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Li 3 Internet-Draft C. Li 4 Intended status: Standards Track Huawei Technologies 5 Expires: October 22, 2021 April 20, 2021 7 Extensions for SRv6 traversing IPv4 network 8 draft-li-spring-srv6-traverse-ipv4-00 10 Abstract 12 As the development of cloud computing, increasing services have been 13 migrated from enterprise sites to clouds, so the connections between 14 sites and clouds are critical for enterprises. 16 SRv6 provides a sourcing routing mechanism to connect the enterprise 17 sites and clouds by programming the end-to-end path at the ingress 18 node. In this scenario, the SRv6 packets may traverse multiple 19 network domains and some of them may not be SRv6-capable. 21 In order to support SRv6 end-to-end path programming, this document 22 proposes the mechanism of SRv6 traversing IPv4 network. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at https://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on October 22, 2021. 41 Copyright Notice 43 Copyright (c) 2021 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (https://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 59 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 60 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 61 3. IPv4 Path Programming in SRv6 . . . . . . . . . . . . . . . . 3 62 3.1. End.B4 . . . . . . . . . . . . . . . . . . . . . . . . . 3 63 3.2. End.4 . . . . . . . . . . . . . . . . . . . . . . . . . . 4 64 3.2.1. IPv4 Tunnel Information Encapsulation . . . . . . . . 5 65 3.2.2. IPv4 Tunnel Information in SRH TLV . . . . . . . . . 6 66 4. Illustration . . . . . . . . . . . . . . . . . . . . . . . . 6 67 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 68 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 69 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 70 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 71 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 72 8.2. Informative References . . . . . . . . . . . . . . . . . 8 73 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 75 1. Introduction 77 When segment routing (SR) [RFC8402] is deployed on the IPv6 data 78 plane, it is called SRv6 [RFC8754]. For support of SR, a new routing 79 header called Segment Routing Header (SRH), which contains a list of 80 SIDs and other information, has been defined in [RFC8754]. 82 When deploying SRv6, the SRv6 network may need to interwork with 83 exiting networks, such as MPLS netwoks and IPv4 networks. 85 With the development of cloud computing, increasing services have 86 been migrated from enterprises to cloud data centers. Compared with 87 interconnections between branches and headquarters, new connections 88 between enterprise sites to cloud data centers and inter-cloud are 89 added, which bring new requirements and challenges for existing 90 networks. [I-D.li-rtgwg-ipv6-based-con] describes the requirements 91 and candidate technologies in IPv6-based Cloud-oriented Networking 92 (CON). In IPv6-based CON, SRv6 can be used to connect enterprise 93 sites and clouds. In this scenario, an SRv6 packet may be forwarded 94 traversing IPv4 domains. 96 The Tunnel Segment is defined in [I-D.li-spring-tunnel-segment] to 97 associate a tunnel to a segment in SRv6 and SR-MPLS, therefore, its 98 dataplane is IPv6 or MPLS. The document defines the a new types of 99 tunnel segment to associate an IPv4 tunnel to an SRv6 SID for 100 supporting end-to-end path programming traversing IPv4 domains. 101 Furthermore, this document also defines the mechanism of encoding the 102 IPv4 tunnel information in the SRH at the source node to provide 103 better source routing programming. 105 2. Terminology 107 This document makes use of the terms defined in [RFC8986], and the 108 reader is assumed to be familiar with that terminology. 110 2.1. Requirements Language 112 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 113 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 114 "OPTIONAL" in this document are to be interpreted as described in BCP 115 14 [RFC2119] [RFC8174] when, and only when, they appear in all 116 capitals, as shown here. 118 3. IPv4 Path Programming in SRv6 120 This document defines the following mechanisms for SRv6 traversing 121 IPv4 networks. 123 3.1. End.B4 125 This document defines a new End.B4 (End bound to an IPv4 tunnel) 126 behavior for an SRv6 SID bound to an IPv4 tunnel. 128 End.B4 SID MUST NOT be the last SID in the segment list. When the 129 node receives a packet with End.B4 SID, the packet is steered into 130 the bound IPv4 tunnel. 132 When node N receives a packet whose IPv6 DA is S and S is a local 133 End.B4 SID, the line S15 - S16 from the End processing [RFC8986] is 134 replaced by the following: 136 S15. Encapsulates the SRv6 packet with a new IPv4 tunnel 137 encapsulation bound to the End.B4 SID S. 138 S16. Submit the packet to the IPv4 module for transmission 140 S17. } 142 3.2. End.4 144 Another option is to carry the IPv4 tunnel information in the SRH. 145 The IPv4 tunnel information can be encoded in another 128-bit value 146 following the SID or SRH TLVs. 148 In this revision, this section defines an End.4 (End function with 149 IPv4 tunnel instantiation) behavior for an SRv6 SID to indicate a 150 128-bit IPv4 tunnel information is encoded following the SID. 152 An End.4 SID MUST be encoded preceding the IPv4 tunnel information 153 encapsulation, thus it can not be the last SID in the SID list. In 154 addition, the IPv6 address is needed to be updated by the next SRv6 155 SID, therefore the IPv4 tunnel information encapsulation MUST NOT be 156 the last SID as well. 158 The SRv6 path of crossing IPv4 domain is called IPv4 sub-path. An 159 IPv4 sub-path is encoded by an END.4 SID and the following IPv4 160 tunnel information encapsulation as shown in the following figure. 162 0 1 2 3 163 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 1 164 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 165 | IPv4 tunnel info | 166 | | 167 | | 168 | | 169 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 170 | SRv6 End.4 SID | 171 | | 172 | | 173 | | 174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 175 Figure 1. IPv4 Tunnel Sub-path Encoding in SRH 177 When encoding the end-to-end forwarding path, the ingress encodes the 178 End.4 SID and related IPv4 tunnel info into the SID list, the 179 encoding of IPv4 tunnel information is shown in section 3.2.1. 181 When a node processes an End.4 SID, it encapsulates the SRv6 packet 182 with an IPv4 tunnel header using the information carried by the IPv4 183 tunnel information, decreases the SL accordingly and then sends the 184 packet by looking up the IPv4 destination address in the IPv4 header. 186 When node N receives a packet whose IPv6 DA is S and S is a local 187 End.B4 SID, the line S02 from the End processing [RFC8986] is 188 replaced by the following: 190 S02. If (Segments Left == 0 or 1) 192 The lines S13-S16 are replaced by the following pseudo code. 194 S13. Decrement SL by 2 195 S14. Update IPv6 DA with Segment List[Segments Left] 196 S15. Encapsulates the SRv6 packet with a new IPv4 tunnel 197 by using the IPv4 tunnel information 198 S16. Submit the packet to the IPv4 module for transmission 199 S17. } 201 3.2.1. IPv4 Tunnel Information Encapsulation 203 An IPv4 Tunnel Information Encapsulation contains 128 bits IPv4 204 tunnel related information. The format is shown below. 206 0 1 2 3 207 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 1 208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 209 | Type | Tunnel Parameters | 210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 211 | IPv4 Src Address | 212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 213 | IPv4 Dest Address | 214 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 215 | Tunnel Parameters | 216 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 218 Figure 1. IPv4 Tunnel Information 220 3.2.1.1. IPv4 Tunnel Information Encoding 222 The IPv4 tunnel information includes tunnel type, source IPv4 223 address, destination IPv4 address and tunnel parameters. Different 224 types of IPv4 tunnels have specific parameters: 226 o IPv4 UDP tunnel: the tunnel parameters includes source port and 227 destination port. 229 o IPv4 VXLAN tunnel: the tunnel parameters includes source port, 230 destination port and VN ID. 232 The detailed encapsulation formats for different types of IPv4 tunnel 233 is out of scope of the document. 235 3.2.2. IPv4 Tunnel Information in SRH TLV 237 The IPv4 tunnel information MAY be carried in SRH TLV as well. 239 A TLV Carrying (TC) Flavor is defined to indicate the SID related 240 information is carried within the SRH TLV. 242 Therefore, an End.4(TC) SID indicates to read the IPv4 tunnel 243 information in the SRH TLV. 245 A mechanism of specifying which SRH TLV to be processed by which SID 246 in the SID list is defined in 247 [I-D.li-spring-srh-tlv-processing-programming], and it can be used 248 for indicating the node to processing IPv4 tunnel information in SRH 249 TLV. More details will be described in the future. 251 4. Illustration 253 For easy understanding, this section illustrates how to use End.4 SID 254 for SRv6 traversing IPv4 networks. 256 Assuming that 258 o A::1:200 is the End.4 SID for traversing an IPv4 domain. 260 o 192.168.0.1 is the source address of the IPv4 tunnel. 262 o 192.168.0.2 is the destination address of the IPv4 tunnel. 264 The programmed SRv6 path is shown in Figure 3: 266 0 1 2 3 267 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 1 268 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 269 | ... | 270 | | 271 | | 272 | | 273 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 274 | Type | Tunnel Parameters | 275 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 276 | 192.168.0.1 | 277 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 278 | 192.168.0.2 | 279 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 280 | Tunnel Parameters | 281 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 282 | A::1:200 (End.4) | 283 | | 284 | | 285 | | 286 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 287 | ... | 288 | | 289 | | 290 | | 291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 293 Figure 3. Illustration of using End.4 SID 295 When the node processes the End.4 SID A::1:200, it encapsulates a new 296 IPv4 header for the SRv6 packet, setting source IPv4 address as 297 192.168.0.1, and destination address as 192.168.0.2, and parameters 298 accordingly. Also, the inner IPv6 DA is updated by the next SID 299 following the IPv4 tunnel information. The node looks up the IPv4 300 destination address and forward the packet. 302 5. IANA Considerations 304 TBD 306 6. Security Considerations 308 TBD 310 7. Acknowledgements 312 8. References 314 8.1. Normative References 316 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 317 Requirement Levels", BCP 14, RFC 2119, 318 DOI 10.17487/RFC2119, March 1997, 319 . 321 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 322 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 323 May 2017, . 325 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 326 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 327 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 328 . 330 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 331 Decraene, B., Litkowski, S., and R. Shakir, "Segment 332 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 333 July 2018, . 335 [RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, 336 D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 337 (SRv6) Network Programming", RFC 8986, 338 DOI 10.17487/RFC8986, February 2021, 339 . 341 8.2. Informative References 343 [I-D.li-spring-srh-tlv-processing-programming] 344 Li, C., Xia, Y., Dhody, D., and Z. Li, "SRH TLV Processing 345 Programming", draft-li-spring-srh-tlv-processing- 346 programming-00 (work in progress), December 2020. 348 [I-D.li-rtgwg-ipv6-based-con] 349 (editor), C. L., Li, Z., and H. Yang, "IPv6-based Cloud- 350 Oriented Networking (CON)", draft-li-rtgwg-ipv6-based- 351 con-01 (work in progress), March 2021. 353 [I-D.li-spring-tunnel-segment] 354 Li, Z. and N. Wu, "Tunnel Segment in Segment Routing", 355 draft-li-spring-tunnel-segment-01 (work in progress), 356 March 2016. 358 Authors' Addresses 360 Zhenbin Li 361 Huawei Technologies 362 Huawei Campus, No. 156 Beiqing Rd. 363 Beijing 100095 364 China 366 Email: lizhenbin@huawei.com 368 Cheng Li 369 Huawei Technologies 370 Huawei Campus, No. 156 Beiqing Rd. 371 Beijing 100095 372 China 374 Email: c.l@huawei.com