spikes in graph every hour

Hi

can anyone explain what these spikes are on my router when its not in use (the red was ICMP off as I was testing something) and other bits where downloading and gaming...its the in between bits that I'm concerned about

here's the graph

https://www.thinkbroadband.com/broadband/monitoring/...
[img]https://i.imgur.com/CtJaymY.jpg[/img]

I'm just wondering why its not all green during the night an non use

I am on plusnet with 22ms ping

thanks