| The following sections provide you with the opportunity to review what you learned in this chapter and to test yourself. The Facts For the exam, don't forget these important key concepts: In a star topology, each device on the network connects to a centralized device via a single cable. Computers in a star network can be connected and disconnected from the network without affecting any other systems. In a star configuration, all devices on the network connect to devices that act as connectivity points for the network, and these devices create a single point of failure on the network. The most common implementation of the physical star topology is the Ethernet 10BaseT standard, although most new installations are 100BaseT, at a minimum. In the ring topology, the network layout forms a complete ring. Computers connect to the network cable directly or, far more commonly, through a specialized network device. Breaking the loop of a ring network disrupts the entire network. Even if network devices are used to create the ring, the ring must still be broken if a fault occurs or the network needs to be expanded. The mesh topology requires each computer on the network be connected to each device. This configuration provides maximum reliability and redundancy for the network. 802.3 defines the Carrier Sense Multiple Access with Collision Avoidance Detection (CSMA/CA) media access method used in Ethernet networks. This is the most popular networking standard used today. 802.5 defines Token Ring networking. All cards in a Token Ring network must operate at the same speed. Ring networks are most commonly wired in a star configuration. In a Token Ring network, a multistation access unit (MSAU) is equivalent to a hub or switch on an Ethernet network. To connect MSAUs, the ring in and ring out configuration must be properly set. FDDI uses a dual-ring configuration for fault tolerance. Four wireless standards are found under the IEEE 802.11 designation; these include 802.11, 802.11a, 802.11b, and 802.11g. Wireless standards use radio frequency as the transmission media, and they all use the CSMA/CA access method. Wireless antennas are typically measured in dBi and are either omni-directional or directional. Wireless antennas boost the range and compensate for interference affecting a wireless signal. Infrastructure wireless topology uses an access point to extend the standard wired LAN. Wireless clients communicate with the AP to access the wires LAN. Ad-hoc networking is the connecting of wireless devices together without using a wireless access point. Communication between a client and the AP requires both to use a common SSID, wireless channel, and security channel.
Key Terms LANs, WANs, and PANs Peer-to-peer and client/server networking models Physical topology Logical topology Bus Ring Star Mesh Wireless IEEE 802.2, 802.3, 802.5, and 802.11 FDDI Infrastructure topology Ad hoc topology 802.11, 802.11a, 802.11b, 802.11g Wireless antenna SSID Wireless channel
Exam Prep Questions | 1: | Which of the following standards uses a dual ring configuration for fault tolerance? A. 802.3 B. FDDI C. 802.5 D. 802.2
| | 2: | Which of the following access methods is associated with Ethernet networks? A. CSMA/CD B. CSMA/CA C. Token Passing D. Demand Polling
| | 3: | You have been asked to install a network that will provide the network users with the greatest amount of fault tolerance. Which of the following network topologies would you choose? A. Star B. Ring C. Mesh D. Bus
| | 4: | Which of the following access methods is associated with the 802.11b standard? A. CSMA/CD B. CSMA/CA C. Token Passing D. Radio Waves
| | 5: | Which of the following topologies allow for network expansion with the least amount of disruption for the current network users? A. Bus B. Ring C. 802.5 D. 802.4 E. Star
| | 6: | Which of the following are functions of the LLC? (Choose all that apply.) A. Data flow control B. Data fault tolerance C. Error control D. Token passing
| | 7: | Which of the following statements are associated with a bus LAN network? (Choose all correct answers.) A. A single cable break can cause complete network disruption. B. All devices connect to a central device. C. Uses a single backbone to connect all network devices. D. Uses a dual ring configuration.
| | 8: | Which of the following is associated with 802.3u? A. Gigabit Ethernet B. Fast Ethernet C. FDDI D. 802.2
| | 9: | What is the maximum speed for the 802.11b IEEE standard? A. 100Mbps B. 40Mbps C. 11Mbps D. 32Mbps
| | 10: | As a network administrator, you are called in to troubleshoot a problem on a token ring network. The network uses two MSAUs connected using the ring in ports on both devices. All network cards are set at the same speed. What is the likely cause of the problem? |
Answers to Exam Prep Questions| A1: | The correct answer is B. FDDI uses a ring network design but uses dual rings for fault tolerance. If there is disruption in one of the rings, network traffic can use the other ring. Answer A is incorrect, as the 802.3 specifies Ethernet networks and does not use a ring design. Answer C is incorrect, as 802.5 only defines a single ring. Answer D is incorrect, as 802.2 is the IEEE standard for the Logical Link Layer. | | A2: | The correct answer is A. CSMA/CD works by monitoring the computers that are sending data on the network. If two computers transmit data at the same time onto the network, a data collision will occur. Answer B is incorrect; CSMA/CA uses collision avoidance as an access method. Answer C is incorrect; token passing is associated with ring networks. Demand polling is an access method based on priority and is not used on Ethernet networks; therefore, answer D is incorrect. | | A3: | The correct answer is C. A mesh network uses a point-to-point connection to every device on the network. This creates multiple points for the data to be transmitted around the network and therefore creates a high degree of redundancy. The star, ring, and bus topologies do not offer fault tolerance. | | A4: | The correct answer is B. 802.11b specifies CSMA/CA as the access method for wireless networks. CSMA/CD is the access method associated with the IEEE 802.3 standards and is therefore incorrect. Token passing is an access method but is not used for wireless networks, making answer C incorrect. Answer D is incorrect, as radio waves represent the media used by wireless, not the access method. | | A5: | The correct answer is E. On a star network, each network device uses a separate cable to make a point-to-point connection to a centralized device such as a hub. With such a configuration, a new device can be added to the network by attaching the new device to the hub with its own cable. This process does not disrupt the users who are currently on the network. Answers A, B, C, and D are incorrect because the addition of new network devices on a ring or bus network can cause a disruption in the network and cause network services to be unavailable during the installation of a new device. 802.5 is the IEEE specification for a ring network, and 802.4 is the IEEE specification for a token bus. | | A6: | The correct answers are A and C. The LLC manages both the data flow control and error control for LAN networking standards such as 802.3, 802.5, and 802.11b. The function of the LLC is not to provide fault tolerance; therefore, answer B is incorrect. Similarly, the function of LLC is not associated with token passing. | | A7: | The correct answers are A and C. In a bus network, a single break in the network cable can disrupt all the devices on that segment of the network, a significant shortcoming. A bus network also uses a single cable as a backbone to which all networking devices attach. A star network requires networked devices to connect to a centralized device such as a hub or MSAU. Therefore, answer B is incorrect. A dual ring topology is associated with FDDI, not a bus network. | | A8: | The correct answer is B. 802.3u is the specification for Fast Ethernet under the original 802.3 IEEE standard. 802.3z is the specification for Gigabit Ethernet; therefore, answer A is incorrect. FDDI is not associated with 802.3u; FDDI uses a dual ring network design. 802.2 is the IEEE standard for the LLC sublayer. | | A9: | The correct answer is C. 802.11b allows for a transfer rate of 11Mbps. None of the other answers represent wireless speeds. | | A10: | The correct answer is C. To create the complete ring, the ring in (RI) port on each MSAU is connected to the ring out (RO) port on another MSAU. The last MSAU in the ring is then connected to the first, to complete the ring. |
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