What is the OSI Model?

• An ISO standard that provides a framework for understanding and designing a network
architecture.
• Introduced in the late 1970s to ensure interoperability among diverse systems and
architectures.
• Key characteristic: It is not a protocol, but a reference model to design flexible, robust, and
interoperable communication systems.
The Seven Layers of OSI
The OSI model has seven layers, categorized into three groups: Network Support Layers, User
Support Layers, and Transport Layer.
1. Physical Layer (Layer 1)
• Purpose: Transmits raw bitstreams over a physical medium.
• Functions:
o Physical characteristics of media (e.g., cables, connectors).
o Bit representation (encoding signals into 0s and 1s).
o Synchronization of sender/receiver clocks.
o Topology (mesh, bus, ring, star).
o Transmission modes: simplex, half-duplex, full-duplex.
2. Data Link Layer (Layer 2)
• Purpose: Ensures reliable data transfer between two directly connected nodes.
• Functions:
o Framing: Converts bitstreams into manageable data units called frames.
o Physical addressing: Adds MAC (Media Access Control) addresses.
o Error control: Detects and corrects damaged frames.
o Flow control: Prevents overwhelming the receiver.
o Access control: Manages channel sharing among devices.
3. Network Layer (Layer 3)
• Purpose: Handles routing and logical addressing for packets between multiple networks.
• Functions:
o Logical addressing: Assigns IP addresses to identify devices.
o Routing: Determines optimal paths for data transmission.
4. Transport Layer (Layer 4)
• Purpose: Provides reliable process-to-process data delivery.
• Functions:
 o Segmentation and reassembly: Splits data into segments and reassembles them at the
destination.
o Service-point addressing: Maps data to specific applications using port numbers.
o Flow and error control: Ensures end-to-end reliability.
o Connection control: Can be connection-oriented (e.g., TCP) or connectionless (e.g.,
UDP).
5. Session Layer (Layer 5)
• Purpose: Manages sessions and controls dialogs between systems.
• Functions:
o Dialog control: Supports half-duplex and full-duplex communication.
o Synchronization: Inserts checkpoints in long data streams.
6. Presentation Layer (Layer 6)
• Purpose: Translates, encrypts, and compresses data for interoperability.
• Functions:
o Translation: Converts data formats (e.g., ASCII to EBCDIC).
o Encryption/Decryption: Secures sensitive information.
o Compression: Reduces the size of multimedia transmissions.
7. Application Layer (Layer 7)
• Purpose: Provides network services directly to the user.
• Functions:
o Enables access to network applications like email (SMTP), file transfer (FTP), and
web browsing (HTTP).
o Interfaces with software and services.
Advantages of the OSI Model
• Standardization: Promotes universal protocols for communication.
• Flexibility: Layers can be updated or replaced independently.
• Interoperability: Allows communication across diverse systems.

2. Explain internet protocol stack

Here’s a breakdown of the Internet Protocol (IP) stack based on the provided document.
The IP stack has five layers, each with distinct responsibilities for transmitting data
efficiently across a network. Let’s explore:

Internet Protocol Stack Layers

1. Application Layer

• Role: Supports network applications and their protocols.

• Protocols:
o HTTP (HyperText Transfer Protocol): Facilitates web browsing by
requesting and transferring web documents.
o SMTP (Simple Mail Transfer Protocol): Handles email transfer.
o FTP (File Transfer Protocol): Transfers files between systems.
o DNS (Domain Name System): Translates human-readable website names
(e.g., www.google.com) into numerical IP addresses.

2. Transport Layer

• Role: Ensures process-to-process data delivery.

• Protocols:
o TCP (Transmission Control Protocol):
▪ Connection-oriented.
▪ Ensures reliable delivery and flow control.
▪ Splits long messages into manageable segments.
▪ Includes congestion control to manage network load.
o UDP (User Datagram Protocol):
▪ Connectionless.
▪ Focuses on speed over reliability (no error control or congestion
management).
• Key Features:
o Addresses application endpoints through port numbers.
o Segments and reassembles data for reliability and proper order.

3. Network Layer

• Role: Handles routing and forwarding of data packets, ensuring end-to-end delivery
across networks.
• Key Components:
o IP (Internet Protocol): Defines how packets (called datagrams) are addressed
and routed.
o Routing Protocols: Determine optimal paths for data delivery.
• Functionality:
o Moves datagrams between the source and destination across multiple
networks.
o Logical addressing ensures devices are identifiable in different networks.

4. Link Layer

• Role: Manages data transfer between adjacent network nodes.

 • Key Features:
o Handles frame transmission, ensuring successful data delivery across a single
link (e.g., Ethernet).
o Protocols in this layer depend on the physical medium being used (e.g., copper
wires, optical fiber).

5. Physical Layer

• Role: Converts data into signals to be transmitted over the hardware medium.
• Functionality:
o Handles the actual transmission of raw binary data (bits) across the network.
o Dependent on the type of medium (e.g., coaxial cables, fiber optics).

Comparison with OSI Model

• The Internet Protocol Stack combines the functionality of the presentation and
session layers (from the OSI model) into the application layer.
• It offers a streamlined and practical approach, unlike the OSI model, which is more
theoretical.

3.Different network devices

1. Repeater
o What it is: A device that operates at the Physical Layer.
o What it does: Regenerates and strengthens weak or corrupted signals to
extend their transmission distance within the same network. It does not
amplify signals but copies them bit by bit.
o Example Use: Extending network coverage in a building.
2. Hub
o What it is: A multiport repeater that also operates at the Physical Layer.
o What it does: Connects multiple devices in a network and broadcasts data to
all connected devices. It does not filter data, so it can lead to inefficiencies due
to data collisions.
o Example Use: Connecting computers in a basic home or small office setup.
3. Bridge
o What it is: A device that operates at the Data Link Layer.
o What it does: Connects two local area networks (LANs) and filters data by
analyzing MAC addresses to forward data only when necessary.
o Example Use: Interconnecting networks with the same protocols while
reducing traffic.
4. Switch
o What it is: A more advanced, multiport version of a bridge, also operating at
the Data Link Layer.
o What it does: Selectively forwards data to the correct port after error
checking. This enhances network performance by reducing unnecessary data
traffic.
o Example Use: Managing data flow in a medium-to-large office network.
5. Router
 o
What it is: A Network Layer device that directs data packets based on IP
addresses.
o What it does: Connects different networks (e.g., LANs to WANs) and decides
the best path for data packets to reach their destination using a dynamically
updating routing table.
o Example Use: Connecting home networks to the internet or linking multiple
corporate networks.
6. Wireless Bridge
o What it is: A Data Link Layer device similar to a regular bridge but operates
wirelessly.
o What it does: Connects two or more LAN segments without physical cables,
using wireless signals instead.
o Example Use: Connecting separate buildings in a corporate campus
wirelessly.

OR

1. Repeater

• Layer: Physical Layer

• Function: Regenerates weak or corrupted signals across the same network to extend
transmission distance.
• Notes:
o Does not amplify signals; instead, it regenerates them.
o Typically has two ports.

2. Hub

• Layer: Physical Layer

• Function: A multiport repeater that connects multiple devices in a star topology.
• Notes:
o Broadcasts data to all connected devices, leading to a shared collision domain.
o Lacks intelligence to filter data or identify the best path for data packets.

3. Bridge

• Layer: Data Link Layer

• Function: Filters data by reading MAC addresses and connects two local area
networks (LANs).
• Notes:
o Acts as a 2-port device.
o Operates on the same protocol for connected LANs.

4. Switch

• Layer: Data Link Layer

• Function: A multiport bridge with a buffer for efficient data transfer between devices.
 • Notes:
o Performs error checking and forwards data selectively to the correct port.
o Reduces traffic and enhances performance compared to a hub.

5. Router

• Layer: Network Layer

• Function: Routes data packets between networks based on IP addresses.
• Notes:
o Connects LANs and WANs.
o Utilizes a dynamically updating routing table to decide optimal paths for data
packets.

6. Wireless Bridge

• Layer: Data Link Layer

• Function: Connects two or more LAN segments wirelessly.
• Notes:
o Operates similarly to a standard bridge but uses wireless signals.

4. Goals of ComputerNetworks:
• Resource Sharing
Many organization has a substantial number of computers in operations,
which are located apart. Ex. A group of office workers can share a common printer, fax, modem,
scanner etc.
• High Reliability
If there are alternate sources of supply, all files could be replicated on two
or, machines. If one of them is not available, due to hardware failure, the other copies could be
used.
• Inter-process Communication
Network users, located geographically apart, may converse in an interactive
session through the network. In order to permit this, the network must provide almost error
free communications.
• Flexible access
Files can be accessed from any computer in the network. The project can be begun on one
computer and finished on another

5. Two types of connections

Point-to-Point Connection:

• A dedicated link between two devices.

• Entire capacity of the link is used for communication between these two devices.
• Commonly uses physical cables, microwaves, or satellite links.
• Example: Connection between a remote control and a television.

Multipoint Connection (also called Multidrop Configuration):

• A single link is shared by two or more devices.

• Capacity of the channel is either shared simultaneously (spatial sharing) or in turns
(temporal sharing)..
• Example: Multiple computers connected to a shared network printer.

6. Explain About Transmission Modes

Transmission modes refer to the ways data is transmitted between devices in a network.
There are three primary transmission modes:

• Simplex Mode:
o Data flows in only one direction, like a one-way street.
o One device transmits, and the other device only receives.
o Example: A keyboard (input device) sends data to a monitor (output device),
but the monitor cannot send data back to the keyboard.
• Half-Duplex Mode:
o Data flows in both directions, but only one direction at a time.
o Devices take turns in sending and receiving data.
o Example: A walkie-talkie, where one user speaks while the other listens, and
then they switch roles.
• Full-Duplex Mode:
o Data flows in both directions simultaneously.
o Both devices can send and receive data at the same time.
o Example: A telephone conversation, where both parties can talk and listen at
the same time.

7. Explain About Types Of Transmission Media

Transmission media refers to the pathways used to transmit data between devices in a
network. It can be categorized into two main types:
1. Guided Media (Wired or Bounded Media):

• Definition: Data signals are transmitted through a physical, guided pathway.

• Key Features:
o High speed and secure.
o Suitable for shorter distances.
• Types:
o Twisted Pair Cable: Consists of pairs of insulated copper wires twisted
together to reduce interference. Commonly used in telephone and Ethernet
networks.
o Coaxial Cable: Has a central conductor surrounded by insulation, a metal
shield, and an outer cover. Used for cable television and broadband internet.
o Optical Fiber Cable: Uses light signals to transmit data with extremely high
speed and low attenuation. Ideal for long-distance and high-bandwidth
communication.

2. Unguided Media (Wireless or Unbounded Media):

• Definition: Data is transmitted through electromagnetic waves without using a

physical medium.
• Key Features:
o Signals are broadcasted through the air.
o Suitable for longer distances but less secure.
• Types:
o Radio Waves: Commonly used for AM/FM radio, television, and mobile
networks.
o Microwaves: Transmitted in a straight line between two antennas. Used for
satellite and long-distance telephone communications.
o Infrared: Uses infrared light for short-range communication (e.g., TV
remotes).

7. Difference between Unicast, Broadcastand Multicast in

ComputerNetwork (different methods of transmitting data

The cast term here signifies some data(stream of packets) is being transmitted to the
recipient(s) from client(s) side over the communication channel that help them to
communicate

• Unicast:
o Involves communication between a single sender and a single receiver.
o It’s a one-to-one transmission.
o Example: Sending an email from one device to another.
• Broadcast:
o Involves communication from one sender to all devices within a network.
o It’s a one-to-all transmission.
o Example: Sending an announcement to all devices in a network using a
broadcast address.
 o Limited broadcast:
▪ Data packets are sent from a sender to all devices within the
same network.
▪ Achieved using the special IP address 255.255.255.255, which
ensures all devices in the local network receive the broadcast.
▪ Example: Sending a network-wide announcement to all
connected devices.
o Direct broadcast:

▪ Data packets are sent from a device in one network to all devices in
another network.
▪ Achieved by setting all bits in the host ID portion of the destination IP
address to 1 (e.g., 192.168.255.255).
▪ Example: Used by TV networks for broadcasting audio and video
streams to multiple receivers.

• Multicast:
o Involves communication from one sender to a specific group of devices.
o It’s a one-to-many transmission, but only for interested recipients.
o Example: Streaming a live video to subscribers of a specific channel.

8. Notes on Different Topologies in Network

In computer networks, topology refers to the arrangement or layout of devices

(nodes) and connections (links) in a network. It determines how devices are
interconnected and how data flows between them.

1. Bus Topology

• Description: All devices are connected to a single central cable (bus).

• Advantages:
o Easy to set up and extend.
o Requires less cable, making it cost-effective.
o Works well for small networks.
• Disadvantages:
o If the central cable fails, the entire network is disrupted.
o Troubleshooting is difficult as identifying problems is complex.
o Performance degrades with more devices due to data collisions.

2. Ring Topology

• Description: Devices are arranged in a circular loop where data flows in one
direction.
• Advantages:
o Efficient data transfer without collisions.
o Simple to manage as data flows in a single direction.
 • Disadvantages:
o A failure in one device or connection can disrupt the entire network.
o Troubleshooting can be challenging.
o Data transmission is slower as packets pass through multiple devices.

3. Star Topology

• Description: All devices are connected to a central hub or switch.

• Advantages:
o Easy to install, manage, and troubleshoot.
o Failure of one device doesn’t affect the rest of the network.
o Enhanced security and better performance with minimal collisions.
• Disadvantages:
o If the central hub or switch fails, the entire network stops working.
o Requires more cable than bus topology, increasing setup cost.

4. Mesh Topology

• Description: Each device is interconnected with every other device.

• Advantages:
o Highly reliable due to multiple redundant paths.
o Ensures continuous communication even if some links fail.
o Supports high data traffic and scalability.
• Disadvantages:
o Expensive due to extensive cabling and hardware requirements.
o Complex setup and maintenance.

5. Tree Topology

• Description: A combination of bus and star topologies forming a hierarchical

structure.
• Advantages:
o Easy to expand by adding branches.
o Offers point-to-point wiring for individual segments.
• Disadvantages:
o Failure in the backbone cable can disrupt the entire network.
o More complex to configure and maintain compared to basic topologies.

6. Hybrid Topology

• Description: A mix of two or more topologies (e.g., star-mesh or star-bus).

• Advantages:
o Flexible and adaptable to different networking needs.
o Can leverage the strengths of multiple topologies.
• Disadvantages:
o High cost and complexity in implementation.
o Maintenance and troubleshooting require expertise.
9. Network Architecture

Network architecture refers to the overall design and structure of a computer network. It
outlines how devices and resources are organized, connected, and interact within a network.
It focuses on the functions, roles, and communication between components like servers,
clients, and network devices. It is also known as a network model or network design.

There are two main types of network architectures:

1. Client-Server Architecture
2. Peer-to-Peer (P2P) Architecture

Comparison: Client/Server vs. Peer-to-Peer (P2P)

Feature Client-Server Architecture Peer-to-Peer (P2P) Architecture

Consists of one or more central servers that All devices (peers) in the network
Structure provide services, while clients request and are equal and can act as both clients
consume those services. and servers.

Centralized control with one powerful server Decentralized control where each
Control
managing resources and access. device manages its own resources.

Can support large and complex networks Suitable for small networks with
Scalability
with many devices. fewer than 10 devices.

Higher cost due to server requirements and Lower cost as no dedicated server is
Cost
increased cabling. required, and less cabling is needed.

Easier to manage and monitor due to the Harder to manage since every peer
Management
centralized system. must be configured individually.

Applications and services must be

Software Applications and services are installed on the
installed on each device
Installation server and shared with clients.
individually.

Less reliable; failure of one device

High reliability; server failure may disrupt
Reliability may affect the resources hosted on
service, but backup servers can mitigate this.
it.

Faster and more efficient for large-scale Slower as peers must communicate
Speed
networks. directly without a dedicated server.

Used in home networks, small

Used in enterprise networks, websites, email
Examples office setups, or for file-sharing
systems, and databases.
applications.

10.Different Types of Computer Networks

1. Personal Area Network (PAN)

• Definition: A small network organized around an individual person to connect

personal devices.
• Key Features:
o Covers a range of just a few meters.
o Typically consists of devices like smartphones, laptops, headphones, and
wearables.
o Supports both wired (e.g., USB connections) and wireless (e.g., Bluetooth)
communication.
• Example: Connecting your smartphone to Bluetooth headphones or smartwatches.

2. Local Area Network (LAN)

• Definition: A network that connects devices within a limited geographical area such
as an office, school, or home.
• Key Features:
o Facilitates resource sharing like printers and file storage.
o Supports high-speed communication and uses Ethernet cables or Wi-Fi.
o Generally owned and managed by a single organization or individual.
• Example: A school’s computer lab connected through Ethernet.

3. Campus Area Network (CAN)

• Definition: A network that connects multiple LANs within a campus or large

premises.
• Key Features:
o Larger than a LAN but restricted to the boundaries of a campus (e.g.,
university, corporate office).
o Uses high-speed optical fibers or wireless technologies for connectivity.
• Example: A university connecting its different departments and libraries.

4. Metropolitan Area Network (MAN)

• Definition: A network that connects multiple LANs across a city or metropolitan

area.
• Key Features:
o Typically used for city-wide networks such as public Wi-Fi or cable TV.
o Faster and less costly than WANs but more extensive than LANs.
• Example: A city's public Wi-Fi system providing internet to various buildings.

5. Wide Area Network (WAN)

• Definition: A large network that spans vast geographical distances, connecting

multiple smaller networks like LANs and MANs.
• Key Features:
o Uses leased telecommunication lines, satellites, or radio waves for
connectivity.
o The largest example of WAN is the Internet.
o Supports low-speed to high-speed data transfer over long distances.
 • Example: A multinational company’s offices in different countries interconnected via
a WAN.

11. Explain about different Switching

1. Personal Area Network (PAN)

• Definition: A small network organized around an individual person to connect

personal devices.
• Key Features:
o Covers a range of just a few meters.
o Typically consists of devices like smartphones, laptops, headphones, and
wearables.
o Supports both wired (e.g., USB connections) and wireless (e.g., Bluetooth)
communication.
• Example: Connecting your smartphone to Bluetooth headphones or
smartwatches.

2. Local Area Network (LAN)

• Definition: A network that connects devices within a limited geographical area

such as an office, school, or home.
• Key Features:
o Facilitates resource sharing like printers and file storage.
o Supports high-speed communication and uses Ethernet cables or Wi-Fi.
o Generally owned and managed by a single organization or individual.
• Example: A school’s computer lab connected through Ethernet.

3. Campus Area Network (CAN)

• Definition: A network that connects multiple LANs within a campus or large

premises.
• Key Features:
o Larger than a LAN but restricted to the boundaries of a campus (e.g.,
university, corporate office).
o Uses high-speed optical fibers or wireless technologies for connectivity.
• Example: A university connecting its different departments and libraries.

4. Metropolitan Area Network (MAN)

• Definition: A network that connects multiple LANs across a city or metropolitan

area.
• Key Features:
o Typically used for city-wide networks such as public Wi-Fi or cable TV.
o Faster and less costly than WANs but more extensive than LANs.
• Example: A city's public Wi-Fi system providing internet to various buildings.

5. Wide Area Network (WAN)

 • Definition: A large network that spans vast geographical distances, connecting
multiple smaller networks like LANs and MANs.
• Key Features:
o Uses leased telecommunication lines, satellites, or radio waves for
connectivity.
o The largest example of WAN is the Internet.
o Supports low-speed to high-speed data transfer over long distances.
• Example: A multinational company’s offices in different countries interconnected
via a WAN.

13.What Is Congestion And Congestion Control

Congestion in a network may occur if the load on the network ( the number of packets sent to
the network) is greater than the capacity of the network / the number of packets that can handle.

Congestion control refers to techniques and mechanisms that can either prevent congestion
before it happens or remove congestion after it has occurred.

14. Explain About Quality of Services

Quality of Service (QoS) refers to the ability of a network to provide a guaranteed level of
performance to selected network traffic. It is crucial for ensuring efficient, reliable, and
smooth delivery of data, especially for applications with specific performance requirements
like video streaming, online gaming, or voice-over-IP calls.

Key Flow Characteristics of QoS

1. Reliability:
o Ensures minimal packet loss during data transmission.
o Some applications (like emails and file transfers) are highly sensitive to
reliability, while others (like telephony) can tolerate some losses.
2. Delay:
o Refers to the time taken for a data packet to travel from the source to the
destination.
o Applications like video conferencing or voice calls demand minimal delay,
whereas slight delays in emails or file transfers are acceptable.
3. Jitter:
o Variation in packet delay. For example, packets arriving out of order in a
video stream can cause disruption.
o Applications like audio and video streaming require low jitter for consistent
quality.
4. Bandwidth:
o Refers to the data rate (amount of data transmitted per second) required by an
application.
o For instance, video conferencing demands higher bandwidth compared to
sending emails.

Techniques to Improve QoS

1. Scheduling:
 o Manages data packets fairly and efficiently.
o Techniques include:
▪ FIFO (First-In-First-Out): Processes packets in the order they arrive.
▪ Priority Queuing: Assigns priorities to packets; high-priority packets
are processed first.
▪ Weighted Fair Queuing: Distributes bandwidth based on priority
weights.
2. Traffic Shaping:
o Regulates and smooths out traffic to avoid congestion.
o Techniques include:
▪ Leaky Bucket Algorithm: Maintains a steady flow of data.
▪ Token Bucket Algorithm: Allows bursts of traffic while maintaining
an average rate.
3. Resource Reservation:
o Allocates specific resources (like bandwidth) for critical applications.
o Protocols like RSVP (Resource Reservation Protocol) help reserve resources.
4. Admission Control:
o Determines whether a new data flow can be admitted based on the available
resources.