Framework for End-to-End IETF Network Slicing

Abstract

Network slicing can be used to meet the connectivity and performance requirement of different services or customers in a shared network. An IETF network slice may be used for 5G or other network scenarios. In the context of 5G, the 5G end-to-end network slices consist of three major types of network technology domains: Radio Access Network (RAN), Transport Network (TN) and Core Network (CN). The transport network slice can be realized as IETF network slices. In the transport network, the IETF network slice may span multiple network administrative domains.¶

In order to facilitate the mapping between network slices in different network technology domains and administrative domains, it is beneficial to carry the identifiers related to the 5G end-to-end network slice, the multi-domain IETF network slice together with the intra-domain network slice related identifier in the data packet.¶

This document describes the framework of end-to-end IETF network slicing, and introduces the identifiers related to 5G end-to-end network slice and the multi-domain IETF network slice. These identifiers can be carried in the data packet. The roles of the different identifiers in packet forwarding is also described. The network slice identifiers may be instantiated with different data planes.¶

1. Introduction

[I-D.ietf-teas-ietf-network-slices] defines the terminologies and the characteristics of IETF network slices. It also discusses the general framework, the components and interfaces for requesting and operating IETF network slices. A Network Resource Partition (NRP) is a collection of network resources in the underlay network that are available to carry traffic and meet the SLOs and SLEs.¶

[I-D.ietf-teas-enhanced-vpn] describes the framework and the candidate component technologies for providing enhanced VPN (VPN+) services based on existing VPN and Traffic Engineering (TE) technologies with enhanced characteristics that specific services require above traditional VPNs. It also introduces the concept of Virtual Transport Network (VTN), which is a virtual underlay network consisting of a set of dedicated or shared network resources allocated from the physical underlay network, and is associated with a customized network topology. VPN+ services can be delivered by mapping one or a group of overlay VPNs to the appropriate VTNs as the underlay, so as to provide the network characteristics required by the customers. Enhanced VPN (VPN+) and VTN can be used for the realization of IETF network slices. In the context of IETF network slicing, NRP can be seen as an instantiation of VTN.¶

[I-D.dong-teas-nrp-scalability] describes the scalability considerations in the control plane and data plane of NRP, and proposed several suggestions to improve the scalability. In the control plane, It proposes the approach of decoupling the topology and resource attributes of NRP, so that multiple NRPs may share the same topology attributes and the result of topology based path computation. In the data plane, it proposes to carry a global NRP-ID of a network domain in the data packet to determine the set of resources reserved for the corresponding NRP.¶

An IETF network slice may span multiple network administrative domains. Further in the context of 5G, there are end-to-end network slices which consists of three major types of network technology domains: Radio Access Network (RAN), Transport Network (TN) and Core Network (CN). In order to facilitate the mapping between network slices in different network technology domains and administrative domains, it may be beneficial to carry the identifiers related to the 5G end-to-end network slice, the identifiers of the multi-domain IETF network slices together with the intra-domain network slices related identifiers in the data packet.¶

This document describes the typical scenarios of end-to-end network slicing, and the framework of concatenating network slices in different network technology domains and administrative domains. Multiple network slice related identifiers are defined for network slices with different network scopes. These network slice related identifiers can be instantiated using different data planes, such as IPv6 and MPLS.¶

2. Framework

    /----\        /----\         /----\          /----\         /----\
   /      \     //      \\     //      \\      //      \\      /      \
  |  RAN   |---|   TN-1   |---|   TN-2   |----|   TN-3   |----|  Core  |
   \      /     \\      //     \\      //      \\      //      \      /
    \----/        \----/         \----/          \----/         \----/

  5G Network Slice
  o--------------------------------------------------------------------o
             IETF Network Slice (VPN+)
           o--------------------------------------------------o
                Global NRP (VTN)
              o===========================================o
                Local NRP-1    Local NRP-2     Local NRP-3
              o************o  o************o  o***********o

Figure 1. 5G end-to-end network slicing scenario

One typical scenario of 5G end-to-end network slicing is shown in figure 1. The 5G end-to-end network slice is identified by the S-NSSAI (Single Network Slice Selection Assistance Information). In the transport network, the 5G network slice is mapped to an IETF network slice. In a multi-domain transport network, an IETF network slice can be realized with a multi-domain VPN+ service. In the underlay network, the multi-domain VPN+ service can be supported by a multi-domain VTN, which is the concatenation of multiple intra-domain NRPs in different domains. In each domain, a domain-significant NRP-ID can be carried in the packet to identify the set of network resource reserved for the NRP in the corresponding domain. Note this is similar to the Option C mode of inter-domain VPN service [RFC4364]. Using Option A or Option B mode of inter-domain VPN for 5G end-to-end network slicing is also possible, which is out of the scope of the current version of this document.¶

In order to concatenate multiple domain-wide NRPs into a multi-domain NRP, the global NRP-ID can be carried in the packet, which is used by the domain border nodes to map to the local NRP-IDs in each domain. And in order to facilitate the network slice mapping between RAN, Core network and transport network, the S-NSSAI may be carried in the packet sent to the transport network, which can be used by the transport network to map the 5G end-to-end network slice to the corresponding IETF network slice.¶

According to the above end-to-end network slicing scenario, there can be three network slice related identifiers in the data packet:¶

• Domain NRP-ID: This is the NRP-ID as defined in [I-D.dong-teas-nrp-scalability]. It is used by the network nodes in a network domain to determine the set of local network resources reserved for an NRP. It SHOULD be processed by each hop along the path in the domain.¶
• End-to-end NRP-ID: This is the identifier which uniquely identifies a multi-domain NRP. In each network domain, the domain border nodes map the global NRP-ID to the domain NRP-ID for packet forwarding.¶
• 5G end-to-end network slice ID (S-NSSAI): This is the identifier of the 5G end-to-end network slice. When required, it may be used by the network nodes to provide traffic monitoring at the end-to-end network slice granularity.¶

For the above network slice identifiers, the domain NRP-ID is mandatory, the global NRP-ID and the 5G S-NSSAI are optional. The existence of the Global NRP-ID depends on whether the NRP spans multiple network domains in the transport network, and how the domain NRP-IDs are managed. In some network scenarios, different network domains can have consistent NRP ID allocation, then the domain NRP-ID can has the same value as a global NRP-ID. The existence of the 5G S-NSSAI depends on whether an IETF network slice is used as part of the 5G end-to-end network slice.¶

3. Requirements on E2E IETF Network Slicing

This section lists the requirements on E2E IETF network slicing.¶

7. References