Strange priorities in IP Stack


I have a QNX Target A, running QNX 6, and connected to a PC over LAN.
The data path on target is as,
TCP/IP Stack → IPoETH Driver → ResourceManager ->H/w → Line
The ResourceManager provides the POSIX APIs for IPoETH (IP over Ethernet Driver) to read/write the data to H/w.

Now here is my observation.
When I start PING from Target A to PC, all the modules runs at priority 10, which is the default priority of io-net. So all is ok.

But when I send PING from PC to Target A, the PING reply is sent at priority 20.

Just wondering, that which task boosted the priority from 10 to 20!!

Any idea or any suggestion over this, that why this is happening!!

Thanks in advance,

Most probably because you are looking at the thread that is dealing with the interrupt of the network card. For example if you look at the documentation of it says argument priority is used to set the priority of the driver-event thread which by default is 21.

One addition information,
we are using our driver, IPoETH which has no direct packet interface to NIC. All the packet are routed through Resource Manager, which provides the POSIX interface to driver to send / receive the packet.