@malreyyashi 

Hey

Just reading what you have stated this appears to be the PLC backhaul restriction.  

The P9s have a PLC backhaul as you describe, and this is rated for 1gbps connection, from experience you will not get anywhere near this in real speeds.   I have an 2000mbps Powerline from TPLink and a 1200 Powerline from Devolo and both get nothing close to what they indicate, usually speeds in real terms are around 120mbps.

Its the same with WiFi, your devices are reading as connected at 800mbps, they will likely offer around 350/400 mbps in real terms with a good signal.  Its just the nature of how Powerlines and WiFi work.

In general, WiFi is faster than PLC, however not as reliable and more susceptible to lag and speed drops.   Good old LAN cable will connect at 1GB and offer you 940mbps always.

If you are iperf testing on the same node (cable to wifi) then I would expect around 400mbps connection, cable to cable 900mbps.  However if you are going node to node via the PLC then it really is a guess, from experience I have always seen this top out around 100mbps.

You would be best testing the iperf on a single node (no backhaul) and see if that comes good, then try the backhaul. 

@Philbert 

Thanks for these valuable information, I'm very appreciated for this.

But my question now is if my ISP offer me a 600 mbps internet speed, am I going to have less than that speed? 

because now I'm confused by what is being advertised by the router and what I will get from real terms.

Thanks for your answer in advanced 

@malreyyashi 

Hey

It sounds like you are going to have the same dilemma that I did.   I upgraded from 80mbps DSL to 1gbps FTTP last year and had the same problem as you, my existing Deco and HomePlugs handled the 80mbps fine for a few years, but couldn't take anything over 120mbps and therefore totally throttled the FTTP connection once it arrived.

In short and being totally honest, there really is only 2 solutions for you

Homeplugs and PLC isn't going to be anywhere near fast enough, these state speeds of 1gbps and more but in reality, you never get anything like that!   The best I have ever seen is ~250/300 and that was from one side of a room to the other, maximum of a 5 meter run.   I have tried Denlovo, Asus, Netgear, TP Link they are all the same sadly.. PLC / Powerlines simply are not fast enough for the WAN speed you are looking to use.

That leaves WiFi and Good old LAN Cables

WiFi  -  The P9s are 802.11AC (also known as WiFi5) grade devices, which means they can offer WiFi speeds of 433mbps per antenna of which there are 2x (total 866mbps).  This is again the 'theoretical maximum' and you won't get that due to interference, refraction, loss etc.  From experience in real-world transfer rates it tops out around 40% or ~180mbps per antenna (total ~360mbps).    The issue I have with the P9s for your setting is they tend to prefer the PLC connection over the the WiFi and this is slower.  Even if they did use the WiFi backhaul its going to take a lot of your bandwidth away from clients (1x of the antenna really) so its going to throttle you.

The 802.11AX range (WiFi 6) of Deco is an option, they offer the newer and faster standard of WiFi and do tend to be faster in general.. but they are expensive and trying to get 600mbps from this is a hard push. They advertise 1200mbps WiFi so I would estimate 450 / 500 in real terms.    You also need WiFi 6 devices to connect to even get that!

Then lastly is LAN Cables.. they do what they say on the tin!   A 1gbps LAN cable will transfer 940mbps all day long and honestly, this is the only way you are going to get the 600 speed for your WAN.     LAN cable the P9 Deco devices together and switch to Access Point mode, this will therefore use the 1gbps LAN connections between them for backhaul and give you the full 2x antenna speed for your devices (~360 / 400mbps, maybe a tad faster).    That is the route I had to go down and 6 months later it turned out the best choice.

Yes you wont get your full 600 on WiFi even with the LAN cable backhaul, however unless you have $$ to burn on a total WiFi6 setup with new wireless cards for the clients then its not going to happen.   If you need the full 600 use a cable, if on WiFi 350/400 should be more than acceptable for most. 

I personally changed the Deco to the TP Link Omada range (business grade) as they are generally faster overall.   Went for a controller, 2x EAP245s and a switch, connected all via Cat6 cables and its been fine so far.    iperf tests on WiFi I'm getting around 450 on a connection that reads 866.

I hope all that helps.. sorry this isnt going to be an easy one for you!   Honestly, with the internet speed you are looking to deliver cabling is your only real option

Hello @Philbert 

This is the depth technical details that I was looking for, I do really appreciate your efforts for explaining that, I'm planing to use Ethernet cable instead of PLC now.

I'm very thankful to you.

@malreyyashi 

If you are going to run cables, which I 100% recommend you do..  consider running Cat6 cables

Cat5E is designed for 1gbps top speed but can do 2.5gbps over short runs

Cat6 is identical to cat5e (1gbps) but can take 10gbps over distances up to 50meters.   Price wise it almost identical to 5e so definitely your best choice as this will future-proof you for 10GB networks in a few years, unless of course you are intending to run over 50 meters distance.

Cat6A is also an option also, its designed for 10GB networks up to 100meters.   However the cable is much thicker and a lot less flexible, also harder to terminate, its a bit of a challenge to work with if honest and is much more expensive.  Likely not needed just yet for most homes.  Cat6 standard should suffice for a good while

Also worth noting if you are buying cable there is two types  labeled CCA and AWG

CCA is Copper Coated Aluminum.. cheaper but not as good

AWG is the standard full copper

Ive used both without issue so its personal choice, I went copper cat 6 myself for home as the difference was so little I though "get the better cable"

If you do have any other queries don't be afraid to ask, more than happy to help!

Thanks @Philbert 

I will take your notes into consideration 

I'm going to test these routers on a 600 Mbps fiber and I will share the results here.

I'm going to test multiple scenarios Like PLC only or Ethernet only.