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MPTCP for Linux

135 points by SweetSoftPillow

by majke

1 subcomments

Hey! MPTCP again!
Back in Jan I wrote a piece about how to actually use MPTCP
https://blog.cloudflare.com/multi-path-tcp-revolutionizing-c...
But plenty has changed since then. It seems all my complains about the API are now addressed. Maybe it's a good time to actually run with MPTCP again :)
In my private affairs, I realised I need MPTCP less, since I started using tailscale. My SSH sessions tend to last longer when going over it.

by floam

1 subcomments

If anyone is unaware:
MPTCP being enabled on a server is what makes clients running on Apple devices magically not time out when you walk out of Wi-Fi range or switch to LTE (and is behind the “Wi-Fi Assist” setting/feature). iOS and macOS have had it quietly on by default for years: at first just iCloud etc. used it under the hood but for instance WeChat started enabling it like a decade ago for the improved performance.
With MPTCP, the same TCP session hops networks mid-flight. Without it, these seamless handoffs are at best fast reconnects. It’s one of those Apple things that “just works”; on your Linux server you need to flip it on in `socket()` or look into `mptcpize` last I checked but it’s no big deal. I dont think it’s well supported as a client yet and who knows if Android will ever.
(the “Wi-Fi Assist” toggle in Settings doesn’t enable/disable MPTCP, it is on regardless, but it decides if iOS will spin up a cellular subflow when Wi-Fi starts flaking out. It will use some metered data, hence the user-facing toggle.)

by imglorp

3 subcomments

Sort of related, I'm curious why SCTP did not take off more in this space? It might have had more telecom origins maybe but seemed to fill some of the same needs back in the day.
https://docs.kernel.org/networking/sctp.html
PS the kernel work goes back to 2003!

by muhammadn

1 subcomments

I've tried to get MPTCP support in Chrome (default OFF, with a knob to turn on in GUI) but the reason most often people gave was that there is how to handle support.
Heck. I even tried to add it into git because i was having issues with reliable connectivity with WiFi and 5G (i was in a hotel at that time) while working on a project.
So unless, if there is some reason why people kept giving reasons of not include it. I just do not have a reason to add support for $(name your favorite software)
https://chromium-review.googlesource.com/c/chromium/src/+/63...

by floam

1 subcomments

by sherinjosephroy

0 subcomment

Great to see the continued work on MPTCP integration for Linux. Having this as a mature, native option for better session resilience and bandwidth aggregation is a huge win for network performance.

by xmichael909

0 subcomment

by senshan

1 subcomments

Seems like a fool's errand. The cited RFC8684 starts from the wrong premise:
> TCP/IP communication is currently restricted to a single path per connection, yet multiple paths often exist between peers.
In reality, IP modules of all the hosts and routers can load-balance over a set of all available interfaces, as long as global routing information is available.