This is a commercial problem, not a technical one.
Not for miners, but for the Internet Exchanges
Is the expected future Bitcoin business big enough and reliable enough for the Internet exchanges to adopt multicast?
Multicast is not supported over the Internet. Period!
Because it was never needed until now $ wise. It's technically simple. Turn on the switch and router software features which make it happen on intranets everywhere.
Internet exchanges would do it if the business were there, like any business would.
So this is a build it and they will come fallacy. There is no demand. Except for Bitcoin which also has yet to be adopted. So it's a quadratic fallacy.
The challenge is to build a business case big enough and convincing enough for all the Internet exchanges in the world to start supporting it finally, en masse.
It's a commercial problem, not a technical one.
The alternative is to hash together a new host centric protocol that does it all, while scaling bigger than any protocol has before, for huge Bitcoin blocks, to thousands of nodes, unicast. Hardly innovative.
Another option is for a private network built between miners only where the IX limitations are irrelevant. But this will be partitioned from public Internet overlay and specialisation nodes. So performance limiting gateways will be needed for SPV users.
Plain old unicast will work today for smaller large block sizes expected at the inception of Teranode. If successful a break point will be hit where unicast no longer scales.
It is here where the multicast commercial decision will be decided.
Will this expected future Blockchain business be big enough and reliable enough for the Internet exchanges to adopt multicast?
This is not an insignificant question. Because the world has yet to decide if Bitcoin is worth adopting already.
These are questions which are getting little focus and encouragement from thought leadership in the Bitcoin world.
This is a commercial challenge, not a technical one.
The Internet has never turned on Multicast for interdomain traffic, because there was never a viable business case for it. Many times it has been requested over the past 30 years. But the case was never convincing. Until, perhaps, now.
So how will they need convincing this time:
1) is the biz case big enough ?
2) will Bitcoin actually get adopted at scale?
3) a new IETF RFC standard or update looks necessary for multicast protocol adaptations. Who will pay for this?
Perhaps by starting out unicast transit as it is today because the host and network load is still relatively low, and ramping up over time will create the demand to activate the resources needed to do the convincing.
Isn't this leaving things rather up in the air though? And to leave this question virtually unattended while forging ahead with Teranode in a vacuum, risks having to roll back a hell of a lot of costly hard work at a later stage, due to unintended consequences.