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5 Layers of the Internet


Computers on the Internet are connected by various networks. The complexity of networking is addressed by dividing the Internet into many layers. The International Organization for Standardization (ISO) developed a 7 layer network model (Application, Presentation, Session, Transport,Network, Data Link and Physical layers) long before the Internet has gained popularity. The 7 layer model has been revised to a 5 layer TCP/IP based Internet Model (Application, Transport, Internet, Network, and Physical layers).

Application Layer Application layer defines generic available network applications or services the Internet can support. See the table below for widely used network applications and the corresponding network protocols.
Application Protocol
Email SMTP
File Transfer FTP

Transmission Control Protocol (TCP) Layer This layer concerns how data can be reliably transferred over the network. UDP (User Datagram Protocol) is used when speed of data transmission is more important than reliability.

Internet Protocol (IP) Layer This layer handles address and routing of the network.

Local Network Access Protocol (NAP) Layer This is the part of your system that is concerned with how you communicate with your local network, whether is Ethernet or token ring.

Physical Layer This is the physical connection whether using a Network Interface Card (NIC) or with a modem to connect to the local network.

Related Topics
Network Management - five major functional areas
Classification of Computer network


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