A Little-Heralded New iOS 7 Feature: Multipath TCP

Olivier Bonaventure writes "Besides changes in UI, multitasking and other features that the press discusses, iOS7 also includes support for Multipath TCP. Multipath TCP is a major extension to TCP that is able to use different interfaces for the same connection. Until now, Multipath TCP has been mainly used by researchers with a modified Linux kernel. iOS7 changes that, with millions of Multipath-TCP enabled devices that can switch from 3G to WiFi without losing existing TCP connections. This is not yet the case on iOS7, which currently seems to only enable it for SIRI, but other use cases will likely appear in the future."

Re:closed source triumphs again

[slash.jit]

How could Tim Cook forgot to present this feature ?

Re:You're Not Making Sense

[Anonymous Coward]

An interesting feature to push for my employer. Getting our servers to support MPT would mean much of the internet will support it.

No, I don't work for MS. I work for Akamai.

IPv6

[hendrikboom]

Anybody know if IPv6 is any better in this regard?

-- hendrik

Re:You're Not Making Sense

[Anonymous Coward]

(Anonymous to preserve modding)

In most cases the web server would receive two requests from two different IP addresses, one per path, with the same session cookies. Let's say one request for the HTML and one for the CSS. That would be enough to serve the right content without any modification to the code on the web server. But I bet that some webapps will be extremely confused by those two addresses. Time to start designing them without the assumption of one-IP-per-session, even inside the same burst of requests?

The best thing I've heard about the new iPhone

[timeOday]

This seems like a very fundamental improvement to the Internet for handling mobility, and a popular product like the iPhone should really boost adoption. Cellular communication is defined by the ability to pair with the best of several available routers, and switch from one to the other without dropping the connection - this is essentially what makes a cellphone different than a plain old cordless phone. But there has always been this annoying disconnect between the cellular network and the Internet, and this sounds like a big step in that direction. If we want super-mobile devices, like dick-tracy wristwatches, they will only have enough power for short-range communication so they will need super-dense infrastructure of some sort, like dynamically pairing with the nearest available wifi or smartphone - migrating connections to the Nth degree.

Re:Siri: Bad use case?

[Rude Turnip]

One of my everyday rituals is walking out of my office building and across the parking lot. During my walk across the parking lot, I ask Siri to call my wife. At some varying point, the building's Wifi cuts out and 3G kicks in. As soon as I read this headline, I knew exactly how it would apply to my life.

This would also be good for Pandora. My home's Wifi reaches almost to my street corner, so I can be several hundred feet away from my house using Pandora and still on Wifi. When I turn the corner, 3G goes on and Pandora cuts out because it lost Wifi. Again, another very practical use of this technology.

Re:Major extension to TCP?

[shreak]

You're right but consider this scenario. You're at a coffee shop that offers wifi and you also have mobile network. You're streaming something to your phone which naturally prefers the wifi network. You get up and walk away and lose wifi. The TCP connection is lost, even though you have a perfectly good moble network also available. The TCP connection needs to be reestablished.

With multipath TCP in the same scenario your phone would have the option of setting up two TCP connections, one over each network. It would present a single socket to the streaming application (who is none the wiser). The multipath TCP socket sends packets over both networks (using whatever spread it feels appropriate). When you walk out of the coffee shop and lose the wifi the multipath TCP socket would stop using the dead network and only use the good network (mobile in this case). No loss in connection.