IP is central to the TCP/IP stack—all other TCP/IP protocols use IP—and all data passes through it. IP is a connectionless protocol and has some limitations. If IP attempts packet delivery and in the process a packet is lost, delivered out of sequence, duplicated, or delayed, neither sender nor receiver is informed. Packet acknowledgement is handled by a higher-layer transport protocol, such as TCP.
IP is responsible for addressing and routing packets between hosts, and for fragmentation. Fragmentation is the process of breaking a datagram into smaller pieces for inter-network routing. IP fragments packets prior to sending them and reassembles them upon receipt.
Note Winsock applications can send packets, but cannot affect packet routing or fragmentation.
For more information about IP addressing, see IP Addressing.