Full Fibre Upgrade 500-900 No change in download speed

[#1]

Earlier this year I was persuaded to upgrade my fibre contract from 500 to 900 speed, (no brainer, it was actually cheaper!)
I use a Google Mesh system (1st gen Model Gj2CQ) We have three devices in the house but my main desktop PC is wired into the main router by a CAT 5E cable The router connects to the BT ONT by a CAT 6 Cable on the WAN Gigabit port.

All Speeds quoted below are WIRED

Prior to the upgrade, I was getting around 480Mbps Upload and 70Mbps Download, this measured both on my PC with speedtest.net and the Google Home app directly on the router.

Post completion of the upgrade I now usually get a hard 540-560 Mbps upload and 107Mbps Download,  Upload is clearly fine but there seems to be an issue with the download speed not being what it should.

I've been through the Plusnet technical help who checked that the upgrade had 'gone through' and tried all the suggestions (power reset router, ONT, router solo without the mesh setup, through to the total pain of a  complete factory reset of the router and MESH network ..TWICE! )  I've even tried a different router on a short ethernet cable close to the ONT with no change in the speeds.

The Google MESH router does not have a QOS setting available to disable, instead it has a device priority feature which IS disabled.

I am now pretty much convinced that the BT network is holding back the speed.   

[#2]

The security packages / ad-blockers and software on the PC can be the issue.

If you boot the PC into Safe Mode + Networking and re-run the speed test does the download speed improve ?

https://interprefy.speedtestcustom.com/

https://speed.cloudflare.com/

[#3]

Hi Philip

I can completely eliminate there being any problem with the PC by running the router's own speed test from the Google Home App which gives similar results...

Similar results with the BT app too

[#4]

@Vic20 

I am now pretty much convinced that the BT network is holding back the speed.   

Are you sure the GJ2CQ has enough CPU power to drive the WAN at 900Mb ?

Its based on a 4 core Qualcomm Atheros IPQ4019 running at 716mhz. The WAN link is PPPoE and most implementations of this are single threaded so a single 716mhz core MIGHT just not be able to hack it ?

Do you have another router e.g a Plusnet Hub 2 ? just to be able to rule out the router

edit: try googling 'IPQ4019 pppoe nat throughput'

[#5]

Thanks MisterW, makes sense. I consulted Claude...

"

"The Hardware Ceiling

The Google Wifi (GJ2CQ) runs a quad-core ARM processor at 710–716 MHz, with 512 MB of RAM and uses the Qualcomm IPQ4019 chip. Tom's Guide While the chip does include a hardware NAT accelerator, it's still fundamentally a ~717 MHz Cortex-A7 design from around 2016.

The GJ2CQ (model AC-1304) is a Wi-Fi 5 device, and the maximum throughput you can realistically expect from it is around 400–600 Mbps — well short of full gigabit speeds. JustAnswer

---

PPPoE Makes It Worse

PPPoE adds meaningful CPU overhead on top of basic NAT, because each packet needs to be encapsulated/decapsulated. This is a well-known issue with high-speed broadband. As one networking forum noted, doing close to a gigabit per second using PPPoE is genuinely challenging — the overhead was fine in the days when DSL topped out at 1–16 Mbps, but at 900 Mbps it becomes a serious burden. Netgate Forum

So at 900 Mbps PPPoE, your router is dealing with:

• NAT processing at near-gigabit rates
• PPPoE encapsulation/decapsulation overhead on every packet
• Mesh management traffic on top of that"

I don't have a Plusnet Hub 2. But I have ordered a GLi-Net MT2500A Mini VPN security gateway to handle the PPPOE and NAT. It was something I was considering anyway for its VPN features. It is based on OpenWRT which I'm very familiar with. Will report back with results!

 

[#6 · Accepted solution]

@Vic20 

But I have ordered a GLi-Net MT2500A

That should hack it with Hardware Offloading enabled, although that precludes using any QoS.  I run a similar MT7981 based router (Cudy WR3000H) running Openwrt albeit as an AP. One of my colleagues runs one as his primary router on a gigabit fibre connection and its fine.

[#7]

That Fixed it!



Thanks for your help!

[#8]

Good to hear.

That's the problem when moving to >500Mb speeds, equipment can have a big influence on achievable speeds.