CISSP Practice

100. All the following are examples of media access control (MAC) sublayer protocols except:

a. Carrier sense multiple access (CSMA)

b. Ethernet

c. Advanced data communications control procedure (ADCCP)

d. Logical link control (LLC)

100. c. Advanced data communications control procedure (ADCCP) is an example of a sliding window protocol. The other three choices are examples of media access control protocols. ADCCP is a modified synchronous data link control (SDLC), which became high-level data link control (HDLC), and later became link access procedure B (LAPB) to make it more compatible with HDLC.

Carrier sense multiple access (CSMA) protocols listen to the channel for a transmitting carrier and act accordingly. If the channel is busy, the station waits until it becomes idle. When the station detects an idle channel, it transmits a frame. If collision occurs, the station waits a random amount of time and starts all over again. The goal is to avoid a collision or detect a collision (CSMA/CA and CSMA/CD). The CSMA/CD is used on LANs in the MAC sublayer and is the basis of Ethernet. Logical link control (LLC) protocol hides the differences between the various kinds of IEEE 802 networks by providing a single format and interface to the network layer. LLC forms the upper half of the data link layer with the MAC sublayer below it.

101. All the following are examples of sliding window protocols except:

a. Wavelength division multiple access (WDMA)

b. Synchronous data link control (SDLC)

c. High-level data link control (HDLC)

d. Link access procedure B (LAPB)

101. a. Sliding window protocols, which are used to integrate error control and flow, are classified in terms of the size of the sender’s window and the size of the receiver’s window. Sliding window protocols (e.g., SDLC, HDLC, and LAPB) are bit-oriented protocols and use flag bytes to delimit frames and bit stuffing to prevent flag bytes from occurring in the data. Wavelength division multiple access (WDMA) is an example of medium/media access control (MAC) sublayer protocol that contains two channels for each station. A narrow channel is provided as a control channel to signal the station, and a wide channel is provided so that the station can output data frames.

102. Data link layer VPN protocols such as the Cisco Layer 2 Forwarding (L2F) do not provide which of the following services?

a. RADIUS

b. TACACS+

c. Encryption

d. Protects the traffic between the ISP and the organization

102. c. Unlike PPTP and L2TP, L2F is intended for use between network devices, such as an ISP’s network access server and an organization’s VPN gateway. Like L2TP, L2F can use authentication protocols such as RADIUS and TACACS+. However, L2F does not support encryption.

103. The wireless local-area network (WLAN) using the IEEE 802.11i standard for a robust security network (RSN) does not support the protection of which of the following?

a. Stations and access points

b. Access points and authentication servers

c. Extensible authentication protocol and transport layer security

d. Stations and authentication servers

103. b. The WLAN IEEE 802.11 and its related standards explicitly state that protection of the communications between the access points and authentication server is not available. Therefore, it is important to ensure that communications between each access point and its corresponding authentication servers are protected sufficiently through cryptography. In addition, the authentication servers should be secured through operating system configuration, firewall rules, and other security controls. The data confidentiality and integrity protocol, such as the counter mode with cipher block chaining message authentication code protocol (CCMP), protects communications between stations and access points. The extensible authentication protocol (EAP) with transport layer security (TLS) is considered the most secure EAP method because it enables strong mutual cryptographic authentications of both stations and authentication servers using public key certificates.

104. Storing and hosting data on which of the following instant messaging (IM) architectures increases the risk of information theft, unauthorized access, and data tampering?

1. Private hosting

2. Public hosting

3. Client-to-client

4. Public-switched network

a. 1 and 2

b. 1 and 4

c. 2 and 3