Example Flow of the OSI Model: WhatsApp Call
- The sender speaks and the Application Layer, or WhatsApp, collects the data
- The data goes to the Presentation Layer, where it is translated, compressed, and encrypted
- WhatsApp uses end-to-end encryption, which means that only the sender and receiver can understand the message
- The Session Layer manages the dialog between the start and end nodes by establishing, maintaining, synchronizing, and terminating connections, or sessions, mainly with Session Description Protocol, or SDP
- Application data from the Application Layer goes to the Transport Layer
- The Transport Layer breaks large Application Data into smaller Data
- Each Data item has a Transport Layer Header, which is the TCP or UDP Header
Application Data = (Header) Data + (Header) Data + ... + (Header) Data
- Segments go to the Network Layer
- The Network Layer adds the Network Layer Header and forms Packets, or Header plus Data
1 Packet = Network Layer Header + TCP/UDP Header + Data
- The packet goes to the Data Link Layer
- The Data Link Layer adds the Header and Trailer and forms Frames
1 Frame = Data Link Header + Network Layer Header + TCP/UDP Header + Data + Data Link Trailer
- Frames go to the Physical Layer, where the data is treated as 0s and 1s, or Bits
- Bits are converted into signals for transmission over the transmission medium