CISSP PRACTICE QUESTIONS – 20210619

Effective CISSP Questions

Which of the following is not a layer two protocol in terms of the ISO OSI reference model? (Wentz QOTD)
A. SLIP
B. CSMA/CD
C. OFDM
D. PPTP

Kindly be reminded that the suggested answer is for your reference only. It doesn’t matter whether you have the right or wrong answer. What really matters is your reasoning process and justifications.

My suggested answer is C. OFDM.

Wentz’s book, The Effective CISSP: Security and Risk Management, helps CISSP and CISM aspirants build a solid conceptual security model. It is a tutorial for information security and a supplement to the official study guides for the CISSP and CISM exams, and an informative reference for security professionals.

IEEE802.2 - Logical Link Control Layer (LLC)
IEEE802.2 – Logical Link Control Layer (LLC) (Image Credit: TelecomWorld101)

The data link layer is layer two of the ISO OSI reference model. “Link” means the connection between two directly connected or adjacent nodes, aka point-to-point (P2P) connection. “Data” implies the logical nature of the connection. The link is not necessarily a physical piece of wire or cable; it can be a virtual circuit or tunnel over a circuit or packet switching network. It’s called “Logical Link” in IEEE 802.2.

  • L2F, PPTP, and L2TP are well-known tunneling protocols used in VPN.
  • SLIP and PPP were commonly used in the era of dial-up using a modem.
  • CSMA/CD, CSMA/CA, Tokenpassing, and polling are typical media access control mechanisms.
  • DSSS, FHSS, are OFDM are signal modularization techniques used in wireless transmission.

SLIP

The Serial Line Internet Protocol (also SLIP) is an encapsulation of the Internet Protocol designed to work over serial ports and router connections. It is documented in RFC 1055. On personal computers, SLIP has largely been replaced by the Point-to-Point Protocol (PPP), which is better engineered, has more features, and does not require its IP address configuration to be set before it is established. On microcontrollers, however, SLIP is still the preferred way of encapsulating IP packets, due to its very small overhead.

Source: Wikipedia

CSMA/CD

Carrier-sense multiple access with collision detection (CSMA/CD) is a media access control (MAC) method used most notably in early Ethernet technology for local area networking. It uses carrier-sensing to defer transmissions until no other stations are transmitting. This is used in combination with collision detection in which a transmitting station detects collisions by sensing transmissions from other stations while it is transmitting a frame. When this collision condition is detected, the station stops transmitting that frame, transmits a jam signal, and then waits for a random time interval before trying to resend the frame.

Source: Wikipedia

PPTP

The Point-to-Point Tunneling Protocol (PPTP) is an obsolete method for implementing virtual private networks. PPTP has many well known security issues.

PPTP uses a TCP control channel and a Generic Routing Encapsulation tunnel to encapsulate PPP packets. Many modern VPNs use various forms of UDP for this same functionality.

The PPTP specification does not describe encryption or authentication features and relies on the Point-to-Point Protocol being tunneled to implement any and all security functionalities.

The PPTP implementation that ships with the Microsoft Windows product families implements various levels of authentication and encryption natively as standard features of the Windows PPTP stack. The intended use of this protocol is to provide security levels and remote access levels comparable with typical VPN products.

Source: Wikipedia

Reference


就 ISO OSI 參考模型而言,以下哪一項不是第二層協議?(Wentz QOTD)
A. SLIP
B. CSMA/CD
C. OFDM
D. PPTP


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