[Raw] WG Last Call: draft-ietf-raw-architecture-11 - David Black's comments

["Black, David" <[e-mail]>]

Lou and Janos (detnet chairs) asked me to take a look at this draft – these comments are posted as an individual, not in my role as a Technical Advisor to the detnet WG.  I actually looked at -12, which has some minor changes from -11.

Overall, there are valuable and important concepts in the architecture.  The primary functional additions of raw over detnet that I noticed are the concepts of multi-Path Tracks and the PSE (Path Selection Engine) that can select Path within Track on a packet-by-packet basis, with the control path revising Tracks on a longer timescale.  That’s more dynamic than the static path provisioning that is envisioned by detnet, e.g., in the discussion of explicit routes in section 3.2.2 of RFC 8655 (Deterministic Networking Architecture).  In addition, the ability of the PSE to monitor, react to, and possibly modify wireless link characteristics (e.g., monitor level of interference and signal loss, modify ARQ & FEC parameters) results in a significantly more dynamic version of detnet PREOF, although I’m not convinced that introducing the new PAREO term and acronym is a productive way of describing that.

Unfortunately, the OODA Raw Control Loop in Section 5 doesn’t work well with this, as exemplified by Figure 8 showing only one control loop that runs through a centralized PCE (Path Computation Engine).  There is a far more important control loop that runs between the PSE and the network, based on far more information than RAW OAM (in Figure 8) provides.  While the draft does characterize the PCE as an example of a control plane structure, it doesn’t have much to say about any others.  That’s too easy to read as reinventing the detnet control plane, which would not be a good idea.

This draft would be considerably stronger if it jettisoned the PCE and its Figure 8 coarse control plane feedback loop to focus on the PSE and its fine-grain path selection feedback loop.  In particular, there’s a lot of good content in Figure 10 that deserves much more explanation than currently provided in sections 5.5 and 5.6.   This sort of approach would involve extending the detnet architecture to introduce Tracks as the entities via which traffic is explicitly “routed” by the detnet/raw control plane.  Section 4 also needs work, as it places the PSE in the detnet service sub-layer with the premise that it uses the detnet forwarding sub-layer with minor changes.  That doesn’t make sense – to phrase this as a question: Given that the PSE is selecting Path within Track on a packet-by-packet basis, how and why is that not packet forwarding functionality?

This is intended as constructive criticism for discussion – as I’ve not been following raw closely, some portion of this is likely to be incorrect in some fashion.

Thanks, --David

From: detnet <[e-mail]> On Behalf Of Eve Schooler
Sent: Friday, June 23, 2023 1:11 PM
To: [e-mail]; [e-mail]
Cc: [e-mail]; [e-mail]; John Scudder
Subject: [Detnet] WG Last Call: draft-ietf-raw-architecture-11


[EXTERNAL EMAIL]

All,



This starts working group last call on draft-ietf-raw-architecture-11

https://datatracker.ietf.org/doc/draft-ietf-raw-architecture/ [datatracker.ietf.org]<https://urldefense.com/v3/__https:/datatracker.ietf.org/doc/draft-ietf-detnet-pof/__;!!LpKI!gwAT9SygbUUZ8R5o9vGdxPNzKSMI44j13KrTFoVFxilR3iN3ZAcjdFYU1uqKEJwOtjWHwje5_7am6fHX4_EpuxQ$>



The working group last call ends on Friday, July 21st, the Friday before IETF 117.

Please send your comments to the working group mailing list.



Two IPR disclosures have been made for this document thus far (in tandem with WGLC, in a separate e-mail, we will solicit all co-authors/contributors for any additional disclosures).

All comments, e.g., "I've reviewed this document and believe it is ready for publication", are welcome.

This is useful and important, even from authors.

In preparation for the transition of the RAW WG to roll back into the DetNet WG, we are issuing this as a joint WGLC to both WGs.

Thank you,

Eve (RAW Co-Chair & doc Shepherd)