IEEE LCN 2007: Kalman Graffi - Overlay Bandwidth Management: Scheduling and Active Queue Management...
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Transcript of IEEE LCN 2007: Kalman Graffi - Overlay Bandwidth Management: Scheduling and Active Queue Management...
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Dipl.-Math. Dipl.-Inform. Kalman Graffi
KOM - Multimedia Communications LabDept. of Electrical Engineering and Information Technology, Dept. of Computer ScienceTUD – Technische Universität Darmstadt Merckstr. 25, D-64283 Darmstadt, Germany, [email protected] Tel.+49 6151 164959, Fax. +49 6151 166152
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Overlay Bandwidth Management: Scheduling and Active Queue Management of Overlay Flows
Kalman Graffi, Konstantin Pussep, Sebastian Kaune, Aleksandra Kovacevic, Nicolas Liebau, and Ralf Steinmetz
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Example: Bandwidth Usage in Unst. P2P Overlay
Queries
I cannot hear youHelp!
Emergency!
Unimportant
Bandwidth usage :
• Irrelevant search queries starve relevant queries• Overlay flow specific QoS demands unconsidered
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Outline
Motivation and Scope
Background: Scheduling and Active Queue Management
Contribution:• Characteristics of Overlay Flows• Requirements and Related Work• Overlay Bandwidth Management Layer• HiPNOS.KOM - Our Solution
Evaluation
Future Work and Conclusion
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Motivation for Bandwidth Management
Emerging commercial P2P applications require• Quality of Service• Crucial for long-term success of P2P paradigm
Most critical resource in P2P systems: bandwidth• In most cases the bottleneck in the system• Required for maintenance and service provisioning
P2P specific bandwidth management needed• Control the bandwidth, provide QoS• Overlay independent solution
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Which Flows are in Focus?
Types of flows in P2P systems
• Layer 4 traffic flows: • Underlay perspective• Out of scope
• Direct P2P communication: • File transfer, application traffic, …• Few, but large data streams (elephants)• (Often) with low priority for the system
• Overlay flows• Multi-hop: maintenance, user queries…• Many, small messages (mice)• Varying relevance for system
Provide QoS to overlay flow according to its relevance
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Learn from network layer
• Scheduling• Reorder tasks/messages in queue• Reference: First-in-First-Out
• Active Queue Management • Drop msg. upon congestion of queue• Reference: Drop Tail
Research challenge: how to apply on overlay layer?
Scheduling and Active Queue Management
Message
1. Message SchedulingBefore:
After:
2. Queue ManagementBefore:
After:Queue Limit
Sched.+AQM
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Overlay Bandwidth Management
Generally applicable overlay bandwidth management• New layer Network Wrapper: API between overlay and underlay
Research challenge: Which requirements are defined• by overlay flow characteristics• for the SCHED + AQM used
In-from overlay
Insert msg in buffer
Apply AQM mech.
Timeout
Pick next msg (SCHED)
Out to underlay
Bandwidth available?
Receive message
yesno
Buffer management
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Observation• Huge number of contacts with few messages each• Overlay “flows” and traditional flows differ significantly
Conclusion • Stateless scheduler needed• Quality of service information are stored in messages
Analyzing Overlay Flows in Kademlia
Simulation of KademliaSetup:
• PeerfactSim.KOM• 10,000 peers, all join,
random store/lookupMetrics:
• # of contacts per peer• # of msg per contact
Results:
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Requirements and Related Work
Requirements:• QoS attributes per message (defined by higher layer):
• Introduce delay priority (ϵ PD) and loss priority (ϵ PL)• Quality req.:
Related Work see paper/Technical Reports of author• SCHED and AQM proposed for routing layer (L3)
Expect long-term flows, not existing in overlays• Overlay bandwidth management in overlays
• Mobile P2P (on UMTS/GSM), P2P multimedia streams Focus on underlay/multimedia
characteristics• GIA [Chawathe, 2003], controls incoming traffic
Sched. and AQM mechanism for overlay flows needed
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HiPNOS.KOM: Highest Priority First, No Starvation• Introduce (independent) message priorities
• For loss – criticality (1 byte)• For delay – criticality (1 byte)
Active Queue Management solution:• If buffer size exceeded:
• Drop message with lowest loss-prio.
Scheduling solution• If bandwidth available:
• Pick message with highest latency-prio.
Avoid starvation• Periodically increase delay-prio. of queued messages
Our Solution: Sched. and AQM of Overlay Flows
In-from overlay
Insert msg in buffer
Apply AQM mech.
Timeout
Pick next msg (SCHED)
Out to underlay
Bandwidth available?
Receive message
yesno
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Evaluation Setup
Compare HiPNOS.KOM with reference solution• First In, First Out: reference scheduling solution• Drop Tail: reference active queue management mech.
Simulation Setup:• Simulated: Kademlia on PeerfactSim.KOM• Scenario:
• 10000 peers join, heterogeneous bandwidths• Peers perform random store/lookup operations• Msgs with random delay/loss priorities: -128 to 127
• Varying: HiPNOS.KOM and FIFO/Drop Tail• 20 simulation runs per setup• Metrics: Delay of msgs and number of dropped msgs
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Evaluation Results of HiPNOS.KOM
Results:
Quality of service increases with priority • Delay antiproportional to priority• Loss decreases with increasing priority
QoS requirements of overlay flows can be fulfilled
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Future Work
Observation:• QoS requirements fulfilled: higher prio., better QoS• Even minimal mechanisms are sufficient
Conclusion:• Shift of research focus:
• Not how to provide QoS for overlay flows (solved)• But how set QoS priorities of overlay messages
Next steps:• Emergency Call Handling (ECH) over P2P Overlays
• Globase.KOM used to find closest Emergency Station• ECH messages have highest priority in overlay• Fulfills legal and technical requirements for ECH
• Security issues• Evaluate with more overlay types (unstructured…)
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ConclusionProblem: QoS for overlays currently not supported
• Overlays cannot be used for critical applications• Heterogeneity of message relevance not supported
Contribution:• Overlay flow characteristics identified: only mice flows• Introduce message priorities for loss and delay• HiPNOS.KOM enables P2P overlays to support QoS
demands
Evaluation:• Good/expected results show effectiveness of solution
Impact:• Increase of stability, scalability, robustness …
• of overlay and application• for low (no?) costs
• Enables QoS-based applications
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Questions?
Kalman Graffi
Peer-to-Peer Research Group
Dept. of Electrical Engineering and Information TechnologyMultimedia Communications Lab · KOM
Merckstr. 25 · 64283 Darmstadt · GermanyPhone (+49) 6151 – 16 49 59Fax (+49) 6151 – 16 61 [email protected]
Further information: http://www.KOM.tu-darmstadt.de/
Publications: http://www.KOM.tu-darmstadt.de/Research/Publications/publications.html