I found this talk from the linux.conf.au 2015 interesting <https://www.youtube.com/watch?v=_ahcUuNO4so> 34 minutes in talks about IPsec. Not the best part. The slides are <https://www.cs.auckland.ac.nz/~pgut001/pubs/crypto_wont_help.pdf> IPsec starts on page 51. Pages from Snowden start on 56. Perhaps worth puzzling over.