Improving Search in P2P Networks

1. Improving Search inP2P Networks Presenters: Mu, Ai Lu, Min Date: Nov 25, 2004

2. Outline • Introduction to JXTA Search • Architecture and Components • Design Goals • Query Routing Protocol (QRP) • Query Resolution • Summary Improving Search in P2P

3. Current P2P Search Models Two main models of p2p networks: • The centralized Client/Server model; • The decentralized model. Improving Search in P2P

4. 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quickly and efficiently; • A single point of failure and a visible target for attack on the network; • Client receive outdated info because central server index is only updated periodically. Improving Search in P2P

5. 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. Searching Decentralized Network Improving Search in P2P

6. 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. Improving Search in P2P

7. 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. Improving Search in P2P

8. 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) Improving Search in P2P

9. JXTA Search Wide search of distributed devices, such as PCs, PDAs, and cell phones. Deep search of rich content sources such as Web servers. Improving Search in P2P

10. Outline • Introduction to JXTA Search • Architecture and Components • Design Goals • Query Routing Protocol (QRP) • Query Resolution • Summary Improving Search in P2P

11. Architectureand Components The JXTA Search Network architecture consists of the following components: • Registration Service • Provider Service • Consumer Service • Hub Service Improving Search in P2P

12. 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 Router • routes and manages query connections, • collates results and returns results to consumers 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. Improving Search in P2P

13. 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. Improving Search in P2P

14. Outline • Introduction to JXTA Search • Architecture and Components • Design Goals • Query Routing Protocol (QRP) • Query Resolution • Summary Improving Search in P2P

15. 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. Improving Search in P2P

16. Query Messages Response Messages Registration Messages Outline Introduction to JXTA Search Architecture and Components Design Goals Query Routing Protocol (QRP) Query Resolution Summary Improving Search in P2P

17. Query Routing Protocol (QRP) QRP defines mechanisms for sending, responding queries as well as meta-data for nodes in the network. Improving Search in P2P

18. 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. Improving Search in P2P

19. 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. Improving Search in P2P

20. 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 <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-formed XML. Improving Search in P2P

21. QRP - Registration Messages • Information providers must register with the JXTA Search network. • To register, a provider contacts an access pointwith 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 theprovider’s predicates are posted to this endpoint. Improving Search in P2P

22. QRP - Registration Messages The query server The query space The predicate body Improving Search in P2P

23. Outline • Introduction to JXTA Search • Architecture and Components • Design Goals • Query Routing Protocol (QRP) • Query Resolution • Summary Improving Search in P2P

24. Query Resolution • Queries are resolved by a resolverby 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. Improving Search in P2P

25. 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 Define a framework for providers to register the type of queries they are interested in. Provide an efficient query resolution and routing service. Improving Search in P2P

26. Outline • Introduction to JXTA Search • Architecture and Components • Design Goals • Query Routing Protocol (QRP) • Query Resolution • Summary Improving Search in P2P

27. 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 Improving Search in P2P

28. 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. Improving Search in P2P

29. 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. Improving Search in P2P

30. The End Thank you! Improving Search in P2P