Re: [Bluez-users] ISSC USB dongle can't ping with size 1000

[Marcel Holtmann <marcel@holtmann.org>]

Hi Al,

>     I have the same problem as below which was posted last month.
> 
> >   I started to play with the ping size. 'ping -s 900' works, 'ping -s 1000'
> > kills the PAN connection. There was hope! Then I played with MTU (on both
> > sides): 'ifconfig bnep0 mtu 1000' solves all my problems (default is
> > 1500)!!! With this setting I've a rock solid 75 kByte/s transfer rate over
> > ftp. A mtu of 1017 still works, 1018 definitely kills the connection. 
> 
>      I wonder if there is other solutions to this problem cause the above solution needs to set MTU to 1000 on both sides. 
> 
>      I try ISSC dongle with IVT software as NAP on Windows XP. Ping with size
> 1500 works fine. It seems ISSC chip has some problems to work with BlueZ, in
> addition to adding HCI_RESET.

I am pretty sure that your chip is at fault here. I have no internals
about your chip, but whatever buffer size you tell us, we will use. And
BlueZ will use it as fast as possible. The latency is very low and the
HCI flow control works fine. So I assume there exists a race condition
in your side of the HCI flow control implementation which triggers a
problem. You can verify with hcidump that we do everything right. The
faulty application is actually not BNEP here. I think you can reproduce
it with any program sending big L2CAP packets. So a test setup with
l2test and different MTU might trigger it more easily.

Regards

Marcel




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