Networking Models

Two networking models describe the communication and transfer of data from one host to another, called ISO/OSI model & TCP/IP model.

OSI vs TCP/IP

OSI Model

• uses seven different layers, which are hierarchically based on each other

• each layer offers services for use to the layer directly above it. To make these services available, the layer uses the services of the layer below it and performs the tasks of its layer

• The layers 2-4 are transport oriented, and the layers 5-7 are application oriented layers

• When an application sends a packet to the other system, the system works the layers from layer 7 down to layer 1, and the receiving system unpacks the received packet from the layer 1 up to layer 7

Layer	Function
7) Application	controls the input and output of data and provides the application functions.
6) Presentation	transfers the system-dependent presentation of data into a form independent of the application.
5) Session	controls the logical connection between two systems and prevents connection breakdowns or other problems.
4) Transport	can detect and avoid congestion situations and segment data streams.
3) Network	Data is transmitted over the entire network from the sender to the receiver.
2) Data Link	enables reliable and error-free transmissions on the respective medium.
1) Physical	the transmission takes place on wired or wireless transmission lines.

TCP/IP Model

• a layered reference modelو often referred to as the Internet Protocol Suite.

• stands for the two protocols Transmission Control Protocol (TCP) and Internet Protocol (IP).

• IP is located within the network layer (Layer 3) and TCP is located within the transport layer (Layer 4) of the OSI layer model.

• IP ensures that the data packet reaches its destination.

• TCP controls the data transfer and ensures the connection between data stream and application.

• every application can transfer and exchange data over any network, and it doesn't matter where the receiver is located.

Layer	Function
4) Application	allows applications to access the other layers' services and defines the protocols applications use to exchange data.
3) Transport	responsible for providing (TCP) session and (UDP) datagram services for the Application Layer.
2) Internet	responsible for host addressing, packaging, and routing functions.
1) Link	responsible for placing the TCP/IP packets on the network medium and receiving corresponding packets from the network medium.