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OpenVPN Server Speed Tweaks

I’ve been running my own VPN so I can access my home-based servers from anywhere with an internet connection (not to mention, in this day & age of Government snooping – personal privacy & increased security).

I’m on a pretty quick connection from Virgin Media here in the UK, currently the fastest they offer:

Virgin Media
Virgin Media

To do these tests, I used the closest test server to my VPN host machine, in this case Paris. This keeps the variables to a minimum. Testing without the VPN connection gave me this:

Paris Server Speed
Paris Server Speed

I did expect a lower general speed to a server further away, this will have much to do with my ISP’s traffic management, network congestion, etc. So I now have a baseline to test my VPN throughput against.
The problem I’ve noticed with OpenVPN stock configs are that the connections are painfully slow – running over UDP on the usual port of 1194 the throughput was pretty pathetic:

Stock Config Speed
Stock Config Speed

I did some reading on the subject, the first possible solution being to change the send/receive buffers so they’re set to a specific value, rather than letting the system handle them. I also added options to get the server to push these values to the clients, this saving me the trouble of having to reissue all the client configurations.

Unfortunately just this option didn’t work as well as I’d like, downstream speeds jumped to 25Mb/s. In the stock config, the tunnel MTU & MSSFIX settings aren’t bothered with, some adjustment to set the tunnel MTU to lower than the host link MTU (in my case the standard 1500) prevents packet fragmentation, MSSFIX let’s the client TCP sessions know to limit the packet sizes it sends so that after OpenVPN has done the encryption & encapsulation, the packets do not exceed the set size. This also helps prevent packet fragmentation.

VPN Tweaked
VPN Tweaked

After adjusting these settings, the download throughput over the VPN link has shot up to 136Mb/s. Upload throughput hasn’t changed as this is limited by my connection to Virgin Media. Some more tweaking is no doubt possible to increase speeds even further, but this is fine for me at the moment.

 

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uRadMonitor Network

I’ve joined the uRadMonitor network! I’m told my unit is on the way & it should be going live here in Manchester, UK within about 10 days.

uRadMonitor Unit
uRadMonitor Unit

This is a crowd project to monitor background radiation levels all over the world, so far there’s a lot of units already online.

More to come once my unit arrives!

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Potentially Lethal Clone Apple Charger

Charger
Charger

I received this USB supply with a laser module from China that I purchased on eBay. I have heard of these nasty copies of Apple chargers going around, but I’d never received one this bad with a piece of Chinese electronics.

Label
Label

Model No. A1265, so definitely an Apple clone. Apparently capable of +5v DC 1A output. Notice the American NEMA pins. This wouldn’t have been any use to me in the first instance since I am resident in the UK & our mains plugs are significantly different, not to mention significantly safer.

Manufacturer is marked as Flextronics.

Top Of Boards
Top Of Boards

Here is the charger disassembled. Inside the case these two boards are folded together, creating an alarmingly small isolation gap between the mains side of the supply & the 5v output. Both the low voltage output & the feedback loop for the supply runs over the 4-core ribbon cable.
The mains wiring from the board is as thin as hair, insulation included, so there is a big possibility of shorts all over the place from this part of the circuit alone.

Bottom Of Boards
Bottom Of Boards

Bottom of the PCB assemblies. Good luck finding any creepage distance here. There simply isn’t any at all. traces on the +350v DC rail on the mains side of the transformer are no more than 1mm away from the supposedly isolated low voltage side.

Plugging one of these devices into anything is just asking for electrocution.