Ports reside at the Transport Layer (Layer 4) of the OSI model.
The Transport Layer is responsible for end-to-end communication between applications. Ports, specifically TCP and UDP ports, are crucial for identifying specific applications or services running on a device. They act as addresses that allow data to be directed to the correct process on a computer or network.
Here's a breakdown:
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OSI Model: The Open Systems Interconnection (OSI) model is a conceptual framework that standardizes the functions of a telecommunication or computing system into seven different layers:
- Physical Layer
- Data Link Layer
- Network Layer
- Transport Layer
- Session Layer
- Presentation Layer
- Application Layer
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Transport Layer (Layer 4): This layer provides reliable and unreliable data delivery between end systems. Protocols like TCP (Transmission Control Protocol) and UDP (User Datagram Protocol) operate at this layer. TCP is connection-oriented and guarantees delivery, while UDP is connectionless and offers faster, but less reliable, transmission.
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Ports: Ports are 16-bit numbers that range from 0 to 65535. They are used to distinguish between different applications or services running on a network device. Some port numbers are well-known and are assigned to common services (e.g., port 80 for HTTP, port 25 for SMTP).
- Well-Known Ports (0-1023): These are reserved for common services and system processes.
- Registered Ports (1024-49151): These can be registered by software vendors for specific applications.
- Dynamic/Private Ports (49152-65535): These are typically used for temporary connections.
In Summary: Ports are essential components of the Transport Layer, enabling applications to communicate effectively over a network. They help to identify and route data to the correct process on a device.
