The FRITZ!Box can establish internet connections via a fibre optic, DSL or cable modem, or it can use an existing internet connection in the network. In some cases these operating modes require special protocol stacks and packet encapsulation as well as additional security mechanisms (NAT, PPP, PPPoE, VLAN, 'Stateful Packet Inspection' firewall, port forwarding, traffic shaping, etc.), which reduces the highest possible transmission rate for the 'WAN' port to an expected rate between about 940 Mbit/s and 900 Mbit/s.

Important:The internet access speeds that can actually be achieved depend on all of the components involved in transmitting data. In addition to the FRITZ!Box, these include the network device and its network adapter, the upstream modem or router, the internet connection, the internet service provider, and the remote site in the internet.
There are no standardized methods for measuring, and the results of 'speed tests' vary greatly due to numerous factors influencing the results.