Coaxial cable is called "coaxial" because it includes one physical channel that carries the signal surrounded (after a layer of insulation) by another concentric physical channel, both running along the same axis. The outer channel serves as a ground. Many of these cables or pairs of coaxial tubes can be placed in a single outer sheathing and, with repeaters, can carry information for a great distance. Source: STEINER, Kurt, Telecommunications and Network Security, Version 1, May 2002, CISSP Open Study Group (Domain Leader: skottikus), Page 14.
Question 77
What enables users to validate each other's certificate when they are certified under different certification hierarchies?
Correct Answer: A
Cross-certification is the act or process by which two CAs each certifiy a public key of the other, issuing a public-key certificate to that other CA, enabling users that are certified under different certification hierarchies to validate each other's certificate. Source: SHIREY, Robert W., RFC2828: Internet Security Glossary, may 2000.
Question 78
What is the framing specification used for transmitting digital signals at 1.544 Mbps on a T1 facility?
Correct Answer: B
Explanation/Reference: Explanation: Digital Signal Level 1 (DS - 1) provides 1.544 Mbps over a T1 line. Incorrect Answers: A: Digital Signal Level 0 (DS - 0) provides from 64 Kbps up to 1.544 Mbps on a Partial T1 line. C: There is no framing specification named DS-2. D: Digital Signal Level 3 (DS - 3) is a specification for T3, not for T1. References: Stewart, James M., Ed Tittel, and Mike Chapple, CISSP: Certified Information Systems Security Professional Study Guide, 5th Edition, Sybex, Indianapolis, 2011, p. 165
Question 79
Which of the following combinations would MOST negatively affect availability?
Correct Answer: A
Question 80
Of the following, which multiple access method for computer networks does 802.11 Wireless Local Area Network use?
Correct Answer: A
Explanation/Reference: Explanation: 802.11 Wireless Local Area Network uses CSMA\CA. Note: Carrier sense multiple access with collision avoidance (CSMA/CA) is a network multiple access method in which carrier sensing is used, but nodes attempt to avoid collisions by transmitting only when the channel is sensed to be "idle". Incorrect Answers: B: While Ethernet uses CSMA/CD, 802.11 Wireless does not. In wireless networks the collision detection of the alternative CSMA/CD is unreliable due to the hidden node problem. C: 802.11 uses Carrier sense multiple access (CSMA/CA). D: Wireless network uses CSMA/CA, not 802.11 RTS/CTS Exchange. References: Harris, Shon, All In One CISSP Exam Guide, 6th Edition, McGraw-Hill, New York, 2013, p. 578
