本当にド底辺なんだな 英語読める? 訳してとかいうなよ

http://tools.ietf.org/html/rfc791
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.