Network Working Group S. Barguil Internet-Draft L.M. Contreras Intended status: Informational Telefonica Expires: 12 January 2023 V. Lopez Nokia R. Rokui Ciena O. Gonzalez de Dios Telefonica 11 July 2022 Instantiation of IETF Network Slices in Service Providers Networks draft-barguil-teas-network-slices-instantation-04 Abstract Network Slicing (NS) is an integral part of Service Provider networks. The IETF has produced several YANG data models to support the Software-Defined Networking and network slice architecture and YANG-based service models for network slice (NS) instantiation. This document describes the relationship between IETF Network Slice models for requesting the IETF Network Slices and (e.g., Layer-3 Service Model, Layer-2 Service Model) and Network Models (e.g., Layer-3 Network Model, Layer-2 Network Model) used during their realizations. In addition, this document describes the communication between the IETF Network Slice Controller and the network controllers for the realization of IETF network slices. The IETF Network Slice YANG model provides the customer-oriented view of the network slice. Thus, once the IETF Network Slice controller (NSC) receives a request, it needs to map it to accomplish the specific parameters expected by the network controllers. The network models are analyzed to satisfy the IETF Network Slice requirements, and the gaps in existing models are reported. The document also provides operational and security considerations when deploying network slices in Service Provider networks. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Barguil, et al. Expires 12 January 2023 [Page 1] Internet-Draft Network models for IETF Network Slices July 2022 Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 12 January 2023. Copyright Notice Copyright (c) 2022 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 2. Reference Architecture and Components . . . . . . . . . . . . 4 2.1. Possible architectural options for IETF Network Slice Controller . . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Possible relationship of IETF Network Slice service model with other models . . . . . . . . . . . . . . . . . . . . 7 3. IETF Network Slice Requirements and Data Models . . . . . . . 8 4. IETF Network Slice Procedure . . . . . . . . . . . . . . . . 9 5. Network Controller Operation . . . . . . . . . . . . . . . . 10 5.1. LxVPN Service Models . . . . . . . . . . . . . . . . . . 10 5.2. LxVPN Network Models . . . . . . . . . . . . . . . . . . 11 5.3. Traffic Engineering Models . . . . . . . . . . . . . . . 11 5.4. Traffic Engineering Service Mapping . . . . . . . . . . . 11 6. Operational Considerations . . . . . . . . . . . . . . . . . 11 6.1. Availability . . . . . . . . . . . . . . . . . . . . . . 12 6.2. Downlink throughput / Uplink throughput. . . . . . . . . 12 6.3. Protection scheme . . . . . . . . . . . . . . . . . . . . 12 6.4. Delay . . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.5. Packet loss rate . . . . . . . . . . . . . . . . . . . . 13 Barguil, et al. Expires 12 January 2023 [Page 2] Internet-Draft Network models for IETF Network Slices July 2022 7. Relationship between IETF NBI model parameters and L3SM and L2SM model parameters . . . . . . . . . . . . . . . . . . 13 8. Network Slice Procedure . . . . . . . . . . . . . . . . . . . 17 8.1. IETF Network Slice requested to Hierarchical Network Controller . . . . . . . . . . . . . . . . . . . . . . . 18 8.2. IETF Network Slice requested to Network Slice Controller . . . . . . . . . . . . . . . . . . . . . . . 19 8.3. Network Slice Controller as part of the domain controller . . . . . . . . . . . . . . . . . . . . . . . 20 9. Security Considerations . . . . . . . . . . . . . . . . . . . 22 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 11. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 23 12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 23 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 23 14. Normative References . . . . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26 1. Introduction The IETF has produced several YANG data models to support the Software-Defined Networking and network slice architecture. The IETF Network Slice YANG service model provides the customer- oriented view of the network slice. Once the IETF Network Slice controller (NSC)receives a request, it needs to map it to accomplish the specific parameters expected by the network controller. Several Service Models and Network Models, including Layer-3 Service Model (L3SM), Layer-2 Service Model (L2SM) and Network Models which may be utilized for IETF Network Slicing, are analyzed can satisfy the IETF Network Slice requirements. In addition, identified gaps on existing models are reported. This document describes the architecture and communication process between the Network Slice Controller and a network controller for IETF network slice creation. Editor's Note: the terminology in this draft will be aligned with the final terminology selected for describing the notion of IETF Network Slice when applied to IETF technologies, as being defined in [I-D.ietf-teas-ietf-network-slices]. 1.1. Terminology The keywords MUST, MUST NOT, REQUIRED, SHALL, SHALL NOT, SHOULD, SHOULD NOT, RECOMMENDED, MAY, and OPTIONAL, when they appear in this document, are to be interpreted as described in [RFC2119]. Barguil, et al. Expires 12 January 2023 [Page 3] Internet-Draft Network models for IETF Network Slices July 2022 2. Reference Architecture and Components As described in [I-D.ietf-teas-ietf-network-slices], the IETF Network Slice Controller (NSC) is a functional entity for control and management of IETF network slices. As shown in Figure A, NSC from its Northbound Interface (NBI exposes set of APIs that allow a higher level system to request an IETF network slice. The NSC NBI supports the request for enabling of an IETF Network Slice (i.e., creation, modification or deletion). Upon receiving a request from its NBI, NSC finds the resources needed for realization of the IETF Network Slice and in turn interfaces from its Southbound Interface (SBI) with one or more Network Controllers for the realization of the requested IETF Network Slice. This document focuses on how IETF Network Slice Controller (NSC) can be implemented in the operator's network. +------------------------------------------+ | A higher level system | | (e.g E2E network slice orchestrator) | +------------------------------------------+ A | NSC NBI V +------------------------------------------+ | IETF Network Slice Controller (NSC) | +------------------------------------------+ A | NSC SBI V +------------------------------------------+ | Network Controller(s) | +------------------------------------------+ Figure 1 Network Slice Controller as a module of the Hierarchical SDN controller. 2.1. Possible architectural options for IETF Network Slice Controller Several architectural definitions have arisen on the IETF to support SDN and network slicing deployments. The architectural proposal defined in [I-D.ietf-teas-ietf-network-slices] includes a three-level hierarchy and expresses how each level relates with the ACTN architecture framework. Figure 2 defines depicts a possible architecture using those concepts. It starts from a top consumer or high-level operational systems. Next, the IETF Network Slice Controller function might be Barguil, et al. Expires 12 January 2023 [Page 4] Internet-Draft Network models for IETF Network Slices July 2022 part of the Hierarchical network controller (e.g., as the MDSC in the ACTN context [RFC8453]) as a modular function. At the bottom, two network controllers, each one can handle multiple or single underlay technologies. +------------------------------+ | High-level operation system. | +--------------+---------------+ |IETF Network Slice Request | +-------------------v------------------+ | | | Hierarchical Network | | Controller/Orchestrator | | | | +-------------------------------+ | | | IETF Network Slice Controller | | | +-------------------------------+ | | | +-------------------+------------------+ | | +--------------+---------------+ | | v v +-------------+----------+ +-------------+----------+ | Network Controller | | Network Controller | +-------------+----------+ +-------------+----------+ | | | | v v Network Elements Network Elements Figure 2 IETF Network Slice Controller as a module of the Hierarchical SDN controller. In other implementations, the IETF Network Slice Controller can be a stand-alone element and directly interact with the network controller, as depicted in Figure 2. In this scenario, the services request follows a data-enrichment path, where each entity adds more information to the service request. This document describes how the available service models and network models interact to deliver the network slices in a service provider environment. Barguil, et al. Expires 12 January 2023 [Page 5] Internet-Draft Network models for IETF Network Slices July 2022 +-------------------------------+ | High-level operation system | +-------------+-----------------+ |IETF Network Slice Request | +-------------v-----------------+ | IETF Network Slice Controller | +-------------+-----------------+ | | +-------------v-----------------+ | Network Controller | +-------------+-----------------+ | | v Network Elements Figure 3 The IETF Network Slice Controller as a stand-alone entity. As another implementation possibility, the IETF Network Slice Controller can be integrated with the Network controller and directly realize the network slice using device data models to configure the network devices. The sample architecture is depicted in Figure 4. +-------------------------------+ | High-level operation system | +-------------+-----------------+ |IETF Network Slice Request | +-------------v----------------+ | Network Controller | | | |+----------------------------+| || Network Slice Controller || |+----------------------------+| | | +-------------+----------------+ | | v Network Elements Figure 4 IETF Network Slice Controller as a module of the Network controller. Barguil, et al. Expires 12 January 2023 [Page 6] Internet-Draft Network models for IETF Network Slices July 2022 2.2. Possible relationship of IETF Network Slice service model with other models IETF Network Slice service is expected to serve as input from where deriving some other models in the network. According to the architectural options before, different relationships could be considered. Figure 5 reflects a couple of options. Operations Support and Business Support YANG Modules +-----------------------+ +-----------------------+ | | | | | Customer Service | | Other | | YANG Modules | | Operations Support | | | | and | | +-----------------+ | | Business Support | | | IETF Network | | | YANG Modules | | | Slice service | | | | | | model | | | | | +------------+----+ | | | | | | | | | | | +------------+ | | | __________V_________ | | | | |/ +------+ +------+\ | | | | | | | | | | | | | | | L2SM | | L3SM | | | | | | | | | | | | | | | +------+ +------+ | | | | |\____________________/ | | | | +-----------|-----------+ | +-----------------------+ | | - - - - - - | - - - - - - - -| - - - - - - - - - - - - - - - - | | Network Service YANG Modules _____________V________________V__________________________________ / \ / +------------+ +-------------+ +-------------+ +-------------+ \ | | | | | | | | | - L2VPN | | - L2VPN | | EVPN | | L3VPN | | - VPWS | | - VPLS | | | | | | | | | | | | | +------------+ +-------------+ +-------------+ +-------------+ Figure 5 Possible relationships between models. Thus, the IETF Network Slice model (e.g., as defined in [I-D.ietf-teas-ietf-network-slice-nbi-yang] could feed existing service models, such as L2SM or L3SM, or could feed existing network Barguil, et al. Expires 12 January 2023 [Page 7] Internet-Draft Network models for IETF Network Slices July 2022 models (e.g., EVPN, L3VPN, etc). Existing models both for service or network level could require some extensions themselves, or their application in conjunction with some other complementary models (e.g., TE model) to accomplish the service objectives and expectations as declared in the IETF Network Slice model. 3. IETF Network Slice Requirements and Data Models The main set of requirements for the IETF Slice, based on the high- level slice requirements from multiple organizations and use cases, are compiled in [I-D.contreras-teas-slice-nbi] and reproduced bellow the slice use cases reported: +-----------------------------------------------+ | Network Slice Requirements for 5G service | +-----------------------------------------------+ | Availability | | Deterministic communication | | Downlink throughput per network slice | | Energy efficiency | | Group communication support | | Isolation level | | Maximum supported packet size | | Mission critical support | | Performance monitoring | | Slice quality of service parameters | | Support for non-IP traffic | | Uplink throughput per network slice | | User data access | | Delay tolerance | +-----------------------------------------------+ +-----------------------------------------------+ | NFV-based services | +-----------------------------------------------+ | Incoming and outgoing bandwidth | | Qos metrics | | Directionality | | MTU | | Protection scheme | | Connectivity mode | +-----------------------------------------------+ Barguil, et al. Expires 12 January 2023 [Page 8] Internet-Draft Network models for IETF Network Slices July 2022 +-----------------------------------------------+ | Network sharing | +-----------------------------------------------+ | Maximum and Guaranteed Bit Rate | | Bounded latency | | Packet loss rate | | IP addressing | | L2/L3 reachability | | Recovery time | | Secure connection | +-----------------------------------------------+ To accomplish those requirements, a set of YANG data models have been proposed. Those Yang models could be used by an IETF Network Slice Controller to manage CRUD operations on the IETF Network Slice. That is, these models aim capturing the requirements from the consumer of the slice point of view and avoid entering into the detail of how the slice is actually created. * [I-D.ietf-teas-ietf-network-slice-nbi-yang]: A Yang Data Model for IETF Network Slice NBI. * [I-D.liu-teas-transport-network-slice-yang]: Transport Network Slice YANG Data Model. 4. IETF Network Slice Procedure An IETF Network Slice may use several underlying technologies. The creation of a new IETF Network Slice will be initiated with following three steps: 1. A higher level system requests connections with specific characteristics via the NBI. 2. This request will be processed by an IETF NSC which specifies a mapping between northbound request to any IETF Services, Tunnels, and paths models. 3. A series of requests for creation of services, tunnels and paths will be sent to the network to realize the transport slice. Barguil, et al. Expires 12 January 2023 [Page 9] Internet-Draft Network models for IETF Network Slices July 2022 5. Network Controller Operation As a functional entity responsible for managing a network domain, the network controller, can expose its northbound interface based on YANG models. The IETF Network Slice Controller can use the network controller's NBI during the realization of IETF Network Slice. The following network models can be used for realization of IETF Network slices: * LxVPN Network models: - These models describe a VPN service from the network point of view. It supports the creation of Layer 3 and Layer 2 services using several control planes. * Traffic Engineering models: - These models allow to manipulate Traffic Engineering tunnels within the network segment. Technology-specific extensions allow to work with a desired technology (e.g. MPLS RSVP-TE tunnels, Segment Routing paths, OTN tunnels, etc.) * TE Service Mapping extensions: - These extensions allow to specify for LxVPN the details of an underlay based on TE. * ACLs and routing policies models: - Even though ACLs and routing policies are device models, it's exposure in the NBI of a domain controller allows to provide an additional granularity that the network domain controller is not able to infer on its own. 5.1. LxVPN Service Models The framework defined in [RFC8969] compiles a set of YANG data models for automating network services. The data models can be used during the service and network management life cycle (e.g., service instantiation, service provisioning, service optimization, service monitoring, service diagnosing, and service assurance). The Service models could be a realization of IETF Network slice requests. The following models are examples of Network models that describe services. * [RFC8049]: YANG Data Model for L3VPN Service Delivery Barguil, et al. Expires 12 January 2023 [Page 10] Internet-Draft Network models for IETF Network Slices July 2022 * [RFC8466]: A YANG Data Model for Layer 2 Virtual Private Network (L2VPN) Service Delivery 5.2. LxVPN Network Models Similar to the Service Models, the framework defined in [RFC8969] compiles a set of YANG data models for automating network services. The Network models could be reused for the realization of Network slice requests. The following models are examples of Network models that describe services. * [RFC9182]: A Layer 3 VPN Network YANG Model * [I-D.ietf-opsawg-l2nm]: A Layer 2 VPN Network YANG Model 5.3. Traffic Engineering Models TEAS has defined a collection of models to allow the management of Traffic Engineering tunnels. * [I-D.ietf-teas-yang-te]: A YANG Data Model for Traffic Engineering Tunnels, Label Switched Paths and Interfaces. The model allows to instantiate paths in a TE enabled network. Note that technology augmented models are require to particular per-technology instantiations. 5.4. Traffic Engineering Service Mapping The IETF has defined a YANG model to set up the procedure to map VPN service/network models to the TE models. This model, known as service mapping, allows the network controller to assign/retrieve transport resources allocated to specific services. At the moment there is just one service mapping model [I-D.ietf-teas-te-service-mapping-yang]. The "Traffic Engineering (TE) and Service Mapping Yang Model" augments the VPN service and network models. 6. Operational Considerations This section outlines the compliance and operational aspects of Network Controller models with IETF Network slice requirements. Section presented the requirements of the IETF Network slice. In this subsection it is analyzed how available YANG models that can be used by a Network Controller can satisfy those requirements and identify gaps. Barguil, et al. Expires 12 January 2023 [Page 11] Internet-Draft Network models for IETF Network Slices July 2022 6.1. Availability As per [draft-ietf-teas-te-service-mapping-yang], Availability is a probabilistic measure of the length of time that a VPN/VN instance functions without a network failure. As per RFC 8330, The parameter "availability", as described in [G.827], [F.1703], and [P.530], is often used to describe the link capacity. The availability is a time scale, representing a proportion of the operating time that the requested bandwidth is ensured". The calculation of the availability is not trivial and would need to be clearly scoped to avoid misunderstandings. The set of Yang models proposed today allow to request tunnels/paths with different resiliency requirements in terms of protection and restoration. However, none of them include the possibility of requesting a specific availability (e.g. 99.9999%). 6.2. Downlink throughput / Uplink throughput. The LxVPN Models ([RFC9182] and [I-D.ietf-opsawg-l2nm]) allow to specify the bandwdidth at the interface level between the slice and the customer. In addition, the Service Mapping model [draft-ietf- teas-te-service-mapping-yang] allows to bind a VPN to a given LSP, which have its bandwidth requirements. Additionally, TE models can force a give bandwidth in the connection between Provider Edges. Previous comment applies to the incoming and outgoing bandwidth parameters required for the NFV-based services use case in [I-D.contreras-teas-slice-nbi]. The Network sharing use case has Maximum and Guaranteed Bit Rate parameters. These parameters can be mapped to the TE tunnel models when setting up LSPs [draft-ietf-teas- yang-te]. 6.3. Protection scheme Protection schemes are mechanisms to define how to setup resources for a given connection. TE tunnel models [draft-ietf-teas-yang-te] includes protection and restoration as two main attributes. The parameters included in the containers for protection and restoration cover the requirements of the IETF NS related with protection schemes. Similarly, TE models cover the parameter 'recovery time' for the network sharing use case. Barguil, et al. Expires 12 January 2023 [Page 12] Internet-Draft Network models for IETF Network Slices July 2022 6.4. Delay Delay is a critical parameter for several IETF NS types. Every use- case defined in [I-D.contreras-teas-slice-nbi] contains delay constraints. 5G use cases require 'delay tolerance', NFV-based services have the delay information within 'QoS metrics' and 'Bounded latency' in the network sharing use case. During the realization of the IETF Network Slice, these parameters are part of the requirements of a TE tunnel configuration [draft- ietf-teas-yang-te]. They can be included within the 'path-metric- bounds' parameter, so the created LSP fulfils the given metrics bounds like 'path-metric-delay-average' or 'path-metric-delay- minimum'. 6.5. Packet loss rate The packet loss rate indicates the maximum rate for lost packets that the service tolerates in the link. During the realization of the IETF Network Slice, this attribute will influence the tunnel selection and the value is included in the [draft-ietf-teas-yang-te] document as the 'path-metric-loss". The 'path-metric-loss' is a metric type, which measures the percentage of packet loss of all links traversed by a P2P path. This parameter is required for 5G services and network sharing use-case, while it is part of the 'QoS metrics' for the NFV-based services. 7. Relationship between IETF NBI model parameters and L3SM and L2SM model parameters This section presents an initial analysis of the relationship between IETF NBI model parameters and L3SM and L2SM service model parameters. The L3SM service parameters are defined in section 6.2 of RFC 8299. The following parameters are considered, so far: * Bandwidth. This parameter indicates the bandwidth requirement between each CE and PE participating in the service, then referrign essentially to the required WAN link bandwidth. It is expressed in terms of bits per second and individually specified for both input and output. Despite it is not stated in RFC 8299, this parameter can be interpreted as the CIR/PIR expected for the CE - PE connection. * MTU. This parameter indicates the maximum PDU size expected for the layer-3 service. It is relevant since packets could be discarded in case the customer sends packets with longer MTU than the one expressed by this parameter. Barguil, et al. Expires 12 January 2023 [Page 13] Internet-Draft Network models for IETF Network Slices July 2022 * QoS. Regardign QoS, two different kind of parameters are detailed. - QoS classification policy. This policy is used to classify the traffic received from the customer, and it is expressed as a set of ordered rules. It is used for marking the input traffic (from CE to PE) when the customer flows match any of the rules in the list, setting the appropriate target class of service (target-class-id). - QoS profile. This profile defines the traffic-scheduling to be applied to the flows for either Site-to-WAN, WAN-to-Site, or both directions. It contains the following information per class of service: rate-limit, latency, jitter and guaranteed bandwidth. * Multicast. This parameter identifies if the service is multicast, and if so, what is the role of the site in the customer multicast service topology (i.e., source, receiver, or both). It also defines the kind of multicast relationship with the customer (i.e., as a router requiring PIM, host requiring either IGMP or MLD, or both), as well as the support of IPv4, IPv6 or both. Similarly L2SM model parameters are described in section 5.9 and 5.10 of RFC 8466. * Bandwidth. This parameter is related to the bandwidth between both CE and PE and can be expressed as CIR/EIR/PIR, in the ingress or egress direction, taking the CE as the point of reference. * MTU. This parameter refers to the maximum layer-2 PDU frame size. * QoS. The specification of the QoS follows a similar structure to the one described in the case of L3SM. Some differences apply, for instance, at the time of QoS classification, which is performed on top of layer-2 parameters (e.g., MAC addresses). * BUM traffic. This parameter allows to determine if a site acts as source, receiver, or both. * Availability. This parameter in the L2SM model relates to the capability of supporting multi-homing. Barguil, et al. Expires 12 January 2023 [Page 14] Internet-Draft Network models for IETF Network Slices July 2022 On the other hand, the IETF NS NBI YANG model supports a number of SLOs and SLEs in the form of network slice service policy attributes. Such policy can apply to per-network slice, per-connection group or per-connection indivudually (over-writting of attributes is allowed as more granular information is provided). The following SLO attributes are detailed: * One-way / Two-way bandwidth, indicating the guaranteed minimum bandwidth between any two NSEs (unidirectional / bidirectional). * One-way / Two-way latency, indicating the guaranteed minimum latency between any two NSEs (unidirectional / bidirectional). * One-way / Two-way delay variation, indicating the maximum permissible delay variation of the slice (unidirectional / bidirectional). * One-way / Two-way packet loss, indicating the maximum permissible packet loss rate between endpoints (unidirectional / bidirectional). Additionally, the following SLEs are defined: * MTU, referring to the the maximum PDU size that the customer may use. * Security, indicating if encryption or other security measures are required between two endpoints. * Isolation, as a way of indicating the isolation level expected by the customer in the allocation of network resources. * Maximum occupancy level, to express the amount of flows to be admitted (and optionally a maximum number of countable resource units such as IP or MAC addresses). Thus, an initial mapping between L3SM, L2SM and IETF NS NBI model can be performed as indicated in the follwoing table. Barguil, et al. Expires 12 January 2023 [Page 15] Internet-Draft Network models for IETF Network Slices July 2022 +-------------------------+-------------------------+---------------------------------+ | L3SM (RFC 8299) | L2SM (RFC 8466) | IETF NSC NBI YANG model | +-------------------------+-------------------------+---------------------------------+ | Bandwidth | Bandwidth (CIR, PIR) | Sum of bandwidth SLO per NSE | | | | counting all connections | +-------------------------+-------------------------+---------------------------------+ | MTU (later 3 service) | MTU (later 2 service) | MTU attribute in SLE | +-------------------------+-------------------------+---------------------------------+ | QoS | QoS | QoS | | ........................| ........................|................................ | | - QoS classification | - QoS classification | Defined in the model as | | policy | policy | network-access-qos-policy-name | | | | to be applied per access-point | | ........................| ........................|................................ | | - QoS profile | - QoS profile | | | - rate-limit | - rate-limit | Defined in the model as | | | | incoming/outgong rate-limits | | | | per end-point (or access-point) | | - latency | - latency | One-way / Two-way latency SLO | | - jitter | - jitter | One-way / Two-way delay | | | | variation SLO | | - bandwidth | - bandwidth | One-way / Two-way bandwidth SLO | +-------------------------+-------------------------+---------------------------------+ | Multicast | Broadcast, Unknown, | The need of replication can be | | | Unicast and Multicast | inferred from | | | (BUM) | ns-connectivity-type. Further | | | | details are not available (e.g. | | | | source or receiver role) | +-------------------------+-------------------------+---------------------------------+ | | Availability as dual | Availability as the ratio of | | | homing | up-time to | | | | total_time(up-time+down-time) | +-------------------------+-------------------------+---------------------------------+ Table 1 Mapping of IETF NS NBI and LxSM service attributes. The following consideration can be made. * While the QoS profile in L3SM and L2SM applies per service class, the parameters in IETF NS NBI apply per connection. So if per- class granularity is required in an IETF network slice, then different connections have to be defined between the same end- points, one per service class. Barguil, et al. Expires 12 January 2023 [Page 16] Internet-Draft Network models for IETF Network Slices July 2022 * A number of attributes are not defined in L3SM nor L2SM such as packet loss, isolation or security. Then L3SM and L2SM could not be sufficient to realize IETF network slices with such specific needs, unless those other objectives and expectations are provided by other means (e.g., realizing the L3SM thorugh technologies guaranteing dedicated resource allocation such as OTN). 8. Network Slice Procedure Draft [draft-contreras-teas-slice-controller-models] shows the internal structure of an IETF Network Slice Controller which can be divided into two components: * IETF Network Slice Mapper: this high-level component processes the customer request, putting it into the context of the overall IETF Network Slices in the network. * IETF Network Slice Realizer: this high-level component processes the complete view of transport slices including the one requested by the customer, decides the proper technologies for realizing the IETF Network Slice and triggers its realization. Higher Level System | | NSC NBI +-------------------------+ | NSC | | | v | | +-----------------+ | | | | | | | NS Mapper | | | | | | | +-----------------+ | | | | | v | | +-----------------+ | | | | | | | NS Realizer | | | | | | | +-----------------+ | | | | +-------------------------+ | NSC SBI v Network Controllers Figure 8: IETF Network Slice Controller Structure Barguil, et al. Expires 12 January 2023 [Page 17] Internet-Draft Network models for IETF Network Slices July 2022 The details of IETF network slice mapper and realize are provided below for various implementation of NCS. 8.1. IETF Network Slice requested to Hierarchical Network Controller Referring to Figure 1 in an integrated architecture, the IETF Network Slice Controller (NCS) is part of a Hierarchical SDN controller module, the NSC's and the Hierarchical Network Controller should share the same internal data and the same NBI. Thus, the H-SDN module must be able to: * Map: The customer request received using the [draft-wd-teas-ietf- network-slice-nbi-yang] must be processed by the NCS. The mapping process takes the network-slice SLAs selected by the customer to available Routing Policies and Forwarding policies. * Realize: Create necessary network requests. The slice's realization can be translated into one or several LXNM Network requests, depending on the number of underlay controllers. Thus, the NCS must have a complete view of the network to map the orders and distribute them across domains. The realization should include the expansion/selection of Forwarding Policies, Routing Policies, VPN policies, and Underlay transport preference. To maintain the data coherence between the control layers, the IETF Network Slice ID ns-id used of the [draft-wd-teas-ietf-network-slice- nbi-yang] must be directly mapped to the transport-instance-id at the VPN-Node level. Barguil, et al. Expires 12 January 2023 [Page 18] Internet-Draft Network models for IETF Network Slices July 2022 + | | IETF Network Slice Request: draft-wd-teas-ietf-network-slice-nbi-yang | * network-slice-id | +-------------------v------------------+ | | | Hierarchical Network | | Controller/Orchestrator | | | | +-------------------------------+ | | | IETF Network Slice Controller | | | +-------------------------------+ | | | +-------------------+------------------+ IETF Network Slice Realizer: LXNM VPN-id | * transport-instance-id | | +--------------+---------------+ | | v v +-------------+----------+ +-------------+----------+ | Network Controller | | Network Controller | +-------------+----------+ +-------------+----------+ | | | | v v Network Elements Network Elements Figure 9 Workflow for the slice request in an integrated architecture. 8.2. IETF Network Slice requested to Network Slice Controller Referring to Figure 2 when the Network Slice Controller is a stand- alone controller module, the NSC's should perform the same two tasks described in section 6.1: * Map: Process the customer request. The customer request can be sent using the [draft-liu-teas-transport-network-slice-yang]. This draft allows the topology mapping of the Slice request. Barguil, et al. Expires 12 January 2023 [Page 19] Internet-Draft Network models for IETF Network Slices July 2022 * Realize: Create necessary network requests. The slice's realization will be translated into one LXNM Network request. As the NCS has a topological view of the network, the realization can include the customer's traffic engineering transport preferences and policies. + |IETF Network Slice Request draft-liu-teas-transport-network-slice-yang network-id | +-------------v-----------------+ | IETF Network Slice Controller | +-------------+-----------------+ | IETF Network Slice Realizer: LXNM VPN-id | * Underlay-transport * transport-instance-id | +-------------v----------------+ | Network Controller | +-------------+----------------+ | | v Network Elements Figure 10 Workflow for the slice request in an stand-alone architecture. 8.3. Network Slice Controller as part of the domain controller The Network Slice Controller can be a module of the Network controller. In that case, two options are available. One is to share the same device data model in the NBI and SBI of the SDN controller. The direct translation would reduce the service logic implemented at the SDN controller level, grouping the mapping and translation into a single task: * Realize: As the device models are part of the network controller's NBI thus, the realization can be done by the network controller applying a simple service logic to send the Network elements. Barguil, et al. Expires 12 January 2023 [Page 20] Internet-Draft Network models for IETF Network Slices July 2022 + | Slice Request based on | Device Models | | +------------------v------------------+ | | | Network | | Controller | | | | +------------------------------+ | | | Network Slice Controller | | | +------------------------------+ | | | +------------------+------------------+ | Device Models | v Network Elements Figure 11 Workflow for the slice request in an stand-alone architecture. A second option introduces a more complex logic in the network controller and creates an abstraction layer to process the transport slices. In that case, the controller should receive network slices creation requests and maintain the whole set of implemented slices: * Map & Realize: The mapping and realization can be done by the Domain controller applying the service logic to create policies directly on the Network elements. Barguil, et al. Expires 12 January 2023 [Page 21] Internet-Draft Network models for IETF Network Slices July 2022 + |Slice Request draft-liu-teas-transport-network-slice-yang-01 network-id | | +------------------v------------------+ | | | Network | | Controller | | | | +------------------------------+ | | | Network Slice Controller | | | +------------------------------+ | | | +------------------+------------------+ | | v Network Elements Figure 12 Workflow for the slice request in an stand-alone architecture. 9. Security Considerations There are two main aspects to consider. On the one hand, the IETF Network Slice has a set of security related requirements, such as hard isolation of the slice, or encryption of the communications through the slice. All those requirements need to be analyzed in detailed and clearly mapped to the Network Controller and device interfaces. On the other hand, the communication between the IETF network slicer and the network controller (or controllers or hierarchy of controllers) need to follow the same security considerations as with the network models. The network YANG modules defines schemas 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 [RFC8466]. Barguil, et al. Expires 12 January 2023 [Page 22] Internet-Draft Network models for IETF Network Slices July 2022 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. The following summarizes the foreseen risks of using the Network Models to instantiate IETF network Slices: * Malicious clients attempting to delete or modify VPN services that implements an IETF network slice. The malicious client could manipulate security related aspects of the network configuration that impact the requirements of the slice, failing to satisfy the customer requirement. * Unauthorized clients attempting to create/modify/delete a VPN hat implements an IETF network slice service. * Unauthorized clients attempting to read VPN services related information hat implements an IETF network slice * Malicious clients attempting to leak traffic of the slice. 10. IANA Considerations This document is informational and does not require IANA allocations. 11. Conclusions A wide variety of yang models are currently under definition in IETF that can be used by Network Controllers to instantiate IETF network slices. Some of the IETF slice requirements can be satisfied by multiple means, as there are multiple choices available. However, other requirements are still not covered by the existing models. A more detailed definition of those uncovered requirements would be needed. Finally, a consensus on the set of models to be exposed by Network Controllers would facilitate the deployment of IETF network slices. 12. Contributors Daniel King, daniel@olddog.co.uk 13. Acknowledgements This work is partially supported by the European Commission under Horizon 2020 grant agreement number 101015857 Secured autonomic traffic management for a Tera of SDN flows (Teraflow). Barguil, et al. Expires 12 January 2023 [Page 23] Internet-Draft Network models for IETF Network Slices July 2022 14. Normative References [I-D.contreras-teas-slice-nbi] Contreras, L. M., Homma, S., Ordonez-Lucena, J. A., Tantsura, J., and H. Nishihara, "IETF Network Slice Use Cases and Attributes for Northbound Interface of IETF Network Slice Controllers", Work in Progress, Internet- Draft, draft-contreras-teas-slice-nbi-06, 7 March 2022, . [I-D.ietf-opsawg-l2nm] Boucadair, M., Dios, O. G. D., Barguil, S., and L. A. Munoz, "A YANG Network Data Model for Layer 2 VPNs", Work in Progress, Internet-Draft, draft-ietf-opsawg-l2nm-19, 2 June 2022, . [I-D.ietf-teas-ietf-network-slices] Farrel, A., Drake, J., Rokui, R., Homma, S., Makhijani, K., Contreras, L. M., and J. Tantsura, "Framework for IETF Network Slices", Work in Progress, Internet-Draft, draft- ietf-teas-ietf-network-slices-12, 30 June 2022, . [I-D.ietf-teas-te-service-mapping-yang] Lee, Y., Dhody, D., Fioccola, G., Wu, Q., Ceccarelli, D., and J. Tantsura, "Traffic Engineering (TE) and Service Mapping YANG Data Model", Work in Progress, Internet- Draft, draft-ietf-teas-te-service-mapping-yang-11, 11 July 2022, . [I-D.ietf-teas-yang-te] Saad, T., Gandhi, R., Liu, X., Beeram, V. P., Bryskin, I., and O. G. D. Dios, "A YANG Data Model for Traffic Engineering Tunnels, Label Switched Paths and Interfaces", Work in Progress, Internet-Draft, draft-ietf-teas-yang-te- 29, 7 February 2022, . Barguil, et al. Expires 12 January 2023 [Page 24] Internet-Draft Network models for IETF Network Slices July 2022 [I-D.ietf-teas-ietf-network-slice-nbi-yang] Wu, B., Dhody, D., Rokui, R., Saad, T., and L. Han, "IETF Network Slice Service YANG Model", Work in Progress, Internet-Draft, draft-ietf-teas-ietf-network-slice-nbi- yang-02, 11 July 2022, . [I-D.liu-teas-transport-network-slice-yang] Liu, X., Tantsura, J., Bryskin, I., Contreras, L. M., Wu, Q., Belotti, S., and R. Rokui, "IETF Network Slice YANG Data Model", Work in Progress, Internet-Draft, draft-liu- teas-transport-network-slice-yang-05, 6 March 2022, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and A. Bierman, Ed., "Network Configuration Protocol (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, . [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018, . [RFC8453] Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for Abstraction and Control of TE Networks (ACTN)", RFC 8453, DOI 10.17487/RFC8453, August 2018, . [RFC8466] Wen, B., Fioccola, G., Ed., Xie, C., and L. Jalil, "A YANG Data Model for Layer 2 Virtual Private Network (L2VPN) Service Delivery", RFC 8466, DOI 10.17487/RFC8466, October 2018, . Barguil, et al. Expires 12 January 2023 [Page 25] Internet-Draft Network models for IETF Network Slices July 2022 [RFC8969] Wu, Q., Ed., Boucadair, M., Ed., Lopez, D., Xie, C., and L. Geng, "A Framework for Automating Service and Network Management with YANG", RFC 8969, DOI 10.17487/RFC8969, January 2021, . [RFC9182] Barguil, S., Gonzalez de Dios, O., Ed., Boucadair, M., Ed., Munoz, L., and A. Aguado, "A YANG Network Data Model for Layer 3 VPNs", RFC 9182, DOI 10.17487/RFC9182, February 2022, . Authors' Addresses Samier Barguil Telefonica Distrito T 28050 Madrid Spain Email: samier.barguilgiraldo.ext@telefonica.com Luis M. Contreras Telefonica Distrito T 28050 Madrid Spain Email: luismiguel.contrerasmurillo@telefonica.com Victor Lopez Nokia Calle de MarĂ­a Tubau, 9 28050 Madrid Spain Email: victor.lopez@nokia.com Reza Rokui Ciena Canada Email: rrokui@ciena.com Oscar Gonzalez de Dios Telefonica Distrito T 28050 Madrid Spain Email: oscar.gonzalezdedios@telefonica.com Barguil, et al. Expires 12 January 2023 [Page 26]