of higher level protocols, such as the Transmission Control Protocol (TCP) in the transport layer. In IPv4, a checksum is used to protect the header of each datagram. The checksum ensures that the information in a received header is accurate, however, IPv4 does not attempt to detect errors that may have occurred to the data in each packet. IPv6 does not include this header checksum, instead relying on the link layer to assure data integrity for the entire packet including the checksum. Core protocols The primary protocols in the internet layer are the Internet Protocol (IP). It is implemented in two versions, IPv4 and IPv6. The Internet Control Message Protocol (ICMP) is primarily used for error and diagnostic functions. Different implementations exist for IPv4 and IPv6. The Internet Group Management Protocol (IGMP) is used by IPv4 hosts and adjacent IP multicast routers to establish multicast group memberships. Security Internet Protocol Security (IPsec) is a suite of protocols for securing IP communications by authenticating and encrypting each IP packet in a data stream. IPsec also includes protocols for key exchange. IPsec was originally designed as a base specification in IPv6 in 1995, and later adapted to IPv4, with which it has found widespread use in securing virtual private networks. Relation to OSI model Because the internet layer of the TCP/IP model is easily compared directly with the network layer (layer 3) in the Open Systems Interconnection (OSI) protocol stack, the internet layer is often improperly called network layer. IETF standards See also End-to-end connectivity References External links Internet Protocol Network layer protocols