When is S1-AP over M2UA required?

Question

I came across a S1-AP pcap, some time back, in which the SCTP dest port was M2UA but the PPID was 18(S1-AP). In what scenario is M2UA encapsulation over SCTP used when SCTP has 36412 port reserved for S1-AP? (I am trying to get hold of that pcap)

Comments

Never heard of something like this, and assume this happens then both eNB and MME need to have this. And what it will gain from M2UA specially which provides only SG-ASP mode....Put at some common location and share the pcap...