Sunday, 4 December 2016


Behrouz A Forouzan, Data Communication and Networking - 4th ed (Chapter 1)


Review Questions

1. For n devices in a network, what is the number of cable links required for a mesh, ring, bus, and star topology?
Ans: n(n-1)/2 cable link are required for mesh, n for ring, n-1 cable link for bus, and n cable link for star topology.
2. What is the difference between half-duplex and full-duplex transmission modes?
Ans: In half-duplex mode, each station can both transmit and receive, but not at the same time.When one device  is sending, the other can only receive,and vice versa. Like walkie-talkies.
In full-duplex mode, both station can transmit and receive simultaneously. Like telephone network.
3. What are some of the factors that determine whether a communication system is a LAN or WAN?
Ans: Size and Coverage of area determine whether a communication system is LAN or WAN. A LAN normally covers an area less than 2 mile, a WAN can be worldwide.
4. Identify the five components of a data communications system?
Ans: A data communications system has five components-(i) Message, (ii) Sender, (iii) Receiver, (iv)Transmission medium, (v) Protocol.
5. What are the advantages of a multipoint connection over point-to-point connection?
Ans: In a multipoint environment, the capacity of the channel is shared, either spatially or temporally. If several devices can use the link simultaneously, it is a spatially shared connection. If users must take turns, it is a timeshared connection.
6. Why are standard needed?
Ans: Standard are essential in creating and maintaining an open and competitive market for equipment manufacturers and in guaranteeing national and international interoperability  of data and telecommunications technology and processes. Standard provide guidelines to manufacturers, vendors, government agencies, and other service providers to ensure the kind of interconnectivity necessary in today's marketplace and in international communications.
7. What are the advantages of distributed processing?
Ans: Most networks use distributed processing, in which a task is divided among multiple computers. Instead of one single large machine being responsible for all aspects of a process,separate computers (usually a personal computer or workstation) handle a subset.
8. Name the four basic network topologies, and cite advantage of each type.
Bus Topology: Easy installation, less cabling, easy expandation etc.
Ring Topology: Less effort in adding or removing devices, simple fault isolation.
Star Topology: Less expensive than mesh, robustness etc.
Mesh Topology: Robustness, present of privacy and security.
9. What is an internet? What is the Internet?
Ans: When two or more networks are connected, they become an internetwork, or internet.
The most notable internet is called the Internet, a collaboration of more than hundreds of thousands of interconnected networks. Private individuals as well as various organizations such as government agencies, schools, research facilities, corporation, and libraries in more than 100 countries use the internet.
10. What are the two types of line configuration?
Ans: Point to point and Multipoint.
11. What are the three criteria  necessary  for an effective  and efficient  network?
Ans: Performance, Reliability, Security.
12. Why are protocols needed?
Ans: In computer networks, communication occurs between entities in different systems. An entity is anything capable of sending or receiving information. However, two entities can not simply send bit streams to each other and expect to be understood. For communication to occur, the entities  must agree on a protocol.
13. Categorize the four basic topologies in terms of line configuration.
Point to point- mesh and star.
Multi point- bus and ring.


14. What is the maximum number of characters or symbols that can be represented by Unicode?
Ans: The code can define up to 2^(32) (4,294,967,296) characters or symbols. 
15. A color image uses 16 bits to represent a pixel. What is the maximum number of different colors that can be represented?
Ans: The number of different colors you can represent with 16 bits is 216, or about 65k colors.
16. Assume six devices are arranged in a mesh topology. How many cables are needed? How many ports are needed for each device?
Ans: Cables needed (6*5)/2 = 15 and,
Each device needs to be connected to 5 other devices. So, each device needs to have 5 ports. Six devices times five ports equals 30 total ports.
17. For each of the following four networks, discuss the consequences if a connection fails. 
      a. Five devices arranged in a mesh topology,
Ans: Mesh is high redundancy. Only one device would be disconnected if all the connections were to fail for that device. You can have many connections to other devices thats why its less likely to fail. The only cause for failure at this point is really the power and if you just don't have any. Even if one of the connections between two devices fail there is no effect on network and they can still communicate through other channels.
      b. Five devices arranged in a star topology (not counting the hub),
Ans: Star runs to a central device like a switch, so if the switch itself fails then the whole network will be disconnected.
      c. Five devices arranged in a bus topology,
Ans: Bus runs in a straight line from one network device to another. So if one gets disconnect then the all the devices connected down the line get disconnect.
      d. Five devices arranged in a ring topology.
Ans. Ring is like a bus except it connects back onto itself. So if one device fails they all fail. The exception is if there is a redundant inside ring like that used in FDDI (fiber ring) then if both get disconnect from one device then they all do.
18. You have two computers connected by an Ethernet hub at home. Is this a LAN, a MAN, or a WAN? Explain your reason.
Ans: This is a LAN (Local Area Network). A WAN is a Wide Area Network that typically connects machines that are geographically remote. A Man is a Metropolitan Area Network - that connects together all machines  in an enterprise, campus or town.
19. In the ring topology in Figure 1.8, what happens if one of the stations is unplugged?
Ans: The network would stop functioning because the token has to pass through each station in the ring.
20. In the bus topology in Figure 1.7, what happens if one of the stations is unplugged?
Ans: From that station rest all will stop functioning.
21. Draw a hybrid topology with a star backbone and three ring networks.
Ans: topology-with-a-Star-backbone-connecting-three-ring-networks.gif
22. Draw a hybrid topology with a ring backbone and two bus networks.
Ans: ring-backbone-with-two-bus-network.jpg
23. Performance is inversely related to delay. When you use the Internet, which of the following applications are more sensitive to delay? 
       a. Sending an e-mail 
       b. Copying a file 
       c. Surfing the Internet
Ans: It is true that performance is inversely proportional to delay.
Sending an email is more sensitive to delay than copying a file and surfing the internet.Because  E-mailing may be interrupted due to high latency, but can always assume as soon as the server is performing again, without user interaction.
Copying a file is less sensitive to delay than surfing the web and sending an e-mail.
Surfing the web is not so much affected by delay because due to effect of latency on surfing the net. 
24. When a party makes a local telephone call to another party, is this a point-to-point or multipoint connection? Explain your answer.
Ans: It is Point-to-Point connection because multipoint connection needs more than two end points.
25. Compare the telephone network and the Internet. What are the similarities? What are the differences?
Ans: Both are the ways of Communications, Both can be make by wires/wireless. Both are capable to two way traffic of signals.
Internet allows us to share our files with our Friends while telephone don't. Video chat is being used by people who has the access to internet, but it isn't possible through telephone. 
Posted 4 by Daniyalyounis

Wednesday, 3 February 2016

to downlaod the form please click the link below.

Tuesday, 2 February 2016


“Data Savers Inc.” is a newly established company which provides the services of data storage to its clients. This company is currently limited to one data warehouse, but now this company wants to extend its data warehouses countrywide. At first step, the future planning is to establish data warehouses at different locations of Lahore and also one data warehouse in Islamabad. These data warehouses should also be connected with each other with secured connections. You are required to discuss precisely on the following points:

i.Which type of network should be implemented by this company using public infrastructure to connect data warehouses of Lahore with Islamabad if they have low budget?

This company must implemented VPN type of the network. A VPN type of network has also low expenses for establishing network without any private channel. Because a private company wants to establish public infrastructure to connect data from one city to another city, therefore there is only suitable VPN network of type. Because company wants establish network of type with low budget, therefore it is suitable VPN network of type with low prize, secured and without interference of third party threats.

ii.If they do not have any budget limitation then which type of communication medium will be more suitable to connect nearby data warehouses of Lahore only and why?
Please read the scenario carefully before writing your comments on the said topics.

If the company has no budget limitations and want to more suitable medium to connect the nearby houses in Lahore only, then company should use Wide Area Network. Because Wide Area network computer are connected for nearby houses therefore it's securely communication medium suitable for the 

Friday, 29 January 2016

CASE The Stanze textiles company

The Stanza Textiles company has printing, spinning, weaving and dyeing units under their own setup.
Further, it has a team of highly professional management and technical staff with standardized working
system. They are in a continuous process of expansion, enhancement and incorporating the latest
technological innovations in order to ensure their customers the best possible quality in home apparels.
The company is proud of its driving force by dynamic, well qualified and highly skilled management
who has extensive knowledge in all aspects of textile exports. As the company has its own production
units of Weaving, Dyeing, Printing & Spinning that made them enable to produce multiple orders with
agility and good quality products according to customer requirements. Utmost attention is given to
maintain quality standards across all stages of production. This is all possible due to its state of the art
production facility.
Question # 01:
Keeping in view the above case, you are required to identify the type of departmentalization that Stanza
Textiles company is following and also draw the structure of departmentalization of the given company.
Question # 02:
In your point of view, what advantages Stanza Textiles company is having by following the type of
departmentalization in above case? (At least three points)
Q1: Answer:'' printing, spinning, weaving and dyeing units = Departmentalization "
The Stanza Textile Company has printing, spinning, weaving, and dying units under their own setup. Departmentalization is very important in organizations. It involves diving an organization into different departments. Since Stanza is a textile company and in textile companies the “departmentalization process” is the main department, which involves spinning, weaving, dying, and printing. We can say Stanza textile is a manufacturing company and also any manufacturing company requires some functions to perform their tasks.
There are some departments, which performs such functions like marketing department, human resource department, accounting department, and production department. The structure of departmentalization of the given company is the main function of the textile company.
The customer departmentalization is used to control the customers of every type, foreign, domestic, wholesalers, and retailers. It also depend upon the worth of the company that whether it works with the foreign customer or not.
The time departmentalization is also a department work in an organization which works 24 hours a day for the purpose of the department to manage duties of the workers in the night and in the day hours.
These are the main departmentalisations in the textile company.
Question 1 part(B):
Structure diagram or above,:
 photo attached

Answer for Question 2:
There are some advantageous of the departmentalization:
1- It offers better customer service and the customers get quick and efficient service due to the customer departmentalization in the Stanza textile company.
2- It divides the work into different units on the basis of responsibility and nature. It also helps top managers in their work.
3- Stanza Textile Company easily grows and expands due to departmentalization without the departmentalization company cannot effectively perform all operations.
daniyal younis