The document is a class note that discusses various topics related to data communication and computer networks. It defines data communication and its components. It also defines common network devices and concepts such as nodes, computer networks (PAN, LAN, MAN, WAN), Network Interface Card (NIC), MAC address, ports, hubs, switches, routers, bridges, repeaters, gateways, and the OSI and TCP/IP models.

1. Class Note
Date: 07/05/2021
Md. Abdur Rahim khan
ID: 1925102512
Course Title: Data Communications
Course Code: Cse-313

2. 1. What is data communication?
Ans: Data communication are the exchange of data between two devices vai some form of
transmission medium of such as a wire cable. (Tutorials Point )
Components of data communication:
(https://ecomputernotes.com/computernetworkingnotes/communication-networks/what-is-data-
communication)
a) Message
b) Sender
c) Receiver
d) Transmission medium
e) Protocol
1. Message: It is the information or data to be communicated. It can consist of text,
numbers, pictures, sound or video or any combination of these.
2. Sender: It is the device/computer that generates and sends that message.
3. Receiver: It is the device or computer that receives the message. The location of
receiver computer is generally different from the sender computer. The distance
between sender and receiver depends upon the types of network used in between.

3. 4. Medium: It is the channel or physical path through which the message is carried
from sender to the receiver. The medium can be wired like twisted pair wire, coaxial
cable, fiber-optic cable or wireless like laser, radio waves, and microwaves.
5. Protocol: It is a set of rules that govern the communication between the devices.
Both sender and receiver follow same protocols to communicate with each other.
2. What is Node?
Ans: A node is a connection point inside a network that can receive, send, create, or store
data.
যখন দুই বা তততাধিক Device wire বা wireless ধবহীন একটি Network
communicate কতে, তখন প্রধতটি Device কক individually এতককটি
Node বতে।
অথবা: Internet Connection ছাড়া যখন ককান PC Data বা ধেত ার্স্
গ্রহন কতে, তখন তাতক Node বতে।
3. Types of Computer Networks :
(https://www.guru99.com/types-of-computer-network.html)
a) PAN
b) LAN
c) MAN
d) WAN
a)PAN(personal Area Network): PAN is a computer network
formed around a person. it can be used for establishing
communication among these personal devices for connecting to a
digital network and the internet.
Characteristics of PAN :
1. PAN includesmobile devices,tablet,andlaptop.
2. It can be wirelesslyconnectedtothe internetcalledWPAN.

4. Advantages of PAN :
1. PAN networksare relativelysecureandsafe
2. It offersonlyshort-range solutionuptotenmeters
3. Strictlyrestrictedtoa small area
Disadvantages of PAN :
1. It may establishabadconnectiontoothernetworksat the same radiobands.
2. Distance limits.
b) LAN ( Local Area Network): A Local Area Network (LAN) is a group of
computer and peripheral devices which are connected in a limited area such as school,
laboratory, home, and office building.
Characteristics of LAN:
1. LAN isa private network,soanoutside regulatorybodynevercontrolsit.
2. LAN operatesata relativelyhigherspeedcompared tootherWAN systems.
Advantages of LAN:
1. Data of all networkuserscanbe storedona single harddiskof the servercomputer.
2. LAN operatesata relativelyhigherspeedcomparedtootherWAN systems.
3. You can easilytransferdataand messagesovernetworkedcomputers.
4. Local Area Networkoffersthe facilitytoshare asingle internetconnectionamongall the LAN
users.
Disadvantages of LAN:
1. LANsare restrictedinsize theycoverasmall area like asingle office,single buildingora group
of nearbybuildings.
2. The initial setup costs of installing Local Area Networks is high because there is special software
required to make a server. Also, communication devices like an ethernet cable, switches, hubs,
routers, cables are costly.

5. MAN (Metropolitan Area Network): A Metropolitan Area Network (MAN)
is consisting of a computer network across an entire city, college campus, or a
small region. It allows you to cover an area fromseveral miles to tens of miles.
Characteristics of MAN:
1. It mostly covers towns and cities in a maximum 50 km range
2. Mostly used medium is optical fibers, cables
Advantages of MAN:
1. It offers fast communication using high-speed carriers, like fiber optic
cables.
2. The dual bus in MAN network provides support to transmit data in both
directions concurrently.
3. A MAN network mostly includes some areas of a city or an entire city.
Disadvantages of MAN:
1. You need more cable to establish MAN connection from one place to
another.
2. In MAN network it is tough to make the system secure from hackers

6. WAN (Wide Area Network): WAN (Wide Area Network) is another
important computer network that which is spread across a large geographical
area. It is mostly limited to an enterprise or an organization.
Characteristics of LAN:
1. It connect devices that are separated by a broader geographical area than a LAN
2. It use serial connection.
Advantages of WAN:
1. WAN helpsyoutocover a largergeographical area.Therefore businessofficessituatedatlonger
distancescaneasilycommunicate.
2. It use serial connection.
Disadvantage of WAN:
1. The initial setup cost of investment is very high.
2. It is difficult to maintain the WAN network. You need skilled technicians and
network administrators.
3. Offers lower security compared to other types of networks.

7. 4.What is (NetworkInterface card) NIC?
Ans: A network interface card is a Hardwaredevicethat is used to connect a
node on to a network.
Characteristics of (Network interface card) NIC:
1. Nic হল এক ধরনের Circuite board, যেটি কম্পিউটারনক
যেটওয়ানক
ে র সানে েুক্ত করার জেয কম্পিউটানর স্থাপে করা হয় ।
2. এই কানড
ে র সানথ একটি Rj 45 Connector থানক । এখানে Network
cable েুক্ত করা হয়।
3. এটি Computer এর motherboard এর সানথ েুক্ত করা হয় এবং এটি
OSI এবং TCP/IP এর Physical Layer এ কাজ কনর এবং Physical
Address প্রদাে কনর।
5. What is (MediaAccess Control Address) MAC?
Ans: A MAC address is a hardwareidentification number that uniquely
identifies each device on a network.
MediaAccess Control (MAC) Address হল প্রম্পেটি ম্পডভাইনসর একটি ইউম্পেক
Address, োর মাধযনম একটি ম্পডভাইস অেয একটি ম্পডভাইসনক ম্পিেনে পানর।
MAC Address 48-bit এর হয় ।
Types of Addressing:

8. 1. Physical Addressing
2. Logical Addressing
1. Physical Address: A physical address is a memory address that is represented
in the form of a binary number on the address bus circuitry in order to enable the data bus to
access a particular storage cell of main memory.
2. Logical Address: A logical address or virtual address is an address that is generated
by the CPU during program execution. The logical address is used as a reference to access the
physical address.
6. What is Port? (https://www.cloudflare.com/learning/network-layer/what-is-a-computer-port/)
Ans:A port is a virtual point where network connections start
and end.
The different port numbers:
1. Ports 20 and 21: File Transfer Protocol (FTP).
2. Port 22: Secure Shell (SSH).
3. Port 25: Simple Mail Transfer Protocol (SMTP).
4. Port 53: Domain Name System (DNS).
5. Port 80: Hypertext Transfer Protocol (HTTP).
6. Port 123: Network Time Protocol (NTP).
7. Port 179: Border Gateway Protocol (BGP).

9. 8. Port 443: HTTP Secure (HTTPS).
9. Port 23: Teletype Network(Telnet)
10. Port 110: Post office protocol 3(POP3).
11. Port 144: Internet message access protocol
4(IMAP4).
12. Port 67: Dynamic Host Configuration
Protocol(DHCP/BOOTPS).
13. Port 69: Trivial File Transfer Protocol(TFTP).
14. Port 161: Simple Network Management Protocol(SNMP).
15. Port 520: performance improvement plan(PIP).
16. Port 143: Internet Message Access Protocol(IMAP)
17. Port 513: Internet Port.
18. Port 110: Electronic mail port.
7. What is Hub?( https://www.geeksforgeeks.org/network-devices-hub-repeater-
bridge-switch-router-gateways/)
Ans: A network hub is a device that allows multiple computers to communicate with each
other over a network.
Hub হে এমন একটি Device যাে মািযতম প্রধতটি ধিভাই তক এক াতে যুক্ত কো
হয় । HUB এে মািযতম ককান ধিভাই এ Data send কেতে তা প্রধতটি Device

10. a পাঠায় এবং কয Device এ Data পাঠাতনা হয় শুিু ক ই Device-ই Data গ্রহন
কতে এবং বাধক Device গুতো ক টা গ্রহন কতে না।
8. What is Switch?
Ans:A switch is a device in a computer network that connects
other devices together. Multiple data cables are plugged into a
switch to enable communication between different networked
devices.
Switch হে এমন একটি Device যাে মািযতম প্রধতটি ধিভাই তক এক াতে যুক্ত
কো হয় । Switch এে মািযতম ককান ধিভাই এ Data send কেতে তা প্রধতটি
Device এ Send না কতে ো ধে টাতগ্ট Device Send কতে ।
9. What is Router?
Ans: A router is a device like a switch that routes data packets based on their
IP addresses. Router is mainly a Network Layer device.
Router এমে একটি Device ো Data Route বা Forward কনর ম্পেম্পদে ষ্ট IP Address এ
Send কনর। Router এ যকাে ডাটা পাঠানো হনল Router ো ম্পিল্টার কনর ম্পেম্পদে ষ্ট
Network এ Send কনর। Router Mac এবং IP Address দুনটাই ম্পডনটক্ট করনে
পানর।
10. What is Bridge?
Ans: A bridge operates at data link layer. A bridge is a repeater, with add on the
functionality of filtering content by reading the MAC addresses of source and
destination.

11. Bridge হল এমে একটি Device োর মাধযনম দুইটি Network যক সংেুক্ত
কনর কাজ করা হয়। আবার একটা বড় Network যক য াট য াট অংনে
ভাগ কনর Bridge এর মাধযনম Network গুম্পলনক সংেুক্ত কনরও কাজ করা
োয়।
11. What Is Repeater?
ANS: A repeater operates at the physical layer. Its job is to
regenerate the signal over the same network before the signal
becomes too weak or corrupted so as to extend the length to
which the signal can be transmitted over the same network.
12. What is Gateway?
Ans: A gateway, as the name suggests, is a passage to connect two networks
together that may work upon different networking models.
13. What is Brouter?
Ans: It is also known as bridging router is a device which combines features of both
bridge and router. It can work either at data link layer or at network layer.
14. What is OSI (Open System Interconnection) Model?(https://www.geeksforgeeks.org/layers -
of-osi-model/)
Ans: The OSI Model (Open Systems Interconnection Model) is a conceptual
framework used to describe the functions of a networking system. The OSI model
characterizes computing functions into a universal set of rules and requirements in
order to support interoperability between different products and software.

12. 7 Layers of the OSI Model:
1. Physical Layer (Layer 1) : The lowest layer of the OSI reference model
is the physical layer. It is responsible for transmitting individual bits from one node to
the next. When receiving data, this layer will get the signal received and convert it into
0s and 1s and send them to the Data Link layer.
2. Data Link Layer (DLL) (Layer 2) : The data link layer is responsible for the
node to node delivery of the message. When a packet arrives in a network, it is the
responsibility of DLL to transmit it to the Host using its MAC address.

13. 3. Network Layer (Layer 3) : Network layer works for the transmission of
data from one host to the other located in different networks.The sender & receiver’s
IP address are placed in the header by the network layer.
4. Transport Layer (Layer 4) : Transport layer provides services to
application layer and takes services from network layer. The transport layer also
provides the acknowledgement of the successful data transmission and re-transmits
the data if an error is found.
5. Session Layer (Layer 5) : This layer allows a process to add checkpoints
which are considered as synchronization points into the data. These
synchronization pointhelp to identify the error so that the data is re-synchronized
properly, and ends of the messages arenot cut prematurely and data loss is
avoided.
6. Presentation Layer (Layer 6) : Presentation layer is also called
the Translation layer.The data from the application layer is extracted here
and manipulated as per the required format to transmit over the network.
7. Application Layer (Layer 7) : At the very top of the OSI
Reference Model stack of layers, we find Application layer which is
implemented by the network applications. These applications produce the
data, which has to be transferred over the network.

14. 15. What Is the TCP/IP Model? (https://www.guru99.com/tcp-ip-model.html)
Ans: TCP/IP stands for Transmission Control Protocol/ Internet Protocol.
TCP/IP Model helps you to determine how a specific computer should be connected to
the internet and how data should be transmitted between them. It helps you to create a
virtual network when multiple computer networks are connected together. The purpose
of TCP/IP model is to allow communication over large distances.
Four Layers of TCP/IP model:

15. 1. Application Layer : Application layer interacts with an application
program, which is the highest level of OSI model. The application layer is the
OSI layer, which is closest to the end-user. It means the OSI application layer
allows users to interact with other software application.
2. Transport Layer: The transport layer also offers an
acknowledgmentof the successfuldata transmission and sends the next
data in case no errors occurred.TCP is the best-known example of the
transport layer.
3. Internet Layer: The Internet layer offers the functional and
proceduralmethod for transferring variable length data sequencesfrom
one node to another with the help of various networks. The main work of
this layer is to send the packets from any network, and any computerstill
they reach the destination irrespective of the route they take.
4. The Network Interface Layer: Network Interface Layer is
this layer of the four-layer TCP/IP model.This layer is also called a network
access layer. It helps you to defines details of how data should be sent
using the network.

16. 13. What is IP Address? ( https://toshost.com/a/ip-address-%E0%A6%95%E0%A6%BF-ip-
address-%E0%A6%95%E0%A6%BF%E0%A6%AD%E0%A6%BE%E0%A6%AC%E0%A7%87 -
%E0%A6%95%E0%A6%BE%E0%A6%9C-%E0%A6%95%E0%A6%B0%E0%A7%87)
Ans: An IP address is a unique address that identifies a device on the internet or a
local network. IP stands for "Internet Protocol," which is the set of rules governing the
format of data sent via the internet or local network.
Types of IP:
a) IPV4-32 bit
b) IPV6-128 bit
a)IPV4
8-Bit 8-Bit 8-Bit 8-Bit =32-Bit
Class of IP:
IP Address IP Rang Possible Noof Host
Calss A 0-126 16,777,214
Class B 128-191 65,534
Class C 192-223 254
Class D 224-239
Class E 240-255
Class A:
Network Host Host Host

17. 8 Bit 8 Bit 8 Bit 8 Bit
Class B:
Network Network Host Host
8 Bit 8 Bit 8 Bit 8 Bit
Class C:
Network Network Network Host
8 Bit 8 Bit 8 Bit 8 Bit
Private and public IP
Address(https://www.geeksforgeeks.org/difference-between-private-and-
public-ip-addresses/)
1.Private IP Address.
2. Public IP Address.

18. 1. Private IP Address: Private IP address of a system is the IP
address which is used to communicate within the same network.
Using private IP data or information can be sent or received
within the same network.
The Private Address Blocks Area:
10.0.0.0 To 10.255.255.255
172.16.0.0 To 172.31.255.255
192.168.0.0 To 192.168.255.255
2. Public IP Address: Public IP address of a system is the
IP address which is used to communicate outside the network.
Public IP address is basically assigned by the ISP (Internet
Service Provider).
The Public IP Address Blocks Area: Besides private IP
addresses, rest are public IP address.

19. Thank You Very Much