I have been onto 2nd level support with a mobile carrier. Always a fun exercise. This time they are calling me since I tried calling them, and I am not an authorised person on my clients phone bill so my client got them to speak to me.

Right now the issue is that a SIM card is playing up in a piece of equipment. Now, this is not all that strange, but the support people are having real issues sorting out the issue. After some questioning from me, they started doing more research and found an error on their system saying that things were failing because of a ‘Mandatory IE’ missing or incorrect. I did not understand what they were saying. But google did, and found this part of the Cisco bookshelf.

This seems to be an error with the carrier systems as far as I can tell right now with the setup of the GTP, or ‘GPRS Tunneling Protocol’. Until today I did not even know that this existed… Google also found an etsi standard document that describes some of the GTP for GPRS and UMTS. ARGH.

Most interesting is that Ethereal has GTP built in as a protocol allowing it to be used by carriers to debug their systems. I think this is fairly amazing. Then again, that really does make sense… When debugging massive systems you need all the help you can get.