homework

meda_5800_p2p_vs.pdf

MEDA 5800 P2P vs. Client Server 7/2011 Basic Networking. Most simply put, a network is an interconnection of computers so that they may share resources among them, such as printers, files, and disk drives. In any network there are 'clients' and 'servers.' A client is a computer which utilizes one or more resources being made available to it by a server computer located on the same network. A server is a computer which provides a resource for other computers (i.e., the clients) to access. You probably have heard the terms 'peer-‐to-‐peer' and 'client-‐server' in reference to common types of networks. The differences between these types is important to understand. In a peer-‐to-‐peer network, which is often functionally limited to a handful of computers, each computer often serves as both a 'client' and 'server.' Let's say computer A has a color inkjet printer directly connected to it, and computer B has a black and white laser printer directly connected. Computer A is configured to allow Computer B to print to the color printer, and at the same time Computer B is configured to allow Computer A to print to the laser printer. Computer A is a client when its user sends a print job to Computer B's laser printer, while Computer B acts as a server in that scenario. Conversely, Computer B becomes the client when its user sends a print job to Computer A, and Computer A then plays the role of server. As you can readily see in this example, both Computer A and Computer B wear both the 'client' and 'server' hats. This is typical of a peer-‐to-‐peer networking configuration.

Network: An interconnection of computers for access to sharable resources. Client: A computer which utilizes a resource being made available to it by another computer on a network. Server: A computer which makes one or more resources available to client computers on a network. A server may be a specially-‐designed high-‐end computer, or it may simply be a typical desktop machine. Resource: Any utility provided on a computer which is recognizable and useful to one or more other computers on a network. Typically, printers, files, programs, hard disk space, and the like. Peer-to-peer Network: A network wherein the computers play the role of both client and server from time to time

In the diagram above, computer A is a client of computer B (to use B's printer) and a server to B at the same time (to allow B to use A's printer). The same is true of computer A. This is standard peer-‐to-‐peer networking.

Client-Server vs. Peer-to-Peer In a client-‐server network architecture, however, certain computers are designated for full-‐time server duty, while others (such as user workstations) are full-‐ time clients. For example, a file server will house hard

Client-Server Network: A network wherein certain computers act as dedicated providers of resources to some number of full-‐time client computers.

drives containing files that all network users can access from their personal workstations. After working on a file, the user can then save the changes back to the server for safekeeping and collaboration. Another example would be a server set up as a dedicated 'post office' for an entire organization, collecting everyone's email from outside sources for internal distribution and serving as the transporter for all outgoing email. In this case each user's computer would be a client of the mail server. Both Peer-‐to-‐peer and Client-‐server network architectures have their advantages and disadvantages. On balance, however, a Client-‐server configuration is preferable to peer-‐to-‐peer, especially in a small business environment where there is an expectation of growth. The upside of the Peer-‐to-‐peer is that it is relatively inexpensive and fairly simple to set up and manage. The flip side is that it is limited in extensibility, tends to overburden user workstations by having them play the role of server to other users, is largely unsecured, and is typically unable to provide system-‐wide services since the typical workstation will run a standard desktop operating system incapable of hosting any major service (e.g., a post office). The upside of the Client-‐server is that it can extend to handle organizational growth, allows user workstations to function as unburdened clients, can provide sophisticated system-‐wide services, and is configurable for maximum security. The downside is obvious: higher initial capital investment to establish, and a greater level of technology expertise required to configure and manage, as compared to the vanilla peer-‐to-‐peer network. Which to pick? A peer-‐to-‐peer network is often a reasonable choice in a home network, or other environment where significant growth in numbers of users or quantity of computer-‐based work is not expected, where security is not a serious concern, and where there is little or no need for major system-‐wide services.

The client-‐server architecture is usually the correct

File Server: A computer, typically higher-‐end than a workstation, which is dedicated to the task of providing file storage and file access for workstation users. Mail Server: A computer, typically higher-‐end than a workstation, which is dedicated to the task of collecting email for an organization from other mail servers on the Internet and distributing it to user mailboxes for viewing in an email client program. This server also serves as the transport agent for collecting organizational outgoing email and distributing across the internet. Extensibility: For example, the capability of a network architecture to expand to meet increased numbers of users and provide expanded levels of service as an organization increases in size and scope of work. Network Security: The ability of a network operating system to provide different schema, based on a maintained database of users and groups of users, where individual users and groups can be assigned varying levels of rights and permissions to access files and other resources. Typically minimal in a peer-‐to-‐peer architecture, yet more robust in a client-‐server configuration where a robust operating system, such as Windows NT Server, is deployed.

choice, even in a small business, where growth is anticipated, security matters, and sophisticated server-‐based services will be beneficial to productivity. Peer to Peer Network Client Server Network Advantages Advantages Allows two or PCs to pool their resources together.

Centralized -‐ Resources and data security are controlled through the server.

Can be built with both 10BaseT cabling and a hub or with a thin coax backbone.

Network access speeds are usually faster than those found on peer-‐to-‐peer networks.

Drives can be easily shared between peer-‐to-‐peer PCs.

Interoperability -‐ All components (client/network/server) work together.

Applications only need to be installed on one computer.

Flexibility -‐ New technology can be easily integrated into system.

Reduced cost (the costs involved in such a network are hardware, cabling and maintenance.

It’s more secure because if a client wants to communicate with another client he/she has to message to he/she and then it will first sent to the file server, where it is then routed to its destination.

Well tested simplicity. Scalability -‐ Any or all elements can be replaced individually as needs increase.

Setup -‐ An operating system (such as Windows XP) already in place may only need to be reconfigured for peer-‐to-‐peer operations.

Accessibility -‐ Server can be accessed remotely and across multiple platforms.

Less initial expense -‐ No need for a dedicated server.

Peer-‐to-‐peer is, by far the easiest type of network to build for either home or office use.

Each computer can make backup copies of its data to other computers for security.

Network is fast and inexpensive to setup and maintain.

Disadvantages Disadvantages

Lack of security -‐ They are less secure than client-‐server networks, especially so because the files have to shared and no password is

Can cause network congestion by adding more users

required. No computer in the network is reliable

Higher than anticipated costs

This system is not centralized, making administration difficult.

Maintenance -‐ Large networks will require a staff to ensure efficient operation

It is more time consuming to maintain the software on individual computers

Dependence -‐ When server goes down, operations will cease across the network

Peer-‐to-‐peer networks are designed for a small number of users. Network speed and performance starts to deteriorate usually after more than 10 computers are on the network. This makes it difficult to grow the network when the need to add more computers on the network becomes unavoidable.

Possibility of not discovering all peers