19.2 THE INTERNET-THE GLOBAL NETWORK OF NETWORKS

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19.2 THE INTERNET—THE GLOBAL NETWORK OF NETWORKS

The Internet is a global network of computer networks. The TCP/IP protocol suite ensures that the diverse networks (LANs, corporate WANs, public data networks, etc.) can be internetworked for people to exchange information.

The entire TCP/IP protocol suite is the result of researchers working in universities and research laboratories. There is no central administrative authority to control the Internet. To ensure that the protocol suite meets the growing requirements, new developments have to take place and new protocols need to be defined. This activity is controlled by the Internet Architecture Board (IAB), which consists of a chairperson and a number of volunteers. IAB has two arms—the Internet Research Task Force (IRTF) and the Internet Engineering Task Force (IETF). IRTF coordinates the research efforts. IETF, consisting of a number of working groups, coordinates the engineering issues. Any new protocol to be implemented has to be approved by IETF. For each protocol, an RFC (Request for Comments) document is released by IETF.

The TCP/IP protocol stack provides the capability to interconnect different networks to form a global network of networks, called the Internet. All protocols to be used in the Internet have to be ratified by the Internet Engineering Task Force (IETF).

The entire Internet spanning the entire planet is just an extension of the small internet shown in Figure 19.2. The TCP/IP protocol suite enables any machine on the Internet to communicate with any other machine. The Internet is very dynamic—every day, a number of networks are connected, and some are disconnected as well. In spite of this dynamic nature, how do we get connected to any machine and access a Web site? It is the IP and the TCP that do the trick. If internetworking still appears a mystery, we will unravel the mystery in the next chapter, where we will study the TCP/IP protocol suite in detail.

Summary

To connect two or more networks is a challenging task because each network has its own protocols. In this chapter, we studied how a router can be used to network heterogeneous networks. The router's function is to do the necessary protocol conversion. The Internet, a global network interconnecting millions of networks, also uses the same mechanism. The IP and TCP protocols provide the means of achieving global connectivity. The Internet Protocol (IP) has to run on each and every router and each and every end system. The Transmission Control Protocol (TCP) has to run on each and every end system. The router is introduced in this chapter. We will study the details in later chapters.

References

• V. Cerf and R. Kahn. "A protocol for Packet Network Interconnection". IEEE Transactions on Communications, COM-22, Vol. 5, May 1974. This paper is written by the two persons who laid the foundation for the global Internet.

• D.E. Comer and D.L. Stevens. Internetworking with TCP/IP, Vol. III: Client/Server Programming and Applications, BSD Socket Version. Prentice Hall Inc., Englewood Cliffs, N.J., 1993. This book gives the complete software for internetworking using TCP/IP.

• http://www.ietf.org The Web site of IETF. You can obtain the RFCs (Request for Comments) that give the complete details of the Internet protocols from this site.

Questions

1. What are the various issues involved in networking of heterogeneous networks?

2. What are the functions of a gateway or router?

3. Draw a diagram that depicts the protocol stacks that need to run on the end systems (hosts) and the routers when an Ethernet LAN is connected to an X.25 WAN.

Exercises

1.	In your department/organization, if there are two LANs, study how they are connected and what network elements (bridge/router) interconnect the two LANs.
2.	Cisco Corporation is one of the leading suppliers of routers. Study the various internetworking products supplied by them. You can get the information from http://www.cisco.com.

Answers

1.	The type of network element used to interconnect two LANs depends on the protocols used in the two LANs. If both LANs run the same protocols, there is no need for any protocol conversion. If the LANs use different protocols, a network element needs to do the protocol conversion.
2.	The earlier routers were only to handle the protocol conversion for data application. Nowdays, routers are capable of handling voice/fax/video services as well. Cisco's AVVID (Architecture for Voice, Video, and Integrated Data) supports multimedia application and the routers are capable of protocol conversion between the PSTN and the Internet. Routers now support IP Version 6.

Projects

1. The IP (Internet Protocol) is the heart of internetworking. Study the source code for the IP implementation on a Linux system.

2. Develop a protocol converter that takes RS232 data in serial format and converts it into Ethernet format. The software has to read the data from a serial port on the PC and convert the data into Ethernet packets.

3. Embed the software developed in Project #2 in a processor-based system. You can use an embedded operating system such as Embedded Linux or RTLinux.

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