> The time is measured in units of seconds, but since every module that processes a datagram must decrease the TTL by at least one even if it process the datagram in less than a second, the TTL must be thought of only as an upper bound on the time a datagram may exist.
> The time is measured in units of seconds, but since every module that processes a datagram must decrease the TTL by at least one even if it process the datagram in less than a second, the TTL must be thought of only as an upper bound on the time a datagram may exist.
https://www.rfc-editor.org/rfc/rfc791.html
The equivalent field in IPv6 is named hop limit in recognition of how the TTL field is used in practice with IPv4:
https://www.rfc-editor.org/rfc/rfc2460.html