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Foundations: Addressing

Explore the transition from postal letter systems to Internet addressing methods, including variable length addressing, ARPANet models, and global standards for communication circuits.

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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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