CHAPTER
An Evolution of Physical
Network Architectures
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
Past
Present
Future
File Server
Application Server
(Client-Server
Technology)
Thin-Clients &
Terminal Servers
Distributed
execution
Cooperative
execution
Centralized
execution
Mainframe architecture
of the past
IBM 9370 Virtual Machine
Example
END OF MODULE
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 Network
OS 400
Micro
AS 400
Token
Ring
Micro
Micro
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 LAN
Ethernet Switch
Hub
Hub
Client
Client
Client
Client
Ethernet LAN Segments
Client
Client
END OF MODULE
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
Modem
Server
Hard Disk
DASD
Concentrator
Pc
Mainframe
PC
Front-end
Processor
Term.
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
LANs With Servers/Minicomputers
Router
Switch
Server 1
Hub
WS
WS
Hub
WS
WS
Server 3
WS
WS
WS
Server 4
Server 2
WS
WS
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
END OF MODULE
MODULE
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
Ter.
Mainframe
Ter.
MiniComputer
Front End Processor
Term.
Modem
Server
Gateway
Concentrator
Term.
External
Lines
PC
LAN
PC
Enterprise Systems/Campus
Network
Bus LAN
Mainframe
Systems
Modem
Gateway
Fiber Optic Backbone
(FDDI)
Ring
LAN
WAN
Connection
Star
LAN
END OF MODULE
MODULE
Wide Area Networks
Types
• By virtue of its definition, it is a
decentralized network
Wide Area Network Overview
Terminal or
Microcomputer
LANs
Public Network
(Frame Relay
ATM, X.25)
Campus
Network
Mainframe
Systems
Enterprise
Systems
Network
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
END OF MODULE
END OF MODULE
END OF CHAPTER