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

• 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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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
• 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 Server 2000,2003, NT Server
• 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 (collision 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 TCP/IP Model
TCP/IP is the standard packet switching protocol
for the Internet
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TCP/IP Layers

• Application layer
• protocols that directly support application
  programs
• protocols such as telnet, FTP, SMTP, DNS, POP,
  and HTTP
• Transport layer
• 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
• IP (Internet Protocol)
• routes and delivers individual packets
• Network access layer
• This is where Ethernet, Token ring and other
  network access protocols reside

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IP Address

• IP address
• 32 bit number
• dotted decimal format
• 134.53.40.2
• Standards
• IPv4 current IPv4 addresses are 32 bits
• supports 232 (about 4.3 billion) addresses
• IPv6 proposed a 64-bit (sub-)network prefix
  and a 64-bit host part
• supports 2128 addresses
• 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 (i.e. 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 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.