P2P Simulation Platform Enhancement

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P2P Simulation Platform Enhancement

• Shih Chin, Chai
• Superviser Dr. Tim Moors
• Assessor Dr. Robert Malaney

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INTRODUCTION

• Part of the Peer-to-Peer (P2P) Sharing of
  Networks Performance Measurements Project
• Focus on enhancing the current simulation
  platform for the development of meaningful
  simulations

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P2P Network

• A distributed system architecture
• No centralized control
• Nodes are symmetric in function
• Large number of unreliable nodes

Fully decentralised
Jane
Judy
Centralised
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P2P networking
Focus at the application level
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MOTIVATION

• Many internet applications, currently based on
  the client-server architecture, will be more
  robust if built on decentralized self-organizing
  overlays (aka Peer-to-Peer Systems).

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More Robust????

• Reliable no single point of failure, many
  replicas.
• Scalable evolves smoothly to millions of nodes.
• High capacity through parallelism many disks,
  many network connections, many CPUs.

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Latest Generation

• Chord (MIT)
• Tapestry (UCB)
• Pastry (Microsoft Rice)
• CAN (UCB ACIRI)
• ..

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Basic lookup in Chord
N120
N10
Consistent Hashing keyID SHA_1(key) nodeID
SHA_1(IP)
Where is key 80?
N105
K15, K30
N32
N90 has K80
N90
K80
7-bit ID space
N60
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P2P networking
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Locality Awareness

• Minimize wide-area traffic, bandwidth
  utilization, congestion, and sensitivity to
  wide-area faults
• Performance in the local area is particulary
  important when many paths can stay entirely
  within the local area.
• We want to make sure that the lookup path stay
  locally whenever its possible.

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Search for Low Stretch

• The measure of locality efficiency is stretch,
  the ratio of the distance traveled to find a copy
  of an object to the distance to the closest copy.
  
• Two of the Distributed Hash Tables(DHT) Tapestry
  Pastry

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Roles of Simulators

• Evaluate the performance of p2p systems, in terms
  of cost (e.g. bandwidth) and value (e.g.
  reliability)
• Provide a "good" abstraction of the real network
  and application for experimental purposes.

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The Dangers in Simulating P2P

• Differences in performance may be due to
  simulator, not p2p system, if different
  simulators are used.
• Simplified to the point where key facets of the
  network behavior have been lost

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Todays P2P Research

• Lack of common simulation platform until recently
  p2psim, peersim have been developed, publicly
  available.
• Current projects still mainly use own simulators.
  (Bad..)
• Q Could a small change in the model result in a
  large change in the outputs? More treacherous..

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My Approach

• The most useful simulator for long-term research
  interests would be the one that incorporates
  various proposals by different researchers, e.g.
  ns-2, Opnet
• This thesis is about a collaborative effort to
  contribute toward a common network simulator in
  P2P networking.

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Intro to p2psim

• Developed by MIT research group
• Written in C
• Multi-threaded
• Discrete-event simulator
• Currently supports Chord, Accordion, Koorde,
  Kelips, Tapestry, and Kademlia.

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Initial (Part A) simulation results

• Aim To evaluate the stretch performance of
  Tapestry
• Setup
• Hardware Pentium 4 CPU 3GHz
• OS Linux 9, gcc version 3.2.2
• Topology King-topology
• Node 1740
• Run Time 40hours
• Method Evaluation under churn

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Simulation Results
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Analysis

• The graph shows that the stretch decreases as
  bandwitch per node increases. However, the actual
  path of a query takes does not show.
• Conclusion More aggressive approach is needed to
  evaluate the actual locality performance

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Goals for thesis part B

• Modify p2psim to output path information for
  individual queries so that complete stretch
  characteristics can be determined
• Implement DHTs that have good support for
  locality, proximity and stretch in p2psim, such
  as Pastry

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Plan Part I

• Expected challenge Current simulator only
  supports end-to-end latencies.
• Possible solution Use an IP-layer topology file,
  GT-ITM with p2psim, because GT-ITM deals with
  IP-layer nodes, which possibly enable us to count
  IP hops of a query.

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Plan Part II

• Expected challenge Huge program. gt3000 lines of
  C code as the outcome.
• Proposed tools
• The Tapestry code
• Based on the paper, Pastry Scalable,
  decentralised object location and routing for
  large-scale p2p systems. (Microsoft Rice)
• P2psim mailing list

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Task Schedule
Debugging Refinement
Week 1-4 Modify p2psim to output stretch
Week 13 14 Final Report and Open Day
Week 5 10 Implement Pastry
Week 11 12 Evaluation and Testing
Documentation Project Management
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Summary

• Enhance p2psim
• Add in new features
• Output query path
• New protocol
• To evaluate the stretch issues our project after.
  Nonetheless,
• For long term research interest.

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Reference

• Li JY, Stribling J, Morris R., Kaashock M.F., Gil
  T.M., A performance vs. cost framwork for
  evaluating DHT design tradeoffs under churn, MIT.
• Stoica I., Morris R., Karger D., Kaashock MF.,
  Balakrishnan H., Chord, MIT and Berkeley.
• Zhao B.Y, Kubiatowicz J., Joseph AD., Tapestry,
  UCB.
• Rowstron A., Druschel P., Pastry, Microsoft and
  Rice University.
• Kurose J., Levine B., Towsley D., Peer-peer and
  Application level networking, http//gaia.cs.umass
  .edu/cs791n
• Floyd S., Paxson V., 2001, Difficulties in
  simulating the Internet, ACIRI, Berkeley.
• Risson J., Moors T., Towards Robust Internet
  Applications Self-Organizing Overlays, UNSW.

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• ANY QUESTION?

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Tapestry MeshIncremental suffix-based routing
NodeID 0x79FE
NodeID 0x23FE
NodeID 0x993E
NodeID 0x43FE
NodeID 0x73FE
NodeID 0x44FE
NodeID 0xF990
NodeID 0x035E
NodeID 0x04FE
NodeID 0x13FE
NodeID 0xABFE
NodeID 0x555E
NodeID 0x9990
NodeID 0x239E
NodeID 0x1290
NodeID 0x73FF
NodeID 0x423E
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Routing to Nodes
Example Octal digits, 218 namespace, 005712 ?
627510
005712
340880
943210
834510
387510
727510
627510
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Object LocationRandomization and Locality
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Pastry Routing
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Proximity Neighbor Selection

• Node is chosen based on the proximity metric
• Routing step
• 1. check the leaf set
• 2. then the routing table