Internet-Draft | Network Slice Topology Data Model | January 2024 |
Liu, et al. | Expires 28 July 2024 | [Page] |
An IETF network slice may use a customized topology to describe intended resource reservation for connectivities between slice endpoints. Customized topologies enable customers to request shared resources among connections activated on demand and to customize the service paths in a network slice with an extensive level of control.¶
This document describes a YANG data model for managing and controlling customized topologies for IETF network slices defined in RFC YYYY.¶
[RFC EDITOR NOTE: Please replace RFC YYYY with the RFC number of draft-ietf-teas-ietf-network-slices once it has been published.¶
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[I-D.ietf-teas-ietf-network-slices] describes that an IETF network slice service customer might ask for some level of control, e.g., to customize the service paths while requesting network slice services. These customized controls may well be expressed by customer-defined topologies, i.e. customized topologies.¶
Furthermore, by using customized topologies, customers can request advanced resource reservation for all potential network slices that can be activated on demand in the future. This capability provides customers with full control over when and how resources are allocated by the slices. The resources can be shared by network slices created at different times as well as by connections between different edge pairs within the same network slice. This could significantly reduce the overall bandwidth requirements of a network slice and provide economic advantages to the customer.¶
For example, in a hub-and-spoke network slice scenario, multiple customer's spoke sites are expected to be dynamically connected to the hub site and the bandwidth is shared between the spoke sites. To create a customized topology with two virtual nodes, one representing all the spoke sites and the other representing the hub site, connected by a shared link between the two, can ensure that resources for the shared connection are reserved in advance and hence are readily available whenever needed by the customer. On the other hand, to achieve the same level of bandwidth assurance with connections, it would be necessary to create separate, dedicated connections between every spoke and the hub. However, this would result in significant waste of bandwidth.¶
This document defines a YANG [RFC7950] data model for representing, managing, and controlling IETF network slices over customized network topologies, where the network slices are defined in [I-D.ietf-teas-ietf-network-slices]. The YANG model augments the data model defined in [RFC8345] to enable a customer to express desired service-level objectives (SLOs) and service-level expectations (SLEs) over various constructs within the customized topology.¶
The defined data model is an interface between customers and providers for configurations and state retrievals, so as to support network slicing as a service. Through this model, a customer can request or negotiate with a network slicing provider to create an instance. The customer can incrementally update its requirements on individual topology elements in the slice instance, e.g., adding or removing a node or link, updating desired bandwidth of a link, and retrieve the operational states of these elements. With the help of other mechanisms and data models defined in IETF, the telemetry information can be published to the customer, too.¶
The YANG model defines constructs that are technology-agnostic to network slicing built on network layers with different technologies such as IP/MPLS, MPLS-TP, OTN and WDM optical. Therefore, this model can serve as a common and base model on which technology-specific models for network slicing, such as [I-D.ietf-ccamp-yang-otn-slicing], may be built.¶
As described in Section 3 of [I-D.contreras-teas-slice-controller-models], using customized topologies and control of resource reservation is optional for network slicing and complements the data model defined in [I-D.ietf-teas-ietf-network-slice-nbi-yang].¶
The YANG data model in this document conforms to the Network Management Datastore Architecture (NMDA) [RFC8342].¶
The following terminologies for describing network slices are defined in [I-D.ietf-teas-ietf-network-slices] and are not redefined herein.¶
Network Slice (NS)¶
Network Slice Customer¶
Network Slice Service Provider¶
Network Slice Controller (NSC)¶
Network Resource Partition (NRP)¶
The following terms are defined and used in this document.¶
Customized Topology: A topology defined by the customer and served as an input to the network slice service provider, i.e. to the Network Slice Controller (NSC).¶
Abstract Topology: A topology exposed to the customer by the network slice service provider prior to the creation of network slices. The provider uses an abstract topology to expose useful information, such as available resources to the customer, which can facilitate the build-up of customized topologies by the customer.¶
NRP Topology: A topology internal to the NSC to facilitate the mapping of network slices to underlying network resources.¶
Tree diagrams used in this document follow the notation defined in [RFC8340].¶
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 Table 1.¶
Prefix | YANG Module | Reference |
---|---|---|
yang | ietf-yang-types | [RFC6991] |
inet | ietf-inet-types | [RFC6991] |
nt | ietf-network-topology | [RFC8345] |
nw | ietf-network-topology | [RFC8345] |
tet | ietf-te-topology | [RFC8795] |
ns-topo | ietf-ns-topo | [RFCXXXX] |
te-types | ietf-te-types | [RFCYYYY] |
ietf-nss | ietf-network-slice-service | [RFCZZZZ] |
RFC Editor Note: Please replace XXXX with the RFC number assigned to this document. Please replace YYYY with the RFC number assigned to [I-D.ietf-teas-rfc8776-update]. Please replace ZZZZ with the RFC number assigned to [I-D.ietf-teas-ietf-network-slice-nbi-yang]. Please remove this note.¶
An IETF network slice topology is a customized topology
modeled as network topology defined in [RFC8345], with augmentations.
A new network type "network-slice" is defined in this document.
When a network topology data instance contains the network-slice
network type, it represents an instance of an IETF network slice
topology.¶
There are many technologies to achieve network slicing. The data model defined in this document can be used to configure resource-based network slices, where the resources for network slices are reserved and represented in the form of a customized topology, which can then be mapped to a network resource partition (NRP) according to the scenarios defined in [I-D.ietf-teas-ietf-network-slices].¶
Network slices may be abstracted differently depending on the requirement of the network slice customer. A customer may request a network slice with direct connectivity between pairs of service demarcation points (SDPs). Each connection within the network slice may be further supported by an end-to-end tunnel that traverse a specific path in a given customized topology supplied by the customer. The resources associated with a link are immediately commissioned by the realization at the time of network slice configuration.¶
Alternatively, a customer can request resources to be reserved for potential network slices through a customized topology, and use the resources to build network slices in the future. The customized topology represents resources that are reserved but not commissioned at the time of request. By doing so, customers can share resources between multiple endpoints and use them on demand.¶
In the example shown in Figure 2, two customized topology intents named as
Network Slice Blue and Network Slice Red, are created
by separate customers and delivered to the network slice service provider.
The provider maps the two intents to corresponding network resource partitions (NRPs)
internally. In realizing the network resource partitions, node virtualization
is used to separate and allocate resources in physical devices. Two virtual
routers VR1 and VR2 are created over physical router R1, and two virtual
routers VR3 and VR4 are created over physical router R2, respectively. Each of the
virtual routers,as a partition of the physical router, takes a portion
of the resources such as ports and memory in the physical router.
Depending on the requirements and the implementations, they may share
certain resources such as processors, ASICs, and switch fabric.¶
A network slice customer can configure customized topologies without any prior knowledge of the provider's network and resource availability. However, this could potentially make it difficult for the provider to understand and realize the topology. Alternatively, the provider may choose to describe the available resources and capabilities as an abstract topology and expose it to the customer prior to network slice requests. This can facilitate the customer with building customized topologies and avoid unnecessary negotiations between the customer and provider.¶
The process and the data models for the provider to expose abstract topologies are outside the scope of this document.¶
The provider reports the operational state of the topology, which represents the allocated resources agreed upon through negotiations between the customer and the provider. Customers can subquently process the requested topology and integrate it into their own topology. It's important to note that this relationship between the customer and provider can be recursive. For example, a customer for network slices can be a provider of its own to offer network slice services using customized topologies to its own customers further up the hierarchy.¶
As an example, Appendix B. shows the JSON encoded data instances of the customer topology intent for Network Slice Blue.¶
The following constructs and attributes are defined within the YANG model:¶
Network topology, which represent set of shared, reserved resources organized as a virtual topology between all of the endpoints. A customer could use such network topology to define detailed connectivity path traversing the topology, and allow sharing of resources between its multiple endpoint pairs.¶
Service-level objectives (SLOs) associated with different objects, including node, link, termination point of the topology.¶
To ensure the security and controllability of physical resource isolation, slice-based independent operation and management are required to achieve management isolation. Each network slice typically requires dedicated accounts, permissions, and resources for independent access and O&M. This mechanism is to guarantee the information isolation among slice tenants and to avoid resource conflicts. The access to slice management functions will only be permitted after successful security checks.¶
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 TLS [RFC8446].¶
The NETCONF access control model [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.¶
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. Considerations in Section 8 of [RFC8795] are also applicable to their subtrees in the module defined in this document.¶
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. Considerations in Section 8 of [RFC8795] are also applicable to their subtrees in the module defined in this document.¶
It is proposed to IANA to assign new URIs from the "IETF XML Registry" [RFC3688] as follows:¶
URI: urn:ietf:params:xml:ns:yang:ietf-ns-topo Registrant Contact: The IESG XML: N/A; the requested URI is an XML namespace.¶
This document registers a YANG module in the YANG Module Names registry [RFC6020].¶
name: ietf-ns-topo namespace: urn:ietf:params:xml:ns:yang:ietf-ns-topo prefix: ns-topo reference: RFC XXXX¶
The authors would like to thank Danielle Ceccarelli, Bo Wu, Mohamed Boucadair, and Vishnu Beeram for providing valuable insights.¶
This section contains an example of an instance data tree in the JSON encoding [RFC7951]. The example instantiates "ietf-network" for the topology of Network Slice Blue depicted in Figure 2.¶
=============== NOTE: '\' line wrapping per RFC 8792 ================ { "ietf-network:networks": { "network": [ { "network-id": "example-customized-blue-topology", "network-types": { "ietf-ns-topo:network-slice": { } }, "node": [ { "node-id": "VR1", "ietf-ns-topo:service-slo-sle-policy": { "sle-policy": { "isolation": [ { "ietf-network-slice-service:service-traffic-iso\ lation" } ] } }, "ietf-network-topology:termination-point": [ { "tp-id": "1-0-1" }, { "tp-id": "1-3-1" } ] }, { "node-id": "VR3", "ietf-ns-topo:service-slo-sle-policy": { "sle-policy": { "isolation": [ { "ietf-network-slice-service:service-traffic-iso\ lation" } ] } }, "ietf-network-topology:termination-point": [ { "tp-id": "3-1-1" }, { "tp-id": "3-5-1" } ] }, { "node-id": "VR5", "ietf-ns-topo:service-slo-sle-policy": { "sle-policy": { "isolation": [ { "ietf-network-slice-service:service-traffic-iso\ lation" } ] } }, "ietf-network-topology:termination-point": [ { "tp-id": "5-3-1" }, { "tp-id": "5-0-1" } ] } ], "ietf-network-topology:link": [ { "link-id": "VR1,1-0-1,,", "source": { "source-node": "VR1", "source-tp": "1-0-1" }, "ietf-ns-topo:service-slo-sle-policy": { "slo-policy": { "metric-bounds": { "metric-bound": [ { "metric-type": "ietf-network-slice-service:se\ rvice-slo-two-way-delay", "metric-unit": "ms", "bound": 60 } ] } }, "sle-policy": { "isolation": [ { "ietf-network-slice-service:service-traffic-iso\ lation" } ] } } }, { "link-id": ",,VR1,1-0-1", "destination": { "dest-node": "VR1", "dest-tp": "1-0-1" }, "ietf-ns-topo:service-slo-sle-policy": { "slo-policy": { "metric-bounds": { "metric-bound": [ { "metric-type": "ietf-network-slice-service:se\ rvice-slo-two-way-delay", "metric-unit": "ms", "bound": 30 } ] } }, "sle-policy": { "isolation": [ { "ietf-network-slice-service:service-traffic-iso\ lation" } ] } } }, { "link-id": "VR1,1-3-1,VR3,3-1-1", "source": { "source-node": "VR1", "source-tp": "1-3-1" }, "destination": { "dest-node": "VR3", "dest-tp": "3-1-1" }, "ietf-ns-topo:service-slo-sle-policy": { "slo-policy": { "metric-bounds": { "metric-bound": [ { "metric-type": "ietf-network-slice-service:se\ rvice-slo-two-way-delay", "metric-unit": "ms", "bound": 30 } ] } }, "sle-policy": { "isolation": [ { "ietf-network-slice-service:service-traffic-iso\ lation" } ] } } }, { "link-id": "VR3,3-1-1,VR1,1-3-1", "source": { "source-node": "VR3", "source-tp": "3-1-1" }, "destination": { "dest-node": "R1", "dest-tp": "1-3-1" }, "ietf-ns-topo:service-slo-sle-policy": { "slo-policy": { "metric-bounds": { "metric-bound": [ { "metric-type": "ietf-network-slice-service:se\ rvice-slo-two-way-delay", "metric-unit": "ms", "bound": 30 } ] } }, "sle-policy": { "isolation": [ { "ietf-network-slice-service:service-traffic-iso\ lation" } ] } } }, { "link-id": "VR3,3-5-1,VR5,5-3-1", "source": { "source-node": "VR3", "source-tp": "3-5-1" }, "destination": { "dest-node": "VR5", "dest-tp": "5-3-1" }, "ietf-ns-topo:service-slo-sle-policy": { "slo-policy": { "metric-bounds": { "metric-bound": [ { "metric-type": "ietf-network-slice-service:se\ rvice-slo-two-way-delay", "metric-unit": "ms", "bound": 35 } ] } }, "sle-policy": { "isolation": [ { "ietf-network-slice-service:service-traffic-iso\ lation" } ] } } }, { "link-id": "VR5,5-3-1,VR3,3-5-1", "source": { "source-node": "VR5", "source-tp": "5-3-1" }, "destination": { "dest-node": "VR3", "dest-tp": "3-5-1" }, "ietf-ns-topo:service-slo-sle-policy": { "slo-policy": { "metric-bounds": { "metric-bound": [ { "metric-type": "ietf-network-slice-service:se\ rvice-slo-two-way-delay", "metric-unit": "ms", "bound": 35 } ] } }, "sle-policy": { "isolation": [ { "ietf-network-slice-service:service-traffic-iso\ lation" } ] } } }, { "link-id": "VR5,5-0-1,,", "source": { "source-node": "VR5", "source-tp": "5-0-1" }, "ietf-ns-topo:service-slo-sle-policy": { "slo-policy": { "metric-bounds": { "metric-bound": [ { "metric-type": "ietf-network-slice-service:se\ rvice-slo-two-way-delay", "metric-unit": "ms", "bound": 25 } ] } }, "sle-policy": { "isolation": [ { "ietf-network-slice-service:service-traffic-iso\ lation" } ] } } }, { "link-id": ",,VR5,5-0-1", "destination": { "dest-node": "VR5", "dest-tp": "5-0-1" }, "ietf-ns-topo:service-slo-sle-policy": { "slo-policy": { "metric-bounds": { "metric-bound": [ { "metric-type": "ietf-network-slice-service:se\ rvice-slo-two-way-delay", "metric-unit": "ms", "bound": 25 } ] } }, "sle-policy": { "isolation": [ { "ietf-network-slice-service:service-traffic-iso\ lation" } ] } } } ], "ietf-ns-topo:service-slo-sle-policy": { "sle-policy": { "isolation": [ { "ietf-network-slice-service:service-traffic-isolati\ on" } ] } } } ] } }¶