Some Computer Network Related Information.

*Computer-Networks related Info:*

*Definition - What does Server mean?

A server is a computer, a device or a program that is dedicated to managing network resources. Servers are often referred to as dedicated because they carry out hardly any other tasks apart from their server tasks.

There are a number of categories of servers, including print servers, file servers, network servers and database servers.

In theory, whenever computers share resources with client machines they are considered servers.

*special characteristics and capabilities, including:*

1. The ability to update hardware and software without a restart or reboot.
2. Advanced backup capability for frequent backup of critical data.
3. Advanced networking performance.
4. Automatic (invisible to the user) data transfer between devices.
5. High security for resources, data and memory protection.

Server computers often have special operating systems not usually found on personal computers. Some operating systems are available in both server and desktop versions and use similar interfaces. However, an increase in the reliability of both server hardware and operating systems has blurred the distinctions between desktop and server operating systems.

*Types of Servers:*

1. Proxy Server. ...
2. Mail Server. ...
3. Server Platforms. ...
4. Web Server. ...
5. Application Server. ...
6. Real-Time Communication Server...
7. FTP Server. ...
8. Collaboration Server.

*Definition - What does Application Server mean?*

An application server is a type of server designed to install, operate and host applications and associated services for end users, IT services and organizations. It makes easy the hosting and delivery of high-end consumer or business applications, which are used by multiple and simultaneously connected local or remote users.

*Application Server*

An application server consists of a server operating system (OS) and server hardware that work together to provide computing-intensive operations and services to the residing application. An application server executes and provides user and/or other app access when utilizing the installed application's business/functional logic. Key required features of an application server include data redundancy, high availability, load balancing, user management, data/application security and a centralized management interface. Moreover, an application server may be connected by enterprise systems, networks or intranet and remotely accessed via the Internet.

Depending on the installed application, an application server may be classified in a variety of ways, including as a Web server, database application server, general purpose application server or enterprise application (EA) server.

*Different Types of Application Servers (Models)*

*1. Dedicated Application Servers:*

The first one is called a dedicated application server. With this type of application server we are talking about one physical hardware server which is running one single network application. Some applications will actually require this. The benefit of using a dedicated application server is great performance, because the server hardware is serving a single application. All CPU and I/O resources are dedicated to providing a single service. However, this model is more expensive because it will force us to to have more physical servers installed for other purposes. That’s because organizations typically have to use more than one network application in their environment, and in that case we will need to purchase additional physical servers. Another issue depends on how heavily the network applications is being used. Depending on application usage, this model may result in unused capacity if the application is not often used. In that case the server is idle most of the time, which is not very efficient. However, most of the time this will not be an issue since dedicated servers are used for applications which will be used a lot.

*2. Distributed Application Servers:*

The next type of application server model is a distributed application server. With this model we still have one network application which we run on many different servers concurrently. So, we use multiple servers to provide the service. Many Web-based applications use a distributed model. More servers allow us to configure fault tolerance by using special software. If one of the servers goes down, other servers can take its place without any down time, and the end-user won’t even know that something happened to our server. More servers also mean scalability which means that we can balance the load between different servers by using a special software. This can be done in various ways, but for now it is only important to remember that different servers can share the load, which enables us to increase the number of users that can use the network application. End-users will see all this as a single service running on a single server, but we know that it’s actually multiple servers running one application. The downside of this type of model is the cost of implementation because it requires more hardware. Also we might have to pay extra money for the application to be able to run on more machines instead of one. We also might have to purchase some type of clustering software or load-balancing software to manage the load among different servers and provide fault tolerance feature.

*3.P2P or Peer-to-peer Application Servers:*

The last model we should know about is the P2P or Peer-to-peer model. When talking about computer networks, we already know that we can configure a peer-to-peer type of computer network. In this type of network we have workstations that provide services on the network and in the same time consume services on the network. So, the systems are a server and a client at the same time as opposed to client/server network where servers provide services and clients consume services. In P2P application model we have application that runs on multiple systems which contribute with their resources. The applications could be running as a client or running as a server for other instances of an application. The key advantage of a P2P application is that it uses server hardware very efficiently. If we have many different server systems, the peer-to-peer application model can balance the load more effectively when compared to distributed application server model, and provide the best performance possible. This is accomplished by analyzing the servers and determining how to load balance. However, the peer-to-peer application model is more complex to set up.

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