Improving Search in P2P Networks

Improving Search inP2P Networks

Presenters: Mu, Ai Lu, Min

Date: Nov 25, 2004

25/11/04 Improving Search in P2P 2

Outline

Introduction to JXTA SearchArchitecture and ComponentsDesign GoalsQuery Routing Protocol (QRP)Query ResolutionSummary


Current P2P Search Models

Two main models of p2p networks:

The centralized Client/Server model;

The decentralized model.


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Client receive outdated info because central server index is only updated periodically.


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.


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.


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.


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)


Wide search of distributed devices, such as PCs, PDAs, and cell phones.

Deep search of rich content sources such as Web servers.

JXTA Search


Outline



The JXTA Search Network architecture consists of the following

components:

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

Architecture and Components


JXTA Search Hub Service

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 Hub Service consists of the two sub components:

Router , ResolverAt the heart of JXTA Search is the "router/resolver"

JXTA Search Router

- routes and manages query connections, - collates results and returns results to consumers


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.


Outline



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.


OutlineIntroduction to JXTA SearchArchitecture and ComponentsDesign GoalsQuery Routing Protocol (QRP)

Query ResolutionSummary

Query MessagesResponse MessagesRegistration Messages


Query Routing Protocol (QRP)

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


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.


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 <request>...</request>.

The query unique ID is specified in the uuid attribute of the <request> 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 <query> to specify the start of the actual query data and the tag <text> to specify free text, or within any other namespace specified by the query-space definition.

E.g. a query for books on Java<?xml version='1.0'?><request xmlns=http://search.jxta.org mlns:b=http://www.sellbooks.com/JxtaSearch

query-uuid=1C8DAC3036A811D584AEC2C23

query-space=http://www.sellbooks.com/JxtaSearch> <query>

<b:author> Bill Joy</b:author><b:title> Java</b:title>

</query></request>


QRP - Response MessagesThe response message is structured as follows:The default name space is http://search.jxta.org.The response message is enveloped within the <responses>...</responses> tags, with each specific response enveloped in <response>...</response> tags. The body of the response is contained within the <data>...</data> tags. It can be arbitrary well-formedXML.

<?xml version='1.0'?><responses xmlns=http://search.jxta.org xmlns:b=http://www.sellbooks.com/JxtaSearch query-uuid=1C8DAC3036A811D584AEC2C23> <response> <data> <b:authors>Bill Joy, Guy Steel</b:authors> <b:URL> http://www.sellbooks.com/0201310082 </b:URL> <b:title>The Java Language Specification, Second Edition

</b:title> <b:price>$39.95</b:price> </data> </response></responses>


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 provider’s 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 provider’s query server endpoint is either a JXTA pipe ID or a URL. Queries which match one of the provider’s predicates are posted to this endpoint.


QRP - Registration Messages

The query server

The predicate body

The query space

?xml version=’1.0’?><register xmlns="http://search.jxta.org" xmlns:b= http://www.sellbooks.com/JxtaSearch > <query-server>http://www.sellbooks.com/exec/jxtasearch.pl </query-server> <query-space uri= www.sellbooks.com/JxtaSearch> <predicate> <query> <b:author> <quote>Bill Joy</quote><quote>Guy Steel</quote> </b:author> <b:title>The Java Language Specification, Second Edition</b:title> </query> </predicate> </query-space></register>


Outline



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.


Query Resolution

Provide an efficient query resolution and routing service.

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.

Define a framework for providers to register the type of queries they are

interested in.

Method 1 Method 2


Outline



JXTA Advantages Simplicity & Robustness JXTA defines a simple & lean framework for P2P applications.

Defers complex implementation details to implementing applications.

Interoperability & UbiquityAllows 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


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.

JXTA Disadvantages


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.


The End

Thank you!

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Improving Search in P2P Networks