Client-Server Pattern

As used in computer science, client-server is a software made up of two sections; client system and the server system where the two communicate over a computer network or using one computer.The application is an interactive consisting of both client and server software. This pattern is efficient in sharing the tasks. The client process is the initiator of connection while the server process waits for the client to make requests. The client-server pattern has a type where both the client process and the server process run in the same computer. This type is called single seat set up.

The relationship between the server and the client explains how the client makes service request from the server and how the server responds to the requests made.the server accepts the requests, process them and gives an output of the requested information to the client.A basic client-server architecture is composed of only two participants; the clienta and the hosts (two-tier).this is so because the client is one tier and the server is another tier.

Examples of clients include web browsers, e-mail clients and online chat clients.On the other hand, the examples of the servers are e-mail servers, file servers and web servers.

CHARACTERISTICS OF THE CLIENT

It always makes requests to the servers.

It always waits for the servers to give an output.

It always receives the feedback from the servers.

It always connects to a limited number of servers at a particular time.

CHARACTERISTICS OF THE SERVERS

It waits for requests to be made the clients.

It processes the request made the clients and gives an output of the request made.

It may communicate with other servers so as to process the request made by the client.

It has no direct interaction with end users.

ADVANTAGES

It is encapsulated; the components are independent.

The data stored is secured. The data is stored in the servers and can be controlled so that only the permitted clients can access the data.

The servers are able to work with many clients whose specifications are different.

DISADVANTAGES

Overloading. Increase in the number of clients sending requests simultaneously to the server leads to traffic blocking.

One node distribution of servers. Incase of failure of one of the servers, clients requests cannot be processed.

`MULTI-TIER DESIGN

The multi-tier architecture breaks down the processing into discrete tiers that are distributed between the clients and the servers. An application in this design has the presentation tier, a middle tier and a data-tier. Creation of a discrete project for each of the tier to be included in the application is the easiest method of separating the n-tiers in an n-tier application. Separating the components of an application in different entities makes it easier to maintain. This is achieved as it allows easy incorporation of new technologies that are applicable to a single tier without the need to design a new system. Moreover, in multi-tier architecture, the sensitive information is stored in the middle-tier and therefore it is in isolation from the presentation-tier.

Presentation-tier

The users interact with the application through it.its composition is:

The components that binds data for example BindingSource and BindingNavigator.

The presentation of data using objects for example LINQ to SQL.

This tier accesses the middle-tier but does not make a direct access to the data-tier. Its interaction with the data-tier is facilitated by the data access component in the middle-tier.

Middle-tier

It is a link that enables the presentation-tier and data-tier to communicate. It is composed of:

Logic of business for example the rules of business and the validation of data.

Components that access data and logic.

The middle-tier normally connects to the data-tier through data connection stored in the data access component.

Data-tier

It is a server whose purpose is to store data of an application.

Advantages

Availability: The presentation-tier is able to process web requests using cache in an event where the application-tiers server is down

Performance: The utilization of network is minimized as well as reduced loading on the application and data tiers since the presentation-tier can cache.

Scalability: Each tier can scale horizontally.

Disadvantages

Templates, assets, uploaded images and files must be pushed manually from the application tier to the presentation tier.

Content creation is only done in the application-tier whereas content can only be viewed in the presentation-tier

PEER-TO-PEER DESIGN

It is a non-centralized model of communication whereby all the participating parties have the same abilities to initiate communication. It is in contrary to the client-server design where the client sends a service request to the server for processing. In this design, every component servers as both the client and the server. Peer-to-peer systems can be used in anonymized routing of network traffic, large parallel environments of computing and distributed storage. Most of its programs are focus media sharing and, therefore, mostly associated software privacy and copyright violation.

Applications of this design permit the users to be in control of many parameters. Examples are; the number of member connection allowed at a time, whose systems to connect or avoid, the services to offer and the number of system resources to develop to the network.

Advantages

Its installation and configuration of computers on this network is easy.

There is no central dependency and, therefore, in an event of one of the peer failing there is no effect on the working of other peers.

All the peers share resources and contents which are in contrary to the client-server design.

Since every user controls his/her machine, there is no need for full time administration.

Disadvantages

Due to its non-centralized nature, the administration of the system is very difficult.

Legally exposes the organizations administrator

It can spread firewalls and malware.