The Infrastructure Technologies

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The Infrastructure Technologies
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Communication

• All communications require
• Transmitters/Senders and receivers
• Transmission medium
• Rules of communication
• A message

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Computer Data Communication

• Transmitter/Receiver
• Combination of Hardware and software
• Physical Media Types
• Cable
• twisted pair
• coaxial cable
• fiber-optic cable
• Wireless media
• radio
• microwave
• cellular telephone
• satellite
• infrared

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Data Communication Media

• Bandwidth
• Measure of a mediums carrying capacity
• Measured in bits (bps)
• Two categories
• Baseband
• one line, one channel
• most local communication
• Broadband
• one line, simultaneous channels
• DSL, cable

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The Message

• Messages have header and trailer carry
  information for delivering and ensuring the
  integrity of the message
• These are used by application and communication
  protocols
• The electronic form of a message is a signal

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Protocols

• A precise set of rules for communicating
• A communication protocol defines
• message format (header/trailer)
• communication speed
• How the message is encoded (e.g., ASCII, EBCDIC)
• filtering/error correction rules
• An implementation of standard rules for passing
  parameters between adjacent layers

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Signal Transmission
(Fig. 13.14)
Electromagnetic spectrum

• Signals transmitted in the context of a Carrier
  Signal
• Known frequency
• Known amplitude

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Signal Incompatibility

• Inside the computer must have discrete/digital
• Many existing communication lines are
  continuous/analog (especially in the last mile)
• Signal must be converted between digital/discrete
  and analog/continuous through modulation/demodulat
  ion.
• The function of a modem

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As Signal Moves Over Line

• Signal degrades or loses strength.
• Called attenuation
• Signal picks up noise.
• EMI - Electromagmetic interference
• Static
• If not addressed, noise can overwhelm signal
• These limit the distance of some communications

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Digital vs. Analog

• Analog
• contiguous signal
• amplify to boost signal
• noise amplified, too
• noise accumulates
• filter known or predictable noise
• tape hiss

• Digital
• discrete signal
• digits (0, 1)
• sample/retransmit
• boosts signal
• automatically filters most noise
• errors function of sampling rate

Both digital and analog data are transmitted in
the context of a carrier signal.
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Networks

• A network consists of two or more computers
  linked by communication lines.
• Connectivity the ability of a device or
  software to work with other devices and/or
  software over a network connection
• Each connected device is called a node

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Local Area Network - LAN

• Small geographic scope
• Computers in close proximity
• Local communications
• no boosting or filtering
• Workstations

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Wide Area Network - WAN

• Network of networks
• Computers geographically disbursed
• Long-distance communication
• common carrier
• boost and filter signal
• Enterprise networks
• Intranet
• Supply chain integration
• Extranet
• Global networks

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Internetworking Hardware

• Use to connect multiple LANs or WANs
• Have intelligence to filter, route and do
  protocol conversion
• Examples
• Bridges - Similar Networks
• Gateways - Dissimilar networks
• Routers
• Switches

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Bridges and Gateways

• A bridge links similar networks.
• A gateway links dissimilar networks.

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Routers

• accept messages at one of several input ports and
  forward the message to the appropriate output port

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Common Network Topologies
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Clients/Server Networks
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Peer to Peer Networks
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Network Operating Systems

• Client/server architecture LANs
• The system software runs on the server (The
  servers operating system)
• Part of the NOS runs on each workstation
• Software that handles communication between the
  workstation and the NOS
• Agent process on client
• clients link to network
• Examples
• Novell NetWare
• Windows 2000 Server
• Windows NT
• Peer to Peer Networks
• NOS is installed on each attached workstation
• Runs on top of the local operating system

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Message Delivery

• Each computer or terminal is a node
• Messages (signals) are either
• Broadcast to all nodes
• Or move from node to node (point to point)
• Topology or routing determines the route
• Protocols define the precise rules to follow for
  LAN access and message delivery (Many different
  protocol exist)
• Popular LAN Access control methods
• Collision detection
• Token passing

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Network Access Control Methods

• Distributed Access Control
• Token passing
• Circulating electronic token prevents collisions
• Must possess the token to transmit a message
• Random Access Control
• Eliminates collisions
• CSMA/CD (collison detection)
• Listen for quiet line (carrier signal) then
  send message
• Collision occurs with simultaneous messages
• Must wait and resend
• Three major standard protocols for LANs
• Ethernet - (CSMA/CD, Star or Bus)
• Token-Ring - (Token passing, Ring)
• ARCnet - (Token passing, Star or bus)

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Packet Switching

• Most popular type of message delivery
• Break message into packets
• Transmit packets independently
• Multiple messages share line
• Reassemble message at receiving end

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Packet Switching

• Packets can follow different routes to reach
  destination
• Error handling is important
• Packets can arrive out of order
• Individual packets may be lost
• Objectives
• Deliver the message accurately
• Efficient utilization of available bandwidth
• Efficient error recovery

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The Open Systems Interconnect (OSI) Model
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Message Flow
Sending computer
Receiving computer
Each level talks to the equivalent level on the
other node. Transmission errors call for
retransmission of affected packet or packets.
Display and manipulate worksheet
Excel worksheet created
Application
Decrypt and decompress worksheet
Worksheet encrypted and compressed
Presentation
Drop connection on completion
Establish connection
Session
Reassemble packets Verify delivery of entire
message
Divide into packets and create messages
Transport
Reroute if necessary
Determine packet routing
Network
Transmit one packet to next node
Accept packets
Data link
Medium of transmission
Medium of transmission
Physical
Physical Medium
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The TCP/IP Model

• TCP/IP is the standard packet switching protocol
  for the Internet

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TCP/IP Layers

• Application layer
• corresponds to OSI Application and Presentation
  layers
• protocols that directly support application
  programs
• protocols such as telnet, FTP, SMTP, DNS, POP,
  and HTTP
• Transport layer
• corresponds to OSI Session and Transport layers
• TCP (Transmission Control Protocol)
• creates packets and reassembles messages
• guarantees delivery
• Receiving end acknowledges each packet
• Sending end re-sends unacknowledged packets

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TCP/IP Layers (continued)

• Internet layer
• corresponds to OSI Network layer
• IP (Internet Protocol)
• routes and delivers individual packets
• Network access layer
• corresponds to OSI Data-link and Physical layer
• This is where Ethernet, Token ring and other
  network access protocols reside

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TCP/IP Layers (continued)
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IP Address

• IP address
• 32 bit number
• dotted decimal format
• 134.53.40.2
• Standards
• IPV4 current
• IPV6 proposed
• Internet protocol communication requires IP
  address

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Assigning an IP Address

• All computers attached to the Internet must have
  an IP address.
• Static allocation
• IP address established at installation
• linked to specific computers Media Access
  Control (MAC) address (ie. Ethernet address)
• Dynamic allocation
• IP address allocated dynamically at login time
• Must use a protocol such as Dynamic Host
  Configuration Protocol (DHCP)

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Domains
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Domain Name System (DNS)

• Accepts domain name
• Converts to IP address
• Network operating system routine on
• each host
• each server
• each Internet service provider (ISP)
• each network service provider (NSP )

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Caching

• Domain name and IP address cached by all
  participating Domain Name Systems.
• Subsequent references use cached IP address.
• Business student uses cob

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Internet History

• 1960s Started as ARPANET (Advanced Research
  Projects Agency)
• 1986 NSFNET became internet Backbone (56Kbps)
• 1989 NSFNET upgraded to T1 1.44 (Mbps)
• 1991 NSFNET upgradet to T3 45 (Mbps)
• 1991 - First commercial traffic
• 1994 - First Web browser introduced
• 1995 NAPs Replaced NSFNET
• 1995 - Control turned over to independent
  governing bodies

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Internet Terminology

• Interconnect Level
• Any means for bandwidth providers to interconnect
  
• Network Access Points (NAPS)
• MAEs, FIXs and CIX (pseudo NAPs)
• Network Service Providers NSPs (National Backbone
  Providers)
• Replaced NSFNET (old backbone network)
• high-speed lines or series of connections that
  form the major pathways of the internet
• Regional Networks
• connect up to one or more national backbone
  providers
• Local Internet Service Providers (ISPs)
• Consumers and Businesses
• Servers - Contain information and are located on
  independently owned networks

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Internet Architecture
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Internet Access

• Access via local point of presence (POPs)
• by local call
• broadband access into the home
• ISPs provide access (the on-ramp)
• POPs connect up the network hierarchy to an
  interconnect point
• Phone is most common for individuals
• Broadband (Cable and ADSL) are coming fast...and
  competing for market share.