Final Exam Guide | Telecommunications and Networking Essentials | CIT 2523, Exams of Computer Science

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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 broad areas) 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 the exam’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) that make up a network. It also includes an understanding of network connectivity devices such as hubs, routers, switches, gateways and wireless access points. Many of the topics in this domain comply with industry standards, such as IEEE’s working group standards for Physical and Data Link layer network access.Although the topics in this domain are highly technical, they are also relatively straightforward.

DOMAIN 2.0: PROTOCOLS AND STANDARDS — 20 PERCENT OF

EXAMINATION

This domain requires knowledge of protocols and standards, the means by which two computers communicate. Given that the most popular network protocol currently used on networks is TCP/IP, this domain pays particular attention to the protocols and subprotocols in the TCP/IP suite of protocols. In addition to protocols, this domain covers the OSI Model, a popular theoretical construct used to describe computer-to-computer communication. Much of 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 and NOSs (network operating systems). It covers the features of each, plus methods for connecting multiple types of clients with each NOS. In addition, this domain requires knowledge of networking best practices to ensure that data is safe and always available and that network access is never interrupted.

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

STAR PHYSICAL TOPOLOGY

UNDERSTANDING THE OBJECTIVE

Every network depends on a physical layout, or topology.The physical topology describes how servers, workstations, printers, and other devices are physically connected in a LAN (local-area network) or WAN (wide-area network). While most modern networks contain 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 physical topology 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, which repeats the data to all other devices on the segment. The recipient node then picks up the data addressed to it. ◆ Any single physical wire on a star network only connects two devices, so a cabling problem 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 segment where the destination node is located, so the destination node can pick it up. ◆ Star topologies are more fault-tolerant and provide better performance than bus or ring topologies. On Ethernet networks, a single cable or node fault will not immobilize a star-wired network. However, star networks require more cabling and devices and are generally more expensive than bus or ring networks. ◆ Star networks can be easily upgraded, moved, and interconnected with other networks. ◆ Star topology networks that divide workstation groups and connectivity devices into 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. Because it is so popular, you should be familiar with the way connectivity devices and nodes are arranged in this topology.As your experience with star topology networks increases, you will also learn how to troubleshoot and add to them.

O B J E C T I V E S

PRACTICE TEST QUESTIONS

1. Which of the following is an advantage to using star topology networks over using bus or ring topology 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 breaches b. to increase available bandwidth by sending multiplexed signals c. to arbitrate addressing conflicts between sending nodes d. 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 how many physical cables? a. three b. four c. five d. 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 computers b. a WAN that connects freelance writers across the nation c. a LAN that connects a dozen computers in an insurance company d. 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 resistor b. 50-ohm resistor c. 100-ohm resistor d. Terminators are not used on star-wired networks.

PRACTICE TEST QUESTIONS

1. On a bus topology, terminators eliminate the possibility of. a. crosstalk b. noise c. signal bounce d. EMI 2. How many nodes share a single channel on a bus topology? a. all connected nodes b. one c. two d. four 3. Which type of cable are you most likely to find on networks that use a bus topology? a. UTP cable b. STP cable c. Coaxial cable d. Fiber-optic cable 4. What is one advantage of using a network based on the bus topology over a network based on the star 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. Terminator b. Ohmmeter c. Transceiver d. Tracker 6. You are the administrator for a LAN that uses the bus topology to connect seven workstations. Each workstation runs Windows XP. What would you need to do if you wanted to add a workstation to the 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.

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

MESH PHYSICAL TOPOLOGY

UNDERSTANDING THE OBJECTIVE

In a LAN,a mesh topology is one in which at least some of the nodes are connected via more than one link.In aWAN,a mesh topology is one in which some of the locations are connected via more than 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 they require the most equipment, connectivity, setup, and maintenance. However, they are also the most fault-tolerant physical topologies. ◆ A less expensive, yet still fault-tolerant alternative to full mesh topologies is a partial mesh topology , in which only some of the nodes on a network are directly connected to other nodes, as shown in the following diagram:

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

OBJECTIVES ON THE JOB

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

O B J E C T I V E S

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

RING PHYSICAL TOPOLOGY

UNDERSTANDING THE OBJECTIVE

A ring topology connects nodes using a single channel in a ring. In order to determine which node can transmit data at any given time, ring networks use tokens that circulate on the network 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 other packets 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 that wants to send data picks up the constantly circling token, adds its data, sends the packet, and when the recipient accepts the packet, releases the token so that other nodes can transmit. ◆ A disadvantage of the ring topology is that one defective node can take down the network. ◆ 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 hybrid topology. In this configuration, the physical topology is a star while the logical topology is a ring.

OBJECTIVES ON THE JOB

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

O B J E C T I V E S

PRACTICE TEST QUESTIONS

1. In which two of the following topologies will the addition of more nodes detrimentally affect the network’s performance? a. bus b. star c. ring d. mesh 2. At any given time, how many tokens circulate on a simple ring network? a. one b. five c. ten d. 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-bus b. ring-bus c. ring-tree d. star-ring 5. In how many directions is data transmitted on a ring network? a. one b. two c. 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 code b. transcender c. token d. A node on a ring network can transmit at any time without restriction.

PRACTICE TEST QUESTIONS

1. The 802.2 standards apply to what sublayer of the Data Link layer? a. the MAC sublayer b. the Logical Link Control sublayer c. the Access Method sublayer d. the Network Transmission sublayer 2. To which other standards body does IEEE contribute its recommendations? a. ISO b. OSI c. ITU d. ANSI 3. In what year was the IEEE 802 committee formed? a. 1980 b. 1990 c. 1995 d. 1998 4. Which of the following MAC sublayer specifications can work with the 802.2 sublayer specification? Choose all that apply. a. 802. b. 802. c. 802. d. 802. 5. Which of the following functions is handled by the 802.2 sublayer? a. issuing electrical signals onto the wire b. appending a physical address to a data frame c. appending a logical address to a data frame d. 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. True **or 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 communication b. to simplify the process of ensuring proper addressing between sending and receiving nodes c. to better articulate the difference between transmission and reception d. to accommodate evolving encryption techniques

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 Data Interface) networking technologies, including: Speed; Access method (CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) and CSMA/CD (Carrier Sense Multiple Access/Collision Detection)); Topology; and Media (continued):

802.3 (ETHERNET)

UNDERSTANDING THE OBJECTIVE

IEEE 802.3 standards specify the MAC sublayer requirements for Ethernet standards, including its network access method, CSMA/CD (Carrier Sense Multiple Access/Collision Detection), which allows 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 transmitting data over the signal (or carrier) on the communications channel before they begin to transmit. The term “Multiple Access” refers to the fact that several Ethernet nodes 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, it waits and checks again after a random (but brief) amount of time. If the channel is free, 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 NIC determines that its data has been involved in a collision, it will first propagate the collision throughout the network by using a jamming signal, ensuring that no other station attempts to transmit. Then the NIC remains silent for a random period 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 wants to transmit data, it sends out a jamming signal, then waits a specific period of time for all nodes to receive the jam. The node then transmits its data. During the data transmission, 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 that implement CSMA/CA are AppleTalk and wireless 802.11 RTS/CTS. ◆ IEEE’s 802.3 standards apply to all wire-bound Ethernet network types, including 10BASE-T (10 Mbps), 100BASE-TX (100 Mbps), 1000BASE-T (1 Gpbs) and 10G BASE-xR (10 Gbps) Ethernet. These networks may use bus, star, or star-wired bus physical topologies.

OBJECTIVES ON THE JOB

Since the IEEE 802.3 standard forms the basis of the most popular networks in use today, you should be thoroughly familiar with its specifications. In particular, you should understand CSMA/CD, its advantages and disadvantages, and how it pertains to network performance on all Ethernet networks.

O B J E C T I V E S

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 Data Interface) networking technologies, including: Speed; Access method (CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) and CSMA/CD (Carrier Sense Multiple Access/Collision Detection)); Topology; and Media (continued):

802.5 (TOKEN RING)

UNDERSTANDING THE OBJECTIVE

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 less common because of its more costly implementation. ◆ Token Ring networks use the token-passing network access method and a star-ring hybrid 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, the active monitor maintains the timing for ring passing, monitors token and frame transmission, detects lost tokens, and corrects errors when a timing error or other disruption occurs. Only one workstation on the ring can act as the active monitor at any given time. ◆ In token passing, a 3-byte token circulates around the network. When a station has something to send, it picks up the token, changes it to a frame, and then adds the header, information, and trailer fields. Each node reads the frame as it traverses the 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 can then be reused. ◆ The token-passing control scheme ensures high data reliability (no collisions) and an efficient use of bandwidth. It also does not impose distance limitations on the length of a LAN segment, unlike CSMA/CD.

OBJECTIVES ON THE JOB

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

O B J E C T I V E S

PRACTICE TEST QUESTIONS

1. Which of the following data transmission speeds would be used on 802.5 networks? Choose all that apply. a. 1 Mbps b. 4 Mbps c. 10 Mbps d. 16 Mbps 2. What network access method is specified by the 802.5 standard? a. CSMA/CA b. demand priority c. token-passing d. CSMA/CD 3. What type of media could be used by a network that relies on the 802.5 standard? Choose all that apply. a. coaxial cable b. UTP c. STP d. single-mode fiber 4. At which sublayer of the Data Link layer do 802.5 standards operate? a. MMC sublayer b. MAC sublayer c. LLC sublayer d. TMC sublayer 5. What network component is responsible for applying 802.5 standards to an electrical signal? a. RJ-45 connector b. RJ-11 connector c. cabling d. 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. standard. 7. What type of physical topology would be used on an 802.5 network? a. bus b. star-wired bus c. star-wired ring d. cube

PRACTICE TEST QUESTIONS

1. What networking component is responsible for applying 802.11 standards to an electrical signal? a. NIC b. portal c. base station d. antenna 2. Which of the following media is the least secure? a. fiber-optic cable b. UTP c. direct infrared d. spread-spectrum RF 3. What is the theoretical maximum throughput of an 802.11b wireless LAN? a. 2.4 Mbps b. 5 Mbps c. 11 Mbps d. 54 Mbps 4. Which radio frequency band is specified for use by the 802.11b standard? a. 1.5 GHz b. 2.4 GHz c. 5.5 GHz d. 6.2 GHz 5. Which of the following network access methods do 802.11 devices use? a. CSMA/CA b. demand priority c. token-passing d. 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 buildings b. a LAN that connects 50 inventory control personnel in a warehouse to a database server c. a WAN that connects 120 mobile sales people with their corporate headquarters d. 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 layer b. Data Link layer c. Network layer d. Transport layer

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 Data Interface) networking technologies, including: Speed; Access method (CSMA/CA (Carrier Sense Multiple Access/Collision Avoidance) and CSMA/CD (Carrier Sense Multiple Access/Collision Detection); Topology; and Media (continued):

FDDI (FIBER DISTRIBUTED DATA INTERFACE)

UNDERSTANDING THE OBJECTIVE

FDDI (Fiber Distributed Data Interface) is a logical topology whose standard was originally specified by ANSI in the mid-1980s. It uses a double fiber-optic ring to transmit data at speeds of 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 frequently find it supporting network backbones that were installed in the late 1980s and early 1990s. ◆ A popular implementation of FDDI involves connecting LANs located in multiple buildings, such as those on college campuses. FDDI links can span distances as far as 62 miles. ◆ Because Ethernet technologies have developed faster transmission speeds and are more compatible with other existing network technologies, FDDI is no longer the much-coveted technology that it was in the 1980s. ◆ Its reliance on fiber-optic cable ensures that FDDI is more reliable and more secure than transmission methods that depend on copper wiring. Another advantage of FDDI is that it works well with Ethernet 100BASE-TX technology. ◆ One drawback to FDDI technology is its high cost relative to Fast Ethernet (costing up 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 also relies on the same token-passing routine that Token Ring networks use. However, unlike Token Ring technology, FDDI runs on two complete rings. During normal operation, the primary FDDI ring carries data, while the secondary ring is idle. The secondary ring will assume data transmission responsibilities should the primary ring experience Physical layer problems.

OBJECTIVES ON THE JOB

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

O B J E C T I V E S