Inability to use Quality of Service (Bandwidth Allocation):
Quality of Service is a function within some routers that allows you to allocate bandwidth to specific devices as needed. Since Verizon FiOS requires the use of their routers, you are incapable of implementing a QoS capable router while using Verizon FiOS Internet. If you are using Verizon FiOS Internet, you will be required to monitor the bandwidth being used at the location. If there is too much downloading/uploading on the network it could cause the phone quality to degrade.
Useful Resources:Bandwidth, FiOS, How do I set up a Verizon FiOS, QoS, Router, Router Set-Up, Router Setup, Routers, Set up Verizon FiOS, Setting up a Verizon FiOS, Verizon, Verizon FiOS