A couple of minor, non-blocking comments that I hope you'll consider:

-- Section 2 --
As RFC 6163 is used to define necessary terminology, I think it's a normative reference.

-- Section 3 --
I found the first paragraph here to be confusing: one thing can't be grouped into multiple categories, and "regardless" seems not the right word.  Also, the sentence (ending in ":") that introduces the list doesn't have anything to do with the list it introduces.

May I propose this instead, and let you fix it if I don't have it quite right?:

OLD
   The WSON RWA information model in this document is grouped into four
   categories regardless of whether they stem from a switching
   subsystem or from a line subsystem. A switching subsystem refers to
   WSON nodes such as ROADM or Optical Add/Drop Multiplexer (OADM) and
   a line subsystem refers to devices such as WDM or Optical Amplifier:
NEW
   The WSON RWA information model in this document comprises four
   categories of information. The categories are independent of
   whether the information comes from a switching subsystem or from a
   line subsystem -- a switching subsystem refers to WSON nodes such as
   ROADM or Optical Add/Drop Multiplexer (OADM), and a line subsystem
   refers to devices such as WDM or Optical Amplifier. The categories
   are these:
END