Hi Brian,
Thank you very much for your comments. Please see inline.

On Monday, February 19, 2018 6:22 PM, Brian Carpenter 
<brian.e.carpen...@gmail.com> wrote:


 

 Reviewer: Brian Carpenter
Review result: Ready with Issues

Gen-ART Last Call review of draft-ietf-6tisch-6top-protocol-09

I am the assigned Gen-ART reviewer for this draft. The General Area
Review Team (Gen-ART) reviews all IETF documents being processed
by the IESG for the IETF Chair.  Please treat these comments just
like any other last call comments.

For more information, please see the FAQ at
<http://wiki.tools.ietf.org/area/gen/trac/wiki/GenArtfaq>.

Document: draft-ietf-6tisch-6top-protocol-09.txt
Reviewer: Brian Carpenter
Review Date: 2018-02-20
IETF LC End Date: 2018-??-??
IESG Telechat date: 2018-03-06

Summary: Ready with issues
--------

Comment:
--------

This is a Last Call review despite the subject field. When will the Last
Call be started?

Major issues:
-------------

In section 3.1.1 "2-step 6P Transaction" there seems to be a race condition
if A's timeout expires while B's Response is in flight. Can the 6top layer
prevent the L2 Ack being sent? (And similar race conditions seem to be
possible in the 3-step transaction.)

[Qin] Firstly, sincethe L2 Ack is sent by L2 according to IEEE802.15.4, 6top 
layer cannot preventit happen. Secondly, the race condition described above 
unlikely happens,because it is required that “The value of the 6P Timeout 
should be larger thanthe longest possible time it can take for the exchange to 
finish.” (3.4.4)


> 3.4.3.  Concurrent 6P Transactions
>
>  Only a single 6P Transaction between two neighbors, in a given
>  direction, can take place at the same time.  That is, a node MUST NOT
>  issue a new 6P Request to a given neighbor before having received the
>  6P Response for a previous request to that neighbor, except when the
>  previous 6P Transaction has timed out.  If a node receives a 6P
>  Request from a given neighbor before having sent the 6P Response to
>  the previous 6P Request from that neighbor, it MUST send back a 6P
>  Response with a return code of RC_RESET (as per Figure 36).  A node
>  receiving RC_RESET code MUST abort the transaction and consider it
>  never happened.

It isn't clear to me whether the RC_RESET aborts the first, the second,
or both transactions.

[Qin] change textto “abort the second transaction”



Minor issues:
-------------

> 1.  Introduction
...
>  6P
>  allows a node to communicate with a neighbor to add/delete TSCH cells
>  to one another.

This sentence is almost unintelligible because of the sequence to...to...to.
Does it mean this?:

  6P allows neighbours to add or delete TSCH cells in each other.

[Qin] Because we want to emphasize that communication between two nodes is the 
way to add/deletecells, we change text to “6P allows a node to communicate with 
a neighbor toadd/delete TSCH cells in each other”



> 3.4.1.  Version Checking

This may be a pointless worry, but is there a DOS attack of some kind
by sending rubbish version numbers?

[Qin] I think thatnot only the field of Version Number, but also other fields, 
such as the fieldof Command Identifier can be filled with rubbish for DOS 
attack. So, I wonderif it is necessary for Version Number field to be treated 
differently. 

I would like asksecurity people to help on the question.


ThanksQin
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