Show me literally any data to support your hypothesis. I showed my work, with measurements and analysis. For example, you could use the APNIC Labs data I showed to compare newer and older networks. We might then ask how old those networks are. Then for anyone concerned that IPv6 would be slower on their network, they could compare their network's age. Without that data, and with all of the data I have see, I have to conclude that you are simply wrong about IPv6 being slower. Lee On 12/3/2025 2:20 AM, Vasilenko Eduard wrote:
My hypothesis, supported but unproven My hypothesis, supported but unproven: IPv6 is activated on new networks. New networks have a bigger capacity and better hardware/software. Moreover, new networks have been designed with the bigger previous experience. It is not always the case, but typically, new things are better than the previous generation. Ed/ -----Original Message----- From: Lee Howard via NANOG <nanog@lists.nanog.org> Sent: Tuesday, December 2, 2025 20:28 To: nanog@lists.nanog.org Cc: Lee Howard <lee@asgard.org> Subject: Re: IPv6 Performance (was Re: IPv4 Pricing)
Before you call people silly, you might want to collect some data.
You would think IPv6 headers would add processing time, but that turns out not to be the case. Yes, they may sometimes be routed along different paths, but I have seen IPv6 have fewer hops and lower latency as often as I've seen IPv4 be faster. When I was at a large network, I published these results, measuring from many points in the network to many common destinations, and there was no predictable difference.
This is true for CGN, firewall, load balancer, router, translator, or any other hardware. The *only* exception is some limited release devices that kicked IPv6 forwarding to the software plane; I would argue that that is not IPv6 support. If anyone else has contrary experience or data, please share. To be fair, such devices also do not add measurable latency in performing NAT44.
Many networks have reported that IPv6 has lower latency, in fact.[1] In North America, IPv6 has a 2ms advantage over IPv4.[2]
This is *as measured* not based on theory.
My hypothesis, supported but unproven, is that when a device uses or prefers IPv6 (such as on an IPv6-only network with translation) and tries to reach an IPv4 destination, the device uses software CLAT to convert IPv4 to IPv6 in the device before forwarding. This would be the case, e.g., for an Android device on an IPv6-only network like T-Mobile, maybe Charter. [3] I haven't seen the new Windows CLAT, but it wouldn't be surprising.
It is fair to say that in general or overall, IPv6 has a slight performance advantage over IPv6. That may not hold true for all permutations of endpoints or devices, so your individual experience may vary.
Lee
[1] e.g., https://www.internetsociety.org/blog/2015/04/facebook-news-feeds-load-20- 40-faster-over-ipv6/
[2] https://stats.labs.apnic.net/v6perf/XQ
[3] Measurements and explanation at https://www.arin.net/blog/2019/06/25/why-is-ipv6-faster/
Fundamentally, IPv6 should be slower because of the bigger
On 12/2/2025 2:09 AM, Vasilenko Eduard via NANOG wrote: headers/overhead.
But it could be faster because CG-NAT detour (if CG-NAT is not on the shortest path). IPv4 and IPv6 could both be faster/slower because of non-congruent peering topology. Actually, the claim that IPv6 is faster is pretty silly. Ed/
-----Original Message----- From: Marco Moock via NANOG <nanog@lists.nanog.org> Sent: Tuesday, December 2, 2025 07:42 To: nanog@lists.nanog.org Cc: Marco Moock <mm@dorfdsl.de> Subject: Re: IPv6 Performance (was Re: IPv4 Pricing)
On 01.12.2025 16:44 Bryan Fields via NANOG <nanog@lists.nanog.org> wrote:
At least once or twice a month I'm downloading something and will find the IPv4 to transfer significantly faster. Case in point, I downloaded the proxmox iso yesterday to a colo server with 50g uplinks. It loafed at 2.4 mbytes/s using default wget, which of course preferred ipv6. Adding -4 to wget made that shoot up to 80 mbytes/s. Have you checked packet loss and latency?
Maybe that is caused by different routes due to peering.
-- kind regards Marco
Send spam to abfall1764603853@stinkedores.dorfdsl.de
NANOG mailing list
https://lists.nanog.org/archives/list/nanog@lists.nanog.org/message/EBHOWL WPDOYOV2ATJPYBAA2CLI6SMIEE/ _______________________________________________ NANOG mailing list https://lists.nanog.org/archives/list/nanog@lists.nanog.org/message/IL5AHCA XCZRJACSQMCFETQEY4GDVX57L/