Re: [v6ops] Geoff/queue-closed: 56%

[Brian Candler <[e-mail]>]

On 17/04/2024 11:13, Xipengxiao wrote:
> We should document IPv6 packet loss issues, identify causes, and publish
>   drafts to address the issues.  Now that average IPv6 RTT is lower than
> IPv4 RTT (according to APNIC stats), if we can bring IPv6 PLR (packet
> loss rate) comparable to IPv4 PLR, then we can declare IPv6 provides
> better performance than IPv4.

I think first we need to dig into *why* those measurements are seen.

As far as I can tell there is no fundamental reason why IPv6 should be 
any more performant than IPv4 for latency, and I would expect typical 
TCP throughput to be ~1.4% worse on IPv6, due to the larger headers.

Personally, I observe paths taken over the IPv6 Internet often to be 
quite different to those taken for IPv4, and that may indeed mean 
shorter and/or less congested paths for IPv6, but this seems to be down 
to political issues rather than technical ones (e.g. a certain 
well-known tier 2 backbone provider offering free peering on IPv6, to 
pick up more routes in an attempt to persuade tier 1's to peer with them)

I don't think this is sustainable in the long term though.

Furthermore, the fact that IPv6 topology is not the same as IPv4 has its 
own problems. If you can argue in any form that the IPv4 Internet is 
"fully connected", then the IPv6 Internet is not; for example Google 
doesn't announce IPv6 routes to transit providers (or didn't last time 
that I checked), meaning that some people can't reach Google over IPv6 
at all. Most of the time, Happy Eyeballs papers over the cracks - i.e. 
IPv4 connectivity is the only one that matters today.

 > That can become a universal reason to persuade people to migrate to 
IPv6.

I don't believe that it stands up as such.

Also, everyone should be clear that there is currently no such thing as 
"migrate to IPv6". You either add IPv6 to your IPv4 stack, or you stay 
with IPv4. You can't remove the IPv4 part without cutting yourself off 
from most of the Internet.