OSI Model to Protocols

OSI Model Study Guide

The OSI (Open Systems Interconnection) model is a framework that standardizes the functions of a telecommunication or computing system into seven abstraction layers. Each layer has specific protocols associated with it. Here’s a breakdown of the OSI layers and the protocols commonly associated with each:

1. Application Layer (Layer 7)

• Functions: Interfaces directly with the end-user, providing network services to applications.

• Protocols:

  • HTTP (HyperText Transfer Protocol)

  • FTP (File Transfer Protocol)

  • SMTP (Simple Mail Transfer Protocol)

  • DNS (Domain Name System)

2. Presentation Layer (Layer 6)

• Functions: Translates data format from application to network format; handles encryption and compression.

• Protocols:

  • TLS/SSL (Transport Layer Security/Secure Sockets Layer)

  • JPEG, GIF (Image formats)

  • MIME (Multipurpose Internet Mail Extensions)

3. Session Layer (Layer 5)

• Functions: Manages sessions or connections between applications; establishes, maintains, and terminates communication.

• Protocols:

  • RPC (Remote Procedure Call)

  • NetBIOS

  • PPTP (Point-to-Point Tunneling Protocol)

4. Transport Layer (Layer 4)

• Functions: Provides end-to-end communication, error-checking, and flow control.

• Protocols:

  • TCP (Transmission Control Protocol)

  • UDP (User Datagram Protocol)

5. Network Layer (Layer 3)

• Functions: Determines how data is sent over the network; handles routing and addressing.

• Protocols:

  • IP (Internet Protocol)

  • ICMP (Internet Control Message Protocol)

  • IGMP (Internet Group Management Protocol)

6. Data Link Layer (Layer 2)

• Functions: Provides node-to-node data transfer and handles error detection and correction.

• Protocols:

  • Ethernet

  • PPP (Point-to-Point Protocol)

  • ARP (Address Resolution Protocol)

7. Physical Layer (Layer 1)

• Functions: Deals with the physical connection between devices, including cables, switches, etc.

• Protocols:

  • Ethernet (also relevant here due to physical specifications)

  • USB (Universal Serial Bus)

  • DSL (Digital Subscriber Line)

“““In the OSI model, the following protocols generally correspond to their respective layers:

• Physical Layer:

  Ethernet, various cable standards (like coaxial, twisted pair), wireless standards (like Wi-Fi). 

• Data Link Layer:

  MAC addresses, Spanning Tree Protocol (STP), PPP (Point-to-Point Protocol). 

• Network Layer:

  IP (Internet Protocol), ARP (Address Resolution Protocol), ICMP (Internet Control Message Protocol), RIP (Routing Information Protocol), OSPF (Open Shortest Path First). 

• Transport Layer:

  TCP (Transmission Control Protocol), UDP (User Datagram Protocol). 

• Session Layer:

  NetBIOS, PPTP (Point-to-Point Tunneling Protocol). 

• Presentation Layer:

  JPEG, MPEG, ASCII 

• Application Layer:

  HTTP (Hypertext Transfer Protocol), SMTP (Simple Mail Transfer Protocol), FTP (File Transfer Protocol), DNS (Domain Name System) 

Key points to remember:

• The OSI model is a conceptual framework, and real-world protocols may not always perfectly align with a single layer. 

• Some protocols may span multiple layers, depending on their functionality. 

• The most commonly used protocols in the internet are IP (Network Layer), TCP and UDP (Transport Layer). “““