CSU/DSU where it is converted form transmitting over a WAN. Incom-ing signals from the WAN follow the reverse path, first passing through the CSU/DSU, before being demultiplexed and transmitted to terminal equipment, such asrouters, switches, or telephone exchange devices.


If your company leases one or more T lines, you will have a CSU/DSU unit in your maincomputer facility at the termination point of theT line.Your service provider will mostly likelyhave included a CSU/DSU as part of your contract. Servicing and maintenance of theCSU/DSU may also be part of your service contract.

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1. What does “CSU” stand for?a. communications service unitb. channel service unitc. communications session unitd. cable session unit

2. A CSU/DSU connects an incoming T-carrier line with which of the following devices?a. routerb. modemc. multiplexerd. laser

3. Suppose a company used a T1 line to carry its analog voice calls and data signals to and from thelocal phone company’s central office. What device or part of a device, in the company’s data centerwould terminate the T1 connection?

a. CSUb. DSUc. terminal equipmentd. multiplexer

4. In what order would an incoming signal pass through devices to reach a LAN workstation?a. CSU, DSU, terminal equipment, multiplexerb. multiplexer, terminal equipment, CSU, DSUc. DSU, CSU, terminal equipment, multiplexerd. CSU, DSU, multiplexer, terminal equipment

5. What is the function of a CSU?a. to encrypt and scramble signalsb. to provide termination for digital signals and ensure connection integrityc. to convert digital signals from one device to analog signals that can be used by another deviced. to convert digital signals from one device to digital signals that can be used by another device

6. What is the function of a DSU?a. to encrypt and scramble signalsb. to provide termination for digital signals and ensure connection integrityc. to convert digital signals from one device to analog signals that can be used by another deviced. to convert digital signals from one device to digital signals that can be used by another device

7. Which WAN technology is serviced by a CSU/DSU? (Choose all that apply)a. ISDNb. SONETc. T1d. T3

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NICs (NETWORK INTERFACE CARDS)


An NIC (network interface card) is a component of a network that connects an individualdevice to media and performs data transmission and reception. It is a Physical layer datatransceiver that allows a computer or other network device to communicate with othernetwork computers or devices.

WHAT YOU REALLY NEED TO KNOW◆ A transceiver is a device that receives and transmits signals. In most modern net-

works, a transceiver can only be found in the network interface card (NIC), ISDNadapter, or wireless access point, depending on the type of network.

◆ NICs (also called network adapters) are connectivity devices that enable networknodes to receive and transmit data over the network media.

◆ NICs are manufactured by many different companies, but each NIC has a uniquenumber encoded into its on-board memory which represents a MAC address. Thistwelve digit hexadecimal address has two parts. The first group six digits refers tothe manufacturer (called the Block ID) and the second group of six digits repre-sents the NIC serial number (called the Device ID). Following is an example of aMAC address: 00:60:8C:00:54:99

◆ All NICs have their own circuitry, a system board interface, and at least one recep-tacle for a connection to the network. They may be external or internal to adevice. Many newer PCs and notebook computers have the NIC circuitry integratedinto the system board (called an on-board NIC) so that the NIC does not appear asa separate, detachable device.

◆ NICs belong to the Physical layer because they transmit data signals but do not (ingeneral) analyze the data from higher layers.

◆ NICs come in a variety of types depending on network transport system (Ethernetvs. Token Ring), network transmission speed (100 Mbps vs. 1000 Mbps), connectorinterfaces (MT-RJ vs. RJ-45), type of bus connection (PCI vs. PCMCIA) or device(workstation vs. printer) they suit, and of course, manufacturer. A PCMCIA card is aplug-in NIC that is used on a laptop computer and is sometimes referred to as a“credit-card” NIC because of its size and shape.

◆ A wireless NIC uses an antenna to exchange signals with an access point or otherwireless NIC adapters.


It’s a good idea to use the same NIC vendor throughout a network.This makes support andmaintenance easier. To maximize network efficiency, it is also important to use NICs thatmatch the speed of your network. For example, using a 10 Mbps NIC on a network where allother devices are rated at 100 Mbps will decrease the efficiency of the node with the 10 MbpsNIC.You may sometimes need to use media converters—for example, to connect a NIC thathas an RJ-45 jack to a fiber optic cable.

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1. Which of the following do all NICs have in common?a. antennab. RJ-11 receptaclec. RJ-45 receptacled. a means for connecting to the system board

2. What type of NIC is intended for use with a laptop computer and is often referred to as a credit-card adapter?

a. PCMCIAb. PCIc. infraredd. USB

3. Which two of the following features that can be found on a sophisticated NIC (such as one foundin a server) improves the performance of the NIC?

a. diagnostic LEDsb. Direct Memory Access (DMA)c. SNMP capabilitiesd. on-board CPU

4. Why is a NIC referred to as a transceiver?a. It relays data signals to all hardware components in a computerb. It transmits and receives network signals for the device to which it is connected.c. It interprets network addresses in order to transmit signals accurately over a network.d. It converts a computer’s analog signals to digital signals for transmission over a network.

5. What is another common name for a Network Interface Card?a. a network gatewayb. a network repeaterc. a network adapterd. a network node

6. Which of the following types of NICs are you most likely to find on a modern desktop computer?a. PCIb. PCMCIAc. infraredd. parallel port

7. If a computer with a 10/100 Mbps NIC is connected to a switch that is rated at 1 Gbps, what is themaximum throughput that can be achieved between the computer and the switch?

a. 10 Mbpsb. 100 Mbpsc. 1 Gbpsd. The computer will not be able to communicate with the switch.

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ISDN (INTEGRATED SERVICES DIGITAL NETWORK) ADAPTERS


An ISDN (integrated services digital network) adapter is a network component that connectsindividual devices to the network media and performs transmission and reception functions.It is used instead of a modem to connect a computer to digital ISDN communicationchannels.

WHAT YOU REALLY NEED TO KNOW◆ ISDN adapters can have several different configurations. The adapter may plug into

a computer expansion slot, or it may use a computer’s serial or parallel port.◆ Using the ISDN BRI (Basic Rate Interface) from the telephone company’s lines, the

ISDN channels connect to an NT1 (Network Termination 1) device at the customer’ssite. The NT1 device connects the twisted-pair wiring at the customer’s buildingwith the ISDN terminal equipment via RJ-11 or RJ-45 data jacks. The ISDN TE (ter-minal equipment) may include cards or standalone devices used to connect com-puters to the ISDN line (similar to a NIC used on Ethernet or Token Ring networks).

◆ A high grade of ISDN, called PRI (Primary Rate Interface), provides higherthroughput. PRI uses the same type of equipment as BRI, but requires an addi-tional network termination device called a NT2 (Network Termination 2) to handlethe multiple ISDN lines needed to gain the higher throughput.

◆ So that the ISDN line can connect to analog equipment, the signal must first passthrough a terminal adapter. An ISDN adapter converts digital signals into analogsignals for use with ISDN phones and other analog devices. Some ISDN adaptersare capable of automatically switching modes (digital or analog) depending onwhether the type of transmission is voice or data.

◆ ISDN adapters are also called ISDN terminal adapters or ISDN modems.


ISDN was once thought to be a good way to achieve higher throughput for small- tomedium-size businesses that could not afford more expensive WAN technologies. However,ISDN has been surpassed by cheaper, less complicated WAN solutions such as DSL andbroadband cable and, therefore, is not as popular in the workplace. ISDN may be found inlocations where equivalent technologies are not offered by communication carriers. It alsomay be found as legacy equipment in locations where a business may have adopted anotherWAN solution, such as T1, but kept ISDN as a supplementary backup to handle excess peakperiod traffic.

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1. Which of the following is one function of an ISDN adapter?a. to convert incoming digital signals into analog signalsb. to convert outgoing digital signals into analog signalsc. to convert outgoing baseband signals into broadband signalsd. to convert incoming baseband signals into broadband signals

2. What types of receptacles would be found on an ISDN adapter?a. F-Type and AUIb. RJ-11 and RJ-45c. SC and STd. RJ-45 and RJ-52

3. Which two of the following might be terminating equipment connected to an ISDN adapter?a. fax machineb. multiplexerc. media filterd. telephone

4. When upgrading from ISDN BRI to PRI, what additional piece of equipment does a customer needto install?

a. a cable modemb. a network interface cardc. an EMI shieldd. a network termination device

5. Why has ISDN largely been surpassed by DSL and broadband cable as a preferred WANtechnology?

a. DSL and broadband cable are more readily available than ISDN in most areas.b. DSL and broadband cable are easier to install and configure than ISDN.c. DSL and broadband cable are usually less expensive to implement than ISDN.d. All of the above.

6. What is another common name for an ISDN adapter?a. ISDN terminal adapterb. ISDN termination equipmentc. ISDN network termination 1d. ISDN network termination 2

7. ISDN is primarily a LAN communication technology used for communicating between networkswitches. True or False?

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WAPs (WIRELESS ACCESS POINTS)


A WAP (WirelessAccess Point), also called simply an AP (Access Point), is a device used onwireless LANs to transmit and receive wireless signals to and from multiple nodes and retransmitthem to the rest of a network segment.Access points can connect a group of nodes with a networkor two networks together.They may use directional or omni-directional antennas.

WHAT YOU REALLY NEED TO KNOW◆ WAPs are devices that act as connection points on a wireless network. They con-

nect the network’s devices using wireless signals and act as control points on thenetwork to prioritize, organize and redirect signals to their intended destinations.

◆ WAPs are sometimes used in conjunction with wire-bound networks to offer anadded degree of flexibility in locating network nodes. It is common for a WLAN(wireless LAN) to have several access points, particularly if the WLAN serves manyworkstations in close proximity to one another.

◆ Typically an IEEE 802.11 WAP may service 10 to 100 wireless satellite nodes atranges up to 300 feet, depending on the manufacturer’s specifications for thedevice. Exceeding the recommended maximum number of connected nodes couldlead to a greater incidence of errors and slower overall transmission.

◆ Each WAP is configured by the manufacturer to operate with a specific wirelessstandard or set of standards. For instance, a WAP may be configured to use onlyIEEE 802.11b, or the WAP may but configured to use IEEE 802.11g and also bebackward compatible with IEEE 802.11b.

◆ WAPs may also be configured to permit roaming, so that a moving wireless nodemight receive continuous signals from different devices as it moves out of range ofone WAP and into range of another.

◆ To cover its intended range, a WAP must have sufficient power and be strategicallyplaced so that stations can communicate with it. For instance, if an access pointmust serve a group of workstations in several offices on one building floor, itwould most likely be located in an open area near the center of the floor. Also,the WAP’s signal must not be impeded by physical obstructions, such as thick wallsor metallic barriers.

◆ In addition to connecting multiple nodes within a LAN, WAPs can be used to con-nect two different parts of a LAN or two separate LANs. Such connections typicallyuse a fixed link with directional antennas between two access points. Becausepoint-to-point links only transmit in one direction (unidirectional), they can applymore energy to signal propagation than mobile wireless links which must transmitin all directions (omni-directional).

OBJECTIVES ON THE JOBWireless networking technology is becoming more common in the workplace to increaseworkforce flexibility and efficiency by freeing network devices from the bindings of cable media.When acquiring and installing wireless access points, it is important to ensure that the devicesmatch the standards for the network and that each device is optimally positioned for bestperformance.

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1. What type of antenna will be used with a WAP that services several surrounding workstations froma central location on a building floor?

a. a whip antennab. a omni-directional antennac. a unidirectional antennad. a dish antenna

2. When configuring a WAP for communication with a WAP on another part of the network, whattype of antenna would be used?

a. a whip antennab. a omni-directional antennac. a unidirectional antennad. a dipole antenna

3. What would be considered a typical maximum distance for a WAP to transmit its signal?a. 3 feetb. 10 feetc. 300 feetd. 1000 feet

4. What is a typical number of workstations that might be serviced by a single WAP?a. Each WAP can service only one workstation.b. A WAP can only service up to two workstations simultaneously.c. A WAP may service up to 100 workstations depending on the manufacturer’s specifications.d. There is no restriction. A WAP can service an unlimited number of workstations.

5. If a manufacturer has specified a maximum number of WAP connections, what might be one effectof exceeding the maximum?

a. transmission errorsb. WAP overheatingc. electrostatic discharge from the WAPd. no effect

6. A WAP can be connected to a wired LAN. True or False?

7. Is it possible to have WAPs that are manufactured to different standards connected together on thesame WLAN?

a. It is not possible.b. It is possible, but they must use omni-directional antennas.c. It is possible, but the standards must be compatible.d. It is possible without any restriction.

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MODEMS


Like a NIC, a modem must have unique and appropriate IRQ, I/O address, and memory addressrange settings. Among other parameters, a modem’s maximum port speed can be configuredthrough the operating system.The throughput of modern modems is limited to 56 Kbps.

WHAT YOU REALLY NEED TO KNOW◆ The word modem is derived from its function as a MODulator/DEModulator. A

modem converts a computer’s digital pulses into analog signals for the PSTN(because not all of the PSTN is necessarily capable of digital transmission), thenconverts the analog signals back into digital pulses at the receiving computer’s end.

◆ On modern computers, modems are typically integrated into the circuitry of themachine’s system board. However, If the modem is housed on a separate card, itwill be connected to the machine’s system board through a PCI or EISA expansionslot. If an external modem is used, it may connect to the PC’s serial port, PCMCIAslot, or USB port.

◆ Often the default values assigned when the modem is installed are correct. How-ever, the ISP a user dials might prefer different port settings (including parity, databits, and stop bits). You can configure these values through the operating systemof any personal computer.

◆ To use FIFO buffers, a modem must have a 16550 UART compatible chip. Thehigher the buffer settings, the faster data will be transmitted; however, less datacorrection will be employed.

◆ The IRQ, I/O base address, and memory range for a modem on a modern PC is ini-tially assigned in the BIOS, but it can be modified through the operating system.IRQ 4 is commonly assigned to the COM1 or COM3 serial ports, which are used formodem connections.

◆ A modem’s speed is measured in bits per second. The fastest modem transmissionpossible with current technology is 56 Kbps.

◆ A dial-up connection uses a PSTN or other line to access a remote server viamodems at both the source (for example, the salesperson’s computer) and destina-tion (for example, the office’s LAN server).


For networking professionals, knowledge of modems is often required when establishing ortroubleshooting remote connectivity. In such a situation, it is necessary to understand how themodem interacts with the operating system and how to fine-tune a modem connection.Fortunately, however, all types of modems are similar and not nearly as complex as otherconnectivity devices, such as routers.

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1. What IRQ number is commonly assigned to a computer’s internal modem?a. 1b. 3c. 4d. 9

2. What is the most likely means for a modem to connect to a desktop computer’s system board?a. serial portb. PCMCIA slotc. parallel portd. expansion slot

3. If a user configures her modem’s maximum port speed to 115,200 bps in her operating system, atwhat speed is she most likely to connect to her ISP?

a. 576,000 bpsb. 115,200 bpsc. 52,600 bpsd. 11,520 bps

4. In a remote networking situation, who or what dictates the proper connection preferences, includ-ing data bits and parity bit?

a. the remote access serverb. the client’s modemc. the LAN managerd. the client’s operating system

5. From what two words does the term “modem” originate?a. modulator/demodulatorb. modifier/demodifierc. moderate/demoderated. modiplexer/demodiplexer

6. What type of chip is needed for a modem to support FIFO buffering?a. 3000 UART or betterb. 10000 UART or betterc. 16550 UART or betterd. 56000 UART or better

7. Which of the following is one function of a modem?a. to convert incoming digital signals into analog signalsb. to convert outgoing digital signals into analog signalsc. to convert outgoing baseband signals into broadband signalsd. to convert incoming baseband signals into broadband signals

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TRANSCEIVERS (MEDIA CONVERTERS)


A transceiver is a device that transmits and receives signals. A NIC acts in part as a type oftransceiver.Specialized transceivers also act as media converters to convert signals coming fromone type of transmission media to another type of media, such as converting a wireless signalto one that could be transmitted over fiber-optic cable, or converting a UTP signal to afiber-optic signal.The functionality of transceivers and media converters is becoming moreand more important in networking as the diversity of transmission media grows.

WHAT YOU REALLY NEED TO KNOW◆ A media converter is a type of transceiver. A media converter completes the physi-

cal connection between two different types of media. It converts the signal so thatit can be transmitted on different media, such as converting an electrical signalfrom a UTP cable to a light signal for a fiber-optic cable. Media converters alsoconvert UTP electrical signals to RF signals for wireless transmission and vice versa.

◆ Because transmitting and receiving signals is also an important function of NICs,they can also be considered transceivers. Nearly all NICs contain a data transceiver,the device that transmits and receives data signals.

◆ Wireless NICs use an antenna (either internal or external) to exchange signals witha base station transceiver or another wireless NIC

◆ Organizations switching, or migrating, from UTP to fiber media can combine100BASE-TX and 100BASE-FX within one network. In order to do this, transceiversin computers and connectivity devices must have both RJ-45 and SC, ST, LC, orMT-RJ ports. Alternatively, a 100BASE-TX to 100BASE-FX media converter may beused at any point in the network to interconnect the different media and convertthe signals of one standard to signals that work with the other standard.

◆ In a wireless network environment, the intermediate points through which wirelesssignals are amplified or repeated are transceivers connected to antennas.


With the proliferation of network media types, network administrators have to know thechoices that are available to them for optimizing their network configurations.The ability touse devices that convert signals is critical.

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1. On a 100BASE-TX Ethernet network, where will you find the transceivers? (Choose all that apply)a. in the backbone wiringb. in the switchesc. in the networks adaptersd. in the horizontal wiring

2. In which of these scenarios would a media converter be required?a. to connect from a hub to a workstation using a UTP straight-through cableb. to connect from a switch using UTP cable workstation connections to a router using fiber-

optic cablec. to signal between two switches connected with fiber-optic cabled. to connect two wireless devices

3. What is one purpose of a media converter?a. It translates protocols at the Network layer.b. It converts digital signal frequencies in a NIC.c. It converts analog signals to digital signals.d. It converts fiber-optic light signals to electrical signals.

4. Which device functions as a transceiver?a. NICb. hubc. repeaterd. all of the above

5. Which connector conversion is most likely to require media conversion?a. RJ-45 to RJ-11b. RJ-11 to F-Typec. SC to MTRJd. RJ-45 to ST

6. Most NICs also function as transceivers. True or False?

7. In which OSI layer do transceivers and media adapters operate?a. Physical layerb. Data Link LLC sub-layerc. Network layerd. Transport layer

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FIREWALLSUNDERSTANDING THE OBJECTIVE

Network firewalls are intended to minimize or eliminate malicious attacks from outside sourcesand protect a network’s privacy and integrity. A firewall is essentially a gateway that selectivelyblocks or filters traffic between networks.Firewalls may be devices optimized for performing theirtasks or computers installed with software necessary to accomplish those tasks.

WHAT YOU REALLY NEED TO KNOW◆ A firewall consists of either software or specially configured hardware devices (such

as a router or a computer), or both.◆ A simple firewall is the packet-filtering firewall (also called screening firewall),

which is a device that examines the header of data packets passing through it todetermine if the packet is authorized to continue. Nearly all routers can be config-ured as firewalls.

◆ Examples of packet-filtering firewall software include IP Tables (for UNIX-type ofsystems), Checkpoint Firewall-1, McAfee Firewall, and Symantec Firewall.

◆ Firewalls can also be configured to block sensitive corporate information or wormsfrom leaving a LAN, or block outgoing traffic from a web server that is intendedto handle only incoming traffic.

◆ Some firewall settings which may need to be configured prior to use include, IPaddresses and ports, IP header flags, transmissions using UDP or ICMP protocols,and, a packet’s inbound or outbound status.

◆ Firewalls can be used to block ports, such as port 80 on a test Web server.◆ Packet-filtering firewalls are used in VPNs (virtual private networks) that make use

of the Internet. Such firewalls must be situated between the LAN and the Interneton either side of the VPN. The firewall will reject any packets that do not have IPaddresses from the sending VPN LAN.

◆ Firewalls can also be configured to allow exceptions to certain blocking rules. Inthese cases the network administrator would “punch a hole” in the security screenfor necessary exceptions.

◆ Packet-filtering firewalls operate at the Network layer. This prevents them fromdistinguishing between a harmless Web browser trying to access a Web server onport 80 and a malicious hacker trying to breach network security through the serv-er’s port 80. For higher level firewall protection, a proxy service software applica-tion, often combined in the firewall device, is required.

◆ A proxy service (also called an Application layer gateway) acts as an intermediarybetween the external and internal networks, screening all traffic.

◆ Proxy servers manage security at the Application layer. They can prevent outsideusers from discovering addresses of internal network devices. A proxy repackagesthe data frames from a workstation so that the workstation address is encapsu-lated in the frame and the frame appears to come from the proxy. The proxy thenpasses the frame to the packet-filtering firewall.

◆ Proxy servers can also improve network performance by caching frequentlyaccessed files such as Web pages so that they do not have to be repeatedlyretrieved from an outside source.

OBJECTIVES ON THE JOBOne of the most important tasks of a network administrator is to maintain the security andintegrity of the network. A firewall is one of the several means of defending a network. Itsconfiguration and deployment must be well understood by any network administrator.

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1. Where would a proxy server be located on a LAN?a. between a file server and the LAN firewallb. between the LAN firewall and the Internet connectionc. between a LAN switch and a workstationd. Proxy servers are not part of a LAN configuration.

2. What is the purpose of installing a firewall on a network?a. It serves to prevent malicious attacks originating from internal LAN workstations.b. It helps manage the traffic volume carried by application servers.c. It filters network traffic going between two ISPs.d. It filters network traffic coming into and going out of a LAN.

3. At which layer of the OSI model does a packet-filtering firewall operate?a. Data Link layerb. Network layerc. Session layerd. Application layer

4. At which layer of the OSI model does a proxy server operate?a. Data Link layerb. Network layerc. Session layerd. Application layer

5. Which of the following statements is the most correct?a. A firewall is primarily a security device.b. A firewall can prevent network cables from catching fire.c. A firewall is either a hardware device or a software application, but never both.d. A firewall is relatively easy to configure.

6. Which type of addresses do packet-filtering firewalls read?a. network addressesb. port addressesc. MAC addressesd. hardware addresses

7. Which scenario best describes the use of a firewall with a VPN?a. A VPN would have no requirement to use a firewall.b. A VPN would require a single firewall only on the transmitting end of the connection.c. A VPN would require a single firewall only on the receiving end of the connection.d. A VPN would require a firewall on both transmitting and receiving ends of the connection.

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1.7 Specify the general characteristics (for example: carrier speed, frequency,transmission type and topology) of the following wireless technologies:802.11 (FREQUENCY HOPPING SPREAD SPECTRUM) AND 802.11x (DIRECT

SEQUENCE SPREAD SPECTRUM)UNDERSTANDING THE OBJECTIVE

The most popular wireless standards used on contemporary LANs are those specified by IEEE802.11 which defines data communication over a WLAN (wireless LAN), and communicationbetween wireless clients and public service providers, via BWAs (broadband wireless access).Theydescribe communication methods using both RF (radio frequency) waves and infrared.

WHAT YOU REALLY NEED TO KNOW◆ A wireless node uses a special NIC with an RF transmitter (typically internal anten-

nas) to issue signals to a base station or access point, which allows it to connect toand communicate with wire-bound devices on a LAN while roaming.

◆ When the number of mobile clients or the geographical range increases, the num-ber of access points must increase.

◆ Nodes transmit signals to a base station in a broadcast fashion. On a network dia-gram, this is represented by an antenna radiating concentric waves to surroundingpoints, somewhat resembling a physical star topology. In some cases, wireless nodesmay communicate directly with each other in an ad-hoc fashion, thus avoiding hav-ing to transmit first to a base station.

◆ The original 802.11 standard specification, sometimes referred to as 802.11 Legacy,specifies data rates of up to 2 Mbps, operates in the 2.4GHz band, and uses FHSS(frequency hopping spread spectrum) transmission encoding technology. FHSSemploys automatic random switching of the transmitted signal to help prevent sig-nals from being decoded.

◆ Another commonly used technology is DSSS (Direct Sequence Spread Spectrum).DSSS data signals are injected with a random sequence of 1 or -1 values that act asnoise and make the entire signal seem to be static. The noise is then removed atthe receiver to recover the data signal.

◆ The three common 802.11 standards (b, a, and g) share some common Physicallayer services: they all use half-duplex signaling, and the CSMA/CA media accessmethod (as opposed to wire-bound Ethernet which uses CSMA/CD).

◆ 802.11b, which currently is the most popular specification, uses DSSS signal modula-tion, supports data rates up to 11 Mbps, and operates in the 2.4 GHz band. Realis-tic rates of around 5 Mbps are more commonly achieved for wireless nodes within100 meters of an access point

◆ 802.11a uses OFDM (orthogonal frequency division multiplexing) signal encodingscheme. It supports data rates up to 54 Mbps, and operates in the 5 GHz band.Realistic throughput is between 11 and 18 Mbps. Its use of higher transmissionfrequencies and wider bandwidth results in higher throughput, but requires morepower and the signals travel shorter distances. The average range for an 802.11aantenna is 20 meters.

◆ 802.11g uses the OFDM, has three available channels supporting data rates up to54 Mbps, and operates in the 2.4 GHz band. It is backwards compatible to 802.11b.Realistic throughput is between 20 to 25 Mbps. The 802.11g antenna has a rangeof 100 meters.

OBJECTIVES ON THE JOBWireless networking is becoming commonplace with standards and specifications evolvingquickly, particularly as they affect security and operating range.You must be aware of scalability,client mobility needs, and compatibility with existing wire-bound infrastructures.

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1. Which versions of the IEEE standard covering wireless LAN transmissions are currently being used?a. IEEE 802.11ab. IEEE 802.11bc. IEEE 802.11gd. All of the above

2. Which version of the IEEE standard covering wireless LAN transmissions was the first to gain largescale commercial popularity?

a. IEEE 802.11ab. IEEE 802.11bc. IEEE 802.11gd. IEEE 802.11n

3. Which frequency band is used by IEEE 802.11b?a. 1.5 GHzb. 2.4 GHzc. 4.2 GHzd. 5 GHz

4. Which version of the IEEE 802.11 standard has the shortest maximum range?a. 802.11ab. 802.11bc. 802.11gd. Their maximum ranges are approximately equal

5. What device is required to connect wireless devices to a wire-bound network?a. hubb. wwitchc. access pointd. router

6. Which method of signal modulation is used by the original IEEE 802.11 standard specification?a. FHSSb. DSSSc. OFDMd. The original 802.11 does not modulate its signals.

7. IEEE 802.11g has a higher rated throughput than IEEE 802.11b. True or False?

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1.7 Specify the general characteristics (for example: carrier speed, frequency,transmission type and topology) of the following wireless technologies(continued):

INFRARED


IR (Infrared) signals fall in the 300 to 300,000 GHz RF frequency range, which is just abovethe visible light spectrum. Devices using IR for data communication are usually short rangedevices such as a TV remote control. IR is used for short range wireless network connectionswhere data has to be transmitted between computers,PDAs,printers, cellular phones and othersuch devices.

WHAT YOU REALLY NEED TO KNOW◆ Specifications for using IR devices to signal between networking equipment have

been established by a non-profit organization called the IrDA (Infrared Data Asso-ciation), founded in 1994. IrDA also refers to the most popular IR networkingspecifications.

◆ IR signals are short range and generally require line-of-sight between the transmit-ter and the receiver, although in certain situations the IR signal can be reflectedoff an object to reach a receiver. The IrDA maximum prescribed link distancebetween devices is 1 meter (3.3 feet). IR signals can travel much farther distancesif, for instance, the signal projection device being used is an IR laser, but even so,the IR signals are still highly susceptible to atmospheric interference such as dust,smoke, fog, sun spots, and rain.

◆ IR signals use CSMA/CA media access technology at the Physical layer.◆ An IR enabled device such as a wireless keyboard must remain in close proximity to

its parent computer and have its IR port in view of the computer’s integrated orattached IR port.

◆ IR technology is relatively inexpensive compared to competing technologies such as802.11 and Bluetooth and it also requires less power to operate.

◆ The most recent IR standard provides for a maximum throughput of 4 Mbps whichis significantly greater than the current Bluetooth data rate.

◆ The growth of IR in network transmission has been hampered by its short rangelimitation due to signal loss and easy obstruction from obstacles placed in its path.


In the workplace, infrared technology has been used for quite some time to connect laptopcomputers together and to desktop computers, and to connect peripheral devices (such askeyboards and printers) to computers.While advances in IR technology are being made, so tooare advances in competing technologies such as Bluetooth.

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O B J E C T I V E S



1. What is the spectral frequency range in which IR functions?a. 30 to 300 MHzb. 4 to 4.438 GHzc. 300 to 300,000 GHzd. d,the visible light spectrum

2. Which organization administers the popular specifications for IR network devices?a. IrDAb. ANSIc. IEEEd. ISO

3. What is the maximum specified link distance for IR devices?a. 1 footb. 1 meterc. 10 metersd. 30 meters

4. What is the maximum specified throughput for the most recent IR standard?a. 723 Kbpsb. 1 Mbpsc. 2.5 Mbpsd. 4 Mbps

5. Which would be the best scenario for employing the use of IR data transmissions?a. connecting a network printer to a switch that is 30 feet awayb. connecting two computers in different roomsc. connecting two routers from different LANsd. connecting a desktop computer to a printer located on the same desk

6. Implementing IR devices is more costly that implementing 802.11 configured devices. Trueor False?

7. Which media access technology is used by infrared signals?a. CSMA/CAb. CSMA/CDc. token passingd. direct access

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1.7 Specify the general characteristics (for example: carrier speed, frequency,transmission type and topology) of the following wireless technologies(continued):

BLUETOOTH

UNDERSTANDING THE OBJECTIVEBluetooth is a wireless technology designed to connect computer peripheral devices, such askeyboards,mice,printers, and even telephones. Its name was derived from reference to the 10th

century Danish King, Harald Blatand. Bluetooth was conceived to be a simplified cablereplacement service, to allow users to get rid of the cables associated with a computer’speripheral devices.

WHAT YOU REALLY NEED TO KNOW◆ The Bluetooth standard was developed by a group of companies working under

the Bluetooth SIG (Special Interest Group). The term “Bluetooth” is the group’sproprietary trademark. The technology is used in a diverse spectrum of industrial,commercial, and household applications.

◆ The IEEE 802.15.1a standard for WPANs (Wireless Personal Area Networks) is basedon Bluetooth V1.2.

◆ Bluetooth is a Physical layer radio frequency (RF) standard that operates in the 2.45GHz band. It uses very low power signaling (to minimize interference betweendevices), making it a short range (10 meters) technology. To further reduce interfer-ence, Bluetooth uses FHSS modulation over 79 frequencies randomly switched 1600times per second.

◆ Bluetooth does not require line-of-site or synchronization currently required forsome devices such as PDAs (Personal Digital Assistant).

◆ Bluetooth devices contain very small, inexpensive RF transmitters that serve as loca-tors and transceivers to make the handshake between devices automatic with nouser intervention required.

◆ When Bluetooth devices come in proximity to one another, their transceivers deter-mine which device controls the conversation and which protocols will be used, andthen automatically form a PAN (personal area network) among the devices. Eachdevice has a pre-programmed address within the range for that particular type ofdevice. After devices determine that their addressing is compatible, they can startcommunicating on the PAN. If there are other PANs nearby, each PAN will hop fre-quencies randomly to minimize interference.

◆ Bluetooth devices may operate in half-duplex or full-duplex mode. Full-duplextransmissions can carry 64 Kbps; half-duplex can carry 721 Kbps; asymmetric (upthen back) transmission can carry 58 Kbps; and symmetric (both directions) trans-mission can carry 433 Kbps.

◆ Bluetooth EDR (Enhanced Data Rate) is rated at data speeds to 2.1 Mbps. Eventhough the EDR version has yet to be standardized by Bluetooth SIG, some manu-facturers have begun to replace current Bluetooth V1.1 and V1.2 devices with thefaster EDR microchips.

OBJECTIVES ON THE JOBIn the workplace, Bluetooth is competing with IR for short distance data signal transmissionbecause it offers certain advantages over IR. Its biggest advantage is that it is not restricted byrigid line-of-sight guidelines. It will most likely be found in a variety of cordless devices, suchas keyboards and mice.

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O B J E C T I V E S



1. Which operating environment is most likely to use Bluetooth technology?a. a busy LAN requiring connection between several switchesb. a WAN requiring connection to a service providerc. a computer requiring connection to a moused. a network router requiring connection to another router

2. Which IEEE standard incorporates Bluetooth technology?a. IEEE 802.3zb. IEEE 802.5c. IEEE 802.11gd. IEEE 802.15.1a

3. Who first developed Bluetooth?a. a group of private companiesb. the Danish governmentc. IEEEd. the International Organization for Standardization (ISO)

4. At which frequency does Bluetooth operate?a. 2.4 GHzb. 5.2 GHzc. 24 GHzd. 52 GHz

5. Bluetooth signals propagate over what media type?a. UTP cableb. fiber-optic cablec. infrared wavesd. radio frequency waves

6. Which operating range would be the most suitable for using Bluetooth configured devices?a. 50 feetb. 500 feetc. 5000 feetd. 5 kilometers

7. What is the approximate maximum throughput of a symmetric Bluetooth V1.2 connection?a. 0.4 Mbpsb. 2.0 Mbpsc. 2.4 Mbpsd. 4 Mbps

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1.8 Identify factors which affect the range and speed of wireless service (forexample: interference, antenna type and environmental factors):

FACTORS AFFECTING WIRELESS RANGE AND SPEEDUNDERSTANDING THE OBJECTIVE

Many factors influence the speed, quality and range of wireless network data transmissions.Characteristics that positively or negatively contribute to the effectiveness of wireless trans-missions include interference, antenna type, and certain environmental factors.

WHAT YOU REALLY NEED TO KNOW◆ Antennas are directional devices that channel transmitted energy in a pattern,

using the power of the transmitter to project the pattern.◆ The pattern projected by an antenna affects signal range. For instance, a unidirec-

tional antenna (signals in one direction) will have a greater range than an omni-directional antenna (signals in all directions), because of the focused power of theunidirectional antenna.

◆ Antennas come in a variety of shapes, sizes and functions, depending on the devicethey are used with, the required projection pattern, the required frequency, andthe power of the signal.

◆ Specific antennas are optimized to work best with wireless devices using the 2.4GHz band, such as 802.11b, 802.11g, and Bluetooth devices.

◆ Interference can take the form of noise often associated with EMI and can have adevastating effect on wireless data signals. EMI sources include motors, electricalcables and power lines, copiers, and fluorescent lights. Sun spots and solar flarescan also cause EMI.

◆ Another source of interference can be similar wireless devices operating at thesame or similar frequencies or equipment, such as a microwave oven which oper-ates in the 2.4 GHz band.

◆ Because infrared transmissions are close to the visible spectrum, they are adverselyaffected by some of the same environmental conditions that impede your vision,such as fog, smoke and dust particles, solid obstacles, rain, and even bright sun light.

◆ A well-located and -maintained antenna can significantly reduce RF scatter. Theremedy to poor signal reception is often relocating the wireless access point orreplacing the device’s antenna.

◆ Wireless ranges using an omni-directional antenna depend on the operatingenvironment. Outdoors with average interference, the average range might be 300feet. Indoors, the range is reduced, mostly by physical impediments. In a closedoffice the maximum coverage radius might be 60 feet, while in an open office, themaximum coverage might increase to 90 feet.

◆ Factors that affect wireless speed include: the protocol being used, such as 802.11,Bluetooth, and IR; the distance between communication points; the physical andatmospheric environment; the transmission frequency; the antenna efficiency andpower; the equipment manufacturer; the software application requesting thetransmission; and the security and interoperability implementations.


As a network administrator, you need to keep constant watch for physical and environmentalconditions that could impede the wireless data transmissions.Physical obstructions, equipmentrelocations, and a host of other factors, sometimes beyond your control, can hurt networkperformance.

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O B J E C T I V E S



1. Which device will work best with an access point whose antenna is tuned to the 2.4 GHz fre-quency band?

a. 802.11a wireless printerb. 802.11g PDA with omni-directional antennac. IR configured keyboardd. 802.11b laptop with a unidirectional antenna

2. Which of the following will not emit EMI that affects the operation of a wireless network?a. incandescent light bulbb. laser printerc. neon building signd. lightening bolt

3. Changes on the sun’s surface can affect the operation of your wireless network. True or False?

4. You are required to establish a network link between two of your corporate buildings. They are onestory each and located 300 feet apart with a nice wooded park in between. Which of the followingwould provide you with the most reliable service?

a. rooftop to rooftop link using Bluetooth technology.b. rooftop to rooftop link using IR technologyc. rooftop to rooftop link using an 802.11 technologyd. underground link using fiber-optic cable.

5. Which of the following might decrease the speed of transmission between devices on a wirelessnetwork?

a. moving the devices so that they at the same distance apart, but in a north-south orientationversus an east-west orientation

b. replacing 802.11b devices with 802.11g devices.c. rurning off the lights in the room where the devices are located.d. implementing software security features between the devices.

6. What type of antenna transmits a signal in all directions?a. omni-directionalb. bi-directionalc. bi-polard. high gain

7. How is the range of a wireless device affected as the transmission pattern of its antenna becomesmore directionally focused?

a. range is increasedb. range is decreased a little bitc. range is decreased drasticallyd. range is unaffected since antenna patterns don’t affect signal range

34384_CPEG_01 2/3/2005 15:41:32 Page 73


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