CTE 244 Computer Networking: Engr. Usman Ishaq Karofi

CTE 244 Computer Networking
Second Semester 2023-2024 Academic Session
Engr. Usman Ishaq Karofi

B.Sc. Software Engineering (Al-Qalam University
Katsina)
usmanishaqkarofi@gmail.com
Week 3: Network Models (OSI and TCP/IP):
Objectives:
• Understand the OSI and TCP/IP models.

• Learn the functions of each layer in both models.
• Compare the OSI and TCP/IP models.
What is Network Models?
Network models refer to the structured representation of how different devices
and systems communicate and interact with each other within a network.
Common Network Models
• OSI Model (Open Systems Interconnection)
• TCP/IP Model (Transmission Control Protocol/Internet Protocol)
What is OSI Model (Open Systems Interconnection)
The OSI model is a conceptual framework used to understand and implement
network protocols in seven layers. Each layer serves a specific function and
communicates with the layers directly above and below it
Seven Layers of the OSI Model
1. Physical Layer
2. Data Link Layer
3. Network Layer
4. Transport Layer
5. Session Layer
6. Presentation Layer
7. Application Layer
Physical Layer (Layer 1):
• Deals with the physical connection between devices.
• Transmits raw bitstreams over a physical medium.
• Examples: Ethernet cables, fiber optics, hubs.
Data Link Layer (Layer 2):
• Handles error detection and correction from the Physical layer.
• Manages MAC (Media Access Control) addresses.
• Examples: Switches, bridges, Ethernet.
Network Layer (Layer 3):
• Manages logical addressing and routing.
• Determines the best path to move data from source to destination.
• Examples: IP, routers.
Transport Layer (Layer 4):
• Provides end-to-end communication and error recovery.
• Manages flow control and segmentation of data.
• Examples: TCP, UDP.
Session Layer (Layer 5):
• Manages sessions or connections between applications.
• Handles session setup, maintenance, and termination.
• Examples: NetBIOS, RPC.
Presentation Layer (Layer 6):
• Translates data between the application layer and the network.
• Handles data encryption, compression, and translation.
• Examples: SSL/TLS, JPEG, GIF.
Application Layer (Layer 7):
• Provides network services directly to user applications.
• Examples: HTTP, FTP, SMTP, DNS.
What is TCP/IP Model (Transmission Control Protocol/Internet Protocol)
The TCP/IP model is a more practical and simplified model used to understand
and design the architecture of the internet. It has four layers.
Four Layers of the TCP/IP Model
1. Network Interface Layer (Link Layer)

2. Internet Layer
3. Transport Layer
4. Application Layer
Network Interface Layer (Link Layer):
• Corresponds to the Physical and Data Link layers of the OSI model.
• Deals with the physical transmission of data.
• Examples: Ethernet, Wi-Fi.
Internet Layer:
• Corresponds to the Network layer of the OSI model.

• Handles logical addressing and routing of packets.
• Examples: IP, ICMP, ARP.
Transport Layer:
• Corresponds to the Transport layer of the OSI model.

• Provides end-to-end communication services.
• Examples: TCP, UDP.
Application Layer:
• Corresponds to the Session, Presentation, and Application layers of the OSI

model.
• Provides network services to applications.
• Examples: HTTP, FTP, SMTP, DNS.
Comparison of OSI and TCP/IP Models
OSI Model:
• Seven layers.
• Developed by ISO (International Organization for Standardization).
• Theoretical model.
TCP/IP Model:
• Four layers.
• Developed by the Department of Defense (DoD).
• Practical model used for actual network communications.
Key Differences
• The OSI model separates functions into more layers, which can help isolate
issues more effectively.
• The TCP/IP model combines the OSI's top three layers into one (Application
Layer), which simplifies the protocol stack used in the internet.
Advantages and Disadvantages of OSI Model
Advantages:
• Modular Approach: The OSI model is divided into seven distinct layers,
making it easier to troubleshoot and develop new protocols for specific
layers without affecting the entire stack.
• Standardization: Provides a standardized framework for different network
protocols, which aids in the interoperability of various hardware and
software.
• Layer Separation: Each layer has specific functions and services, which
promotes a clear separation of concerns and simplifies the understanding of
networking concepts.
• Flexibility: Allows different types of network hardware and software to
communicate, facilitating the development and implementation of various
network technologies.
Advantages and Disadvantages of OSI Model
Disadvantages:
• Complexity: The model's strict layering and abstract concepts can be
difficult to understand and implement, especially for beginners.
• Overhead: Some layers may introduce unnecessary overhead, making the
model less efficient in certain scenarios.
• Theoretical Model: The OSI model is more of a theoretical framework and is
not widely used in practical network implementations compared to the
TCP/IP model.
Advantages and Disadvantages of TCP/IP Model
Advantages:
• Simplicity: The TCP/IP model has only four layers, which makes it simpler to
understand and implement compared to the OSI model.
• Real-world Application: It is the foundation of the internet and widely used
in practical network implementations.
• Flexibility: Adapts well to various network types and technologies, allowing
seamless communication across diverse systems.
• Robustness: Designed to be robust and scalable, enabling it to handle large
and complex networks like the global internet.
Advantages and Disadvantages of TCP/IP Model
Disadvantages:
• Less Modular: The fewer layers can lead to a less clear separation of
concerns, making it harder to troubleshoot and isolate issues to specific
layers.
• Less Detailed: Provides fewer details and functions at each layer compared
to the OSI model, which can limit understanding of specific networking
tasks.
• Limited to TCP/IP Protocols: Designed specifically for the TCP/IP protocol
suite, which may not be as versatile for non-internet-based networking
solutions.
Summary Table:
Suggested Reading:
• "Computer Networking: A Top-Down Approach" by James F. Kurose and
Keith W. Ross
• "TCP/IP Illustrated, Volume 1: The Protocols" by W. Richard Stevens
Assignment:
• Write a comparison between the OSI and TCP/IP models, highlighting their
advantages and disadvantages.
• Create a diagram that maps the layers of the OSI model to the
corresponding layers in the TCP/IP model.

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CTE 244 Computer Networking

Second Semester 2023-2024 Academic Session

Engr. Usman Ishaq Karofi

• Understand the OSI and TCP/IP models.

1. Network Interface Layer (Link Layer)

• Corresponds to the Network layer of the OSI model.

• Corresponds to the Transport layer of the OSI model.

• Corresponds to the Session, Presentation, and Application layers of the OSI

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