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Design Philosophy of the DARPA Internet Protocols

Design Philosophy of the DARPA Internet Protocols. CSCI 634, Fall 2010. Fundamental goals (top-level). High utilization by multiplex Packet switching Inter-connect heterogeneous networks Gateway: store and forward packets. These two determine the structure of Internet. Second level goals.

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Design Philosophy of the DARPA Internet Protocols

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  1. Design Philosophy of the DARPA Internet Protocols CSCI 634, Fall 2010

  2. Fundamental goals (top-level) • High utilization by multiplex • Packet switching • Inter-connect heterogeneous networks • Gateway: store and forward packets These two determine the structure of Internet

  3. Second level goals • Fault-tolerance (V) • Support multiple type of services (X) • Accommodate a variety of networks (V) • Distributed resource management (V) • Cost-effective (V) • Easy host attachment (V)) • Accountability (X)

  4. Fate-sharing • Only end-point maintains the states • We lose the state information associated with the end-host, only when the end-host itself is dead • Gateways are stateless • Tolerate any number of intermediate failures • Much easy to engineer than replication

  5. Type of service • TCP supports reliable sequenced data delivery • Virtual circuit • UDP provides the basic datagram service • Multiple services could be constructed out of basic datagram building block • Not as easy as expected • Lack of flexibility

  6. Varieties of networks • X.25 networks • Ethernet, token-ring • Satellite nets • Wireless networks Key to flexibility: making a minimum assumptions about the function that the net will provide

  7. Architecture & Implementation • Flexibility: various realization • Challenge: how to relate realization to the proposed service ? • Performance! • Performance!! • Still Performance!!! That is why we need networking research!

  8. Internet Architecture: Datagram • No individual connection state is maintained at routers • Datagram is a basic building block • Datagram represents the minimum network service assumption

  9. TCP design decision • Flow control and acknowledgement are byte-based, not packet-based • Insert control information into sequence space (X) • Broken into smaller packets (X) • Small packets can be gathered into one larger packet • More accurate estimation of throughput • No EOL (End-Of-Letter) flag

  10. Summary (many great points) • More attention to • Accounting • Resource management • Operations of different ASes (BGP) • Better building block than datagram • Flow-based • Soft-state

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