Week 4 IA
NTC 360

OSI Model
OSI model is a way of sub-dividing a communications system into small parts called the seven layers. The definition of the OSI model is Open Systems Interconnection model. The seven layers of the OSI model are divided into the host layer and the media layer. On the following paragraphs I would discuss the objective of establishing the OSI model and which end of the layers is closest to physical hardware and which is closest to applications.

The number one layer of the OSI model is the physical layer. This layer defines the electrical and physical specifications for devices. This includes the layout of cable specifications, repeaters, network adapters, voltages, pins, and more. The major functions of the physical layer are establishment and termination of a connection to a communications medium. The modulation or conversion between the representation of digital data in user equipment and the corresponding signals transmitted over a communications channel.

The second layer of the OSI model consists of the data link layer. The data link layer consists of the WAN protocol architecture and the LAN architecture. Both WAN and LAN services arrange bits, from the physical layer, into logical sequences called frames. Not all physical layer bits necessarily go into frames, as some of these bits are purely intended for physical layer functions.

The Network layer is the third layer of the OSI model and also the layer that conclude the media layers. The network layer performs network routing functions, and may also perform fragmentation and reassembly, and report delivery errors. Routers operate in this layer sending data throughout the extended and making the Internet possible. The network layer connects computers with routers and servers.

Transport layer is number four and lives up to its name. The transport layer is responsible for