Open system interconnection model...
In this article we try to find the open system interconnection model(OSI) ..
OSI model defined as how the data is transferred from one computer to other computer ..in most basic form of transferring data using wire which is connected to the both the computer's ..but if one computer run's with windows OS other computer with Mac OS then how computers are trying to communicate eachother..??
In order to accomplish the communication between computer's or networks, different architecture ..we use 7 layer OSI model..and it is introduced by the international organisation for standardisation in 1984.... contains 7 layers ...
1.Application layer .
2.Presentation layer
3.Session layer.
4.Transport layer.
5.Network layer.
6.Datalink layer .
7.Physical layer ...each layer is package of protocols....
Application layer
It is used for network applications that means computer applications that use internet like google Chrome, Firefox,outlook, Skype ..etc web browser is network application that running in your pc but it does mean that web browser is reside in application layer .but it's use application protocols like http , HTTPS , HTTPS , FTP, NFS,FMTP,HCP,SNMP,TELNET,IRC...there are lot of application layer protocols are used to function service's like file transfer using FTP, web surfing using HTTP/S,emails for SMTP, virtual terminal for TELNET..ETC...
So application layer provides survices for network applications with the help of network protocols to perform user activities ...
Presentation layer
This presentation layer receive the data from the application layer and this received Data is in the form of characters and numbers. presentation layer converts this characters and numbers into Machine understandable language (binary language)...
Eg ; ASCII , EBCDIC...
this function of presentation layer is called translation....after completing the translation we have to reduce the data before the data is transmitted ..by using this process we can reduce the no.of bits that are used to represent the original data...this method is called data compression ...
Example; using data compression method we can reduce 5mb file into 2mb file without eliminating actual data . reducing data we have advantages like speed, accuracy,data receive the destination in less time. it is very useful for real time video and audio.. streaming .....to maintain intergrity data we have to be encrypted before transmission ..to receive data we have to decrypt it using SSL( secure socket layer ) this used for encrypt/decrypt ....
There are three basic functions TRANSMISSION
DATA COMPRESSION
ENCRYPTION/DECRYPTION...
SESSION LAYER
It help setting up and managing connections enabling sending and receiving the data ... following termination of connections and sessions ...using application interface provide programing (ADIS) ...if a session need to work then a connection is established with the server perform a function called Authentication
Authentication
This is a process of knowing "who are you" a server uses a user name and posword if you want to connect the session or connection then you have to match user name and posword in server .....then a connection established between server and your computer...after Authentication the authorisation checked
AUTHORIZATION...
The authorisation is a process used by servers to determine or checked permission for accessing the file ....if you have permission then you will download easily. if not the page shows" you are not authorised to access this file "...this is managed by the session layer
Example...
If a webpage contain text and images ...this text and images store in separate file in servers .when you request to a web browser it opens a separate session to download these text ,images etc....this images and files received in the form of data packets.. so session layer keep in track of flow of data and received destination this is called session management ...
Finally he session layer helps in ...
A.session management..
B.authorization
C.Authintication...
I will stop here.. thank you for reading this article.. if you are interested then i will write on remaining layers ...
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