TIL Time To Live is, in practise, a hop limit and will be renamed in IPv6.
Time To Live (TTL) is one of the fields in the IPv4 header. TTL limits a datagram's lifetime, by telling a router whether or not the packet has been in the network for too long and should be discarded—thus prevents a data packet from circulating indefinetly.
In theory, under IPv4, TTL is measured in seconds, although every host that passes the datagram must reduce the TTL by at least one unit. However, in practice, the TTL field is reduced by one on every hop.
To reflect this practice, the field is renamed to hop limit in IPv6.
Image created with draw.io