Last Call Review of draft-ietf-opsawg-model-automation-framework-06
review-ietf-opsawg-model-automation-framework-06-tsvart-lc-pauly-2020-10-06-00

This document has been reviewed as part of the transport area review team's
ongoing effort to review key IETF documents. These comments were written
primarily for the transport area directors, but are copied to the document's
authors and WG to allow them to address any issues raised and also to the IETF
discussion list for information.

When done at the time of IETF Last Call, the authors should consider this
review as part of the last-call comments they receive. Please always CC
tsv-art@ietf.org if you reply to or forward this review.

This document describes an architecture for using YANG models in with automated
networks and services. The details of delivery (such as over L2 or L3 VPNs) is
not discussed in detail, and transport-specific details of that delivery seem
out of scope for this document. The primary intersection of this work with the
Transport Area is the integration with IPPM specifications and YANG modules.

Section 3.1 references several IPPM specifications (One-Way Delay/Loss metrics,
and Link Capacity). It may be good to reference the new IPPM registries for
metrics, which are currently in AUTH48
(https://www.iana.org/assignments/performance-metrics/performance-metrics.xhtml,
draft-ietf-ippm-metric-registry, draft-ietf-ippm-initial-registry). Also as a
nit, the link for “I-D.ietf-ippm-capacity-metric-method” doesn’t seem to be a
live hyperlink.

I am also a bit unclear about the way that these metrics are referenced. The
relevant text is:

For example, the service level
   can be used to characterise the network service(s) to be ensured
   between service nodes (ingress/egress) such as:
…
   o  the traffic performance guarantees (One-Way Delay (OWD) [RFC7679],
      One-Way Loss [RFC7680], ...),
   o  link capacity [RFC5136][I-D.ietf-ippm-capacity-metric-method],

This is the first place that “service level” is used as a term. Should this be
“Service Model” as is used earlier in the paragraph? It also seems a bit
problematic to reference these link metrics as “guarantees”; these metrics are
used to represent empirical measurements, but cannot guarantee behavior of a
link. Could we replace “guarantees” and “ensures” with other words, such as
“expected”/“expectations”?

I also agree with Christian’s secdir review comments, particularly with the
number of referenced documents and dependencies.