Which layer establishes the connection between a client and server and maintains it during use of the website?

• A. Layer 4 Transport
• B. Layer 5 Session
• C. Layer 6 Presentation
• D. Layer 7 Application

Answer: (A)

The Transport layer is responsible for creating a reliable end-to-end channel between the client and server and keeping it alive for the duration of the web activity. When your browser loads a page, it typically opens a TCP connection to the server. The transport layer performs the handshake to establish this connection, then manages the data flow with segmentation, sequencing, error detection and recovery, and flow control. This keeps HTTP data moving smoothly and reliably across the network, and the connection can be kept open for multiple requests (or reused) to reduce overhead. If the session is secured, the TLS handshake occurs within this same channel, over the established connection.

While the Session, Presentation, and Application layers have roles related to dialog management, data formatting, and the web protocol itself, the actual establishment and maintenance of the network connection for the duration of website use are handled by the Transport layer.