site_archiver@lists.apple.com Delivered-To: darwin-kernel@lists.apple.com User-agent: Microsoft-Entourage/11.1.0.040913 Hello You're right, i also already setup a ppp tunnel over ssh With something like pppd pty 'ssh -x -t -e none user@server /usr/sbin/pppd passive noauth 9600' noauth 10.0.0.1:10.0.0.2 and get the same poor performance, and bad ping also :/ on 26/10/04 20:55, « Jamie Wood » <eimaj79@hotmail.com> wrote:

I have noticed that the performance of the PPP interface in Mac OS X 10.3.5 is not very good at all. I have written a simple program that brings up a PPP interface, configures it using "ifconfig", and reads incoming packets. If I use another program to repeatedly send UDP packets to my newly-created PPP interface in a tight loop, the sendto() function quickly begins to return a "No buffer space available" error. The program which is reading packets from the PPP interface only reports that about 1% of the packets even get through.

If I run a similar set of tests on Linux, none of the UDP packets are dropped, and sendto returns no errors.

In another test, I tried using iperf to measure the throughput of a ssh-pppd tunnel. The most I can get without compression enabled is 1.2 Mbits/sec over a 10 Mbit link. The same test on Linux results in numbers which are close to link speed (one of our tests resulted in ~28 Mbits/sec).

One interesting thing I and my collegues have observed is that if a Linux box is used for one end of the ssh-pppd tunnel, we get about 7 Mbits/sec download speed (Linux->Mac OS X) but only about 800 Kbits/sec upload speed (Mac OS X->Linux).

All of this seems to indicate that there is some sort of performance problem between the TCP stack and the PPP interface code, which is causing some sort of serious delay when the interface picks up events from the stack.

Any information about this behavior, and suggestions for possible workarounds/fixes would be greatly appreciated.

Thanks, Jamie Wood

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