23.401 said that SIPTO above RAN uses TAI during the DNS interrogation. But I could't find the DNS interrogation using TAI in TS29.303. Could you show me the way or doc. for easy understanding?
In order to select the appropriate PDN GW for SIPTO above RAN service, the PDN GW selection function uses the TAI (Tracking Area Identity), the serving eNodeB identifier, or TAI together with serving eNodeB identifier depending on the operator's deployment during the DNS interrogation as specified in TS 29.303  to find the PDN GW identity.