Which of the following is the most likely function to be decremented when a tool is used to measure the distance between two locations on the internet?

GRE (Generic Routing Encapsulation) is a tunneling protocol, not a field decremented to measure hop count.

Tools like `traceroute` or `tracert` operate by sending packets with an incrementally increasing Time-To-Live (TTL) value; each router decrements the TTL, and when it reaches zero, the packet is discarded, and an ICMP 'Time Exceeded' message is sent back to the source.

VPN (Virtual Private Network) provides secure, private network connections over a public network, but it's not a field that is decremented for distance measurement.

QoS (Quality of Service) refers to mechanisms for managing network traffic and prioritizing bandwidth, not a field that decreases with each hop.