I have reviewed this document as part of the security directorate's
ongoing effort to review all IETF documents being processed by the
IESG. These comments were written primarily for the benefit of the
security area directors. Document editors and WG chairs should treat
these comments just like any other last call comments.

This draft defines some guidelines that tunneling protocols should
use to allow for ECN signals to propagate consistently. It is very 
well-written and describes the problem well. The Security 
Considerations are fine and discuss why hop-by-hop integrity of
ECN in not being proposed.

The summary of the review is "Ready", but with a small nit.
That nit is that figure 1 shows "subnet A" and "subnet B" but the
accompanying text talks about "subnet 2", should be "subnet B".