Network Working Group Z. Li Internet-Draft J. Dong Intended status: Standards Track Huawei Technologies Expires: October 24, 2021 April 22, 2021 Segment Routing for End-to-End IETF Network Slicing draft-li-spring-sr-e2e-ietf-network-slicing-00 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 can be realized as enhanced VPNs (VPN+), which is delivered by integrating the overlay VPN service with a Virtual Transport Network (VTN) as the underlay. An end-to-end IETF network slice may span multiple network domains. Within each domain, traffic of the end-to-end network slice service is mapped to a local VTN. When segment routing (SR) is used to build a multi-domain IETF network slice, information of the local network slices in each domain can be specified using special SR binding segments called VTN binding segments (VTN BSID). The multi-domain IETF network slice can be specified using a list of VTN BSIDs in the packet, each of which can be used by the corresponding domain edge nodes to steer the traffic of end-to-end IETF network slice into the specific VTN in the local domain. This document describes the functionality of VTN binding segment and its instantiation in SR-MPLS and SRv6. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. 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/. Li & Dong Expires October 24, 2021 [Page 1] Internet-Draft SR for E2E IETF Network Slicing April 2021 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 October 24, 2021. Copyright Notice Copyright (c) 2021 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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Segment Routing for IETF E2E Network Slicing . . . . . . . . 3 3. SRv6 VTN Binding Functions . . . . . . . . . . . . . . . . . 4 3.1. End.VTN.Encaps . . . . . . . . . . . . . . . . . . . . . 5 3.2. End.BVTN.Encaps . . . . . . . . . . . . . . . . . . . . . 5 3.3. End.B6VTN.Encaps . . . . . . . . . . . . . . . . . . . . 7 4. SR-MPLS VTN BSIDs . . . . . . . . . . . . . . . . . . . . . . 8 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 8.1. Normative References . . . . . . . . . . . . . . . . . . 9 8.2. Informative References . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction The definition and the characteristics of IETF network slice are introduced in [I-D.ietf-teas-ietf-network-slice-definition], and [I-D.ietf-teas-ietf-network-slice-framework] describes a general framework of IETF network slice. [I-D.ietf-teas-enhanced-vpn] describes the framework and the candidate component technologies for providing enhanced VPN services. Li & Dong Expires October 24, 2021 [Page 2] Internet-Draft SR for E2E IETF Network Slicing April 2021 VPN+ can be built from a VPN overlay and an underlying Virtual Transport Network (VTN) which has a customized network topology and a set of dedicated or shared resources in the underlay network. Enhanced VPN (VPN+) can be used for the realization of IETF network slices. [I-D.ietf-spring-sr-for-enhanced-vpn] describes the mechanisms and procedures of using resource-aware segments [I-D.ietf-spring-resource-aware-segments] to build SR based VTNs. [I-D.dong-teas-enhanced-vpn-vtn-scalability] describes the scalability considerations in the control plane and data plane to enable VPN+ services, and provide the suggestions to improve the scalability of VTN. In the control plane, It proposes the approach of decoupling the topology and resource attributes of VTN, so that multiple VTNs may share the same topology and the result of topology based path computation. In the data plane, it proposes to carry a VTN-ID of a network domain in the data packet to determine the set of resources reserved for the corresponding VTN. An IETF network slice may span multiple network domains. Within each domain, traffic of the end-to-end network slice is mapped to a local network slice. The VTN-ID which identifies the virtual underlay network in the local domain for the end-to-end network slice needs to be determined on the domain edge node. When segment routing (SR) is used to build a multi-domain IETF network slice, information of the local network slices in each domain can be specified using special SR binding segments called VTN binding segments (VTN BSID). The multi-domain IETF network slice can be specified using a list of VTN BSIDs in the packet, each of which can be used by the corresponding domain edge nodes to steer the traffic of end-to-end IETF network slice using the specific resource-aware segments or VTN-ID of the local domain. This document describes the functionality of the network slice binding segment and its instantiation in SR-MPLS and SRv6. 2. Segment Routing for IETF E2E Network Slicing [I-D.dong-teas-enhanced-vpn-vtn-scalability] describes the scalability considerations in the control plane and data plane to enable VPN+ services. In data plane, it proposes to carry a dedicated VTN-ID in data packet to determine the set of resources reserved for the corresponding VTN in a network domain. [I-D.li-teas-e2e-ietf-network-slicing] describes the framework of carrying network slice related identifiers in the data plane, each of the network slice IDs may have a different network scope. It Li & Dong Expires October 24, 2021 [Page 3] Internet-Draft SR for E2E IETF Network Slicing April 2021 provides an approach of mapping the global VTN-ID to local VTN-IDs at the network domain edge nodes. With Segment Routing, there are several optional approaches to realize the mapping between the end-to-end network slice and the network slice constructs in the local domain. 1. The first approach is to use one type of VTN binding segment to specify the mapping of traffic to a list of resource-aware segments of a local VTN. 2. The second approach is to use one type of VTN binding segment to determine a local VTN-ID, and instruct the encapsulation of the local VTN-ID into the packet at the domain edge node. 3. The third approach is to use one type of VTN binding segment to specify the mapping of traffic to a local VTN, the local VTN-ID is specified in the associated fields by the ingress node, and is encapsulated into the packet at the domain edge node. 4. The fourth approach is to use one type of VTN binding segment to specify the mapping of traffic to a SR policy which is bound to a local VTN. The function of the first type of VTN binding segment is similar to the function of the existing binding segment, the difference is it is associated with a particular VTN. The other types of the VTN binding segments are different from the existing binding segment, and their instantiation in SR-MPLS and SRv6 are described in the following sections. 3. SRv6 VTN Binding Functions [RFC8986] defines the SRv6 Network Programming concept and specifies the base set of SRv6 behaviors. The SRv6 End.B6.Encaps function is defined to instantiate the Binding SID in SRv6, which can be used as the first type of VTN binding function to specify the mapping of traffic to a list of resource-aware SRv6 segments of a local VTN. [I-D.dong-6man-enhanced-vpn-vtn-id] describes the mechanism of carrying the VTN-ID of a network domain in the IPv6 Hop-by-Hop (HBH) extension header. For the type 2, 3, 4 of VTN binding segments described in section 2, three new SRv6 Binding functions are defined in the following sections. Li & Dong Expires October 24, 2021 [Page 4] Internet-Draft SR for E2E IETF Network Slicing April 2021 3.1. End.VTN.Encaps A new SRv6 function called End.VTN.Encaps is defined. This is a variation of the End behavior. It instructs the endpoint node to determine the corresponding VTN-ID of the local domain based on the mapping relationship between the End.VTN.Encaps SID and the VTNs maintained on the endpoint. The VTN-ID is encapsulated in the VTN-ID option in the IPv6 HBH extension header. Any SID instance of this behavior is associated with one VTN-ID V and a source address A. When node N receives a packet whose IPv6 DA is S, and S is a local End.VTN.Encaps SID, N does the following: S01. When an SRH is processed { S02. If (Segments Left == 0) { S03. Stop processing the SRH, and proceed to process the next header in the packet, whose type is identified by the Next Header field in the routing header. S04. } S05. If (IPv6 Hop Limit <= 1) { S06. Send an ICMP Time Exceeded message to the Source Address with Code 0 (Hop limit exceeded in transit), interrupt packet processing, and discard the packet. S07. } S08. max_LE = (Hdr Ext Len / 2) - 1 S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) { S10. Send an ICMP Parameter Problem to the Source Address with Code 0 (Erroneous header field encountered) and Pointer set to the Segments Left field, interrupt packet processing, and discard the packet. S11. } S12. Decrement IPv6 Hop Limit by 1 S13. Decrement Segments Left by 1 S14. Update IPv6 DA with Segment List [Segments Left] S15. Set the VTN-ID option to V in the HBH Ext header S16. Submit the packet to the egress IPv6 FIB lookup for transmission to the new destination S17. } 3.2. End.BVTN.Encaps A new SRv6 function called End.BVTN.Encaps: Endpoint bound to a VTN with IPv6 encapsulation is defined. This is a variation of the End behavior. For the End.BVTN SID, its corresponding VTN-ID should be specified and encapsulated by the ingress node of SRv6 Path. It instructs the endpoint node to obtain the corresponding VTN-ID from Li & Dong Expires October 24, 2021 [Page 5] Internet-Draft SR for E2E IETF Network Slicing April 2021 the SRH, and encapsulate it in the VTN-ID option in the IPv6 HBH extension header. Through the End.BVTN.Encaps, the ingress node can flexibly specify the local VTN the packet traverses in the network. Any SID instance of this behavior is associated with one VTN-ID V and a source address A. There can be several options to carry the local VTN-ID corresponding to the End.BVTN.Encaps function: 1. The VTN-ID is carried in the argument field of the End.BVTN.Encaps SID. 2. The VTN-ID is carried in the SRH TLV field. 3. The VTN-ID is carried in the next SID following the End.BVTN.Encaps SID in the SID list. Editor's note: In the current version of this document, option 1 is preferred, in which the local VTN-ID is carried in the argument field of the SRv6 SID. When an ingress node of an SR path encapsulates the End.BVTN.Encaps SID into the packet, it SHOULD put the VTN-ID which the packet is expected to be mapped to into the argument part of the SID. When node N receives a packet whose IPv6 DA is S, and S is a local End.BVTN.Encaps SID, N does the following: Li & Dong Expires October 24, 2021 [Page 6] Internet-Draft SR for E2E IETF Network Slicing April 2021 S01. When an SRH is processed { S02. If (Segments Left == 0) { S03. Stop processing the SRH, and proceed to process the next header in the packet, whose type is identified by the Next Header field in the routing header. S04. } S05. If (IPv6 Hop Limit <= 1) { S06. Send an ICMP Time Exceeded message to the Source Address with Code 0 (Hop limit exceeded in transit), interrupt packet processing, and discard the packet. S07. } S08. max_LE = (Hdr Ext Len / 2) - 1 S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) { S10. Send an ICMP Parameter Problem to the Source Address with Code 0 (Erroneous header field encountered) and Pointer set to the Segments Left field, interrupt packet processing, and discard the packet. S11. } S12. Obtain the VTN-ID V from the argument part of the IPv6 DA S13. Decrement IPv6 Hop Limit by 1 S14. Decrement Segments Left by 1 S15. Update IPv6 DA with Segment List [Segments Left] S16. Set the VTN-ID option to V in the HBH Ext header S17. Submit the packet to the egress IPv6 FIB lookup for transmission to the new destination S18. } 3.3. End.B6VTN.Encaps A new SRv6 function called End.B6VTN.Encaps: Endpoint bound to a SRv6 Policy in a VTN with IPv6 encapsulation is defined in this section. This is a variation of the End behavior. It instructs the endpoint node to determine an SRv6 Policy in a specific VTN of the local domain, and encapsulate the SID list of the SR Policy and the VTN-ID in a new IPv6 header. Any SID instance of this behavior is associated with an SR Policy B, a VTN-ID V and a source address A. When node N receives a packet whose IPv6 DA is S, and S is a local End.B6VTN.Encaps SID, N does the following: Li & Dong Expires October 24, 2021 [Page 7] Internet-Draft SR for E2E IETF Network Slicing April 2021 S01. When an SRH is processed { S02. If (Segments Left == 0) { S03. Stop processing the SRH, and proceed to process the next header in the packet, whose type is identified by the Next Header field in the routing header. S04. } S05. If (IPv6 Hop Limit <= 1) { S06. Send an ICMP Time Exceeded message to the Source Address with Code 0 (Hop limit exceeded in transit), interrupt packet processing, and discard the packet. S07. } S08. max_LE = (Hdr Ext Len / 2) - 1 S09. If ((Last Entry > max_LE) or (Segments Left > Last Entry+1)) { S10. Send an ICMP Parameter Problem to the Source Address with Code 0 (Erroneous header field encountered) and Pointer set to the Segments Left field, interrupt packet processing, and discard the packet. S11. } S12. Decrement IPv6 Hop Limit by 1 S13. Decrement Segments Left by 1 S14. Update IPv6 DA with Segment List [Segments Left] S15. Push a new IPv6 header with its own SRH containing B, and the VTN-ID option set to V in the HBH Ext header S16. Set the outer IPv6 SA to A S17. Set the outer IPv6 DA to the first SID of B S18. Set the outer Payload Length, Traffic Class, Flow Label, Hop Limit, and Next Header fields S19. Submit the packet to the egress IPv6 FIB lookup for transmission to the new destination S20. } 4. SR-MPLS VTN BSIDs [I-D.li-mpls-enhanced-vpn-vtn-id] describes the mechanism of carrying the VTN-ID of a network domain in the MPLS extension header. With SR-MPLS data plane, VTN binding SIDs can be allocated by a domain edge node for the three types of VTN binding behaviors described in section 2. For the first type of VTN binding segment, a BSID is bound to a list of resource-aware segments of a local VTN. When a node receives a packet with a locally assigned VTN BSID, it determines the corresponding SID list which consists of the resource-aware segments of a local VTN, and encapsulates the SID list to the MPLS label stack. Li & Dong Expires October 24, 2021 [Page 8] Internet-Draft SR for E2E IETF Network Slicing April 2021 For the second type of VTN binding segment, a VTN BSID is bound to a VTN of the local network domain. When a node receives a packet with a locally assigned VTN BSID, it determines the corresponding local VTN-ID based on the mapping relationship between the VTN BSID and the VTN-ID, and encapsulates the packet with an MPLS VTN extension header which carries the local VTN-ID option. Note this requires to assign a VTN BSID for each VTN. For the third type of VTN binding segment, a VTN BSID is bound to a VTN of the local network domain, the VTN-ID is specified and encapsulated by the ingress node in the MPLS VTN extension header. When a node receives a packet with a locally assinged VTN BSID, it obtains the corresponding local VTN-ID from the VTN-ID list in the VTN extension header, and update the local VTN-ID option in the VTN extension header with the obtained VTN-ID. For the fourth type of VTN binding behavior, a VTN BSID is bound to a SR Policy in a VTN of the local network domain. When a node receives a packet with a locally assigned VTN BSID, it determines the corresponding SID list and the local VTN-ID, and encaps the packet with the SID list and an MPLS VTN extension header which carries the local VTN-ID option. Note this requires to assign a VTN BSID for each SR policy in each VTN the node participates in. 5. IANA Considerations TBD 6. Security Considerations TBD 7. Acknowledgements TBD 8. References 8.1. Normative References [I-D.ietf-teas-enhanced-vpn] Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A Framework for Enhanced Virtual Private Networks (VPN+) Service", draft-ietf-teas-enhanced-vpn-06 (work in progress), July 2020. Li & Dong Expires October 24, 2021 [Page 9] Internet-Draft SR for E2E IETF Network Slicing April 2021 [I-D.ietf-teas-ietf-network-slice-definition] Rokui, R., Homma, S., Makhijani, K., Contreras, L., and J. Tantsura, "Definition of IETF Network Slices", draft-ietf- teas-ietf-network-slice-definition-00 (work in progress), January 2021. [I-D.ietf-teas-ietf-network-slice-framework] Gray, E. and J. Drake, "Framework for IETF Network Slices", March 2021, . [I-D.li-teas-e2e-ietf-network-slicing] Li, Z. and J. Dong, "Framework for End-to-End IETF Network Slicing", April 2021, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 (SRv6) Network Programming", RFC 8986, DOI 10.17487/RFC8986, February 2021, . 8.2. Informative References [I-D.dong-6man-enhanced-vpn-vtn-id] Dong, J., Li, Z., Xie, C., and C. Ma, "Carrying Virtual Transport Network Identifier in IPv6 Extension Header", draft-dong-6man-enhanced-vpn-vtn-id-02 (work in progress), November 2020. [I-D.dong-teas-enhanced-vpn-vtn-scalability] Dong, J., Li, Z., Qin, F., and G. Yang, "Scalability Considerations for Enhanced VPN (VPN+)", draft-dong-teas- enhanced-vpn-vtn-scalability-01 (work in progress), November 2020. [I-D.ietf-spring-resource-aware-segments] Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., Li, Z., and F. Clad, "Introducing Resource Awareness to SR Segments", draft-ietf-spring-resource-aware-segments-01 (work in progress), January 2021. Li & Dong Expires October 24, 2021 [Page 10] Internet-Draft SR for E2E IETF Network Slicing April 2021 [I-D.ietf-spring-sr-for-enhanced-vpn] Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., Li, Z., and F. Clad, "Segment Routing based Virtual Transport Network (VTN) for Enhanced VPN", draft-ietf-spring-sr-for- enhanced-vpn-00 (work in progress), February 2021. [I-D.li-mpls-enhanced-vpn-vtn-id] Li, Z. and J. Dong, "Carrying Virtual Transport Network Identifier in MPLS Packet", draft-li-mpls-enhanced-vpn- vtn-id-00 (work in progress), February 2021. Authors' Addresses Zhenbin Li Huawei Technologies Huawei Campus, No. 156 Beiqing Road Beijing 100095 China Email: lizhenbin@huawei.com Jie Dong Huawei Technologies Huawei Campus, No. 156 Beiqing Road Beijing 100095 China Email: jie.dong@huawei.com Li & Dong Expires October 24, 2021 [Page 11]