Data Communications and Networking

1

• Data Communications and Networking

2
Source Coding - Text

• Morse Code
• Dot, dash, space
• ASCII
• 7-bit
• Text, symbol, punctuation, formatting
• EBCDIC
• 8-bit
• DLE Data link escape
• Table
• http//www.natural-innovations.com/computing/ascii
  ebcdic.html
• Unicode
• http//www.unicode.org/
• 2-byte
• Cross language
• Common platform

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ASCII Control Code

• ASCII Control Code
• Header and trailer
• SOH Start of header
• STX Start of text
• ETX End of text
• EOT End of transmission
• Handshaking
• ACK Acknowledgment
• NAK Negative ACK
• Printer control
• BEL
• FF

4
Video and Audio Coding

• MPEG
• http//www.mpeg.org/MPEG/index.html
• Audio
• http//en.wikipedia.org/wiki/MP3
• Video teleconferencing
• MPEG-4, 7, 21

5
Line Coding

• Bandwidth Limited Digital Signaling
• DC
• Timing recovery
• Polarity
• Unipolar
• Polar
• Bipolar
• http//www.electronics.dit.ie/staff/amoloney/dt021
  _4/lecture-9.pdf

HDB3
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Line Coding

• Unipolar
• H, 0L DC
• Polar
• H, -L No DC
• NRZ
• NRZ-Level (H or L)
• NRZ-Invert (transition when next bit is H)
• Bandwidth efficient
• Difficult to synchronize for long zero
• RZ (H and zero or L and zero)
• RZ-NRZ converter
• http//www.iterrac.com/product/nrz_converters.html

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Line Coding

• Biphase
• Manchester (H to L or L to H in the middle of
  clock interval)
• Differential Manchester (transition in the
  middle, plus transition at beginning for zero)
• Bipolar
• Alternate Mark Inversion (alternate between and
  for 1, zero for 0)
• Waveforms
• http//web.uct.ac.za/depts/staff/rebejide/New20Fo
  lder/eee358s-508PCM.ppt
• Hardware Circuits
• http//www.tek.com/Measurement/fundamentals/scopes
  /literature/linecode.pdf

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More Line Coding

• 4B5B
• 8B6T
• 4B2Q
• MLT3
• PAM5x5
• 4D-PAM5

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Channel Coding

• Reliability via Redundancy
• Error Detection
• Parity check
• Single bit
• Even or odd

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Channel Coding

• Cyclic redundancy check
• Data 00101100010101110100011
• Generator
• Polynomial
• 100101
• Modulo-2 division
• Remainder 00010
• ACK and ARQ
• (Request to resend)

100101 00101100010101110100011
100101 -------------
00100101
100101 ----------
0000000101110
100101 ----------
00101110 100101
---------- 00101100
100101 ----------
00100111 100101
----------
00010
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Channel Coding

• CRC-16 hardware implementation

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Channel Coding

• Forward Error Correction
• Block coding (n,k)
• Convolution coding

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Hamming Code

• Example
• Strategy
• Maximize difference among valid codes

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Hamming Code

• Input
• 16 possible 4-bit input blocks
• Translation (Matrix Multiplication or Parity)
• Output
• 7-bit output block, 128 patterns
• Convert Back to Data and Parity Bits
• Error Handling
• 1 detect and correct
• 2 detect
• ?3 undetected
• BCH (Bose-Chaudhuri-Hocquenhem) codes

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Hamming Code

• Rule
• d p 1 lt 2p
• Systematic approach
• (7,4) http//www.ee.unb.ca/tervo/ee4253/hamming.ht
  m
• (12,8) http//www.cs.fiu.edu/downeyt/cop3402/hamm
  ing.html
• Efficiency

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Error and Coding

• Burst or Distributed Error
• Interleaving redundancy bits with data
• Latency
• Reed Solomon Code
• History
• http//www.cs.utk.edu/shuford/terminal/reed_solom
  on_codes.html
• CD data processing
• http//web.usna.navy.mil/wdj/reed-sol.htm

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Convolution Code

• Operates Serially on Incoming Bits
• (n,k,K)
• n number of output bits
• k number of input bits
• K constraint length, number of input bits to
  determine output
• Viterbi Decoding
• Tutorial
• http//home.netcom.com/chip.f/viterbi/tutorial.ht
  ml

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Data Encryption

• Encryption
• Input Data, key
• Engine Algorithm
• Output Scrambled data
• Decryption
• With key
• Without key
• Key
• Secret
• Public/Private

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RSA Algorithm

• Pick P, Q
• Two large prime numbers 53, 61
• Pick E
• 1ltEltPQ
• Relative prime to (P-1)(Q-1) 17
• Publicize E and PQ
• Compute Private Key, D
• DE-1 evenly divisible by (P-1)(Q-1)
• Encryption
• CTE mod PQ
• Decryption
• T CD mod PQ
• http//mathworld.wolfram.com/RSAEncryption.html

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Quantum Encryption

• Key Generation and Distribution
• Single Photon Events
• Eavesdropping sensitive
• http//www.aip.org/pt/vol-53/iss-11/p22.html
• http//www.osa-opn.org/abstract.cfm?URIOPN-13-7-2
  6

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Synchronization

• Asynchronous
• Start bit, data, parity, stop bit
• Synchronous
• Frame

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Computer Peripherals

• Serial
• 9 pin, 25 pin
• Hardware handshaking
• Xon, Xoff
• Parallel or Centronix
• IEEE488 or HPIB
• Firewire
• USB

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Serial Port
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UART

• Signaling
• Block Diagram
• Application
• http//www.khwarzimic.org/interfacing/SERIAL_PORT
  .pps

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Parallel Port
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Parallel Peripheral Interface

• IEEE1284 Specifications
• http//www.longrange.net/ParallelPort/1284d12.pdf
  
• Parallel Port Programming and Projects
• http//www.epanorama.net/circuits/parallel_output
  .html
• http//www.logix4u.net/parallelport1.htm

27
IEEE488

• What is IEEE488
• http//www.hit.bme.hu/people/papay/edu/GPIB/tutor.
  htm

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Firewire and USB

• IEEE1394
• 100M, 200M, 400Mbit/sec
• Peer to peer
• lt 4.5m
• 63 devices
• DC 1.25A
• Digital video
• USB
• 1.5M, 12M, 480Mbit/sec
• Controller hub
• lt 5m
• 127 devices
• DC 500 mA

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Firewire and USB Chips

• Interface Chips
• http//www.lvr.com/usbchips.htm
• Chipset
• Intel
• Nvidia
• ATI
• Via
• Sis

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Networking

• OSI Model
• Networks
• LAN, MAN, WAN
• Topology
• Hardware
• Ethernet
• Internet
• VoIP

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OSI Model
32
5-Layer Internet Model
Linux TCP/IP Network Administration
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Network Topologies

• Mesh
• Star
• Bus
• Ring
• Tree

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Considerations

• Traffic Flow
• Latency
• Collision
• Reliability
• Node failure
• Scalability
• Number
• Length
• Infrastructure and Cost

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Hardware

• Network Interface Card
• Chipset
• Connector
• RJ45, DB9-AUI, BNC
• Cable
• Twisted wire pair, coax, fiber, etc.
• Hub or Repeater
• Data forwarding or regeneration (physical layer)
• Bridge
• Network segmentation (data link layer)
• Switch
• Direct connection (data link layer)
• Router
• Across network packet delivery (network layer)
• Network address translation
• Firewall
• Gateway
• Data repackaging, protocol change (transport and
  session)

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Ethernet

• Standards
• IEEE802.3
• Specifications
• 10 Mb/s, 100 Mb/s, 1000 Mb/sec
• Data Frame
• Preamble (7-bytes)
• Start Frame Delimiter (1-byte)
• Destination MAC Address (6-bytes)
• Source MAC Address (6-bytes)
• Length / Type (2-bytes)
• Data (0-n bytes)
• Padding (0-p bytes)
• Frame Check Sequence (4-bytes)
• Media Access
• MAC Address
• Peer to Peer
• CSMA/CD
• References
• http//www.cisco.com/univercd/cc/td/doc/cisintwk/i
  to_doc/ethernet.pdf

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Ethernet Signaling

• 100Base-TX
• Gb

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Reading Materials

• Introduction to TCP/IP
• http//www.yale.edu/pclt/COMM/TCPIP.HTM
• Networking
• http//www.cisco.com/univercd/cc/td/doc/cisintwk/i
  to_doc/