In my last year of university (5 years ago) I took a networking seminar. Each student took a look at a different technology to utilize multiple links for internet data transfers.
Initially I was amazed by MPTCP and wondered why it had so little adoption. As I looked into the papers I slowly figured out why. With different links (WLAN, LAN, LTE) their real world characteristics are too different for efficient aggregation. It is the head of line blocking problem times ten.
It might be fine as a back up link, but there are other problems like the limit to TCP and middelboxes dropping unknowns packets.
The challenges outnumber the benefits for consumers and in data centers there are other technologies to aggregate links that operate on a level below TCP.
People underestimate how often MPTCP is actually used. Siri has been using it for ages and has since expanded their MPTCP usage to many other built in apps. At some point MPTCP became available to all apps on iOS. Any network with an iPhone connected to it is using MPTCP, whether you know it or not.
When you're using TCP, you can enable MPTCP for free and make your connections faster and more stable. If you're not using TCP, there are alternatives, but then MPTCP is completely irrelevant anyway. You can use QUIC if you want to bypass shitty middleboxes, for instance, as that has similar features but smuggles itself past shitty middleboxes by being marked as UDP (which also makes it more likely to get dropped when the network is congested, unfortunately).
Can an app use MPTCP if they don't have a MPTCP-aware server component? Or is Apple proxying (or via VPN) the MPTCP connection as part of their services?
It needs server side support, but the OS just supports it out of the box. On linux enabling multi path is I believe just a configuration flag and then it just works.
I imagine re-ordering is a big problem. The only application I can think of that would require a single flow is media streaming, but you only need ~4Mbs for a decent quality stream anyway. Other applications like file transfer can be split into multiple concurrent flow, at which point you might as well just let the local router nat each flow to each internet connection in turn.
I hope QUIC with its many advanced features gets better adoption to provide many of the benefits so we can just stop messing with TCP for it's completely screwed up by middleboxes.
I used OpenMPTCPRouter to aggregate 3 LTE connections (via routers connected to directional antenna, with SIM cards from different operators) when I was living in a house in the woods before the war has started I had to leave Russia.
Worked like a charm, giving me up to 180 Mbps or so. May not be that good for aggregating different types of links together, but for using multiple cellular connections it's nearly a perfect solution.
BTW 5G 3GPP specs include MPTCP support, IIRC for aggregating connections going via different gNodeBs (base stations)
I used this product when I lived in a building where I could get a 500mb and a 100mbit connection but not a gigabit connection. I had the server side setup on digital ocean and it "worked" in so far as I could pull 600mbit/s but was impractical since 1) I would get the latency of the worse (and in my case more variable) connection and 2) since it was essentially a VPN to a cloud provider many sites blocked me as a suspected bot.
Love it, but aggregating different connections (latency, LTE vs Adsl, fiber) is hard. Tried different algos, but always had network hogs or even higher ping that slowest connection.
What made it work best (and rock stable) was using LTE only, or ADSL only connections having same ping to aggregator (VPS) and have the VPS as near as possible. (latency wise)
I did not had the time to set up multiple redundant aggregators, so my SPOF was the VPS some times. Maybe there is a solution out there.
So far my experience a year ago. Our provider then offered a way cheaper managed solution, thats why we stopped using it.
Cool, but needs a VPS. A simpler approach is to load balance/ fail over individual TCP/UDP flows, eg using mwan3
I'm hoping that with QUIC, there will be a way to use it's migration feature to load balance more accurately (no need to wait for new flows to start). But, right now there is no way for a middlebox to tell if the server end of an individual flow supports migration, as this is only visible to the client.
I used this when I was in Tallinn. Place I was in didnt have gigabit fiber (probably the only place on the whole street). It worked well for me.
I was using copper internet from local ISP paired with cellular and starlink. Starlink went out for 30 seconds every few minutes but when it worked, it was the fastest of the bunch.
I rented a cheap VPS in the city to use as the other end of this router. The setup worked well overall, I was getting work done along with downloading games with sizes above 100G without worrying too much
In my last year of university (5 years ago) I took a networking seminar. Each student took a look at a different technology to utilize multiple links for internet data transfers.
Initially I was amazed by MPTCP and wondered why it had so little adoption. As I looked into the papers I slowly figured out why. With different links (WLAN, LAN, LTE) their real world characteristics are too different for efficient aggregation. It is the head of line blocking problem times ten.
It might be fine as a back up link, but there are other problems like the limit to TCP and middelboxes dropping unknowns packets. The challenges outnumber the benefits for consumers and in data centers there are other technologies to aggregate links that operate on a level below TCP.
Instead of trying to aggregate by packet, wouldn't it be more effective by managing sessions?
Once a session establishes a route, maintain it. Add logic to prioritize routes by session importance.
That is done with multiwan in opnsense or mwan3 in openwrt.
People underestimate how often MPTCP is actually used. Siri has been using it for ages and has since expanded their MPTCP usage to many other built in apps. At some point MPTCP became available to all apps on iOS. Any network with an iPhone connected to it is using MPTCP, whether you know it or not.
When you're using TCP, you can enable MPTCP for free and make your connections faster and more stable. If you're not using TCP, there are alternatives, but then MPTCP is completely irrelevant anyway. You can use QUIC if you want to bypass shitty middleboxes, for instance, as that has similar features but smuggles itself past shitty middleboxes by being marked as UDP (which also makes it more likely to get dropped when the network is congested, unfortunately).
Can an app use MPTCP if they don't have a MPTCP-aware server component? Or is Apple proxying (or via VPN) the MPTCP connection as part of their services?
It needs server side support, but the OS just supports it out of the box. On linux enabling multi path is I believe just a configuration flag and then it just works.
I imagine re-ordering is a big problem. The only application I can think of that would require a single flow is media streaming, but you only need ~4Mbs for a decent quality stream anyway. Other applications like file transfer can be split into multiple concurrent flow, at which point you might as well just let the local router nat each flow to each internet connection in turn.
I routinely ship 50mbit media streams over the internet, and sometimes streams up in the 200mbit range. In campus streams are up in the 10gbit range.
Over bonded networks bitrate are typically under 40mbit, and usually under 20
Of course none of this uses tcp.
I hope QUIC with its many advanced features gets better adoption to provide many of the benefits so we can just stop messing with TCP for it's completely screwed up by middleboxes.
Middle boxes simply block QUIC so that won’t help
I used OpenMPTCPRouter to aggregate 3 LTE connections (via routers connected to directional antenna, with SIM cards from different operators) when I was living in a house in the woods before the war has started I had to leave Russia. Worked like a charm, giving me up to 180 Mbps or so. May not be that good for aggregating different types of links together, but for using multiple cellular connections it's nearly a perfect solution. BTW 5G 3GPP specs include MPTCP support, IIRC for aggregating connections going via different gNodeBs (base stations)
I used this product when I lived in a building where I could get a 500mb and a 100mbit connection but not a gigabit connection. I had the server side setup on digital ocean and it "worked" in so far as I could pull 600mbit/s but was impractical since 1) I would get the latency of the worse (and in my case more variable) connection and 2) since it was essentially a VPN to a cloud provider many sites blocked me as a suspected bot.
Love it, but aggregating different connections (latency, LTE vs Adsl, fiber) is hard. Tried different algos, but always had network hogs or even higher ping that slowest connection.
What made it work best (and rock stable) was using LTE only, or ADSL only connections having same ping to aggregator (VPS) and have the VPS as near as possible. (latency wise)
I did not had the time to set up multiple redundant aggregators, so my SPOF was the VPS some times. Maybe there is a solution out there.
So far my experience a year ago. Our provider then offered a way cheaper managed solution, thats why we stopped using it.
Cool, but needs a VPS. A simpler approach is to load balance/ fail over individual TCP/UDP flows, eg using mwan3
I'm hoping that with QUIC, there will be a way to use it's migration feature to load balance more accurately (no need to wait for new flows to start). But, right now there is no way for a middlebox to tell if the server end of an individual flow supports migration, as this is only visible to the client.
I used this when I was in Tallinn. Place I was in didnt have gigabit fiber (probably the only place on the whole street). It worked well for me.
I was using copper internet from local ISP paired with cellular and starlink. Starlink went out for 30 seconds every few minutes but when it worked, it was the fastest of the bunch.
I rented a cheap VPS in the city to use as the other end of this router. The setup worked well overall, I was getting work done along with downloading games with sizes above 100G without worrying too much
TCP Over TCP Is A Bad Idea https://web.archive.org/web/20230228035749/http://sites.inka...
MPTCP isn't TCP over TCP.
It’s odd
> If MPTCP is not supported, OpenMPTCProuter can also use Multi-link VPN (MLVPN) or Glorytun UDP with multipath support.
It’s unclear to me from a brief look why they use mptcp as a backend for bonding
What's a Prouter?
It's Open-MPTCP-router.
Rasprouter the bruter! I musta got lost