GCFA · Question #110
Which of the following types of firewall functions at the Session layer of OSI model?
The correct answer is D. Circuit-level firewall. Circuit-level firewalls operate at Layer 5 (Session layer) of the OSI model by monitoring and validating TCP/UDP session handshakes before permitting traffic to flow.
Question
Which of the following types of firewall functions at the Session layer of OSI model?
Options
- AApplication-level firewall
- BSwitch-level firewall
- CPacket filtering firewall
- DCircuit-level firewall
How the community answered
(37 responses)- A14% (5)
- B5% (2)
- C3% (1)
- D78% (29)
Why each option
Circuit-level firewalls operate at Layer 5 (Session layer) of the OSI model by monitoring and validating TCP/UDP session handshakes before permitting traffic to flow.
An application-level firewall (proxy firewall) operates at Layer 7 (Application layer), performing deep inspection of application-protocol content such as HTTP, FTP, or DNS.
Switch-level firewall is not a recognized OSI-based firewall classification; network switches operate at Layer 2 (Data Link layer) and do not perform firewall session or packet inspection by default.
A packet filtering firewall operates at Layers 3 and 4 (Network and Transport layers), making allow/deny decisions based solely on IP addresses, protocols, and port numbers without tracking session state.
A circuit-level gateway (circuit-level firewall) functions at the Session layer (Layer 5) of the OSI model, inspecting the TCP three-way handshake to determine whether a session is legitimate before relaying packets. It does not inspect packet payload contents, making it faster than application-layer inspection while still enforcing session-based access control. This distinguishes it from packet filters (Layers 3-4) and application proxies (Layer 7).
Concept tested: Firewall types and OSI layer classification
Source: https://www.cloudflare.com/learning/security/what-is-a-firewall/
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