June 18, 2025 2:18 PM, "Mickael Torres" <[email protected]> wrote:
> June 18, 2025 12:27 PM, "Jan Stary" <[email protected]> wrote: > >> On Jun 18 08:58:41, [email protected] wrote: >> >>> I've been seeing the same kind of issue on different hardware (both >>> CPU/GPU/NIC). Inconsistent ping >>> latency and reduced download speed. I don't see it much on my local >>> network, way more towards hosts >>> on the internet. For me the trigger is if there's a vlan interface on the >>> OpenBSD side. >> >> Or any other thing on any of the hops inbetween, >> about which you can't know anything (OS, HW, MTU, bufsizes, ...). >> >> What exactly is the issue? >> >>> Without a vlan interface: >>> 64 bytes from 1.1.1.1: icmp_seq=11 ttl=57 time=3.886 ms >>> 64 bytes from 1.1.1.1: icmp_seq=13 ttl=57 time=7.042 ms >> >> That's almost double. So what? >> >>> With a vlan interface: >>> 64 bytes from 1.1.1.1: icmp_seq=3 ttl=57 time=4.299 ms >>> 64 bytes from 1.1.1.1: icmp_seq=7 ttl=57 time=31.252 ms >> >> That's sevenfold. So what? > > The 'what' is that it is consistent with having or not a vlan interface on > the machine. > Tests are not just a one-off, they were repeated tens of times, and the only > thing that > would make the latency inconsistent or the bandwidth to be down is where is > the vlan > 'terminated'. > If the vlan interface is on the machine, I have inconsistent latency and > severely limited > bandwidth. If the vlan is handled by the switch, no issues at all. > My question is what can I check/try to see why this happens? > > I'm going to try to reproduce locally, but for now I couldn't find a way to > do it. > > Best, > Mickael Hello! I finally found the issue, and why I couldn't reproduce locally. With a vlan interface on the machine, the txprio field was set to '3'. With a vlan on the switch, the txprio field was set to '1'. And it seems that my ISP applies some traffic shaping on packets with a txprio field different than '1'. In case it can help someone, solving this was just then setting 'txprio 1' on the ISP-facing vlan, instead of the default 'txprio packet'. Best, Mickael
