I am a routing naïf and do not have a lot of time these days. I hope this review is still useful, anyway.

The glossary was very helpful.  I still don't have a clear understanding of L1 and L2.

The picture is a tour de force.  The description "Figure 1 is an example..." paragraph should be moved before the picture, not directly after it.

Sections 6 and 7 indicate, to me, that this document is comprehensive and informed by real-world concerns.

Sec 9, Security Considerations.
This is where I did the most careful reading.
"If an attacker should be able..."  s/should be able/can/
s/could be in most extreme case/could be in THE most extreme case/
It was a bit surprising to me to see the same sentence at the end of both paragraph 1 and paragraph 2.  Maybe remove them and move them to the start of paragraph 3.

I think the risks are well-described, and the importance to preventing is made. Is it possible to mitigate the damage if a risk occurs?  "No" is a reasonable answer.