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Internet layer is the second lowest layer of the TCP/IP reference model, which defines addressing of host, packaging and routing of data packets (datagram) from source to destination host through one or more similar or dissimilar types of networks.

Description

• Packages data received from upper layer into datagram by adding IP header to it, which consist of source and destination address that is used to forward the datagram between nodes and across networks.
• Performs addressing, routing and other functions using following protocols:
  • Internet Protocol (IP) - is a connectionless protocol used for addressing host and routing datagram's from source to destination host across one or more types of networks.
  • Address Resolution Protocol (ARP) - used to resolve host hardware address or MAC address when only its IP address of internet layer is known.
  • Reverse Address Resolution Protocol (RARP) - used to determine IP address, when its MAC address is known. It works reverse as ARP so the name RARP.
  • Internet Control Message Protocol (ICMP) - used to report error messages to host machine like destination host unreachable, time exceeded, invalid parameter etc.
  • Internet Group Management Protocol (IGMP) - used by host and routers to establish and manage IP multicast groups

Protocols used: IP (IPv4,IPv6), ICMP, ICMPv6, IGMP, ARP, RARP, DHCP etc.

Network devices: Router, Gateway.