It could happen, but it’s not mandatory to happen. That your internet connection will be slow when you try to download or upload files over a Vodafone Fiber connection. It happened with a few customers of the company where I work for. To solve this problem you need to add a Traffic Shaper on your firewall.
To add a traffic shaper to the WAN interface you need to go to Policies > Traffic Shaper
Create a new Shaper
First you have to know what your internet speed is. In this example it’s a 50Mbit/s internet connection up and down. I took 92% of the real connection to max out the download speed. This is 46000 (loss of 4mbit)
Give the Traffic Shaper a logical name when saved go to Traffic Shaping Policies.
Add a new Traffic Shaping Policy, select the source (internal lan’s) and the destination (all) the outgoing interface is the WAN interface. Apply the shaper.
When you have applied thie shaper it works instantly for all the users.
Under Traffic Shapers you see the max Bandwith and the current Bandwith utilization at the moment.