Fundamentals of Application Architecture

1. What are the different types of application architectures? There are three different fundamental application architectures. In host-based networks, the server performs virtually all of the work. In client-based networks, the client computer does most of the work; the server is used only for data storage. In client-server networks, the work is shared between the servers and clients. The client performs all presentation logic, the server handles all data storage and data access logic, and one performs the application logic. Client server networks can be cheaper to install and often better balance the network loads but are far more complex and costly to develop manage. 2. Describe the four basic functions of an application software package. Basic functions of an application Layer

Data storage
Storing of data generated by programs (e.g., files, records) Data access logic
Processing required accessing stored data (e.g., SQL)
Application logic
Business login such as word processors, spreadsheets
Presentation logic
Presentation of info to user and acceptance of user commands 7. Compare and contrast two-tier, three-tier, and n-tier client-server architectures. What are the technical differences, and what advantages and disadvantages does each offer? Two-tier client server architecture uses only two sets of computers, one set of clients and one set of servers. Three-tier architecture uses three sets of computers. In this case, the software on the client computer is responsible for presentation logic, an application server is responsible for the application logic, and a separate database server is responsible for the data access logic and data storage. Coming to n-tier architecture uses more than three sets of computers. In this case the client is responsible for presentation logic, a database server is responsible for the data access logic and data storage, and the application logic is spread across two or more different set of servers.

The primary advantages of an n-tier client-server architecture compared with a two-tier and three-tier is that it separates out the processing that occurs to better balance the load on the different servers; it is more scalable. We have three separate servers, which provides more powerful server, or even put in two application servers. The primary disadvantages to an n-tier architecture compared with two-tier and three-tier architecture, it puts greater load on the network. It generates more difficult to program and test software in n-tier architectures than in two-tier architectures because more devices have to communicate to complete a user’s transaction.

10. What do the following tools enable you to do: the web, e-mail, FTP, telnet? Web
One of the fastest growing Internet applications is the web. It began with two innovative ideas: -Hypertext
A document containing links to other documents
-Uniform Resource Locators (URLs)
A formal way of identifying links to other documents. E-mail
Electronic mail was one of the earliest applications on the Internet and is still among the most heavily used today. With e-mail, users create and send message to one user, several users, or all users on a distribution list. File Transfer Protocol (FTP)

FTP enables you to send and receive files over the Internet. FTP works in a similar manner as HTTP. FTP requires an application layer program on the client computer and a FTP server application program on a server. Telnet

Telnet enables users to log in to servers (or other clients). Telnet requires an application layer program on the client computer and an application layer program on the server or host computer. 11. For what is HTTP used? What are its major parts?

The standard protocol for communication between a web browser and a web server is Hypertext Transfer Protocol (HTTP). It has three parts. The first two parts are required; the last is optional. The parts are: -The request line, which starts with a command (e.g., get), provides
the web page and ends with the HTTP version number that the browser understands; the version number ensures that the web server does not attempt to use a more advanced or newer version of the HTTP standard that the browser does not understand. -The request header, which contains a variety of optional information such as the web browser being used (e.g., internet explorer) and the date. -The request body, which contains information sent to the server, such as information that the user has typed into a form. 12. For what HTML used?

HTML is known as Hypertext Markup Language. It is the predominant markup language for web pages. It provides a means to describe the structure of text-based information in a document by denoting certain text as links, headings, paragraphs, lists, and so on. HTML can also describe, to some degree, the appearance and semantics of a document, and can include embedded scripting language code which can affect the behavior of web browsers and other HTML processors. 13. Describe how a web browser and web server work together to send a web page to a user. The web is the most common way for business to establish a presence on the Internet. The web has two application software packages, a web browser on the client and a web server on the server.

Web browser and servers communicate with one another using a standard called HTTP. 16. What roles do SMTP, POP, and IMAP play in sending and receiving e-mail on the Internet? With e-mail, users create and send messages using an application-layer software package on client computers called user agents. The user agent sends the mail to a server running an application-layer software package called a mail transfer agent, which then forwards the message through a series of mail transfer agents to the mail transfer agent on receiver’s server. Several standards have been developed to ensure compatibility between different user agents and mail transfer agents. SMTP, POP, and IMAP are used on the internet. 19. What is FTP, and why is it useful?

File Transfer Protocol (FTP) enables you to send and receive files over the Internet. FTP works in a similar manner as HTTP. It requires an application program on the client computer and a FTP server program on a server. It is commonly used today for uploading web pages. 20. What is Telnet, and why is it useful?

Telnet enables users to log in to servers (or other clients). Telnet requires an application layer program on the client computer and an application layer program on the server or host computer. It is useful because it enables you to access your server or host computer without sitting as its keyboard. It also poses a great security threat. 26. It says that Internet explorer cannot be displayed.