TCP/IP, the OSI model, and the IEEE 802.x standards are all important network conceptual models and standards.
The Open Systems Interconnection reference model, or OSI model, is a network model developed in 1983 by the international standards organization. The OSI model is split into 7 layers with each layer being assigned a different aspect of the model to take care of. The following are the 7 layers of the OSI model:
- Physical Layer – This is the physical transmission of data between the two nodes via whatever connection type they might utilize e.g. Ethernet.
- Data Link Layer – This is the data link layer and it takes the raw bits that have been transferred through the physical layer, handling any errors along the way, and converts them into a data frame that can then be used by the next layer (network layer).
- Network Layer – This is the network layer and it controls how a data packet operates when being transmitted. E.G. the route it takes.
- Transport Layer – This is the transport layer and it takes data from the layer above (the session layer) and splits it down into smaller data packets that can be transferred along the network layer. At the other end it also ensures that all those smaller data packets arrived correctly.
- Session Layer – This is the session layer and it handles the communications between the machines, initializing, managing and afterwards terminating any communications or exchanges between the two endpoints.
- Presentation Layer – This is the presentation layer and it takes care of the way everything being transmitted is displayed.
- Application Layer – This is the application layer. It is the highest / top level layer and it contains all the different protocols required by the different application services it provides.
The IEEE, also known as the Institute of Electrical and Electronic Engineers, developed the IEEE 802 standards which deal exclusively with the first two layers of the OSI model. (Physical and data link)
The IEEE 802 standards split the data link layer of the OSI model into two sub-layers. These are the LLC or logical Link Control sublayer and the MAC or Medium Access Control sublayer. The physical layer deals only with the physical network interface controller, each of which have their own unique MAC address.
Originally developed in 1969 by the US Department of Defense, TCP/IP is a set of network protocols that enable data to be transmitted through the internet, allowing end to end communication. TCP/IP has become the standard of the internet and is now the most widely used network protocol.
There are 4 layers in the TCP/IP model and these are:
- Network Interface Layer – Also known as the physical layer, this deals with protocols that operate only on a link.
- Internet Layer – Also referred to as the network layer, this layer deals with the data packets and also connects networks so that the packets can pass across network boundaries.
- Host to Host Layer – Also referred to as the transport layer, this layer maintains the end to end connection.
- Application Layer – This layer deals with the protocols that work directly with the applications.
TCP/IP deals with all 7 layers of the OSI model in just 4 of its own layers. Exactly how the OSI model and TCP/IP compare can be seen below:
Now that you know a bit more about network conceptual models and standards, why not carry out some research into the various standards and conceptual models out there. You’ll find quite a few.