Locating Equivalent Servants over P2P Networks

Abstract:-

While peer-to-peer networks are mainly used tolocate unique resources across the Internet, new interestingdeployment scenarios are emerging. Particularly, some applications(e.g., VoIP) are proposing the creation of overlays for thelocalization of services based on equivalent servants (e.g., voicerelays).

This paper explores the possible overlay architecturesthat can be adopted to provide such services, showing how anunstructured solution based on a scale-free overlay topologyis an effective option to deploy in this context. Consequently,we propose EQUATOR (Equivalentservantlocator), an unstructuredoverlay implementing the above mentioned operatingprinciples, based on an overlay construction algorithm that wellapproximates an ideal scale-free construction model.

We presentboth analytical and simulation results which support our overlaytopology selection and validate the proposed architecture.

Pure peer-to-peer:

• Peers act as equals, merging the roles of clients and server

• There is no central server managing the network

• There is no central router

Algorithm

Epidemic dissemination algorithm

Overlay construction algorithm

Detail Algorithm Explanation

An interesting lookup solution that avoids the deleterioustraffic overhead generated by flooding-based queries is theadoption of a service lookup based on random walks encompassing a bounded number of nodes. Within this technique,the service request is forwarded, at each node, to a peerrandomly selected among its neighbors. If the encounterednode is available or knows an available servant, the procedureterminates. The knowledge of nodes can be improved through

Proper advertisement messages containing the node itselfand/or other participating peers, thus implementing a so calledepidemic dissemination algorithm

Architecture

Existing System

Existing works lack in providing adequate support to theseemerging distributed systems In fact, most of them focuson the development of a system supporting specific requests, previous work explores the ideaof a service based on it limit equivalent servants,

Disadvantages

Existing cant implemented feature of scale-free networks, Network size grows

Proposed System

This Project focuses on services provided by equivalent servantsand models and analyzes the performance of structuredand unstructured overlays when used to provide such services.We demonstrate that the architecture chosen for the P2Pnetwork has a huge impact on the overall performance ofthe service. In particular, with the support of some analyticaland simulation results, we show how an unstructured networkbased on epidemic dissemination and built over a scale-freeoverlay topology is an effective solution to deploy in thiscontext.

Advantages

  • Peer-to-peer computing takes advantage of existing desktop computing power and networking connectivity, allowing economical clients to leverage their collective power to benefit the entire enterprise
  • Large number of participating servants and user’s single entity directly handles all possibleservants and consequently offers the best performance

Implemented Modules

1. Peer to peer equivalent servants

The equivalence of servants is considered in; propose a scheme for CPU cycle sharing overan unstructured P2P network. They consider the unbalanced node degree distribution, which may result in real overlay networks, as a possible obstacle to the lookup effectiveness of the system and, consequently, they propose mechanisms to overcome these limitations...

2.Structured DHT based P2P Overlays

Structured - Overlay network topology is tightly controlled and content are placed not at random peers but at specified locations that will make subsequent queries more efficient.

Uses Distributed Hash Table (DHT) as a substrate,

data object (or value) location information is placed deterministically, at the peers with identifiers corresponding to the data object’s unique key.

Examples – CAN, Chord, Pastry, Tapestry

Data objects are assigned unique identifiers called keys, chosen from the same identifier space.

Keys are mapped by the overlay network protocol to a unique live peer in the overlay network.

The P2P overlay supports the scalable storage and retrieval of {key,value}pairs on the overlay network,

Each peer maintains a small routing table consisting of its “neighboring” peers’ Node IDs and IP addresses

3. Unstructured P2P Overlay Networks

System composed of peers joining the network with some loose rules, without any prior knowledge of the topology.

Network uses flooding or random walks as the mechanism to send queries across the overlay with a limited scope.

When a peer receives the flood query, it sends a list of all content matching the query to the originating peer

Examples – FreeNet, Gnutella,KaZaA, BitTorrent

Structured Overlays

We introduce an additionalfeature to this querying mechanism: during the lookup process,any node encountered along the path is checked for availabilityand can be selected as a servant for the querying user. Noticethat this operating mode makes the approach independent ofthe adopted DHT.

Unstructured Overlays

An efficient unstructured overlay is characterized by highlookup performance and small amount of traffic required tomaintain the overlay.

3. Peer join/Leave

•Each file has a hash and a descriptor

•Client sends keyword query to its group leader

•Group leader(super peer) responds with matches:

–For each match: metadata, hash, IP address

•If group leader forwards query to other group leaders, they respond with matches

•Client then selects files for downloading

–HTTP requests using hash as identifier sent to peers holding desired file

4. DHTequivalent servants

DHT(Dynamic Hash Table) introduce an additionalfeature to this querying mechanism: during the lookup process,any node encountered along the path is checked for availabilityand can be selected as a servant for the querying user. Noticethat this operating mode makes the approach independent ofthe adopted DHT. In fact, only the overlay topology (which isa regular graph in existing DHTs) is of interest in our context.In other words, we adopt the topology of a generic DHT, with afixed number of neighbors for each node, but we use a differentrouting mechanism.

The idea of using a DHT for our scenario of equivalentservants is especially interesting in case a DHT has to beimplemented anyway for some other services. For example,P2PSIP already uses a structured overlay to index all possibletargets of a multimedia communication, i.e., all the user agentsregistered in the SIP domain. Using the same DHT to locate,if necessary, a relay node to support the communication (i.e.,a servant among the many peers existing in the SIP domain)may be a considerable advantage for that application, whichneeds to maintain only one overlay structure that can be usedfor both functions.

5. DHT Equator Simulationequivalent servants

In EQUATOR, we prefer a more flexible approach that relieson multiple

Bootstrap reachable through appropriateDNS records thus guaranteeing redundancyand load balancing. Bootstrap servers globally storeinformation about m0 participating peers; when a peer joins the overlay. it adds we proposed the Equivalent servant locator (EQUATOR) architecture, which overcomes the issues related to the deployment of a scale-free topology for service location in a real network, mainly due to the static nature of the ideal scale-free construction algorithm and the lack of a global knowledge of the participating peers. Simulation results confirmed the effectiveness of EQUATOR, showing how it offers good lookup performance in conjunction with low message overhead and high resiliency to node churn and failures.

System Requirements:

Hardware Requirements:

•System: Pentium IV 2.4 GHz.

•Hard Disk: 40 GB.

•Floppy Drive: 1.44 Mb.

•Monitor: 15 VGA Colour.

•Mouse: Logitech.

•Ram: 256 Mb.

Software Requirements:

•Operating system :- Windows XP Professional

•JDK :-1.5/ 1.6 and above

•Front End :- JAVA, Swing(JFC),

•Database :MS-Access

• Tool :Eclipse 3.3