CSE 679 Prioritized Delivery in UDP and TCP

CSE 679: Prioritized Delivery in UDP and TCP r Prioritized Delivery in UDP r 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 r Cyclic-UDP r HPF

Cyclic UDP r Developed at UC Berkeley r Notion of rounds -- data sent in a fixed size time units r Retransmit data within the round r Move on to next round if data not received within round r Apply flow control within the round.

Prioritization in Cyclic UDP r Prioritize packets within round r Order higher priority packets in front r CUDP improves chances of delivery of higher priority packets -- retransmissions have higher priority r NACK - indicate not received packets so far on each packet reception

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

Issues in Cyclic UDP r Assumes all available BW can be used r Not clear what happens to competing TCP applications r Results indicate multiple CUDP flows share available BW

HPF r HPF = Heterogeneous Packet Flows r If TCP congestion/flow control is so good, why not retain it? r Easy to show that “TCP-friendly” r Get rid of reliable/in-order delivery mechanisms that get in the way.

Prioritization in HPF r Allows marking packets high/low priority r Provides In-order reliable delivery of high priority packets r Allows low priority packets to be delivered when enough BW available r If routers support priority, can drop low priority packets ahead of high priority packets

HPF Layers* r Application Framing (AF) -- convert frames into packets, packets into frames r Windowing, Reliability, Timing and Flow-control (WRTF) -- window management, flow control, reliability, deadlines r Congestion Control (CC) -- congestion response, estimation of RTTs

HPF Architecture*

HPF*

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

Conclusion r CUDP m Allows Timely Delivery and discard of expired packets, prioritization m Not clear if more aggressive than TCP m Not a multiplicative decrease response r HPF m UDP-based delivery puts application in charge to do flow control, congestion response etc. m Tedious for every application to implement all the basic mechanisms* m Separate ALF policies and implementation -HPF does this and follows TCP based congestion response*