1. OSI ARCHITECTURE IN OSI, ACTUAL INFORMATION IS OVERHEADED BY PROTOCOL LAYERS IF ALL SEVEN LAYERS ARE OVERHEADED, THEN AS LITTLE AS 15% OF THE TRANSMITTED MESSAGE IS HAVING SOURCE INFORMATION.

2. Session Transport Network Datalink Physical Presentation Application Computer A Session Transport Network Datalink Physical Presentation Application Computer B Virtual Communication

3. PHYSICLA LAYER PROVIDES ELECTRICAL AND MECHANICAL INTERFACES FOR A NETWORK SPECIFIES TYPE OF MEDIA USED TO CONNECT NETWORK DEVICES SPECIFIES HOW SIGNALS ARE TRANSMITTED ON NETWORK

4. DATA LINK LAYER CONTROLS ACCESS TO COMMUNICATION CHANNEL CONTROLS THE FLOW OF DATA ORGANIZES DATA INTO LOGICAL FRAMES IDENTIFIES SPECIFIC COMPUTER ON THE NETWORK DETECTS ERRORS

5. NETWORK LAYER MOVES INFORMATION TO THE CORRECT ADDRESS ASSEMBLES AND DEASSEMBLES PACKETS ADDRESSES AND ROUTES DATA PACKETS DETERMINES BEST PATH FOR MOVING DATA THROUGH THE NETWORK

6. TRANSPORT LAYER TAKES ACTION TO CORRECT FAULTY TRANSMISSION CONTROLS THE FLOW OF DATA ACKNOWLEDGES SUCCESSFUL RECEIPT OF DATA FRAGMENTS AND RE ASSEMBLES DATA

7. SESSION LAYER ESTABLISHES AND MAINTAINS CONNECTION MANAGES UPPER LAYER ERRORS HANDLES REMOTE PROCEDURE CALLS SYSNCHRONIZES COMMUNICATING NODES

8. PRESENTATION LAYER ENCODES AND DECODES DATA DETERMINES THE FORMAT AND STRUCTURE OF DATA COMPRESSES AND DECOMPRESSES DATA ENCRYPTS AND DECRYPTS

9. APPLICATION LAYER PROVIDES THE USER INTERFACE CONNECTS THE USER TO THE NETWORK PROVIDES FILE TRANSER SERVICE,EMAIL SERVICE TERMINAL EMULATION, AND OTHER SERVICES