Why do we say that Internet Protocol (IP) is an unreliable protocol?

Question

Can someone provide me some details that how this conversion is possible by which it compresses the IP header (Minimum of 20 bytes) in to Token that is 1 to 4 bytes ?

Answer 1

IP is a unreliable protocol because it does not guarantee the delivery of a datagram to its destination. The reliability must be provided by the upper layer protocols like TCP/SCTP. IP does not support flow control, re-transmission, acknowledgement and error recovery.