a. Multiplexers
b. Network interface cards
c. Concentrators
d. Front-end processors
39. b. A network interface card (NIC) is used in implementing local-area networks (LANs), not wide-area networks (WANs). It is a device used primarily within a LAN to enable a number of independent devices, with varying protocols, to communicate with each other. This communication is accomplished by converting each device protocol into a common transmission protocol.
A multiplexer is incorrect because it is a device that combines the functions of multiplexing and demultiplexing of digital signals. It combines two or more information channels onto a common transmission medium.
A concentrator is incorrect because it is a device that connects a number of circuits, which are not all used at once, to a smaller group of circuits for economy. It usually provides communication capability between many low-speed, usually asynchronous, channels and one or more high-speed, usually synchronous channels. Different speeds, codes, and protocols can be accommodated on the low-speed side. The low-speed channels operate in contention and require buffering. A concentrator permits a common path to handle more data sources than there are channels currently available within the path.
A front-end processor is incorrect because it is a programmed-logic or stored-program device that interfaces data communication equipment with the input/output bus or memory of a data processing computer.
40. Network-based firewalls should perform or implement which of the following?
1. Ingress filtering
2. Egress filtering
3. Deny-by-default rulesets for incoming traffic
4. Deny-by-default rulesets for outgoing traffic
a. 1 and 2
b. 1 and 3
c. 2 and 4
d. 1, 2, 3, and 4
40. d. Because network-based firewalls can restrict both incoming and outgoing traffic, they can also be used to stop certain worm infections within the organization from spreading to external systems. To prevent malware incidents, organizations should implement deny-by-default rulesets, meaning that the firewalls deny all incoming and outgoing traffic that is not expressly permitted. Organizations should also ensure that their network firewalls perform egress and ingress filtering. Egress filtering is blocking outgoing packets that should not exit a network. Ingress filtering is blocking incoming packets that should not enter a network.
41. A website has been vandalized. Which of the following should be monitored closely?
a. Illegal logging
b. Illegal privilege usage
c. Illegal file access
d. Illegal Web server shutdown
41. c. Selecting the illegal file access addresses the vandalism issue because that is what the attacker can benefit from the most. Files have critical data useful to an attacker. The other three choices are incidental.
42. The Voice over Internet Protocol (VoIP) technology can lead to which of the following?
a. Converged network
b. Ad hoc network
c. Content delivery network
d. Wireless sensor network
42. a. The Voice over Internet Protocol (VoIP) technology can lead to a converged network, where the latter combines two different networks such as data and voice networks, similar to the VoIP. Ad hoc network is a network of nodes near each other. Content delivery network delivers the contents of music, movie, sports, and/or news from a content owner’s website to end users. Wireless sensor network is used to provide security over buildings, machinery, vehicle operation, and environmental changes in a building (e.g., humidity, voltage, and temperature).
43. Which of the following transmission media is unsuitable for handling intra-building data or voice communications?
a. Twisted pair
b. Coaxial cable
c. Optical fiber
d. Microwave transmission
43. d. Microwave transmission is a point-to-point transmission using radio frequency spectrum signals and is commonly used as a substitution for copper or fiber cable. Because of this, it is not suitable for handling intra-building communications and is more appropriate for long-distance transmission. Twisted pair, made of copper wire, is best for low-cost, short-distance local networks linking microcomputers. Coaxial cable is rarely used medium for data transmission in local-area networking. Optical fiber uses light signals to carry a stream of data at extremely high modulation rates and is sturdy and secure.
44. From a corporation viewpoint, which of the following design objectives is most important for a local-area network?
a. Productivity
b. Availability
c. Throughput
d. Responsiveness
44. b. Availability is the ratio of the total time a functional unit is capable of being used during a given interval to the length of the interval. It is the time during which a functional unit can be used. What good are productivity, throughput, and response time if the system is shut down and not available? Therefore, system availability is the most important objective for a local-area network (LAN) or any other network.
45. Which of the following wiring schemes makes future network changes easier to implement?
a. Post wiring
b. Wiring on demand
c. Buildings with high ceilings
d. Cable conduits
45. d. Because the cost of wiring an existing building goes up with the height of the ceiling and rises even higher after the tenants have moved in, making the right decisions as early as possible can significantly reduce future costs. Dangling cables can be a safety hazard. Therefore, proactive thinking such as prewiring and cable conduits during building construction should be planned carefully to make future changes easier with less cost. Post-wiring and wiring on demand are reactive in nature, relatively expensive, and disruptive to work.
46. Which of the following is a disadvantage of satellite communications versus a conventional communications method?
a. User-owned stations
b. Cost
c. Frequency bands
d. Broadcast ability
46. c. Frequency bands are of two types: low and high frequency. All the lower frequency bands have become increasingly crowded, and developing higher frequencies is difficult and expensive. Also, transmission problems typically worsen at higher frequencies. In satellite systems, power must be increased at both the original transmission site (uplink) on earth and on the satellite. Increased satellite power generally increases costs.
The other three choices are advantages. Users purchase their own sending and receiving equipment. Satellites have a low-cost, point-to-multipoint broadcast capability that is most expensive to duplicate with conventional techniques.
47. Host-based firewalls can have a serious negative effect on system usability and user satisfaction with which of the following?
a. Deny-by-default rulesets for incoming traffic
b. Deny-by-default rulesets for outgoing traffic