Network Designs and Cabling

1
Network Designs and Cabling

• Organizational Communications and Technologies
• Prithvi N. Rao
• H. John Heinz III School of Public Policy and
  Management
• Carnegie Mellon University

2
Readings

• Traditional Wide Area Networks(Stallings and van
  Slyke) Chapter 7
• Local Area Networks (Stallings and van Slyke)
  Chapter 9

3
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

4
Objectives

• Discuss the strengths of peer-to-peer network
  systems
• Describe two different media plant specifications

5
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

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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

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Stand-Alone Computers
Printer
Sales Data
Billing Data
Customer Service Data
Planning
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Token Ring Cabling

• Result was localized processing or distributed
  processing
• Has both advantages and disadvantages over
  centralized processing

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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

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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

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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

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Local Area Networks (LAN)

• LAN provides physical connection between
  independent computing devices
• LAN provides logical connection including
• Handshaking
• Flow control
• Error detection

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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

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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
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Token Ring
File Server
Node
Shared printer
Node
Node
Print Server
Node
Node
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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

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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

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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

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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

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Peer-to-Peer
Shared printer
Shared disk storage
Host
Host
Peer Host
Host
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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
  network-based distributed applications

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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

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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

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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

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NIC Configuration Items

• I/O address
• IRQ address
• DMA channel
• ROM and RAM addressing

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Configuration Issues Problems and Solutions

• Problem right after installation of NIC card
• NIC card failure
• IRQ conflict
• Solution is to reconfigure the IRQ to a different
  value
• 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

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Configuration Issues Problems and Solutions

• Problem
• Node address is not unique
• Solution
• 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

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Configuration Issues Problems and Solutions

• Solution
• Adjust drivers to use alternative memory (higher)
• Problem
• 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

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Configuration IssuesProblems and Solutions

• Problem
• Hangs up when accessing the server
• Bad driver or speed related problem
• Solution
• Bad driver requires replacement from vendor
  software CD
• Place driver on a different place on disk
• Problem
• PC is running too fast for NIC

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Configuration Issues Problems and Solutions

• Solution
• Upgrade NIC
• Slow down PC by inserting wait-states inside CMOS
  setup
• Problem
• Invalid path, No xxxx file found means that some
  configuration files cannot be found
• Solution
• Set up NOS software to point to the files

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Media

• Two types of media used in networking systems
• Bounded
• unbounded
• Bounded
• Signal is contained within bounds of media in the
  cable
• Unbounded
• Signal travels in the absence of a cable outside
  bounds of physical media

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Bounded Media

• Coaxial cable
• Twisted pair cable
• Fiber optic cable

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Unbounded Media

• Satellite transmission
• Infrared
• Radio Frequency
• Microwave
• Laser

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Twisted Pair

• Two kinds
• 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

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Twisted Pair

• Various grades of cable
• Level 1 used for telephone connections
• Level 5 used to support high speed LAN

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Fiber Optic Cable Profile

• Transmits light rather than electrical signals
• FDDI is one example (Fiber Distributed Data
  Interface)
• Token passing LAN protocol
• Popular for long distance carriers
• Little need to regenerate signal midway
• Advantage over traditional cabling that have much
  shorter distances of propagation before signal
  must be regenerated
• Large bandwidth so large movements of data
  possible

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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)
38
Coaxial Cable

• Two kinds
• Thick
• Thin
• Generally used to construct
• 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)
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Cable Plant Specifications

• Vendors provide specifications for layout of
  cable plant
• IBM cable plant
• ATT premises distribution scheme
• Both use a HUB and SPOKE approach
• Hubs are placed in wiring closets
• Spokes branch out to each workstation
• Hubs are connected by a backbone

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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?
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Radio Frequency (RF) LAN

• Gaining popularity
• 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

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Radio Frequency (RF) LAN
Radio frequency Communications Controller
Workstations with RF NICs
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Summary

• LANs follow two design principles
• Clients or servers
• Equal peers
• Services include
• 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

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Summary

• Two media types available
• Bounded (twisted pair, coaxial cable, fiber optic
  cable)
• Unbounded (satellite, microwave, radio frequency)