Network connections

There is a whole array of devices between you and the target server daemon, so any of those can be slow. Usually it looks like this from your browser to the website:

• Browser
• Network Manager
• Operating System (OS)
• Network Card
• Cable / WiFi (aka WLAN)
• Switch or Access Point
• Router
• Modem
• Wall Plug
• box in basement (either active, like with most DOCSIS installations, or passive with VDSL)
• copper or fibre cable
• box on street containing ISP network devices
• fibre channel to local ISP backbone
• local backbone network devices
• more centralised peering point
• Central Internet Exchange (CIX)
• another CIX
• peering point
• data centre uplink
• data centre core modem
• core router
• core switch
• rack switch
• hypervisor's (HV) network card
• HV OS and virtualisation software (e.g. XCP-ng)
• virtual machine (VM) network interface
• VM OS
• server daemon for reverse proxy on VM (e.g. HAProxy, Envoy)
• VM OS, network interface, HV, rack switch, another HV, another VM's network interface and OS
• web server daemon (e.g. nginx, Apache2)
• backend server daemon (e.g. Apache Tomcat, node.js, PHP FPM, Django, Golang binary)
• the actual application's routing library (e.g. Nio, Gorilla)