Write 3 pages thesis on the topic physical architecture layer design. It involves the plan for the hardware and software used in the system, security of the system, communication infrastructure and global support. It is at the physical layer architecture design that a decision on the type of physical architecture of the system is made. The architecture can be chosen from server-based, client-based or client –server architectures depending on the system to be designed. Architectural components The components of a physical layer can be widely grouped in two categories, mainly hardware and software (application). Hardware components may include the computers (clients and the servers) and the network used in the system while the software components comprise data storage, data access logic, application logic and presentation logic. Software components are as vital for the running of the system as the hardware.(Wixom, 12) Among its many functions are: data storage. achieved by documenting data in the CRC cards, presentation of the information to the user while accepting the user commands through the application logic and processing needed to access data like database queries through data access logic. The hardware components on the hand include the physical computers and the networks connecting the computers to form a distributed system. The computers can either be sever or client. Different arrangement of the computers gives different physical architectures. Physical architectures Physical architectures are composed of clients (I/O hardware used by user, PCs and terminals), servers (mainframes, minis or micros) and network (hardware and software to connect client to server) and are grouped in three categories namely client based, server based and client server based. (Denis, 2) In Server based architecture, the server performs all the four application functions presentation logic, data access logic, application logic and data storage. The client only need basic hardware like the monitor and keyboard to communicate with the server. Upgrading this type of architecture can be quite expensive beside the fact that the server can become overloaded since the server does everything which may result to system failure. (Kendall, 8) As opposed to Server based architecture, in Client based architecture the client does most of the work as the server just deals with data storage functions. All the logic resides in the client computer while data is stored in the server computer. All the data must travel over the network to the server for processing which may lead to a lot of network traffic. This type of architecture is simple to develop but hard to maintain. Client-server architecture is more preferable as compared to server and client based architecture since it balances processing between the client and the server unlike the two other architectures. It is the mostly used architecture in modern system among the three architectures. The client computer mainly deals with the presentation and application logics while data access and data storage logics are handled by the server computer. There are two or more tiers available for this architecture depending on the partitioning of the application logics.