IPv4 (Internet Protocol version 4)

• Protocol: 8 bits identifying the higher-layer protocol that created the message contained in the Data field. Examples include Transmission Control Protocol (TCP) and User Datagram Protocol (UDP).

• Header Checksum: 16 bits used for error control in the header.The process is that of a cyclic redundancy check (CRC).

• Source IP Address: 32 bits containing the IP address of the source host.

• Destination IP Address: 32 bits containing the IP address of the destination host.

• IP Options, If Any: An optional, variable-length field used by gateways to control fragmentation and routing options.

• Padding: A variable-length field used only when necessary to ensure that the IP header extends to an exact multiple of 32 bits.

• Data: A variable-length field that contains the actual data content, or payload.

See also bandwidth, best effort, connectionless, CRC, datagram, dial-up, dotted decimal notation, error control, IETF, IPv4, IPv4 address, IPv6, gateway, header, host, Internet, network, Network Layer, octet, OSI Reference Model, packet, payload, PPP, protocol, QoS, router, segmentation, SLIP, TCP, TCP/ IP protocol suite, and UDP.

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