Definition
Time to Live TTL is a value set on data or network packets that limits the lifespan of that data or packet. It is typically expressed as a number of hops or seconds, after which the data or packet is discarded. This mechanism prevents data from circulating indefinitely within a network, which could otherwise consume excessive resources. For instance, DNS records have TTL values that determine how long a resolver will cache a particular record before querying the authoritative name server again. A common point of confusion is mistaking TTL for a strict expiration date, when it is more accurately a maximum duration before revalidation or discard. Understanding TTL is crucial for network administrators and security professionals, appearing on certifications like CompTIA Security+ and CISSP.