]> Huawei Technologies

Beijing China jie.dong@huawei.com

China Unicom

Beijing China pangran@chinaunicom.cn

Huawei Technologies

Beijing China zhangka@huawei.com

Routing SPRING Internet-Draft Segment Routing (SR) Policy is a set of candidate paths, each consisting of one or more segment lists and the associated information. A Network Resource Partition (NRP) is a subset of the network resources and associated policies in the underlay network, which can be used to support one or a group of Enhanced VPN or RFC 9543 network slice services. In SR networks where there are multiple NRPs, an SR Policy may be associated with a particular NRP. Within an NRP, SR Policy can be used for forwarding traffic which is mapped to the NRP, so that the traffic can be provided with the subset of network resources and policy of the NRP for guaranteed performance. The association between SR Policy and NRP needs to be specified. This document defines extensions to the SR Policy Architecture to allow the association of the SR Policy candidate paths with NRPs.

Introduction The concept and architecture of Segment Routing (SR) Policy is defined in . An SR Policy is a set of candidate paths, each consisting of one or more segment lists. The head end node of an SR Policy may learn multiple candidate paths for an SR Policy. The header of a packet steered in an SR Policy is augmented with an ordered list of segments associated with that SR Policy. introduces the concept and the characteristics of network slice built using IETF technologies, and describes a general framework for RFC 9543 network slice management and operation. describes the framework and the candidate component technologies for delivering enhanced VPN services. Enhanced VPN can be used for the realization of RFC 9543 network slices. also introduces the concept Network Resource Partition (NRP), which is a subset of the network resources and associated policies in the underlay network. An NRP can be used to support one or a group of enhanced VPN or RFC 9543 network slice services. In SR networks, an NRP can be realized using NRP-specific resource-aware segments as defined in and . With this approach, a separate set of resource-aware SIDs need to be assigned for each NRP. For network scenarios where the number of NRP is large, suggests to introduce a dedicated NRP ID in the data packet. The data plane NRP ID is a network-wide identifier which can be used by network nodes to identify the set of network resources allocated to the NRP. This is considered as a scalable approach for realizing NRP, as the number of SR SIDs will not be proportional to the number of NRPs. The mechanisms for encapsulating NRP ID in data packet are out of the scope of this document and are specified in separate documents. The encapsulation of NRP information in IPv6 data plane is specified in , and the encapsulation of NRP information in MPLS data plane is specified in . In SR networks where there are multiple NRPs, an SR Policy may need to be associated with a particular NRP. Within the NRP, the SR Policy can be used for steering and forwarding traffic which is mapped to the NRP, so that the traffic can be forwarded along the selected path using the subset of network resources and policy of the NRP for guaranteed performance. For NRPs built with resource-aware segments, the association of SR Policy with NRP can be achieved by using NRP-specific resource-aware SIDs to construct the segment lists of the SR Policy. For NRPs built using dedicated data plane NRP ID, normal SR SIDs will be used for the segment lists of SR Policy, then the association between SR Policy and NRP needs to be specified explicitly. This document defines extensions to the SR Policy Architecture for associating SR Policy with NRP.

Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

Associating SR Policy with NRP As defined in , an SR Policy is associated with one or more candidate paths. A candidate path is the unit for signaling of an SR Policy to a headend via protocol extensions like the Path Computation Element Communication Protocol (PCEP) or BGP SR Policy . A candidate path consists of one or multiple segment lists. The segment lists are used for load balancing. The association between SR Policy and NRP is specified at the candidate path level. For an SR Policy associated with NRP, each of its candidate path needs to be associated with an NRP. The NRP ID is used to indicate the NRP to which the SR Policy candidate path is associated with. All the segment lists of the candidate path are associated with the same NRP. The protocol extensions for signaling of the SR Policy associated with NRP are described in and , and the mechanism for advertising the status of SR Policy which is associated with NRP is described in .

Updated SR Policy Information Model The information model of SR Policy associated with NRP can be shown as below:

Information Model of SR Policy with NRP Binding SID Candidate Path CP1 Preference Priority NRP Segment List 1 Weight W1 Segments Segment List 2 Weight W2 Segments Candidate Path CP2 Preference Priority NRP Segment List 3 Weight W3 Segments Segment List 4 Weight W4 Segments ... ]]>

Although the proposed information model allows that different candidate paths of one SR policy be associated with different NRPs, in most network scenarios it is considered that the association between an SR Policy and NRP is consistent, in such case all the candidate paths of one SR policy SHOULD be associated with the same NRP.

Packet Forwarding using SR Policy with NRP The mechanism of steering packets into SR Policy as described in section 8 of applies to SR Policy associated with NRP. This section describes the packet forwarding behavior using SR Policy with NRP. If the SR Policy candidate path selected as the best candidate path is associated with an NRP, the headend node of the SR Policy SHOULD encapsulate both the segment list and the associated NRP ID of the selected candidate path in the header of packets which are steered to the SR Policy. The segment list is used to instruct the path the packets need to traverse, and the NRP ID is used by each node along the path to identify the set of local network resources allocated to the NRP for the processing of the packet. For SR Policy with IPv6 data plane, the approach to encapsulate the NRP ID into the IPv6 header of the data packet is defined in . For SR Policy with MPLS data plane, one approach to encapsulate the NRP ID to the data packet is defined in .

Security Considerations This document introduces no additional security vulnerabilities in addition to the ones as described in .

IANA Considerations This document has no IANA actions.

Acknowledgements The authors would like to thank XXX for the review and discussion of this document.

References Normative References Segment Routing (SR) allows a node to steer a packet flow along any path. Intermediate per-path states are eliminated thanks to source routing. SR Policy is an ordered list of segments (i.e., instructions) that represent a source-routed policy. Packet flows are steered into an SR Policy on a node where it is instantiated called a headend node. The packets steered into an SR Policy carry an ordered list of segments associated with that SR Policy. This document updates RFC 8402 as it details the concepts of SR Policy and steering into an SR Policy. This document describes network slicing in the context of networks built from IETF technologies. It defines the term "IETF Network Slice" to describe this type of network slice and establishes the general principles of network slicing in the IETF context. The document discusses the general framework for requesting and operating IETF Network Slices, the characteristics of an IETF Network Slice, the necessary system components and interfaces, and the mapping of abstract requests to more specific technologies. The document also discusses related considerations with monitoring and security. This document also provides definitions of related terms to enable consistent usage in other IETF documents that describe or use aspects of IETF Network Slices. Huawei University of Surrey China Mobile KDDI Corporation Samsung This document describes the framework for Network Resource Partition (NRP) based Enhanced Virtual Private Networks (VPNs) to support the needs of applications with specific traffic performance requirements (e.g., low latency, bounded jitter). An NRP represents a subset of network resources and associated policies in the underlay network. NRP-based Enhanced VPNs leverage the VPN and Traffic Engineering (TE) technologies and add characteristics that specific services require beyond those provided by conventional VPNs. Typically, an NRP-based enhanced VPN will be used to underpin network slicing, but could also be of use in its own right providing enhanced connectivity services between customer sites. This document also provides an overview of relevant technologies in different network layers, and identifies some areas for potential new work. Huawei Technologies KDDI Corporation China Telecom China Mobile China Mobile This document describes the mechanism to associate network resources to Segment Routing Identifiers (SIDs). Such SIDs are referred to as resource-aware SIDs in this document. The resource-aware SIDs retain their original forwarding semantics, but with the additional semantics to identify the set of network resources available for the packet processing and forwarding action. The resource-aware SIDs can therefore be used to build SR paths or virtual networks with a set of reserved network resources. The proposed mechanism is applicable to both segment routing with MPLS data plane (SR-MPLS) and segment routing with IPv6 data plane (SRv6). Huawei Technologies KDDI Corporation China Telecom China Mobile China Mobile Enhanced VPNs aim to deliver VPN services with enhanced characteristics, such as guaranteed resources, latency, jitter, etc., so as to support customers requirements on connectivity services with these enhanced characteristics. Enhanced VPN requires integration between the overlay VPN connectivity and the characteristics provided by the underlay network. A Network Resource Partition (NRP) is a subset of the network resources and associated policies on each of a connected set of links in the underlay network. An NRP could be used as the underlay to support one or a group of enhanced VPN services. Segment Routing (SR) leverages the source routing paradigm. A node steers a packet through an ordered list of instructions, called "segments". A segment can represent topological or service based instructions. A segment can further be associated with a set of network resources used for executing the instruction. Such a segment is called resource-aware segment. Resource-aware Segment Identifiers (SIDs) may be used to build SR paths with a set of reserved network resources. In addition, a group of resource-aware SIDs may be used to build SR based NRPs, which provide customized network topology and resource attributes required by one or a group of enhanced VPN services. This document describes an approach to build SR based NRPs using resource-aware SIDs. The SR based NRP can be used to deliver enhanced VPN services in SR networks. Huawei Technologies Huawei Technologies China Mobile China Telecom Verizon Inc. A network slice offers connectivity services to a network slice customer with specific Service Level Objectives (SLOs) and Service Level Expectations (SLEs) over a common underlay network. RFC XXXX describes a framework for network slices built using networks that use IETF technologies. As part of that framework, the Network Resource Partition (NRP) is introduced as a set of network resources that are allocated from the underlay network to carry a specific set of network slice service traffic and meet specific SLOs and SLEs. As the demand for network slices increases, scalability becomes an important factor. Although the scalability of network slices can be improved by mapping a group of network slices to a single NRP, that design may not be suitable or possible for all deployments, thus there are concerns about the scalability of NRPs themselves. This document discusses some considerations for NRP scalability in the control and data planes. It also investigates a set of optimization mechanisms. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings. Informative References Huawei Technologies Huawei Technologies China Telecom China Telecom Verizon Inc. Virtual Private Networks (VPNs) provide different customers with logically separated connectivity over a common network infrastructure. With the introduction and evolvement of 5G and also in some existing network scenarios, some customers may require network connectivity services with advanced features comparing to conventional VPN services. Such kind of network service is called enhanced VPNs. Enhanced VPNs can be used, for example, to deliver network slice services. A Network Resource Partition (NRP) is a subset of the network resources and associated policies on each of a connected set of links in the underlay network. An NRP could be used as the underlay to support one or a group of enhanced VPN services. For packet forwarding in a specific NRP, some fields in the data packet are used to identify the NRP the packet belongs to, so that NRP-specific processing can be performed on each node along a path in the NRP. This document specifies a new IPv6 Hop-by-Hop option to carry the NRP related information in data packets, which could be used to identify the NRP-specific processing to be performed on the packets by each network node along a network path in the NRP. Huawei Technologies Huawei Technologies A Virtual Transport Network (VTN) is a virtual network which has a customized network topology and a set of dedicated or shared network resources allocated from the underlying physical network. Multiple VTNs can be created by network operator for using as the underlay for one or a group of VPNs services to provide enhanced VPN (VPN+) services. In packet forwarding, some fields in the data packet needs to be used to identify the VTN the packet belongs to, so that the VTN-specific processing can be executed on the packet. In the context of network slicing, a VTN can be instantiated as a Network Resource Partition (NRP). This document proposes a mechanism to carry the data plane VTN ID in an MPLS packet to identify the VTN the packet belongs to. The procedure for processing the VTN ID is also specified. Segment Routing (SR) enables any head-end node to select any path without relying on a hop-by-hop signaling technique (e.g., LDP or RSVP-TE). It depends only on "segments" that are advertised by link-state Interior Gateway Protocols (IGPs). An SR path can be derived from a variety of mechanisms, including an IGP Shortest Path Tree (SPT), an explicit configuration, or a Path Computation Element (PCE). This document specifies extensions to the Path Computation Element Communication Protocol (PCEP) that allow a stateful PCE to compute and initiate Traffic-Engineering (TE) paths, as well as a Path Computation Client (PCC) to request a path subject to certain constraints and optimization criteria in SR networks. This document updates RFC 8408. Ciena Corporation Ciena Corporation Juniper Networks, Inc. Huawei Technologies Nokia Segment Routing (SR) allows a node to steer a packet flow along any path. SR Policy is an ordered list of segments (i.e., instructions) that represent a source-routed policy. Packet flows are steered into an SR Policy on a node where it is instantiated called a headend node. An SR Policy is made of one or more candidate paths. This document specifies the Path Computation Element Communication Protocol (PCEP) extension to signal candidate paths of the SR Policy. Additionally, this document updates RFC 8231 to allow stateful bring up of an SR Label Switched Path (LSP), without using the path computation request and reply messages. This document is applicable to both Segment Routing over MPLS (SR-MPLS) and Segment Routing over IPv6 (SRv6). Huawei Technologies Cisco Systems Cisco Systems Microsoft Google A Segment Routing (SR) Policy is an ordered list of segments (i.e., instructions) that represent a source-routed policy. An SR Policy consists of one or more candidate paths, each consisting of one or more segment lists. A headend may be provisioned with candidate paths for an SR Policy via several different mechanisms, e.g., CLI, NETCONF, PCEP, or BGP. This document specifies how BGP may be used to distribute SR Policy candidate paths. It introduces a BGP SAFI to advertise a candidate path of a Segment Routing (SR) Policy and defines sub-TLVs for the Tunnel Encapsulation Attribute for signaling information about these candidate paths. This documents updates RFC9012 with extensions to the Color Extended Community to support additional steering modes over SR Policy. Huawei Technologies Huawei Technologies ZTE Corporation ZTE Corporation China Mobile China Mobile Juniper Networks Cisco Systems This document specifies the extensions to Path Computation Element Communication Protocol (PCEP) to carry Network Resource Partition (NRP) related information in the PCEP messages. The extensions in this document can be used to indicate the NRP-specific constraints and information needed in path computation, path status report and path initialization. ZTE Corporation Huawei ZTE Corporation China mobile China Telecom China Unicom A Network Resource Partition (NRP) is a network resource attribute associated with the SR policy. It is also an important attribute of the SR policy and needs to be reported to the external components. This document defines a new TLV which enable the headend to report the configuration and the states of an SR policy carrying the NRP information by using BGP-LS.