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

This document specifies a set of extensions to IGP to enable multiple topologies within one IGP domain, and each topology has its unique constraint-based path computation metric.  

It would be very helpful if Section 15 (Operational Consideration) included some considerations on the number of topologies to be created for exemplary deployments. Even though theoretically, hundreds/thousands of topologies can be supported by the mechanisms described in the draft, in practice, probably only a handful of (or even fewer) Flex-Algorithms are needed per IGP domain. It would be so much easier to follow the document if knowing only two or three Flex-Algorithm are needed. 

Thank you
Linda Dunbar