idnits 2.17.1 draft-zhu-lsr-isis-sr-vtn-flexalgo-00.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (March 9, 2020) is 1507 days in the past. Is this intentional? 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'I-D.dong-spring-sr-for-enhanced-vpn') == Outdated reference: A later version (-26) exists of draft-ietf-lsr-flex-algo-06 == Outdated reference: A later version (-19) exists of draft-ietf-lsr-isis-srv6-extensions-06 == Outdated reference: A later version (-10) exists of draft-dong-lsr-sr-enhanced-vpn-02 == Outdated reference: A later version (-28) exists of draft-ietf-spring-srv6-network-programming-12 == Outdated reference: A later version (-17) exists of draft-ietf-teas-enhanced-vpn-05 Summary: 1 error (**), 0 flaws (~~), 10 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 LSR Working Group Y. Zhu 3 Internet-Draft China Telecom 4 Intended status: Standards Track J. Dong 5 Expires: September 10, 2020 Z. Hu 6 Huawei Technologies 7 March 9, 2020 9 Using Flex-Algo for Segment Routing based VTN 10 draft-zhu-lsr-isis-sr-vtn-flexalgo-00 12 Abstract 14 As defined in I-D.ietf-teas-enhanced-vpn, enhanced VPN (VPN+) aims to 15 provide enhanced VPN service to support the needs of enhanced 16 isolation and stringent performance requirements. VPN+ requries 17 integration between the overlay VPN and the underlay network. A 18 Virtual Transport Network (VTN) is a virtual network which consists 19 of a subset of network toplogy and network resources allocated from 20 the underlay network. A VTN could be used as the underlay for one or 21 a group of VPN+ services. 23 I-D-dong-lsr-sr-enhanced-vpn defines the IGP mechanisms with 24 necessary extensions to build a set of Segment Routing (SR) based 25 VTNs. This document describes a simplified mechanism to build the SR 26 based VTNs using SR Flex-Algo with minor extensions to IGP L2 bundle. 28 Requirements Language 30 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 31 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 32 document are to be interpreted as described in RFC 2119 [RFC2119]. 34 Status of This Memo 36 This Internet-Draft is submitted in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF). Note that other groups may also distribute 41 working documents as Internet-Drafts. The list of current Internet- 42 Drafts is at https://datatracker.ietf.org/drafts/current/. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on September 10, 2020. 50 Copyright Notice 52 Copyright (c) 2020 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (https://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 68 2. Advertisement of SR VTN Topology Attribute . . . . . . . . . 3 69 3. Extensions to IGP L2 Bundles . . . . . . . . . . . . . . . . 4 70 4. Scalability Considerations . . . . . . . . . . . . . . . . . 5 71 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 72 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 73 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 74 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 75 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 76 8.2. Informative References . . . . . . . . . . . . . . . . . 7 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 79 1. Introduction 81 Enhanced VPN (VPN+) is an enhancement to VPN services to support the 82 needs of new applications, particularly including the applications 83 that are associated with 5G services. These applications require 84 enhanced isolation and have more stringent performance requirements 85 than that can be provided with traditional overlay VPNs. These 86 properties cannot be met with pure overlay networks, as they require 87 integration between the underlay and the overlay networks. 88 [I-D.ietf-teas-enhanced-vpn] specifies the framework of enhanced VPN 89 and describes the candidate component technologies in different 90 network planes and layers. An enhanced VPN may be used for 5G 91 transport network slicing, and will also be of use in other generic 92 scenarios. 94 To meet the requirement of enhanced VPN services, a number of virtual 95 transport networks (VTN) need to be created, each with a subset of 96 the underlay network topology and a set of network resources 97 allocated to meet the requirement of a specific VPN+ service or a 98 group of VPN+ services. Another existing approach is to build a set 99 of point-to-point paths, each with a set of network resource reserved 100 along the path, such paths are called Virtual Transport Paths (VTPs). 101 Although using a set of dedicated VTPs can provide similar 102 characteristics, it has some scalability issues in large networks. 104 [I-D.dong-spring-sr-for-enhanced-vpn] specifies how segment routing 105 (SR) [RFC8402] can be used to build virtual transport networks (VTNs) 106 with the required network topology and network resource attributes to 107 support enhanced VPN services. With segment routing based data 108 plane, Segment Identifiers (SIDs) can be used to represent the 109 topology and the set of network resources allocated by network nodes 110 to a virtual network. The SIDs of each VTN and the associated 111 topology and resource attributes need to be distributed using control 112 plane. 114 [I-D.dong-lsr-sr-enhanced-vpn] defines the IGP mechanisms with 115 necessary extensions to build a set of Segment Routing (SR) based 116 VTNs. The VTNs could be used as the underlay of the enhanced VPN 117 service. The mechanism described in [I-D.dong-lsr-sr-enhanced-vpn] 118 allows flexible combination of the topology and resource attribute to 119 build customized VTNs. In some network scenarios, it is assumed that 120 each VTN has an independent topology and a set of dedicated network 121 resources. This document describes a simplified mechanism to build 122 the SR based VTNs in those scenarios. 124 2. Advertisement of SR VTN Topology Attribute 126 [I-D.ietf-lsr-flex-algo] specifies the mechanism to provide 127 distributed constraint-path computation, and the usage of SR-MPLS 128 prefix-SIDs and SRv6 locators for steering traffic along the 129 constrained paths. 131 The Flex-Algo definition provides the topological constraints for 132 path computation. When each VTN has an independent network topology, 133 the Flex-Algo Identifier could be used as the identifier of a VTN in 134 control plane. Thus the topology attribute of a VTN could be defined 135 using Flex-Algo. 137 According to the network nodes' participation of a Flex-Algo, and the 138 rules of including or excluding specific Admin Groups (colors) and 139 Shared Risk Link Groups (SRLGs), the topology attribute of a VTN can 140 be determined using the associated Flex-Algo. 142 With the mechanisms defined in[RFC8667] [I-D.ietf-lsr-flex-algo], 143 prefix-SID advertisement can be associated with a specific topology 144 and a specific algorithm, which can be a Flex-Algo. This allows the 145 nodes to use the prefix-SID to steer traffic along distributed 146 computed paths according to the identified Flex-Algo in the 147 associated topology. 149 [I-D.ietf-lsr-isis-srv6-extensions] specifies the IS-IS extensions to 150 support SRv6 data plane, in which the SRv6 locators advertisement can 151 be associated with a specific topology and a specific algorithm, 152 which can be a Flex-Algo. This allows the the nodes to used the SRv6 153 locator to steer traffic along distributed computed paths according 154 to the identified Flex-Algo in the associated topology. In addition, 155 topology/algorithm specific SRv6 End SID and End.X SID can be used to 156 enforce traffic over the LFA computed backup path. 158 3. Extensions to IGP L2 Bundles 160 In order to perform constraint based path computation for each VTN on 161 network controller and the ingress nodes, the resource attribute of 162 VTN also needs to be advertised. 164 [RFC8668] was defined to advertise link attributes of the Layer 2 165 bundle member links. In this section it is extended to advertise the 166 network resource attributes associated with different VTNs on one 167 Layer 3 interface. 169 On a Layer 3 interface, it is assumed that different subset of the 170 link resources are allocated to different VTNs it participates in. A 171 subset of the link resource can be seen as a virtual layer-2 member 172 link of the Layer 3 interface. If the Layer 3 interface is a L2 link 173 bundle, it is also possible that the subset of link resource for a 174 specific VTN is provided by a physical Layer 2 member link. 176 A new flag "V" (Virtual) is defined in the flag field of the Parent 177 L3 Neighbor Descriptor in the L2 Bundle Member Attributes TLV (25). 179 0 1 2 3 4 5 6 7 180 +-+-+-+-+-+-+-+-+ 181 |P|V| | 182 +-+-+-+-+-+-+-+-+ 184 V flag: When the V flag is set, it indicates the advertised member 185 links under the Parent L3 link are virtual member links. When the V 186 flag is clear, it indicates the member links are physical member 187 links. 189 For each virtual or physical member link, the TE attributes such as 190 the Maximum Link Bandwidth and admin-groups can be advertised using 191 the mechanism as defined in [RFC8668]. 193 In order to associate different virtual or physical member links with 194 the corresponding VTNs, each member link SHOULD be assigned with a 195 dedicated admin-group or extended admin-group (color), which is 196 included in the definition of the corresponding Flex-Algo. Note that 197 in this case the admin-group or extended admin-group of the Layer 3 198 interface SHOULD be set to the union of all the admin-groups of the 199 virtual or physical member links. This is to ensure that the Layer 3 200 link will be included in the constraint-based computation of the 201 corresponding Flex-Algo. 203 4. Scalability Considerations 205 The mechanism described in this document requires that each VTN maps 206 to an independent Flex-Algo. Even if multiple VTNs share the same 207 topology constraints. While this brings the benefits of simplicity, 208 it also has some limitations. For example, it means that even if 209 multiple VTNs have the same topology constraints, they would still 210 need to be identified using different Flex-Algos in the control 211 plane. Then this requires that for each VTN, independent path 212 computation would be executed. The number of VTNs supported in a 213 network may be dependent on the number of Flex-Algos supported, which 214 is related to the control plane computation overhead. 216 Another aspect which may impact the number of VTNs supported is that 217 at most 128 Flex-Algos can be defined in a network. 219 5. Security Considerations 221 This document introduces no additional security vulnerabilities to 222 IS-IS and OSPF. 224 The mechanism proposed in this document is subject to the same 225 vulnerabilities as any other protocol that relies on IGPs. 227 6. IANA Considerations 229 This document does not request any IANA actions. 231 7. Acknowledgments 233 The authors would like to thank Zhenbin Li for the review and 234 discussion of this document. 236 8. References 237 8.1. Normative References 239 [I-D.dong-spring-sr-for-enhanced-vpn] 240 Dong, J., Bryant, S., Miyasaka, T., Zhu, Y., Qin, F., and 241 Z. Li, "Segment Routing for Resource Partitioned Virtual 242 Networks", draft-dong-spring-sr-for-enhanced-vpn-06 (work 243 in progress), December 2019. 245 [I-D.ietf-lsr-flex-algo] 246 Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and 247 A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex- 248 algo-06 (work in progress), February 2020. 250 [I-D.ietf-lsr-isis-srv6-extensions] 251 Psenak, P., Filsfils, C., Bashandy, A., Decraene, B., and 252 Z. Hu, "IS-IS Extension to Support Segment Routing over 253 IPv6 Dataplane", draft-ietf-lsr-isis-srv6-extensions-06 254 (work in progress), March 2020. 256 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 257 Requirement Levels", BCP 14, RFC 2119, 258 DOI 10.17487/RFC2119, March 1997, 259 . 261 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 262 Topology (MT) Routing in Intermediate System to 263 Intermediate Systems (IS-ISs)", RFC 5120, 264 DOI 10.17487/RFC5120, February 2008, 265 . 267 [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic 268 Engineering", RFC 5305, DOI 10.17487/RFC5305, October 269 2008, . 271 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 272 Decraene, B., Litkowski, S., and R. Shakir, "Segment 273 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 274 July 2018, . 276 [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., 277 Bashandy, A., Gredler, H., and B. Decraene, "IS-IS 278 Extensions for Segment Routing", RFC 8667, 279 DOI 10.17487/RFC8667, December 2019, 280 . 282 [RFC8668] Ginsberg, L., Ed., Bashandy, A., Filsfils, C., Nanduri, 283 M., and E. Aries, "Advertising Layer 2 Bundle Member Link 284 Attributes in IS-IS", RFC 8668, DOI 10.17487/RFC8668, 285 December 2019, . 287 8.2. Informative References 289 [I-D.dong-lsr-sr-enhanced-vpn] 290 Dong, J., Hu, Z., and S. Bryant, "IGP Extensions for 291 Segment Routing based Enhanced VPN", draft-dong-lsr-sr- 292 enhanced-vpn-02 (work in progress), November 2019. 294 [I-D.ietf-spring-srv6-network-programming] 295 Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., 296 Matsushima, S., and Z. Li, "SRv6 Network Programming", 297 draft-ietf-spring-srv6-network-programming-12 (work in 298 progress), March 2020. 300 [I-D.ietf-teas-enhanced-vpn] 301 Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A 302 Framework for Enhanced Virtual Private Networks (VPN+) 303 Services", draft-ietf-teas-enhanced-vpn-05 (work in 304 progress), February 2020. 306 Authors' Addresses 308 Yongqing Zhu 309 China Telecom 311 Email: zhuyq8@chinatelecom.cn 313 Jie Dong 314 Huawei Technologies 316 Email: jie.dong@huawei.com 318 Zhibo Hu 319 Huawei Technologies 321 Email: huzhibo@huawei.com