Internet-Draft | NRPs YANG | March 2024 |
Wu, et al. | Expires 17 September 2024 | [Page] |
RFC 9543 describes a framework for Network Slice in a network built from IETF technologies. In this framework, the network resource partition (NRP) is introduced as a collection of network resources allocated from the underlay network to carry a specific set of network slice service traffic and meet specific Service Level Objective (SLO) and Service Level Expectation (SLE) characteristics.¶
This document defines YANG data models for Network Resource Partitions (NRPs), applicable to devices and network controllers. The models can be used, in particular, for the realization of the RFC9543 Network Slice Services in IP/MPLS and Segment Routing (SR) networks.¶
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[RFC9543] describes a framework for Network Slice in a network built from IETF technologies. As specified in Section 7.4 [RFC9543], an NRP is a collection of resources identified in the underlay network to support the RFC9543 Network Slice Service to meet the slice Service Level Objectives (SLOs) and Service Level Expectations (SLEs) characteristics and network scalability.¶
This document defines two YANG models: NRPs network model in Section 4 and NRPs device model in Section 5. An Network Slice Controller (NSC) defined in Section 6.3 [RFC9543] can use the NRP network model to manage NRP instances for Network Slice Services. According to the YANG model classification of [RFC8309], the NRPs network model is a network configuration model.The NRPs device model can be used for device configuration, including device-specific configuration (e.g. interfaces).¶
The NRPs models conforms to the Network Management Datastore Architecture (NMDA) [RFC8342].¶
An NRP Policy [I-D.ietf-teas-ns-ip-mpls] is a policy construct that enables instantiation of mechanisms in support of service specific control and data plane behaviors on select topological elements associated with the NRP.Section 3.1 describes the detailed definition of NRP policy in NRP instantiation.¶
The following terms are defined in [RFC6241] and are used in this specification:¶
The following terms are defined in [RFC7950] and are used in this specification:¶
The terminology for describing YANG data models is found in [RFC7950].¶
The tree diagram used in this document follows the notation defined in [RFC8340].¶
The general operations of NRPs are as follows:¶
NRPs instantiation: Depending on the slice service types and also network status, there can be two types of approaches. One method is to create an NRP instance before the network controller processes the Network Slice service request. Another one is that the network controller may start creating an NRP instance while configuring the Network Slice service request.¶
NRPs modification: When the capacity of an existing NPR link is close to capacity, the bandwidth of the link could be increased. And when an NRP links or nodes resources are insufficient, new NRP links and nodes could be added.¶
NRPs Deletion: If the NSC determines that no slice service is using an NRP, the NSC can delete the NRP instance.¶
NRPs Monitoring: The NSC can use the NRPs model to track and monitor NRPs resource status and usage.¶
Section 3.5 in [I-D.ietf-teas-ns-ip-mpls] introduces the NRP policy. An NRP policy specifies the rules for determining the topology associated with the NRP and dictates how an NRP can be realized in IP/MPLS/SR networks. Section 4 of [I-D.ietf-teas-ns-ip-mpls] also defines three partition modes: (a) just the data plane or in (b) just the control plane or in (c) both the control and data planes. The NRP policy can dictate if the partitioning of the shared network resources can be achievedthrough one of the modes.¶
The NRP policy modes (a) and (c) require the forwarding engine on each NRP capable node to identify the traffic belonging to a specific NRP and to apply the corresponding Per-Hop Behavior (PHB) or forwarding mechanism that determines the forwarding treatment of the packets belonging to the NRP. When catering to Network Slices, this NRP identification is referred to as the NRP selector and may comprises of traffic streams from one or more connectivity constructs (belonging to one or more Network Slices) mapped to a specific NRP. The NRP policy modes (b) and (c) require the distributed/centralized resource reservation management.¶
'nrp-policy' is defined to enable NRP Stateful Traffic Engineering (NRP-TE) [I-D.ietf-teas-ns-ip-mpls] and/or NRP IGP forwarding in IP/MPLS networks [I-D.ietf-teas-nrp-scalability].¶
The high-level model structure of NRP policy defined by this document is as shown in Figure 1:¶
The 'networks' container from the 'ietf-network' module [RFC8345] provides a placeholder for an inventory of nodes in the network. This container is augmented to carry a set of NRP policies.¶
The 'nrp-policies' container carries a list of NRP policies. Each 'nrp-policy' entry is identified by a name and holds the set of attributes needed to instantiate an NRP. Each entry also carries an 'nrp-id' leaf which uniquely identifies the NRP created by the enforcement of this policy.¶
The description of the 'nrp-policies' data nodes are as follows, and the other key elements of each nrp-policy entry are discussed in the following sub-sections.¶
'nrp-id': Is an identifier that is used to uniquely identify an NRP instance within an NSC network scope.¶
'mode': Refers to control plane resource partition, data plane resource partition, or a combination of both types.¶
The 'resource-reservation' container specifies the bandwidth resource allocated to an NRP instance, or can be overridden by the configuration of the link specific 'resource-reservation' nodes of 'nrp-topology'.¶
NRP selector defines the data plane encapsulation types and values that are used to identify NRP-specific network resources.¶
[I-D.ietf-teas-nrp-scalability] discusses several candidate NRP selector encapsulation schemes, including IP, MPLS, or SRv6, for example, the IPv6 Hop-by-Hop extension header defined in [I-D.ietf-6man-enhanced-vpn-vtn-id], or the SRv6 SID defined in [I-D.ietf-spring-sr-for-enhanced-vpn]. Since the MPLS encapsulation schemes are still under discussion, the model only provides a place holder for future updates. Additionally, the use of NRP-specific IP addresses to identify NRP resources, or the use of specific ACLs, are optional NRP selector mechanisms.¶
PHB and NRP selector are combined mechanisms. PHB is used to specify the forwarding treatment of packets belonging to a specific NRP selector, such as bandwidth control, congestion control (e.g., Section 3.4 [RFC3644]). The exact definition of PHB is locally defined by the device or controller managing the NRPs. The 'phb-profile' leaf carries a name of a PHB profile available on the topological element where the policy is being enforced. Some examples of "phb-probile" may be standard PHBs, such as "Assured Forwarding (AF)", "Expedited Forwarding (EF)", or a customized local policies, such as "High", "Low", "Standard".¶
'nrp-topology' defines a dedicated NRP topology.¶
When an NRP support IGP forwarding, the topology of the NRP must be congruent with an IGP instance.The topology used for IGP route computation and forwarding can be derived using Multi-Topology Routing (MTR) or Flex-algo. Multi-Topology Routing (MTR) is defined in [RFC4915], [RFC5120], and [I-D.ietf-lsr-isis-sr-vtn-mt] or Flex-algo is defined in [RFC9350].¶
Figure 5 shows an example of NRP-1 enabling "igp-congruent", which indicates that this NRP instance uses the same IGP topology with the specified 'multi-topology-id' or 'algo-id'. As illustrated, NRP-1 has different link resource attributes from those of the IGP, but shares the same the nodes and termination point (TPs) of the IGP topology.¶
The 'selection' container consists of a list of select subset of links of an underlay topology or a pre-built topology.¶
The 'filter' container consists of a list of filters where each entry references a topology filter [I-D.bestbar-teas-yang-topology-filter]. The topological elements that satisfy the membership criteria can optionally override the default resource-reservation and nrp-selector specific leafs.¶
The NRPs model can be used to track and monitor operational status and resource usage of NRPs.¶
The device-specific NRPs model is defined in module 'ietf-nrp-device' as shown in Section 5, which augments NRPs YANG data model in Section 4 and adds interface attributes, including resource reservation, NRP selector, and PHB profile, that are specific to an NRP device.¶
Figure below shows the tree diagram of the device NRPs YANG model defined in modules 'ietf-nrp-device.yang'.¶
The 'ietf-nrp' module uses types defined in [RFC8345], [RFC8294],[RFC8776], [RFC6991], [RFC8519], [I-D.ietf-spring-srv6-yang], and [I-D.bestbar-teas-yang-topology-filter].¶
The device NRPs YANG module ('ietf-nrp-device') models augments the NRPs YANG module ('ietf-nrp') and adds the attributes of NRP interfaces that are local to an NRP device.¶
The device NRPs YANG module imports the following module(s): ietf-interfaces defined in [RFC8343], ietf-network defined in [RFC8345], and grouping defined in this document.¶
[I-D.ietf-teas-nrp-scalability] analyzes the scalability considerations of the control plane and data plane in the NRPs deployment. This section complements some scalability considerations with the model and the possible implications on deployment or implementation.¶
Note: The possible managment impact of a large number of NRPs instance management on devices and controllers on a large-scale network scenarios will be added later.¶
The YANG model defined in this document 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 model 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.¶
nrp-link: A malicious client could attempt to remove a link from a topology, add a new link. In each case, the structure of the topology would be sabotaged, and this scenario could, for example, result in an NRP topology that is less than optimal.¶
The entries in the nodes above include the whole network configurations corresponding with the NRP, and indirectly create or modify the PE or P device configurations. Unexpected changes to these entries could lead to service disruption and/or network misbehavior.¶
This document registers a URI in the IETF XML registry [RFC3688]. Following the format in [RFC3688], the following registration is requested to be made:¶
URI: urn:ietf:params:xml:ns:yang:ietf-nrp Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace. URI: urn:ietf:params:xml:ns:yang:ietf-nrp-device Registrant Contact: The IESG. XML: N/A, the requested URI is an XML namespace.¶
This document requests to register a YANG module in the YANG Module Names registry [RFC7950].¶
Name: ietf-nrp Namespace: urn:ietf:params:xml:ns:yang:ietf-nrp Maintained by IANA: N Prefix: nrp Reference: RFC XXXX Name: ietf-nrp-device Namespace: urn:ietf:params:xml:ns:yang:ietf-nrp-device Maintained by IANA: N Prefix: nrp-dev Reference: RFC XXXX¶
The authors would like to thank Krzysztof Szarkowicz, Jie Dong, Qin Wu, Yao Zhao, Zhenbing Li, Adrian Farrel, Tom Petch, Xuesong Geng, Italo Busi,and many others for their helpful comments and suggestions.¶
The following individuals, authors of [I-D.bestbar-teas-yang-nrp-policy] and [I-D.wd-teas-nrp-yang], contributed to this consolidated document:¶
Xufeng Liu IBM Corporation Email: xufeng.liu.ietf@gmail.com Mohamed Boucadair Orange Email: mohamed.boucadair@orange.com Daniele Ceccarelli Bin Wen Comcast Email: Bin_Wen@cable.comcast.com Ran Chen ZTE Corporation Email: chen.ran@zte.com.cn Luis M. Contreras Telefonica Email: luismiguel.contrerasmurillo@telefonica.com Ying Cheng China Unicom Email: chengying10@chinaunicom.cn Liyan Gong China Mobile Email: gongliyan@chinamobile.com¶
This section lists the non-blocking issues raised during the Working Group adoption process. The issues listed below need to be fully resolved before publication¶
Raised by Tom Petch: Abstract lacks the reference to the NS framework that defines the NRP.¶
Raised by Adrain Farrel: 1) Avoid limiting IP/MPLS technology to realize NRPs, SR should be in scope; 2) Avoid the "IETF Network Slice" language, should use terms as "RFC 9543 Network Slice" and "RFC 9543 Network Slice Service" 3) It's good to investigate any scaling issues with the model and any implications on deployments or implementations, just as draft-ietf-teas-nrp-scalability.¶
Raised by Med Boucadair: 1) Normative dependency on individual drafts, such as I-D.bestbar-teas-yang-topology-filter, suggesting to add it back when stable 2) The device model in the spec is not a device model as it augments a network model. 3) Some of the review provided in https://github.com/boucadair/IETF-Drafts-Reviews/blob/master/2024/draft-ahuang-netconf-udp-client-server-01-rev%20Med.pdf¶
Raised by Lius Contreras: 1) Clarify the NRP model usage in NSC, network controllers, and devices; 2) Rename Section 3.1.1 title to bandwidth reservation; 3) Add the references of "NRP capable node"; 4) In Section 3.1.3, better to clarify single PHB or multiple PHB per NRP and Whether the PHB management scope is in the NSC or network controller; 5) Section 3.1 adds description of NRP policy modes (b) and (c).¶
Raised by Xuesong: 1) Clarify the considerations for defining the NRP policy; 2) Distinguish NRP model operation and NRP mode (CP,DP, and hybrid); 3) Clarify the relationship and design consideration of NRPs network and device models.¶
Raised by Italo: 1) Clarify the models are technology-agnostic NRPs model or IP technology-specific NRPs model; 2) Updates the abstract/introduction to clarify that this model applies on devices and on controllers.¶
This section contains an example of an instance data tree in JSON encoding [RFC7951]. The example below instantiates an NRP for the topology that is depicted in the following diagram. There are three nodes, D1, D2, and D3. D1 has three termination points, 1-0-1, 1-2-1, and 1-3-1. D2 has three termination points as well, 2-1-1, 2-0-1, and 2-3-1. D3 has two termination points, 3-1-1 and 3-2-1. In addition there are six links, two between each pair of nodes with one going in each direction.¶
An corresponding IGP congruent NRP instance data tree is depicted below:¶
In addition, an exampe of an NRP that supports the control plane partition mode is shown in the following figure.¶
{ "ietf-network:networks": { "nrp-policies": { "nrp-policy": [ { "name": "NRP2", "nrp-id": "foo:nrp-example2", "mode": "nrp-control-plane-partition", "resource-reservation": { "bw-value": "10000" }, "phb-profile:": "EF", "topology": { "filters": { "filter": [ { "filter-ref": "te-topology-filter1" } ] } } } ] } } }¶
Figure 13 shows the full tree diagram of the NRPs YANG model defined in module 'ietf-nrp.yang'.¶
Figure 14 shows the full tree diagram of the NRPs device YANG model defined in module 'ietf-nrp-device.yang'.¶