Cse679 prioritized delivery in udp and tcp
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CSE679: Prioritized Delivery in UDP and TCP. Prioritized Delivery in UDP Prioritized Delivery in TCP. Prioritized Delivery for JPEG Data. Prioritized Delivery for MPEG Data. Prioritized Delivery for Audio Data. Playback Jitter. Prioritized Delivery on Transport-layer Protocols. Cyclic-UDP

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Cse679 prioritized delivery in udp and tcp
CSE679: Prioritized Delivery in UDP and TCP

  • Prioritized Delivery in UDP

  • Prioritized Delivery in TCP







Cyclic udp
Cyclic UDP

  • Developed at UC Berkeley

  • Notion of rounds -- data sent in a fixed size time units

  • Retransmit data within the round

  • Move on to next round if data not received within round

  • Apply flow control within the round.


Prioritization in cyclic udp
Prioritization in Cyclic UDP

  • Prioritize packets within round

  • Order higher priority packets in front

  • CUDP improves chances of delivery of higher priority packets -- retransmissions have higher priority

  • NACK - indicate not received packets so far on each packet reception


Congestion control in cyclic udp
Congestion Control in Cyclic UDP

  • Rounds allow timely delivery

  • Uses delay and packet losses for determining available BW

  • Adapt to congestion


Issues in cyclic udp
Issues in Cyclic UDP

  • Assumes all available BW can be used

  • Not clear what happens to competing TCP applications

  • Results indicate multiple CUDP flows share available BW


HPF

  • HPF = Heterogeneous Packet Flows

  • If TCP congestion/flow control is so good, why not retain it?

  • Easy to show that “TCP-friendly”

  • Get rid of reliable/in-order delivery mechanisms that get in the way.


Prioritization in hpf
Prioritization in HPF

  • Allows marking packets high/low priority

  • Provides In-order reliable delivery of high priority packets

  • Allows low priority packets to be delivered when enough BW available

  • If routers support priority, can drop low priority packets ahead of high priority packets


Hpf layers
HPF Layers*

  • Application Framing (AF) -- convert frames into packets, packets into frames

  • Windowing, Reliability, Timing and Flow-control (WRTF) -- window management, flow control, reliability, deadlines

  • Congestion Control (CC) -- congestion response, estimation of RTTs




Hpf vs tcp
HPF vs TCP*

  • Separate the reliable delivery from windowing mechanisms.

  • Multiplicative Decrease/Additive Increase


Conclusion
Conclusion

  • CUDP

    • Allows Timely Delivery and discard of expired packets, prioritization

    • Not clear if more aggressive than TCP

    • Not a multiplicative decrease response

  • HPF

    • UDP-based delivery puts application in charge to do flow control, congestion response etc.

    • Tedious for every application to implement all the basic mechanisms*

    • Separate ALF policies and implementation -HPF does this and follows TCP based congestion response*


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