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A FreeBSD-based prototype of a Time-Driven Priority router

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Politecnico di Torino Istituto Superiore Mario Boella. A FreeBSD-based prototype of a Time-Driven Priority router. Mario Baldi Guido Marchetto. Goals. First implementation of TDP Until now analytical studies and software simulations only Identification of possible criticalities

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Presentation Transcript
slide1

Politecnico di Torino

Istituto Superiore Mario Boella

A FreeBSD-based prototype of a Time-Driven Priority router

Mario Baldi

Guido Marchetto

slide2

Goals

  • First implementation of TDP
    • Until now analytical studies and software simulations only
    • Identification of possible criticalities
  • Visually show TDP benefits through multimedia demonstration
    • Video quality with TDP vs asynchronous packet switching
slide3

Network prototype topology

TDP network

router

host

slide4

Router architecture

  • PC based
  • FreeBSD operating system
  • Four components:
    • TDP input classifier
    • TDP output buffers (ALTQ extension)
    • TDP scheduler
    • Asynchronous input shaper(Dummynet extension)
slide5

Common Time Reference (CTR)

  • Adopted card: Symmetricom
    • Periodic interrupt over the PCI bus
    • Programmable interrupt frequency
  • Each interrupt represents the beginning
  • of a new TF
slide6

Implementation issues

  • Interfaces are not served at the same time
  • Interrupts are served with latency
  • Both servicing times are variable
slide7

Consequences

  • Transmissions do not start as soon asthe TF begins
    • Violation of nominal time frame boundaries
  • Transmissions start with a variable delay
  • Potential bandwidth waste
slide8

Facts

  • Latency equivalent to longer links
    • Interrupt and interface service latencyis low
  • Latency variation is absorbed by “delaying” forwarding time-frame
    • Interrupt and interface service latency has low variability
  • “EXTRA” CROSSING DELAY IN THE NODE
  • “EXTRA” BUFFERING IN ORDER TO HANDLE THIS DELAY
slide9

Conclusions

  • Contribution
    • Proof of concept:
      • Algorithm and system semplicity(~1000 LOC)
      • PC architecture can support TDP
  • Future work
    • Performance evaluation
    • Realization of the network testbed and demonstration
slide10

Thank you.

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