[pptp-server] pptpd 0.9.16 / Win98 performance problem

[Chris Hyde]

Hi there,

Has anything been resolved with the pptpd / Windows 98 performance
issue? I've just read through the archives and there seems to be 
no answer.

My problem:

RedHat 6.0 2.2.10 kernel pptpd 0.9.16 Server on a 3Mb/s fibre
Win98 client on a cable modem connection.

Usual ping is ~25ms.

Connect via VPN and start a ping on the server back to my client:

PING x.x.x.x (x.x.x.x): 56 data bytes
64 bytes from x.x.x.x: icmp_seq=0 ttl=128 time=33.3 ms
64 bytes from x.x.x.x: icmp_seq=2 ttl=128 time=32.5 ms
64 bytes from x.x.x.x: icmp_seq=3 ttl=128 time=32.9 ms
64 bytes from x.x.x.x: icmp_seq=4 ttl=128 time=31.7 ms
64 bytes from x.x.x.x: icmp_seq=5 ttl=128 time=35.8 ms
64 bytes from x.x.x.x: icmp_seq=6 ttl=128 time=35.6 ms

All great so far, then I actually use the connection from the client
side (hit an internal website). Before the website is loaded I see:

64 bytes from x.x.x.x: icmp_seq=10 ttl=128 time=42.2 ms
64 bytes from x.x.x.x: icmp_seq=11 ttl=128 time=60.6 ms
64 bytes from x.x.x.x: icmp_seq=13 ttl=128 time=2690.4 ms
64 bytes from x.x.x.x: icmp_seq=14 ttl=128 time=4331.3 ms
64 bytes from x.x.x.x: icmp_seq=18 ttl=128 time=495.5 ms
64 bytes from x.x.x.x: icmp_seq=19 ttl=128 time=6763.5 ms
64 bytes from x.x.x.x: icmp_seq=20 ttl=128 time=6072.7 ms
64 bytes from x.x.x.x: icmp_seq=21 ttl=128 time=7075.6 ms
64 bytes from x.x.x.x: icmp_seq=22 ttl=128 time=6081.9 ms
64 bytes from x.x.x.x: icmp_seq=23 ttl=128 time=6036.2 ms
64 bytes from x.x.x.x: icmp_seq=24 ttl=128 time=5977.3 ms
64 bytes from x.x.x.x: icmp_seq=25 ttl=128 time=10531.3 ms

... and then the connection will finally break down entirely and no
data will be transferred. There is not a connection problem between me
and the server at all. At the time of testing I was getting <20ms and
no packet loss.

I tried tweaking the PCKT_RECV_WINDOW_SIZE and this improved performance
but I would eventually get the same out-of-sync like behaviour where
the pings would go through the roof and stay there. 

Higher WINDOW_SIZE's would just put this off for a few more pages ...

Anyone have any answers for this one?


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Chris Hyde
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