Different Client Server Architectures

This architecture can be considered as a network model where a machine or process involved, is either a client or a server. Servers are usually machines with high processing power, dedicated in synchronizing network traffic (network servers), devices as disk drives (file servers), printers (print servers). Clients are basically machines or workstations which are dependent on servers for resources, data and devices (Client/Server Architectures,2011). 

Apart from centralized distributed client/server model, peer-to-peer architecture remains a major concern as it conquers a distribution of equal responsibility among each node. Both these models are widely used in the industry and both include advantages and disadvantages as mentioned below (Client/Server Architectures,2011).

Implementation methods and their applications

The client/server architecture functionality divides into categories as 2-tier, 3-tier and N-tier models and the serviceable units consist of user interface, business logic and the shared data. Since the content of this report is towards a network perspective, I have not elaborated on the 1-tier architecture as they are non-distributed, end-user applications

2-tier Client/Server Architecture

Two tier software architectures were built in 1980’s based on the file server software architectural behavior projected mainly to improve usability through the support of form based user-friendly interfaces. It also provides increased scalability via supporting upto 100 users though the file server model supports only dozen of users. Often corporate data can be shared over homogenous environment enhancing flexible usage. This model necessitates minimal operator intervention mostly used in non-complex, non-time critical information processing systems. Eg: File Servers, Database Servers with Stored Procedure (Client/Server Architectures,2011).

Two tier paradigms consist of three components dispersed in two layers: client (supplicant of services) and server (supplier of services) mentioned as below.

• ·        User System Interface (session, text and dialog input, display management services)
• ·      Processing Management (process development and performance, process monitoring, process resource services)
• ·        Database Management ( data and file services) 

In this architecture User System Interface is entirely allocated to the client and the Database Management is placed on the server whereas the Processing Management is functionally dispersed on both client/server resulting two layers (Client/Server Architectures, 2011).

The application logic can reside on client-side, within a user interface or server-side within a database independently or on both sides. These applications can be simply built using visual builder tools helpful in developing applications for small-scale groupware entitled for decision support systems and in the creation of web publishing applications (Client/Server Architectures, 2011). 

Characteristics

• In this model the client is capable of communicating directly with the server application with no presence of an intermediate application (Bhuvana, 2006).

• Usually the Business logic is contributed towards the server or the client.

·          Fat Server with Thin Client scenario is when the business logic is attached to the client (Bhuvana, 2006).

·          Fat Client with Thin Server scenario is when the business logic is attached to the corporate server (Bhuvana, 2006).

• The Procedure in which the client application interacts with the server is achieved through the usage of a database bridge known as Application Programming Interface (API) (Bhuvana, 2006). Commonly used API’s include JDBC- as Java Database Connectivity.

• Each machine consisting of a client application entitled to the usage of a database-driver to interact with the database. In case the database changes it’s necessary to re-install the driver which increases the Deployment cost.

• A separate database connection underlies in every client of the network, which are limited and expensive.

• Usually database connections retain even if no client interaction occurs, enabling the database to be available to other clients thus making a limited number of clients to access the database at a time.

When simultaneous client request occurs, or when there’s an incensement in the data transfer path- number of trips across a physical boundary, it causes higher network traffic.

In the occurrence of a database operation the data is transferred across a physical boundary separating business logic and data tiers.

When considering the applications of the 2-tier model we often come across classic client/server interactions where client refers to a custom application developed in a language like Delphi or Visual Basic whereas the server is a database engine like SQL Server, Postgres or Oracle, e.g- Library and Lab Reservation Systems where the UI has direct communication with the database server (Chapple, 2011).

Also due to the fact that majority of web applications conclude no separation of business logic form presentation and application servers they are also considered as 2-tier applications using PHP, ASP, ASP.Net etc to connect to the databases via connector objects like ADO, ADO.Net or proprietary connectors (Dilettante, 2010).

Real scenario is often this seems unsuccessful in larger scale implementations grown beyond the departmental LAN, rather than in small scale or prototype level implementations. But fortunately it underwent a transition phase which made it possible to nurture beyond the departmental LAN’s, enforcing to develop 3-tier and the N-tier applications with the help of mounting technological aspects (Dilettante, 2010).

Bibliography

·     slideshare. (2011). Client Server Architecture. [Online]. Available from: http://www.slideshare.net/suks_87/client-server-architecture-presentation. [Accessed: 20th January 2011]

·     bhuvana. (2006). Two-Tier Architecture. [Online].Available from: http://bhuvans.wordpress.com/2006/08/22/two-tier-architecture/. [Accessed: 27th January 2011]

·  Chapple. (2011). Two-Tier or n-Teir. [Online].Available from: http://databases.about.com/od/specificproducts/a/architectures.htm. [Accessed: 27th January 2011]

·   dilettante. (2010). Vb Forums. [Online].Available from: http://www.vbforums.com/showthread.php?t=620167. [Accessed: 25th January 2011]