Last Call Review of draft-ietf-isis-reverse-metric-13
review-ietf-isis-reverse-metric-13-secdir-lc-leiba-2018-10-04-00

This document is well written and seems ready to go.  The only security issue I
thought of as I read through it (attacking by spoofing a reverse metric) is
covered in the Security Considerations section.

I found one sentence to be slightly ambiguous, but only very slightly.  In
Section 3.5:

   A router MUST advertise a Reverse Metric TLV toward a neighbor only
   for the operational maintenance window period during which it wants a
   neighbor to temporarily update its IS-IS metric or Traffic
   Engineering parameters towards it.

It begins to look like it's saying that a router MUST advertise this under
certain conditions, and it took me a moment to get that it's actually
*limiting* when it should be advertised (the "MUST" applies to the "only"
clause).  If you think my suggested replacement reads well, you might use it;
if not, no problem:

   A router MUST limit the period during which it advertises a Reverse Metric
   TLV toward a neighbor only to the operational maintenance window period
   during which it wants that neighbor to temporarily update its IS-IS metric
   or Traffic Engineering parameters towards it.