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Example path application:Jukebox/cell-phone application
• Ninja Jukebox:– service providing real-time streaming audio
data from a collection of CDs in the network
• GSM Cell-phone:– 12kbps data, 13kbps voice– communicates with BTS
Jukebox
JukeboxPath
:operator :connector
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What is a path?
• A way to compose services to create customizable complex services
• Goals:– composability– accessibility– availability, fault-tolerance– scalability– security
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Overall path construction process
– a continuous optimization process with feedback:
Path Instantiation, Execution, Maintenance
Logical Path Creation
Physical Path Creation
Path Tear-down
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Logical path creation:Path matching algorithm
• Formulated as shortest path graph search– Operators ===> edges– Data format/type ===> nodes
• Dijkstra’s shortest path algorithm– O(v2)
• Difficulty: expressing constraints and optimization variables
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Path maintenance:Partial Path Repair (PPR)
• APC(Automatic Path Creation) service guarantees robustness and fault-tolerance
• Two ways of monitoring:– active checking of operator status– operators notify APC of neighboring operators’
failure
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Performance measurements(4 operators, Jukebox/cell-phone app)
• Logical/Physical path creation time: 264ms
• Path instantiation time: 215ms– operator instantiation: 70ms– connector creation: 64ms– start operator running: 81 ms
• Path recovery: one operator fails– Time to detect failure of operator: 2ms– Time to repair one failed operator: 400ms
• Path tear-down time: 289ms
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Open design issues
• Wide area considerations• Improved path reliability model• Path performance modeling• Path resource management framework• Flexible path control
– control path, path migration, dynamic adaptation
• Applications for paths• Metrics for evaluation
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Wide area path design
APC
APC
APCSAN
SAN
SAN
WAN WAN
service
Hierarchical APC Service
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Step-by-step WAN path creation for Jukebox/Cell-phone application
1. End-user using cell-phone requests access to Jukebox service
• QoS needs: delay-sensitive, reliable service
2. APC uses graph search algorithm finds the logical path
3. APC searches for the physical path1. Finds relevant parameters affecting QoS, determines
the reliability model
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Step-by-step WAN path creation for Jukebox/Cell-phone application
5. Obtains resource information from resource management framework
6. Uses queuing model to evaluate choices
7. APC selects the optimal choice
8. APC dynamically adjusts the decision given feedback from the resource monitoring tools
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Operator placement decisions
• Depend on– operator computational requirement– software/hardware requirement– output/input properties
• data location, data volume, delay-sensitivity, degradation properties
– network characteristics• bandwidth, latency, jitter, packet loss
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Path resource management framework
• develop network monitoring tools– to obtain network statistics
• Available resources– computational, memory, network etc.
• Make trade-offs due to interdependencies among resources
• resource allocated per path basis
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Path resource management framework
• A high-level global hierarchical resource manager
• Local resource manager per SAN
• Runtime resource monitoring tools monitor/discover resource changes during the lifetime of paths
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Applications for paths
• Operators:– content transcoding operators:
• text-to-speech, mp3-to-PCM, PCM-to-GSM
• web search tools, filtering, aggregation, personalization
• Microsoft COM objects, existing Web services...
• Document conversion services
– protocol translation operators:• serial socket, security transcoder, RMI Lite
Any service Any device
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Measurement metrics
• Path creation time– logical/physical path creation, instantiation, execution
• Scalability– number of paths created per amount of time
• Fault-recovery time• Control, ease-of-use, programmability of paths• Ease of transparent path migration, adaptation to
resource changes
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Conclusion
• Recent work:– APC prototype built for SAN with reasonable
performance, Partial Path Repair
• Future work:– focus on WAN, scalable path design
– WAN test plan: campus-wide millennium cluster
– support for continuous path optimization and adaptation
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For more information
• Please send comments/questions to Z. Morley Mao – [email protected]
• Slides will be available at:– http://www.cs.berkeley.edu/~zmao/paths
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Extra Slides
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Flexible path control: control path
• Control path– Definition: make changes of operators, connectors
• independent of data path• highly-available, fault-tolerant• Proposed design:
– replicated control paths:• neighboring operators have control over each other
• APC has complete control over localized operators
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Flexible path control: path migration
Two paths of different quality running– migrate from the fast-to-startup, lower-quality one to
slow-to-startup, higher-quality one
• Transparent migration of paths– dynamic fusion of operators – dynamic deletion, addition, replacement of
operators/connectors– Goal: adapt changes in resources and locations of end
points
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Wide area considerations
• Goal: scalable, network-partition-tolerant• proposed design:
– replicated APC service instances
– state of paths partitioned and replicated
– operators are soft-state
– continuous monitoring of operators and connectors by APC service instances
– a few localized path components hooked together over wide area
