1.1.d Explain IP operations

1.1.d [iv] TTL

Time to live (TTL) or hop limit is a mechanism that limits the lifespan or lifetime of data in a network. TTL prevents a data packet from circulating indefinitely. If the TTL field reaches zero before the datagram arrives at its destination, then the datagram is discarded and an ICMP error datagram (11 – Time Exceeded) is sent back to the sender.

Adam, Paul (2014-07-12). All-in-One CCIE V5 Written Exam Guide (Kindle Locations 1074-1075).  . Kindle Edition.