The Internet Layer in the TCP/IP Model

The Internet layer is responsible for logical transmission of data packets over the internet. It can be compared to the network layer of the OSI model.

The main functions of the internet layer are −

• It transmits data packets to the link layer.
• It routes each of the data packets independently from the source to the destination, using the optimal route.
• It reassembles the out-of-order packets when they reach the destination.
• It handles the error in transmission of data packets and fragmentation of data packets.

The protocols used in this layer are −

• Internet Protocol, IP − It is a connectionless and unreliable protocol that provides a best effort delivery service. It transports data packets called datagrams that travel over different routes across multiple nodes.
• Address Resolution Protocol, ARP −This protocol maps the logical address or the Internet address of a host to its physical address, as printed in the network interface card.
• Reverse Address Resolution Protocol, RARP − This is to find the Internet address of a host when its physical address is known.
• Internet Control Message Protocol, ICMP − It monitors sending the queries as well as the error messages.
• Internet Group Message Protocol, IGMP −It allows the transmission of a message to a group of recipients simultaneously.

The following diagram shows the network layer in the TCP/IP protocol suite −