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Quality-Of-Service (QoS) Panel

Quality-Of-Service (QoS) Panel. SWiM, Stanford University, January 9, 2003. Mitch Cherniack Brandeis David Maier OGI Rajeev Motwani Stanford Johannes Gehrke Cornell Hari Balakrishnan MIT. Scheduled according to their QoS emails…. Three Talking Points.

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Quality-Of-Service (QoS) Panel

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  1. Quality-Of-Service (QoS) Panel SWiM, Stanford University, January 9, 2003 Mitch Cherniack Brandeis David Maier OGI Rajeev Motwani Stanford Johannes Gehrke Cornell Hari Balakrishnan MIT Scheduled according to their QoS emails…

  2. Three Talking Points • Why (If) QoS is Appropriate for Streams • Expressing QoS for Streams • Processing QoS for Streams

  3. U (x) x What is QoS? • Resource mgmt driven byapplication reqts • Each app specifies its own error-tolerance (delay, inaccuracy,…) • Utility Functions x-axis: Delay (sec), Inaccuracy (% dropped),… y-axis Utility ([0..1])

  4. What is QoS? • QoS Specs Used to Drive: • Admission control • Resource reservation • Load shedding… • Prominent Domain: Networks w/ Real-Time Apps (e.g., multimedia streams) • Resource Management (Bandwidth) • Non-Uniform Error-Tolerance (Frame rate, jitter,…)

  5. Why QoS is Appropriate for Streams An Example: Battlefield Monitoring Resource Management: numerous data sources (soldiers outfitted with sensors: GPS, vital signs, …) numerous monitoring queries Non-Uniform Error-Tolerance: remote triage (low latency, some inaccuracy ok) remote enemy tracking (some latency ok, accurate) missile detection (low latency, no inaccuracy)

  6. Why QoS is Appropriate for Streams Processing QoS Specs for Streams • Operator Scheduling • Load Shedding • Query Optimization • Tuple Reordering • Load Balancing…

  7. QoS-Driven SchedulingGoal: Maximize Overall QoS Delay = 2 sec Utility = 0.5 A: Cost: 1 sec Choice 1: (…, age: 1 sec) Delay = 5 sec Utility = 0.8 B: Cost: 2 sec Choice 2: (…, age: 3 sec) Schedule Box A now rather than later Ideal: Maximize Overall Utility

  8. Stream Networks ¹ Packet Networks 1. In-Flight Generation of Tuples Complications in expression of QoS Specs 2. Semantic Richness of Tuples Opportunities in processing QoS Specs

  9. Expressing QoS for Streams Packet Networks p p p p p p p p packetlost from result Reasonable measure of inaccuracy: Packets dropped / Total Packets

  10. Expressing QoS for Streams Stream Networks sp t tuplelost from result? Depends onp(t) true Þtuple lost from result falseÞtuple not lost from result

  11. Expressing QoS for Streams Stream Networks CNT t tuplelost from result? No, but less accuracy in calculation

  12. Expressing QoS for Streams Stream Networks t tuplelost from result? 0 or more tuples lost from result

  13. Stream Networks ¹ Packet Networks 1. Tuples Generated In-Flight Complications in expression of QoS Specs • Multiple Flavors of Inaccuracy • (lost tuples, imprecise tuples) • Impact of dropped tuples hard to determine • (depends on where in network dropped)

  14. Stream Networks ¹ Packet Networks 2. Semantic Richness of Tuples Opportunities in processing QoS Specs Aurora example: Value-based QoS Load Shedding: Drop less valuable tuples Scheduling: Process most valuable tuples 1st

  15. Conclusions • QoS is Appropriate for Streams Resource management Apps w/ non-uniform toleration of error 2) Streams vs Packets Networks. In-flight tuple generation Complicate Expression/Calculation of QoS Semantic Richness of Tuples Offer Processing Opportunities (Value-Based QoS)

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