--On 20 January 2004 21:40 -0500 Robert Watson <[EMAIL PROTECTED]> wrote:

On Tue, 20 Jan 2004, Karl Pielorz wrote:

I've just setup a FreeBSD tunnel (we've tried both gif and tun [via
nos-tun]) now between two fairly large networks of machines...

What version of FreeBSD are you using? If using FreeBSD 5.x, you may well want to switch to 4.x for at least one more minor version, as interrupt latency hasn't been optimized in 5.x yet since the move to interrupt threads, and the network stack also runs with Giant in 5.2 out of the box. I wouldn't think this would hurt you as much as seen below, but it's worth keeping in mind.

Also, I would generally expect gif, gre, et al, to be faster than
tun-based tunneling, as they avoid the trip through userspace, which
involves a number of packet copies.

We're already using 4.9. I also take your point about gif being quicker than switching to user space and back (And, in testing - tun was indeed even slower than gif).

In the end we fixed this problem by putting stupidly fast machines at each end (i.e. P4 2.6Ghz) - we also made some tweaks to the tcp sysctls (such as disabling delayed acks, and closing the window size down) - which also seemed to help.

I'm just wondering if it was something 'weird' such as the delay over the tunnel being on average 'just the right delay time' to cause problems that you wouldn't get on a LAN or something? :)



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