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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 Network Working Group L. Dunbar 2 Internet Draft Huawei 3 Intended status: Informational Mehmet Toy 4 Expires: Aug 2019 Verizon 5 February 28, 2019 7 Segment routing for SD-WAN paths over hybrid networks 8 draft-dunbar-sr-sdwan-over-hybrid-networks-03 10 Abstract 12 This document describes a method for end-to-end (E2E) SD-WAN paths 13 to traverse specific list of network segments, some of which are 14 private networks which include SR enabled segments, some of which 15 may be the public IP networks that do not support SR, to achieve the 16 desired optimal E2E quality. 18 The method described in this draft uses the principle of segment 19 routing to enforce a SD-WAN path' head-end selected route traversing 20 through a list of specific nodes of multiple network segments 21 without requiring the nodes in each network segment to have the 22 intelligence (or maintaining states) of selecting next hop or next 23 domain. 25 Status of this Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. This document may not be modified, 32 and derivative works of it may not be created, except to publish it 33 as an RFC and to translate it into languages other than English. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF), its areas, and its working groups. Note that 37 other groups may also distribute working documents as Internet- 38 Drafts. 40 Internet-Drafts are draft documents valid for a maximum of six 41 months and may be updated, replaced, or obsoleted by other documents 42 at any time. It is inappropriate to use Internet-Drafts as 43 reference material or to cite them other than as "work in progress." 45 The list of current Internet-Drafts can be accessed at 46 http://www.ietf.org/ietf/1id-abstracts.txt 48 The list of Internet-Draft Shadow Directories can be accessed at 49 http://www.ietf.org/shadow.html 51 This Internet-Draft will expire on August 28, 2019. 53 Copyright Notice 55 Copyright (c) 2019 IETF Trust and the persons identified as the 56 document authors. All rights reserved. 58 This document is subject to BCP 78 and the IETF Trust's Legal 59 Provisions Relating to IETF Documents 60 (http://trustee.ietf.org/license-info) in effect on the date of 61 publication of this document. Please review these documents 62 carefully, as they describe your rights and restrictions with 63 respect to this document. Code Components extracted from this 64 document must include Simplified BSD License text as described in 65 Section 4.e of the Trust Legal Provisions and are provided without 66 warranty as described in the Simplified BSD License. 68 Table of Contents 70 1. Introduction...................................................3 71 2. Definition of terms............................................4 72 3. Key Use Cases..................................................5 73 3.1. SD-WAN Path over LTE network and SR Domain................5 74 3.2. SD-WAN As Last Mile for Cloud DCs Access..................6 75 3.3. How & Why SR is useful for those use cases................7 76 4. Mechanism for SD-WAN path over one SR Domain and existing access 77 ..................................................................8 78 4.1. Controller Delivers SID Stack to SD-WAN Head-end..........9 79 4.2. Using GRE Key or VXLAN ID to Differentiate Flows.........11 80 4.3. Using UDP Source Port Number to Differentiate Flows......12 81 4.4. GRE Header Extension.....................................15 82 5. SD-WAN path over multiple SP managed domains..................16 83 5.1. When Both SP domains support SR..........................17 84 5.2. When SP-2 does not support SR............................17 85 5.3. When SP-1 and SP-2 don't want to share network information18 86 5.4. TLV to pass Metadata through SRv6 Domain.................18 87 6. Security Considerations.......................................19 88 7. IANA Considerations...........................................20 89 8. References....................................................20 90 8.1. Normative References.....................................20 91 8.2. Informative References...................................20 92 9. Acknowledgments...............................................21 94 1. Introduction 96 This document describes a method to enforce a SD-WAN path's head-end 97 selected route traversing through a list of specific nodes of 98 multiple network segments without requiring the nodes in each 99 network segments to have the intelligence (or maintaining states) of 100 selecting next hop or next segments. Those networks over which the 101 SD-WAN path traverse have at least one SR enabled network, and some 102 network segments (especially the last mile access portion) being 103 existing IP networks (such as existing IPv4, IPv6 or others). 105 SD-WAN, as described by ONUG (Open Network User Group), is about 106 pooling WAN bandwidth from multiple service providers to get better 107 WAN bandwidth management, visibility & control. 109 Throughout this document, the term "Classic SD-WAN" refers to a pair 110 of CPEs in two locations aggregating N Service Providers' paths, 111 such as MPLS Paths and public internet paths. [SR-SD-WAN] describes 112 using explicit routes within the SRv6 or SR-MPLS enabled networks to 113 reach the desired quality for SD-WAN paths over the SRv6 or SR-MPLS 114 enabled networks respectively. 116 [SDWAN-Framework] describes three distinct SDWAN scenarios from edge 117 node's perspective: 119 1) All traffic are encrypted over WAN ports; allowing network 120 service providers to extend its existing VPN to reach sites to 121 which they do not have physical infrastructure yet. 123 2) Edge node has some ports connected to VPNs over which traffic 124 can go natively without encryption and other ports to the public 125 Internet over which traffic are encrypted; or 127 3) VPN PEs adding Internet facing WAN ports to offload low 128 priority traffic when the VPN backbone paths/links are congested. 130 This document focuses on the scenario 1) above, where a SD-WAN path 131 is over SR enabled networks and the other portion of the SD-WAN path 132 is over the public IP networks, such as existing IPv4, LTE, etc. 133 Under this scenario, the endpoints of the SD-WAN path (e.g. the CPE 134 devices, one or both) are not directly attached to PEs of a SR 135 domain. 137 The goal is to place a large portion of the SD-WAN path over a 138 provider VPN to reach more optimal transport quality or making the 139 SDWAN path traversing specific ingress/egress PEs for the optimal 140 cost, quality or other reasons. 142 2. Definition of terms 144 Cloud DC: Off-Premises Data Centers that usually host applications 145 and workload owned by different organizations or 146 tenants. 148 Controller: Used interchangeably with SD-WAN controller to manage 149 SD-WAN overlay path creation/deletion and monitoring the 150 path conditions between two or more sites. 152 DMVPN: Dynamic Multipoint Virtual Private Network. DMVPN is a 153 secure network that exchanges data between sites without 154 needing to pass traffic through an organization's 155 headquarter virtual private network (VPN) server or 156 router. 158 Heterogeneous Cloud: applications & workloads split among Cloud DCs 159 owned & managed by different Cloud Providers. 161 Hybrid Cloud: applications & workloads split between on-premises 162 Data centers and Cloud DCs. In this document Hybrid 163 Cloud also include heterogeneous cloud as well. 165 SD-WAN: Software Defined Wide Area Network, "SDWAN" refers to 166 the solutions of pooling WAN bandwidth from multiple 167 underlay networks to get better WAN bandwidth 168 management, visibility & control. When the underlay 169 networks are private, traffic can traverse without 170 additional encryption; when the underlay networks are 171 public, such as the Internet, some traffic needs to be 172 encrypted when traversing through (depending on user 173 provided policies). 175 SP: Network Service Provider 177 SR: Segment Routing 179 SR Domain: A domain that supports Segment Routing 181 VPC: Virtual Private Cloud. A service offered by many Cloud 182 DC operators to allocate a logically isolated cloud 183 resources, including computing, networking and storage. 185 3. Key Use Cases 187 3.1. SD-WAN Path over LTE network and SR Domain 189 MEF Cloud Service Architecture [MEF-Cloud] describes a use case of 190 network operators needing to use SD-WAN over LTE for the last mile 191 access that they do not have physical infrastructure, as shown 192 below: 194 +********SD-WAN Overlay Path *********+ 195 * * 196 * +------------+ * 197 * |SD-WAN Ctrl | * 198 * +===+------------+====+ * 199 * // \\ * 200 * // <-------VxLAN-------> \\ * 201 * +-+--+ +--+ +--+ +--+-+ * 202 ***+ E1 |==|C1| |C4+==+ E2 |****+ 203 A --+ | | | | | | +----Z 204 A2--+--||+ ++-+ ++-+ ++---+\---Z2 205 LTE || | | // 206 || | SR +-+---+ +----+ 207 || | Network | C6 | |E3 | 208 || | | |----| | 209 +===+-----+ +-+---+ +----+ 210 + C3 |-------+ 211 +---+-+ 212 | 213 +---+-+ 214 | E4 | 215 +-----+ 216 -- Directly attached 217 == || Public Internet or LTE path 218 *** Overlay path 220 Figure 1: SD-WAN end points are attached to VPN via LTE 222 3.2. SD-WAN As Last Mile for Cloud DCs Access 224 Digital Transformation is propelling more and more enterprises to 225 move their workloads/Apps to cloud DCs that are geographically close 226 to their end users to improve end-to-end latency & overall user 227 experience, or to comply with local data protection regulations. 228 Conversely, workloads/Apps in those Cloud DCs can be easily shutdown 229 when their end users' geographic base changes. 231 Because of the ephemeral property of the selected Cloud DCs, an 232 enterprise or its network service provider may not have the direct 233 links to the Cloud DCs that are optimal for hosting the enterprise's 234 specific workloads/Apps. Under those circumstances, SD-WAN is a very 235 flexible choice to interconnect the enterprise on-premises data 236 centers & branch offices to its desired Cloud DCs. 238 However, SD-WAN paths over public internet can have unpredictable 239 performance, especially over long distances and cross state/country 240 boundaries. Therefore, it is highly desirable to place as much as 241 possible the portion of SD-WAN paths over service provider VPN (e.g. 242 enterprise's existing VPN) that have guaranteed SLA to minimize the 243 distance/segments over public internet. 245 Under this scenario, one or both of the SD-WAN end points may not 246 directly attached to the PEs of a SR Domain. 248 3.3. How & Why SR is useful for those use cases 250 Let us assume that the SD-WAN Controller is capable of computing 251 optimal paths between two end-points (e.g. E1<->E2 in the Figure 2), 252 either by communicating with the SR Domain controller/management- 253 system, or by other methods which is out of the scope of this 254 document. 256 The SR domain must have a set of PEs that have at least one port 257 facing the external networks (such as the public internet or LTE 258 termination). 260 Under this circumstance, SD-WAN end-points usually can reach 261 multiple PEs. 263 In the diagram below, E1 <-> E2 SD-WAN (most likely IPsec encrypted 264 tunnel) path can traverse C1 <-> C4, C1<->C6, C3<->C6, or C3<->C4 265 within the VPN. There are many flows (by different Apps) between E1 266 <-> E2. Some flows may need to traverse C1<->C4, others may need to 267 traverse C3<->C6 or other segments within the VPN, which are 268 determined by the SD-WAN controller based on the characteristics & 269 need of the Apps, such as cost, available bandwidth, latency, or 270 special functions only available at specific locations, etc. 272 Even with the same ingress/egress, some flows may need different 273 segments across the SR Domain. It is not practical, or even 274 possible, for PEs (e.g. C1, C2, C3 in this example) to determine 275 which Apps' flows should egress C4 or C6 where both C4&C6 can reach 276 E2. 278 Segment Routing can be used to force the path to traverse the 279 explicit egress node (C4 or C6), or explicit segments through the SR 280 Domain based on the SLA requested by the SD-WAN head-end nodes. 282 +********SD-WAN Overlay Path *********+ 283 * * 284 * +------------+ * 285 * |SD-WAN Ctrl | * 286 * +===+------------+====+ * 287 * // \\ * 288 * // <----- -VxLAN-------> \\ * 289 * +-+--+ ++-+ ++-+ +--+-+ * 290 ***+ E1 |==|C1| |C4+==+ E2 |****+ 291 A --+ | | | | | | +----Z 292 A2--+----+ ++-+ ++-+ ++---+\---Z2 293 LTE || | | // 294 || | SR +-+---+ +----+ 295 || | Network | C6 | |E3 | 296 || | | |- --| | 297 || +-----+ +-+---+ +----+ 298 +====+ C3 |-----+ 299 +-+---+ 300 | 301 +---+-+ 302 | E4 | 303 +-----+ 305 -- Directly attached 306 == || Public Internet or LTE path 307 ** Overlay path 309 Figure 2: SDWAN end points not directly attached to PEs of SR Domain 311 4. Mechanism for SD-WAN path over one SR Domain and existing access 313 This section describes the mechanism to enforce a SD-WAN path' head- 314 end selected route traversing through a list of specific nodes of 315 multiple network segments without requiring the nodes in each 316 network segment to have the intelligence (or maintaining states) of 317 selecting next hop or next domain. 319 There may be two approaches here: 321 1) Controller installs the entire SID stack at E1. 322 2) Controller delivers to E1 a "Key" that the SR ingress PE can use 323 to map to the SID stack for the packets arriving at the SR Ingress 324 PE. Section 4.2 & 4.3 will describe how the "Key" is carried by the 325 packets. 327 The Approach 1) requires less processing at the SR Ingress PE nodes, 328 but only works if the remote CPEs are in the same Administrative 329 domain as the SR domain. SR domain usually is not willing to expose 330 its internal binding SIDs to devices in different administration 331 domains. This approach also requires more changes to SD-WAN end 332 nodes and need more header bytes added to the packets when rd traversing through 3 party internet. Some SD-WAN nodes might not be 333 capable of supporting encapsulating packets with the SID stack. 335 The Approach 2) above requires SR Ingress PE nodes to map the "Key" 336 to the SID Stack and prepend the SID stack to the packets (Same 337 processing for other traffic except the mapping is from the received 338 "Key" carried in the payload). 340 4.1. Controller Delivers SID Stack to SD-WAN Head-end 342 This approach is straightforward. 344 E1 -------------------------- > SD-WAN controller 345 request for a SD-WAN path E1<->E2 with a specific SLA 347 E1 <-------------------------- SD-WAN controller 348 Reply with the Ingress PE Node ID or address 349 & the Binding SID. 351 Here is the packet header for SD-WAN Source Node to prepend to the 352 payload: 354 0 1 2 3 355 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 1 357 IPv4 Header: 358 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 359 |Version| IHL |Type of Service| Total Length | 360 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 361 | Identification |Flags| Fragment Offset | 362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 363 | Time to Live | Prot.=17(UDP) | Header Checksum | 364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 365 | SD-WAN Source IPv4 Address | 366 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 367 | SR Ingress PE IPv4 Address | 368 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 370 UDP Header: 371 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 372 | Source Port = | Dest. Port = 4754/4755 | 373 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 374 | UDP Length | UDP Checksum | 375 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 377 GRE Header: 378 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 379 |C| |K|S| Reserved0 | Ver | Protocol Type | 380 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 381 | Checksum (optional) | Reserved1 (Optional) | 382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 383 | Key (For SR Ingress to map to its SID) | 384 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 385 | Sequence Number (optional) | 386 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 388 To traverse SRv6 domain, SRv6 Header is appended after the GRE 389 header [SRv6-SRH]: 391 To traverse MPLS-SR domain, a stack of MPLS labels is appended after 392 GRE Header [MPLS-SR]. 394 4.2. Using GRE Key or VXLAN ID to Differentiate Flows 396 This section describes a method of SD-WAN head-end node using GRE 397 Key or VXLAN Network ID (VNI) to indicate the desired property for 398 specific flows between SD-WAN end-points (E1<->E2 in the figure 399 above): such as different desired routes through the SR Domain, 400 different egress PEs based on cost, performance or other factors. 401 It might be difficult or impossible to DiffServ bits carried by the 402 packets to describe those flow properties. 404 The SR Domain ingress can map the GRE key to different SID through 405 the SR Domain. 407 We assume that the SD-WAN Controller can determine which ingress PE 408 can lead to the optimal path between E1<->E2. It is beyond the scope 409 of this document on how SD-WAN controller computes the paths and how 410 & what SD-WAN controller communicates with the SR Domain controller. 412 Here is the sequence of the flow: 414 E1 -------------------------- > SD-WAN controller 415 request for a SD-WAN path E1<->E2 with a specific SLA 417 E1 <-------------------------- SD-WAN controller 418 Reply with the Ingress PE Node ID or address 419 & (the GRE Key or VXLAN ID). 421 Note: the GRE key (or VXLAN ID) from the SD-WAN controller is for 422 the ingress PEs to correlate desired Path with the list of SIDs to 423 prepend the packet across the SR domain. 425 When SD-WAN Controller get the E1<->E2 path request, it will 426 communicate with the VPN Controller to get the optimal Ingress PE 427 Node ID (or IP address) and the GRE key (or VXLAN ID) to encapsulate 428 the original packets between E1 <-> E2 (assuming IPsec Tunnel mode 429 is used). 431 Upon receiving the GRE encapsulated packets, the provider ingress 432 Edge C1/C3 uses the GRE key (or VXLAN ID) to map to the pre-defined 433 (by the network controller) Binding SIDs, prepend the Binding SIDs 434 to the packets, and forward its desired paths across the provider 435 VPN. 437 Depending on how the SD-WAN path destination can be reached by the 438 egress PE, the egress PE has different processing procedure: 440 - If the destination of the SD-WAN path is directly attached to 441 the egress VPN PE node, the egress VPN PE decapsulates SR 442 header and forward the packets to SD-WAN path destination node, 443 such as the E2 in the figure above. 444 - If the destination of the SD-WAN path is IP reachable via IPv4 445 network from the egress VPN PE node, the egress VPN PE node 446 decapsulates SR header and forward the packets to SD-WAN path 447 destination node via its internet facing port to the SD-WAN 448 path destination (i.e. the E2 node in the figure above). 449 - If the SD-WAN path is traversing multiple domains owned by 450 different network operators, the egress PE processing is 451 described in the next session. 453 4.3. Using UDP Source Port Number to Differentiate Flows 455 [RFC8086] describes how to use GRE-in-UDP source port number as 456 entropy for better ECMP performance. When the remotely attached CPEs 457 is within very close proximity to the PEs, e.g. only one or two 458 hopes away like in LTE access, there is less issue if ECMP put all 459 flows with same traffic classifier into one path. Then, those UDP 460 numbers can also be used as a key to SR PE nodes to map to the 461 appropriate SID to the packets. 463 Same as RFC8086, UDP source port values used as a key for SR PEs to 464 map to appropriate SIDs SHOULD be chosen from the ephemeral port 465 range (49152-65535) [RFC8085]. 467 The GRE-in-UDP encapsulation format contains a UDP header [RFC768] 468 and a GRE header [RFC2890]. The format is shown as follow 469 (presented in bit order): 471 0 1 2 3 472 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 1 474 IPv4 Header: 475 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 476 |Version| IHL |Type of Service| Total Length | 477 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 478 | Identification |Flags| Fragment Offset | 479 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 480 | Time to Live | Prot.=17(UDP) | Header Checksum | 481 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 482 | SD-WAN Source IPv4 Address | 483 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 484 | SR Ingress PE IPv4 Address | 485 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 487 UDP Header: 488 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 489 | Source Port = SIDs key Value | Dest. Port = 4754/4755 | 490 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 491 | UDP Length | UDP Checksum | 492 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 494 GRE Header: 495 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 496 |C| |K|S| Reserved0 | Ver | Protocol Type | 497 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 498 | Checksum (optional) | Reserved1 (Optional) | 499 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 500 | Key (optional) | 501 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 502 | Sequence Number (optional) | 503 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 505 Figure 3: UDP + GRE Headers in IPv4 507 Here is the GRE Header for IPv6 network, i.e. the SD-WAN Source SD- 508 WAN Destination, and SR PEs are all in IPv6 domain: 510 0 1 2 3 511 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 1 513 IPv6 Header: 514 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 515 |Version| Traffic Class | Flow Label | 516 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 517 | Payload Length | NxtHdr=17(UDP)| Hop Limit | 518 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 519 | | 520 + + 521 | | 522 + SD-WAN Source IPv6 Address + 523 | | 524 + + 525 | | 526 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 527 | | 528 + + 529 | | 530 + SR Domain Ingress PE IPv6 Address + 531 | | 532 + + 533 | | 534 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 536 UDP Header: 537 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 538 | Source Port = SIDs key value | Dest. Port = 4754/4755 | 539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 540 | UDP Length | UDP Checksum | 541 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 543 GRE Header: 544 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 545 |C| |K|S| Reserved0 | Ver | Protocol Type | 546 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 547 | Checksum (optional) | Reserved1 (Optional) | 548 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 549 | Key (optional) | 550 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 551 | Sequence Number (optional) | 552 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 554 Figure 4: GRE+UDP for IPv6 556 4.4. GRE Header Extension 558 A new protocol type can be added to the GRE header [RFC2890] to make 559 it easier for the SR PE to do the proper actions: 561 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 1 562 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 563 |C| Reserved0 | Ver | Protocol Type | 564 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 565 | Checksum (optional) | Reserved1 (Optional) | 566 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 568 The proposed GRE header will have the following format: 570 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 1 571 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 572 |C| |K|S| Reserved0 | Ver | Protocol Type | 573 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 574 | Checksum (optional) | Reserved1 (Optional) | 575 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 576 | Key (optional) | 577 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 578 | Sequence Number (Optional) | 579 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 581 New protocol type (value to be assigned by IANA): 582 UDP-Key: Using UDP source port value as a Key for SR Ingress PE to 583 map to the appropriate SIDs. 585 GRE-KEY: Using GRE Key value as a key for SR ingress PE to map to 586 the appropriate SIDs 588 5. SD-WAN path over multiple SP managed domains 589 The following figure shows a SD-WAN Path E1<->E2 over two SP domains 590 which are interconnected by public internet. 592 +********SD-WAN Overlay Path *************+ 593 * * 594 * +------------+ * 595 * |SD-WAN Ctrl | * 596 * +===+------------+====E2/E3/E4.. * 597 * // * 598 * // <-----EVPN-VxLAN----> * 599 * +-+--+ ++-+ ++-+ +--+-+ * 600 ***+ E1 |==|C1| |C7+--+ E7 | * 601 A --+ | | | | | | + * 602 A2--+----+ ++-+ ++-+ ++---+ * 603 LTE || | SP1 | // * 604 +---+ SR +-+---+ +----+ * 605 +--------+ |C3 | Network | C4 | |E3 | * 606 | E4 | | | | |- --| | * 607 | | +---+-----+---+---+-+ +----+ * 608 +--------+=======+ C2 | || * 609 +---+-+ // * 610 // // * 611 +-+-+--------+--+-+ * 612 |D1 | |D4 | * 613 | | | | * 614 ++--+ ++---+ * 615 | SP2 | * 616 | SR +--+--+ +-+--+ 617 +--------+ | Network | D2 | |E2 +----Z 618 | E6 | | | +====+ +---Z2 619 | | +--+-----+ +-+---+LTE +----+ 620 +-+--+-+-+-------+ D3 |-----+ 621 +---+-+ 623 -- Directly attached 624 == || Public Internet or LTE path 625 ** Overlay path 626 Figure 5: SD-WAN path over two different SP domains 628 Let's assume that the SP-1 domain's egress node for the SD-WAN path 629 E1<->E2 is C2, which can reach D1 or D4 of SP-2 via public IP 630 network (say IPv4 network). 632 Let's also assume that the optimal route for some flows over SD-WAN 633 path E1<->E2 are C1->C2->D1 and other flows are over C1->C2->D4 (out 634 of the scope of this document on how the path is calculated). 636 If SP-1 is SR enabled, the mechanism described in Section 4 is 637 applicable to the SD-WAN path source node E1 and the SP-1's ingress 638 PE (e.g. C1 or C3 in the figure). 639 However, the processing at egress node might be different depending 640 on how the SP-1's egress edges are connected to the SP-2's ingress 641 edge nodes. 643 5.1. When Both SP domains support SR 645 There may be three approaches here: 647 1) Controller installs the entire SID stack at E1, and the SID list 648 contains SID entries belong to both domains. 650 2) Controller delivers to E1 the SID stack that only for the first 651 domain, but delivers to C6 (egress node of first domain) the binding 652 SID of the second domain. 654 3) Controller delivers a "Key" to E1, which can be encoded as GRE 655 KEY or represented by the Source UDP port of the GRE encapsulation, 656 for Ingress PE of the first SR Domain to map to its own SID stack as 657 described in Section 4. The first SR Domain will reserve the "Key" 658 through its domain and pass the "Key" to the second SR domain. The 659 second SR Domain Ingress node will use the same method to map the 660 "Key" to its SID stack. 662 5.2. When SP-2 does not support SR 664 Under this circumstance (which can be caused by SP-2 not supporting 665 SR or not willing to share Binding SIDs to SP-1), if the packets 666 arriving at SP-1 egress node C6 do not have any metadata indicating 667 the types of encrypted payload, C6 does not really have much choice 668 other than simply forwarding the packets to E2 via public IP 669 network. This way, the packets may or may not traverse through the 670 SP-2 domain. If the distance between C6 and E2 is far, the quality 671 of service can be unpredictable. 673 5.3. When SP-1 and SP-2 don't want to share network information 675 If SP-1's ingress node C1 can include the GRE KEY it receives from 676 E1 in the data packets' SR header, the SP-1's egress node can map 677 the Key to the SP-2's Ingress node and encapsulate the data packet 678 in a new GRE header destined towards the SP-2's Ingress node. Then 679 the SP-2's Ingress node can follow the procedure described in the 680 Section 4 to forward the data packets across its domain. 682 If the first SR Domain does not support adding metadata to carry the 683 "key" through its domain, the controller can deliver the "key" to 684 SP-1's egress node the same time as it delivers the key to E1, 685 knowing the SD-WAN path will need to traverse two domains with the 686 second one does support SR but the two SPs don't want to exchange 687 network information. 689 5.4. TLV to pass Metadata through SRv6 Domain 691 If SP-1 is SRv6 based, the ingress node C1 can append a TLV to the 692 end of the SR Header [SRv6-SRH] to carry the KEY it receives from 693 E1. 695 The SP-1 egress node C6 can get the mapping between the KEYs and the 696 Node-IDs (or Addresses) of the next domain's ingress edge node (i.e. 697 D1 or D4 in the figure 3 above) from its network controller ahead of 698 time. 700 0 1 2 3 701 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 1 702 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 703 | Type | Length | RESERVED | 704 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 705 | Key ID (4 octets) from the GRE tunnel remote ingress node | 706 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 707 | Optional // 708 | Node ID or address for the ingress node Next domain // 709 | Variable length (0~32 octets) // 710 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 712 TYPE: (to be assigned by IANA) is to indicate the TLV is for 713 carrying the flow identifier of the packet encoded by the SD-WAN 714 source node. 716 Upon receiving the packet, the egress node (C6) can 718 - find the Node-ID (or the address) for the next domain's ingress 719 node, 720 - construct a GRE header with the Key received from the TLV above 721 and the destination address from the mapping given by the 722 controller, 723 - encapsulate the GRE header to the data packet (which has 724 decapsulated SR header), 725 - and forward the packet to the public internet. 727 6. Security Considerations 729 Remotely attached CPEs might brought the following security risks: 731 1) Potential DDoS attack to the PEs with ports facing internet. 732 I.e. the PE resource being attacked by unwanted traffic. 733 2) Potential risk of provider VPN network bandwidth being stolen 734 by the entities who spoofed the addresses of SD-WAN end nodes. 736 To mitigate security risk of 1) above, it is absolutely necessary 737 for PEs which accept remotely attached CPEs or simply have ports 738 facing internet to enable Anti-DDoS feature to prevent major DDoS 739 attack to those PEs. 741 To mitigate the security risk of 2) above, RFC7510 defines the use 742 of DTLS to authenticate and encrypt the RFC7510 encapsulation. 744 However, for the scenario of SD-WAN source node being remotely 745 attached to PEs, using the method recommended by RFC7510 means the 746 source node has to perform DTLS on top of the IPSec encryption 747 between SD-WAN end points E1<->E2. This can be too processing heavy 748 for the SD-WAN end nodes. In addition, if there are many SD-WAN 749 flows to traverse through the ingress PE (e.g. C1, C2, C4 in the 750 figure 1 above), heavy processing is required on the ingress PEs. 752 Since the payload between E2<->E2 is already encrypted, the 753 confidentiality of the payload is already ensured. The network 754 operators need to balance between how much they can tolerant some 755 percentage of bandwidth being stolen and how much extra cost they 756 are willing to pay for completely prevent any unpaid traffic 757 traversing through its VPN networks. For operators who opt for lower 758 cost ingress PEs and CPEs, but can tolerant some percentage of 759 bandwidth being used by unpaid subscribers, a simple approach can be 760 considered: 762 - Embed a key in the packets, which can be changed periodically, 763 like the digital signature used by a certificate authority or 764 certification authority (CA). 765 - The key can be encoded in the GRE Key field between SD-WAN end 766 node and Ingress PE. Since GRE has 24 bits, some fixed bits 767 can be used to represent the signature of paid subscribers. 769 7. IANA Considerations 771 This document requires new protocol type: 773 Protocol type to be added to GRE header: SR_Route 775 8. References 777 8.1. Normative References 778 [RFC2890] G. Dommety "Key and Sequence Number Extensions to GRE". 779 Sep. 2000. 781 8.2. Informative References 783 [RFC2735] B. Fox, et al "NHRP Support for Virtual Private 784 networks". Dec. 1999. 786 [RFC8192] S. Hares, et al "Interface to Network Security Functions 787 (I2NSF) Problem Statement and Use Cases", July 2017 789 [ITU-T-X1036] ITU-T Recommendation X.1036, "Framework for creation, 790 storage, distribution and enforcement of policies for 791 network security", Nov 2007. 793 [RFC6071] S. Frankel and S. Krishnan, "IP Security (IPsec) and 794 Internet Key Exchange (IKE) Document Roadmap", Feb 2011. 796 [RFC4364] E. Rosen and Y. Rekhter, "BGP/MPLS IP Virtual Private 797 Networks (VPNs)", Feb 2006 799 [RFC4664] L. Andersson and E. Rosen, "Framework for Layer 2 Virtual 800 Private Networks (L2VPNs)", Sept 2006. 802 [SR-SD-WAN] D. Dukes, et al, "SR for SDWAN: VPN with Underlay SLA", 803 draft-dukes-sr-for-sdwan-00, in progress, Oct 2017 805 [SRv6-SRH] S. Previdi, et al, "IPv6 Segment Routing Header (SRH)", 806 draft-ietf-6man-segment-routing-header-13, in progress, 807 April 2018. 809 [MPLS-SR] A. Bashandy, et al, "Segment Routing with MPLS data 810 plane", draft-ietf-spring-segment-routing-mpls-13, in 811 progress, April 2018. 813 [RFC7510] X. Xu, et al, "Encapsulating MPLS in UDP", April 2015. 815 [RFC8086] L. Yong, et al, "GRE-in-UDP Encapsulation", March 2017. 817 [MEF-Cloud] "Cloud Services Architecture Technical Specification", 818 Work in progress, April 2018 820 9. Acknowledgments 822 Many thanks to Dean Cheng and Jim Guichard for the discussion and 823 contributions. 825 Authors' Addresses 827 Linda Dunbar 828 Huawei 829 Email: Linda.Dunbar@huawei.com 831 Mehmet Toy 832 Verizon 833 One Verizon Way 834 Basking Ridge, NJ 07920 835 Email: mehmet.toy@verizon.com