Foundations:%20Addressing - PowerPoint PPT Presentation

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Foundations:%20Addressing

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Limited Huffman coding (country codes and area codes in some countries) ... Part physical address to the final recipient or functional area. Addressing was local ... – PowerPoint PPT presentation

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Title: Foundations:%20Addressing


1
Foundations Addressing
  • Barry Wessler
  • October 1, 2004

2
The Postal Letter
  • Variable length
  • Subaddressing
  • Descriptive
  • Field oriented
  • Redundancy (zip code)
  • Limited automation (OCR, ZIP)
  • Global Standard

3
Circuit Switch
  • Telex, telephone, X.25 (virtual circuits)
  • Numeric
  • Variable length (but fixed maximum)
  • Limited Huffman coding (country codes and area
    codes in some countries)
  • Historically geo-coded numbering but some
    breakdown today due to mobile services

4
Message Switching
  • Telex store-and-forward
  • Generally hybrid addressing
  • Part numeric to a distribution center
  • Part physical address to the final recipient or
    functional area
  • Addressing was local

5
Packet Services
  • Three original ARPANet application models
  • Person-to-person (RWT)
  • Computer-to-computer (LGR)
  • Person-to-computer (BDW)

6
Basic Justification LGR Analysis
Unit cost
Transmission
Computing
Time
7
Original Scale
  • 30 to 50 nodes planned
  • 50 Kbs lines between nodes
  • Less than 100 bytes average packet size
  • ARPA IPT contractors and selected defense
    establishments
  • RD money used not implementation or operation
    money

8
ARPANet Addressing
  • Specified in BBN 1822 interface document
  • Fixed length (6 bits) node addressing
  • Subaddressing (2 bits)
  • Total of 256 addressable points
  • Later changed to 16 bit node addressing and 8 bit
    subaddressing (1976)

9
Early ARPANet Map
10
Later Map
11
Later Map
12
System Complexity
Complexity
Time
13
Addressing for Internet 0
  • Always use existing protocols if rational and
    possible
  • If not, try to predict end point complexity and
    plateaus and design accordingly
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