I’ve been communicating with the nice folks at IANA (Internet Assigned Numbers Authority) to try to get official recognition for an ED25519 authentication method in IAX2. My submission is linked here:
It’s not that profound, but if anyone has comments please feel free to share them.
is not IAX2 only being kept around for backwards compatibility with old installations? My understanding is that at the moment it’s mainly used for inter-Asterisk trunking and nothing else. Without new implementations being built that incorporate this extension what is the point of this proposal?
Hi Ted. The Amateur Radio community has a large (>10,000 node) IAX2 network that is used to link radio systems around the world. Most of these nodes run an extended version of Asterisk, but there are a few non-Asterisk implementations of the protocol as well. You can learn more at: https://www.allstarlink.org/
I am working on a new, non-Asterisk implementation of IAX2 which is described here: Ampersand Linking Project | Bruce MacKinnon
My IAX2 implementation incorporates several extensions, so I care about IAX2 and am trying to pass my improvements through the Internet standards process.
For better or worse, IAX2 is very much alive.
One fact that hasn’t changed, is that IAX2 is easier to tunnel through NAT than SIP. It’s just one UDP port. I realize SIP is now long-established as a known quantity, and everybody knows all the procedures for dealing with the headaches. But that doesn’t make them completely go away.
IPv6 makes NAT go away and for any new networking you need to be compatible with it.
I’m not qualified to argue the merits of IAX2 vs. SIP, so don’t interpret my messages as trying to argue the superiority of IAX2. 
One guy’s opinion from watching “average people” (not network/VOIP admins) setup/build various VOIP systems: IAX2 is easier to get up and running than SIP for peer-to-peer networks. It’s not just a NAT issue, there are also firewall issues that have to be considered.
And yes, I agree, IPv6 makes things a bit easier.
There’s also the issue of protocol complexity for constrained devices (i.e. microcontrollers and portable stations).
It’s probably not a coincidence that neither of the largest VOIP linking networks used in the Amateur Radio community (EchoLink and AllStarLink) are SIP-based.
What about encryption?