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Network Interface Layer
The Link Layer, also called the Network Interface Layer, is in charge of sending data physically across a network. It has the tools needed for data link tasks, like network adapters, switches, and Ethernet protocols. This layer makes sure data is ready to go over the physical medium and fixes any errors that pop up.
- Physical Layer: Defines the hardware components and how data is physically transmitted over the network.
- Data Link Layer: Manages the framing, addressing, and error detection/correction in the data transmission process.
Protocols commonly associated with the Network Interface Layer include Ethernet, Wi-Fi (IEEE 802.11), and ARP (Address Resolution Protocol).
Internet Layer
The Internet Layer is responsible for logical addressing, routing, and packet forwarding. This layer ensures that data packets are correctly addressed and routed from the source to the destination across multiple networks.
- IP (Internet Protocol): The core protocol responsible for logical addressing and routing. IPv4 and IPv6 are the two versions of IP currently in use.
- ICMP (Internet Control Message Protocol): Used for diagnostic and error-reporting purposes.
- ARP (Address Resolution Protocol): Resolves IP addresses to MAC (Media Access Control) addresses.
- RARP (Reverse Address Resolution Protocol): Resolves MAC addresses to IP addresses, though it is largely obsolete.
The Internet Layer handles the fragmentation and reassembly of data packets to accommodate networks with different maximum transmission unit (MTU) sizes.
Transport Layer
The Transport Layer is responsible for end-to-end communication and data transfer management between hosts. It ensures that data is delivered reliably and in the correct sequence.
- TCP (Transmission Control Protocol): A connection-oriented protocol that provides reliable, ordered, and error-checked delivery of data. It includes mechanisms for flow control, congestion control, and retransmission of lost packets.
- UDP (User Datagram Protocol): A connectionless protocol that provides a faster, but less reliable, data transfer service. It is used for applications where speed is more critical than reliability, such as video streaming and online gaming.
The Transport Layer also provides port numbers to differentiate multiple communication sessions on the same device.
Application Layer
The Application Layer encompasses the protocols and services that directly interact with the end-users and their applications. This layer supports a wide range of network applications and services.
- HTTP (Hypertext Transfer Protocol): The foundation of data communication on the web, used for transmitting web pages.
- HTTPS (HTTP Secure): An extension of HTTP that includes encryption for secure communication over the internet.
- FTP (File Transfer Protocol): Used for transferring files between computers on a network.
- SMTP (Simple Mail Transfer Protocol): Used for sending and receiving email.
- DNS (Domain Name System): Translates human-readable domain names to IP addresses.
- Telnet: Provides bidirectional interactive text-based communication, though it is largely replaced by SSH (Secure Shell).
The Application Layer protocols enable user applications to interact with the network services seamlessly.
Comparison with the OSI Model
The Open Systems Interconnection (OSI) model serves as an additional foundational structure that helps explain network communication. The OSI model has seven layers, including Physical, Data Link, Network, Transport, Session, Presentation, and Application, compared to the four-layer TCP/IP model.
Although the objectives of both models are similar, the OSI model offers a more detailed method of network communication. Because it reflects the protocols and technologies used on the internet, the TCP/IP model is more widely used and practical.
Key Features of the TCP/IP Model
- Scalability: The TCP/IP model can work with networks of any size, like small LANs or the huge internet.
- Interoperability: The model is made to support all kinds of hardware and software, so it can be used on different systems and devices without any problems.
- Robustness: TCP/IP protocols are made to deal with mistakes and make sure that data gets sent correctly, even if there are problems with the network being too crowded or other things going wrong.
- Flexibility: The model can support various communication services, from simple data transfer to complex multimedia streaming.