domingo, 28 de septiembre de 2014

Connectivity device


Connectivity devices are those devices used to make physical network connections. Connectivity devices operate at the physical layer of the Open Systems Interconnection Reference Model (OSI) model. The OSI model describes how computer services and procedures are standardized. This standardization allows computers to share information and enables the interconnection of various networking connectivity devices regardless of vendor. 





The seven layers of the OSI model are:



7————–Application

6————–Presentation

5————–Session

4————–Transport

3————–Network

2————–Data Link

1————–Physical



The functions of the seven layers of the OSI model are:


7-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.


6-The Presentation Layer of the OSI model is responsible for defining the syntax which two network hosts use to communicate. Encryption and compression should be Presentation Layer functions.


5-The Session Layer of the OSI model is responsible for establishing process-to-process commnunications between networked hosts.


4-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.


3-The Network Layer of the OSI model is responsible for establishing paths for data transfer through the network. Routers operate at the Network Layer.


2-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.


1-The Physical Layer of the OSI model is responsible for bit-level transmission between network nodes. The Physical Layer defines items such as: connector types, cable types, voltages, and pin-outs




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