DHARMA: Distributed Home Agent for Robust Mobile Access

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DHARMADistributed Home Agentfor Robust Mobile
Access

• Yun Mao
• University of Pennsylvania
• Joint work with
• Bjorn Knutsson, Honghui Lu, and Jonathan M. Smith
• March 2005

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Vision
Ethernet
Residential Access Point
Departmental Access Point
Hot spots
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Butwhat about intermittent connectivity?
Scenario 1 intentional disconnections
Residential Access Point
Departmental Access Point
Travel with laptop hibernated
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Scenario 2 Unintentional disconnections
path failure
Internet
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Outline

• What are the fundamental issues in laptop
  mobility?
• DHARMA Our solution
• Evaluation
• Related work
• Conclusion

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Mobility Problem Statement

• Two orthogonal problems
• Addressability
• Induced by switching network attachment points
• Connectivity!!!
• intermittent as opposed to always-on
• Disruptive to TCPs circuit model
• Design goals
• Robust
• Practical
• Incrementally deployable
• Efficient

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layering
Application Layer
Transport Layer
Network Layer
Link Layer
Physical Layer
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layering
Application Layer
Session Layer
DHARMA
Transport Layer
Network Layer
Mobile IP
Link Layer
Physical Layer
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DHARMA End to end mode
Application Layer
Application Layer
Session Protocol
Session Layer
Session Layer
Identify sessions Explicit resume/suspend Failure
detection
Transport Layer
Transport Layer
Network Layer
Network Layer
Link Layer
Link Layer
Physical Layer
Physical Layer
unreliable network
Mobile Host
Correspondent Host
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Proxy-based mode
Application Layer
Session Protocol
Session Layer
Application Layer
Session Layer
Transport Protocol
Transport Layer
Transport Layer
Transport Layer
Network Layer
Network Layer
Network Layer
Link Layer
Link Layer
Link Layer
Physical Layer
Physical Layer
Physical Layer
unreliable network
reliable network
Legacy Correspondent Host
Home Agent (with fixed IP)
Mobile Host
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Implementation
Correspondent Host
Home Agent (with fixed IP)
Mobile Host
Remote Proxy
Application
Application
Local Proxy
wrapper
lo
ethX
eth0
eth0
unreliable network
reliable network
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Efficiency concern
Correspondent Host
Home Agent
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Efficiency concern
Correspondent Host
Mobile Host (MH)
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Distributed Agents A birds eye view
Agent y
Mobile Host
Agent 1
Agent 2
Correspondent Host
Agent x
Agent 4
Agent 3
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Distributed Agents A birds eye view
The closest one to the CH
Agent y
Mobile Host
Agent 1
Agent 2
Correspondent Host
Agent x
Agent 4
Agent 3
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Distributed Agents A birds eye view
The closest one to the CH
Agent y
Agent 1
Agent 2
Correspondent Host
Agent x
Agent 4
Agent 3
Mobile Host
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Design
ch.upenn.edu
ch.upenn.edu
Agent y
Agent 1
Agent 2
Agent 2
Correspondent Host
Portal Server
Agent 4
Agent 3
Mobile Host
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Technical details

• Session protocol
• Reverse DNS lookup based heuristics
• Caching and prefetching tokens
• TCP semantics
• Security concerns
• Further details in our paper

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Evaluation

• Prototype works!!
• Many success stories
• Remote X-windows survive overnight laptop
  hibernation
• Support legacy TCP applications
• Works on Windows and Linux platforms
• 24x7 service running on PlanetLab
• 300 geographically distributed home agents
• Semi-open

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Simulation

• Routing efficiency by simulation in real world
  network topology
• Mobility pattern according to Pareto distribution
• Comparing to mobile IP

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Improvement vs. conventional Mobile IP
Mobile IP (Bi-directional tunneling)
Lower is better
Mobile IP (triangle routing)
DHARMA
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Related work

• Addressability
• Mobile IP(Ioannidis91, Perkins98,02)
• MSOCKS(Maltz98)
• HIP (IETF draft 05)
• ROAM(Zhuang03), Wrap(Zhao04)
• Connectivity
• Migrate (Snoeren01), Rocks (Zandy02)
• Do not work with legacy CHs
• Could take advantage of DHARMAs approach

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Conclusion

• A unified, incrementally deployable approach
  towards session-based mobility
• Dynamic HA selection in overlay networks
• A demonstration of flexibility, effectiveness and
  ease-of-use of our prototype system.
• http//dharma.cis.upenn.edu
• Download and try it today!

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