CISSP Question #1048: Real Exam Question with Answer & Explanation

Question

When conducting a remote access session using Internet Protocol Security (IPSec), which Open Systems Interconnection (OSI) model layer does this connection use?

Options

• ATransport
• BNetwork
• CData link
• DPresentation

Explanation

Internet Protocol Security (IPSec) is a protocol that provides secure and encrypted communication between two systems or networks over the internet. IPSec operates at the network layer of the Open Systems Interconnection (OSI) model, which is the third layer that is responsible for the routing and forwarding of the network packets, such as IP, ICMP, or ARP. IPSec uses two main protocols to secure the network communication: Authentication Header (AH) and Encapsulating Security Payload (ESP). AH provides data integrity and authentication for the IP packets, while ESP provides data confidentiality, integrity, and authentication for the IP packets. IPSec also uses two main modes to secure the network communication: transport mode and tunnel mode. Transport mode encrypts only the payload of the IP packet, while tunnel mode encrypts both the header and the payload of the IP packet. Transport, data link, or presentation are not the OSI model layers that IPSec uses. Transport is the fourth layer that is responsible for the reliable and error-free delivery of the data segments, such as TCP, UDP, or SCTP. Data link is the second layer that is responsible for the transmission and reception of the data frames, such as Ethernet, Wi-Fi, or PPP. Presentation is the sixth layer that is responsible for the formatting and conversion of the data, such as ASCII, JPEG, or SSL.

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