Speedify and multipath

Trying to make my Starlink setup reliable enough to use regularly, I think I hit on a good consumer solution: Speedify. It’s a VPN service whose client on your desktop / laptop computer is smart enough to bond two Internet links. It can use extra links to boost speed or reliabilty or both. It seems to work. I’m using this to paper over Starlink’s unreliability. I imagine it’s particularly useful to bond crappy hotel wifi with a cellular hotspot (assuming you have two wifi adapters.)

Before I go on about Speedify I want to mention Multipath TCP. That’s a general technology for doing something similar. The Linux kernel has support and there’s various implementations but I can’t tell if any of them are really usable; a lot look like research projects. The emphasis on TCP is also a limitation, I’d like a redundancy solution for all IP not just TCP. Kind of a different problem though.

The main thing I know about Speedify is I was watching a Youtube video and had an open ssh session and unplugged my ethernet cable that connects me to Starlink. But the video never stopped and the ssh session stayed alive, presumably using the Wifi backup to my other ISP. That’s neat! Also speed tests show I’m getting the full speed of my Starlink, at least sometimes, so it’s not constrained to the lowest common denominator. So far I’ve lost 0.4% of pings to over most of an hour; that’s better than I see using either ISP alone.

The Windows install experience is a dream. Installs smoothly, autodetects your links, sets it all up and you’re running on Speedify in seconds. There’s a free no-account-required option for initial testing, limited to 2GB. The UI is pretty slick too, with decent monitoring and configurability.

One drawback is that Speedify seems to require different actual network devices to bond. What I’d like to do is use a single ethernet adapter for both my ISPs and have Speedify bond two separate gateways. It doesn’t have the UI to do this. (Maybe there’s a way to set up a virtual ethernet device in Windows? Dunno.) I’m working around this by having plugged in a separate WiFi adapter that’s connected to one ISP, with the ethernet to the other. That works fine actually.

Another drawback is that Speedify is a VPN service terminated in a data center. In my case, Fremont CA. That adds latency. Also a bunch of video services like Netflix and Amazon now refuse to serve video to VPN datacenters because they’re so often used to work around country restrictions, etc. Speedify has a special “turn this off for video” feature, but of course video is exactly when you might most want to have Speedify. Finally some folks complain that Speedify makes their links slower than necessary. Speedify, for their part, says you should expect 200-300Mbps.

A final limitation is that Speedify doesn’t give a lot of control over what it’s doing. The user can choose the bonding mode: speed, streaming, or redundant mode. Speed and redundant seem to be two extremes: either maximize performance (but no redundancy) or maximize reliability. Streaming mode is a “smart” middle ground; it monitors each stream and decides when you need more redundancy. Mostly they’re talking about audio and video streams but the marketing copy mentions gaming, too, so presumably that’s also covered. There’s some more technical details here.

Here’s a couple of DSL reports speed tests. These aren’t the best I’ve seen; I’ve gotten 150/20 through Speedify, which is about the limit of my Starlink throughput. (Although I’d expected 50Mbps on the uplink, needs further testing.) I noticed on the download speed test it was only using the Starlink whereas on upload it saturated both my Starlink and my WISP. I think that makes sense. First, redundancy seems more important on the uplink than the downlink. Second, my upload was really limited during these tests and so the WiFi meaningfully could supplement it.

I wish they had a whole-network product! You can probably hack something up using their Linux support and a clever router, their product page indicates they indicate they’re sort of OK with you doing that but might charge you accordingly. That’s what got me interested more generally in multipath technologies for Linux; it’d be nice to have a router designed to do this. I think the easiest way forward with what Speedify has right now is to set up a Raspberry Pi with three ethernet ports; two for inputs from ISPs, one for output to a regular router. You might be throughput limited by USB speeds (for the extra ethernet ports) or encryption speed, but I’m not sure what the limit would be.

I’m really impressed with Speedify so far. I’ll probably sign up for a plan ($3 to $6 a month) for at least a year, to tide me over with Starlink. Gonna run out my free trial here first though.

Update: after most of a day of using it I bought a year of Speedify. $65 with the coupon DEAL10. It really does work as advertised. None of my sessions dropped; World of Warcraft, persistent TCP sockets, two hour idle ssh sessions all stayed open and working. Really solid.

I’m not positive the performance is great but I may be overanalyzing. I’m in Streaming mode and I should be getting at least my Starlink speed, if not better. In practice the speed tests tell me I get about 100/15. Peak is 190/22. Then again that’s just about the average Starlink performance now, so maybe it’s right. It seems pretty smart about using my slower WISP link a lot less but the backup has been there for me every time I needed it. Latency seems fairly variable too, seeing 20-80ms where I’d expect 20-50ms from Starlink. None of this is bad and compared to an unreliable link, it’s terrific. But it does make me think if Starlink gets to 100% reliability I may stop using Speedify.

Now I want a little 4 ethernet port Linux box to run as a Speedify bonding appliance in front of my router! That, or Speedify built right into a router. That should be doable in theory. For some reason Speedify has positioned itself as not a router; they’re real clear it’s a client product.

Update 2: OpenMPTCrouter looks like a plausible base for a roll-your-own alternative to Speedify.