# Status of multipath TCP support on FreeBSD 12+



## Veeny (Feb 20, 2021)

Hi guys,

my boss is talking about live video streaming using multi-path backup mode. I've gathered that FreeBSD is multipath TCP capable using an extension, but I'm wondering if that extension has been merged into the kernel or, if not, if it is compatible with the latest kernel versions. Can't seem to find any relevant piece of information about this.

If someone knows, I'd be forever beholden to them. 

Cheers,
Vincent


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## Deleted member 66267 (Feb 21, 2021)

If no one answer you here you could try asking on the mailing lists.


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## Veeny (Feb 21, 2021)

failure said:


> If no one answer you here you could try asking on the mailing lists.


Well, yeah, that particular topic doesn't seem to stir up a lot of turmoil   Thanks for the tip.


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## Mjölnir (Feb 21, 2021)

If you mean automatic failover via CARP? Yes, that's supported for several years now.  It can be combined with LACP, IIRC the latter even has a special mode to support a propriatary mode used by Cisco equipment?  See carp(4) & lagg(4) & consult the Handbook (scroll to the top of this page).


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## SirDice (Feb 21, 2021)

I've tried searching for it but apart from an old experimental patch for HEAD (which was 11.0 at that time) I haven't found anything.






						Multipath TCP for FreeBSD | FreeBSD Foundation
					

TCP Extensions for Multipath Operation with Multiple Addresses (MPTCP) allows a mutli-homed host to utilize multiple network interfaces or paths on a single TCP session. The protocol is currently being standardized by the IETF in RFC 6824. The Foundation is sponsoring a Master's research...




					freebsdfoundation.org
				




Reading the wikipedia article I did notice SCTP is mentioned as an alternative. Now that is supported, sctp(4).



Mjölnir said:


> If you mean automatic failover via CARP?


No, that's something else entirely.


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## Mjölnir (Feb 21, 2021)

See also the respective section in the FreeBSD Status Report for 2020Q4


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## Veeny (Feb 22, 2021)

Ok, thanks to everyone. I shall consider sctp


Mjölnir said:


> If you mean automatic failover via CARP? Yes, that's supported for several years now.  It can be combined with LACP, IIRC the latter even has a special mode to support a propriatary mode used by Cisco equipment?  See carp(4) & lagg(4) & consult the Handbook (scroll to the top of this page).


And no, this is not CARP. We have to live-stream videos from "field" locations, where typically no fibre, and probably no ADSL connection, is available. To try and avoid any loss that may occur if we use a single 4G channel, we would like to stream through a device with 2/3/4 SIMS, each one tied to a different operator. If the stream experiences unbearable jitter or lost packets with the current selected operator, we switch to another operator, etc. But that means the packets can arrive out of order, thereby the need to use MPTCP to reorder them before forwarding them to a streaming platform such as YouTube or Vimeo.

… and Bob's your uncle 

Cheers and thanks for your input!


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