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TCP/IP: The Internet Layer Protocol

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Learn the basics of the Internet layer protocol from the experts at NIIT. Format and transmit IP Datagrams.
This chapter is from the book

The Internet Layer

The Internet layer in the TCP/IP reference model is responsible for transferring data between the source and destination computers. The Internet layer accepts data from the Transport layer and passes the data to the Network Interface layer. The following are the functions of the Internet layer:

  • Transmitting data to the Network Interface layer.

  • Routing the data to the correct destination. This layer takes care of sending the data through the shortest route if more than one route is available. In addition, if a route through which a datagram is to be sent has problems, the datagram is sent through an alternate route.


The path taken by a datagram to reach the destination is called the route.

  • Handling errors and fragmentation and reassembling, all of which are discussed in the sections that follow.

The protocols that operate in this layer are Internet Protocol (IP) and Internet Control Message Protocol (ICMP), shown in Figure 3.1. ICMP works with IP to handle errors in data transmission.

Figure 3.1 Internet Protocol and Internet Control Message Protocol operate from the Internet layer of the TCP/IP reference model.


The version of IP that is discussed in this book is called IPv4. IPv4 is the version of IP that was created to provide communication over a TCP/IP-based network. With the growing number of LANs and WANs, the address space that is provided by IPv4 is becoming insufficient. Moreover, requirements due to technological changes led to the creation of a new version of IP called IPv6.

To learn more about IPv6, see "IPv6," p. 403

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