OSI Layer is broken down into 7 parts, starting from the bottom up, Physical Layer 1 - This is where hardware like physical switches/routers/etc lie Data Layer 2 - This is where the OS's of the hardware lie like Cisco IOS/Juniper OS (JUNOS), etc that facilitate the processing of traffic such as data frames Network Layer 3 - This is where the type of network traffic is initiated e.g. TCP/IP packet initiation and encapsulation of them with tcp and ip information Transport Layer 4 - This is the actual transport layer using protocols like Quality of Service to ensure most efficient service execution for data transport and data integrity Session Layer 5 - This is where authentication/authorisation between the source and destination points is handled establishing a secure connection for data transport via http/https/etc Presentation Layer 6 - This is the protocol layer where data format information is created or used to decrypt and format the data stream incoming Application layer 7 - This is the application level where data is created from and presented to client