Current Issues in P2P Systems

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Current Issues in P2P Systems

• Christoph Schmitz
• 24.6.2002

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Exchanging Content in P2P Networks Vision
?
?
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Recent Workshops and Conferences
IPTPS 02
O'Reilly 01
AP2PC 02
Security
Security
Anonymity
Trust
Performance
Workload characterization
Web Services
Web Services
Agents
Infrastructure
Infrastructure
Semantic Web
Metadata/Search
Self organization
Sociometry
Scalable Distributed Datastructures
Intellectual Property Rights
Intellectual Property Rights
Collaboration
Business Models
File Sharing
Applications
Distributed Computation
Data Mining
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Security and Protection Trust Anonymity Reputation
Business and Legal Issues Business
Models Intellectual Property Rights
Sociometry Small World Phenomena Power-Law
Networks
Network Architecture and Design Network
Topology Routing Overlay Networks
P2P
Distributed Databases Query Decomposition Query
Distribution Mediation
Distributed Data Structures Distributed Hash
Tables Scalable Distributed Data Structures
Intelligent Agents/ Web-based Services Matchmaking
Service Description
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Security and Protection Trust Anonymity Reputation
Business and Legal Issues Business
Models Intellectual Property Rights
Sociometry Small World Phenomena Power-Law
Networks
Network Architecture and Design Network
Topology Routing Overlay Networks
P2P
Distributed Databases Query Decomposition Query
Distribution Mediation
Distributed Data Structures Distributed Hash
Tables Scalable Distributed Data Structures
Intelligent Agents/ Web-based Services Matchmaking
Service Description
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Overlay Networks

• Layer on top of existing infrastructure
• Cope with
• Masquerading/Dynamic IPs
• One address may represent many nodes
• One node may appear under many addresses
• Firewalls
• Only certain types of traffic allowed
• Employ your own
• Adressing scheme
• Topology
• Routing mechanism

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Overlay Networks (II) JXTA
Output Pipe
Service B
Service A
Service C
Input Pipe
RDV
Peers identified by PeerID
RDV
TCP/IP Network
Relay
Firewall NAT
TCP
HTTP
TCP/IP Network
TCP/IP Network
TAD02
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Routing (I) Current State in P2P
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Routing (II) TCP/IP - CIDR

• Aggregation of information about networks
• Smaller routing tables

Internet Service Provider
The Internet
200.25.0.0/16
200.25.32.0/20
200.25.16.0/20
200.25.16.0/24 200.25.17.0/24 200.25.18.0/24
200.25.28.0/24 200.25.29.0/24
200.25.24.0/24 200.25.25.0/24
ISP Client 1
ISP Client 3
ISP Client 2
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Routing (III) Towards semantic routing

• Routing Indices
• Maintain aggregated view of term frequency count
  behind each link
• Make use of small-worldproperties!
• Updates? Cycles?

Foo 5 Blah 5
Foo 25 Bar 60 Blah 25
Foo 20 Bar 60 Blah 20
CGM01
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Security and Protection Trust Anonymity Reputation
Business and Legal Issues Business
Models Intellectual Property Rights
Sociometry Small World Phenomena Power-Law
Networks
Network Architecture and Design Network
Topology Routing Overlay Networks
P2P
Distributed Databases Query Decomposition Query
Distribution Mediation
Distributed Data Structures Distributed Hash
Tables Scalable Distributed Data Structures
Intelligent Agents/ Web-based Services Matchmaking
Service Description
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Scalable Distributed Data Structures

• Distributed Hash Table
• Mapping idD idN so that node N contains
  document D
• Chord
• idD, idN in 0, .., n-1
• Put doc D on node N, so that idN smallest node id
  larger that idD
• Skip list node q stores pointers to q1, q2,
  q4 ..., q 2k (mod n)
• Find node for every doc in O(log(nodes)) steps
  O(log(nodes)) storage per node

SMK01
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Security and Protection Trust Anonymity Reputation
Business and Legal Issues Business
Models Intellectual Property Rights
Sociometry Small World Phenomena Power-Law
Networks
Network Architecture and Design Network
Topology Routing Overlay Networks
P2P
Distributed Databases Query Decomposition Query
Distribution Mediation
Distributed Data Structures Distributed Hash
Tables Scalable Distributed Data Structures
Intelligent Agents/ Web-based Services Matchmaking
Service Description
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Semantic Matchmaking

• Find agent that is capable of fulfilling a given
  task
• Example LARKS
• Service described by
• Context Sorting
• Input/output parameters In i list of real Out
  o list of real
• Input/output constraints len(i) lt 100,
  sorted(o)
• Text description Sorts a list of at most 100
  reals
• ...

SLKW99
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Semantic Matchmaking (II)

• Match description of wanted task against
  available agents
• Several kinds of filters, e. g.
• Similarity matching
• Test ontology-based similarity of words in
  description
• Signature matching
• Test if input and output types of descriptions
  are equal or subconcepts of each other
• Constraint matching
• Test if one set of constraints subsumes the other
  one

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Security and Protection Trust Anonymity Reputation
Business and Legal Issues Business
Models Intellectual Property Rights
Sociometry Small World Phenomena Power-Law
Networks
Network Architecture and Design Network
Topology Routing Overlay Networks
P2P
Distributed Databases Query Decomposition Query
Distribution Mediation
Distributed Data Structures Distributed Hash
Tables Scalable Distributed Data Structures
Intelligent Agents/ Web-based Services Matchmaking
Service Description
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Distributed Databases Mediation

• AMOS II
• Wrapper-Mediator Approach for Distributed DBMS
• Wrappers map data sources to common data model
• Mediators distribute queries and integrate results

AMOS II Kernel
ODBC/JDBC
Java API
Inter-AMOS
Mediator
Relational
XML
Inter-AMOS
Wrappers
ODBC
XML file
RDBMS
RJ01
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Distributed Databases (II)

• Query decomposition
• Predicate grouping
• group query predicates by node
• Predicate placement
• cost-based heuristics
• select execution node for each predicate
• Cost-based scheduling
• compute execution tree
• Tree balancing and distribution
• optimize execution tree

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Security and Protection Trust Anonymity Reputation
Business and Legal Issues Business
Models Intellectual Property Rights
Sociometry Small World Phenomena Power-Law
Networks
Network Architecture and Design Network
Topology Routing Overlay Networks
P2P
Distributed Databases Query Decomposition Query
Distribution Mediation
Distributed Data Structures Distributed Hash
Tables Scalable Distributed Data Structures
Intelligent Agents/ Web-based Services Matchmaking
Service Description
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Small-World Phenomena and Power-Law Graphs

• Milgrams six degrees of separation (1967) Its
  a small world
• Forwarding of letters from Nebraska to
  Massachusetts
• Forward message to someone closer to the target
  
• Average chain of mutual acquaintances between two
  Americans has average length 6

WS98, FFF99
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Small-World Phenomena and Power-Law Graphs (II)

• Power-Law Graphs
• Pnode has degree k for some ?gt0
• Found in many real-life situations

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Small-World Phenomena and Power-Law Graphs (III)

• Highly clustered, short paths
• short cuts long range edges
• Milgram Experiment
• High-degree nodes are crucial for short paths

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Conclusion Thesis proposal

• Semantic routing in P2P networks
• Need a way to semantically describe content of
  repositories
• I contain information about database lectures,
  KDD conferences and some machine learning stuff.
• Use semantic content description for aggregation
• My peer group is concerned with databases and
  information systems.
• Create or make use of small-world topology
• No, I dont know anything about Bluetooth, but
  that guy over there might be able to help you.

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References

• TAD02 Bernard Traversat, Mohamed Abdelaziz,
  Mike Duigou, Jean-Christophe Hugly, Eric Pouyoul,
  and Bill Yeager. Project JXTA virtual network.
  http//www.jxta.org/project/www/docs/JXTAprotocols
  .pdf, February 2002.
• CGM01 Arturo Crespo and Hector Garcia-Molina.
  Routing indices for peer-to-peer systems.
  (Submitted for publication)
• SMK01 Ion Stoica, Robert Morris, David Karger,
  M. Frans Kaashoek, and Hari Balakrishnan. Chord
  A scalable peer-to-peer lookup service for
  internet Applications. In Proceedings of the 2001
  ACM SIGCOMM, 2001.
• SLKW99 Katia Sycara, Jianguo Lu, Matthias
  Klusch, and Seth Widoff. Dynamic service
  matchmaking among agents in open information
  en-vironments. ACM SIGMOD Record, Special Issue
  on Semantic Interoperability in Global
  Information Systems, 1999.
• RJ01 Tore Risch and Vanja Josifovski.
  Distributed data integration by object-oriented
  mediator servers. Concurrency and Computation
  Practice and Experience, 13(11)933953,
  September 2001.
• WS98 Duncan J. Watts and Steven Strogatz.
  Collective dynamics of small-world networks.
  Nature, 393440442, June 1998.
• FFF99 Michalis Faloutsos, Petros Faloutsos, and
  Christos Faloutsos. On power-law relationships of
  the internet topology. In Proceedings of the
  conference on Applications, technologies,
  architectures, and protocols for computer
  communication, pages 251262, 1999.