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
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