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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. Prioritized Delivery for JPEG Data. Prioritized Delivery for MPEG Data. Prioritized Delivery for Audio Data . Playback Jitter. Prioritized Delivery on Transport-layer Protocols.

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CSE679: Prioritized Delivery in UDP and TCP

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  1. CSE679: Prioritized Delivery in UDP and TCP • Prioritized Delivery in UDP • Prioritized Delivery in TCP

  2. Prioritized Delivery for JPEG Data

  3. Prioritized Delivery for MPEG Data

  4. Prioritized Delivery for Audio Data

  5. Playback Jitter

  6. Prioritized Delivery on Transport-layer Protocols • Cyclic-UDP • HPF

  7. 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.

  8. 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

  9. Congestion Control in Cyclic UDP • Rounds allow timely delivery • Uses delay and packet losses for determining available BW • Adapt to congestion

  10. 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

  11. 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.

  12. 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

  13. 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

  14. HPF Architecture*

  15. HPF*

  16. HPF vs TCP* • Separate the reliable delivery from windowing mechanisms. • Multiplicative Decrease/Additive Increase

  17. 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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