Title: Network Model
Course: Introduction to SSL/PKI > Section: SSL/TLS

Network Model

The network communication model shown is an abstraction of actual network communications. In theory, each layer in the model communicates with itself using the next lower layer.

This type of model is sometimes called a "protocol stack".

Application layer

The application layer is used by programs to communicate over the network. Data is passed to the next lower layer for transmission over the network in an application specific format.

Transport layer

The transport layer connects applications together. It is responsible for making sure the data reach its destination reliably.

The transport layer's responsibilities include:

- end-to-end message transfer
- error control
- fragmentation (packets)
- flow control

Network layer

The Network layer is responsible for getting the data from the source network to the destination network. This usually involves routing the packet across a network of networks (such as the Internet).

Data link layer

The data link layer is responsible for transmitting the data over a physical medium.