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FS#4221 - R7800 poor download rate when client connects with 100FD #9202

openwrt-bot opened this issue Jan 9, 2022 · 7 comments

FS#4221 - R7800 poor download rate when client connects with 100FD #9202

openwrt-bot opened this issue Jan 9, 2022 · 7 comments


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@openwrt-bot openwrt-bot commented Jan 9, 2022


Netgear Nighthawk X4S R7800 with OpenWrt 21.02.1 freshly installed

ISP line is 250/25. Wan port is 1G (auto).

Steps to reproduce:
Laptop connected on LAN-side with 1G (auto): Ookla speedtest is 250/25.
Laptop connected on LAN-side with 100FD: Ookla speedtest is only 30/25.

This performance degration only occurs, when the R7800 is routing and natting the traffic.
"Switched only" traffic inside the LAN is not affected.

With stock ROM the download rate is as expected:
Laptop connected on LAN-side with 100FD: Ookla speedtest is 80/25.

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@sppmasterspp sppmasterspp commented Mar 16, 2022

I experience the same low download/upload speeds when there is LAN traffic.
I fully explained the things in several posts here
I have issues with download / upload rates only when there is traffic on the LAN-side like playing a 4K movie from LAN.
If a device is playing a 4K movie over WAN side (like HBOMax) there are no speed drops.

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@sppmasterspp sppmasterspp commented Mar 17, 2022

After lots of tests - here is the problem completely reproducible using iperf3 to create LAN traffic between LAN clients. In my case I run iperf3 (with a predefined throughput of 60Mbps) between a Laptop connected at 100Mbps! (this is the culprit) and PC connected at 1000Mbps. The result - the PC can only download/upload from/to WAN at really low speeds.
If the same test is performed when a Laptop is connected at 1000Mbps then there is no problem for the PC to achieve full speeds.
The slowdown only occurs when a device (Laptop, PC, Smart TV) is connected via cable and the negotiated speed is 100Mbps (I've used a 100Mbps cable). Then the other device even connected at 1000Mbps cannot download/upload to WAN at high speed if there is LAN traffic at the same time.

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@sppmasterspp sppmasterspp commented Mar 18, 2022

I have to add that two compulsory conditions should be met at the same time in order to reproduce the WAN performance drop. A client connected at 100Mbps (let's call it "Problem Client") and a LAN traffic between the "Problem Client" and any other device connected to LAN by cable.

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@Ansuel Ansuel commented Mar 20, 2022

@sppmasterspp what we should really test is if the original firmware also suffer from the same problem. Can you that simple test? It's just to have a direction if internally they fixed the bug and we are just missing the workaround on our code

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@sppmasterspp sppmasterspp commented Mar 20, 2022

@Ansuel What I've been able to test so far is this:
With Voxel firmware based on original Netgear firmware the router can reach maximum download speeds (considering the scenario with LAN traffic and 100Mbps Problem client takes place) even with ping being 50-70 ms. But the WAN upload speed in this case is limited to around 150Mbps.
Will add more test data as soon as I can.

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@sppmasterspp sppmasterspp commented Apr 8, 2022

@Ansuel @quarkysg
I've tested extensively the latest stock Netgear firmware and latest Voxel firmware for R7800.
I've found that both have almost the same issue as OpenWRT.
There are a few differences. The stock firmware is more resilient and when the LAN traffic is present (between PC and 100Mbps client) the full WAN download speed is still achievable even though with higher ping times. But when the WAN speed is at full there are drops in LAN transfer speed.
The upload WAN speed is limited as with OpenWRT firmware.
Original Netgear firmware experiences issues with WAN download speeds too but this happens when there are two different 100Mbps devices connected to the LAN ports and there is a LAN transfer involving one desktop PC (1Gbps) sending files over LAN (or running iperf3 server) to both 100Mbps clients. Using this scenario the R7800 has problems to achieve full WAN down/up speeds.
If the clients are connected at 1Gbps full WAN/LAN speeds at low pings are possible.

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@sppmasterspp sppmasterspp commented Apr 9, 2022

I've posted the exact steps to reproduce/trigger the bug.

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