This document defines PCEP extensions for grouping two unidirectional
MPLS-TE LSPs into an Associated Bidirectional LSP.
Specifically, this document defines two new
Association Types, "Single-sided Bidirectional LSP Association" and
"Double-sided Bidirectional LSP Association", as well as
"Bidirectional LSP Association Group TLV" to carry additional
information for the association.

Comments:

Thank you for including Section 8, Manageability Considerations.

I'm seeking clarification for the following requirement (although it may be completely clear to those who are knee-deep in this terminology):

Section 4.1
...
   o  The Tunnel (as defined in [RFC3209]) of forward and reverse LSPs
      of the Single-sided Bidirectional LSP Association on the
      originating endpoint node MUST be the same, albeit with reverse
      endpoint nodes.

as currently written, the requirement says that 
two preceding nouns MUST be the same. 

But is it: 
"The Tunnel *containing the* forward and reverse LSPs..."?
Or is it, 
"The *Tunnels associated with the* forward and reverse LSPs ..." ?
Or something else?

[RFC3209] simple definitions are (both seem to be unidirectional):
   LSP Tunnel
      An LSP which is used to tunnel below normal IP routing and/or
      filtering mechanisms.
   Traffic Engineered Tunnel (TE Tunnel)
      A set of one or more LSP Tunnels which carries a traffic trunk.

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Another request for clarification:
5.6.  State Synchronization
   During state synchronization, a PCC MUST report all the existing
   Bidirectional LSP Associations to the Stateful PCE as per [RFC8697].
   After the state synchronization, the PCE MUST remove all stale
   Bidirectional LSP Associations.

What is the procedure to determine a stale association, a time-out
or simply the absence of a previously association in a report?
Is there a passage covering stale determination in 8697, another 
reference, or a passage in the current memo that I missed?
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Editorial:
4.2.  Bidirectional LSP Association Group TLV

   The "Bidirectional LSP Association Group TLV" an OPTIONAL TLV for use
s/an/is an/