1. Network interface (Communication channel) layer
2. Network layer
3. Transport level
4. Applied level
Layer of the network interface
The lowest layer of the TCP/IP model. Its task consists in providing access to transfer the physical environment, and it differs according to environment introduction.
The network layer provides network addressing, the direction and datagram transfer. Used protocols which will be of interest further concerning DHCP, are IP and ARP.
It is the main protocol of a network layer and in general the Internet as a whole. It sends datagrams which are independent units which contain information on mission, a source and serial number of the datagram. Serial number is used for message reconstruction as the order for delivery of datagrams couldn't coincide with their order in the message, and reliability of delivery isn't guaranteed in general.
IP of the version of the protocol:
"IP v4 - 32-bit addresses. Provides about 4 billion unique addresses which aren't sufficient now times.
"IP v6 - 128-bit addresses. Transition to v6 will bring (brings), higher safety, QoS, segmentation of a package and still is a lot of IP addresses. (transition from IP v4 to IP v6 should be supported by the system supplier),
Reduction of ARP designates the Protocol of the Resolution of the Address. This protocol is used to find the physical address (MAC) based on the known IP address. In need of ARP sends information of rather demanded appeal to all stations to networks - the Broadcast. Stations therefore answer with the message containing them by MAC. If demanded the device/station is out of knot/segment, the corresponding router will answer instead of it.
Transport level is carried out only in limiting devices, and it regulates behavior of a network according to device/application requirements.
Applied level is made of programs which use pure services to execute needs of users. Examples of certain protocols - for example, FTP, DNS and DHCP.
Applied protocols use TCP, UDP or both services at the same time. So-called ports are used to be differentiated between applied protocols, they represent type of a label of application. It is possible to change ports in service settings, but each service has a port by default which isn't changed for the majority of services and is used as an unwritten standard.
"FTP = 21
"DNS = 53
"DHCP = 67 + 68