In this post I will talk about the 5 different layers used in the TCP/IP network model. The TCP/IP is a set of protocols that are used for communication between several computers. It consists of five major layers, in each layer the data is isolated in such a way that the only relevant information is used. The layers are as follows:

Layer 5: Application Layer

All users are able to associate with the application layer. It is user friendly and consists of the message. An example of an address at its application layer is any URL for a given website. For example http://www.bentley.edu . Also the port number can be specified at the end of the application layer, although is more thought to be implemented at the beginning of the transport layer. With HTTP (hyper text transfer protocol) the standard port number is 80; however some websites use 8080 in order to secure some data, or make it unavailable for all users. There is more than one way to specify a port number. The easy way when using http is by adding a colon followed by the port number at the end of the URL. For example http://www.domainName.com:8080/

Layer 4: Transport Layer

This layer is responsible for the packetization of messages. Where the message is broken up into packets and put into “envelops” stamping it with address of the final destination.  This layer also is responsible for all end-to-end communication whether the message is sent using TCP, UDP, or SCTP protocols. I will elaborate more on the previous protocols in a later post.

Layer 3: Network Layer

In simple terms this layer is responsible for sending the message to the next address. Sometimes it is also referred to the IP layer. The protocol used here uses an unreliable best effort delivery service. In other words deliver is not guaranteed. One of the reasons it uses this services is because the error correction is found in the Transport Layer, and error checking at this state would “waste” time.

Layer 2: Data Link Layer

The data link layer is considered to be a physical layer. This layer is responsible for the reliable transmission of the message to the next node. It converts IP addresses to MAC addresses (medium access control). Every device has its own MAC address; as a matter of fact a personal computer has at least three MAC addresses, one for Ethernet, one for wifi and one for Bluetooth. This layer makes it possible to transmit data from one node to another. The packets at this layer are called frames.

Layer 1:  Physical Layer

This is where the transmission of the message actually takes place. This layer is implemented via hardware. Depending on the type of device connected to the network different methods are used. This is primarily why both the physical and data link layers are not defined by the TCP/IP and is depended on the underlying network.