Re: [Bluez-users] MTU in l2test

Marcel Holtmann
2005-01-02T14:05:21Z

Hi Manjunath,

> I am varying the mtu and data size variables in the l2test program.
> From the docs, I learnt that maximum L2CAP payload is 65535 bytes. I
> am unable to set the data size above 45000 bytes inspite of setting my
> MTU to 65535 (both on the sender and the receiver).
> I get an error saying "Send failed. Resource temporarily unavailable".
> Hope you can help me with this one.

the MTU is different for incoming and outgoing side. With what kind of
device and what commands lines are you testing these.

> Also, in the l2test, is the data channel connectionless(6 byte L2CAP
> header) or connection oriented(4 byte L2CAP header).I am asking this
> because the code seems to have a 6-byte offset for the header which
> means the data channel might be connectionless but i am also able to
> see the "connection request" and "configuration request" which is a
> feature of connection oriented data channels.

Actually the connectionless L2CAP is not really supported and maybe
somekind of buggy. Feel free to send in any improvements.

> Also, how is that I am able to see the packet size of ACL Data in "HCI
> dump", say a 339 byte packet for DH5 packets. Isn't this supposed to
> happen at the Baseband?

The HCI sends up the ACL data and actually for most chips it is the same
size as on the baseband. As far as I know this is not recommanded, but
it is a good way to not introduce too much overhead for the chip. The
final SAR is done by the L2CAP layer.