, NotesNeo
Unit 1 : Introduction to Computer Networks
Syllabus :
Introduction: Data communication, Components, Computer networks and its
historical development, distributed processing, Internet.
Network Models: OSI model and TCP/IP Model.
Physical Layer: physical layer functions, Data Representation, Simplex, Half Duplex
and Full Duplex Transmission, Modulation and Multiplexing, Packet and circuit
switching, Transmission media, Topologies, connectionless and connection-oriented
services.
Data Link Layer: Data link layer functions and services, MAC Addressing, Framing,
Stop and Wait, Go back – N ARQ, Selective Repeat ARQ, Sliding Window Protocol.
Section 1 : Introduction
1.1 Data Communication
Definition
● Data communications is simply the exchange of data between two devices
via some form of transmission medium (e.g., wire cable) to share resources
with each other.
Importance
● Facilitates resource sharing and coordination.
● Enhances faster communication.
● Access to information.
● Supports business operations and personal communications.
● Enables the operation of information systems and the Internet.
Components of Data Communication System
1. Sender: Device that sends the data message.
2. Receiver: Device that receives the data message.
3. Message: Data to be communicated.
4. Transmission Medium: Physical path by which a message travels from
sender to receiver.
5. Protocol: Set of rules governing data communications.
1
, NotesNeo
1.2 Computer Networks
Definition
● A computer network is a group of interconnected computers and devices that
communicate and share resources with each other through various
transmission media, such as wires, optical fibers, or wireless links.
● These devices can include computers, servers, routers, switches, and other
networked devices.
● The primary goal of a computer network is to facilitate resource sharing
among different devices.
Objectives of Computer Networks
● Resource Sharing: Enables multiple users to share hardware (e.g., printers),
software (e.g., applications), and data files.
● Communication: Facilitates communication between users through email,
instant messaging, video conferencing, etc.
● Connectivity: Connect various devices within an organization or across the
world to create a unified system for communication and resource sharing.
● Efficiency: Enhances productivity by allowing for the centralized
management and streamlined access to resources.
● Scalability: Allows for easy expansion of the network as the number of users
or devices increases.
Historical Development of Computer Networks
● 1960s - ARPANET: The first operational packet-switching network, funded by
the U.S. Department of Defense.
● 1970s - Ethernet: Development of the Ethernet protocol by Robert Metcalfe;
became a standard for LANs.
● 1980s - TCP/IP: Adoption of TCP/IP protocols, making the Internet protocol
suite the standard for networking.
● 1990s - The World Wide Web: Developed by Tim Berners-Lee; revolutionized
access to information and internet usage.
Components of Computer Networks
Computer network components are essential parts needed to set up and operate a
network. These components can vary based on the type of network being installed.
Below are the major components required to establish a network:
1. Network Interface Card (NIC)
● NIC is a hardware component used to connect a computer to a network.
● Transfer Rate: Supports 10, 100, to 1000 Mb/s.
● MAC Address: A unique identifier encoded on the network card chip, assigned
by IEEE, and stored in PROM (Programmable Read-Only Memory).
● Types of NIC:
2
, NotesNeo
○ Wired NIC: Present inside the motherboard, using cables and
connectors for data transfer.
○ Wireless NIC: Contains an antenna for wireless connections using
radio wave technology (e.g., found in laptops).
2. Hub
● Function: A Hub is a hardware device that acts as a central connection point
for multiple devices in a network. It receives a request for data from one
device and distributes it to all connected devices.
● The process used by the Hub consumes more bandwidth and limits the
amount of communication. Nowadays, the use of hub is obsolete, and it is
replaced by more advanced computer network components such as
Switches, Routers.
● Limitation: Broadcasts data to all devices, leading to potential inefficiency
and data collisions.
3. Switch
● Function: A switch is a hardware device that is similar to a hub but more
efficient and advanced. A Switch does not broadcast the message to the
entire network like the Hub. It connects devices within a network and
forwards data only to the specific device for which it is intended.
● Advantage: Reduces unnecessary data traffic and increases the speed of the
network improving network performance.
4. Router
● Function: A router is a hardware device which is used to connect different
networks, including LANs to the internet. It is used to receive, analyze and
forward the incoming data packets to another destination network.
● Layer: A router operates at Layer 3 (Network Layer) of the OSI model.
● Routing Table: A router forwards the packet based on the information
available in the routing table.
● Path Determination: It determines the best path from available routes for
packet transmission.
● Advantages:
○ Security: Only the specified addressed device can read the transmitted
data.
○ Reliability: Network reliability is maintained even if one server fails.
○ Performance: Enhances network performance by reducing traffic load
through network segmentation.
5. Modem
● Function: A modem is a hardware device that connects a computer to the
internet over existing telephone lines. A modem is not integrated with the
3
Unit 1 : Introduction to Computer Networks
Syllabus :
Introduction: Data communication, Components, Computer networks and its
historical development, distributed processing, Internet.
Network Models: OSI model and TCP/IP Model.
Physical Layer: physical layer functions, Data Representation, Simplex, Half Duplex
and Full Duplex Transmission, Modulation and Multiplexing, Packet and circuit
switching, Transmission media, Topologies, connectionless and connection-oriented
services.
Data Link Layer: Data link layer functions and services, MAC Addressing, Framing,
Stop and Wait, Go back – N ARQ, Selective Repeat ARQ, Sliding Window Protocol.
Section 1 : Introduction
1.1 Data Communication
Definition
● Data communications is simply the exchange of data between two devices
via some form of transmission medium (e.g., wire cable) to share resources
with each other.
Importance
● Facilitates resource sharing and coordination.
● Enhances faster communication.
● Access to information.
● Supports business operations and personal communications.
● Enables the operation of information systems and the Internet.
Components of Data Communication System
1. Sender: Device that sends the data message.
2. Receiver: Device that receives the data message.
3. Message: Data to be communicated.
4. Transmission Medium: Physical path by which a message travels from
sender to receiver.
5. Protocol: Set of rules governing data communications.
1
, NotesNeo
1.2 Computer Networks
Definition
● A computer network is a group of interconnected computers and devices that
communicate and share resources with each other through various
transmission media, such as wires, optical fibers, or wireless links.
● These devices can include computers, servers, routers, switches, and other
networked devices.
● The primary goal of a computer network is to facilitate resource sharing
among different devices.
Objectives of Computer Networks
● Resource Sharing: Enables multiple users to share hardware (e.g., printers),
software (e.g., applications), and data files.
● Communication: Facilitates communication between users through email,
instant messaging, video conferencing, etc.
● Connectivity: Connect various devices within an organization or across the
world to create a unified system for communication and resource sharing.
● Efficiency: Enhances productivity by allowing for the centralized
management and streamlined access to resources.
● Scalability: Allows for easy expansion of the network as the number of users
or devices increases.
Historical Development of Computer Networks
● 1960s - ARPANET: The first operational packet-switching network, funded by
the U.S. Department of Defense.
● 1970s - Ethernet: Development of the Ethernet protocol by Robert Metcalfe;
became a standard for LANs.
● 1980s - TCP/IP: Adoption of TCP/IP protocols, making the Internet protocol
suite the standard for networking.
● 1990s - The World Wide Web: Developed by Tim Berners-Lee; revolutionized
access to information and internet usage.
Components of Computer Networks
Computer network components are essential parts needed to set up and operate a
network. These components can vary based on the type of network being installed.
Below are the major components required to establish a network:
1. Network Interface Card (NIC)
● NIC is a hardware component used to connect a computer to a network.
● Transfer Rate: Supports 10, 100, to 1000 Mb/s.
● MAC Address: A unique identifier encoded on the network card chip, assigned
by IEEE, and stored in PROM (Programmable Read-Only Memory).
● Types of NIC:
2
, NotesNeo
○ Wired NIC: Present inside the motherboard, using cables and
connectors for data transfer.
○ Wireless NIC: Contains an antenna for wireless connections using
radio wave technology (e.g., found in laptops).
2. Hub
● Function: A Hub is a hardware device that acts as a central connection point
for multiple devices in a network. It receives a request for data from one
device and distributes it to all connected devices.
● The process used by the Hub consumes more bandwidth and limits the
amount of communication. Nowadays, the use of hub is obsolete, and it is
replaced by more advanced computer network components such as
Switches, Routers.
● Limitation: Broadcasts data to all devices, leading to potential inefficiency
and data collisions.
3. Switch
● Function: A switch is a hardware device that is similar to a hub but more
efficient and advanced. A Switch does not broadcast the message to the
entire network like the Hub. It connects devices within a network and
forwards data only to the specific device for which it is intended.
● Advantage: Reduces unnecessary data traffic and increases the speed of the
network improving network performance.
4. Router
● Function: A router is a hardware device which is used to connect different
networks, including LANs to the internet. It is used to receive, analyze and
forward the incoming data packets to another destination network.
● Layer: A router operates at Layer 3 (Network Layer) of the OSI model.
● Routing Table: A router forwards the packet based on the information
available in the routing table.
● Path Determination: It determines the best path from available routes for
packet transmission.
● Advantages:
○ Security: Only the specified addressed device can read the transmitted
data.
○ Reliability: Network reliability is maintained even if one server fails.
○ Performance: Enhances network performance by reducing traffic load
through network segmentation.
5. Modem
● Function: A modem is a hardware device that connects a computer to the
internet over existing telephone lines. A modem is not integrated with the
3
