1. Introduction to Computer
Networks
Networks connect computers to share information and resources. This
presentation explores the fundamentals of computer networking, from historical
development to modern applications, protocols, and architecture models.
2. Network Definition & Historical
Development
What is a Network?
"A group of computers & other
devices such as printers,
workstations, and servers that are
linked together to share information
and resources."
Networking refers to the concepts of
connected computers and devices
sharing information, resources, or
both.
Historical Development
In the mid-1960s, mainframe
computers were standalone devices.
The Advanced Research Projects
Agency (ARPA) developed ARPANET in
1967 to connect research computers.
By 1969, ARPANET connected four
nodes (UCLA, UCSB, SRI, University of
Utah) using Interface Message
Processors (IMPs) and Network
Control Protocol (NCP).
4. Uses of Computer Networks
Resource Sharing
• File sharing between network users
• Hardware sharing (printers, drives)
• Program sharing (applications)
• Internet connection sharing
Communication
• Electronic mail
• Newsgroups
• Video conferencing
• Person-to-person communication
Data Management
• Centralized data storage
• User access control
• Data security
• Information sharing
Entertainment & Home Use
• Internet access
• Interactive entertainment
• Electronic commerce
• Access to remote information
5. Network Design Criteria
Performance
Measured by transit time (message travel time) and response time (time
between inquiry and response). Also affected by software efficiency, number of
users, and hardware capability.
Reliability
Determines frequency of network failures. More failures mean less reliability.
Critical for business operations and data integrity.
Scalability
Network's ability to grow and accommodate new users and technologies
without performance degradation. Essential for evolving organizations.
Security
Protection of data from unauthorized access. Includes authentication,
encryption, and access controls to prevent eavesdropping and data
alteration.
Routing
Selecting optimal paths for data transmission based on cost and time.
Various algorithms determine the most efficient routes.
Flow Control
Prevents receiver overflow when sender produces data faster than
receiver can process it. Ensures smooth data transmission.
6. Data Transmission & Service Types
Data Transmission Modes Connection-Oriented vs. Connectionless Services
Connection-Oriented
• Establishes connection before data transfer
• Follows sequence: connect, send, release
• More reliable with error checking
• Example: TCP protocol
Connectionless
• No connection establishment required
• Similar to postal service
• No delivery guarantee
• Example: UDP protocol
Service Primitives: LISTEN, CONNECT, RECEIVE, SEND, and DISCONNECT operations enable communication between layers.
7. •Network: A group of connected computers and devices that can communicate and share data with each other.
•Node: Any device that can send, receive, or forward data in a network. This includes laptops, mobiles, printers, earbuds, servers, etc.
•Networking Devices: Devices that manage and support networking functions. This includes routers, switches, hubs, and access points.
•Transmission Media: The physical or wireless medium through which data travels between devices. Wired media: Ethernet cables, optical
fiber. Wireless media: Wi-Fi, Bluetooth, infrared
•Service Provider Networks: Networks offered by external providers that allow users or organizations to lease network access and
capabilities. This includes internet providers, mobile carriers, etc.
•IP Address: IP Address (Internet Protocol Address) is a unique numerical label assigned to each device connected to a computer network that uses the Internet
Protocol for communication.
Basic Terminologies of Computer Networks
•IPv4 (e.g., 192.168.1.1) – 32-bit address.
•IPv6 (e.g., 2001:0db8:85a3::8a2e:0370:7334) – 128-bit address
8. Computer Network falls under these broad Categories:
•Client-Server Architecture: It is a type of Computer Network Architecture in which Nodes can be Servers or Clients.
Here, the server node can manage the Client Node Behavior.
•Peer-to-Peer Architecture: There is not any concept of a Central Server. Each device is free for working as either
client or server.
Types of Computer Network Architecture
Network Devices
9. •Router
A router connects multiple networks together and directs data packets between them. It operates at the network layer (Layer 3)
of the OSI model and can assign IP addresses and manage traffic.
•Hub
A hub is a basic networking device that connects multiple computers in a LAN and broadcasts data to all connected devices,
regardless of the destination. It operates at the physical layer (Layer 1).
•Bridge
A bridge connects two or more LAN segments, filtering and forwarding data based on MAC addresses. It works at the data link
layer (Layer 2) and reduces network traffic by dividing collision domains.
•Wireless Router
A wireless router combines the functionality of a router and an access point, allowing wireless devices to connect to a network. It
routes traffic and provides Wi-Fi access.
•Switch
A switch connects devices in a LAN and uses MAC addresses to forward data to the correct destination. It operates at the data
link layer (Layer 2) and offers better performance than a hub.
•Wireless Bridge
A wireless bridge connects two wired networks wirelessly. It extends the range of a wired network by connecting segments
without physical cabling.
Network Devices
https://www.youtube.com/watch?v=QvBbg7oaeHE
10. Network Topology
The Network Topology is the layout arrangement of the different devices in a
network. Some types of network topologies are,
•Bus Topology: all devices are connected to a single central cable called a bus.
•Star Topology: all devices are connected to a central node called hub or switch.
•Ring Topology: devices are connected in a circular loop with each device connected to two
others. Data travels in one direction (or sometimes both) passing through each device until it
reaches its destination.
•Mesh Topology: device is connected to every other device in the network.
•Tree Topology: Tree topology is the combination of star and bus topology. Tree topology is good
for organizing large networks and allows for easy expansion.
•Hybrid Topology: Hybrid topology is the combination of two or more different topologies (like
star and mesh).
11. OSI Model
OSI stands for Open Systems Interconnection. It is a reference model that specifies standards for communications protocols
and also the functionalities of each layer. The OSI has been developed by the International Organization For Standardization
and it is 7 layer architecture. Each layer of OSI has different functions and each layer has to follow different protocols. The 7
layers are as follows:
•Physical Layer
•Data link Layer
•Network Layer
•Transport Layer
•Session Layer
•Presentation Layer
•Application Layer
12. OSI Reference Model
The Open Systems Interconnection (OSI) model, released by ISO in 1984, is a seven-layer framework that standardizes
network communication processes.
Application (7)
User interface, file transfer, email (FTP, HTTP, SMTP)
Presentation (6)
Data formatting, encryption, compression (ASCII, JPEG, MPEG)
Session (5)
Dialog control, synchronization
Transport (4)
End-to-end connections, reliability (TCP, UDP)
Network (3)
Routing, addressing, packet forwarding (IP)
Data Link (2)
Media access, error detection (Ethernet, WiFi)
Physical (1)
Bits transmission, cables, signals
13. OSI Model Layers
Created by the International Organization for
Standardization (ISO) towards the end of the 1970s, the OSI
model simplifies the intricate task of communication
between computers by segmenting it into seven unique
layers. Each layer is assigned a particular role and interacts
with the layers immediately adjacent to it.
SSL (Secure Sockets Layer)
TLS (Transport Layer Security)
TCP (Transmission Control Protocol)
UDP (User Datagram Protocol)
Internet Control Message Protocol (ICMP)
14. •A MAC address is a unique hardware identity assigned to each device on a network to distinguish it
from others. It operates at the Data Link layer and is used for local network communication.
•An IP Address is a digital identifier given to each device on a network that communicates using the
Internet Protocol (IP). It operates at the Network layer and is used to identify devices across different
networks and route data.
Data Link Layer- Interview Questions
Physical Layer- Interview Questions
•Coaxial cables:
• Resistant to electromagnetic interference
• Suitable for cable TV and Ethernet
• Bulkier and less flexible
•Fiber optic cables:
• Transmit data via light
• High speeds, long distances
• No electromagnetic interference
• Ideal for backbone networks and long-distance communication
•Twisted pair cables (Ethernet cables):
• Common in LANs and telephone connections
• Available in shielded and unshielded versions
• Variable electromagnetic interference vulnerability
• Different speeds and distance capabilities
How does the Data Link Layer handle error detection and correction?
15. Network Layer (Layer 3)
The Network Layer is responsible for data packet routing, logical addressing, and the handling of routing
protocols. It manages the delivery of packets from the source to the destination across multiple networks
(routing).
Network Layer Interview Questions
1.Describe how a router works at the Network Layer to route data.
A router examines the destination IP address in a packet’s header, uses routing tables to determine the best
route for the packet, and forwards it toward its destination through the appropriate interface. It operates at the
Network Layer, directing traffic based on IP addresses.
2.What is the significance of routing protocols in the Network Layer?
Routing protocols like OSPF( Open Shortest Path First), BGP (Border Gateway Protocol) enable routers to build and
maintain routing tables. They dynamically communicate network topology changes and determine the most
efficient path for data packet delivery across different networks, ensuring efficient and reliable data routing.
•Unicasting: Sending data from one
sender to one specific receiver.
•Multicasting: Sending data from one
sender to multiple specified receivers.
•Broadcasting: Sending data from one
sender to all possible receivers in the
network segment.
•The Internet Protocol (IP) is a crucial protocol that guides data packets from their source to their designated destination
through multiple networks, leveraging IP addresses to determine their path.
•Internet Control Message Protocol (ICMP) is used to send diagnostic messages and report error, helping manage and
troubleshoot network issues.
•Internet Group Management Protocol (IGMP) manages multicast group memberships, allowing routers to efficiently send
multicasting data to groups of interested receivers.
16. Network Protocols
A protocol is a set of rules or algorithms which define the way how two entities can communicate across the network
and there exists a different protocol defined at each layer of the OSI model. A few such protocols are TCP, IP, UDP, ARP,
DHCP, FTP, and so on.
•Transmission Control Protocol/Internet Protocol (TCP/IP): TCP/IP is the foundational protocol suite of the internet,
enabling reliable communication. TCP Ensures data is delivered reliably and in order and IP routes data packets to their
destination based on IP addresses.
•Hypertext Transfer Protocol (HTTP) and HTTPS: HTTP and HTTPS protocols used for transmitting web pages. In
HTTP communication is unsecured and in HTTPS secured communication using SSL/TLS encryption.
•Simple Mail Transfer Protocol (SMTP): SMTP protocol used to send email. SMTP protocol works with other protocols
like POP3 and IMAP for email retrieval.
•File Transfer Protocol (FTP): FTP protocol used for transferring files between computers. Includes commands for
uploading, downloading, and managing files on a remote server.
•Dynamic Host Configuration Protocol (DHCP): DHCP protocol automatically assigns IP addresses to devices on a
network. Reduces manual configuration and IP address conflicts.
•Domain Name System (DNS): DNS Translates human-friendly domain names into IP addresses. Ensures seamless
navigation on the internet.
17. Unique Identifiers of Network
Hostname: Each device in the network is associated with a unique device name known as Hostname.
IP Address (Internet Protocol address): Also known as the Logical Address, the IP Address is the network
address of the system across the network. To identify each device in the world-wide-web, the Internet Assigned
Numbers Authority (IANA) assigns an IPV4 (Version 4) address as a unique identifier to each device on the
Internet.
The length of an IPv4 address is 32 bits, hence, we have 232
IP addresses available. The length of an IPv6
address is 128 bits.
In Windows Type “ipconfig” in the command prompt and press ‘Enter’, this gives us the IP address of the
device. For Linux, Type “ifconfig” in the terminal and press ‘Enter’ this gives us the IP address of the device.
MAC Address (Media Access Control address): Also known as physical address, the MAC Address is the unique
identifier of each host and is associated with its NIC (Network Interface Card). A MAC address is assigned to the
NIC at the time of manufacturing. The length of the MAC address is: 12-nibble/ 6 bytes/ 48 bits Type “ipconfig/all”
in the command prompt and press ‘Enter’, this gives us the MAC address.
Port: A port can be referred to as a logical channel through which data can be sent/received to an application. Any
host may have multiple applications running, and each of these applications is identified using the port number
on which they are running.
18. Protocol Hierarchies
Networks use layered protocols where each layer offers services to higher layers
while hiding implementation details. This concept is similar to information hiding
and object-oriented programming.
A protocol is an agreement between communicating parties on how
communication proceeds. Processes in corresponding layers on different machines
are called peers.
Key Concepts
• Virtual communication occurs between peer layers
• Physical communication happens only at the lowest layer
• Each layer adds headers to messages as they pass down
• Headers contain control information for peer layers
• A set of layers and protocols is called a Network Architecture
• A list of protocols used by a system is called a protocol stack
20. TCP/IP Model
TCP/IP (Transmission Control Protocol/Internet Protocol) was developed by the Department of Defense's Project
Research Agency (ARPA) and is the foundation of the modern Internet.
1
Application Layer
Provides network services to applications. Includes protocols like TELNET, FTP, SMTP, and DNS for various
communication functions.
2
Transport Layer
Handles data transmission paths, multiplexing, and segmentation. Ensures proper sequencing of packets
and adds header information.
3
Internet Layer
Enables packet routing across networks. Uses IP to deliver packets independently to their destination,
regardless of order.
4
Host-to-Network Layer
Lowest layer that connects hosts to the network. Varies between different network types and hardware
configurations.
Advantages of TCP/IP
• Operates independently
• Highly scalable
• Client/server architecture
• Supports multiple routing protocols
• Enables computer-to-computer connections
Limitations
• Transport layer doesn't guarantee packet delivery
• Limited to specific applications
• Difficult protocol replacement
• Services, interfaces, and protocols not clearly separated
21. Facebook Data Center
Fabric – Network
Architecture
Term Meaning
Leaf Switch Connects to servers; handles
traffic to/from spines
Spine Switch
Aggregates traffic from
leaves; connects to all leaves
East-West
Server-to-server
communication (intra-DC)
North-South
External-to-server or client-
to-DC traffic
eBGP
Routing protocol used
between modules/devices
(even internally)
Fault Domain
A module or unit that can
fail without affecting the
entire infrastructure
22. Traditional WAN SD-WAN
Routes traffic through MPLS/private links
Routes dynamically over MPLS,
broadband, LTE
Static and complex configuration Centralized control with easy policies
Expensive per Mbps
Cost-effective using internet + hybrid
routing
No real-time visibility Full analytics, QoS, and application
performance
SD-WAN (Software-Defined Wide Area Network)
SD-WAN is a modern networking technology that uses software-based controllers to intelligently manage wide-area networks (WANs). It replaces or augments traditional
WANs (like MPLS) by using the internet and multiple network connections (broadband, LTE, fiber) more efficiently and securely.
Editor's Notes
#3:Network: A network is a collection of computers and devices that are connected together to enable communication and data exchange.
Nodes: Nodes are devices that are connected to a network. These can include computers, Servers, Printers, Routers, Switches and other devices.
Protocol: A protocol is a set of rules and standards that govern how data is transmitted over a network. Examples of protocols include TCP/IP, HTTP and FTP.
Topology: Network topology refers to the physical and logical arrangement of nodes on a network. The common network topologies include bus, star, ring, mesh and tree.
Service Provider Networks: These types of Networks give permission to take Network Capacity and Functionality on lease from the Provider. Service Provider Networks include Wireless Communications, Data Carriers, etc.
IP Address: An IP address is a unique numerical identifier that is assigned to every device on a network. IP addresses are used to identify devices and enable communication between them.
DNS: The Domain Name System (DNS) is a protocol that is used to translate human-readable domain names (such as www.google.com) into IP addresses that computers can understand.
Firewall: A firewall is a security device that is used to monitor and control incoming and outgoing network traffic. Firewalls are used to protect networks from unauthorized access and other security threats.
