Refer to the exhibit. Users on the Internal LAN are unable to connect to the www server. The network administrator pings the server and verifies that NAT is functioning correctly. Which OSI layer should the administrator begin to troubleshoot next?

The administrator has verified that NAT is working and that basic IP connectivity functions (ping works). This means Layer 3 (network layer) is operational, as is Layer 1 and 2. Since users cannot reach the web server using HTTP but IP-level connectivity is confirmed, the problem is at Layer 7 (application layer). Possible issues include: firewall rules blocking HTTP traffic, the web server service not running, or application-level filtering. The next troubleshooting step should focus on application layer issues.