Presentation of the MPTCP implementation

This is a presentation for a multipath TCP implementation for ns3 (www.nsnam.org).

This implementation started as a fork of https://github.com/mkheirkhah/mptcp but then diverged as I thought it would be best to have MPTCP subflows inherit TcpSocketBase. Thus it is based on ns.23 but I backported TCP options from Natale's GSoC 2015.

The implementation bit-wise and protocol-wise is already quite good though not robust enough: it is capable in some situations to talk to a linux MPTCP server (tried in DCE).

Nevertheless, many things are still missing, look at the github issue tracker to know which are the current problems.

I welcome small Pull Requests that would fix documentation, spelling mistake or bugs. If you decide to deal with a bug, please signal yourself first so that no effort is wasted.

Some patches are already in ns3 tracker and we expect to upstream the implementation in ns3.27.