Subject: NetBSD TCP strangeness (was: problems using nbcvs)
To: None <>
From: John Klos <>
List: tech-net
Date: 01/28/2003 17:41:16

> > Allen Briggs tested this, too, and says this:
> > ftp inside the NAT block says 4.5KB/s, outside the NAT 150KB/s.
> > NAT isn't clamping mss or anything.  Trivial configuration.
> I'll update this and say that with NetBSD (Jan 14 current) running
> instead of OS X (inside the NAT here), it's getting ~150KB/s.  I've
> not been paying enough attention to know if that's well-known.

Let me qualify this completely:
I have NetBSD 1.6 running on a colocated server with a fast uplink. It is
running 1.6 release with nothing out of the ordinary, and I'm using Apache

From behind IP NAT using IP Filter (tried NetBSD 1.5.2, 1.5.3, 1.6, 1.6
release from two weeks ago, FreeBSD 4.6.2), all Mac OS X machines get
anywhere from .5 k to 10 k/sec from my server. Note that all of the NATs
tested were not PPPoE or anything that requires a reduced MTU.

From behind all of those NAT, Linux, Windows, Mac OS classic, AmigaDOS,
and NetBSD all get expected speeds:
gaia: {4} ftp -4
100% |*************************************| 4228 KB 273.25 KB/s 00:00 ETA

I don't have any OS X machines that are not behind NAT, but if anyone else
can test this, I'd like to know if the problem is specifically due to IP
Filter's NAT and how it works with OS X. Also, the OS X machines don't
have any problems with most other servers.

I also have slow speeds (10-15k/sec) from, but I really
can't find any large files to test on there. But it also happens with
mail-index - oh, wait - that's the same as www now, isn't it?

[sonja:~] elaine% ftp
100% |*************************************|   198 KB    8.32 KB/s    00:00 ETA

VAX, NetBSD 1.6, same network:
gaia: {6} ftp -4
100% |*************************************|   198 KB  155.77 KB/s    00:00 ETA

I think someone more skilled than me should look into this, because I
haven't a clue, and this seems to be a big problem.

John Klos