How about test the speed with pc connected to the modem directly without the switch, and also from Deco directly? Are you testing on the same computer with the same quality cable? What's the Ethernet link speed on the computer in different situations?

Enson Loo wrote

How about test the speed with pc connected to the modem directly without the switch, and also from Deco directly? Are you testing on the same computer with the same quality cable? What's the Ethernet link speed on the computer in different situations?

Thank you for the suggestion Enso, but i have already excluded other devices. This really clearly is a Deco issue. But I tested it just now again, just to be sure:
- ISP modem --> Deco --> Switch --> Desktop PC, all cabled: 90 mbits (out of 200 from ISP)
- ISP modem --> Deco --> Desktop PC, all cabled: 90 mbits (out of 200 from ISP)
- ISP modem --> Desktop PC, all cabled: 201 mbits (out of 200 from ISP)

All was tested on the same pc, through quality cat6 cabled.
(Before this I have done the same tests with a second desktop pc as well (different cables) with same results)
(Also worth noting: Wifi speeds right next to main deco out-of-the-box where up-to 190 mbit, this is also now reduced to 90)

Could anyone at least tell me how to instaal the newer firmware found here :) Would very much like to test this!
http://nl.tp-link.com/download/Deco-M5.html#Firmware

Not sure if it's related... I'm using Network MM on my iPhone to measure the WIFI speed while walking around the house.
When connected to the DECO I see that I'm connect to where the is changing each time and seems to be related to the DECO you are connected to.

What I notice is that I have a speed of about 260 Mb/s, but then the is suddenly changing and my speed drops to 40 Mb/s,
So it looks like that a device is not always connected such that you get the highest speed.

As far as I know, the deco only has one SSID , is there any other wifi network in your house ?

I do not have any other WIFI network.
On my laptop I see the SSID that I have setup in the DECO, but the Network MM app on the iPhone shows a bit more information...

So if my SSID is "DECO" and I'm connected to "DECO" then the "Network MM" app shows "DECO 7f8" and "DECO 13b3" etc when walking around.

Apoxas wrote

Thank you for the suggestion Enso, but i have already excluded other devices. This really clearly is a Deco issue. But I tested it just now again, just to be sure:
- ISP modem --> Deco --> Switch --> Desktop PC, all cabled: 90 mbits (out of 200 from ISP)
- ISP modem --> Deco --> Desktop PC, all cabled: 90 mbits (out of 200 from ISP)
- ISP modem --> Desktop PC, all cabled: 201 mbits (out of 200 from ISP)

All was tested on the same pc, through quality cat6 cabled.
(Before this I have done the same tests with a second desktop pc as well (different cables) with same results)
(Also worth noting: Wifi speeds right next to main deco out-of-the-box where up-to 190 mbit, this is also now reduced to 90)

Could anyone at least tell me how to instaal the newer firmware found here :) Would very much like to test this!
http://nl.tp-link.com/download/Deco-M5.html#Firmware

I did similar tests and found the same problem. So clearly this is a DECO problem, which is a shame.
I'm willing to downgrade the firmware as well.

sounds weird....Have you check other smart phones, are they all the same?
I think you can power off the deco ,and see whether still able to see "DECO 7f8" and "DECO 13b3"

The (hexadecimal) number I also see with SSID's of other WIFI networks, so it's not specific to the DECO. I will check with the supplier of this "Network Mulitmeter" APP what it means.
But what I do notice is that when the speed is dropping, also that (hexadecimal) number is changing. My working assumption is that this happens when one DECO takes over from another DECO. Or when it switches from 5 GHz to 2.4 GHz.

Ok, found it... I used the Network MM on my iPhone in combination with the Wifi Analyzer on the Android.
The Network MM is showing me the speed while walking around.
The Wifi Analyzer is showing me all the details of the different WIFI network around.

These hexadecimal numbers shown in the Network MM are the last 4 digits of the MAC address of the DECO you are connected to. And every DECO has a different MAC address for 2.4 and 5 GHz.
So when I see my speed suddenly dropping (or increasing) it's because it's switching between the 5 and 2.4 GHz of the same DECO, or because another DECO is taking over.

In the example below my speed was low and I walked to the nearest DECO unit. In the next screenshot I was at 1 meter from that DECO. The last 4 digits of the MAC address are 07D7 and it's the 2.4 GHz one.





And then, without moving one inch, it switched to another MAC address and I got the high speed. The last 4 digits of the MAC address are 07D8 and it's the 5 Ghz one.






So it seems that the algorithm within the DECO that decides which network to use is not always selecting the one with the highest speed. Having said that, the 37 Mb/s "low speed" is most likely enough for most purposes... But as I have fiber, 500 Mb up/down, I also like to see that back a bit when connecting via WIFI... Actually I was expecting a higher "high" speed than the 279 Mb/s as my DECO's are connected via CAT-6 cables. E.g. on my PC I get with a speedtest 500+ Mb/s.

Note: at the time of testing there where some other devices connected but more in standby so these should not have influenced the speed.

I can confirm the exact same issue as above! And the strange thing is, in the beginning everything worked just fine.