Early Review of draft-ietf-mpls-rmr-09

Request Review of draft-ietf-mpls-rmr-09
Requested rev. 09 (document currently at 12)
Type Early Review
Team Routing Area Directorate (rtgdir)
Deadline 2019-01-30
Requested 2019-01-15
Requested by Loa Andersson
Authors Kireeti Kompella, Luis Contreras
Draft last updated 2019-02-11
Completed reviews Rtgdir Early review of -09 by Susan Hares (diff)
Rtgdir Last Call review of -11 by Susan Hares (diff)
Tsvart Last Call review of -12 by Colin Perkins
Genart Last Call review of -12 by Francis Dupont
Secdir Last Call review of -12 by Derek Atkins
Opsdir Last Call review of -12 by Nagendra Kumar
I'm requesting a review to be done in parallel with the MPLS wg last call.
Assignment Reviewer Susan Hares
State Completed
Review review-ietf-mpls-rmr-09-rtgdir-early-hares-2019-02-11
Reviewed rev. 09 (document currently at 12)
Review result Not Ready
Review completed: 2019-02-11


This is a routing directorate review.  As such, it should be considered the same as other later WG LC review.

overall-comment: Well-written and an exciting new direction.  I appreciate Kireeti and Luis work on this topic. 

major concerns:  
1) security (section 8),  
2) long-term stability of architecture discussion,  
3) FRR/Protection sections (3.6/3.7), and
4) amount of traffic that auto-discovery will place on the network. 

caveat:  I have not been an WG participant for these discussions.   As such, I am a "fresh" pair of eyes to read the current specification.  

Major concerns 

1) Section 8 - Security considerations.  

"This section states 'It is not anticipated that either the notion of MPLS rings
or the extensions to various protocols to support them will cause security loopholes."

This statement provides an opinion of the authors without any reasoning behind it.  As such, it provide no utility to the reader.  Inquiring minds would like to know "why" the authors feel this true and on what basis.   Launching a new type of structure within the MPLS cloud that auto-configures it self with a great deal of message exchange does not appear to have these qualities.  Surely, these authors have considered or tried these issues. 

2) Long-term stability of document - in the face of repeated statements of a future version of this document. 

If this is just an interim document, then why is it being standardized.  In a specification that is going to include an RFC track, the sttaements of scope seem inappropriate in sections 1, 3.3, 4.5,  5, 7.1, and 7.2).  This scope should be gathered to a particular place and stated in another.   

I agree with the concept of deployment and then refinement of the protocol mechanisms.  However, this document seems to anticipate quick refinement of the basic architeture.  If this is really true, then why is this document going ot  the IESG.  If this is not true, then the scoping in above sections needs to be refined. 

3)  Fast re-routing installation puts details (3.6) before concepts of protection.  
Only after I read section 3.7, did section 3.6 start to make sense.   If you re-ordered the sections, perhaps you could provide additonal depth to section 3.6. 
4) paragraph 4.3, last sentence  "The nodes that set their M bit should be extra careful in advertising their M Bit in subsequent tries".   

As an engineering, I find this description to avoid many of the problems about how long the bidding for master will take.  Is there a potential for the bidding to repeat over and over.  If so, how does the operator detect it.  Can something drop the nodes into membership phase or re-identification phase repeated?   While the ring announcement and ring identification cycle become a denial-of-service attack on the IGPs announcing the information?  I suspect the authors have investigated these points, but the architeture document is the place to indicate why the architecture prevents these problems. 
As an editor, I find the anthropomorphism to be unwarranted in the text.  While it took me to flights of fantasy where the nodes became intelligent silicon life forms, I suspect that is not what the authors wanted.   Perhaps after clarifying the engineering point, the authors can rewrite the sense of the text.  

brief editorial nits: 

1) page 4, node index linke  
/upto/ to /up to/

2) page 5 (Q_jk): - not define earlier, please define it. 

3) page 5, section 3 paragraph 2, sentence file 

current: /The default is to send traffic along the shortest path./
new:  /The default policy is to send traffic along the shortest path./

4) page 6, section 3.3 sentences 2 

current:/ The last attribute means/
new: /The "auto-bundled" attribute means/

While the authors first formi is current, the change makes a specification clear. 

5) page 3.5 - please spell out the first use of UHP 
6) section 3.6/3.7 - could use a diagram.  
7) page 11, section 4.3, paragraph 2, sentence 2 (spelling) - 

old/exaclty one;/
new/exactly one/