[i2rs] Benjamin Kaduk's No Objection on draft-ietf-i2rs-yang-l2-network-topology-14: (with COMMENT)

Benjamin Kaduk via Datatracker <noreply@ietf.org> Tue, 07 July 2020 01:35 UTC

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Subject: [i2rs] Benjamin Kaduk's No Objection on draft-ietf-i2rs-yang-l2-network-topology-14: (with COMMENT)
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Benjamin Kaduk has entered the following ballot position for
draft-ietf-i2rs-yang-l2-network-topology-14: No Objection

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----------------------------------------------------------------------
COMMENT:
----------------------------------------------------------------------

Why is the "management-address" for a l2-node an IP address?  Does that
exclude any potential use of this data model for non-IP networks?

Section 3

   o  Links in the "ietf-network-topology" module are augmented as well
      with a set of Layer 2 parameters, allowing to associate a link
      with a name, a set of Layer 2 link attributes, and flags.

Interesting that names for links were not part of the core
network-topology module.  Are there any potential issues if other
ntework types also specify a link name and there is disagreement between
them?

Section 4

It reads a little oddly to use the flag-identity as the base type of a
typedef before the identity itself is declared, but I am way out of my
league here and defer to the YANG experts.

       description
         "VXLAN Network Identifier or VXLAN Segment ID.
          It allows up to 16 M VXLAN segments to coexist
          within the same administrative domain.

          The use of value '0' is implementation-specific.";

Is this intended as a nod to the use of 0 for the management VLAN?/
(I seem to recall this topic raising to some level of controversy in the
discussions around draft-ietf-bfd-vxlan.)

     /*

      * Features
      */

nit: there seems to be a spurious blank line here.

     grouping l2-node-attributes {
         [...]
         leaf sys-mac-address {
           type yang:mac-address;
           description
             "System MAC address.";
         }

Is there only one "System MAC address" per node?

         leaf delay {
           type uint32;
           units "microseconds";
           description
             "Link delay in microseconds.";

I guess we don't expect to use this model for deep-space links :)

       container l2-termination-point-attributes {
         description
           "Containing L2 termination point attributes.";
         leaf description {
           type string;
           description
             "Port description.";

Is a termination point always a "port", or should the description be
modified?

             list qinq {
               [...]
               leaf svlan-id {
                 type dot1q-types:vlanid;
                 description
                   "SVLAN ID.";
               }
               leaf cvlan-id {
                 type dot1q-types:vlanid;
                 description
                   "CVLAN ID.";

Could we perhaps expand "service" and "customer"?

           }
           //case ethernet

RFC 6020 suggests that YANG comments are "C++-style", which would seem
to indicate that the single-line comment could start on the same line as
the closing brace.  This, in turn, would save some confusion since the
block comments apply to the content after the comment, but these
comments apply to the content before the comment.
(Also later on as well.)

         leaf tp-state {
           [...]
             enum others {
               value 4;
               description
                 "The termination point is in other state.";
             }

Is there a plan for how substructure of these "others" states might be
added in the future?

Section 6

Thank you for updating the privacy considerations in response to the
secdir review!

   In the case of a topology that is configured, i.e. whose origin is
   "intended", the undesired configuration could become effective and be

Perhaps toss the word "datastore" in here somewhere to remind the
less-clueful reader (i.e., me) that origin is an NMDA concept?  Though
if it's sufficiently obvious, no need to do it just for me.

   reflected in the operational state datastore, leading to disruption
   of services provided via this topology might be disrupted.  For those

nit: deduplicate "disruption"/"disrupted".

   reasons, it is important that the NETCONF access control model is
   vigorously applied to prevent topology misconfiguration by
   unauthorized clients.

Should we condense "NACM" here since we provided the acronym at the
start of the paragraph?

   o  l2-node-attributes: A malicious client could attempt to sabotage
      the configuration of important node attributes, such as the name
      or the management-address.

I don't feel a need for a text change here (since "such as" suffices),
but would a change to the node's MAC address be similarly impactful?

   Some of the readable data nodes in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control read access (e.g., via get, get-config, or
   notification) to these data nodes.  In particular, the YANG model for
   layer 2 topology may expose sensitive information, for example the
   MAC addresses of devices.  Unrestricted use of such information can

I think I've been told that in some environments the topology itself
(especially VLAN/VXLAN identifiers) can be considered sensitive.  What's
written here is consistent with that, and I don't insist on a change to
the text, but wondered if that was seen as a common enough thing to be
worth mentioning.

Section 8.1

RFC 3688 could arguably be demoted to informative, as could RFC 7951.

Section 8.2

If we use types defined in [IEEE802.1Qcp], that seems like a normative
reference to me.

Noting the discussion at
https://www.ietf.org/about/groups/iesg/statements/normative-informative-references/
about even optional features still being normative references, I think
RFC 7348 would be better placed as a normative reference.  Note that
there is not a process/downref issue in doing so, since it is already
listed at https://datatracker.ietf.org/doc/downref/

I could go either way (informative or normative) for RFC 8342;
presumably there's a convention to stick to.

Appendix B

I was going to reference
https://www.iab.org/2016/11/07/iab-statement-on-ipv6/ and suggest IPv6
addresses as example management-addresses, but I have a lingering memory
that the IPv4 form is still used to identify nodes even in v6-only
environments.  Do the right thing, of course.

[Note that I did not do an extensive consistency/sanity check on the
example topology or try to reconstruct it from the JSON.]