A TCP/IP network layer protocol for addressing and routing packets of data between hosts on a TCP/IP network. Internet Protocol (IP) is a connectionless protocol that provides best-effort delivery using packet-switching services.
IP does not guarantee delivery of data. The responsibility for guaranteeing delivery and sending acknowledgments lies with the higher transport-level protocol Transmission Control Protocol (TCP).
The structure of an IP packet is shown in the following diagram. Some of the more important header fields include
IP packets are routed in the following fashion:
Graphic I-11. The structure of an IP packet.