Last Call Review of draft-ietf-spring-srv6-network-programming-17
review-ietf-spring-srv6-network-programming-17-opsdir-lc-romascanu-2020-08-20-00

This document together with the companion document
[I-D.filsfils-spring-srv6-net-pgm-illustration] defines the SRv6 Network
Programming concept and specifies the main segment routing behaviors to enable
the creation of interoperable overlays with underlay optimization (Service
Level Agreement).

The document is Ready.  There are a number of issues from an Operations and
Management perspective that need further work, and it is assumed that they will
be subject to work in the future. Some clarification on these issues would be
however welcome before document approval.

There are several references that are work-in-progress. For example basic
concepts need to be understood from
[I-D.filsfils-spring-srv6-net-pgm-illustration]. The control plane interaction
is based on BGP-LS  [I-D.ietf-idr-bgpls-srv6-ext] or on BGP IP/VPN/EVPN
[I-D.ietf-bess-srv6-services]. These documents are listed as Informative
References probably in order to avoid a downref for this Standards Track
document, but actually this document cannot be implemented or even understood
without stable versions of the later.

From the operators point of view I would like to draw the attention on Sections
6 and 8. - Section 6 (Operation) recommends the implementation of a implement a
combined traffic counter (packets and bytes) per local SID entry. There is no
indication how an operator would retrieve this information and if and how the
values of these counters could be used for operational purposes. Adding such
information would be useful. - Section 8 (Control Plane) describes how the
controllers can explicitly provision the SIDs and/or discover them as part of a
service discovery function. Subsections describe the usage of IGP, BGP-LS, and
BGP IP/VPN/EVPN for these purposes. Operators should be aware that one or more
of these protocols also need to be supported in an SDN deployment.