GIAC Security Essentials Certification (GSEC) — Question 6

What is the function of the TTL (Time to Live) field in IPv4 and the Hop Limit field in IPv6 In an IP Packet header?

Answer options

• A. These fields are decremented each time a packet is retransmitted to minimize the possibility of routing loops.
• B. These fields are initialized to an initial value to prevent packet fragmentation and fragmentation attacks.
• C. These fields are recalculated based on the required time for a packet to arrive at its destination.
• D. These fields are incremented each time a packet is transmitted to indicate the number of routers that an IP packet has traversed.

Correct answer: A

Explanation

The correct answer is A because the TTL and Hop Limit fields are indeed decremented each time the packet is forwarded by a router, which helps prevent routing loops by eventually discarding packets that cannot reach their destination. Options B and C are incorrect as they misrepresent the purpose of these fields, while option D inaccurately states that these fields are incremented, which is not their function.