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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Downref: Normative reference to an Informational RFC: RFC 8811 -- Obsolete informational reference (is this intentional?): RFC 8782 (Obsoleted by RFC 9132) Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group M. Boucadair 3 Internet-Draft Orange 4 Intended status: Standards Track T. Reddy 5 Expires: November 26, 2021 McAfee 6 W. Pan 7 Huawei Technologies 8 May 25, 2021 10 Multi-homing Deployment Considerations for Distributed-Denial-of-Service 11 Open Threat Signaling (DOTS) 12 draft-ietf-dots-multihoming-06 14 Abstract 16 This document discusses multi-homing considerations for Distributed- 17 Denial-of-Service Open Threat Signaling (DOTS). The goal is to 18 provide some guidance for DOTS clients/gateways when multihomed. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at https://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on November 26, 2021. 37 Copyright Notice 39 Copyright (c) 2021 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (https://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 4 56 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 57 4. Multi-Homing Scenarios . . . . . . . . . . . . . . . . . . . 4 58 4.1. Residential Single CPE . . . . . . . . . . . . . . . . . 5 59 4.2. Multi-Homed Enterprise: Single CPE, Multiple Upstream 60 ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 5 61 4.3. Multi-homed Enterprise: Multiple CPEs, Multiple Upstream 62 ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 6 63 4.4. Multi-homed Enterprise with the Same ISP . . . . . . . . 7 64 5. DOTS Multi-homing Deployment Considerations . . . . . . . . . 7 65 5.1. Residential CPE . . . . . . . . . . . . . . . . . . . . . 8 66 5.2. Multi-Homed Enterprise: Single CPE, Multiple Upstream 67 ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 9 68 5.3. Multi-Homed Enterprise: Multiple CPEs, Multiple Upstream 69 ISPs . . . . . . . . . . . . . . . . . . . . . . . . . . 12 70 5.4. Multi-Homed Enterprise: Single ISP . . . . . . . . . . . 13 71 6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 72 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 73 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 74 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 75 9.1. Normative References . . . . . . . . . . . . . . . . . . 14 76 9.2. Informative References . . . . . . . . . . . . . . . . . 14 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 79 1. Introduction 81 In many deployments, it may not be possible for a network to 82 determine the cause of a distributed Denial-of-Service (DoS) attack 83 [RFC4732]. Rather, the network may just realize that some resources 84 seem to be under attack. To improve such situation, the IETF is 85 specifying the DDoS Open Threat Signaling (DOTS) architecture 86 [RFC8811], where a DOTS client can inform a DOTS server that the 87 network is under a potential attack and that appropriate mitigation 88 actions are required. Indeed, because the lack of a common method to 89 coordinate a real-time response among involved actors and network 90 domains jeopardizes the efficiency of DDoS attack mitigation actions, 91 the DOTS protocol is meant to carry requests for DDoS attack 92 mitigation, thereby reducing the impact of an attack and leading to 93 more efficient responsive actions. [I-D.ietf-dots-use-cases] 94 identifies a set of scenarios for DOTS; most of these scenarios 95 involve a Customer Premises Equipment (CPE). 97 The high-level base DOTS architecture is illustrated in Figure 1 98 ([RFC8811]): 100 +-----------+ +-------------+ 101 | Mitigator | ~~~~~~~~~~ | DOTS Server | 102 +-----------+ +-------------+ 103 | 104 | 105 | 106 +---------------+ +-------------+ 107 | Attack Target | ~~~~~~ | DOTS Client | 108 +---------------+ +-------------+ 110 Figure 1: Basic DOTS Architecture 112 [RFC8811] specifies that the DOTS client may be provided with a list 113 of DOTS servers; each of these servers is associated with one or more 114 IP addresses. These addresses may or may not be of the same address 115 family. The DOTS client establishes one or more DOTS sessions by 116 connecting to the provided DOTS server(s) addresses (e.g., 117 [RFC8973]). 119 DOTS may be deployed within networks that are connected to one single 120 upstream provider. It can also be enabled within networks that are 121 multi-homed. The reader may refer to [RFC3582] for an overview of 122 multi-homing goals and motivations. This document discusses DOTS 123 multi-homing considerations. Specifically, the document aims to: 125 1. Complete the base DOTS architecture with multi-homing specifics. 126 Those specifics need to be taken into account because: 128 * Send a DOTS mitigation request to an arbitrary DOTS server 129 won't help mitigating a DDoS attack. 131 * Blindly forking all DOTS mitigation requests among all 132 available DOTS servers is suboptimal. 134 * Sequentially contacting DOTS servers may increase the delay 135 before a mitigation plan is enforced. 137 2. Identify DOTS deployment schemes in a multi-homing context, where 138 DOTS services can be offered by all or a subset of upstream 139 providers. 141 3. Sketch guidelines and recommendations for placing DOTS requests 142 in multi-homed networks, e.g.,: 144 * Select the appropriate DOTS server(s). 146 * Identify cases where anycast is not recommended. 148 This document adopts the following methodology: 150 o Identify and extract viable deployment candidates from 151 [I-D.ietf-dots-use-cases]. 153 o Augment the description with multi-homing technicalities, e.g., 155 * One vs. multiple upstream network providers 157 * One vs. multiple interconnect routers 159 * Provider-Independent (PI) vs. Provider-Aggregatable (PA) IP 160 addresses 162 o Describe the recommended behavior of DOTS clients and gateways for 163 each case. 165 Multi-homed DOTS agents are assumed to make use of the protocols 166 defined in [RFC8782] and [RFC8783]; no specific extension is required 167 to the base DOTS protocols for deploying DOTS in a multi-homed 168 context. 170 2. Requirements Language 172 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 173 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 174 "OPTIONAL" in this document are to be interpreted as described in BCP 175 14 [RFC2119][RFC8174] when, and only when, they appear in all 176 capitals, as shown here. 178 3. Terminology 180 This document makes use of the terms defined in [RFC8811] and 181 [RFC4116]. 183 IP indifferently refers to IPv4 or IPv6. 185 4. Multi-Homing Scenarios 187 This section describes some multi-homing scenarios that are relevant 188 to DOTS. In the following subsections, only the connections of 189 border routers are shown; internal network topologies are not 190 elaborated. 192 This section distinguishes between residential CPEs vs. enterprise 193 CPEs because PI addresses may be used for enterprises while this is 194 not the current practice for residential CPEs. 196 4.1. Residential Single CPE 198 The scenario shown in Figure 2 is characterized as follows: 200 o The home network is connected to the Internet using one single 201 CPE. 203 o The CPE is connected to multiple provisioning domains (i.e., both 204 fixed and mobile networks). Provisioning domain (PvD) is 205 explained in [RFC7556]. 207 o Each of these provisioning domains assigns IP addresses/prefixes 208 to the CPE and provides additional configuration information such 209 as a list of DNS servers, DNS suffixes associated with the 210 network, default gateway address, and DOTS server's name 211 [RFC8973]. These addresses/prefixes are assumed to be Provider- 212 Aggregatable (PA). 214 o Because of ingress filtering, packets forwarded by the CPE towards 215 a given provisioning domain must be sent with a source IP address 216 that was assigned by that domain [RFC8043]. 218 +-------+ +-------+ 219 |Fixed | |Mobile | 220 |Network| |Network| 221 +---+---+ +---+---+ 222 | | Service Providers 223 ............|....................|....................... 224 +---------++---------+ Home Network 225 || 226 +--++-+ 227 | CPE | 228 +-----+ 229 ... (Internal Network) 231 Figure 2: Typical Multi-homed Residential CPE 233 4.2. Multi-Homed Enterprise: Single CPE, Multiple Upstream ISPs 235 The scenario shown in Figure 3 is characterized as follows: 237 o The enterprise network is connected to the Internet using one 238 single router. 240 o That router is connected to multiple provisioning domains (i.e., 241 managed by distinct administrative entities). 243 Unlike the previous scenario, two sub-cases can be considered for an 244 enterprise network with regards to assigned addresses: 246 1. PI addresses/prefixes: The enterprise is the owner of the IP 247 addresses/prefixes; the same address/prefix is then used when 248 establishing communications over any of the provisioning domains. 250 2. PA addresses/prefixes: Each of the provisioning domains assigns 251 IP addresses/prefixes to the enterprise network. 253 +------+ +------+ 254 | ISP1 | | ISP2 | 255 +---+--+ +--+---+ 256 | | Service Providers 257 ............|....................|....................... 258 +---------++---------+ Enterprise Network 259 || 260 +--++-+ 261 | rtr | 262 +-----+ 263 ... (Internal Network) 265 Figure 3: Multi-homed Enterprise Network (Single CPE connected to 266 Multiple Networks) 268 4.3. Multi-homed Enterprise: Multiple CPEs, Multiple Upstream ISPs 270 This scenario is similar to the one described in Section 4.2; the 271 main difference is that dedicated routers are used to connect to each 272 provisioning domain. 274 +------+ +------+ 275 | ISP1 | | ISP2 | 276 +---+--+ +--+---+ 277 | | Service Providers 278 ......................|..........|....................... 279 | | Enterprise Network 280 +---+--+ +--+---+ 281 | rtr1 | | rtr2 | 282 +------+ +------+ 284 ... (Internal Network) 286 Figure 4: Multi-homed Enterprise Network (Multiple CPEs, Multiple 287 ISPs) 289 4.4. Multi-homed Enterprise with the Same ISP 291 This scenario is a variant of Section 4.2 and Section 4.3 in which 292 multi-homing is supported by the same ISP (i.e., same provisioning 293 domain). 295 5. DOTS Multi-homing Deployment Considerations 297 Table 1 provides some sample, non-exhaustive, deployment schemes to 298 illustrate how DOTS agents may be deployed for each of the scenarios 299 introduced in Section 4. 301 +---------------------------+-------------------------+-------------+ 302 | Scenario | DOTS client | DOTS | 303 | | | gateway | 304 +---------------------------+-------------------------+-------------+ 305 | Residential CPE | CPE | N/A | 306 +---------------------------+-------------------------+-------------+ 307 | Single CPE, Multiple | internal hosts or CPE | CPE | 308 | provisioning domains | | | 309 +---------------------------+-------------------------+-------------+ 310 | Multiple CPEs, Multiple | internal hosts or all | CPEs (rtr1 | 311 | provisioning domains | CPEs (rtr1 and rtr2) | and rtr2) | 312 +---------------------------+-------------------------+-------------+ 313 | Multi-homed enterprise, | internal hosts or all | CPEs (rtr1 | 314 | Single provisioning | CPEs (rtr1 and rtr2) | and rtr2) | 315 | domain | | | 316 +---------------------------+-------------------------+-------------+ 318 Table 1: Sample Deployment Cases 320 These deployment schemes are further discussed in the following 321 subsections. 323 5.1. Residential CPE 325 Figure 5 depicts DOTS sessions that need to be established between a 326 DOTS client (C) and two DOTS servers (S1, S2) within the context of 327 the scenario described in Section 4.1. 329 For each provisioning domain, the DOTS client MUST resolve the DOTS 330 server's name provided by a provisioning domain ([RFC8973]) using the 331 DNS servers learned from the respective provisioning domain. 332 IPv6-capable DOTS clients MUST use the source address selection 333 algorithm defined in [RFC6724] to select the candidate source 334 addresses to contact each of these DOTS servers. DOTS sessions MUST 335 be established and maintained with each of the DOTS servers because 336 the mitigation scope of these servers is restricted. The DOTS client 337 SHOULD use the certificate provisioned by a provisioning domain to 338 authenticate itself to the DOTS server(s) provided by the same 339 provisioning domain. 341 When conveying a mitigation request to protect the attack target(s), 342 the DOTS client among the DOTS servers available MUST select a DOTS 343 server whose network has assigned the IP prefixes from which target 344 IP prefixes/addresses are derived. This implies that if no 345 appropriate DOTS server is found, the DOTS client MUST NOT send the 346 mitigation request to any other available DOTS server. 348 For example, a mitigation request to protect target resources bound 349 to a PA IP address/prefix cannot be satisfied by a provisioning 350 domain another domain than the one that owns those addresses/ 351 prefixes. Consequently, if a CPE detects a DDoS attack that spreads 352 over all its network attachments, it MUST contact both DOTS servers 353 for mitigation purposes. Nevertheless, if the DDoS attack is 354 received from one single network, then only the DOTS server of that 355 network MUST be contacted. 357 The DOTS client MUST be able to associate a DOTS server with each 358 provisioning domain. For example, if the DOTS client is provisioned 359 with S1 using DHCP when attaching to a first network and with S2 360 using Protocol Configuration Option (PCO) when attaching to a second 361 network, the DOTS client must record the interface from which a DOTS 362 server was provisioned. DOTS signaling session to a given DOTS 363 server must be established using the interface from which the DOTS 364 server was provisioned. 366 +--+ 367 ----------|S1| 368 / +--+ 369 / DOTS Server Domain #1 370 / 371 +---+/ 372 | C | 373 +---+\ 374 \ 375 \ 376 \ +--+ 377 ----------|S2| 378 +--+ 379 DOTS Server Domain #2 381 Figure 5: DOTS Associations for a Multihomed Residential CPE 383 5.2. Multi-Homed Enterprise: Single CPE, Multiple Upstream ISPs 385 Figure 6 illustrates a first set of DOTS associations that can be 386 established with a DOTS gateway, which is enabled within the context 387 of the scenario described in Section 4.2. This deployment is 388 characterized as follows: 390 o One of more DOTS clients are enabled in hosts located in the 391 internal network. 393 o A DOTS gateway is enabled to aggregate and then relay the requests 394 towards upstream DOTS servers. 396 When PA addresses/prefixes are in use, the same considerations 397 discussed in Section 5.1 need to be followed by the DOTS gateway to 398 contact its DOTS server(s). The DOTS gateways can be reachable from 399 DOTS clients by using an unicast address or an anycast address. 401 Nevertheless, when PI addresses/prefixes are assigned, the DOTS 402 gateway MUST send mitigation requests to all its DOTS servers. 403 Otherwise, the attack traffic may still be delivered via the ISP 404 which hasn't received the mitigation request. 406 +--+ 407 ----------|S1| 408 +---+ / +--+ 409 | C1|----+ / DOTS Server Domain #1 410 +---+ | / 411 +---+ +-+-+/ 412 | C3|------| G | 413 +---+ +-+-+\ 414 +---+ | \ 415 | C2|----+ \ 416 +---+ \ +--+ 417 ----------|S2| 418 +--+ 419 DOTS Server Domain #2 421 Figure 6: Multiple DOTS Clients, Single DOTS Gateway, Multiple DOTS 422 Servers 424 An alternate deployment model is depicted in Figure 7. This 425 deployment assumes that: 427 o One or more DOTS clients are enabled in hosts located in the 428 internal network. These DOTS clients may use [RFC8973] to 429 discover their DOTS server(s). 431 o These DOTS clients communicate directly with upstream DOTS 432 servers. 434 If PI addresses/prefixes are in use, the DOTS client MUST send a 435 mitigation request to all the DOTS servers. The use of anycast 436 addresses to reach the DOTS servers is NOT RECOMMENDED. 438 If PA addresses/prefixes are used, the same considerations discussed 439 in Section 5.1 need to be followed by the DOTS clients. Because DOTS 440 clients are not embedded in the CPE and multiple addreses/prefixes 441 may not be assigned to the DOTS client (typically in an IPv4 442 context), some issues arise to steer traffic towards the appropriate 443 DOTS server by using the appropriate source IP address. These 444 complications discussed in [RFC4116] are not specific to DOTS. 446 .......... 447 . +--+ . 448 +--------|C1|--------+ 449 | . +--+ . | 450 +--+ . +--+ . +--+ 451 |S2|------|C3|------|S1| 452 +--+ . +--+ . +--+ 453 | . +--+ . | 454 +--------|C2|--------+ 455 . +--+ . 456 .......... 457 DOTS Client 458 Domain 460 Figure 7: Multiple DOTS Clients, Multiple DOTS Servers 462 Another deployment approach is to enable many DOTS clients; each of 463 them is responsible for handling communications with a specific DOTS 464 server (see Figure 8). 466 .......... 467 . +--+ . 468 +--------|C1| . 469 | . +--+ . 470 +--+ . +--+ . +--+ 471 |S2| . |C2|------|S1| 472 +--+ . +--+ . +--+ 473 .......... 474 DOTS Client 475 Domain 477 Figure 8: Single Homed DOTS Clients 479 Each DOTS client SHOULD be provided with policies (e.g., a prefix 480 filter that will be against DDoS detection alarms) that will trigger 481 DOTS communications with the DOTS servers. Such policies will help 482 the DOTS client to select the appropriate destination DOTS server. 484 The CPE MUST select the appropriate source IP address when forwarding 485 DOTS messages received from an internal DOTS client. If anycast 486 addresses are used to reach DOTS servers, the CPE may not be able to 487 select the appropriate provisioning domain to which the mitigation 488 request should be forwarded. As a consequence, the request may not 489 be forwarded to the appropriate DOTS server. 491 5.3. Multi-Homed Enterprise: Multiple CPEs, Multiple Upstream ISPs 493 The deployments depicted in Figures 7 and 8 also apply to the 494 scenario described in Section 4.3. One specific problem for this 495 scenario is to select the appropriate exit router when contacting a 496 given DOTS server. 498 An alternative deployment scheme is shown in Figure 9: 500 o DOTS clients are enabled in hosts located in the internal network. 502 o A DOTS gateway is enabled in each CPE (rtr1, rtr2). 504 o Each of these DOTS gateways communicates with the DOTS server of 505 the provisioning domain. 507 When PI addresses/prefixes are used, DOTS clients MUST contact all 508 the DOTS gateways to send a DOTS message. DOTS gateways will then 509 relay the request to the DOTS server. Note that the use of anycast 510 addresses is NOT RECOMMENDED to establish DOTS sessions between DOTS 511 clients and DOTS gateways. 513 When PA addresses/prefixes are used, but no filter rules are provided 514 to DOTS clients, the latter MUST contact all DOTS gateways 515 simultaneously to send a DOTS message. Upon receipt of a request by 516 a DOTS gateway, it MUST check whether the request is to be forwarded 517 upstream (if the target IP prefix is managed by the upstream server) 518 or rejected. 520 When PA addresses/prefixes are used, but specific filter rules are 521 provided to DOTS clients using some means that are out of scope of 522 this document, the clients MUST select the appropriate DOTS gateway 523 to reach. The use of anycast addresses is NOT RECOMMENDED to reach 524 DOTS gateways. 526 +---+ 527 +------------| C1|----+ 528 | +---+ | 529 +--+ +-+-+ +---+ +-+-+ +--+ 530 |S2|------|G2 |------| C3|------|G1 |------|S1| 531 +--+ +-+-+ +---+ +-+-+ +--+ 532 | +---+ | 533 +------------| C2|----+ 534 +---+ 536 Figure 9: Multiple DOTS Clients, Multiple DOTS Gateways, Multiple 537 DOTS Servers 539 5.4. Multi-Homed Enterprise: Single ISP 541 The key difference of the scenario described in Section 4.4 compared 542 to the other scenarios is that multi-homing is provided by the same 543 ISP. Concretely, that ISP can decide to provision the enterprise 544 network with: 546 o The same DOTS server for all network attachments. 548 o Distinct DOTS servers for each network attachment. These DOTS 549 servers need to coordinate when a mitigation action is received 550 from the enterprise network. 552 In both cases, DOTS agents enabled within the enterprise network MAY 553 decide to select one or all network attachments to send DOTS 554 mitigation requests. 556 6. Security Considerations 558 DOTS-related security considerations are discussed in Section 4 of 559 [RFC8811]. 561 DOTS clients should control the information that they share with peer 562 DOTS servers. For example, if a DOTS client maintains DOTS 563 associations with specific DOTS servers per interconnection link, the 564 DOTS client should not leak information specific to a given link to 565 DOTS servers not authorized to mitigate attacks received on that 566 link. Whether this constraint is relaxed is deployment specific and 567 must be subject to explicit consent from the DOTS client domain 568 administrator. 570 7. IANA Considerations 572 This document does not require any action from IANA. 574 8. Acknowledgements 576 Thanks to Roland Dobbins, Nik Teague, Jon Shallow, Dan Wing, and 577 Christian Jacquenet for sharing their comments on the mailing list. 579 Thanks to Kirill Kasavchenko for the comments. 581 9. References 582 9.1. Normative References 584 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 585 Requirement Levels", BCP 14, RFC 2119, 586 DOI 10.17487/RFC2119, March 1997, 587 . 589 [RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown, 590 "Default Address Selection for Internet Protocol Version 6 591 (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012, 592 . 594 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 595 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 596 May 2017, . 598 [RFC8811] Mortensen, A., Ed., Reddy.K, T., Ed., Andreasen, F., 599 Teague, N., and R. Compton, "DDoS Open Threat Signaling 600 (DOTS) Architecture", RFC 8811, DOI 10.17487/RFC8811, 601 August 2020, . 603 9.2. Informative References 605 [I-D.ietf-dots-use-cases] 606 Dobbins, R., Migault, D., Moskowitz, R., Teague, N., Xia, 607 L., and K. Nishizuka, "Use cases for DDoS Open Threat 608 Signaling", draft-ietf-dots-use-cases-25 (work in 609 progress), July 2020. 611 [RFC3582] Abley, J., Black, B., and V. Gill, "Goals for IPv6 Site- 612 Multihoming Architectures", RFC 3582, 613 DOI 10.17487/RFC3582, August 2003, 614 . 616 [RFC4116] Abley, J., Lindqvist, K., Davies, E., Black, B., and V. 617 Gill, "IPv4 Multihoming Practices and Limitations", 618 RFC 4116, DOI 10.17487/RFC4116, July 2005, 619 . 621 [RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet 622 Denial-of-Service Considerations", RFC 4732, 623 DOI 10.17487/RFC4732, December 2006, 624 . 626 [RFC7556] Anipko, D., Ed., "Multiple Provisioning Domain 627 Architecture", RFC 7556, DOI 10.17487/RFC7556, June 2015, 628 . 630 [RFC8043] Sarikaya, B. and M. Boucadair, "Source-Address-Dependent 631 Routing and Source Address Selection for IPv6 Hosts: 632 Overview of the Problem Space", RFC 8043, 633 DOI 10.17487/RFC8043, January 2017, 634 . 636 [RFC8782] Reddy.K, T., Ed., Boucadair, M., Ed., Patil, P., 637 Mortensen, A., and N. Teague, "Distributed Denial-of- 638 Service Open Threat Signaling (DOTS) Signal Channel 639 Specification", RFC 8782, DOI 10.17487/RFC8782, May 2020, 640 . 642 [RFC8783] Boucadair, M., Ed. and T. Reddy.K, Ed., "Distributed 643 Denial-of-Service Open Threat Signaling (DOTS) Data 644 Channel Specification", RFC 8783, DOI 10.17487/RFC8783, 645 May 2020, . 647 [RFC8973] Boucadair, M. and T. Reddy.K, "DDoS Open Threat Signaling 648 (DOTS) Agent Discovery", RFC 8973, DOI 10.17487/RFC8973, 649 January 2021, . 651 Authors' Addresses 653 Mohamed Boucadair 654 Orange 655 Rennes 35000 656 France 658 Email: mohamed.boucadair@orange.com 660 Tirumaleswar Reddy 661 McAfee, Inc. 662 Embassy Golf Link Business Park 663 Bangalore, Karnataka 560071 664 India 666 Email: TirumaleswarReddy_Konda@McAfee.com 668 Wei Pan 669 Huawei Technologies 671 Email: william.panwei@huawei.com