[shivam543]

> And until we can start disabling v4, v6 gives no advantage and only causes significant added complexity.

v6 advantages:

* If you're an ISP, you need more complex hardware for CGNAT-v4 if your traffic is huge. If you do support v6, netflix, youtube and majority of your traffic is already on v6, you can get by without upgrading your CGNAT Infra.

* I suspect v6 should have faster initial connection - time to first byte, because of no NAT. I assume NAT is implied in v4 because if you're an ISP say in India where you have 1.2B mobile devices, you cannot buy 1/4th of all IPv4 addresses.

* Because of more IP addresses you can run VMs with public v6 addresses. It's not common to have ISPs give multiple IPv4 to a single customer, but with v6 that's always the case.

[mort96]

* Until the transition is complete, I and everyone else is gonna have to use an ISP which provides a v4 address, whether they're end users or a server operators. Fair enough though that ISPs may have some incentive to making more people have v4+v6 (not that they seem to have realized...)

* I really don't think NAT could possibly make a noticeable difference in the time to first byte. My guess about what's "barely noticeable" would be a few hundred added milliseconds, my guess at what NAT would add would be a few milliseconds. Happy to be proven wrong though if there are any studies or experiments on the topic.

* I'm not sure what benefits there are to giving your VMs public v6 IPs when you still need to support incoming v4 connections.

[Dagger2]

For whatever reason (it's probably a mix of NAT, the extra routing needed for CGNAT, and other things) there is a measurable difference in time to first byte on v6. Apple measured it as 40%: https://www.zdnet.com/article/apple-tells-app-devs-to-use-ip...

(Also, doing things like loading a webpage requires many round trips, so even a small RTT difference multiplies to a bigger delay for total load time.)

You don't need to remove v4 to get benefits from v6. For example, you can handle inbound v4 on your load balancers to avoid needing to mess around with it on your entire VM fleet.

[shivam543]

s/w stack penalizes IPv4 by 25 ms to 300 ms. This is not a point to say that v4 is bad, but has been made bad artificially: https://ma.ttias.be/apple-favours-ipv6-gives-ipv4-a-25ms-pen...

[shivam543]

I did a small experiment with 2 websites: federalreserve.gov and one of the Google's server located in Delhi. I'm in India in a city around 250 kms from Delhi on ISP: Reliance Jio Fiber. I see around 8ms benefit when using IPv6 for Google, and 20 ms when using federalreserve.gov Hardly noticable