[Detnet] Promised comments on draft-ietf-detnet-architecture

[Lou Berger <[e-mail]>]

Hi,

     I have a number of high level comments on the document that I'd 
like to raise below.  I also have a number of more editorial/specific 
comments that I'd like to review directly with the authors and then have 
them report back on changes -- if any turn out to be more substantive 
discussions from the author's perspective, I'll raise these on the list 
separately.

My higher level comments are:

- Support for out of order delivery (or miss-ordering) has come up a few 
times and looks like at least some will be allowed in the data plane 
solutions being discussed.  I suggest that the architecture reflect 
this, perhaps by inserting a new subsection before 3.2.4. noting that 
DetNet service should include maximum allowed miss-ordering as a 
constraint, and that some specific (small) value be allowed - of course 
zero miss-ordering would be a valid service constraint.

- While the document discusses how you can have overlapping or nested 
service protection, it does so without reusing the very useful concept 
of "protection domains" that was formalized in RFC6372.  A related, but 
more minor point: I suggest that the document add this term to the 
definitions section and use while describing Service Protection.  I also 
suggest that the "DetNet Service Protection" term be used in place of 
packet replication and elimination when the architectural concept is 
being referenced vs a specific implementation. (I'll provide specific 
examples for both to the authors.)

- WRT Section 4.4.3, I think the inclusion of a distributed control 
plane in the "Network Plane" is inconsistent with other functional 
definitions and conflates where a function resides from the actual 
function and that whether control is implemented in a fully centralized, 
fully distributed or some hybrid form doesn't fundamentally change  the 
control function's role -- therefore I think the sections 4.4.2 and .3 
should be revised accordingly

- In several places it's not clear that DetNet service is always a L3 
service which is controlled using L3 identifiers, i.e., IP addresses -- 
this is true even in the MPLS service case and the TSN over MPLS case.  
I think this is an important point to be clear on in the document.

Please let me know what you think.

Cheers,

Lou