Dear all,   I have reviewed this document as part of the operations directorate's ongoing effort to review all IETF documents being processed by the IESG. These comments were written primarily for the benefit of the operations area directors. Document editors and WG chairs should treat these comments just like any other last call comments.    Control plane extension is used for tree selection notification. I see the advantage of it to use the exiting hardware with software upgrading only. Such feature is of great value for deployment.   Section 5.7 After sentence about tunnelling, another sentence could be added as following. “It should be noted that tunneling would require silicon change though CMT itself is software upgrading only.”   It can be also added in the introduction or abstract, CMT method doesn’t need hardware upgrade, this is the biggest advantage of CMT.     Thank you, Tina