Last Call Review of draft-ietf-teas-yang-te-topo-08
review-ietf-teas-yang-te-topo-08-yangdoctors-lc-jethanandani-2017-05-24-00

Document reviewed: draft-ietf-teas-yang-te-topo-08

Status: Ready with Issues

I am not an expert in Traffic Engineering. This review is looking at the draft
from a YANG perspective. With that said, I have marked it as “Ready with
Issues” because of some of the points discussed below.

Summary:

This document defines a YANG data model for representing, retrieving and
manipulating TE Topologies. The model serves as a base model that other
technology specific TE Topology models can augment.

Comments:

Almost all the containers in the model are presence containers. Is there a
reason why they have to be presence containers? Note, that presence containers
are containers whose existence itself represents configuration data. What
particular configuration data is each container representing in itself?

It is difficult to co-relate the diagram with the model itself because of
different terms being used to define different parts of the model. There is “TE
Topology Model” and then there is “Generic TE Topology Model”. Are these one
and the same models? If so, a common term for both of them would be helpful.

There is extensive use of groupings in the document. However, not all instances
of groupings are used multiple number of times. Where they are not being
repeated, it would be better to move the grouping directly where the uses
statement resides. Case in point the grouping
connectivity-label-restriction-list.

The split between config and state containers does not seem to follow any
particular pattern. It is neither a top level split, as is the case with
existing IETF models, nor do they follow the OpenConfig style of splitting
config and state under each relevant leaf, nor do they follow the new
guidelines as suggested by the new datastore model draft
(https://tools.ietf.org/html/draft-dsdt-nmda-guidelines-01.html). Since there
recommendation for all new models is to follow the new datastore guidelines,
would suggest that the state containers be removed and any non-duplicate leafs
within state be moved under a single container. I am told that the change in
ietf-te-topology from the current draft to NMDA style is about 175 lines and
for te-types it is 24 line diff (thanks Robert). As such, the change is not
major and can be done easily. See the diffs at the end of this review.

A pyang compilation of the model with —ietf and —lint option was clean.

A idnits run of the draft reveals some issues with spacing and references, but
they are parts of the diagram, which confuses idnits.

te-types.diff
—————
507,509c507,509
<   grouping explicit-route-hop_config {
<     description
<       "The explicit route subobject grouping";
---
>   grouping explicit-route-hop {
>     description "Explicit route hop grouping";
>
595,609d594
<     }
<   }
<
<   grouping explicit-route-hop {
<     description "Explicit route hop grouping";
<     container config {
<       description
<         "Configuration parameters for the explicit route hop";
<       uses explicit-route-hop_config;
<     }
<     container state {
<       config false;
<       description
<         "State parameters for the explicit route hop";
<       uses explicit-route-hop_config;

te-topology.diff
——————-
264a265
>       config false;
323a325
>       config false;
327a330
>       config false;
357a361
>       config false;
361a366
>       config false;
733,744c738,739
<       container config {
<         description
<           "Configuration data.";
<         uses te-link-config;
<       } // config
<       container state {
<         config false;
<         description
<           "Operational state data.";
<         uses te-link-config;
<         uses te-link-state-derived;
<       } // state
---
>       uses te-link-config;
>       uses te-link-state-derived;
780,781c775,776
<                 path "../../../../../../nw:node[nw:node-id = "
<                   + "current()/../../../../../nt:source/"
---
>                 path "../../../../../nw:node[nw:node-id = "
>                   + "current()/../../../../nt:source/"
792,793c787,788
<                 path "../../../../../../nw:node[nw:node-id = "
<                   + "current()/../../../../../nt:destination/"
---
>                 path "../../../../../nw:node[nw:node-id = "
>                   + "current()/../../../../nt:destination/"
841c836
<         path "../../../../../te/templates/link-template/name";
---
>         path "../../../../te/templates/link-template/name";
1087a1083
>       config false;
1092a1089
>       config false;
1106a1104
>       config false;
1113a1112
>       config false;
1128a1128
>       config false;
1267,1279c1267,1268
<       container config {
<         description
<           "Configuration data.";
<         uses te-node-config;
<       } // config
<       container state {
<         config false;
<         description
<           "Operational state data.";
<
<         uses te-node-config;
<         uses te-node-state-derived;
<       } // state
---
>       uses te-node-config;
>       uses te-node-state-derived;
1297,1309c1286,1287
<         container config {
<           description
<             "Configuration data.";
<           uses te-node-tunnel-termination-attributes;
<         }
<         container state {
<           config false;
<           description
<             "Operational state data.";
<
<           uses te-node-tunnel-termination-attributes;
<           uses geolocation-container;
<         } // state
---
>         uses te-node-tunnel-termination-attributes;
>         uses geolocation-container;
1406c1384
<         path "../../../../../te/templates/node-template/name";
---
>         path "../../../../te/templates/node-template/name";
1473,1474c1451
<               path "../../../../../../../nt:termination-point/"+
<                 "nt:tp-id";
---
>               path "../../../../../../nt:termination-point/nt:tp-id";
1485,1486c1462
<               path "../../../../../../../nt:termination-point/"+
<                 "nt:tp-id";
---
>               path "../../../../../../nt:termination-point/nt:tp-id";
1577a1554
>       config false;
1583a1561
>       config false;
1595a1574
>       config false;
1738c1717
<             path "../../../../../../nt:termination-point/nt:tp-id";
---
>             path "../../../../../nt:termination-point/nt:tp-id";
1753c1732
<     uses te-types:explicit-route-hop_config;
---
>     uses te-types:explicit-route-hop;
1773,1779c1752,1754
<       container config {
<         description
<           "Configuration data.";
<         uses te-termination-point-config;
<       } // config
<       container state {
<         config false;
---
>       uses interface-switching-capability-list;
>       leaf inter-layer-lock-id {
>         type uint32;
1781,1784c1756,1765
<           "Operational state data.";
<         uses te-termination-point-config;
<         uses geolocation-container;
<       } // state
---
>           "Inter layer lock ID, used for path computation in a TE
>            topology covering multiple layers or multiple regions.";
>         reference
>           "RFC5212: Requirements for GMPLS-Based Multi-Region and
>            Multi-Layer Networks (MRN/MLN).
>            RFC6001: Generalized MPLS (GMPLS) Protocol Extensions for
>            Multi-Layer and Multi-Region Networks (MLN/MRN).";
>       }
>
>       uses geolocation-container;
1787,1802d1767
<   grouping te-termination-point-config {
<     description
<       "TE termination point configuration grouping.";
<     uses interface-switching-capability-list;
<     leaf inter-layer-lock-id {
<       type uint32;
<       description
<         "Inter layer lock ID, used for path computation in a TE
<          topology covering multiple layers or multiple regions.";
<       reference
<         "RFC5212: Requirements for GMPLS-Based Multi-Region and
<          Multi-Layer Networks (MRN/MLN).
<          RFC6001: Generalized MPLS (GMPLS) Protocol Extensions
<          for Multi-Layer and Multi-Region Networks (MLN/MRN).";
<     }
<   } // te-termination-point-config
1879,1890c1844,1845
<       container config {
<         description
<           "Configuration data.";
<         uses te-topology-config;
<       } // config
<       container state {
<         config false;
<         description
<           "Operational state data.";
<         uses te-topology-config;
<         uses geolocation-container;
<       } // state
---
>       uses te-topology-config;
>       uses geolocation-container;