Chapter 21: Internet Protocol (IP)

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The Internet Protocol (IP) is the heart of the Internet. Networks running different protocols are connected together to form the global network because of the IP. In this chapter, we will study IP version 4, which is presently running on most of the routers and end systems. We also will discuss IP Version 6 which is the next version of the IP that is being deployed and that will become predominant in coming years. We also will discuss various routing protocols. Details of Internet Control Message Protocol (ICMP) are also presented in this chapter.

21.1 OVERVIEW OF INTERNET PROTOCOL

Internet Protocol (IP) is the protocol that enables various networks to talk to each other. IP defines the data formats for transferring data between various networks. It also specifies the addressing and routing mechanisms. The service delivered by IP is unreliable connectionless packet service. The service is unreliable because there is no guarantee that the packets will be delivered—packets may be lost if there is congestion, though "best-effort" is made for the delivery. The packets may not be received in sequence, packets may be duplicated, and packets may arrive at the destination with variable delay. The service is connectionless because each packet is handled independently. IP defines the rules for discarding packets, generating error messages, and how hosts and routers should process the packets.

The functions of the IP layer are addressing and routing. IP provides a connectionless service: each packet is handled independently by the router.

IP is implemented as software. This software must run on every end system and on every router in any internet that uses the TCP/IP protocol suite.

Note 

The IP software runs on every router as well as on every end system.

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