Chapter 2: Application Layer

Question 1

What is Application Architecture?

Answer 1

The way in which the functions of the application layer software are spread among the clients and servers in the network.

Question 2

What are the Five General Functions of any Application Program?

Answer 2

Data Storage, Data Access Logic, Presentation Logic (User Interface), Application Logic, Services Logic

Question 3

What are the three deployment methods of Cloud Computing that Organizations use?

Answer 3

Private Cloud, Public Cloud, Community Cloud

Question 4

What is Pure Strategy?

Answer 4

When an organization will choose to use only one deployment model for all its cloud-based applications.

Question 5

What is the Hybrid Strategy?

Answer 5

allows the organization to take advantage of the benefits that these different cloud deployment models offer. For example, a hospital can use Gmail for its email application (public cloud) but a private cloud for patient data, which require high security. The downside of a hybrid cloud strategy is that an organization has to deal with different platforms and cloud providers.

Question 6

What are the Five functions that can be allocated between the client computers and the servers in a network.

Answer 6

Host-Based Architectures, Client-Based Architectures, Client-Server Architectures, Cloud-Based Architectures

Question 7

What is Middleware?

Answer 7

software that sits between the application software on the client and the application software on the server. Middleware does two things:

1. provides a standard way of communicating that can translate between software from different vendors.
2. to manage the message transfer from clients to servers (and vice versa) so that clients need not know the specific server that contains the application’s data.

Question 8

What are Three of the most important standard models for Middleware?

Answer 8

Distributed Computing Environment (DCE)
Common Object Request Broker Architecture (CORBA)
Open Database Connectivity (ODBC) {provides a standard for data access logic.}

Question 9

What is a two-tier architecture?

Answer 9

A partitioning between the client and the server that uses only two sets of computers, one set of clients and one set of servers.

Question 10

What is a Three-tier architecture?

Answer 10

uses three sets of computers, the software on the client computer is responsible for presentation logic, an application server is responsible for the services logic and application logic, and a separate database server is responsible for the data access logic and data storage.

Question 11

What is N-Tier Architecture?

Answer 11

Uses more than three sets of computers.

the client is responsible for presentation logic, a database server is responsible for the data access logic and data storage, and the services logic and application logic are spread across two or more different sets of servers.

Question 12

What is a Thin Client Architecture?

What is a Thick Client Architecture?

Answer 12

1. places little or no application logic on the client.

2. places all or almost all of the application logic on the client

Question 13

What is Software-as-a-Service (SAAS)?

Answer 13

one of the three cloud computing models. An organization outsources the entire application to the cloud provider and uses it as any other application that is available via a browser (thin client). SaaS is based on multitenancy. This means that rather than having many copies of the same application, there is only one application that everybody shares, yet everybody can customize it for his or her specific needs (Similar to renting a room in a office).

Question 14

What is Platform-as-a-Service (PAAS)?

Answer 14

Is when developers in an organization decide what programming language to use to develop the application of choice. The needed hardware and software infrastructure, called the platform, is rented from the cloud provider. In this case, the organization manages the application and its own data but uses the database software (data access logic) and operating system provided by the cloud provider.

(PaaS providers include: Amazon Elastic Cloud Compute (EC2), Microsoft Windows Azure, and Google App Engine.)

Question 15

What is Infrastructure-as-a-Service (IAAS) or Hardware-as-a-Service (HAAS)?

Answer 15

Where the cloud provider manages the hardware, including servers, storage, and networking components. The organization is responsible for all the software, including operating system (and virtualization software), database software, and its applications and data.

only the hardware is provided; everything else is up to the organization.

Question 16

What is Scalability?

Answer 16

the ability to increase (or decrease) the capacity of the servers to meet changing needs.

Question 17

What is HTTP?

Answer 17

Hypertext Transfer Protocol.

The standard protocol for communication between a Web browser and a Web server

Question 18

What is inside a HTTP Request?

Answer 18

1. A Request Line
2. A Request Header
3. A request Body

(First two are mandatory, last one is optional)

Question 19

What is in a HTTP Response?

Answer 19

1. A Response Status
2. A Response Header
3. A Response Body

(only the first one is mandatory)

Question 20

What is SMTP?

Answer 20

the most commonly used email standard simply because it is the email standard used on the Internet.usually implemented as a two-tier thick client–server application, but not always

Question 21

Explain a Two-Tier Email Structure

Answer 21

each client computer runs an application layer software package called a mail user agent, which is usually more commonly called an email client. The user creates the email message using an email client, which formats the message into an SMTP packet that includes information such as the sender’s address and the destination address.