A Step Back Reflections on P2P Techniques

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A Step BackReflections on P2P Techniques

• Indranil Gupta
• March 16, 2006
• CS 598IG. SP06.

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Lets keep it Short Today

• 2 P2P or Not to P2P
• Scooped, Again

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2 P2P or Not 2 P2P?

• Mema Roussopoulos
• Mary Baker
• David S. H. Rosenthal
• TJ Giuli
• Petros Maniatis
• Jeff Mogul

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Candidate problems
Kerry

• Internet Routing (RON)
• Resource Sharing (PlanetLab)
• Cooperative Web Caching
• Internet Backup and Corporate Backup
• Distributed Digital Libraries
• Distributed Monitoring
• Ad hoc Routing in Disaster Recovery
• Metropolitan-area Cell Phone Forwarding

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Ideal P2P properties

• Self Organizing
• P2P routing
• Discovery
• Symmetric communication
• Peers are approximately equal
• Decentralized control
• No single point of failure

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P2P Networks
Usenet
Gnutella
Images from http//www.cybergeography.org/atlas/mo
re_topology.html
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2 P2P or not P2P
Budget
Relevance
Trust
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Budget
Low
Effect
High

• Lowest possible cost per peer, rather than lowest
  global cost
• Bittorrent, Gnutella, Freenet, etc.
• SETI_at_home

• Dictates how many peers join
• Decides if P2P is viable for problem

• Worries less about performance criticality
• Favors centralized approaches, P2P irrelevant
• Clusters, High performance computing

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Relevance
Low
Effect
High

• Personal data
• Private data
• Internet backup
• Corporate backup
• Web caching

• Relevance of resources encourages peers to join
• When resource relevance is high, cooperation in
  a P2P solution evolves naturally

• File sharing
• Freenet
• Content distribution
• Internet routing
• Bit Torrent
• Gnutella
• Kazaa

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Trust
Low
Effect
High

• Encryption
• Anonymity
• Freenet
• Oceanstore
• Ivy
• Timestamping
• MojoNation

• Mutual trust
• Risks

• Gnutella
• Napster
• Overlays
• File sharing
• Usenet

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Rate of Change
Low
Effect
High

• Tangler
• Freenet
• LOCKSS
• Time stamping
• Content distribution
• Usenet
• Flash crowds

• Churn
• Timeliness
• Consistency

• Internet routing
• Online net monitoring

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Criticality
Low
Effect
High

• Usenet
• Content distribution
• Offline net study
• File sharing

• Centralized control
• Accountability
• Fault tolerance

• Ad hoc disaster recovery
• Flash crowds
• Internet monitoring
• Routing

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2 P2P or not P2P
Budget
Relevance
Trust
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Conclusion

• Framework for analyzing P2P applications
• Captures constraints and app requirements
• Limited budget is motivating factor
• Problems with low relevance are inappropriate for
  P2P
• Same as our Penny Lane motivation for P2P
  systems

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Critique

• Strengths
• Quantifies application requirements and suitable
  use cases
• Generically describes suitability of classes of
  P2P apps
• Weaknesses
• High churn p2p inappropriate? Or most current
  non-Kelips solutions insufficient?
• Why cant p2p systems handle critical
  applications? Its a question of developing the
  right, e.g., real-time, technologies.
• Why is the order of preference budget relevance
  trust churn criticality? Why not a
  different ordering?
• Fuzzy requirements not accounted for
• Other requirements will they evolve as new p2p
  applications emerge?

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Scooped, Again

• Jonathan Ledlie
• Jeff Shneidman
• Margo Seltzer
• John Huth

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Outline

• Introduction
• Grid Computing
• P2P Systems
• Fallacies preventing cooperation
• Shared and Disjoint Problems
• Conclusions

What they are, Goals, Manifestations
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Introduction

• Peer-to-Peer vs. Grid Computing
• Overlapping problem domain
• P2P focuses on research
• Grid is concerned with concrete, tangible
  solutions
• History, repeated the Web

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Introduction cont.

• Current trends
• Divergent, parallel development
• Duplication of work
• Grid risk of non-optimal solutions
• Missing out on P2Ps strong achievements (search
  and storage scalability, decentralization,
  anonymity, denial of service prevention)
• Cooperation is the key

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Grids

• What is the Grid?
• a type of parallel and distributed system that
  enables the sharing, selection, and aggregation
  of resources distributed across multiple
  administrative domains based on the resources
  availability, capability, performance, cost, and
  users QoS requirements
• Short version virtualizing computer resources
• Large scale heterogeneous resource sharing
  (different platforms, hardware/software
  architectures, and computer languages)
• Functional classification
• Computational grids (run batch jobs during idle
  times)
• Data grids

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Grid Layout
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Grid Goals

• Design goal
• Solve problems too big for a single
  supercomputer, but retain the flexibility to work
  on multiple smaller problems
• Self-configuring, self-tuning, self-healing
• Allow data sharing and support computation across
  administrative domains
• Standardized programming interface
• GGF (Global Grid Forum)
• Globus toolkit the de facto standard for grid
  middleware

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Grid Manifestations

• Protocols
• Resource management
• Grid Resource Allocation Management Protocol
  (GRAM)
• Information services
• Monitoring and Discovery Service (MDS)
• Security services
• Grid Security Infrastructure (GSI)
• Data movement and management
• Global Access to Secondary Storage (GASS),
  GridFTP
• Tools
• Grid Portal Software (GridPort, OGCE)
• Grid Packaging Toolkit
• Grid-enabled MPI (MPICH-G2)
• Network Weather Service
• Condor (CPU cycle scavenging) and Condor-G (job
  submission)
• APIs
• Web Services Open Grid Services Architecture
  (OGSA)

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P2P

• What is P2P?
• a class of applications that take advantage of
  resources storage, cycles, content, human
  presence available at the edges of the
  Internet
• Decentralized, non-hierarchical node organization
• Inherently untrusted (well)

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P2P Goals

• Cost sharing / reduction
• Every peer responsible for its own cost
• Reduction of file storage costs
• Reduction of computation costs
• Improved scalability / reliability
• Lack of centralization allows new algorithms
  (CAN, Chordetc) to be designed to allow improved
  scalability
• Resource Aggregation
• Every peer lends its own resources to the network
• Increased Autonomy
• Tasks are performed locally no central service
  provider

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P2P Goals cont.

• Anonymity / Privacy
• FreeNet
• Dynamism
• Nodes enter and leave the system in a transparent
  way
• Ad-hoc communication
• Members can join and leave based on their
  physical location or interests

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Summary

• Grids
• Parallel, distributed systems concerned with
  resource sharing, selection, aggregation
• Resource availability, capability, performance,
  cost, and user QoS requirements are considered
• Self-configuring, self-tuning, self-healing
• Idle cycle and storage utilization

• P2P
• Distributed systems that take advantage of
  resources scattered throughout the Internet
• Decentralized, non-hierarchical node organization
• Concerned with fault-tolerance, scalability,
  availabilityetc.
• Idle cycle and storage utilization

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Summary cont.

• Grid
• Distributed computation
• distributed.net
• SETI_at_home
• Data production / aggregation

• P2P
• Distributed file sharing
• Gnutella, KaZaA
• Distributed computation
• distributed.net
• Anonymity
• Freenet, Publius

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Outline

• Introduction
• Grid Computing
• P2P Systems
• Fallacies preventing cooperation
• Shared and Disjoint Problems
• Conclusions

What they are, Goals, Manifestations
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Fallacies preventing cooperation

• The technical problems in Grid systems are
  different from those in p2p systems
• Usage misconception Grid for computing problems,
  P2P for file sharing
• Data handling and data production in Grid systems
  has become important
• P2P used in desktop collaboration and network
  computation
• open problems in both camps have striking
  similarities

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Fallacies preventing cooperation

• While the technical problems are similar, the
  architectures (physical topology, bandwidth
  availability and use, trust model, etc.) demand
  that the specific solutions be fundamentally
  different
• Solving common problems through sharing good
  ideas from each community
• Application dependent special requirements
  tailored to application needs, however the
  technical approaches for solving a particular
  problem could benefit both communities

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Fallacies preventing cooperation

• Grid projects do not have the flexibility to try
  new algorithms/ideas because they have to get
  real work done. P2P research is all about this
  flexibility
• Grid has room for flexible research, too
• Testing new applications and protocols
• Users willing to adopt different technologies to
  get the work done

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Outline

• Introduction
• Grid Computing
• P2P Systems
• Fallacies preventing cooperation
• Shared and Disjoint Problems
• Conclusions

What they are, Goals, Manifestations
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Shared problems

• Topology Formation
• Node join and neighbor discovery
• Work has been done by both groups
• Grid On fully decentralized resource discovery
  in grid environments
• P2P Self-organization in p2p systems
• Grid infrastructure in not flexible hard coded
• Could benefit from P2P research prototypes

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Shared problems cont.

• Utilization
• Resource discovery, data retrieval
• P2P hash-based look-up schemes are useful
• Resource management / optimization
• How to best utilize resources in a network
• Data replication/caching examined by both
  communities
• Scheduling and handling of contention
• P2P focus bandwidth usage (e.g. Gnutella)
• Grid focus scheduling
• Load balancing break large tasks into
  distributed smaller ones

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Shared problems cont.

• Coping with Failure
• P2P lossy storage model (Freenet, Gnutella)
• Considerations for Grid adaptability
• Different common loss model
• Storage size (O(petabyte/month))
• Security-related issues
• Authenticity verification of data/computation
• Availability resilience to DoS attacks
• Authorization ACLs

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Shared problems cont.

• Maintenance
• P2P essentially no standards or APIs
• Efforts by Berkeley BOINC, Google Compute,
  overlay standardization
• Grid pushes for a standardized API
• GGF (Global Grid Forum)
• OGSA (Open Grid Services Architecture)
• Web services oriented API Globus as reference
  implementation

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Disjoint Problems

• Anonymity
• Not really useful for Grid systems, yet

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Conclusions

• A lot of overlap between the goals and research
  interests of the two communities
• P2P community needs to consider the needs of the
  Grid users to see how existing research can be
  applied successfully to Grid problems
• Aim for common standards as much as possible

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Critique

• Since this paper was published (2003), a little
  bit of convergence has happened, but not as much
  as predicted by these authors and as predicted by
  Foster et al
• Will it just take more time?
• (Skeptics Viewpoint) Really? Arent P2P and Grid
  two different areas?
• They still have mostly-disjoint research
  communities
• Or is that an opportunity for more researrch?

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Have a good Break!

• Remember Midterm report (with initial
  experimental data) is due April 2!