Improving Search in P2P Networks

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Improving Search inP2P Networks

• Presenters Mu, Ai
• Lu, Min
• Date Nov 25, 2004

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Outline

• Introduction to JXTA Search
• Architecture and Components
• Design Goals
• Query Routing Protocol (QRP)
• Query Resolution
• Summary

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Current P2P Search Models

• Two main models of p2p networks
• The centralized Client/Server model
• The decentralized model.

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Searching Centralized Networks

• The central index which locates files quickly and
  efficiently
• A single point of failure and a visible target
  for attack on the network
• Client receive outdated info because central
  server index is only updated periodically.

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Searching Decentralized Network

• Remove the central structure of the network
• Searching a decentralized network is slower
• Not guarantee to find a file even if it is on the
  network because the TTL (time to live) expires.

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Why JXTA Search?

• Most Web content is invisible to current search
  engines
• JXTA Search address this problem, providing a
  unique query routing protocol that makes content
  visible and facilitates its use.

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Introduction JXTA

• Originally developed by Sun
• JXTA is a set of open, generalized peer-to-peer
  (P2P) protocols that allow any connected device
  on the network from cell phone to PDA, from PC
  to server to communicate and collaborate as
  peers
• The JXTA protocols are independent of any
  programming language, and multiple
  implementations exist.

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JXTA Search

• JXTA Search is a decentralized p2p search engine.
• Defines a XML-Protocol (QRP), which enables the
  search in P2P Network.
• Supports both Wide Search and Deep Search.
• Open source code (http//search.jxta.org)

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JXTA Search
Wide search of distributed devices, such as PCs,
PDAs, and cell phones. Deep search of rich
content sources such as Web servers.
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Outline

• Introduction to JXTA Search
• Architecture and Components
• Design Goals
• Query Routing Protocol (QRP)
• Query Resolution
• Summary

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Architecture and Components
The JXTA Search Network architecture consists of
the following components

• Registration Service
• Provider Service
• Consumer Service
• Hub Service

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JXTA Search Hub Service
JXTA Search Hub Service consists of the two sub
components Router , Resolver At the heart of
JXTA Search is the "router/resolver"
JXTA Search Resolver - maintains an index of
provider's registrations, - and when a query is
received, matches the query against a set of
providers that may be good at answering the
query.

• JXTA Search Router
• routes and manages query
• connections,
• collates results and returns
• results to consumers

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Architecture

• Distributed Search
• Central to the JXTA Search infrastructure are
  "hubs".
• Each hub has a series of providers that form its
  local network.
• These providers typically have something in
  common.
• Hubs are expected to become an efficient way to
  group peers with similar content, or geography.

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Outline

• Introduction to JXTA Search
• Architecture and Components
• Design Goals
• Query Routing Protocol (QRP)
• Query Resolution
• Summary

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Design Goals

• Simplicity any client and server can be
  incorporated
• Structure all queries to the JXTA Search Network
  are XML messages conforming to a queryspace in
  which providers register templates describing the
  structure of queries they can accept
• Extensibility arbitrary queryspaces can be used
• Scalability peer can dynamically join the
  network for sending the registration message.

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Outline

• Introduction to JXTA Search
• Architecture and Components
• Design Goals
• Query Routing Protocol (QRP)
• Query Resolution
• Summary

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Query Routing Protocol (QRP)

• QRP defines mechanisms for sending, responding
  queries as well as meta-data for nodes in the
  network.

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Queryspaces

• Providers may have widely different types of
  content or resources in their datastores.
• The notion of queryspaces is allowed to define
  the structure of a query and its associated
  registration.
• Queryspaces are a fundamental component of the
  JXTA Search framework. Like XML namespaces,
  queryspaces do not necessarily reference to the
  actual content, they are simply identifiers used
  by providers and consumers to find each other.

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QRP - Query Messages

• Query messages are structured as follows
• The default namespace is http//search.jxta.org
• The query message is contained within the
  envelope ltrequestgt...lt/requestgt.
• The query unique ID is specified in the uuid
  attribute of the ltrequestgt tag.
• The query space is specified in the query-space
  attribute of the request tag.
• The query data can be arbitrary XML within a
  namespace. It includes the tag ltquerygt to specify
  the start of the actual query data and the tag
  lttextgt to specify free text, or within any other
  namespace specified by the query-space
  definition.

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QRP - Response Messages

• The response message is structured as follows
• The default name space is http//search.jxta.org.
• The response message is enveloped within the
  ltresponsesgt...lt/responsesgt tags, with each
  specific response enveloped in ltresponsegt...lt/resp
  onsegt tags.
• The body of the response is contained within the
  ltdatagt...lt/datagt tags. It can be arbitrary
  well-formed
• XML.

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QRP - Registration Messages

• Information providers must register with the JXTA
  Search network.
• To register, a provider contacts an access point
  with a registration message.
• An XML document with three components
• Queryspace URL identifies the URL at which, when
  queries are posted to it, the providers
  predicates are checked for matches.
• A set of predicatesThe predicate defines the
  structure and content of the queries which the
  provider is interested in.
• The providers query server endpoint is either a
  JXTA pipe ID or a URL. Queries which match one of
  the providers predicates are posted to this
  endpoint.

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QRP - Registration Messages
The query server
The query space
The predicate body
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Outline

• Introduction to JXTA Search
• Architecture and Components
• Design Goals
• Query Routing Protocol (QRP)
• Query Resolution
• Summary

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Query Resolution

• Queries are resolved by a resolver by matching
  query terms to registration terms. Providers
  whose registration terms match the query terms
  are returned by the resolver.
• The minimal condition for matching a query to a
  provider is that the query must have the same
  query-space as the provider registration.

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Query Resolution
To determine to which set of providers a given
query should be routed. Sending all queries to
all providers is inefficient. JXTA Search
attempts great efficiency.
Method 1
Method 2
Provide an efficient query resolution and routing
service.
Define a framework for providers to register the
type of queries they are interested in.
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Outline

• Introduction to JXTA Search
• Architecture and Components
• Design Goals
• Query Routing Protocol (QRP)
• Query Resolution
• Summary

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JXTA Advantages

• Simplicity Robustness
• JXTA defines a simple lean framework for
  P2P applications. Defers complex implementation
  details to implementing applications.
• Interoperability Ubiquity
• Allows a wide range of peers such as sensors,
  PDAs appliances, network routers, desktop
  computers, data-center servers and storage
  systems to interact with one another.
• Language Platform independence
• Clear-cut distinction between policies and
  mechanisms
• To keep the core small and elegant, there is an
  architectural distinction between core mechanisms
  and optional policies.
• Flexibility Implementation Incremental
  Improvement
• Openness Open source is available at
  http//search.jxta.org

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JXTA Disadvantages

• Heavy Applications
• JXTA implements minimal P2P infrastructure and
  leaves several issues for applications to
  address.
• Example reliable end to end communication on
  top of an unreliable transport
• Security Trust models
• To date JXTA relies heavily on credentials
  and digests for authentication protection.
  Applications are required to implement their
  security models. Trustability of peers.

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Summary

• A novel approach for query routing in distributed
  networks.
• Using a simple XML protocol combined with
  powerful but simple indexing matching engines.
• Provides developers with the capability to
  connect multiple consumer and provider
  applications together for the purposes of
  information discovery and exchange.

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The End

• Thank you!