Support
 
Phone Live Chat
 
Support
 
US: +1 888 720 9500
US: +1 800 443 6694
Intl: +1 925 924 9500
Aus: +1 800 631 268
UK: 0800 028 6590
CN: +86 400 660 8680

Direct Inward Dialing: +1 408 916 9393

 
 
 
 
Features
Active Directory Management » Features

OSI model: 7 layers explained

The Open Systems Interconnection (OSI) model is a conceptual framework used to describe how network communication occurs between devices on a network. By understanding the OSI model, you gain a clear picture of how network protocols work. Network protocols are constructed upon these layers, ensuring seamless and efficient transmission of data across networks.

The OSI model

How network protocols work: The OSI model

With a structured arrangement of seven layers, each designed for distinct functions and arranged in a top-down order, the OSI model collaborates to facilitate efficient data transmission.

The seven layers of the OSI model

The OSI model consists of seven layers, arranged from the bottom to the top as follows.

  • 1. Physical layer  
  • 2. Data link layer  
  • 3. Network layer  
  • 4. Transport layer  
  • 5. Session layer  
  • 6. Presentation layer  
  • 7. Application layer  

1. Physical layer

The physical layer establishes the physical connection between network devices using cables and connectors. This layer dictates how raw digital data is converted into electrical signals or optical signals suitable for transmission over the network medium.

Examples: Cables, connectors, USB

2. Data link layer

The data link layer functions as the protocol layer responsible for transferring data between nodes within a network segment, utilizing the physical layer for transmission. To ensure efficient transmission, the data link layer breaks the incoming data stream into smaller, manageable units called frames. Each frame acts like a labeled package, containing the sender's and receiver's MAC addresses to ensure it reaches the right destination.

This layer is commonly divided into two sub layers: the media access control (MAC) layer and the logical link control (LLC) layer. The MAC sub layer regulates access to data and transmission permissions for computers on the network, while the LLC layer governs frame synchronization, flow control, and error checking.

Examples: MAC, hubs, switches

3. Network layer

The network layer is responsible for routing and forwarding data packets between different networks. The network layer divides segments from the transport layer into smaller units known as packets on the sender's device and then reassembles these packets on the receiving device.

This layer is also responsible for determining the optimal physical path for the data to reach its destination. This process is known as routing.

Examples: IP, routers

4. Transport layer

The transport layer facilitates end-to-end communication between two devices. The data transferred in this layer is referred to as segments. The primary objective of this layer is to guarantee the orderly delivery of data packets without losses or errors.

Prominent protocols at this layer are the Transmission Control Protocol (TCP), recognized for its near-lossless, connection-oriented nature, and the User Datagram Protocol (UDP), operating on a connectionless, loss-tolerant basis.

Examples: TCP, UDP

5. Session layer

The session layer oversees the initiation of connections, management of sessions, authentication, and security enforcement. It establishes communication channels, known as sessions, between devices. It is responsible for opening sessions, ensuring they remain open and functional while data is being transferred, and closing them when communication ends.

This layer incorporates checkpoints to monitor data transmission sequences. If errors occur during the transmission, data retransmission initiates from the checkpoint. This process is called synchronization and recovery.

Examples: RTCP, PPTP, RPC

6. Presentation layer

The presentation layer is responsible for ensuring that data exchanged between systems is presented in a format that the application layer can understand. It handles tasks such as data encryption, compression, and formatting, allowing different systems to communicate effectively despite differences in their internal data representations. This layer manages data syntax and semantics, ensuring compatibility between communicating devices.

Examples: AFP, NCP, SSL

7. Application layer

The application layer is responsible for providing network services directly to end users. It enables communication between software applications and the network by offering interfaces and protocols that applications can use to exchange data over the network. Functions performed at the application layer include email, file transfer, web browsing, remote access, and other network-based services that directly interact with users.

Examples: Telnet, DHCP, SMTP, FTP

The TCP/IP model

TCP/IP stands for Transmission Control Protocol/Internet Protocol. It is also referred to as the Internet Protocol Suite. It is a set of communication protocols used for connecting devices on the internet. It is responsible for establishing and maintaining connections between devices as well as routing data packets between them.

The model operates on a four-layered architecture, with each layer employing the necessary network protocols to process the data for transmission, thereby optimizing its structure for efficient delivery across the network.

OSI model TCP/IP model

The OSI model has 7 layers.

The TCP/IP model has 4 layers.

This model was developed by the International Standard Organization (ISO).

This model was developed by the Advanced Research Project Agency Network (ARPANET).

Despite its comprehensive structure, the OSI model is not as widely implemented in practice and serves more as a theoretical model.

This model is widely adopted as the de facto standard for Internet communication and is used in the actual implementation of network protocols.

Each layer has specific functions and serves as a modular unit, with clear boundaries between layers.

While the TCP/IP model also defines layers, the boundaries between layers are less rigid, and some functions may overlap.

The OSI model follows a vertical approach.

The TCP/IP model follows a horizontal approach.
The TCP/IP model

Types of network protocol

There are three major categories of network protocols.

Network communication protocols

Network communication protocols establish the rules and formats for data transmission, encompassing syntax, semantics, error detection, synchronization, and authentication. These protocols are essential for ensuring seamless communication and data exchange across networks.

Protocols: HTTP, TCP, UDP, BGP, ARP, IP, DHCP

Network management protocols

Network management protocols define the guidelines and procedures for monitoring, maintaining, and managing computer networks. These protocols communicate these requirements across the network. They also help in quick troubleshooting between host and client devices.

Protocols: ICMP, SNMP, Gopher, FTP, POP3, Telnet

Network security protocols

Network security protocols guarantee secure data transmission across network connections. These protocols outline procedures to protect data from unauthorized access. These protocols use encryption and cryptography to keep data safe.

Protocols: SSL, HTTPS, TLS

ADManager Plus Trusted By

The one-stop solution to Active Directory Management and Reporting
Highlights AD Management Active Directory Reports Exchange Management Popular products

The one-stop solution to Active Directory Management and Reporting

Free Trial Get Quote
Email Download Link
Back to Top