Grid and P2P are the two important resource sharing systems at present. Grid systems are applied in some large scientific computing centers in order to make full use of the shared resources, such as computer CPUs, storage, data, software and instruments. Grid systems are usually organized centrally or hierarchically in order to administrate the participating resources effectively [1].

Although, P2P and grid have many common characteristics such as dynamic behavior and heterogeneity of the involved resources, P2P and grid systems exhibit essential differences. Grids employ relative concentration and distributed resource administrative strategy in order to allow access to all of the resources shared on the network. Grids are trusted in the heterogeneous environment, as a special resource sharing model, users have high security, confidentiality and reliability, but do not solve the issue that nodes randomly join and live.

The emergence of fast wide-area networks has moved distributed computing to a new area in which distributed resources in a wide-area network are more closely coupled to provide a single integrated platform for computing and data storage. Well-known examples are Grid computing and peer-to-peer networks, which harness the computing power of hosts in a network and make their under-utilized resources available to users.

Informally, peer-to-peer systems can be described to be distributed systems in which all nodes are peers in the sense that they have equal roles and responsibilities. The nodes in the distributed system have identical capabilities and responsibilities, and all communication is symmetric. Peer-to-peer systems are characterized by decentralized control, large scale, and extreme dynamics of their operating environment. Peer-to-peer systems are used for file-sharing (i.e., exchanging files between peers) and file-storage (i.e., the peer-to-peer network is used as a distributed file system) [2, 3].The peer-to-peer networks can also be used to harness the computing power of hosts in a network, similar to SETI@home or more elaborate systems like Condor [4] and Grid computing environments [5].

I. P2P NETWORKING PARADIGM

The two primary types of network architecture are client-server and peer-to-peer networks. In client-server networks, a central server handles all security and file transactions while in peer-to-peer networks; each machine shares its own resources and handles its own security. The comparison of client-server and peer-to-peer architecture models is given as fig.1

Fig.1 Client-server and peer-to-peer Model

The primary advantage of P2P networks is that all clients contribute and share their own resources and all peers are both users and providers of resources. Hence in comparison to client–server networks, P2P networks are more robust and scalable as there are no central authorities or servers. The P2P overlay network consists of all the participating peers as network nodes. There are communication links between any two nodes that know each other: i.e. if a participating peer knows the location of another peer in the P2P network, then there is a directed edge from the former node to the latter in the overlay network. Based on how the nodes in the overlay network are linked to each other, we can classify the P2P networks as unstructured or structured.

A. UNSTRUCTURED OVERLAYS

An unstructured overlay is an overlay in which a node relies only on its adjacent nodes for delivery of messages to other nodes in the overlay. Example message propagation strategies are flooding and random walk [6]. Unstructured P2P systems do not maintain network structure and establish links arbitrarily. Unstructured overlay designs of P2P systems include Freenet, Gnutella, Fast Track, Fast Freenet, and Local Minima Search (LMS).

B. STRUCTURED OVERLAYS

Structured Overlay is an architecture in which nodes cooperatively maintain routing information about how to reach all nodes in the overlay [7]. Structured overlay networks let the set of cooperating peers act as a distributed data structure with well-defined operations.

II. GRID COMPUTING PARADIGM

A. ARTCHITECTURE

Grids started off in the mid-90s to address large-scale computation problems using a network of resource-sharing commodity machines that deliver the computation power affordable only by supercomputers and large dedicated clusters at that time. The major motivation was that these high performance computing resources were expensive and hard to get access to, so the starting point was to use federated resources that could comprise compute, storage and network resources from multiple geographically distributed institutions, and such resources are generally heterogeneous and dynamic. Grids focused on integrating existing resources with their hardware, operating systems, local resource management, and security infrastructure.

Grids provide protocols and services at five different layers as identified in the Grid protocol architecture as in Figure 2.

The fabric layer, Grids provide access to different resource types such as compute, storage and network resource, code repository, etc. Grids usually rely on existing fabric components, for instance, local resource managers (i.e. PBS [8], Condor [9], etc).

Fig.2 Grid Protocol Architecture

The connectivity layer defines core communication and authentication protocols for easy and secure network transactions. The GSI (Grid Security Infrastructure) [10] protocol underlies every Grid transaction.

The resource layer defines protocols for the publication, discovery, negotiation, monitoring, accounting and payment of sharing operations on individual resources. The GRAM (Grid Resource Access and Management) [11] protocol is used for allocation of computational resources and for monitoring and control of computation on those resources, and GridFTP [13] for data access and high-speed data transfer.

The collective layer captures interactions across collections of resources, directory services such as MDS (Monitoring and Discovery Service) [12] allows for the monitoring and discovery of VO resources, Condor-G [14] and Nimrod-G [15] are examples of co-allocating, scheduling and brokering services, and MPICH [16] for Grid enabled programming systems, and CAS (community authorization service) for global resource policies.

The application layer comprises whatever user applications built on top of the above protocols and APIs and operate in VO environments. Two examples are Grid workflow systems and Grid portals (i.e. QuarkNet e-learning environment [17], National Virtual Observatory (http://www.us-vo.org), TeraGrid Science gateway http://www.teragrid.org).

III. RELATED WORKS

The integration of P2P technology and grids improves the dynamicity and the scalability of the grid, enhances the security of P2P, and eventually solves the issue of the large-scale distributed, heterogeneous, dynamic resource sharing. It is thus reasonable to combine grid and P2P to build a large scale, highly dynamic knowledge repository which provides several ways to discover the resources.

A. COMPARING GRIDS AND P2P

Current Grids provide many services to moderate-sized communities [18] and emphasize the integration of substantial resources to deliver nontrivial qualities of service within an environment of at least limited trust. For example, NASA’s Information Power Grid links supercomputers at four NASA laboratories [19]. In contrast, current P2P systems deal with many more participants (e.g., Limewire [20] reports hundreds of thousands in Gnutella) but offer limited and specialized services, have been less concerned with qualities of service, and have made few if any

assumptions about trust.

a) RESOURCES

In general, Grid systems integrate resources that are more powerful, more diverse, and better connected than the typical P2P resource. A Grid resource might be a cluster, storage system, database, or scientific instrument of considerable value that is administered in an organized fashion according to some well-defined policy. This explicit administration enhances the resource’s ability to deliver desired qualities of service and can facilitate, for example, software upgrades, but it can also increase the cost of integrating the resource into a Grid. Diversity in architecture and policy makes the publication of resource properties important [21]. Explicit administration, higher cost of membership, and the stronger community links within scientific VOs mean that Grids integrate not only high-end. Resources: desktop systems with variable availability form a major component of many contemporary Grids. However, the ensembles of all such resources within a Grid are not treated as an undifferentiated swarm of global scope. Rather, they are aggregated within administrative domains via technologies such as Condor to create local resource pools that are integrated into larger Grids via the same Grid protocols as other computational resources.

b) SERVICES AND INFRASTRUCTURE

Many Grid communities use the open source Globus Toolkit [20] as a technology base. Significant effort has been channeled toward the standardization of protocols and interfaces to enable interoperability between different Grid deployments. The Open Grid Services Architecture (OGSA)[22] is such an effort: it integrates Grid and Web services technologies to define a service-oriented architecture

P2P systems have tended to focus on the integration of simple resources (individual computers) via protocols designed to provide specific vertically integrated functionality. Thus, for example, Gnutella defines its own protocols for search and network maintenance.

Finally, the summarization of above comparative and contrast over peer to peer and grids are as below table no.1:

Table 1

Feature	Grid Computing	Peer-to-peer
Organization	any	Peers (by definition)
Main purpose	Resource Sharing · Computation · Storage · Data	Content Sharing · Data
Core Enabling Technology	Resource Virtualization	Distributed data search and retrieval
Expectations for security/reliability	Medium/Medium	Low/Low
Sophistication of implementers /user	High/Medium	Low/Low
Access requirements	Read/Write/Execute	Read
Standardization	Formal process led by the Global Grid Forum (GGF)	De-facto standards from successful software , some movement
Feature	Grid Computing	Peer-to-peer
Commercialisation · Of enabling technology · Of resource usages	Underway · Many companies · Some	Problematic · Limited · Failed

IV. CONCLUSION:

Peer to Peer grid technology has proven that it is the best technology to work over the internet on commerce, businesses, educations, science, researches, and many other projects by eliminating the geographical and economical limitations of the resources. Since P2P and Grid computing are both designed to fulfill the same objective for harnessing and applying various resources across various organizations it will be more useful if both technologies can be merged together to have absolute and optimal benefits. This survey will help people understand the potential benefits of P2P Grid in the research community and industry.

V. REFERENCES:

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Received on 15.02.2013 Accepted on 01.03.2013

Research J. Science and Tech 5(3): July- Sept., 2013 page 291-294