Network+ Certification Readiness Review by Craig Zacker

From the Publisher

Test your readiness for the Network+ exam.

If you took the Network+ Certification exam today, would you pass? With the Readiness Review exam simulation on CD-ROM, you get a low-risk, low-cost way to find out! This next-generation test engine delivers randomly generated practice exams that cover the actual Network+ objectives. You can test and retest with different question sets each time—and with automated scoring, you get immediate Pass/Fail feedback. More important, you get answers to these four critical questions:

• What do Network+ exam questions look like?
• In what topic and skill areas am I proficient/deficient?
• How should I focus my studies?
• Am I ready for the real exam?

• Media and topologies
• Protocols and standards
• Network implementation
• Network support

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• ISBN: 0735614571
• Publisher: Microsoft Press
• Pub. Date: January 2002
• Condition:

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• Table of Contents
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Table of Contents

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Objective Domain 1: Media and Topologies

LANs consist of more than just computers and cables, however. To attach a computer to the network, it must have a network interface card (NIC) in it, and to attach the cables to the NICs, they must have connectors on them. In addition, some network topologies require other hardware elements, such as hubs. More complicated network installations consist of multiple LANs connected using devices such as bridges, routers, switches, gateways, or even wide area network (WAN) links. You must understand the functions of all of these components and devices, and this objective domain tests your knowledge of them.

Tested Skills and Suggested Practices

The skills that you need to successfully master the Media and Topologies objective domain on the Network+ Certification exam include:

• Recognizing the following logical or physical network topologies given a schematic diagram or description: bus, ring, star/hierarchical, mesh, and wireless.
• Practice 1: Study the specifications associated with the various networking protocols that use these topologies, including Ethernet (IEEE 802.3), Token Ring (IEEE 802.5), and wireless LANs (IEEE 802.11b) and learn which topologies are used by each protocol and cable type.
• Practice 2: Create diagrams of simple LANs that use each of the specified topologies and compare them with any test or lab networks you have access to. Identify which topology your network uses.

• Specifying the main features, including speed, access method, topology, and media of: IEEE 802.3 (Ethernet), IEEE 802.5 (Token Ring), IEEE 802.11b (wireless), and FDDI networking technologies.
• Practice 1: Study the specifications for these protocols. The protocol standards specify the basic functions of the protocols, such as their speeds and access methods. List the various media and topologies you can use with each one.
• Practice 2: Determine which of the specified protocols your network uses. Examine the hardware used to construct it (after obtaining permission from the network administrator) and determine how it was installed.

• Specifying the characteristics, such as speed, length, topology, and cable type, of the following IEEE 802.3 (Ethernet) standards: 10BASE-T, 100BASE-TX, 10BASE2, 10BASE5, 100BASE-FX, and Gigabit Ethernet.
• Practice 1: Study the specifications for the various Ethernet physical layer options and compare their relative advantages in transmission speed, topology, and cable lengths.
• Practice 2: Create a diagram of your network's physical layer by studying the hardware used to construct it and determining how it was installed. Measure the lengths of the cable segments, mark them on your diagram, and determine whether your network was installed according to the specifications for the standard it uses.

• Recognizing the following media connectors and describing their uses: RJ-11, RJ- 45, AUI, BNC, ST, and SC.
• Practice 1: Create a list of the various connectors used to build LANs and specify the protocol and network medium that uses each one.
• Practice 2: Obtain cables that use each of the connectors on your list and take them apart, examining how they are constructed and how the conductors are connected.

• Choosing the appropriate media type and connectors to add a client to an existing network.
• Practice 1: Select a familiar business or organization. Make a list of its networking needs, including elements such as the number of computers it requires, the distances between them, the environmental conditions in which they would be installed, and the amount of data they have to transfer. Compare these requirements with the capabilities of the various media types and connectors used by the common data-link layer protocols. Select the one best suited to the job.
• Practice 2: Determine which media type and connectors your network uses and then redesign it using the other available media types and connectors. Estimate whether the redesigned network would be an improvement, based on criteria such as network performance, tolerance of cable breaks, and other physical layer faults.

• Describing the purpose, features, and functions of the following network components: hubs, switches, bridges, routers, gateways, CSU/DSUs, NICs/ISDN adapters/system area network cards, wireless access points, and modems.
• Practice 1: Study the functions of each of these devices and determine if they are currently used on your network. For each device your network is not using, determine how you would integrate it and what purpose it could possibly serve.
• Practice 2: Obtain product literature for several examples of each of these devices (from manufacturers, printed catalogs, or the World Wide Web) and familiarize yourself with their general appearance and common features.

Further Reading

Objective 1.1

Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 2, "Network Hardware."

Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for "bus topology," "mesh topology," "ring topology," "star bus topology," "star topology," and "topology."

Objective 1.2

Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1, 2, 3, and 5 in Chapter 5, "Data-Link Layer Protocols."

Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for "Ethernet," "Fiber Distributed Data Interface," "Token Ring," and "wireless networking."

Objective 1.3

Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 5, "Data-Link Layer Protocols."

Spurgeon, Charles. "Quick Reference Guides to 10 Mbps Ethernet" and "Quick Reference Guides to 100 Mbps Ethernet." These documents are available on Charles Spurgeon's Web site at http://wwwhost.ots.utexas.edu/ethernet/ethernet-home.html.

Objective 1.4

Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1 in Chapter 2, "Network Hardware."

Connectivity Knowledge Platform. "Connector Reference Chart." This document is available on CKB's Web site at http://www.mouse.demon.nl/ckp/misc/conchart.htm.

Objective 1.5

Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lesson 1 in Chapter 14, "Planning the Network."

Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for "cabling," "coaxial cabling," "fiber optic cabling," "twisted pair cabling," and "unshielded twisted pair (UTP) cabling."

Objective 1.6

Microsoft Corporation. Network+ Certification Training Kit. 2nd ed. Redmond, Washington: Microsoft Press, 2001. Review Lessons 1, 2, and 3 in Chapter 3, "Network Connections," Lesson 2 in Chapter 2, "Network Hardware," Lesson 5 in Chapter 5, "Data-Link Layer Protocols," and Lesson 2 in Chapter 12, "Remote Network Access."

University of Western Ontario. "Bridges vs. Switches vs. Routers." This comparison table is available on the UWO Web site at http://www.csd.uwo.ca/courses/CS457a/reports/handin/efteevan/A1/compare.html.

Microsoft Corporation. Microsoft Encyclopedia of Networking. Redmond, Washington: Microsoft Press, 2000. See entries for "access point," "bridge," "Channel Service Unit/Data Service Unit (CSU/DSU)," "gateway," "hub," "Integrated Services Digital Network (ISDN)," "modem," "network interface card (NIC)," "router," "switch," and "wireless networking."

Objective 1.1   Recognize the following logical or physical network topologies given a schematic diagram or description: star/hierarchical, bus, mesh, ring, wireless.

There are three main topologies associated with local area networking, and two others listed here that are seen less often.

• Bus topology—A bus topology is one in which each computer on the network is connected to the next one, forming an unbroken chain with two endpoints. When a computer transmits its data, the signals travel in both directions on the bus until they reach both ends. At each end of the bus you must have a terminator, which is an array of resistors that nullifies the signals reaching it. Without the terminators, the signals reaching the ends of the bus reflect back in the other direction, interfering with the new signals being introduced and causing data loss. Bus networks are also intolerant of cabling faults or network interface failures; a break in the bus splits the network into two halves that cannot communicate with each other. The bus topology is used by the two Ethernet coaxial cable specifications, which are called Thick Ethernet (10Base5) and Thin Ethernet (10Base2).
• Ring topology—A ring topology is one in which each computer on the network is connected to the next one, as in a bus topology, but the two ends are joined to form a ring. On a ring network, the signals travel in only one direction, and the computer that transmits data is also responsible for removing it from the network after it has traversed the entire ring. In most networks using ring topology, the ring is implemented logically, not physically. The cables connecting the computers do not run directly from node to node because a single cable break would bring the entire network down. Instead, they run to a special hub called a multistation access unit (MAU or MSAU). This unit implements the ring internally by transmitting incoming signals out through each port in succession and waiting for the signal to be returned over that port by the computer before transmitting it out to the next one. The result is a logical ring topology that is more fault tolerant than a physical one because the MAU can bypass specific ports, effectively removing malfunctioning nodes from the ring. The ring topology is used by several protocols, including Token Ring and Fiber Distributed Data Interface (FDDI).
• Star/hierarchical topology—A star topology is one in which each of the network nodes is connected to a central cabling nexus called a hub or concentrator. The hub takes the signals arriving through any of its ports, amplifies them, and immediately transmits them out through all of its other ports. This enables the computers connected to the hub to share a single network medium, just as if they were connected with a single cable. The hub also provides greater fault tolerance than a bus network. If a cable break or a NIC failure occurs, only one computer is affected. All of the others continue operating normally. To expand a star network beyond the capacity of a single hub, you can connect an additional hub by plugging it into the existing hub's uplink port. This expandability is not unlimited, however; the protocols that use this topology specify how many layers are permitted in the hierarchy. A network of this type is said to use a hierarchical star topology. 10Base- T Ethernet networks use the star topology, as do all Fast Ethernet networks.
• Mesh topology—In local area networking, a mesh topology is a theoretical construct in which each computer on the network has a dedicated connection to every other computer. This eliminates the shared medium from the LAN and enables the computers to communicate with each other at full speed, any time. The mesh topology is not feasible on today's LANs because it requires each computer to have multiple network interfaces—one for each of the other computers on the network. The term mesh is also used in internetworking to refer to a network with redundant routes between network intersections, enabling traffic to reach a destination using any one of several paths as a fault tolerance measure.
• Wireless topology—Wireless LANs eliminate the need for cables as a network medium, and in doing so, eliminate the need for a standard topology. A wireless LAN typically consists of a transceiver unit, called a wireless access point, that is connected to servers or directly to the network and other devices using a standard cabled network protocol, such as Ethernet or Token Ring. Client computers with their own transceivers can then communicate with the network-attached transceiver using any one of several wireless media, such as infrared light or radio waves.

MCS

N10-002.01.01.001

C

A company with a 25-node Thin Ethernet network is planning to upgrade to Fast Ethernet using UTP cable. Which of the following topology changes must they make during the upgrade process?

A. Bus to ring

Incorrect

A. The bus topology is indeed used by Thin Ethernet networks. The ring topology is used by Token Ring and FDDI networks among others, but it is not used by any type of Ethernet network.

B. Ring to star

Incorrect

B. Thin Ethernet networks use coaxial cable, which can only be installed using the bus topology. The star topology is used by Fast Ethernet networks running over UTP cable, however.

C. Bus to star

Correct

C. The company's existing network uses Thin Ethernet, which consists of coaxial cable installed in a star topology. The new network uses Fast Ethernet, for which one of the physical layer options is UTP cable, which you always install using a star topology.

D. Mesh to ring

Incorrect

D. The mesh topology is not used by any form of Ethernet or LAN protocol because each computer would have to have a separate network interface for each of the other computers on the network. The ring topology is not used by any form of Ethernet network.

MCS

N10-002.01.01.002

A

A maintenance worker accidentally cuts through a LAN cable while working inside an office's drop ceiling. On which type of topology is the cable break likely to cause the greatest disturbance in network communications?

A. Bus

Correct

A. When a cable break occurs on a bus network, the LAN is immediately split in two, preventing the computers on one side of the break from communicating with those on the other side. In addition, the break also creates two unterminated cable segments. This lack of termination will also affect the communications between computers on the same segment, effectively disrupting the entire network.

B. Ring

Incorrect

B. If a network uses a physical ring topology, a cable break would be catastrophic, preventing all communications from traversing the entire ring and from being removed from the ring by the transmitting system. This is why the ring topology is always implemented logically using the physical configuration of a star. When a cable break occurs, only the computer connected to the MAU by that cable is affected. The MAU detects the breakdown in communications with that computer and removes it from the logical ring.

C. Star

Incorrect

C. On a star network, each computer is connected to the hub using a separate cable. A cable break therefore affects only one of the computer/hub connections. The rest of the computers can continue to communicate normally.

D. Hierarchical star

Incorrect

D. A hierarchical star network is similar to a regular star network in that a break in a cable connecting a computer to a hub affects only that computer. However, a break in a cable connecting two hubs is more serious. In this case, the cable break splits the network in two, preventing the computers on one hub from communicating with the computers on the other. Unlike a bus network, however, no termination is needed, so the communications between the computers connected to each hub proceed normally.

MCM

N10-002.01.01.003

A and D

Which of the following statements about hubs and MAUs are true? (Choose two.)

A. Hubs amplify incoming signals before transmitting them.

Correct

A. A repeater is a device that amplifies signals so they can travel longer distances without suffering from signal degradation, also called attenuation. A hub's function is to transmit data received through any one of its ports out through all of its other ports. Hubs are also called multiport repeaters because they amplify the signals before retransmitting them.

B. Hubs provide termination for cable segments.

Incorrect

B. Networks using a star topology do not require termination, and hubs propagate signals to the network, not remove them.

C. MAUs are responsible for removing signals from the ring.

Incorrect

C. Signals are removed from the ring by the computer that originally transmitted them, not by the MAU.

D. MAUs maintain network integrity by removing malfunctioning nodes from the ring.

Correct

D. The primary reason for implementing the ring topology logically (inside the MAU) is to prevent a broken cable or malfunctioning computer from disrupting communications for the entire network. MAUs do this by performing an initialization process for each attached computer, which adds it to the ring. If a malfunction occurs, the MAU can remove the computer from the ring, bypassing it internally so that no data is transmitted to it or expected from it.

MCS

N10-002.01.01.004

D

Which of the following LAN topologies is implemented logically and not physically?

A. Star

Incorrect

A. The star topology gets its name from the use of a hub as the cabling nexus for all of the computers on the LAN. Even though the computers may not be dispersed evenly around a hub located in the exact center of the star, the physical layout of the network reflects the topology.

B. Bus

Incorrect

B. The bus topology consists of computers that are physically joined by cables running in a chain from one system to the next.

C. Mesh

Incorrect

C. The mesh topology doesn't exist on a LAN, either logically or physically; it is an internetwork topology that provides redundant physical paths between destinations.

D. Ring

Correct

D. The ring topology is implemented logically by a MAU that transmits incoming data packets out through each one of its ports in turn, waiting for the connected computer to return the packet before proceeding to the next port. Physically, the network is cabled using a star topology.

Objective 1.2   Specify the main features of 802.2 (LLC), 802.3 (Ethernet), 802.5 (token ring), 802.11b (wireless), and FDDI networking technologies, including speed, access method, topology, media.

Standard	MAC Method	Speeds	Media	Topologies
IEEE 802.3 (Ethernet)	CSMA/CD	10 Mbps 10/100 Mbps 10/100 Mbps	Coaxial U TP Fiber optic	Bus Star Star
IEEE 802.5 (Token Ring)	Token passing	4/16 Mbps	IBM Type 1/ UTP	Ring
FDDI	Token passing	100 Mbps	Fiber optic	Double ring
IEEE 802.11b	CSMA/CA	11 Mbps	DSSS	Ad hoc infrastructure

Ethernet is the most popular data-link layer LAN protocol in the world, with millions of nodes installed. Ethernet networks can run at different speeds and use different cables and topologies, but the main identifying characteristic common to all Ethernet networks is the media access control (MAC) mechanism known as Carrier Sense Multiple Access with Collision Detection (CSMA/CD). A MAC mechanism regulates access to a network, ensuring that each computer has an opportunity to transmit its data. Each computer on a CSMA/CD Ethernet network begins the transmission process by listening to the network, and if it's free, proceeds to transmit its data. Sometimes two computers transmit simultaneously, however, causing a collision. Collisions are a normal occurrence on Ethernet networks because the protocol design enables the computers to detect them when they occur and compensate for them by retransmitting the data. Over its 25-year history, Ethernet has evolved considerably. It now supports a variety of physical layer options, including two types of coaxial cable running at 10 Mbps in a bus topology; UTP cable running at 10, 100, or 1,000 Mbps in a star topology; and fiber optic cable, also running at 10, 100, or 1,000 Mbps in a star topology.

Token Ring is a data-link layer protocol, developed by IBM and later standardized by the IEEE, that is fundamentally different than Ethernet. Token Ring networks all use a logical ring topology, although their physical configuration is that of a star. Token Ring's MAC mechanism is called token passing, and it is the reason for using of the ring topology. A special packet called a token circulates around the ring until a computer has data to transmit. This computer takes possession of the token and proceeds to transmit its data. Only the computer possessing the token can transmit, making it impossible for collisions to occur on a network that is functioning properly. After the data circulates around the ring, the transmitting system is responsible for removing it from the network and generating a new token. Token Ring networks originally ran at 4 Mbps and used a shielded twisted pair (STP) cabling system called IBM Type 1. Today, virtually all Token Ring installations run at 16 Mbps and use standard UTP cables.

FDDI is a 100 Mbps data-link layer protocol that was designed for network backbones that require high speeds and must span long distances. FDDI pre-dates Fast Ethernet (which has since largely replaced it), and at the time of its conception was the only 100 Mbps LAN protocol available commercially. FDDI uses the token passing MAC mechanism and the ring topology, much like Token Ring, except that in some cases, FDDI networks are physically cabled in a ring formation. The physical ring doesn't provide the fault tolerance of the logical ring, so the standard also defines the use of an optional double ring topology. In the double ring, traffic travels in opposite directions on the two rings and the computers are connected to both rings. If one ring gets broken, the other can still carry traffic to any destination on the network....