Ntc 360 – Network & Telecommunications Concepts – the Osi Model
Essay title: Ntc 360 – Network & Telecommunications Concepts – the Osi Model
The OSI Model
NTC/360 Network & Telecommunications Concepts
The OSI Model
The Open Systems Interconnection Reference Model (OSI) is the accepted model that describes the how the communications for a computer network should be designed. OSI was developed as part of the Open Systems Interconnect Initiative.
Basically, OSI divides the functions of a protocol in to seven layers. This makes the reasoning easy to follow and the system much more reliable. The implementation of several OSI layers is often referred to as a Stack or a TCP/IP Stack.
The layers are often referenced in descending order because layer 7 is the first layer that an end user sees. A detail of each layer in descending order follows:
Layer Seven of the OSI Model – The Application Layer of the OSI model is responsible for providing end-user services, such as file transfers, electronic messaging, e-mail, virtual terminal access, and network management. This is the layer with which the user interacts.
Layer Six of the OSI Model – The Presentation Layer of the OSI model is responsible for defining the language that enables two network hosts to communicate. Encryption and compression should be Presentation Layer functions.
Layer Five of the OSI Model – The Session Layer of the OSI model is responsible for establishing process-to-process communications between networked hosts.
Layer Four of the OSI Model – The Transport Layer of the OSI model is responsible for delivering messages between networked hosts. The Transport Layer should be responsible for fragmentation and reassembly.
Layer Three of the OSI Model – The Network Layer of the OSI model is responsible for establishing paths for data transfer through the network. Routers operate at the Network Layer.
Layer Two of the OSI Model – The Data Link Layer of the OSI model is responsible for communications between adjacent network nodes. Hubs and switches operate at the Data Link Layer.
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