Internet Protocol Stack (TCP/IP model)

This is the meat and butter to understanding how the Internet works.

Older Models of TCP/IP Model

Older models often show only four layers, combining the link and physical layers into the network access layer.

Application Layer

The application layer is where network applications and their application-layer protocols reside. The Internet’s application layer includes many protocols:

  • HTTP Protocol (for web)
  • SMTP Protocol (for email)
  • FTP Protocol (for files)

Transport Layer

The Internet’s transport layer transports application-layer messages between application endpoints. In the Internet, there are two transport protocols to choose from:

  1. TCP
  2. UDP

Either of these can transport application-layer messages.

Network Layer

The Internet’s network layer is responsible for moving network-layer packets known as datagrams from one host to another.


Physical Layer

The job of the physical layer is to move the individual bits within the frame from one node to the next