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Foundations: Addressing

Foundations: Addressing. Barry Wessler October 1, 2004. The Postal Letter. Variable length Subaddressing Descriptive Field oriented Redundancy (zip code) Limited automation (OCR, ZIP) Global Standard. Circuit Switch. Telex, telephone, X.25 (virtual circuits) Numeric

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Foundations: Addressing

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  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 • R&D 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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