I am a newbie too. There are experts around here. It's better you post your question as a topic or google it like "ns-3 mpls".
In my case, I googled something like "ns-3 mesh" or "ns-3 802.11s" which is IEEE standard (it is actually a draft now) I've been working on, I found some research efforts in this field which are in form of academic papers and I ended up having guidance of those papers.
Sorry for my incapability of answering your question. Good luck for your work.