Hi, working on a diagnostic interface, I also ran into the lack of a gsmtap type for LTE NAS plain messages. So I am supporting Shinzo's request for a new GSMTAP_TYPE_LTE_NAS (or GSMTAP_TYPE_LTE_UU) type in packet-gsmtap.h.

This type would play a similar role to that of GSMTAP_TYPE_UM for GSM, if my understanding is correct.

Best regards, Martin

Unlike GSM and UMTS, LTE introduced separate layer for encryption of NAS and RRC. As a result, while NAS messages are piggybacked to LTE RRC, but after NAS security had been activated only encrypted NAS messages are available at RRC layer. This is reflected into the baseband diagnostics of various makers: Qualcomm provides separate diagnostic item for LTE NAS (both encrypted and plain) and RRC. Separate payload type for LTE RRC and LTE NAS will solve this issue. I can submit a patch if this looks positive.