Reviewer: Linda Dunbar
Review result: Has Nits  & with comment

I am the assigned Ops area reviewer for this draft. The Ops directorate reviews all IETF documents being processed by the IESG for the IETF Chair.  Please treat these comments just like any other last call comments.

This document is written very clear, specifying a framework for a new device to securely join a 6TiSCH network. 

One question: the document assumes that there is pre-shared key (PSK) between the device and the controller. The Security Consideration does describe the common pitfall of  a single PSK shared among a group of
devices. 
Is there any way to prevent it? Is it necessary to require the Key to be periodically changed? 

Another  suggestion: 
Section 5.1 introduces an acronym ASN to represent "Absolute slot number". 

Can you use a different acronym because ASN has been widely used in networking as the Autonomous System Number.  
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An autonomous system number (ASN) is a unique number that's available globally to identify an autonomous system and which enables that system to exchange exterior routing information with other neighboring autonomous systems.

Thank you. 

Linda Dunbar