Client Server Systems
This system has a dominant computer that is the Server and has software running on it and is connected to various Clients that have limited functionality. The client requests for services to the Server. Examples of this are Windows NT and Novell NetWare. Network services like printing and electronic mail are routed through the file server, which allows networking tasks to be tracked. . A Network Operating System, or NOS, is installed onto each PC that requires network access. The NOS is a regulatory measure that monitors the exchange and flow of information. Servers store databases, files, programs and more that are shared across the network with clients. This architecture allows access to data, information and resources company wide. Applications consist of three tiers: Presentation (the User Interface), Business Logic, and Data (the Database). Client/server computing splits the application tasks and puts them on the platform where it can be handled most efficiently. This is by far the most popular model for various business purposes.
Message Oriented Middleware: http://www.sei.cmu.edu/str/descriptions/momt_body.html
P2P Systems are decentralized networks and does not have a single computer like a Server that is dominant over any other computer. Each computer (node) determines which resources it will share with the network and to what degree it will share those resources. For example, one user on the network might choose to allow their hard drive to be shared in a 'read only' manner, while another user may allow 'full access' and still another might disallow access to some or all of the files on their drive. Additionally, in a peer-to-peer configuration, no one computer can override any of the others to force them to change their settings. They are easy to set up, less expensive than client server networks, and its own operator individually maintains each computer. Most network operating system software (such as Windows 95 and Windows 98) allows each peer-to-peer computer to determine which resources will be available for use by all other users of the remaining computers on the network. Specific hard and floppy disk drives, directories, files, printers, and all other resources can be attached or detached from the network via software.
Characteristics of Peer Computing
After looking at what P2P systems are, let us look at some of the characteristics of P2P systems. There are some distinguishing characteristics that make P2P systems different from other systems, the crux of which are:
· The location of a file is not known by its retriever, perhaps not even after the file is retrieved. So there is no concept of a hooking to a server to get some services done.
· Files move freely among systems, they can show up on some systems and disappear unexpectedly. Large numbers of people request content from a global system rather than from a particular host.
· Have an operational computer of server quality, since each node acts as a client and a server.
· An addressing system which is independent of the DNS.
· The ability to cope with variable connectivity.
Some of the requirements to have a P2P system running are the following:
· Standard communication protocols are required.
· Information exchange should be secure.
· Information networks should support policy-based authorization.
· Information networks should facilitate more effective search.
· Information networks should be easy to use and set up.
· Information networks should scale.
· Information networks should be ubiquitous.
Advantages of P2P over CS
Empowers the users, and has very little
New P2P technology is emerging on the edge of the Internet. The web is full of useful information. However, “often times the most urgent and personally relevant content – music, photos, work files, drafts and works-in-progress, calendars and schedules – are found on desktops of individuals beyond the reach of any centralized or web-based search engine” (Grove).
P2P popularity is growing among end users, technologists and business people. The appeal includes personal control, context, security, flexibility, cost effectiveness, and speed. The user has direct access and control by actually moving content directly onto his machine. The difference between this process and a web page is the difference between “having” and “viewing"
P2P allows people to go beyond sharing and swapping, “to talking with each other about the content. In this way, an intuitive and shared context emerges from the marriage of content and activity”
Both CS and P2P in my opinion will survive for a long time to come; though the P2P is moving at a rapid pace.
Nodes on this form are peers i.e can act as clients and servers and have the same capability as its neighbors. It has no central servers. It has every node as a Peer and has no central router. Further there are two routing structures, one which is a distributed catalogue and the other direct messaging. There is equality among nodes. Exapmle: Gnutella, Freenet.
The central server is responsible for maintaining a registry of shared information and responding to queries for that information. The peers are responsible for hosting the information, communicating what is to be shared to the central server, and downloading it to other peers upon request. This is centralized but not in the conventional Client Server sense. Route terminals are used to hold catalogues of addresses. They are referenced by a set of indexes that determine ab address set. Example: Napster
The Pure and Hybrid forms are extremes, the Mixed is a middle ground that involved the server as well as gives the peers adequate independence.
The VPC can be structured hierarchically. Queries are generally routed only within a community. Queries may pass between communities where one peer acts as a gateway by being a member of both communities. Only members of a particular community may decipher queries for that community. Information sharing is restricted to members of the community. Communities can be created within communities in order to provide for more specialized information sharing.