Question

What is the typical method for restricting packet lifetime on the internet?

Answer 1

The maximum time the packet is allowed to remain in the internet system is defined in the header of the IP packet. The field is called Time to Live (TTL) and contains the seconds the packet can travel through the internet network.
 If this field contains the value zero, then the packet must be destroyed.
The intention is to cause undeliverable packets to be discarded, and to bound the maximum packet lifetime.