OPEN SYSTEMS INTERCONNECT MODEL

The OSI model consists of seven functional layers which provide the basis for communication among computers over networks.The seven layers of the osi model from the highest to the loest are application,presentation,session,transport,network,datalink and physical.

The Application Layer
The application layer is the interfae to the user.It has several protocols which include the file transfer protocol which enables the transfer of files between two computers and access to directories.A domain name service which is a distributed database system that matches host names to IP addresses.A simple mail transfer protocol which supports sending and receiving emails.A secure file transfer protocol which includes strong encryption and authentication thereby providing security.A simple network management protocol which supports the exchange of management information among network devices.It is a tool used by network administrators to manage the network.A remote login(Rlogin) which is a command in UNIX that begins a session between a user and a remote host on the network.The user can perform all functions as if he were actually at the remote host.

The Presentation Layer
The presentation layer presents information to the application layer.It performs encryption,decryption and compression functions.We have the following standards associated with the presentation layer viz Jpeg and Http.

The Session Layer
The session layer synchronizes the communications between the transmitting and receiving data and also formats the message data.The session layer comprises of various protocols like structured query language,Appletalk session protocol,Remote procedure call and network file system.

The Transport Layer
Tis layer manages the networking of messages and maintains the control of a communications session.It consists of the following protocols which includes transmission control protocol,user datagram protocol and sequencial packet exchange.

The Network Layer
Tis layer sets up logical paths for transmitting data packets from a source network to a destination network.Some of the functions it performs are switching,routing,addressing and error detection.it consists of the following protocols which includes internet protocol,address resolution protocol and reverse address resolution protocol.

The data Link Layer
This layer encodes the data packets to be sent into bits for transmission by the physical layer.The data link protocols include serial line internet protocol and point to point protocol.

The Physical Layer
This layer transmits data bits through the network in the form of signals or radio waves.It includes the necessary software and hardware to perform the task including cabling,cable connectors and cable length,


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