Slow Internet speed when HomePlug combined with router

I'm using HomePlug AV2 600 devices to connect upstairs with downstairs (router is downstairs). A check with `iperf` shows bandwidth of ~100Mbps, and data transferred on the local network from downstairs to upstairs is transferred at about that speed. Good times.

But when I try to access the Internet from upstairs, maximum throughput is only 40Mbps. Bad times.

If I try from downstairs, I get the full 80Mbps that my Internet connection allows. This is really puzzling, as I know the HomePlugs are working faster than that for local data.

The router is connecting to a fibre modem using PPPoE, everything has gigabit ports, and all testing was using wired connections.

If I connect to the router downstairs (wired), then it works great.

If I wire the downstairs HomePlug straight to the modem, and setup a PPPoE connection from the Windows 7 machine upstairs, it also works as expected.

So the issue is only there when connecting to the Internet through both HomePlugs and the router. I've tried replacing the router with a newer model, but get the same result.

I'm at a loss, so any help would be much appreciated!

Well, I still haven't fixed it, but after flashing my router with DD-WRT firmware (TP-LINK Archer C7) I've got 2 reasonable workarounds.

1. Connect using wireless, just for Internet access, and use the wired connection for the LAN. Using wireless 'n' I can get speeds up to 60Mbps. I've got an 'ac' router and adapter, but for some reason I can only get 30Mbps with that - I guess it's an issue with DD-WRT ('ac' support for my router seems to be new to DD-WRT)

2. Enable a PPPoE server on the router, and have the upstairs machines connect to that, using their wired connection (i.e. over the HomePlugs). For some inexplicable reason, I get the full 80Mbps download speed doing this

I'd still love to know why on earth option 2 works, when the 'normal', non-PPPoE encapsulated WAN traffic is half the speed?!

I have a very similar issue, which oddly only affects my Nexus 5 Android phone. It is connected to a Unifi wifi access point and then to the router via some Devolo 200mbs adapters.

Via the adapters it tops out at 3mbs when streaming from the Internet on a 25mbs FTTC line, from the local LAN over the same adapters it can saturate the network happily. Take the power line adapters out of the equation and it all works fine.

I found that it only affected certain pairs of the adapter (I have half a dozen around the house), so I swapped them around until I was using a pair that worked best.

MTU, perhaps?

or maybe Jumbo frames?

In reply to a post by BatBoy:

MTU, perhaps?

or maybe Jumbo frames?

I tried playing around with the MTU, but it didn't seem to have any impact.

What about jumbo frames? Is that something that can be enabled/disabled or configured on the router or the clients?

In reply to a post by andynormancx:

I have a very similar issue, which oddly only affects my Nexus 5 Android phone. It is connected to a Unifi wifi access point and then to the router via some Devolo 200mbs adapters.

Via the adapters it tops out at 3mbs when streaming from the Internet on a 25mbs FTTC line, from the local LAN over the same adapters it can saturate the network happily. Take the power line adapters out of the equation and it all works fine.

I found that it only affected certain pairs of the adapter (I have half a dozen around the house), so I swapped them around until I was using a pair that worked best.

Hmm, does sound like a similar issue.

I've tried 2 different routers (both TP-LINKs tho) and 2 different brands of homeplug (Solwise AV2 600's and Devlo DLAN 650+'s), but got the same result with both.

Colin, I'm seeing very similar problems as you.

I've got some Solwise 500AV homeplugs.

I get a nice 100Mbit/s+ transfer rate between downstairs and upstairs.

I get 74Mbit/s+ on the Internet downstairs.

But upstairs, I'm limited to around 40Mbit/s on the Internet.

Except that in one case, running 15 ssl connections concurrently, I can get the full 74Mbit/s.

I'm wondering if the homeplugs have speed issues with IP fragmentation, because if I lower my router's MTU to 1430 from 1492, I get odd speedtest results, some up to 60-ish Mbit/sec.

Additionally, I'm wondering if not using 1500 byte frames are affecting the homeplugs speed-wise.

-- gyre --

Edited by gyre (Thu 07-Aug-14 13:18:49)

I tried an experiment last night. I put a small http proxy (polipo) on the PC downstairs. I then set that as the proxy for firefox running on the PC upstairs.

I got nearly 70Mbit/s via the proxy on a few speedtests.

I'm just wondering if putting another small computer running a bridge between the router and the downstairs homeplug would solve the speed issue...

Puzzled

-- gyre --