OSI MODEL

1.researced and developed by the ISO- (INTER ORANIZITION FOR STANDARDIZATIONS)
2.1977 establish a subcommit to develope a communition  architecture
3.1984 publish iso 7498 the open system interconnection osi reference model

THE OSI MODEL A FRAME WORK WITHIN WHICH NETWORKING STANDARDS CAN BE DEVELOPED IT PROVIDED VENDORS WITH A SET A STANDARDS THAT ENSURED GREATER COMPABILTIY
AND BETWEEN THE VARIOUS TYPES OF NETWORK TECHNOLOGIES THAT WERE PRODECER BY THE MANY COMPANIES AROUND THE WORLD  
    
Q-WHY A LAYERED MODEL ?
+reduce complexity
+ standardizes interfaces
+ facilitates modular engineering
+ensure interoperable technology 
+ accelerates evolation
+simplifies teachning and learning