Question4: Describe the progression of communications systems from the 1800s to the present. Answer: Data communications systems grew more rapidly and globally since 1800s to present, In the 1800s, it took several weeks for a message to reach North America by ship from England. By the 1900s, it could be transmitted within the hour. Today, it can be transmitted in seconds. Collapsing the information lag to Internet speeds means that people can communicate and access information anywhere in the world regardless of their physical locations.
Question23: In the 1980s when we wrote the first edition of this book, there were many, many more protocols in common use at the data link, network, and transport layers than there are today. Why do you think the number of commonly used protocols at these layers has declined? Do you think this trend will continue? What are the implications for those who design and operate networks? Answer: With more vendors to develop software and hardware leading creations of many new network models the number of commonly used protocols would be declining.
The standards developed by an official industry or government body implements more & more standards leading to many standards-making organizations. The rise in these pervasive, integrated networks will mean a significant increase in the availability of information services and more competition. Question24: The number of standardized protocols in use at the application layer has significantly increased since the 1980s. Why? Do you think this trend will continue? What are the implications for those who design and operate networks?
Answer: The significant increase of application layer is because of the major advantage of using different software and protocols is that it is easy to develop new software, because all one has to do is write software for one level at a time.
The developers of Web applications, for example, do not need to write software to perform error checking or routing, because those are performed by the data link and network layers. Developers can simply assume those functions are performed and just focus on the application layer.
Likewise, it is simple to change the software at any level (or add new application protocols), as long as the interface between that layer and the ones around it remains unchanged. Second, it is important to note that for communication to be successful, each layer in one computer must be able to communicate with its matching layer in the other computer. Chapter 2 Question2: Describe the four basic functions of an application software package. Answer: The four basic functions of an application software package are as follows— (1) Data storage.
Most application programs require data to be stored and retrieved, whether it is a small file such as a memo produced by a word processor or a large database such as an organization’s accounting records. (2) Data access logic, the processing required to access data, which often means database queries in SQL. (3) Application logic (sometimes called business logic), which also can be simple or complex, depending on the application. (4) Presentation logic, the presentation of information to the user and the acceptance of the user’s commands.
These four functions—data storage, data access logic, application logic, and presentation logic—are the basic building blocks of any application. Question3: What are the advantages and disadvantages of host-based networks versus client-server networks? Answer: The advantages and disadvantages of host-based networks versus client-server networks are Host-based Networks: Advantages – This very simple architecture often works very well. Application software is developed and stored on the one server along with all data. If ou’ve ever used a terminal, you’ve used a host-based application. There is one point of control, because all messages flow through the one central server. In theory, there are economies of scale, because all computer resources are centralized. Disadvantages – There are two fundamental problems with host-based networks. First, the server must process all messages. As the demands for more and more network applications grow, many servers become overloaded and unable to quickly process all the users’ demands. Prioritizing users’ access becomes difficult.
Response time becomes slower, and network managers are required to spend increasingly more money to upgrade the server. Unfortunately, upgrades to the mainframes that usually are the servers in this architecture are “lumpy. ” That is, upgrades come in large increments and are expensive. Client-Server Networks: Advantages – This simple architecture often works very well as most applications written today use client-server architectures. Client-server architectures attempt to balance the processing between the client and the server by having both does some of the logic.
In these networks, the client is responsible for the presentation logic, whereas the server is responsible for the data access logic and data storage. The application logic either resides on the client, reside on the server, or be split between both. Disadvantages – The fundamental problem in client-based networks is that all data on the server must travel to the client for processing. For example, suppose the user wishes to display a list of all employees with company life insurance.
All the data in the database must travel from the server where the database is stored over the network circuit to the client, which then examines each record to see if it matches the data requested by the user. This can overload the network circuits because far more data is transmitted from the server to the client than the client actually needs Question4: What is middleware, and what does it do? Answer: middleware – is the software that sits between the application software on the client and the application software on the server.
It does two things — First, it provides a standard way of communicating that can translate between software from different vendors. Many middleware tools began as translation utilities that enabled messages sent from a specific client tool to be translated into a form understood by a specific server tool. The second function is 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
Question15: What roles do SMTP, POP, and IMAP play in sending and receiving email on the Internet? Answer: Following are the roles of SMTP, POP, and IMAP play in sending and receiving email on the Internet— SMPT — The Simple Mail Transfer Protocol (SMTP) is the most commonly used email standard simply because it is the email standard used on the Internet. 2 Email works similarly to how the Web works, but it is a bit more complex. SMTP email is usually implemented as a two-tier thick client-server application, but not always.
POP – Post Office Protocol, before a user can read a mail message with a POP email client, the email message must be copied to the client computer’s hard disk and deleted from the mail server. IMPAP – Internet Message Access Protocol, email messages can remain stored on the mail server after they are read. IMAP therefore offers considerable benefits to users who read their email from many different computers (e. g. , home, office, computer labs) because they no longer need to worry about having old email messages scattered across several client computers; all email is stored on the server until it is deleted.
Question19: What is cloud computing? Answer: cloud computing, is a metaphor used by Technology or IT services companies that contracts with another firm to provide software services over the Internet, rather than installing the software on its own servers. The company no longer buys and manages its own servers and software, but instead pays a monthly subscription fee or a fee based on how much they use the application. Because the cloud-computing provider provides the same services to many companies, it has considerable economies of scale that drive down costs.