A YANG Data Model for Wavelength Switched Optical Networks (WSONs)
Extracted elements (18)
Impairment-aware optical networks and flexi-grid are explicitly out of scope; separate YANG models ([OPT-IMPAIR-AWARE-YANG] and [FLEXI-GRID-YANG]) address those cases. Transponder models and resource block models (e.g., 3R) are also excluded, narrowing this document to fixed-grid transparent WSON topology.
The model references the ITU-T G.698.2 standard application mode for amplified multichannel DWDM with single-channel optical interfaces, constraining the scope to this specific deployment scenario and ensuring channel numbering (dwdm-n, cwdm-n) aligns with ITU-T grid definitions.
The WSON topology model is structured as a YANG augmentation of the generic TE topology module (ietf-te-topology, RFC 8795) rather than as a standalone model. This allows WSON-specific attributes to reuse the common TE topology framework including connectivity matrices, tunnel termination points, and label restriction structures without duplicating them.
The model augments five distinct attachment points in the TE topology: te-node-attributes (connectivity-matrices and information-source-entry), tunnel-termination-point (local-link-connectivities), te-link-attributes, and link-template. Implementations must handle all five contexts to fully support WSON topology representation.
The YANG data model is derived from the WSON information model (RFC 7446) and protocol-independent encodings (RFC 7581, RFC 7579). Implementations should understand these underlying information models to correctly interpret the grid-type, channel spacing, and label range semantics exposed by this module.
All WSON-specific augmentations (node attributes, link attributes, tunnel termination points, connectivity matrices) include a 'when' expression that requires 'wsont:wson-topology' to be present in the network's network-types. Augmentation parameters apply only for networks with the WSON topology type.
The YANG data model MUST be used via NETCONF (RFC 6020, RFC 8341) or RESTCONF (RFC 8040), and MUST conform to the Network Management Datastore Architecture (NMDA) as defined in RFC 8342.
The 'ietf-wson-topology' YANG module (namespace 'urn:ietf:params:xml:ns:yang:ietf-wson-topology', prefix 'wsont', YANG version 1.1) is a technology-specific augmentation of ietf-te-topology (RFC 8795) for WSON routing and wavelength assignment. It imports ietf-network and ietf-network-topology (RFC 8345), ietf-te-topology (RFC 8795), and ietf-layer0-types (RFC 9093).
The l0-label-range-info grouping from ietf-layer0-types (RFC 9093) is augmented into label-restriction nodes throughout the WSON topology model, adding 'grid-type' (identityref) and 'priority' (uint8) to describe optical grid constraints for nodes, links, connectivity matrices, and tunnel termination points.
The 'wson-node' presence container augments TE node attributes and carries the boolean leaf 'is-reconfigurable-node' (default true). A value of true identifies a Reconfigurable Optical Add/Drop Multiplexer (ROADM); false identifies a Fixed Optical Add/Drop Multiplexer (FOADM).
The 'wson-topology' presence container augments the TE topology network-types node to declare a WSON topology type. Its presence alone signals that the enclosing network instance is a WSON topology and activates all other WSON-specific augmentations via YANG 'when' conditions.
IANA registers the 'ietf-wson-topology' YANG module in the 'IETF XML Registry' with namespace URI 'urn:ietf:params:xml:ns:yang:ietf-wson-topology' and in the 'YANG Module Names' registry with prefix 'wsont', referencing RFC 9094.
Read-only (ro) information-source-entry nodes expose the WSON topology as understood from routing protocols. Access to this state data should be appropriately restricted as it reveals the optical network topology, which may be sensitive from an operational security perspective.
The 'ietf-wson-topology' module defines numerous writable (rw) data nodes including the wson-topology network type, the is-reconfigurable-node flag, grid-type, priority, and label range/hop parameters. Unauthorized write access to these nodes via NETCONF or RESTCONF could misconfigure the WSON topology and disrupt optical channel assignments across the network.
Label step (channel spacing) for DWDM grids is encoded as 'wson-dwdm-channel-spacing' (identityref from l0-types) and for CWDM grids as 'wson-cwdm-channel-spacing' (identityref from l0-types), both appearing under the 'wson' case in the label-step technology choice.
WSON CWDM label range boundaries (label-start, label-end) are encoded via the 'cwdm-n' leaf (type l0-types:cwdm-n) representing the ITU-T CWDM channel number, used under the 'cwdm' case of the 'grid-type' choice in the wson-label-start-end grouping.
WSON DWDM label range boundaries (label-start, label-end) are encoded via the 'dwdm-n' leaf (type l0-types:dwdm-n) representing the ITU-T DWDM channel number, used under the 'dwdm' case of the 'grid-type' choice in the wson-label-start-end grouping.
WSON label hops (used in path elements for primary/backup underlay, explicit route include/exclude objects, and computed path route objects) use a 'single-or-super-channel' choice for DWDM: a single channel encodes 'dwdm-n' (l0-types:dwdm-n), while a super-channel encodes a list 'subcarrier-dwdm-n*' (l0-types:dwdm-n) identifying multiple subcarriers.