IP is the mailroom of the TCP/IP stack, where packet sorting and delivery take place. At this layer, each incoming or outgoing packet is referred to as a datagram. Each IP datagram bears the source IP address of the sender and the destination IP address of the intended recipient. Unlike the MAC addresses, the IP addresses in a datagram remain the same throughout a packet's journey across an inter-network. IP layer functions are described below.

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.

Windows CE .NET 4.1 and later provides a dual protocol stack to support 32-bit IPv4 addresses and 128-bit IPv6 addresses. For information about the stack architecture, see Dual Stack Architecture.

The following table shows links to more information about IPv4.

See Also