Chapter 1. Internetworking Basics


The following topics are covered in this chapter:

  • Open System Interconnection Reference Model

  • Information Formats

  • Network Hierarchy

  • Connection-Oriented and Connectionless Network Services

  • Network Addressing

  • Flow Control

  • Error-Checking

  • Standards Organization

Internetworks are groups of individual networks functioning as a single large network. Internetworking refers to the technology and devices such as bridges, routers, and switches creating and administering these internetworks.

Two primary types of networks are used by customers:

  • Local-area networks (LANs) enable multiple users in a small geographical area, such as within a building or campus, to share files and exchange messages. LANs also enable the sharing of resources, such as file servers and printers. Some examples of LAN technology are Ethernet, Token Ring, or FDDI implementations.

    NOTE

    High-speed LANs and switched internetworks often are deployed throughout enterprise organizations because these internetworks enable high-bandwidth applications, such as videoconferencing, voice-over alternate technologies (such as VoIP and VoATM), and other multimedia applications.

  • Wide-area networks (WANs) interconnect geographically dispersed LANs enabling these LAN users to communicate and share resources with each other. Some examples of WAN technology are Frame Relay, Asynchronous Transfer Mode (ATM), or IP Virtual Private Network (VPN).

In comparison, the roads and highways used are an internetwork. Consider the neighborhood roads and streets as part of a LAN. People living in houses attached (by driveways) to these neighborhood roads are the LAN users. When people leave their houses and drive to work, they use an internetwork of larger thoroughfares and perhaps interstates. This larger internetwork is a WAN, carrying several users from one LAN (home neighborhood) to another (workplace neighborhood).

Just as these highways and interstates create one type of WAN, the railroad creates another and the routes taken by airplanes yet another. Figure 1-1 illustrates this highway/Frame Relay and railway/ATM comparison.

Figure 1-1. Internetwork Comparison

graphics/01fig01.gif

In order to use the railroad WAN, a user must be in the proper vehicle; in this case, a railroad car. An automobile, or bus, would not be able to use railroad tracks because the automobile is designed to be used on a different WAN: the highway. These differing vehicles are similar to different WAN technologies in use, such as Frame Relay, ATM, or Internet Protocol Virtual Private Networking (IP VPN). A Frame Relay user (automobile) could not use the railroad tracks (ATM) for transportation because the two are incompatible. Some form of conversion must be available to carry the data; in this case a person, from one network to another.

The key fundamental concept to an internetworked system is the Open System Interconnection (OSI) Reference Model, which is discussed in the following section.



Network Sales and Services Handbook
Network Sales and Services Handbook (Cisco Press Networking Technology)
ISBN: 1587050900
EAN: 2147483647
Year: 2005
Pages: 269

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