Hi Harald,
in osmo-iuh/doc/hnb_cs_lu.msc I find that after the location update request from the UE, an identity request "should" follow from the CN.
Yesterday I made my first pcap using our hNodeB and that weighty black UE we use for testing, and saw that the MSC indeed sends out an identity request at that time [1], however, the UE simply never responds to it.
My question: is the hnb_cs_lu.msc declarative and definitely correct, or could it be that in 3G, UEs in general expect authentication first, as the "osmo-iuh/pcap/UPP RANAP.pcap" suggests (starting at packet #335).
Since my sources tell me (i.e. Daniel) that an identity request at that time is indeed kinda special practise by openbsc to collect all IMEIs we possibly can, I'm going for authentication first.
Just wanted to make sure you agree that the hnb_cs_lu.msc may be erratic in that case. Thanks!
~Neels
[1] near openbsc/src/libmsc/gsm_04_08.c:589 (thanks Daniel!)