Does ipv6 result in higher latencies? I could see larger addresses increasing latency, but then again I could also see a more efficient protocol resulting in lower net latency. I should probably read a book describing the differences.
Google's IPv6 stats also measure latency compared to IPv4 and in most countries IPv6 has lower latency (e.g. in the US on average you get 10ms lower latency with IPv6). When this chart was new it was mostly the other way around, with early IPv6 implementations being poor https://www.google.com/intl/en/ipv6/statistics.html#tab=per-...
If your v4 goes through NAT and v6 doesn't, that's a big thing.
If you have different peering and transit providers in v4 and v6, that's a big thing.
If overhead from address sizes was really a big deal, we'd see work to push larger MTUs and working MTU discovery, but that kind of stalled a while ago. 1500 works for a lot of people, and many major sites drop effective MTU by 20 or so and that makes more things work, and then it gets swept under the rug. (OTOH, I think Android may have finally gotten MTU probing enabled after many years of shipping it disabled; Apple has had very effective probing, at least on iOS for a long time)
Eg: Sometimes IPv6 is faster due to routing differences.
However, this will depend on each specific game, if they are using all the available space or not. If they're sending 200 byte datagrams, they shouldn't see any difference.
On the flipside, IPv6 has a larger minimum MTU than IPv4, so it could happen that your maximum UDP payload actually goes up when switching to IPv6. So, if the game previously had to send 5 packets to do an update, it might be able to send only 3 when it can rely on IPv6, so maybe latency actually significantly improves.
Not sure if the same goes for game UDP packets, but the optional header stuff in v6 IP packets means more of it goes to the useful parts of the payload and less to "the sum of all protocol bits and flags that is not used by all traffic".
Anecdotally, my ping to HN is consistently 166ms with either protocol. I doubt an extra 20 bytes is going to make any meaningful difference to latency, but I'll leave that for the game devs to find out.
So, we have added 24 bytes to the header because of the address difference, and removed 4 bytes from other places.
Now again, there are many differences between IPv4 and v6 that are much more relevant to latency than this extra header overhead. But it is a real overhead, there is no extra scope for payload. Your observation with ping is just wrong (most likely both versions are just padding the packets up to 64 bytes by default).
https://www.youtube.com/watch?v=An7s25FSK0U
This is an area you want to measure carefully because some of the older reports about IPv6 being slower were artifacts of old hardware limitations or under-optimized software which are no longer relevant.
???
On the internet, most links are faster than 1 Gbps and most paths are shorter than 100 hops, so that's a conservative estimate.
If you're sending lots of 10-byte payloads, then IPv6 requires (40+10)/(20+10)=166% as much network capacity, but are you really filling up an expensive link with VoIP traffic?
In practice IPv6 is newer, which has good and bad sides; IPv6 routing paths are more likely to be using newer (and therefore faster) equipment, but there's also a bigger risk of someone making a mistake that messes up your routing/latency, particularly if your ISP hasn't been doing IPv6 for very long.