Networking Models - OSI and TCP/IP

In the OSI networking model, there are 7 layers:

1. Physical
2. Data Link
3. Network
4. Transport
5. Session
6. Presentation
7. Application

In the TCP/IP network model there are just 4 layers: 4. Application 3. Transport 2. Internet

1. Network Access

Some of the protocols used in the application, presentation and session layers (Layers 7,6 and 5) are HTTP, DNS, DHCP and FTP.

Some of the protocols used in the Transport layer (Layer 4) include TCP and UDP

Some of the protocols used in the Network layer (Layer 3) include IP and ICMP.

Some of the protocols used in the Data Link layer (Layer 2) include Ethernet.

Some differences between the 2 models are:

• The minimum header size of the TCP/IP model is 20 bytes, the minimum header size of the OSI model is 5 bytes.
• TCP/IP follows a horizontal approach, OSI model follows a vertical approach