Ch 1: Introduction to Data Communications

Question 1

Core IT capabilities within Organizational Settings.

Answer 1

1. Storing and retrieving data
2. Analyzing and Visualizing data
3. Automating data operations
4. Protecting data

Question 2

What is MIS?

Answer 2

An information system used for decision-making, and for the coordination, control, analysis, and visualization of information in an organization.

Question 3

What is Data Communications?

Answer 3

The movement of computer information from one point to another by means of electrical or optical transmission systems (called Data Communications Networks)

Question 4

What are the three basic components of a Data Communications Network

Answer 4

1. A Server
2. A Client
3. A Circuit

Question 5

What is a server?

Answer 5

Stores data or software that can be accessed by clients

Question 6

What is a client?

Answer 6

The input/output hardware device at the user’s end of a communication circuit

Question 7

What is a circuit?

Answer 7

The pathway through which messages travel

Question 8

What is a peer-to-peer network?

Answer 8

A network without a server(computers function as equals rather than relying on a server)

Question 9

Local Area Network Terms

Answer 9

1. This network has several personal computers(clients) connected through switch and cables(circuit)
   2.Computers connect wirelessly through a wireless access point(WAP)
2. Router is a special device that connects two or more networks

Question 10

Name the three server types

Answer 10

1. File server
2. Web server
3. Mail server

Question 11

What is a file server?

Answer 11

Stores data and software that can be used by computers on a network

Question 12

What is a Web server?

Answer 12

Stores documents and graphics that can be accessed from any web browser

Question 13

What is a Mail server?

Answer 13

Handles and delivers email over the network

Question 14

What is a Local Area Network?

Answer 14

A group of computers located in the same general area(commonly operates at 100 million bits per sec: 100 mbps)

Question 15

Define backbone network

Answer 15

A larger central network connecting several LANs, other BNs, MANs, and WANs (Typically 100-1,000 mbps)

Question 16

Wide Area Networks (WANs)

Answer 16

connect BNs and MANs
(Most organizations do not build their own WANs)

Question 17

What is an Intranet?

Answer 17

a LAN that uses the same technologies as the Internet but is
open to only those inside the organization (Sometimes, an intranet is provided by a completely separate Web server hidden from
the Internet)

Question 18

What is an Extranet?

Answer 18

a LAN that uses the same technologies as the Internet but is
provided to invited users outside the organization who access it over the
Internet (It can provide access to information services, inventories, and other internal
organizational databases that are provided only to customers, suppliers, or those who have paid for access)

Question 19

Network Models

Answer 19

• All networks provide the same basic functions to transfer a message from
  sender to receiver
• Each network can use different network hardware and software to provide these functions
• There are many different ways in which the network layers can be designed
  o The two most important network models are the Open Systems Interconnection
  Reference (OSI) model and the Internet model

Question 20

What are the two most important Network Models?

Answer 20

Open Systems Interconnection
Reference (OSI) model and the Internet model

Question 21

Open Systems Interconnection
Reference (OSI) model

Answer 21

• produced in 1984 by the Open System Interconnection
  Subcommittee of the International Organization for Standardization (ISO)
• The OSI model is the most referred to network model

Question 22

7 Layers of the OSI Model (Part 1)

Answer 22

Layer 1: Physical Layer
o The physical layer is concerned primarily with transmitting data bits (zeros or ones)
over a communication circuit
Layer 2: Data Link Layer
o The data link layer manages the physical transmission circuit in layer 1
o Transforms it into a circuit that is free of transmission errors as far as layers above are
concerned
o Solve the problems caused by damaged, lost, or duplicate messages so the succeeding layers are shielded from transmission errors
Layer 3: Network Layer
o The network layer performs routing

Question 23

7 Layers of the OSI Model (Part 3)

Answer 23

Layer 4: Transport Layer
o The transport layer deals with end-to-end issues, such as procedures for entering and
departing from the network
o Maintains logical connections
o Makes sure that packets are received
Layer 5: Session Layer
o The session layer is responsible for managing and structuring all sessions
o Handles session accounting so the correct party receives the bill

Question 24

7 Layers of the OSI Model (Part 3)

Answer 24

Layer 6: Presentation Layer
o The presentation layer formats the data for presentation to the user
o Its job is to accommodate different interfaces on different computers so the
application program need not worry about them
Layer 7: Application Layer
o The application layer is the end user’s access to the network
o The primary purpose is to provide a set of utilities for application programs

Question 25

Internet Model

Answer 25

* The network model that dominates current hardware and software is a more simple five-layer Internet model * Evolved from the work of thousands of people who developed pieces of the Internet * The Internet model has never been formally defined

Question 26

Five Layers of the Internet Model (Part 1)

Answer 26

Layer 1: The Physical Layer o The physical layer in the Internet model is the physical connection between the sender and receiver o The physical layer includes all the hardware devices and physical media Layer 2: The Data Link Layer o The data link layer is responsible for moving a message from one computer to the next computer in the network path from the sender to the receiver 1. Controls the physical layer by deciding when to transmit messages over the media 2. Formats the messages by indicating where they start and end 3. Detects and may correct any errors that have occurred during transmission

Question 27

Five Layers of the Internet Model (Part 2)

Answer 27

Layer 3: Network Layer o The network layer performs routing o it can find the address of that computer if it does not already know it Layer 4:The Transport Layer o It is responsible for linking the application layer software to the network and establishing end-to-end connections o It is responsible for breaking long messages into several smaller messages and then recombining the smaller messages back into the original larger message at the receiving end Layer 5: Application Layer o The application layer is the application software used by the network user

Question 28

Groups of Layers

Answer 28

The layers in the Internet are often so closely coupled that decisions in one layer impose certain requirements on other layers * The data link layer and the physical layer are closely tied(often called hardware layer) The transport and network layers are so closely coupled that sometimes these layers are called the internetwork layers

Question 29

Message Transmission using layers

Answer 29

* Each computer in the network has software that operates at each of the layers and performs the functions required by those layers * Each layer in the network uses a formal language, or protocol, that is simply a set of rules that define what the layer will do * In general, all messages sent in a network pass through all layers * All layers except the physical layer create a new Protocol Data Unit (PDU) as the message passes through them

Question 30

Message Transmission using layers

Answer 30

1. Application layer 2. Transport Layer 3. Network Layer 4. Data Link layer 5. Physical Layer

Question 31

Application Layer (1)

Answer 31

* The user creates a message at the application layer using a Web browser by clicking on a link * The browser translates the user’s message into HTTP * The Web browser fills in the necessary information in the HTTP packet, drops the user’s request inside the packet, then passes the HTTP packet to the transport layer

Question 32

Transport Layer

Answer 32

* The transport layer on the Internet uses a protocol called TCP (transmission control protocol) * TCP is responsible for breaking large files into smaller packets and for opening a connection to the server for the transfer of a large set of packets * The transport layer places the HTTP packet inside a TCP PDU fills in the information needed by the TCP segment, and passes the TCP segment to the network layer

Question 33

Network Layer

Answer 33

* The network layer on the Internet uses a protocol called IP (Internet Protocol) * IP selects the next stop on the message’s route through the network * It places the TCP segment inside an IP PUD and passes the IP packet to the data link layer

Question 34

Data Link Layer

Answer 34

* The data link layer uses a protocol called Ethernet to connect to the Internet * The data link layer formats the message with start and stop markers, adds error checks information * It instructs the physical hardware to transmit the Ethernet frame

Question 35

Physical Layer

Answer 35

* The physical layer in this case is network cable connecting your computer to the rest of the network * The computer will take the Ethernet frame and send it as a series of electrical pulses through your cable to the server

Question 36

Pros and Cons of using Layers

Answer 36

* There are many different software packages and many different PDUs that operate at different layers to successfully transfer a message * For communication to be successful, each layer in one computer must be able to communicate with its matching layer in the other computer * The major disadvantage of using a layered network model is that it is somewhat inefficient

Question 37

Network Standards

Answer 37

* The primary reason for standards is to ensure that hardware and software produced by different vendors can work together * Standards also mean that customers are not locked into one vendor * The use of standards makes it much easier to develop software and hardware that link different networks because software and hardware can be developed one layer at a time

Question 38

List the two types of standard

Answer 38

De jure and De facto

Question 39

De jure

Answer 39

Developed by an official industry or a government body and is often called a formal standard o Typically take several years to develop 1. Specifications 2. Identification of choices 3. Acceptance

Question 40

De facto

Answer 40

Emerge in the marketplace and are supported by several vendors but have no official standing

Question 41

What are the Standard Making Organizations?

Answer 41

* International Organization for Standardization * International Telecommunications Union-Telecommunications Group(ITU‑T) * American National Standards Institute (ANSI) * Institute of Electrical and Electronics Engineers (IEEE) * Internet Engineering Task Force (IETF)