CHAPTER CHAPTER

An Evolution of An Evolution of Physical Network Physical Network

ArchitecturesArchitectures

Chapter Objectives

• Discuss the different network hardware architectures that span varying sizes of business enterprises

• Provide an insight into LAN architectural evolution– Centralized, decentralized, mixed etc.

• Introduce the WAN architecture that is becoming increasingly relevant to the Internet

Chapter Modules

• Small Computer Networks• Medium Sized Computer Networks• Large Scale Computer Networks• Enterprise Computer Networks• Wide Area Networks

Chapter Focus on Functional Types

• Distributed– LAN driven– Current trend

• Centralized– Mini/Mainframe derived– Past trend and probably the future trend

• Combination– Distributed/ Centralized– Emerging trend

MODULE

Small Computer Networks

Major Types• Distributed

– Resources and executions are distributed over the network

– LAN• Centralized

– Resources and execution are confined to a central unit

– Multi-user Micro• A Unix multi-user computer operating under the

Unix operating system– Entry-level minicomputers also known as

departmental computers

LAN Evolution

File ServerApplication Server

(Client-ServerTechnology)

Thin-Clients &Terminal Servers

Distributedexecution

Cooperativeexecution

Centralizedexecution

Past Present Future

Mainframe architecture of the past

IBM 9370 Virtual Machine Example

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Suns Computer Network

Sun Enterprise Server

Pentium Pentium

Web Research

• Visit www.sun.com and obtain information about their Sun Enterprise servers– How are they networked together?– Choose a server to serve 25

workstations• Sun Enterprise Server 220R

MODULE

Medium Sized Computer Networks

Major Types• Centralized architecture

– Past, present and possible future – Minicomputers

• Decentralized architecture– Present– Very large LANs with Multiple segments

• Mixed architecture– Combination of both of the above– Large LAN with different network segments

Centralized Architecture: Medium Sized Computer

NetworkAS 400

Micro

MicroMicro

OS 400

Token Ring

OS2 / Warp

Web Research

• Visit www.ibm.com to obtain more information about the configuration of an AS 400 computer for:– Running OS/400– Functioning as a file server for a Windows

net work • Name the different IBM server families• Visit www.search400.com for additional

information on AS/400

Decentralized Architecture: A Switched

LANEthernet Switch

ClientClient Client Client ClientClient

Ethernet LAN Segments

Hub Hub

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MODULE

Large-Scale Computer Networks

Types

• Centralized Architecture• Decentralized Architecture• Combination of both

Examples

• Mainframe computer– Centralized

• Heterogeneous LAN– Distributed

Large Scale Centralized Computer Network

Concentrator

Term.

PC

Pc Mai

nfra

me

Fron

t-end

Proc

esso

r

DASDHard DiskModemServer

Mainframe Reference Terminology for

Equipment

• DCE (Data Communication Equipment)– Front-end Processor, Modem Server

and Concentrator for example• DTE (Data Terminal Equipment)

– Terminals, PCs and Printers for example

LAN Reference Terminology for

Equipment

• Internetworking devices– Switches, Routers etc.

• Clients or Workstations– PCs

Heterogeneous LAN Architecture

Router Switch

WSHubHub

WS

WS

WSWS WS WS WSWS

Server 3 Server 4

LANs With Servers/Minicomputers

Server 1Server 2

Switch• Switch network traffic between the LAN segments• Allows crossover traffic from one segment to

another segment• Otherwise, the network traffic is confined to the

individual segments• Used for connecting LAN segments that operate

under the same protocol• Performs Layer 2 functions

– Newer switches may also perform some routing which is a Layer 3 functions

• Such switches are called Layer 3 switches

Router

• Used for connecting LAN segments that operate under different protocols

• A more advanced device compared to the switch

• Routes traffic between different LANs• Performs Layer 3 functions

Web Research

• Visit www.whatis.com and get the definition for switches and gateways

• Access www.cisco.com to obtain further information on the following– Switch– Router

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MODULEMODULE

Enterprise Computer Networks

Major Types

• Centralized– Based on mainframes – Mainframe derived architecture

• Decentralized– Based on a backbone used of

connecting LANs and other computer systems

– LAN driven architecture

Enterprise Systems Network: Centralized

Architecture

Mainframe

Front End ProcessorMini-Computer

Term. Term. PCPC

Concentrator

LAN

ModemServer

Ter. Ter.ExternalLines

Gateway

Enterprise Systems/Campus Network

Fiber Optic Backbone(FDDI)

MainframeSystems

Bus LAN

RingLAN

ModemGateway

WAN Connection Star

LAN

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MODULE

Wide Area Networks

Types

• By virtue of its definition, it is a decentralized network

Wide Area Network Overview

Public Network(Frame RelayATM, X.25)

LANs

Terminal or Microcomputer

Campus Network

EnterpriseSystemsNetwork

MainframeSystems

Web Research

• Access a reference website such as www.whatis.com to obtain information on the following– ATM, Frame Relay, X.25– DS1, DS3 etc. – T1, T3 etc.– OC1, OC3 etc.

• Switches and Routers

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