Introduction to Networking

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Introduction to Networking

• James R. Coakley, PhD

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Outline

• 5-layer Network Model
• A theoretical framework for our day-to-day
  interactions on the Internet
• Protocol stack
• Network Design and Topology

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Theoretical Framework 5-layer network model

• Application Layer (Layer-5)
• Transport Layer
• Network Layer

• Data Link Layer
• Physical Layer (Layer-1)

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Five-Layer Network ModelMajor Functions

• Application Layer (top)
• User interface with application software
• HTTP (Hyper Text Transfer Protocol)
• Example of an application layer address
  www.bus.oregonstate.edu

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Five-Layer Network ModelMajor Functions

• Transport Layer
• Packetizing
• Breaking large messages into smaller packets at
  source
• Reassembling packets at final destination
• Creates/appends TCP (Transmission Control
  Protocol) header
• Packet
• Source/Destination Port ID
• 80 (Web)
• 25 (E-mail)

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Five-Layer Network ModelMajor Functions contd

• Network Layer Addressing and Routing.
• Internet Protocol prepares IP header.
• Contents of IP header include Source/Destination
  IP Address and Routing Information
• Example of an IP address 128.192.64.224
• Addressing
• DHCP Server (Dynamic Host Control Protocol
  Server)
• Assigns IP addresses to client machines
  requesting an IP address
• DNS Server (Domain Name Service Server)
• Similar to directory assistance used for
  finding destination IP addresses.
• Routing
• Routing tables Routers (Tracert) Routing
  Protocols

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Five-Layer Network ModelMajor Functions contd

• Data Link Layer
• Media Access Control (Handling message
  collisions)
• Error Detection/Error Correction
• Message Delineation (Identifying beginning and
  ending of packets since all computer
  transmissions go out as 0s and 1s over the
  physical layer)
• DL layer appends a DL header and DL Trailer

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Data Link LayerData Direction Methods

• Methods to direct data between locations
• Circuit switching
• Packet switching
• Frame relay
• Faster, less expensive
• Does not perform error correction

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Data Link LayerData Direction Methods (contd)

• ISDN
• Worldwide digital protocol using existing
  twisted-pair telephone lines
• Transmit voice, video and data up to 1.5 Mbps
• Asynchronous Transfer Mode (ATM)
• Seamlessly and dynamically switch voice, data and
  video
• Speeds range from 155 Mbps to 2.5 Gbps
• Uses uniform cells (53 by 8) eliminating need for
  protocol conversion

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Data Link LayerProtocols

• Ethernet Bus with CSMA/CD
• Carrier Sense Multiple Access/Collision Detection
• Fast Ethernet (100 mbps)
• Gigabit Ethernet
• Token Ring
• FDDI
• Fiber Distributed Data Interface
• Token Ring on fiber

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FDDI
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FDDI (Continued)
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Data Link LayerInternetworking Devices

• Hubs Multiplexers
• Switches Routers
• DSL/Cable Modems

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Internetworking Devices

• Connect Networks together
• Gateway (AL)
• Translate protocols
• Router (NL)
• Routes messages between same protocol
• Bridge (DL)
• Same protocol
• Hubs (PL)
• Broadcast
• Switch (all)
• Point-to-point
• Multiplexers

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Layer 1 - Physical Layer

• Wired Media/Wireless Media Examples
• Twisted pair Coaxial Fiber Optic Cables
• Microwave Satellites and wireless (cell phones)

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Physical LayerBackground on Telecommunications

• Modem
• Modulate demodulate
• Multiplexing

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Physical LayerTelecommunications Media

• Criteria that determine ability to transmit data
• Frequency cycles per second (baud). Hertz is
  one cycle per second. measure of speed. (assume
  send one bit per cycle)
• Bandwidth difference between highest and lowest
  frequencies which can be transmitted. measure of
  capacity (pulse-code modulation)
• Attenuation signal strength weakens as it
  travels over distance.
• Interference EMI (electromagnetic) and RFI
  (radio frequency)

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Physical LayerTelecommunications Media (contd)

• Twisted Pair standard telephone lines
• High availability
• Lower speeds, poor security
• High-speed data lines
• T1 (1.54 mbps)
• T3 (45 mbps)
• Cable coaxial cable
• Less interference, higher bandwidth
• Higher cost, low security

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Physical LayerTelecommunications Media (contd)

• Microwave
• Towers spaced 30 miles apart (line of sight)
• Easier than trenching wires into dirt
• Susceptible to interference
• Satellite
• Eliminates line-of-sight issue
• Propagation delay
• HF (high frequency)/RF (radio frequency)
• Use for short range (within warehouse)

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Physical Layer Broadband Communications

• High-speed connections
• Distinguish upstream and downstream
• 56K modem has upstream of 31.2 and downstream of
  56
• For Internet use, need higher downstream rates
• Three options
• DSL (telephone lines)
• Cable Modem (cable)
• Satellite (microwave)

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Cable Modem

• Send and receive data over the coaxial cable used
  in cable television system

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Advantages of Cable Modem

• Speed
• The fastest home Internet connection speeds
  possible
• Up to 30 mbps (megabits per second)
• Ease of setup
• As simple as installing regular cable
• Call local provider for setup
• Low cost
• Add-on to Cable

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Disadvantage

• Must have cable
• Speed dependent on number of users
• High installation fee

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DSL - Digital Subscriber Lines

• Brings high bandwidth information to homes or
  small businesses over ordinary telephone lines
• Can use telephone and PC on the same line and at
  the same time

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Advantages

• Speed --
• Individual connections will provide from 512 Kbps
  to 1.544 Mbps downstream and about 128 Kbps
  upstream
• These are not shared (as in cable modem)
• Carries voice conversations and data connections
  at the same time

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Disadvantages

• Restricted availability
• Must be within 3 miles of switching station
• Attenuation of signal
• Higher cost for higher speeds

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Satellite Technologies

• A device used to transmit and receive signals
  from a satellite transponder

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How does it work?
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Advantages

• Speed
• 400 Kbps downstream, upstream through modem
• Internet and TV on one dish
• Can be used in remote areas
• Easy to install

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Disadvantages

• Slower than DSL or cable modem
• Higher cost

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Physical Layer Wireless Wide Area Network

• Multiple competing technologies
• CDMA - 1xRTT code-division multiple access
• Verison and Sprint
• 70 kbps data rate
• Mostly US, Canada, Korea
• GSM-GPRS global system for mobile communication
• T-Mobile and ATT
• 40 kbps data rate
• Available world-wide
• T-Mobile has roaming agreements in Europe
• CDPD Cellular Digital Packet Data
• Based on IP (packet switched) and conforms to ISO
  standards
• Up to 19.2 kbps data rate

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Physical Layer Wireless Local Area Network

• Closer to having standards for WLAN
• Wi-Fi 802.11 families
• (b) wireless ethernet.
• 2.5 Ghz band
• 11 mbps (5 mbps data rate)
• (a) proposed standard. 54 mbps on 5 Gig radio
  band
• (g) works in b band, but delivers 54 mbps speed
  (20 mbps data rate)
• Bluetooth
• Connect devices to PC within 30 feet
• 710 kbps
• IR devices
• 6 feet, 4 mbps
• WiMax

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Application LayerWireless Application Protocol

• WAP
• Format web pages for display on wireless devices
• Move to fully synchronized PDAs
• Providence Health Care

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Local Area Network

• Connects PCs together
• Peer-to-peer
• Server-based
• File server
• Distance restrictions
• Between 1000 and 5000 feet
• Why?

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Wide Area Network

• What is it?
• How connect?
• Leased Lines
• Satellite
• Other options
• VAN
• Private, data-only network managed by third party
• Virtual Private Network
• Run WAN over internet (tunneling)

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What is the Internet?

• Global network of LANs
• How did Internet evolve?
• Originated in 1969, restricted to government,
  research and education (Arpanet)
• WWW released in 1992
• In 1993
• Ban on commercial use lifted
• Mosaic released
• Growth (different data depending on source)
• 3 million in 94
• 40 million in 97
• 100 million in 98

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What are the underlying technologies?

• Packet Switching
• .X25 standard uses packets of 128 bytes
• Each packet travels independently through network
• Protocols TCP/IP
• Internet Protocol destination address
• Each computer has its own IP address
• Domain name system (DNS)
• Transmission Control Protocol breaks
  information into data packets

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Backbone
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What is WWW?

• Application that uses the internet
• Set a standards for storing, retrieving,
  formatting and displaying information via
  client/server architecture
• HTML standard language
• Connection
• Uniform Resource Locator (URL)
• Hypertext transport protocol (http)
  communication protocol to transfer pages
• ftp File Transfer Protocol