Re: Slow WAN traffic to FreeBSD hosts but not to Linux hosts---how to debug/fix?

From: Paul Mather <>
Date: Tue, 31 Jan 2023 22:03:08 UTC
On Jan 31, 2023, at 10:39 AM, David <> wrote:

> On 1/30/23 16:30, Matt Garber wrote:
>>     > Any help/insight is gratefully appreciated.
>>     >
>>     > Cheers,
>>     >
>>     > Paul.
>>     >
>>    sysctl
>>    I would set "htcp" on the server and home computer to improve
>>    through in
>>    your type of situation.
>> There may be other FreeBSD sysctls that have bad defaults in this scenario and could be better tuned, but I doubt changing the CC algorithm at this point is the problem — at least not so much a problem that’s causing throughput to be reduced so drastically. Happy to be wrong if that does help things quickly and easily, though.
>> (Since OP mentioned that FreeBSD CC was set to CUBIC, that would match what the Linux boxes are using by default, too, unless they’ve been changed to something newer like BBR… so seems like CUBIC *should* be performing fine on this WAN link, and the difference is something else.)
>> —Matt
> I love FreeBSD and very much appreciate the efforts of those people much smarter. But... I don't think the defaults get enough testing in real world conditions.
> I came across Paul's issue several years ago and spent a few a hours testing and found the defaults performed very well on a LAN but could perform terribly on a many hop WAN. HTCP performs marginally worse on a LAN or close WAN connection, but much much better on a many hop WAN connection.

> In my opinion HTCP is a better default for the current state of the internet.

It looks like they already changed the default from NewReno to CUBIC in FreeBSD-CURRENT.

I agree with your observation about the defaults vs. real world conditions.  As you observed, I also get great performance in a high-speed LAN, but not so much in a many-hop WAN to an asymmetric ISP connection.

I actually started down this rabbit hole when I noticed I couldn't manage more than about 3--4 MB in a single stream and thought my ISP was throttling me.  But then I noticed I would actually get fast/maximum speeds, e.g., when doing "brew upgrade -v" and Homebrew would be downloading packages, and so then wondered whether they were throttling non-HTTP traffic.  That led me to discover that even HTTP downloads were slow to the FreeBSD servers I use remotely at $JOB and, furthermore, that all traffic to Linux systems I use at $JOB didn't seem to be throttled or incapable of getting maximum single stream bandwidth matching my ISP's quoted speeds. :-\

I accept that this may just be a peculiarity of my local and remote setup, and so appreciate the help and suggestions people have offered in trying to debug the issue.