TTL field in Networking and it's use

TTL or time to live field is a packet that is added with each and every packet that is routed in to the network. It is a 8 bit field. This is the value in min header of packet. Even there is no error in the packet, TTL value gets decreased every time. This changes the fragment offset as well as the checksum value too.  

This is a term used in IP packets to tell a network router that packet has been in the network for a long time or not and whether it is to be discarded or not. In IP version6 (IPv6), TTL field is also referred as hop limit/count. 

Protocols in the networking can receive the packets from a source or the frames in order or out of order, i.e. not in the sequence in which packets were sent. Our aim is to increase the efficiency of the protocols and channels, but at the same time we need to receive the data packets in order. This is the reason why TTL field is employed.

IP datagram header uses the TTL field, that is Time to Live field in the internet protocols, due to the reason that the packets should not loop for an indefinite or infinite time. This may be caused due to the fact that the packets were not delivered to the desired destination port. Due to which, they are looping into the network undelivered. 

If not destroyed, they will stay in the network and increase the load of the channel. Moreover, the channel capacity may decrease which will ultimately result in the decreased efficiency.