Why does my internet speed keep dropping?

[Annoyingcloth675]

okay so I'm on Virgin Media and I'm meant to be getting 30Mbps download speed but lately my internet has been dropping very low, sometimes down to 10Mbps
http://s7.postimg.org/wnsi5azjf/lollo.png
I understand that 20Mbps is still very good, but in the small green graph at the bottom it's dropping, instead of a smooth, flat speed at 30. I can't even play a full game on Xbox live, and its very laggy in the party chat. even going onto a webpage takes a way lot longer to load up on all devices. I have tried to restart my Super Hub a million times now but still nothing as changed, it still drops every few seconds.

Any feedback appreciated

[Sporadic]

Virgin can cap speeds, especially at peak times (evenings, usually). I know Sunday night can be a pain for me.

Also if you use too much bandwidth in a one hit (sorry, can't remember how much), you can get sin binned for a few hours, where they drop the speed for your connection to, I think, 1/3 of it's regular speed.

The green bar at the bottom shouldn't really have any peaks and troughs like yours. Personally, I'd run the test at regular intervals over the weekend, and armed with the results, get in touch with Virgin.