Application Layer

Question 1

What are the Application layer architecture features? It determines how the client/server divides their workload

Answer 1

• The presentation logic defines the user interface and controls the application
• The application/business logic describes what the application does.
• The data access logic describes how the application manages its data.
• The data storage logic describes where the data is stored e.g files, data base.

Question 2

Define the Server-based architecture and its features?-

Answer 2

In the server-based architecture, the server does all of the logic while the client is a “dumb” terminal sending keystrokes to the server from the server’s instructions. The server becomes a bottleneck due to a lot of tasks and upgrade becomes expensive and “lumpy”.

Question 3

Define the Client-based architecture and its features.

Answer 3

In the client-based architecture, all of the logic is handled by the client while the server stores the data. This means that data would need to move back and forth between the server and client.

Question 4

Define the Client-based architecture and its features.

Answer 4

In the client-based architecture, all of the logic is handled by the client while the server stores the data. This means that data would need to move back and forth between the server and client.

Question 5

Define the Client-Server architecture and its features.

Answer 5

In a client-server architecture, the client handles the application and business logic while the server stores and manages the data. The processing load is balanced between client and server.

Question 6

Define the Thin-Client architecture and its features.

Answer 6

In a thin-client architecture, the server handles most of the logic except the presentation logic. This would mean that only one server needs updating!

Question 7

Define the Multi-tier architecture and its features.

Answer 7

In a multi-tier architecture, an additional server handles the application/business logic while another server stores and manages the data. Meanwhile, the client needs to simply control the application .

Question 8

Define the Peer-to-peer architecture and its features.

Answer 8

In a peer-to-peer architecture, the computer acts as both a client and a server. Local logic is used to access data from another computer.

Question 9

What are the application layer protocols?

Answer 9

HTML, SMTP

Question 10

What is the World Wide Web?

Answer 10

The world wide web (WWW) is based on two main technologies - HTTP and HTML. HTTP is a protocol for communication between the client and the server while HTML is a format to describe webpages.

Question 11

What is HTTP?

Answer 11

The Hypertext Transfer Protocol defines how a web browser(client) communicates with web server. It is based on two innovative ideas- Hypertext and URL. Hypertext is a document with links to other documents. The URL (Unified Resource Locators) is the standard for identifying the links to other document. HTTP as a whole defines how documents are requested and transferred.

Question 12

How is HTTP performed?

Answer 12

The request-response cycle between the web browser(client) and web server enables the client to request a document through an HTTP request (URL)and the server to respond with a HTTP response. (HTML)

Question 13

What are some HTTP methods?

Answer 13

THE GET method retrieves the specified URL from a server.

The HEAD method retrieves only the header of the specified URL.

The POST method adds data to the request body to the specified URL.

Question 14

What is a HTTP request and response?

Answer 14

The client sends a HTTP request with a HTTP method to a server for a HTTP response . The HTTP header and body for request and response are optional.

Question 15

How does HTTP add states?

Answer 15

HTTP is stateless i.e each request is an independent transaction. However, sometimes states need to be added to identify and keep track of the session. Hence there are two approaches to add HTTP states-

1. Client sends the session identifier as POST with every request
2. The server sets a cookie and client transmits the cookie with every request

Question 16

What is HTTML?

Answer 16

The HTML documents is a format to describe web pages using tags. It provides the structure and backbone of a webpage.

Question 17

What is SMTP?

Answer 17

The Simple Mail transfer protocol handles transfer of text messages between email client and server and also between two email servers. SMTP handles plain text email.

Question 18

What is POP?

Answer 18

The Post Office Protocol is where messages are downloaded from the client and deleted from the server.

Question 19

What is IMAP?

Answer 19

The Internet Message Access Protocol is where messages remain on the server and multiple clients can be connected simultaneously to the same mailbox.

Question 20

What is MIME?

Answer 20

Multi-Purpose Internet Mail Extensions is an extension of SMTP as the latter handles plain text email. MIME specifies an encoding can handle unicode characters, non text messages, files, attachments, etc. It uses base-64 encoding*

Question 21

What is the difference between two-tier and three-tier mail?

Answer 21

Two-tier email is based on the client-server architecture where the client handles the application logic and communicates with the server using SMTP and POP/IMAP.

Three-tier email is based on the thin-client architecture where a thin client can access the mail via an application and clients can access through the server using HTTP. The server handles application logic.

Server-to-server uses SMTP and POP

Server-to-client uses HTTP.