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Network Designs and Cabling
Organizational Communications and
Technologies
Prithvi N. Rao
H. John Heinz III School of Public
Policy and Management
Carnegie Mellon University
Readings
Traditional Wide Area
Networks(Stallings and van Slyke)
Chapter 7
Local Area Networks (Stallings and van
Slyke) Chapter 9
Objectives

Identify the differences of centralized vs distributed
computing

Describe the three basic functions of any network

List two network design principles

Discuss the strengths of client/server network
systems
Objectives


Discuss the strengths of peer-to-peer network
systems
Describe two different media plant specifications
Token Ring Cabling


Explosion of personal computers has changed the
way organizations process information
De-centralization created a number of problems for
MIS managers



Sharing of information more difficult
Difficult to access corporate application files
Difficult to access common peripheral devices
Token Ring Cabling

Centralized mainframes





One central processing device
Single file system
Facility to control peripherals
Single communications mechanism
PC networks




Many processing units
Many file systems
Many peripherals
Many communications mecahism
Stand-Alone Computers
Printer
Sales Data
Billing Data
Customer
Service
Data
Planning
Token Ring Cabling


Result was localized processing or distributed
processing
Has both advantages and disadvantages over
centralized processing
Advantages of Distributed
Processing


Networks can be grown incrementally by adding
additional workstations as needed
Localized processing allows some users to run
computationally intensive applications without
affecting the performance of other users

PC technology is widely known and well accepted

Vast library of application software for PC systems
Disadvantages of Distributed
Processing



Lack of central file storage systems to store
commonly accessible data and application files
Lack of communication facility to support sharing of
peripherals
Operating a PC may require more skill

Employee skill level must increase
Local Area Networks (LAN)



LANs developed to restore lost functionality of
centralized mainframes
Allowed connection of independent desktop
computers together
LAN geographical range is small with reasonably high
data rates of transfer
Local Area Networks (LAN)


LAN provides physical connection between
independent computing devices
LAN provides logical connection including



Handshaking
Flow control
Error detection
Local Area Networks (LAN)

LANs offer benefits of sharing application data and
peripherals among users



Greatly reduced cost
Incrementally expand network
Three basic functions of any network



File transfer
Remote program execution
Virtual terminal services
Local Area Networks (LAN)
All other network applications (peripheral sharing)
can be accomplished using one of these three basic
functions.
Example:
Shared printing is a file transfer operation to another
computer where it is printed
Token Ring
File Server
Shared printer
Node
Print
Server
Node
Node
Node
Node
LAN Design Principles

Client – Server LANs define one computer as the
master station or LAN Server and other computers
are LAN clients


Clients depend on server for services
Central server contains



Central file system
Communication facility or NOS software
Centralized authority to manage network
LAN Strengths


Central file system
Communication can be efficiently managed by central
server

Server can act to police the network traffic of clients

Client communication software is simple
LAN Weaknesses

Single point of failure: no server implies no network

All communication must involve server


Even local conversation between clients
Network operating system may be overly complex
Example of NOS is Novell Netware
Peer-to-Peer

Peer-to-peer networks treat all computers on network
as equal peers



All computers responsible for communication requirements
of LAN
All computers are masters and manage
communication amongst workstations
No single server to manage LAN
Peer-to-Peer
Shared printer
Peer Host
Host
Shared disk
storage
Host
Host
Peer-to-Peer Strengths



No single point of failure for communication on the
network
More flexibility for storing distributed data and
sharing remote peripherals
Availability of more application programming
interfaces that facilitate development of networkbased distributed applications
Peer-to-Peer Weaknesses



Host software must be more self-sufficient requiring
it to be more complex than client software
Absence of central monitor to manage network
communication
Lack of authority mechanism to resolve contention
issues that may arise during operation
TCP/IP are an example of peer-to-peer networks
Interface Requirements



Each computer must contain a Network Interface
Card (NIC) that physically attaches to the internal
bus of the computer
NICs come in different types, speeds and price
ranges
NICs handle the actual sending and receiving of data
between computers that are communicating
NIC Functions

Physically attaching the computer to the network

Framing the data for transmission as digital signals


Decoding received signals and converting it back to
data
Error detection (usually with CRC) and retransmission
NIC Configuration Items

I/O address

IRQ address

DMA channel

ROM and RAM addressing
Configuration Issues:
Problems and Solutions

Problem right after installation of NIC card



Solution is to reconfigure the IRQ to a different value



NIC card failure
IRQ conflict
Software as well as hardware may need to be reconfigured
Problem is lobe media failure
Solution is to check cable and connectors and replace
parts
Configuration Issues:
Problems and Solutions

Problem


Solution


Node address is not unique
Another NIC card on the LAN has the same address as your
card. Replace the card for a different one from your vendor
Problem

Insufficient memory for NOS or application program to run
Configuration Issues:
Problems and Solutions

Solution


Problem



Adjust drivers to use alternative memory (higher)
DMA failure
Some NIC cards do not support DMA
Solution


Reconfigure NIC to alternative DMA channel
Disable DMA or disable memory cache addressing on NIC
Configuration Issues:Problems
and Solutions

Problem



Solution



Hang’s up when accessing the server
Bad driver or speed related problem
Bad driver requires replacement from vendor software CD
Place driver on a different place on disk
Problem

PC is running too fast for NIC
Configuration Issues:
Problems and Solutions

Solution



Problem


Upgrade NIC
Slow down PC by inserting wait-states inside CMOS setup
Invalid path, No xxxx file found means that some
configuration files cannot be found
Solution

Set up NOS software to point to the files
Media

Two types of media used in networking systems


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Bounded

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Bounded
unbounded
Signal is contained within bounds of media in the cable
Unbounded

Signal travels in the absence of a cable outside bounds of
physical media
Bounded Media

Coaxial cable

Twisted pair cable

Fiber optic cable
Unbounded Media

Satellite transmission

Infrared

Radio Frequency

Microwave

Laser
Twisted Pair

Two kinds

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Shielded (STP)
Unshielded (UTP)
Twisted pair used to construct token ring LANs and
10Base-t (T for twisted pair)




Connects terminals (STP)
Voice communication and wiring telephone networks
Least expensive and does not require special skills to instal
Already exists mostly
Twisted Pair

Various grades of cable


Level 1 used for telephone connections
Level 5 used to support high speed LAN
Fiber Optic Cable Profile

Transmits light rather than electrical signals

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
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Little need to regenerate signal midway

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FDDI is one example (Fiber Distributed Data Interface)
Token passing LAN protocol
Popular for long distance carriers
Advantage over traditional cabling that have much shorter
distances of propagation before signal must be regenerated
Large bandwidth so large movements of data
possible
Fiber Optic Cable Profile

Advantages over traditional cabling


Immune from crosstalk
Immune from noise as a result of electro-magnetic
interference (EMI) or radio frequency interference (RFI)
Fiber is typically used as a backbone media connecting LANs together since
the cost of the media and special skills to install it may prohibit its use to
each workstation (for now)
Coaxial Cable

Two kinds

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
Thick
Thin
Generally used to construct


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BUS Ethernet LAN
ARCNET LAN
Broadband LAN
Coaxial cable can extend long distances and has a high level of immunity to
electrical interference (thicknet more so than thinnet cable)
Cable Plant Specifications

Vendors provide specifications for layout of cable
plant



IBM cable plant
AT&T premises distribution scheme
Both use a HUB and SPOKE approach

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Hubs are placed in wiring closets
Spokes branch out to each workstation
Hubs are connected by a backbone
Design Considerations



Important to lay out wiring plan, install and test
Can use a simulator to assist in prediction of behavior
of network
Existing cable layouts must be carefully examined to
satisfy requirements due to cost of replacement


Cost of materials is usually less than 10% of total
Labor which can be 90% of total
Might as well install expensive cable?
Radio Frequency (RF) LAN

Gaining popularity

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
No need for expensive cable plant installation and
maintenance
Easier to modify, expand and dismantled
RF technology uses different spectrum to microwave




Cannot travel as far as microwave
Particularly useful for LAN
Wireless devices are getting more popular
Unanswered issues regarding assignment of spectrum
ranges, security and reliability of transmission
Radio Frequency (RF) LAN
Radio frequency
Communications
Controller
Workstations with RF NICs
Summary

LANs follow two design principles



Services include




Clients or servers
Equal peers
File management
Print and communications services
Peer-to-peer can act as servers without being configured as
such
Media can be greatest expense and source of failure
Summary

Two media types available


Bounded (twisted pair, coaxial cable, fiber optic cable)
Unbounded (satellite, microwave, radio frequency)