CompTIA Security+ Question A-93

The concept of rendering data passing between two points over an IP based network impervious to all but the most sophisticated advanced persistent threats is BEST categorized as which of the following?

A. Stream ciphers
B. Transport encryption
C. Key escrow
D. Block ciphers

Answer: B

Explanation:
Transport encryption is the process of encrypting data ready to be transmitted over an insecure network. A common example of this would be online banking or online purchases where sensitive information such as account numbers or credit card numbers is transmitted.

Transport Layer Security (TLS) is a protocol that ensures privacy between communicating applications and their users on the Internet. When a server and client communicate, TLS ensures that no third party may eavesdrop or tamper with any message. TLS is the successor to the Secure Sockets Layer (SSL).

CompTIA Network+ Question B-42

When troubleshooting a network problem, browsing through the log of a switch, it is discovered that multiple frames contain errors. In which of the following layers does the problem reside? (Select TWO).

A. Layer 2
B. Layer 3
C. Layer 5
D. Transport layer
E. Data link
F. Physical layer

Correct Answer: AE

Explanation:
Layer 2 of the OSI reference model is the data-link layer. Components of the data-link layer include frame-format, Media Access Control (MAC) addressing, protocol identification and error detection.
When data is being sent, it is split into protocol data units (PDUs) as it passes through the layers of the OSI model. The PDUs have different names as they are passed through the layers of the OSI model. In layer 2, the PDU is called a ‘Frame’.
The most common protocol specified in the data-link layer is Ethernet and the most common network component in the data-link layer is a network switch.
In this question, problems are discovered with Ethernet frames by examining the logs in a network switch. Therefore, for this question, we are working in Layer 2, the data-link layer.

CompTIA Network+ Question A-39

When a client calls and describes a problem with a computer not being able to reach the Internet, in which of the following places of the OSI model would a technician begin troubleshooting?

A. Transport layer
B. Physical layer
C. Network layer
D. Session layer

Correct Answer: B

Explanation:
The bottom layer of the OSI reference model is Layer 1, the physical layer.
The physical layer is the layer that defines the hardware elements of a network. These elements include:
Network Interface Cards Network topology Network cabling
The type of signals used for data transmissions
When troubleshooting a network connectivity issue, the first thing you would check is the computer’s network cabling, the network card etc. In other words, the computer’s physical connection to the network.

CompTIA Network+ Question A-24

Which of the following PDUs is used by a connectionless protocol?

A. Frames
B. Segments
C. Streams
D. Datagram

Correct Answer: D

Explanation:
UDP is a connectionless transport protocol that operates in the transport layer of the OSI model. UDP stands for User Datagram Protocol. PDUs (Protocol Data Units) used by UDP are known as Datagrams.