1. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.1 Computer Networks and Internets with Internet Applications, 4e By Douglas E. Comer Lecture PowerPoints By Lami Kaya, LKaya@ieee.org

2. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.2 Chapter 17 Internetworking: Concepts, Architecture, and Protocols

3. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.3 Topics Covered 17.1 Introduction 17.2 The Motivation For Internetworking 17.3 The Concept Of Universal Service 17.4 Universal Service In A Heterogeneous World 17.5 Internetworking 17.6 Physical NW Connection With Routers 17.7 Internet Architecture 17.8 Achieving Universal Service 17.9 A Virtual NW 17.10 Protocols For Internetworking 17.11 Significance Of Internetworking And TCP/IP 17.12 Layering And TCP/IP Protocols 17.13 Host Computers, Routers, And Protocol Layers

4. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.4 17.1 Introduction This chapter discusses the motivation for internetworking, introduces the HW components used, describes the architecture of connection, and discusses the significance of the concept

5. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.5 17.2 The Motivation For Internetworking Each NW technology is designed to fit a specific set of constraints –LANs to provide high speed for short distances, –WANs to provide communication across large areas. –No single NW technology is best for all needs. A large organization with diverse NW requirements needs may multiple physical NW –if the organization chooses different NW for each task, the organization will have several types of NW –Ethernet might be the best solution for a given site –Frame Relay service might be used to interconnect remote sites

6. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.6 17.3 The Concept Of Universal Service In many early installations, –Each computer was attached to a single NW –To choose a computer/NW appropriate for each task –Reduce productivity and complications Most modern systems allow communication between any two computers –known as “universal service” –A user on any computer in any part of an organization can send messages or data to any other user

7. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.7 17.4 Universal Service In A Heterogeneous World Does universal service mean an organization needs to adopt a single NW technology? Is it possible to have universal service across multiple NW that use multiple technologies? Electrical incompatibilities make it impossible to form a large NW merely by interconnecting the wires Extension techniques such as bridging cannot be used with heterogeneous NW technologies – incompatible packet formats and different addressing schemes A frame created for one NW technology cannot be transmitted on a NW that uses a different technology

8. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.8 17.5 Internetworking Researchers have devised a scheme that provides universal service among heterogeneous NW –called “internetworking” or “Internet” SW on all the hosts provides universal service Internetworking is quite general –an internet is not restricted in size –connecting a few NW or thousands of NW Number of computers attached to each NW in an internet can vary –some NW have no computers attached –while others may have hundreds attached

9. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.9 17.6 Physical NW Connection With Routers The basic HW component used to connect heterogeneous NW is a router Physically, routers resemble bridges –each router is a special-purpose HW system –contains a processor and memory as well as a separate I/O interface for each NW to which it connects. The NW treats a connection to a router the same as a connection to any other computer. A cloud is used to depict each NW instead of a line or a circle –Router connections are not restricted to a NW technology –A router can connect two LANs, a LAN and a WAN, or two WANs

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11. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.11 17.7 Internet Architecture Figure 17.2 shows connected networks using routers The figure shows each router with two connections –However, an organization seldom uses a single router to connect all of its NW. There are two reasons: –The router processor may be insufficient to handle all the traffic –Redundancy improves reliability to avoid a single point of failure, continuously monitors internet connections, and instructs the routers to send traffic along alternative paths when a NW or router fails When planning, an organization must choose a design that meets –reliability –capacity –cost

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13. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.13 17.8 Achieving Universal Service The goal of internetworking –universal service across heterogeneous NW To provide universal service among all computers –routers must agree to forward from a source to destination The task is complex –frame formats –addressing schemes –etc, can differ

14. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.14 17.9 A Virtual NW Internet SW –provides the appearance of a single, seamless communication system to which many computers attach –hides the details of physical NW connections, physical addresses, and routing information –neither users, nor application programs are aware of the underlying physical NW or the routers that connect them We say that an internet is a virtual NW system –because the communication system is an abstraction –although a combination of HW and SW provides the illusion of a uniform NW system, no such NW exists Figure 17.3 illustrates the virtual NW concept as well as a corresponding physical structure

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17. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.17 17.10 Protocols For Internetworking Although many protocols have been adapted for use in an internet is the most widely used –TCP/IP Internet Protocols TCP/IP was the first set of protocols developed for use in an internet. –Work on TCP/IP began in the 1970s –U.S. military funded research through Advanced Research Projects Agency (ARPA) by Department of Defense (DoD) –Sometimes known as DARPA The military was among the first organizations to have multiple physical NW

18. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.18 17.11 Significance Of InterNWing And TCP/IP Internet with (Uppercase I), refers to the global Internet Research on internetworking and TCP/IP produced dramatic results –Internetworking has become one of the most important issue –Internet technology has revolutionized computer communication Demand for internetworking products has affected most companies –modified their protocol designs to accommodate internetworking –Old protocols were proprietary designed to work with one NW technology and one physical NW at a time To provide internetworking capabilities, companies have extended the designs in two ways: –able to work with many NW technologies –and new features have been added

19. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.19 17.12 Layering And TCP/IP Protocols Internet model contains five layers as Figure 17.4 illustrates Layer 1: Physical –corresponds to basic NW HW Layer 2: NW Interface –specify how to organize data into frames and how a computer transmits frames over a NW Layer 3: Internet –specify the format of packets sent across an internet as well as the mechanisms used to forward packets Layer 4: Transport –specify how to ensure reliable transfer Layer 5: Application –gives details of NW applications

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21. © 2007 Pearson Education Inc., Upper Saddle River, NJ. All rights reserved.21 17.13 Host Computers, Routers, And Protocol Layers TCP/IP defines the term host computer –refer to any computer system that connects to an internet and runs applications Both hosts and routers need TCP/IP protocol SW –However, routers do not use protocols from all layers –In particular, a router does not need Layer 5 protocols for applications Some routers do run applications that permit a manager to administer the router remotely