Communitating with XBee module

Hello,

I am new with Arduino and XBee and I am trying to develop 6lowpan and the ipv6 stack for Arduino, using XBee for the 802.15.4 layer.

The problem I found is that the Arduino library for XBee (http://code.google.com/p/xbee-arduino/) uses its own protocol to send and receive data, which adds a START BYTE, the LENGTH, etc. as an extra header, which is not compatible for communicating with a device that implements 802.15.4, 6LoWPAN, ipv6, etc. but does not use an XBee module (a TMote Sky with Contiki, for example).

I saw the code and I can avoid sending that extra header but the problem will be when reading a message, as the XBee will be receiving something but it does not know its length. The question is: - Can I get the size of the 802.15.4 received frame in some way? (in the case that I do not receive the extra header added by the Arduino-XBee library) - If not, do you think that it is possible to read the data (byte by byte) directly from the serial port until it is empty? The problem I see would be to receive two messages faster than the time it takes to read the complete serial buffer.. do you think that this is feasible?

Thank you very much.

Regards,

Alejandro