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Dong 3 Internet-Draft Z. Hu 4 Intended status: Standards Track Huawei Technologies 5 Expires: January 12, 2022 R. Pang 6 China Unicom 7 July 11, 2021 9 BGP SR Policy Extensions for Virtual Transport Network 10 draft-dong-idr-sr-policy-vtn-01 12 Abstract 14 Segment Routing (SR) Policy is a set of candidate paths, each 15 consisting of one or more segment lists and the associated 16 information. The header of a packet steered in an SR Policy is 17 augmented with an ordered list of segments associated with that SR 18 Policy. In scenarios where multiple Virtual Transport Networks 19 (VTNs) exist in the network, the VTN in which the SR policy is 20 instantiated may also need to be specified, so that the header of the 21 packet can also be augmented with the information associated with the 22 VTN. An SR Policy candidate path can be distributed using BGP SR 23 Policy. This document defines extensions to BGP SR policy to specify 24 the VTN associated with the SR policy. 26 Status of This Memo 28 This Internet-Draft is submitted in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF). Note that other groups may also distribute 33 working documents as Internet-Drafts. The list of current Internet- 34 Drafts is at https://datatracker.ietf.org/drafts/current/. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 This Internet-Draft will expire on January 12, 2022. 43 Copyright Notice 45 Copyright (c) 2021 IETF Trust and the persons identified as the 46 document authors. All rights reserved. 48 This document is subject to BCP 78 and the IETF Trust's Legal 49 Provisions Relating to IETF Documents 50 (https://trustee.ietf.org/license-info) in effect on the date of 51 publication of this document. Please review these documents 52 carefully, as they describe your rights and restrictions with respect 53 to this document. Code Components extracted from this document must 54 include Simplified BSD License text as described in Section 4.e of 55 the Trust Legal Provisions and are provided without warranty as 56 described in the Simplified BSD License. 58 Table of Contents 60 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 61 2. Specification of Requirements . . . . . . . . . . . . . . . . 3 62 3. VTN Information Encoding in SR Policy . . . . . . . . . . . . 3 63 4. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 65 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 66 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 67 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 68 8.1. Normative References . . . . . . . . . . . . . . . . . . 5 69 8.2. Informative References . . . . . . . . . . . . . . . . . 6 70 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 72 1. Introduction 74 The concept of Segment Routing (SR) policy is defined in 75 [I-D.ietf-spring-segment-routing-policy]. An SR Policy is a set of 76 candidate paths, each consisting of one or more segment lists. The 77 head end of an SR Policy may learn multiple candidate paths for an SR 78 Policy. The header of a packet steered in an SR Policy is augmented 79 with an ordered list of segments associated with that SR Policy. The 80 BGP extensions to distribute SR Policy candidate paths is defined in 81 [I-D.ietf-idr-segment-routing-te-policy]. 83 The concept of Virtual Transport Network (VTN) is introduced in 84 [I-D.ietf-teas-enhanced-vpn]. A VTN is a virtual underlay network 85 which has customized network topology and a set of dedicated or 86 shared network resources. In a network, different VTNs may be 87 created to meet different service requirements, and different 88 services can be mapped to different VTNs. 90 In scenarios where multiple virtual networks (VTNs) exist in the 91 network, the identifier of VTN in which the SR policy is instantiated 92 may also need to be specified, so that the header of data packet can 93 also be augmented with the information of the associated VTN. This 94 document defines the BGP extensions to specify the VTN ID associated 95 with a candidate path of SR policy. 97 2. Specification of Requirements 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 101 document are to be interpreted as described in RFC 2119 [RFC2119]. 103 3. VTN Information Encoding in SR Policy 105 In order to specify the VTN the candidate path of SR policy is 106 associated with, a new sub-TLV called "VTN sub-TLV" is defined in the 107 BGP Tunnel Encapsulation Attribute [I-D.ietf-idr-tunnel-encaps]. The 108 VTN sub-TLV can be carried in the BGP Tunnel Encapsulation Attribute 109 with the tunnel type set to SR Policy. 111 The VTN sub-TLV is optional and MUST NOT appear more than once for 112 one SR Policy candidate path. If the VTN sub-TLV appears more than 113 once, the associated BGP SR Policy NLRI is considered malformed and 114 the "treat-as-withdraw" strategy of [RFC7606] is applied. 116 The VTN sub-TLV has the following format: 118 0 1 2 3 119 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 120 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 121 | Type | Length | Flags | RESERVED | 122 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 123 | VTN ID (4 octets) | 124 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 125 Figure 1. VTN Sub-TLV 127 where: 129 o Type: 123 131 o Length: 6 133 o Flags: 1-octet flag field. None is defined at this stage. The 134 flags SHOULD be set to zero on transmission and MUST be ignored on 135 receipt. 137 o RESERVED: 1 octet of reserved bits. All of the reserved bits 138 SHOULD be set to zero on transmission and MUST be ignored on 139 receipt. 141 o VTN ID: A 32-bit global significant identifier which is used to 142 identify a VTN. Value 0 and 0xFFFFFFFF are reserved. 144 The encoding structure of BGP SR Policy with the VTN sub-TLV is 145 expressed as below: 147 SR Policy SAFI NLRI: 148 Attributes: 149 Tunnel Encaps Attribute (23) 150 Tunnel Type: SR Policy 151 Binding SID 152 Preference 153 Priority 154 Policy Name 155 Explicit NULL Label Policy (ENLP) 156 VTN 157 Segment List 158 Weight 159 Segment 160 Segment 161 ... 162 ... 164 4. Procedures 166 When a candidate path of SR policy is associated with a specific VTN, 167 the originating node of SR policy SHOULD include the associated VTN 168 in the BGP Tunnel Encapsulation Attribute of the BGP SR policy. The 169 setting of other fields and attributes in BGP SR policy SHOULD 170 follows the mechanism as defined in 171 [I-D.ietf-idr-segment-routing-te-policy]. 173 When a BGP speaker receives an SR Policy which is acceptable and 174 usable according to the rules as defined in 175 [I-D.ietf-idr-segment-routing-te-policy], and the SR Policy candidate 176 path selected as the best candidate path is associated with a VTN, 177 the receiver node of the SR policy SHOULD encapsulate VTN-specific 178 information to the header of packets steered to the SR policy. For 179 SR Policy with IPv6 data plane, the possible approach is to 180 encapsulate the VTN-ID to the packet using the mechanism defined in 181 [I-D.dong-6man-enhanced-vpn-vtn-id]. For SR Policy with MPLS data 182 plane, the usage of the VTN information is similar, the possible 183 mechanism to encapsulate the VTN-ID to the packet is defined in 184 [I-D.li-mpls-enhanced-vpn-vtn-id] 186 Although the proposed mechanism allows that different candidate paths 187 in one SR policy be associated with different VTNs, in normal network 188 scenarios it is considered that the mapping between service to VTN is 189 consistent, in such case all candidate paths of one SR policy are 190 associated with the same VTN. 192 5. Security Considerations 194 The security considerations of BGP and BGP SR policy apply to this 195 document. 197 6. IANA Considerations 199 IANA has assigned the sub-TLV type as defined in Section 3 from "BGP 200 Tunnel Encapsulation Attribute sub-TLVs" registry. 202 Value Description Reference 203 ---------------------------------------------------- 204 123 VTN This document 206 7. Acknowledgments 208 The authors would like to thank Guoqi Xu, Lei Bao and Haibo Wang for 209 the review and discussion of this document. 211 8. References 213 8.1. Normative References 215 [I-D.ietf-idr-segment-routing-te-policy] 216 Previdi, S., Filsfils, C., Talaulikar, K., Mattes, P., 217 Rosen, E., Jain, D., and S. Lin, "Advertising Segment 218 Routing Policies in BGP", draft-ietf-idr-segment-routing- 219 te-policy-11 (work in progress), November 2020. 221 [I-D.ietf-idr-tunnel-encaps] 222 Patel, K., Velde, G. V. D., Sangli, S. R., and J. Scudder, 223 "The BGP Tunnel Encapsulation Attribute", draft-ietf-idr- 224 tunnel-encaps-22 (work in progress), January 2021. 226 [I-D.ietf-spring-segment-routing-policy] 227 Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and 228 P. Mattes, "Segment Routing Policy Architecture", draft- 229 ietf-spring-segment-routing-policy-11 (work in progress), 230 April 2021. 232 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 233 Requirement Levels", BCP 14, RFC 2119, 234 DOI 10.17487/RFC2119, March 1997, 235 . 237 [RFC7606] Chen, E., Ed., Scudder, J., Ed., Mohapatra, P., and K. 238 Patel, "Revised Error Handling for BGP UPDATE Messages", 239 RFC 7606, DOI 10.17487/RFC7606, August 2015, 240 . 242 8.2. Informative References 244 [I-D.dong-6man-enhanced-vpn-vtn-id] 245 Dong, J., Li, Z., Xie, C., and C. Ma, "Carrying Virtual 246 Transport Network Identifier in IPv6 Extension Header", 247 draft-dong-6man-enhanced-vpn-vtn-id-03 (work in progress), 248 February 2021. 250 [I-D.ietf-teas-enhanced-vpn] 251 Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A 252 Framework for Enhanced Virtual Private Network (VPN+) 253 Services", draft-ietf-teas-enhanced-vpn-07 (work in 254 progress), February 2021. 256 [I-D.li-mpls-enhanced-vpn-vtn-id] 257 Li, Z. and J. Dong, "Carrying Virtual Transport Network 258 Identifier in MPLS Packet", draft-li-mpls-enhanced-vpn- 259 vtn-id-00 (work in progress), February 2021. 261 Authors' Addresses 263 Jie Dong 264 Huawei Technologies 266 Email: jie.dong@huawei.com 268 Zhibo Hu 269 Huawei Technologies 271 Email: huzhibo@huawei.com 273 Ran Pang 274 China Unicom 276 Email: pangran@chinaunicom.cn