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title: "A YANG Data Model for Flexi-Grid Optical Networks" abbrev: "Flexi-Grid YANG" category: std

docname: draft-ietf-ccamp-flexigrid-yang-latest submissiontype: IETF # also: "independent", "editorial", "IAB", or "IRTF" number: date: consensus: true v: 3 area: "Routing" workgroup: "CCAMP Working Group" keyword:

author:

ins: J.E. Lopez de Vergara
name: Jorge E. Lopez de Vergara Mendez
org: Naudit HPCN
email: [email protected]

contributor:

name: Oscar Gonzalez de Dios
ins: O. Gonzalez de Dios
org: Telefonica
email: [email protected]

normative: ITU-T_G.694.1: title: "Spectral grids for WDM applications: DWDM frequency grid" author: org: ITU-T Recommendation G.694.1 date: October 2020 seriesinfo: ITU-T G.694.1 ITU-T_G.872: title: Architecture of optical transport networks author: org: International Telecommunication Union date: January 2021 seriesinfo: ITU-T G.872 Amendment 1

--- abstract

This document defines a YANG module for managing flexi-grid optical networks. The model defined in this document specifies a flexi-grid traffic engineering database that is used to describe the topology of a flexi-grid network. It is based on and augments existing YANG models that describe network and traffic engineering topologies.

--- middle

Introduction

The flexible grid (flexi-grid) optical network technology defined by the International Telecommunication Union Telecommunication Standardization Sector (ITU-T) and documented in Recommendation ITU- T_G.694.1 {{ITU-T_G.694.1}} and ITU-T_G.872 {{ITU-T_G.872}} provides an enhanced Dense Wavelength Division Multiplexing (DWDM) grid by defining a set of nominal central frequencies, slot widths, and the concept of the "frequency slot". This technology increases both transport network scalability and flexibility, allowing the optimization of bandwidth usage.

{{?RFC7698}} provides a framework for GMPLS-Based control of flexi-grid DWDM networks while {{!RFC7699}} defines generalized labels for the use of GMPLS in flexi-grid networks.

{{!RFC8363}} provides extensions to the OSPF-TE protocol so as to support GMPLS control of flexi-grid networks.

This document presents a YANG data model {{!RFC7950}} for flexi-grid objects in the dynamic optical network, including nodes, transponders and links, as well as how such links interconnect nodes. This model is independent of control plane protocols.

This document identifies the flexi-grid components, parameters, and their values. It characterizes the features and the performances of the flexi-grid elements. For this, it augments {{!RFC8795}}, and imports the generic Layer 0 types and use of "media-channel" defined in {{!I-D.ietf-ccamp-rfc9093-bis}}.

An application example in {{example}} is also provided to better understand the utility of this YANG model.

A partner document defines a second YANG module that described flexi- grid tunnels, i.e., the paths from source to destination through a number of intermediate nodes {{?I-D.ietf-ccamp-flexigrid-tunnel-yang}}.

Impairment-aware traffic engineering topology is described in {{?I-D.ietf-ccamp-optical-impairment-topology-yang}}.

The YANG data model defined in this document conforms to the Network Management Datastore Architecture (NMDA) {{!RFC8342}}.

Terminology

Refer to {{?RFC7698}} and {{!RFC7699}} for the key terms used in this document.

The following terms are defined in {{!RFC7950}} and are not redefined here:

  • client

  • server

  • augment

  • data model

  • data node

The following terms are defined in {{!RFC6241}} and are not redefined here:

  • configuration data

  • state data

The terminology for describing YANG data models is found in {{!RFC7950}}.

Tree Diagram

A simplified graphical representation of the data model is used in this document. The meaning of the symbols in these diagrams is defined in {{?RFC8340}}.

Prefixes in Data Node Names

In this document, names of data nodes and other data model objects are prefixed using the standard prefix associated with the corresponding YANG imported modules, as shown in {{tab-prefixes}}. It uses prefixes from {{!I-D.ietf-ccamp-rfc9093-bis}}, {{!RFC8345}}, and {{!RFC8795}}.

| Prefix | YANG module | Reference | |-------------|--------------------------|-----------------+ | l0-types | ietf-layer0-types | [RFCYYYY] | | flexgt | ietf-flexi-grid-topology | RFC XXXX | | nw | ietf-network | {{!RFC8345}} | | nt | ietf-network-topology | {{!RFC8345}} | | tet | ietf-te-topology | {{!RFC8795}} | {: #tab-prefixes title="Prefixes and corresponding YANG modules"}

RFC Editor Note: Please replace XXXX with the RFC number assigned to this document. Please replace YYYY with the RFC numbers assigned to {{!I-D.ietf-ccamp-rfc9093-bis}}. Please remove this note.

{: #example}

Example of Use

In order to explain how this model is used, we provide the following example. An optical network usually has multiple transponders, switches (nodes) and links. {{fig-topo}} shows a simple topology.

      +----------+                                        +----------+
      |  Flexi-  |                                        | Flexi-   |
      |   grid   |                                        |  grid    |
      |  node A  |                                        | node E   |
      |          |        +------+        +------+        |          |
      |          | Link 1 |Flexi-| Link 2 |Flexi-| Link 3 |          |
      |          |<------>| grid |<------>| grid |<------>|          |
      |......... |        |node B|        |node C|        | .........|
      | Trans- : |        +------+        +------+        | : Trans- |
      | ponder : |                                        | : ponder |
      |    A   : |              +----------+              | :    E   |
      |........: |     Link 4   |Flexi-grid|   Link 5     | :........|
      |          |<------------>|   node   |<------------>|          |
      |          |              |    D     |              |          |
      |          |              +----------+              |          |
      +----------+                                        +----------+

{: #fig-topo title="Topology Example"}

In order to configure a flexi-grid network to interconnect transponders A and E, first of all we have to populate the flexi-grid topology YANG model with all elements in the network:

  • We define the transponders within nodes A and E as tunnel termination points (TTPs) and provide their internal local link connectivity towards the node interfaces. We also provide the identifiers, addresses and interfaces of nodes A and B.

  • We do the same for the nodes B, C and D, providing their identifiers, addresses and interfaces, as well as the internal connectivity matrix between interfaces.

  • Then, we also define the links 1 to 5 that interconnect nodes, indicating which flexi-grid labels are available.

  • Other information, such as the slot frequency and granularity are also provided.

YANG Data Model for Flexi-Grid Topology

Flexi-Grid Topology Data Model Overview

This document describes the data model for flexi-grid topology. As a classic traffic engineering (TE) technology, flexi-grid provides WDM switching in transport network. Therefore the YANG module presented in this document augments from a more generic TE network topology data model, i.e., the ietf-te-topology, as specified in {{!RFC8795}}, following the guidelines provided in section 6 of {{!RFC8795}}.

Common types, identities, and groupings defined in {{!I-D.ietf-ccamp-rfc9093-bis}} are reused in this document.

The figure below shows the augmentation relationship between YANG models.

                        +-------------------------+
           TE generic   |    ietf-te-topology     |
                        +-------------------------+
                                     ^
                                     |
                                     | Augments
                                     |
                        +------------+-------------+
           Flexi-Grid   | ietf-flexi-grid-topology |
                        +--------------------------+

{: #fig-model-hierachy title="Relationship between Flexi-Grid and TE topology models"}

The entities and TE attributes, such as node, termination points and links, are still applicable for describing a flexi-grid topology and the model presented in this document only specifies the technology- specific attributes/information.

The flexi-grid specific attributes and label format is defined in {{!RFC7699}}, including the grid type, nominal central frequency granularity, slot width granularity, n and m parameters. A collection of common data types have also been specified in {{!I-D.ietf-ccamp-rfc9093-bis}}, and used in this document for augmentation of the generic TE topology model.

The YANG module ietf-flexi-grid-topology defined in this document conforms to the Network Management Datastore Architecture (NMDA) defined in {{!RFC8342}}.

Augmentations for Flexi-Grid Topology and Node

There are a few characteristics augmenting to the generic TE topology.

Following the guidelines in {{!RFC8795}}, a flexi-grid-topology network- type is specified as the indicator of flexi-grid in the topology as shown in {{fig-network-type}}.

       augment /nw:networks/nw:network/nw:network-types/tet:te-topology:
         +--rw flexi-grid-topology!

{: #fig-network-type title="Flexi-Grid Topology Augmentation"}

A flexi-grid-node presence container is specified, augmenting the generic TE node attributes, to indicate that the TE node is a Flexi- Grid node as shown in {{fig-node-type}}.

          augment /nw:networks/nw:network/nw:node/tet:te
                  /tet:te-node-attributes:
            +--rw flexi-grid-node!

{: #fig-node-type title="Flex-Grid Node Augmentation"}

It is assumed that all the flexi-grid nodes are reconfigurable.

Bandwidth Augmentation

No bandwidth augmentations are needed for this YANG module.

As described in Section 4.2 of {{!RFC7699}}, there is some overlap between bandwidth and label in Layer 0.

The flexi-grid label resource information described in {{flexi-label}}, is sufficient to also describe the spectrum resources within a flexi- grid network. Therefore, the model does not define any augmentation for the te-bandwidth containers defined in {{!RFC8795}}.

{: #flexi-label}

Label Augmentation

The model augments all the occurrences of the label-restriction list in {{!RFC8795}} with flexi-grid technology specific attributes using the flexi-grid-label-range-info grouping defined in {{!I-D.ietf-ccamp-rfc9093-bis}}.

Moreover, following the guidelines in {{!RFC8795}}, the model augments all the occurrences of the te-label container with the flexi-grid technology specific attributes using the flexi-grid-label-start-end, flexi-grid-label-hop and flexi-grid-label-step groupings defined in {{!I-D.ietf-ccamp-rfc9093-bis}}.

YANG Model (Tree Structure) for Flexi-Grid Topology

{::include ./ietf-flexi-grid-topology.tree}

{: #fig-flexig-topo-tree artwork-name="ietf-flexi-grid-topology.tree"}

The YANG Code for Flexi-grid topology

{::include ./ietf-flexi-grid-topology.yang}

{: #fig-flexig-topo-yang sourcecode-markers="true" sourcecode-name="[email protected]"}

Security Considerations

The YANG module specified in this document defines a schema for data that is designed to be accessed via network management protocols such as NETCONF {{!RFC6241}} or RESTCONF {{!RFC8040}}. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) {{!RFC6242}}. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is Transport Layer Security (TLS) {{!RFC8446}}.

The NETCONF access control model {{!RFC8341}} provides the means to restrict access for particular NETCONF users to a preconfigured subset of all available NETCONF protocol operations and content. The NETCONF Protocol SSH {{!RFC6242}} describes a method for invoking and running NETCONF within a SSH session as an SSH subsystem. The Network Configuration Access Control Model (NACM) {{!RFC8341}} provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content.

A number of configuration data nodes defined in this document are writable/deletable (i.e., "config true"). These data nodes may be considered sensitive or vulnerable in some network environments.

There are a number of data nodes defined in this YANG module that are writable/creatable/deletable (i.e., config true, which is the default). These data nodes may be considered sensitive or vulnerable in some network environments. Write operations (e.g., edit-config) to these data nodes without proper protection can have a negative effect on network operations. These are the subtrees and data nodes and their sensitivity/vulnerability:

      /nw:networks/nw:network/nw:network-types/tet:te-topology
      /nw:networks/nw:network/nt:link/tet:te/tet:te-link-attributes
      /nw:networks/nw:network/nw:node/nt:termination-point/tet:te
      /nw:networks/nw:network/nw:node/tet:te/tet:te-node-attributes
      /te-connectivity-matrices/te-connectivity-matrix/tet:path-
      constraints/tet:te-bandwidth/tet:technology
      /nw:networks/nw:network/nw:node/tet:te
      /tet:tunnel-termination-point/tet:local-link-connectivities
      /tet:label-restrictions/tet:label-restriction

IANA Considerations

IANA is requested to assigned a new URI from the "IETF XML Registry" {{!RFC3688}} as follows:

         URI: urn:ietf:params:xml:ns:yang:ietf-flexi-grid-topology
         Registrant Contact: The IESG
         XML: N/A; the requested URI is an XML namespace.

IANA is requested to assign a new YANG module name in the "YANG Module Names" registry {{!RFC6020}} as follows:

         Name: ietf-flexi-grid-topology
         Namespace: urn:ietf:params:xml:ns:yang:ietf-flexi-grid-topology
         Prefix: flexgt
         Reference: RFC XXXX

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Acknowledgments

{:numbered="false"}

The work presented in this document has been partially funded by the European Commission under the project H2020 METRO-HAUL (Metro High bandwidth, 5G Application-aware optical network, with edge storage, compUte and low Latency), Grant Agreement number: 761727.

This work is also partially funded by the Spanish State Research Agency under the project AgileMon (AEI PID2019-104451RB-C21) and by the Spanish Ministry of Science, Innovation and Universities under the program for the training of university lecturers (Grant number: FPU19/05678).

Thanks to Adrian Farrel for reviewing this document and assisting with conversion to XML.