Router connection speed v ethernet download speed

[boschguy]

Hi everyone, so a very noob question and asking as I e googled and can't find an answer!

I have fttc with a smart hub 2 router. Router stats show I connect at 55mb download 10mb upstream.

Interestingly doing a speed test connected by ethernet to the Lan port I can get 48.6mb. WiFi on 5ghz is around the same at 48mb. 

So my question is, what happens to the missing 6-7mb? 

Now, when testing I've done it late at night and so there will be devices (around 18) connected to the router but not used such as smart lights, tablets, phones. 

My best guess is they use some of the bandwidth regardless, and perhaps so does the BTwifi hotspot that is switched on (no one connected to it). 

Just really interested to know from the resident techies. Thanks!

[licquorice · Accepted solution]

Protocol overheads.

The hub is measuring the physical layer DSL speed. You are measuring at the IP layer. In between you also have the PPP layer and Ethernet layer, all of which have overhead bytes.

Google OSI 7 layer model for explanation of the layers.

[boschguy]

Thanks so much, keen to learn and this was very helpful.