What is the RFC-specified default fragment expiry time?

What is the RFC-specified default fragment expiry time?

• A. 30 seconds
• B. 1-2 minutes
• C. 5-10 minutes
• D. 1 hour

Answer: (B)

Fragment reassembly timer is what controls how long a host or router will hold onto IP fragments before discarding them if the other pieces don’t arrive. The RFCs set a window that’s long enough to accommodate typical network delays but short enough to prevent fragments from consuming memory forever. That window is about one to two minutes. So, the default expiry time for fragments is in the 1- to 2-minute range. Seeing this timeout helps you understand why you can’t always reconstruct every packet from fragments in a trace—fragments arriving after the timer has expired will be discarded, and you’ll only see partial reassembly or none at all. The other options are either too short to account for normal network delays or too long for practical resource management.

Fragment reassembly timer is what controls how long a host or router will hold onto IP fragments before discarding them if the other pieces don’t arrive. The RFCs set a window that’s long enough to accommodate typical network delays but short enough to prevent fragments from consuming memory forever. That window is about one to two minutes. So, the default expiry time for fragments is in the 1- to 2-minute range.

Seeing this timeout helps you understand why you can’t always reconstruct every packet from fragments in a trace—fragments arriving after the timer has expired will be discarded, and you’ll only see partial reassembly or none at all. The other options are either too short to account for normal network delays or too long for practical resource management.