Hi, Martin and Mik! Additionally to Mik:
1)MAP version (or more exactly Application Context version) is defined for separate MAP procedure (e.g. Update_Location, Purge_MS, MT_Forward_SM) – not for overall MAP release.
2) SCCP segmentation (XUDT) is defined for overall MAP release and not recomended for high priority message and inter-PLMN message. There is no evident correlation between AC version and SCCP segmentation using. SCCP segmentation may be used for all AC versions of some procedures according 29.002.
3)Telecommunication network is evolved and the MAP is evolved together with it. The reasons for AC version change are: addition of new parameters in message, new cause values; unconfirmed procedure became confirmed (for example Alert_SC v1 is unconfirmed, but Alert_SC v2 is confirmed) etc.