Re: IPv6 Performance (was Re: IPv4 Pricing)

[Tom Beecher via NANOG <nanog () lists nanog org>]

Also Geoff has measured this :

https://nanog.org/events/nanog-66/content/1078/

https://archive.nanog.org/sites/default/files/Huston_Is_Ipv6.pdf

10 years old now, but his conclusions then were if you could establish a
connection, V4 and V6 latency was basically the same. ( Unless 6 to 4 was
involved. )

On Tue, Dec 2, 2025 at 12:29 PM Lee Howard via NANOG <nanog () lists nanog org>
wrote:

> 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/
>
>
> On 12/2/2025 2:09 AM, Vasilenko Eduard via NANOG wrote:
> > Fundamentally, IPv6 should be slower because of the bigger
> 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
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