A packet's Hop Limit determines how many times it can be forwarded before it is discarded. Each time a packet is forwarded, its Hop Limit value is decremented by one. When the Hop Limit reaches zero or when a router receives a packet with its Hop Limit set to zero, the packet is discarded and the source of the packet receives a Time Exceeded message indicating that the initial Hop Limit was too small or that the packet was caught in a routing loop.