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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 DOTS T. Reddy 3 Internet-Draft Cisco 4 Intended status: Standards Track M. Boucadair 5 Expires: October 20, 2017 Orange 6 P. Patil 7 Cisco 8 A. Mortensen 9 Arbor Networks, Inc. 10 N. Teague 11 Verisign, Inc. 12 April 18, 2017 14 Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal 15 Channel 16 draft-ietf-dots-signal-channel-01 18 Abstract 20 This document specifies the DOTS signal channel, a protocol for 21 signaling the need for protection against Distributed Denial-of- 22 Service (DDoS) attacks to a server capable of enabling network 23 traffic mitigation on behalf of the requesting client. A companion 24 document defines the DOTS data channel, a separate reliable 25 communication layer for DOTS management and configuration. 27 Status of This Memo 29 This Internet-Draft is submitted in full conformance with the 30 provisions of BCP 78 and BCP 79. 32 Internet-Drafts are working documents of the Internet Engineering 33 Task Force (IETF). Note that other groups may also distribute 34 working documents as Internet-Drafts. The list of current Internet- 35 Drafts is at http://datatracker.ietf.org/drafts/current/. 37 Internet-Drafts are draft documents valid for a maximum of six months 38 and may be updated, replaced, or obsoleted by other documents at any 39 time. It is inappropriate to use Internet-Drafts as reference 40 material or to cite them other than as "work in progress." 42 This Internet-Draft will expire on October 20, 2017. 44 Copyright Notice 46 Copyright (c) 2017 IETF Trust and the persons identified as the 47 document authors. All rights reserved. 49 This document is subject to BCP 78 and the IETF Trust's Legal 50 Provisions Relating to IETF Documents 51 (http://trustee.ietf.org/license-info) in effect on the date of 52 publication of this document. Please review these documents 53 carefully, as they describe your rights and restrictions with respect 54 to this document. Code Components extracted from this document must 55 include Simplified BSD License text as described in Section 4.e of 56 the Trust Legal Provisions and are provided without warranty as 57 described in the Simplified BSD License. 59 Table of Contents 61 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 62 2. Notational Conventions and Terminology . . . . . . . . . . . 3 63 3. Solution Overview . . . . . . . . . . . . . . . . . . . . . . 4 64 4. Happy Eyeballs for DOTS Signal Channel . . . . . . . . . . . 5 65 5. DOTS Signal Channel . . . . . . . . . . . . . . . . . . . . . 7 66 5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 7 67 5.2. DOTS Signal YANG Model . . . . . . . . . . . . . . . . . 8 68 5.2.1. Mitigation Request Model structure . . . . . . . . . 8 69 5.2.2. Mitigation Request Model . . . . . . . . . . . . . . 8 70 5.2.3. Session Configuration Model structure . . . . . . . . 10 71 5.2.4. Session Configuration Model . . . . . . . . . . . . . 10 72 5.3. Mitigation Request . . . . . . . . . . . . . . . . . . . 12 73 5.3.1. Requesting mitigation . . . . . . . . . . . . . . . . 12 74 5.3.2. Withdraw a DOTS Signal . . . . . . . . . . . . . . . 17 75 5.3.3. Retrieving a DOTS Signal . . . . . . . . . . . . . . 18 76 5.3.4. Efficacy Update from DOTS Client . . . . . . . . . . 23 77 5.4. DOTS Signal Channel Session Configuration . . . . . . . . 25 78 5.4.1. Discover Acceptable Configuration Parameters . . . . 26 79 5.4.2. Convey DOTS Signal Channel Session Configuration . . 27 80 5.4.3. Delete DOTS Signal Channel Session Configuration . . 29 81 5.4.4. Retrieving DOTS Signal Channel Session Configuration 29 82 5.5. Redirected Signaling . . . . . . . . . . . . . . . . . . 30 83 5.6. Heartbeat Mechanism . . . . . . . . . . . . . . . . . . . 31 84 6. Mapping parameters to CBOR . . . . . . . . . . . . . . . . . 32 85 7. (D)TLS Protocol Profile and Performance considerations . . . 32 86 7.1. MTU and Fragmentation Issues . . . . . . . . . . . . . . 33 87 8. (D)TLS 1.3 considerations . . . . . . . . . . . . . . . . . . 34 88 9. Mutual Authentication of DOTS Agents & Authorization of DOTS 89 Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . 35 90 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 37 91 10.1. DOTS signal channel CBOR Mappings Registry . . . . . . . 37 92 10.1.1. Registration Template . . . . . . . . . . . . . . . 37 93 10.1.2. Initial Registry Contents . . . . . . . . . . . . . 37 94 11. Implementation Status . . . . . . . . . . . . . . . . . . . . 41 95 11.1. nttdots . . . . . . . . . . . . . . . . . . . . . . . . 41 96 12. Security Considerations . . . . . . . . . . . . . . . . . . . 42 97 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 42 98 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 43 99 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 43 100 15.1. Normative References . . . . . . . . . . . . . . . . . . 43 101 15.2. Informative References . . . . . . . . . . . . . . . . . 44 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 46 104 1. Introduction 106 A distributed denial-of-service (DDoS) attack is an attempt to make 107 machines or network resources unavailable to their intended users. 108 In most cases, sufficient scale can be achieved by compromising 109 enough end-hosts and using those infected hosts to perpetrate and 110 amplify the attack. The victim in this attack can be an application 111 server, a host, a router, a firewall, or an entire network. 113 In many cases, it may not be possible for an network administrators 114 to determine the causes of an attack, but instead just realize that 115 certain resources seem to be under attack. This document defines a 116 lightweight protocol permitting a DOTS client to request mitigation 117 from one or more DOTS servers for protection against detected, 118 suspected, or anticipated attacks . This protocol enables cooperation 119 between DOTS agents to permit a highly-automated network defense that 120 is robust, reliable and secure. 122 The requirements for DOTS signal channel protocol are obtained from 123 [I-D.ietf-dots-requirements]. 125 This document satisfies all the use cases discussed in 126 [I-D.ietf-dots-use-cases] except the Third-party DOTS notifications 127 use case in Section 3.2.3 of [I-D.ietf-dots-use-cases] which is an 128 optional feature and not a core use case. Third-party DOTS 129 notifications are not part of the DOTS requirements document. 130 Moreover, the DOTS architecture does not assess whether that use case 131 may have an impact on the architecture itself and/or the DOTS trust 132 model. 134 This is a companion document to the DOTS data channel specification 135 [I-D.reddy-dots-data-channel] that defines a configuration and bulk 136 data exchange mechanism supporting the DOTS signal channel. 138 2. Notational Conventions and Terminology 140 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 141 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 142 document are to be interpreted as described in [RFC2119]. 144 (D)TLS: For brevity this term is used for statements that apply to 145 both Transport Layer Security [RFC5246] and Datagram Transport Layer 146 Security [RFC6347]. Specific terms will be used for any statement 147 that applies to either protocol alone. 149 The reader should be familiar with the terms defined in 150 [I-D.ietf-dots-architecture]. 152 3. Solution Overview 154 Network applications have finite resources like CPU cycles, number of 155 processes or threads they can create and use, maximum number of 156 simultaneous connections it can handle, limited resources of the 157 control plane, etc. When processing network traffic, such 158 applications are supposed to use these resources to offer the 159 intended task in the most efficient fashion. However, an attacker 160 may be able to prevent an application from performing its intended 161 task by causing the application to exhaust the finite supply of a 162 specific resource. 164 TCP DDoS SYN-flood, for example, is a memory-exhaustion attack on the 165 victim and ACK-flood is a CPU exhaustion attack on the victim 166 ([RFC4987]). Attacks on the link are carried out by sending enough 167 traffic such that the link becomes excessively congested, and 168 legitimate traffic suffers high packet loss. Stateful firewalls can 169 also be attacked by sending traffic that causes the firewall to hold 170 excessive state. The firewall then runs out of memory, and can no 171 longer instantiate the state required to pass legitimate flows. 172 Other possible DDoS attacks are discussed in [RFC4732]. 174 In each of the cases described above, the possible arrangements 175 between the DOTS client and DOTS server to mitigate the attack are 176 discussed in [I-D.ietf-dots-use-cases]. An example of network 177 diagram showing a deployment of these elements is shown in Figure 1. 178 Architectural relationships between involved DOTS agents is explained 179 in [I-D.ietf-dots-architecture]. In this example, the DOTS server is 180 operating on the access network. 182 Network 183 Resource CPE router Access network __________ 184 +-----------+ +--------------+ +-------------+ / \ 185 | |____| |_______| |___ | Internet | 186 |DOTS client| | DOTS gateway | | DOTS server | | | 187 | | | | | | | | 188 +-----------+ +--------------+ +-------------+ \__________/ 190 Figure 1 192 The DOTS server can also be running on the Internet, as depicted in 193 Figure 2. 195 Network DDoS mitigation 196 Resource CPE router __________ service 197 +-----------+ +-------------+ / \ +-------------+ 198 | |____| |_______| |___ | | 199 |DOTS client| |DOTS gateway | | Internet | | DOTS server | 200 | | | | | | | | | 201 +-----------+ +-------------+ \__________/ +-------------+ 203 Figure 2 205 In typical deployments, the DOTS client belongs to a different 206 administrative domain than the DOTS server. For example, the DOTS 207 client is a firewall protecting services owned and operated by an 208 domain, while the DOTS server is owned and operated by a different 209 domain providing DDoS mitigation services. That domain providing 210 DDoS mitigation service might, or might not, also provide Internet 211 access service to the website operator. 213 The DOTS server may (not) be co-located with the DOTS mitigator. In 214 typical deployments, the DOTS server belongs to the same 215 administrative domain as the mitigator. 217 The DOTS client can communicate directly with the DOTS server or 218 indirectly via a DOTS gateway. 220 This document focuses on the DOTS signal channel. 222 4. Happy Eyeballs for DOTS Signal Channel 224 DOTS signaling can happen with DTLS [RFC6347] over UDP and TLS 225 [RFC5246] over TCP. A DOTS client can use DNS to determine the IP 226 address(es) of a DOTS server or a DOTS client may be provided with 227 the list of DOTS server IP addresses. The DOTS client MUST know a 228 DOTS server's domain name; hard-coding the domain name of the DOTS 229 server into software is NOT RECOMMENDED in case the domain name is 230 not valid or needs to change for legal or other reasons. The DOTS 231 client performs A and/or AAAA record lookup of the domain name and 232 the result will be a list of IP addresses, each of which can be used 233 to contact the DOTS server using UDP and TCP. 235 If an IPv4 path to reach a DOTS server is found, but the DOTS 236 server's IPv6 path is not working, a dual-stack DOTS client can 237 experience a significant connection delay compared to an IPv4-only 238 DOTS client. The other problem is that if a middlebox between the 239 DOTS client and DOTS server is configured to block UDP, the DOTS 240 client will fail to establish a DTLS session with the DOTS server and 241 will, then, have to fall back to TLS over TCP incurring significant 242 connection delays. [I-D.ietf-dots-requirements] discusses that DOTS 243 client and server will have to support both connectionless and 244 connection-oriented protocols. 246 To overcome these connection setup problems, the DOTS client can try 247 connecting to the DOTS server using both IPv6 and IPv4, and try both 248 DTLS over UDP and TLS over TCP in a fashion similar to the Happy 249 Eyeballs mechanism [RFC6555]. These connection attempts are 250 performed by the DOTS client when its initializes, and the client 251 uses that information for its subsequent alert to the DOTS server. 252 In order of preference (most preferred first), it is UDP over IPv6, 253 UDP over IPv4, TCP over IPv6, and finally TCP over IPv4, which 254 adheres to address preference order [RFC6724] and the DOTS preference 255 that UDP be used over TCP (to avoid TCP's head of line blocking). 257 DOTS client DOTS server 258 | | 259 |--DTLS ClientHello, IPv6 ---->X | 260 |--TCP SYN, IPv6-------------->X | 261 |--DTLS ClientHello, IPv4 ---->X | 262 |--TCP SYN, IPv4----------------------------------------->| 263 |--DTLS ClientHello, IPv6 ---->X | 264 |--TCP SYN, IPv6-------------->X | 265 |<-TCP SYNACK---------------------------------------------| 266 |--DTLS ClientHello, IPv4 ---->X | 267 |--TCP ACK----------------------------------------------->| 268 |<------------Establish TLS Session---------------------->| 269 |----------------DOTS signal----------------------------->| 270 | | 272 Figure 3: Happy Eyeballs 274 In reference to Figure 3, the DOTS client sends two TCP SYNs and two 275 DTLS ClientHello messages at the same time over IPv6 and IPv4. In 276 this example, it is assumed that the IPv6 path is broken and UDP is 277 dropped by a middle box but has little impact to the DOTS client 278 because there is no long delay before using IPv4 and TCP. The DOTS 279 client repeats the mechanism to discover if DOTS signaling with DTLS 280 over UDP becomes available from the DOTS server, so the DOTS client 281 can migrate the DOTS signal channel from TCP to UDP, but such probing 282 SHOULD NOT be done more frequently than every 24 hours and MUST NOT 283 be done more frequently than every 5 minutes. 285 5. DOTS Signal Channel 287 5.1. Overview 289 The DOTS signal channel is built on top of the Constrained 290 Application Protocol (CoAP) [RFC7252], a lightweight protocol 291 originally designed for constrained devices and networks. CoAP's 292 expectation of packet loss, support for asynchronous non-confirmable 293 messaging, congestion control, small message overhead limiting the 294 need for fragmentation, use of minimal resources, and support for 295 (D)TLS make it a good foundation on which to build the DOTS signaling 296 mechanism. 298 The DOTS signal channel is layered on existing standards (Figure 4). 300 +--------------+ 301 | DOTS | 302 +--------------+ 303 | CoAP | 304 +--------------+ 305 | TLS | DTLS | 306 +--------------+ 307 | TCP | UDP | 308 +--------------+ 309 | IP | 310 +--------------+ 312 Figure 4: Abstract Layering of DOTS signal channel over CoAP over 313 (D)TLS 315 The signal channel is initiated by the DOTS client. Once the signal 316 channel is established, the DOTS agents periodically send heartbeats 317 to keep the channel active. At any time, the DOTS client may send a 318 mitigation request message to the DOTS server over the active 319 channel. While mitigation is active, the DOTS server periodically 320 sends status messages to the client, including basic mitigation 321 feedback details. Mitigation remains active until the DOTS client 322 explicitly terminates mitigation, or the mitigation lifetime expires. 324 Messages exchanged between DOTS client and server are serialized 325 using Concise Binary Object Representation (CBOR) [RFC7049], CBOR is 326 a binary encoding designed for small code and message size. CBOR 327 encoded payloads are used to convey signal channel specific payload 328 messages that convey request parameters and response information such 329 as errors. This specification uses the encoding rules defined in 330 [I-D.ietf-core-yang-cbor] for representing mitigation scope and DOTS 331 signal channel session configuration data defined using YANG 332 (Section 5.2) as CBOR data. 334 5.2. DOTS Signal YANG Model 336 This document defines a YANG [RFC6020] data model for mitigation 337 scope and DOTS signal channel session configuration data. 339 5.2.1. Mitigation Request Model structure 341 This document defines the YANG module "ietf-dots-signal", which has 342 the following structure: 344 module: ietf-dots-signal 345 +--rw mitigation-scope 346 +--rw scope* [mitigation-id] 347 +--rw mitigation-id int32 348 +--rw target-ip* inet:ip-address 349 +--rw target-prefix* inet:ip-prefix 350 +--rw target-port-range* [lower-port upper-port] 351 | +--rw lower-port inet:port-number 352 | +--rw upper-port inet:port-number 353 +--rw target-protocol* uint8 354 +--rw FQDN* inet:domain-name 355 +--rw URI* inet:uri 356 +--rw alias* string 357 +--rw lifetime? int32 359 5.2.2. Mitigation Request Model 361 file "ietf-dots-signal@2016-11-28.yang" 363 module ietf-dots-signal { 364 namespace "urn:ietf:params:xml:ns:yang:ietf-dots-signal"; 365 prefix "signal"; 366 import ietf-inet-types { 367 prefix "inet"; 368 } 369 organization "Cisco Systems, Inc."; 370 contact "Tirumaleswar Reddy "; 372 description 373 "This module contains YANG definition for DOTS 374 signal sent by the DOTS client to the DOTS server"; 376 revision 2016-11-28 { 377 reference 378 "https://tools.ietf.org/html/draft-reddy-dots-signal-channel"; 379 } 381 container mitigation-scope { 382 description "top level container for mitigation request"; 383 list scope { 384 key mitigation-id; 385 description "Identifier for the mitigation request"; 386 leaf mitigation-id { 387 type int32; 388 description "mitigation request identifier"; 389 } 390 leaf-list target-ip { 391 type inet:ip-address; 392 description "IP address"; 393 } 394 leaf-list target-prefix { 395 type inet:ip-prefix; 396 description "prefix"; 397 } 398 list target-port-range { 399 key "lower-port upper-port"; 400 description "Port range. When only lower-port is present, 401 it represents a single port."; 402 leaf lower-port { 403 type inet:port-number; 404 mandatory true; 405 description "lower port"; 406 } 407 leaf upper-port { 408 type inet:port-number; 409 must ". >= ../lower-port" { 410 error-message 411 "The upper-port must be greater than or 412 equal to lower-port"; 413 } 414 description "upper port"; 415 } 416 } 417 leaf-list target-protocol { 418 type uint8; 419 description "Internet Protocol number"; 420 } 421 leaf-list FQDN { 422 type inet:domain-name; 423 description "FQDN"; 424 } 425 leaf-list URI { 426 type inet:uri; 427 description "URI"; 428 } 429 leaf-list alias { 430 type string; 431 description "alias name"; 432 } 433 leaf lifetime { 434 type int32; 435 description "lifetime"; 436 } 437 } 438 } 439 } 440 442 5.2.3. Session Configuration Model structure 444 This document defines the YANG module "ietf-dots-signal-config", 445 which has the following structure: 447 module: ietf-dots-signal-config 448 +--rw signal-config 449 +--rw session-id? int32 450 +--rw heartbeat-timeout? int16 451 +--rw max-retransmit? int16 452 +--rw ack-timeout? int16 453 +--rw ack-random-factor? decimal64 455 5.2.4. Session Configuration Model 456 file "ietf-dots-signal-config@2016-11-28.yang" 458 module ietf-dots-signal-config { 459 namespace "urn:ietf:params:xml:ns:yang:ietf-dots-signal-config"; 460 prefix "config"; 461 organization "Cisco Systems, Inc."; 462 contact "Tirumaleswar Reddy "; 464 description 465 "This module contains YANG definition for DOTS 466 signal channel session configuration"; 468 revision 2016-11-28 { 469 reference 470 "https://tools.ietf.org/html/draft-reddy-dots-signal-channel"; 471 } 473 container signal-config { 474 description "top level container for DOTS signal channel session 475 configuration"; 476 leaf session-id { 477 type int32; 478 description "Identifier for the DOTS signal channel 479 session configuration data"; 480 } 481 leaf heartbeat-timeout { 482 type int16; 483 description "heartbeat timeout"; 484 } 485 leaf max-retransmit { 486 type int16; 487 description "Maximum number of retransmissions"; 488 } 489 leaf ack-timeout { 490 type int16; 491 description "Initial retransmission timeout value"; 492 } 493 leaf ack-random-factor { 494 type decimal64 { 495 fraction-digits 2; 496 } 497 description "Random factor used to influence the timing of 498 retransmissions"; 499 } 500 } 501 } 503 504 5.3. Mitigation Request 506 The following methods are used to request or withdraw mitigation 507 requests: 509 PUT: DOTS clients use the PUT method to request mitigation 510 (Section 5.3.1). During active mitigation, DOTS clients may use 511 PUT requests to convey mitigation efficacy updates to the DOTS 512 server (Section 5.3.4). 513 DELETE: DOTS clients use the DELETE method to withdraw a request for 514 mitigation from the DOTS server (Section 5.3.2). 515 GET: DOTS clients may use the GET method to subscribe to DOTS server 516 status messages, or to retrieve the list of existing mitigations 517 (Section 5.3.3). 519 Mitigation request and response messages are marked as Non- 520 confirmable messages. DOTS agents should follow the data 521 transmission guidelines discussed in Section 3.1.3 of 522 [I-D.ietf-tsvwg-rfc5405bis] and control transmission behavior by not 523 sending on average more than one UDP datagram per RTT to the peer 524 DOTS agent. Requests marked by the DOTS client as Non-confirmable 525 messages are sent at regular intervals until a response is received 526 from the DOTS server and if the DOTS client cannot maintain a RTT 527 estimate then it SHOULD NOT send more than one Non-confirmable 528 request every 3 seconds, and SHOULD use an even less aggressive rate 529 when possible (case 2 in Section 3.1.3 of 530 [I-D.ietf-tsvwg-rfc5405bis]). 532 5.3.1. Requesting mitigation 534 When a DOTS client requires mitigation for any reason, the DOTS 535 client uses CoAP PUT method to send a mitigation request to the DOTS 536 server (Figure 5, illustrated in JSON diagnostic notation). The DOTS 537 server can enable mitigation on behalf of the DOTS client by 538 communicating the DOTS client's request to the mitigator and relaying 539 selected mitigator feedback to the requesting DOTS client. 541 Header: PUT (Code=0.03) 542 Uri-Host: "host" 543 Uri-Path: "version" 544 Uri-Path: "dots-signal" 545 Uri-Path: "signal" 546 Content-Type: "application/cbor" 547 { 548 "mitigation-scope": { 549 "scope": [ 550 { 551 "mitigation-id": integer, 552 "target-ip": [ 553 "string" 554 ], 555 "target-prefix": [ 556 "string" 557 ], 558 "target-port-range": [ 559 { 560 "lower-port": integer, 561 "upper-port": integer 562 } 563 ], 564 "target-protocol": [ 565 integer 566 ], 567 "FQDN": [ 568 "string" 569 ], 570 "URI": [ 571 "string" 572 ], 573 "alias": [ 574 "string" 575 ], 576 "lifetime": integer 577 } 578 ] 579 } 580 } 582 Figure 5: PUT to convey DOTS signals 584 The parameters are described below. 586 mitigation-id: Identifier for the mitigation request represented 587 using an integer. This identifier MUST be unique for each 588 mitigation request bound to the DOTS client, i.e., the mitigation- 589 id parameter value in the mitigation request needs to be unique 590 relative to the mitigation-id parameter values of active 591 mitigation requests conveyed from the DOTS client to the DOTS 592 server. This identifier MUST be generated by the DOTS client. 593 This document does not make any assumption about how this 594 identifier is generated. This is a mandatory attribute. 595 target-ip: A list of IP addresses under attack. This is an optional 596 attribute. 597 target-prefix: A list of prefixes under attack. Prefixes are 598 represented using CIDR notation [RFC4632]. This is an optional 599 attribute. 600 target-port-range: A list of ports under attack. The port range, 601 lower-port for lower port number and upper-port for upper port 602 number. When only lower-port is present, it represents a single 603 port. For TCP, UDP, SCTP, or DCCP: the range of ports (e.g., 604 1024-65535). This is an optional attribute. 605 target-protocol: A list of protocols under attack. Internet 606 Protocol numbers. This is an optional attribute. 607 FQDN: A list of Fully Qualified Domain Names. Fully Qualified 608 Domain Name (FQDN) is the full name of a system, rather than just 609 its hostname. For example, "venera" is a hostname, and 610 "venera.isi.edu" is an FQDN. This is an optional attribute. 611 URI: A list of Uniform Resource Identifiers (URI). This is an 612 optional attribute. 613 alias: A list of aliases. Aliases can be created using the DOTS 614 data channel (Section 3.1.1 in [I-D.reddy-dots-data-channel]) or 615 direct connection and then used in subsequent signal channel 616 exchanges to refer more efficiently to the resources under attack. 617 This is an optional attribute. 618 lifetime: Lifetime of the mitigation request in seconds. Upon the 619 expiry of this lifetime, and if the request is not refreshed, the 620 mitigation request is removed. The request can be refreshed by 621 sending the same request again. The default lifetime of the 622 mitigation request is 3600 seconds (60 minutes) -- this value was 623 chosen to be long enough so that refreshing is not typically a 624 burden on the DOTS client, while expiring the request where the 625 client has unexpectedly quit in a timely manner. A lifetime of 626 zero indicates indefinite lifetime for the mitigation request. 627 The server MUST always indicate the actual lifetime in the 628 response and the remaining lifetime in status messages sent to the 629 client. This is an optional attribute in the request. 631 The CBOR key values for the parameters are defined in Section 6. The 632 IANA Considerations section defines how the CBOR key values can be 633 allocated to standards bodies and vendors. In the PUT request at 634 least one of the attributes target-ip or target-prefix or FQDN or URI 635 or alias MUST be present. DOTS agents can safely ignore Vendor- 636 Specific parameters they don't understand. The relative order of two 637 mitigation requests from a DOTS client is determined by comparing 638 their respective mitigation-id values. If two mitigation requests 639 have overlapping mitigation scopes the mitigation request with higher 640 numeric mitigation-id value will override the mitigation request with 641 a lower numeric mitigation-id value. The Uri-Path option carries a 642 major and minor version nomenclature to manage versioning and DOTS 643 signal channel in this specification uses v1 major version. 645 In both DOTS signal and data channel sessions, the DOTS client MUST 646 authenticate itself to the DOTS server (Section 9). The DOTS server 647 couples the DOTS signal and data channel sessions using the DOTS 648 client identity, so the DOTS server can validate whether the aliases 649 conveyed in the mitigation request were indeed created by the same 650 DOTS client using the DOTS data channel session. If the aliases were 651 not created by the DOTS client then the DOTS server returns 4.00 (Bad 652 Request) in the response. The DOTS server couples the DOTS signal 653 channel sessions using the DOTS client identity, and the DOTS server 654 uses mitigation-id parameter value to detect duplicate mitigation 655 requests. 657 Figure 6 shows a PUT request example to signal that ports 80, 8080, 658 and 443 on the servers 2002:db8:6401::1 and 2002:db8:6401::2 are 659 being attacked (illustrated in JSON diagnostic notation). 661 Header: PUT (Code=0.03) 662 Uri-Host: "www.example.com" 663 Uri-Path: "v1" 664 Uri-Path: "dots-signal" 665 Uri-Path: "signal" 666 Content-Format: "application/cbor" 667 { 668 "mitigation-scope": { 669 "scope": [ 670 { 671 "mitigation-id": 12332, 672 "target-ip": [ 673 "2002:db8:6401::1", 674 "2002:db8:6401::2" 675 ], 676 "target-port-range": [ 677 { 678 "lower-port": 80 679 }, 680 { 681 "lower-port": 443 682 }, 683 { 684 "lower-port": 8080 686 } 687 ], 688 "target-protocol": [ 689 6 690 ] 691 } 692 ] 693 } 694 } 696 The CBOR encoding format is shown below: 698 a1 # map(1) 699 01 # unsigned(1) 700 a1 # map(1) 701 02 # unsigned(2) 702 81 # array(1) 703 a4 # map(4) 704 03 # unsigned(3) 705 19 302c # unsigned(12332) 706 04 # unsigned(4) 707 82 # array(2) 708 70 # text(16) 709 323030323a6462383a363430313a3a31 # "2002:db8:6401::1" 710 70 # text(16) 711 323030323a6462383a363430313a3a32 # "2002:db8:6401::2" 712 05 # unsigned(5) 713 83 # array(3) 714 a1 # map(1) 715 06 # unsigned(6) 716 18 50 # unsigned(80) 717 a1 # map(1) 718 06 # unsigned(6) 719 19 01bb # unsigned(443) 720 a1 # map(1) 721 06 # unsigned(6) 722 19 1f90 # unsigned(8080) 723 08 # unsigned(8) 724 81 # array(1) 725 06 # unsigned(6) 727 Figure 6: POST for DOTS signal 729 The DOTS server indicates the result of processing the PUT request 730 using CoAP response codes. CoAP 2.xx codes are success. CoAP 4.xx 731 codes are some sort of invalid requests. COAP 5.xx codes are 732 returned if the DOTS server has erred or is currently unavailable to 733 provide mitigation in response to the mitigation request from the 734 DOTS client. If the DOTS server does not find the mitigation-id 735 parameter value conveyed in the PUT request in its configuration data 736 then the server MAY accept the mitigation request, and a 2.01 737 (Created) response is returned to the DOTS client, and the DOTS 738 server will try to mitigate the attack. If the DOTS server finds the 739 mitigation-id parameter value conveyed in the PUT request in its 740 configuration data then the server MAY update the mitigation request, 741 and a 2.04 (Changed) response is returned to indicate a successful 742 updation of the mitigation request. If the request is missing one or 743 more mandatory attributes, then 4.00 (Bad Request) will be returned 744 in the response or if the request contains invalid or unknown 745 parameters then 4.02 (Invalid query) will be returned in the 746 response. For responses indicating a client or server error, the 747 payload explains the error situation of the result of the requested 748 action (Section 5.5 in [RFC7252]). 750 5.3.2. Withdraw a DOTS Signal 752 A DELETE request is used to withdraw a DOTS signal from a DOTS server 753 (Figure 7). 755 Header: DELETE (Code=0.04) 756 Uri-Host: "host" 757 Uri-Path: "version" 758 Uri-Path: "dots-signal" 759 Uri-Path: "signal" 760 Content-Format: "application/cbor" 761 { 762 "mitigation-scope": { 763 "scope": [ 764 { 765 "mitigation-id": integer 766 } 767 ] 768 } 769 } 771 Figure 7: Withdraw DOTS signal 773 If the DOTS server does not find the mitigation-id parameter value 774 conveyed in the DELETE request in its configuration data, then it 775 responds with a 4.04 (Not Found) error response code. The DOTS 776 server successfully acknowledges a DOTS client's request to withdraw 777 the DOTS signal using 2.02 (Deleted) response code, and ceases 778 mitigation activity as quickly as possible. 780 To protect against route or DNS flapping caused by a client rapidly 781 toggling mitigation, and to dampen the effect of oscillating attacks, 782 DOTS servers MAY continue mitigation for a period of up to fifteen 783 minutes after acknowledging a DOTS client's withdrawal of a 784 mitigation request. During this period, DOTS server mitigation 785 status messages SHOULD indicate that mitigation is active but 786 terminating. After the fifteen-minute period elapses, the DOTS 787 server MUST treat the mitigation as terminated, as the DOTS client is 788 no longer responsible for the mitigation. 790 5.3.3. Retrieving a DOTS Signal 792 A GET request is used to retrieve information and status of a DOTS 793 signal from a DOTS server (Figure 8). If the DOTS server does not 794 find the mitigation-id parameter value conveyed in the GET request in 795 its configuration data, then it responds with a 4.04 (Not Found) 796 error response code. The 'c' (content) parameter and its permitted 797 values defined in [I-D.ietf-core-comi] can be used to retrieve non- 798 configuration data or configuration data or both. 800 1) To retrieve all DOTS signals signaled by the DOTS client. 802 Header: GET (Code=0.01) 803 Uri-Host: "host" 804 Uri-Path: "version" 805 Uri-Path: "dots-signal" 806 Uri-Path: "signal" 807 Observe : 0 809 2) To retrieve a specific DOTS signal signaled by the DOTS client. 810 The configuration data in the response will be formatted in the 811 same order it was processed at the DOTS server. 813 Header: GET (Code=0.01) 814 Uri-Host: "host" 815 Uri-Path: "version" 816 Uri-Path: "dots-signal" 817 Uri-Path: "signal" 818 Observe : 0 819 Content-Format: "application/cbor" 820 { 821 "mitigation-scope": { 822 "scope": [ 823 { 824 "mitigation-id": integer 825 } 826 ] 827 } 828 } 830 Figure 8: GET to retrieve the rules 832 Figure 9 shows a response example of all the active mitigation 833 requests associated with the DOTS client on the DOTS server and the 834 mitigation status of each mitigation request. 836 { 837 "mitigation-scope":[ 838 { 839 "scope": [ 840 { 841 "mitigation-id": 12332, 842 "target-protocol": [ 843 17 844 ], 845 "lifetime":1800, 846 "status":2, 847 "bytes-dropped": 134334555, 848 "bps-dropped": 43344, 849 "pkts-dropped": 333334444, 850 "pps-dropped": 432432 851 } 852 ] 853 }, 854 { 855 "scope": [ 856 { 857 "mitigation-id": 12333, 858 "target-protocol": [ 859 6 860 ], 861 "lifetime":1800, 862 "status":3 863 "bytes-dropped": 0, 864 "bps-dropped": 0, 865 "pkts-dropped": 0, 866 "pps-dropped": 0 867 } 868 ] 869 } 870 ] 871 } 873 Figure 9: Response body 875 The mitigation status parameters are described below. 877 bytes-dropped: The total dropped byte count for the mitigation 878 request. This is a optional attribute. 879 bps-dropped: The average dropped bytes per second for the mitigation 880 request. This is a optional attribute. 881 pkts-dropped: The total dropped packet count for the mitigation 882 request. This is a optional attribute. 884 pps-dropped: The average dropped packets per second for the 885 mitigation request. This is a optional attribute. 886 status: Status of attack mitigation. The 'status' parameter is a 887 mandatory attribute. 889 The various possible values of 'status' parameter are explained 890 below: 892 /--------------------+---------------------------------------------------\ 893 | Parameter value | Description | 894 |--------------------+---------------------------------------------------| 895 | 1 | Attack mitigation is in progress | 896 | | (e.g., changing the network path to re-route the | 897 | | inbound traffic to DOTS mitigator). | 898 +------------------------------------------------------------------------+ 899 | 2 | Attack is successfully mitigated | 900 | | (e.g., traffic is redirected to a DDOS mitigator | 901 | | and attack traffic is dropped). | 902 +------------------------------------------------------------------------+ 903 | 3 | Attack has stopped and the DOTS client | 904 | | can withdraw the mitigation request. | 905 +------------------------------------------------------------------------+ 906 | 4 | Attack has exceeded the mitigation provider | 907 | | capability. | 908 +------------------------------------------------------------------------+ 909 | 5 | DOTS client has withdrawn the mitigation request | 910 and the mitigation is active but terminating. | 911 | | | 912 \--------------------+---------------------------------------------------/ 914 The observe option defined in [RFC7641] extends the CoAP core 915 protocol with a mechanism for a CoAP client to "observe" a resource 916 on a CoAP server: the client retrieves a representation of the 917 resource and requests this representation be updated by the server as 918 long as the client is interested in the resource. A DOTS client 919 conveys the observe option set to 0 in the GET request to receive 920 unsolicited notifications of attack mitigation status from the DOTS 921 server. Unidirectional notifications within the bidirectional signal 922 channel allows unsolicited message delivery, enabling asynchronous 923 notifications between the agents. A DOTS client that is no longer 924 interested in receiving notifications from the DOTS server can simply 925 "forget" the observation. When the DOTS server then sends the next 926 notification, the DOTS client will not recognize the token in the 927 message and thus will return a Reset message. This causes the DOTS 928 server to remove the associated entry. 930 DOTS Client DOTS Server 931 | | 932 | GET / | 933 | Token: 0x4a | Registration 934 | Observe: 0 | 935 +------------------------------>| 936 | | 937 | 2.05 Content | 938 | Token: 0x4a | Notification of 939 | Observe: 12 | the current state 940 | status: "mitigation | 941 | in progress" | 942 |<------------------------------+ 943 | 2.05 Content | 944 | Token: 0x4a | Notification upon 945 | Observe: 44 | a state change 946 | status: "mitigation | 947 | complete" | 948 |<------------------------------+ 949 | 2.05 Content | 950 | Token: 0x4a | Notification upon 951 | Observe: 60 | a state change 952 | status: "attack stopped" | 953 |<------------------------------+ 954 | | 956 Figure 10: Notifications of attack mitigation status 958 5.3.3.1. Mitigation Status 960 A DOTS client retrieves the information about a DOTS signal at 961 frequent intervals to determine the status of an attack. If the DOTS 962 server has been able to mitigate the attack and the attack has 963 stopped, the DOTS server indicates as such in the status, and the 964 DOTS client recalls the mitigation request. 966 A DOTS client should react to the status of the attack from the DOTS 967 server and not the fact that it has recognized, using its own means, 968 that the attack has been mitigated. This ensures that the DOTS 969 client does not recall a mitigation request in a premature fashion 970 because it is possible that the DOTS client does not sense the DDOS 971 attack on its resources but the DOTS server could be actively 972 mitigating the attack and the attack is not completely averted. 974 5.3.4. Efficacy Update from DOTS Client 976 While DDoS mitigation is active, a DOTS client MAY frequently 977 transmit DOTS mitigation efficacy updates to the relevant DOTS 978 server. An PUT request (Figure 11) is used to convey the mitigation 979 efficacy update to the DOTS server. The PUT request MUST include all 980 the parameters used in the PUT request to convey the DOTS signal 981 (Section 5.3.1). 983 Header: PUT (Code=0.03) 984 Uri-Host: "host" 985 Uri-Path: "version" 986 Uri-Path: "dots-signal" 987 Uri-Path: "signal" 988 Content-Format: "application/cbor" 989 { 990 "mitigation-scope": { 991 "scope": [ 992 { 993 "mitigation-id": integer, 994 "target-ip": [ 995 "string" 996 ], 997 "target-port-range": [ 998 { 999 "lower-port": integer, 1000 "upper-port": integer 1001 } 1002 ], 1003 "target-protocol": [ 1004 integer 1005 ], 1006 "FQDN": [ 1007 "string" 1008 ], 1009 "URI": [ 1010 "string" 1011 ], 1012 "alias": [ 1013 "string" 1014 ], 1015 "lifetime": integer, 1016 "attack-status": integer 1017 } 1018 ] 1019 } 1020 } 1022 Figure 11: Efficacy Update 1024 The 'attack-status' parameter is a mandatory attribute. The various 1025 possible values contained in the 'attack-status' parameter are 1026 explained below: 1028 /--------------------+------------------------------------------------------\ 1029 | Parameter value | Description | 1030 |--------------------+------------------------------------------------------| 1031 | 1 | DOTS client determines that it is still under attack.| 1032 +---------------------------------------------------------------------------+ 1033 | 2 | DOTS client determines that the attack is | 1034 | | successfully mitigated | 1035 | | (e.g., attack traffic is not seen). | 1036 \--------------------+------------------------------------------------------/ 1038 The DOTS server indicates the result of processing the PUT request 1039 using CoAP response codes. The response code 2.04 (Changed) will be 1040 returned in the response if the DOTS server has accepted the 1041 mitigation efficacy update. If the DOTS server does not find the 1042 mitigation-id parameter value conveyed in the PUT request in its 1043 configuration data then the server MAY accept the mitigation request 1044 and will try to mitigate the attack, resulting in a 2.01 (Created) 1045 Response Code. The 5.xx response codes are returned if the DOTS 1046 server has erred or is incapable of performing the mitigation. 1048 5.4. DOTS Signal Channel Session Configuration 1050 The DOTS client can negotiate, configure and retrieve the DOTS signal 1051 channel session behavior. The DOTS signal channel can be used, for 1052 example, to configure the following: 1054 a. Heartbeat timeout: DOTS agents regularly send heartbeats (Ping/ 1055 Pong) to each other after mutual authentication in order to keep 1056 the DOTS signal channel open, heartbeat timeout is the time to 1057 wait for a Pong in milliseconds. 1058 b. Acceptable signal loss ratio: Maximum retransmissions, 1059 retransmission timeout value and other message transmission 1060 parameters for the DOTS signal channel. 1062 Reliability is provided to requests and responses by marking them as 1063 Confirmable (CON) messages. DOTS signal channel session 1064 configuration requests and responses are marked as Confirmable (CON) 1065 messages. As explained in Section 2.1 of [RFC7252], a Confirmable 1066 message is retransmitted using a default timeout and exponential 1067 back-off between retransmissions, until the DOTS server sends an 1068 Acknowledgement message (ACK) with the same Message ID conveyed from 1069 the DOTS client. Message transmission parameters are defined in 1070 Section 4.8 of [RFC7252]. Reliability is provided to the responses 1071 by marking them as Confirmable (CON) messages. The DOTS server can 1072 either piggyback the response in the acknowledgement message or if 1073 the DOTS server is not able to respond immediately to a request 1074 carried in a Confirmable message, it simply responds with an Empty 1075 Acknowledgement message so that the DOTS client can stop 1076 retransmitting the request. Empty Acknowledgement message is 1077 explained in Section 2.2 of [RFC7252]. When the response is ready, 1078 the server sends it in a new Confirmable message which then in turn 1079 needs to be acknowledged by the DOTS client (see Sections 5.2.1 and 1080 Sections 5.2.2 in [RFC7252]). Requests and responses exchanged 1081 between DOTS agents during peacetime are marked as Confirmable 1082 messages. 1084 Implementation Note: A DOTS client that receives a response in a CON 1085 message may want to clean up the message state right after sending 1086 the ACK. If that ACK is lost and the DOTS server retransmits the 1087 CON, the DOTS client may no longer have any state to which to 1088 correlate this response, making the retransmission an unexpected 1089 message; the DOTS client will send a Reset message so it does not 1090 receive any more retransmissions. This behavior is normal and not an 1091 indication of an error (see Section 5.3.2 in [RFC7252] for more 1092 details). 1094 5.4.1. Discover Acceptable Configuration Parameters 1096 A GET request is used to obtain acceptable configuration parameters 1097 on the DOTS server for DOTS signal channel session configuration. 1098 Figure 12 shows how to obtain acceptable configuration parameters for 1099 the server. 1101 Header: GET (Code=0.01) 1102 Uri-Host: "host" 1103 Uri-Path: "version" 1104 Uri-Path: "dots-signal" 1105 Uri-Path: "config" 1107 Figure 12: GET to retrieve configuration 1109 The DOTS server in the 2.05 (Content) response conveys the minimum 1110 and maximum attribute values acceptable by the DOTS server. 1112 Content-Format: "application/cbor" 1113 { 1114 "heartbeat-timeout": {"MinValue": integer, "MaxValue" : integer}, 1115 "max-retransmit": {"MinValue": integer, "MaxValue" : integer}, 1116 "ack-timeout": {"MinValue": integer, "MaxValue" : integer}, 1117 "ack-random-factor": {"MinValue": number, "MaxValue" : number} 1118 } 1120 Figure 13: GET response body 1122 5.4.2. Convey DOTS Signal Channel Session Configuration 1124 A POST request is used to convey the configuration parameters for the 1125 signaling channel (e.g., heartbeat timeout, maximum retransmissions 1126 etc). Message transmission parameters for CoAP are defined in 1127 Section 4.8 of [RFC7252]. If the DOTS agent wishes to change the 1128 default values of message transmission parameters then it should 1129 follow the guidance given in Section 4.8.1 of [RFC7252]. The DOTS 1130 agents MUST use the negotiated values for message transmission 1131 parameters and default values for non-negotiated message transmission 1132 parameters. The signaling channel session configuration is 1133 applicable to a single DOTS signal channel session between the DOTS 1134 agents. 1136 Header: POST (Code=0.02) 1137 Uri-Host: "host" 1138 Uri-Path: "version" 1139 Uri-Path: "dots-signal" 1140 Uri-Path: "config" 1141 Content-Format: "application/cbor" 1142 { 1143 "signal-config": { 1144 "session-id": integer, 1145 "heartbeat-timeout": integer, 1146 "max-retransmit": integer, 1147 "ack-timeout": integer, 1148 "ack-random-factor": number 1149 } 1150 } 1152 Figure 14: POST to convey the DOTS signal channel session 1153 configuration data. 1155 The parameters are described below: 1157 session-id: Identifier for the DOTS signal channel session 1158 configuration data represented as an integer. This identifier 1159 MUST be generated by the DOTS client. This document does not make 1160 any assumption about how this identifier is generated. This is a 1161 mandatory attribute. 1162 heartbeat-timeout: Heartbeat timeout is the time to wait for a 1163 response in milliseconds to check the DOTS peer health. This is 1164 an optional attribute. 1165 max-retransmit: Maximum number of retransmissions for a message 1166 (referred to as MAX_RETRANSMIT parameter in CoAP). This is an 1167 optional attribute. 1169 ack-timeout: Timeout value in seconds used to calculate the intial 1170 retransmission timeout value (referred to as ACK_TIMEOUT parameter 1171 in CoAP). This is an optional attribute. 1172 ack-random-factor: Random factor used to influence the timing of 1173 retransmissions (referred to as ACK_RANDOM_FACTOR parameter in 1174 CoAP). This is an optional attribute. 1176 In the POST request at least one of the attributes heartbeat-timeout 1177 or max-retransmit or ack-timeout or ack-random-factor MUST be 1178 present. The POST request with higher numeric session-id value over- 1179 rides the DOTS signal channel session configuration data installed by 1180 a POST request with a lower numeric session-id value. 1182 Figure 15 shows a POST request example to convey the configuration 1183 parameters for the DOTS signal channel. 1185 Header: POST (Code=0.02) 1186 Uri-Host: "www.example.com" 1187 Uri-Path: "v1" 1188 Uri-Path: "dots-signal" 1189 Uri-Path: "config" 1190 Content-Format: "application/cbor" 1191 { 1192 "signal-config": { 1193 "session-id": 1234534333242, 1194 "heartbeat-timeout": 30, 1195 "max-retransmit": 7, 1196 "ack-timeout": 5, 1197 "ack-random-factor": 1.5 1198 } 1199 } 1201 Figure 15: POST to convey the configuration parameters 1203 The DOTS server indicates the result of processing the POST request 1204 using CoAP response codes. The CoAP response will include the CBOR 1205 body received in the request. Response code 2.01 (Created) will be 1206 returned in the response if the DOTS server has accepted the 1207 configuration parameters. If the request is missing one or more 1208 mandatory attributes then 4.00 (Bad Request) will be returned in the 1209 response or if the request contains invalid or unknown parameters 1210 then 4.02 (Invalid query) will be returned in the response. Response 1211 code 4.22 (Unprocessable Entity) will be returned in the response if 1212 any of the heartbeat-timeout, max-retransmit, target-protocol, ack- 1213 timeout and ack-random-factor attribute values is not acceptable to 1214 the DOTS server. The DOTS server in the error response conveys the 1215 minimum and maximum attribute values acceptable by the DOTS server. 1217 The DOTS client can re-try and send the POST request with updated 1218 attribute values acceptable to the DOTS server. 1220 Content-Format: "application/cbor" 1221 { 1222 "heartbeat-timeout": {"MinValue": 15, "MaxValue" : 60}, 1223 "max-retransmit": {"MinValue": 3, "MaxValue" : 15}, 1224 "ack-timeout": {"MinValue": 1, "MaxValue" : 30}, 1225 "ack-random-factor": {"MinValue": 1.0, "MaxValue" : 4.0} 1226 } 1228 Figure 16: Error response body 1230 5.4.3. Delete DOTS Signal Channel Session Configuration 1232 A DELETE request is used to delete the installed DOTS signal channel 1233 session configuration data (Figure 17). 1235 Header: DELETE (Code=0.04) 1236 Uri-Host: "host" 1237 Uri-Path: "version" 1238 Uri-Path: "dots-signal" 1239 Uri-Path: "config" 1240 Content-Format: "application/cbor" 1241 { 1242 "signal-config": { 1243 "session-id": integer 1244 } 1245 } 1247 Figure 17: DELETE configuration 1249 If the DOTS server does not find the session-id parameter value 1250 conveyed in the DELETE request in its configuration data, then it 1251 responds with a 4.04 (Not Found) error response code. The DOTS 1252 server successfully acknowledges a DOTS client's request to remove 1253 the DOTS signal channel session configuration using 2.02 (Deleted) 1254 response code. 1256 5.4.4. Retrieving DOTS Signal Channel Session Configuration 1258 A GET request is used to retrieve the installed DOTS signal channel 1259 session configuration data from a DOTS server. Figure 18 shows how 1260 to retrieve the DOTS signal channel session configuration data. 1262 Header: GET (Code=0.01) 1263 Uri-Host: "host" 1264 Uri-Path: "version" 1265 Uri-Path: "dots-signal" 1266 Uri-Path: "config" 1267 Content-Format: "application/cbor" 1268 { 1269 "signal-config": { 1270 "session-id": integer 1271 } 1272 } 1274 Figure 18: GET to retrieve configuration 1276 5.5. Redirected Signaling 1278 Redirected Signaling is discussed in detail in Section 3.2.2 of 1279 [I-D.ietf-dots-architecture]. If the DOTS server wants to redirect 1280 the DOTS client to an alternative DOTS server for a signaling session 1281 then the response code 3.00 (alternate server) will be returned in 1282 the response to the client. The DOTS server can return the error 1283 response code 3.00 in response to a POST or PUT request from the DOTS 1284 client or convey the error response code 3.00 in a unidirectional 1285 notification response from the DOTS server. 1287 The DOTS server in the error response conveys the alternate DOTS 1288 server FQDN, and the alternate DOTS server IP addresses and TTL (time 1289 to live) values in the CBOR body. 1291 { 1292 "alt-server": "string", 1293 "alt-server-record": [ 1294 { 1295 "addr": "string", 1296 "TTL" : integer, 1297 } 1298 ] 1299 } 1301 Figure 19: Error response body 1303 The parameters are described below: 1305 alt-server: FQDN of alternate DOTS server. 1306 addr: IP address of alternate DOTS server. 1307 TTL: Time to live represented as an integer number of seconds. 1309 Figure 20 shows a 3.00 response example to convey the DOTS alternate 1310 server www.example-alt.com, its IP addresses 2002:db8:6401::1 and 1311 2002:db8:6401::2, and TTL values 3600 and 1800. 1313 { 1315 "alt-server": "www.example-alt.com", 1316 "alt-server-record": [ 1317 { 1318 "TTL" : 3600, 1319 "addr": "2002:db8:6401::1" 1320 }, 1321 { 1322 "TTL" : 1800, 1323 "addr": "2002:db8:6401::2" 1324 } 1325 ] 1326 } 1328 Figure 20: Example of error response body 1330 When the DOTS client receives 3.00 response, it considers the current 1331 request as having failed, but SHOULD try the request with the 1332 alternate DOTS server. During a DDOS attack, the DNS server may be 1333 subjected to DDOS attack, alternate DOTS server IP addresses conveyed 1334 in the 3.00 response help the DOTS client to skip DNS lookup of the 1335 alternate DOTS server and can try to establish UDP or TCP session 1336 with the alternate DOTS server IP addresses. The DOTS client SHOULD 1337 implement DNS64 function to handle the scenario where IPv6-only DOTS 1338 client communicates with IPv4-only alternate DOTS server. 1340 5.6. Heartbeat Mechanism 1342 While the communication between the DOTS agents is quiescent, the 1343 DOTS client will probe the DOTS server to ensure it has maintained 1344 cryptographic state and vice versa. Such probes can also keep alive 1345 firewall or NAT bindings. This probing reduces the frequency of 1346 needing a new handshake when a DOTS signal needs to be conveyed to 1347 the DOTS server. In DOTS over UDP, heartbeat messages can be 1348 exchanged between the DOTS agents using the "COAP ping" mechanism 1349 (Section 4.2 in [RFC7252]). The DOTS agent sends an Empty 1350 Confirmable message and the peer DOTS agent will respond by sending 1351 an Reset message. In DOTS over TCP, heartbeat messages can be 1352 exchanged between the DOTS agents using the Ping and Pong messages 1353 (Section 4.4 in [I-D.ietf-core-coap-tcp-tls]). The DOTS agent sends 1354 an Ping message and the peer DOTS agent will respond by sending an 1355 single Pong message. 1357 6. Mapping parameters to CBOR 1359 All parameters in DOTS signal channel are mapped to CBOR types as 1360 follows and are given an integer key value to save space. 1362 /--------------------+------------------------+--------------------------\ 1363 | Parameter name | CBOR key | CBOR major type of value | 1364 |--------------------+------------------------+--------------------------| 1365 | mitigation-scope | 1 | 5 (map) | 1366 | scope | 2 | 5 (map) | 1367 | mitigation-id | 3 | 0 (unsigned) | 1368 | target-ip | 4 | 4 (array) | 1369 | target-port-range | 5 | 4 | 1370 | lower-port | 6 | 0 | 1371 | upper-port | 7 | 0 | 1372 | target-protocol | 8 | 4 | 1373 | FQDN | 9 | 4 | 1374 | URI | 10 | 4 | 1375 | alias | 11 | 4 | 1376 | lifetime | 12 | 0 | 1377 | attack-status | 13 | 0 | 1378 | signal-config | 14 | 5 | 1379 | heartbeat-timeout | 15 | 0 | 1380 | max-retransmit | 16 | 0 | 1381 | ack-timeout | 17 | 0 | 1382 | ack-random-factor | 18 | 7 | 1383 | MinValue | 19 | 0 | 1384 | MaxValue | 20 | 0 | 1385 | status | 21 | 0 | 1386 | bytes-dropped | 22 | 0 | 1387 | bps-dropped | 23 | 0 | 1388 | pkts-dropped | 24 | 0 | 1389 | pps-dropped | 25 | 0 | 1390 | session-id | 26 | 0 | 1391 \--------------------+------------------------+--------------------------/ 1393 Figure 21: CBOR mappings used in DOTS signal channel message 1395 7. (D)TLS Protocol Profile and Performance considerations 1397 This section defines the (D)TLS protocol profile of DOTS signal 1398 channel over (D)TLS and DOTS data channel over TLS. 1400 There are known attacks on (D)TLS, such as machine-in-the-middle and 1401 protocol downgrade. These are general attacks on (D)TLS and not 1402 specific to DOTS over (D)TLS; please refer to the (D)TLS RFCs for 1403 discussion of these security issues. DOTS agents MUST adhere to the 1404 (D)TLS implementation recommendations and security considerations of 1406 [RFC7525] except with respect to (D)TLS version. Since encryption of 1407 DOTS using (D)TLS is virtually a green-field deployment DOTS agents 1408 MUST implement only (D)TLS 1.2 or later. 1410 Implementations compliant with this profile MUST implement all of the 1411 following items: 1413 o DOTS agents MUST support DTLS record replay detection (Section 3.3 1414 in [RFC6347]) to protect against replay attacks. 1415 o DOTS client can use (D)TLS session resumption without server-side 1416 state [RFC5077] to resume session and convey the DOTS signal. 1417 o Raw public keys [RFC7250] which reduce the size of the 1418 ServerHello, and can be used by servers that cannot obtain 1419 certificates (e.g., DOTS gateways on private networks). 1421 Implementations compliant with this profile SHOULD implement all of 1422 the following items to reduce the delay required to deliver a DOTS 1423 signal: 1425 o TLS False Start [RFC7918] which reduces round-trips by allowing 1426 the TLS second flight of messages (ChangeCipherSpec) to also 1427 contain the DOTS signal. 1428 o Cached Information Extension [RFC7924] which avoids transmitting 1429 the server's certificate and certificate chain if the client has 1430 cached that information from a previous TLS handshake. 1431 o TCP Fast Open [RFC7413] can reduce the number of round-trips to 1432 convey DOTS signal. 1434 7.1. MTU and Fragmentation Issues 1436 To avoid DOTS signal message fragmentation and the consequently 1437 decreased probability of message delivery, DOTS agents MUST ensure 1438 that the DTLS record MUST fit within a single datagram. If the Path 1439 MTU is not known to the DOTS server, an IP MTU of 1280 bytes SHOULD 1440 be assumed. The length of the URL MUST NOT exceed 256 bytes. If UDP 1441 is used to convey the DOTS signal messages then the DOTS client must 1442 consider the amount of record expansion expected by the DTLS 1443 processing when calculating the size of CoAP message that fits within 1444 the path MTU. Path MTU MUST be greater than or equal to [CoAP 1445 message size + DTLS overhead of 13 octets + authentication overhead 1446 of the negotiated DTLS cipher suite + block padding (Section 4.1.1.1 1447 of [RFC6347]]. If the request size exceeds the Path MTU then the 1448 DOTS client MUST split the DOTS signal into separate messages, for 1449 example the list of addresses in the 'target-ip' parameter could be 1450 split into multiple lists and each list conveyed in a new POST 1451 request. 1453 Implementation Note: DOTS choice of message size parameters works 1454 well with IPv6 and with most of today's IPv4 paths. However, with 1455 IPv4, it is harder to absolutely ensure that there is no IP 1456 fragmentation. If IPv4 support on unusual networks is a 1457 consideration and path MTU is unknown, implementations may want to 1458 limit themselves to more conservative IPv4 datagram sizes such as 576 1459 bytes, as per [RFC0791] IP packets up to 576 bytes should never need 1460 to be fragmented, thus sending a maximum of 500 bytes of DOTS signal 1461 over a UDP datagram will generally avoid IP fragmentation. 1463 8. (D)TLS 1.3 considerations 1465 TLS 1.3 [I-D.ietf-tls-tls13] provides critical latency improvements 1466 for connection establishment over TLS 1.2. The DTLS 1.3 protocol 1467 [I-D.rescorla-tls-dtls13] is based on the TLS 1.3 protocol and 1468 provides equivalent security guarantees. (D)TLS 1.3 provides two 1469 basic handshake modes of interest to DOTS signal channel: 1471 o Absent packet loss, a full handshake in which the DOTS client is 1472 able to send the DOTS signal message after one round trip and the 1473 DOTS server immediately after receiving the first DOTS signal 1474 message from the client. 1475 o 0-RTT mode in which the DOTS client can authenticate itself and 1476 send DOTS signal message on its first flight, thus reducing 1477 handshake latency. 0-RTT only works if the DOTS client has 1478 previously communicated with that DOTS server, which is very 1479 likely with the DOTS signal channel. The DOTS client SHOULD 1480 establish a (D)TLS session with the DOTS server during peacetime 1481 and share a PSK. During DDOS attack, the DOTS client can use the 1482 (D)TLS session to convey the DOTS signal message and if there is 1483 no response from the server after multiple re-tries then the DOTS 1484 client can resume the (D)TLS session in 0-RTT mode using PSK. A 1485 simplified TLS 1.3 handshake with 0-RTT DOTS signal message 1486 exchange is shown in Figure 22. 1488 DOTS Client DOTS Server 1490 ClientHello 1491 (Finished) 1492 (0-RTT DOTS signal message) 1493 (end_of_early_data) --------> 1494 ServerHello 1495 {EncryptedExtensions} 1496 {ServerConfiguration} 1497 {Certificate} 1498 {CertificateVerify} 1499 {Finished} 1500 <-------- [DOTS signal message] 1501 {Finished} --------> 1503 [DOTS signal message] <-------> [DOTS signal message] 1505 Figure 22: TLS 1.3 handshake with 0-RTT 1507 9. Mutual Authentication of DOTS Agents & Authorization of DOTS Clients 1509 (D)TLS based on client certificate can be used for mutual 1510 authentication between DOTS agents. If a DOTS gateway is involved, 1511 DOTS clients and DOTS gateway MUST perform mutual authentication; 1512 only authorized DOTS clients are allowed to send DOTS signals to a 1513 DOTS gateway. DOTS gateway and DOTS server MUST perform mutual 1514 authentication; DOTS server only allows DOTS signals from authorized 1515 DOTS gateway, creating a two-link chain of transitive authentication 1516 between the DOTS client and the DOTS server. 1518 +-------------------------------------------------+ 1519 | example.com domain +---------+ | 1520 | | AAA | | 1521 | +---------------+ | Server | | 1522 | | Application | +------+--+ | 1523 | | server + ^ 1524 | | (DOTS client) |<-----------------+ | | 1525 | +---------------+ + | | example.net domain 1526 | V V | 1527 | +-------------+ | +---------------+ 1528 | +--------------+ | | | | | 1529 | | Guest +<-----x----->+ +<---------------->+ DOTS | 1530 | | (DOTS client)| | DOTS | | | Server | 1531 | +--------------+ | Gateway | | | | 1532 | +----+--------+ | +---------------+ 1533 | ^ | 1534 | | | 1535 | +----------------+ | | 1536 | | DDOS detector | | | 1537 | | (DOTS client) +<--------------+ | 1538 | +----------------+ | 1539 | | 1540 +-------------------------------------------------+ 1542 Figure 23: Example of Authentication and Authorization of DOTS Agents 1544 In the example depicted in Figure 23, the DOTS gateway and DOTS 1545 clients within the 'example.com' domain mutually authenticate with 1546 each other. After the DOTS gateway validates the identity of a DOTS 1547 client, it communicates with the AAA server in the 'example.com' 1548 domain to determine if the DOTS client is authorized to request DDOS 1549 mitigation. If the DOTS client is not authorized, a 4.01 1550 (Unauthorized) is returned in the response to the DOTS client. In 1551 this example, the DOTS gateway only allows the application server and 1552 DDOS detector to request DDOS mitigation, but does not permit the 1553 user of type 'guest' to request DDOS mitigation. 1555 Also, DOTS gateway and DOTS server MUST perform mutual authentication 1556 using certificates. A DOTS server will only allow a DOTS gateway 1557 with a certificate for a particular domain to request mitigation for 1558 that domain. In reference to Figure 23, the DOTS server only allows 1559 the DOTS gateway to request mitigation for 'example.com' domain and 1560 not for other domains. 1562 10. IANA Considerations 1564 This specification registers new parameters for DOTS signal channel 1565 and establishes registries for mappings to CBOR. 1567 10.1. DOTS signal channel CBOR Mappings Registry 1569 A new registry will be requested from IANA, entitled "DOTS signal 1570 channel CBOR Mappings Registry". The registry is to be created as 1571 Expert Review Required. 1573 10.1.1. Registration Template 1575 Parameter name: 1576 Parameter names (e.g., "target_ip") in the DOTS signal channel. 1577 CBOR Key Value: 1578 Key value for the parameter. The key value MUST be an integer in 1579 the range of 1 to 65536. The key values in the range of 32768 to 1580 65536 are assigned for Vendor-Specific parameters. 1581 CBOR Major Type: 1582 CBOR Major type and optional tag for the claim. 1583 Change Controller: 1584 For Standards Track RFCs, list the "IESG". For others, give the 1585 name of the responsible party. Other details (e.g., postal 1586 address, email address, home page URI) may also be included. 1587 Specification Document(s): 1588 Reference to the document or documents that specify the parameter, 1589 preferably including URIs that can be used to retrieve copies of 1590 the documents. An indication of the relevant sections may also be 1591 included but is not required. 1593 10.1.2. Initial Registry Contents 1595 o Parameter Name: "mitigation-scope" 1596 o CBOR Key Value: 1 1597 o CBOR Major Type: 5 1598 o Change Controller: IESG 1599 o Specification Document(s): this document 1601 o Parameter Name: "scope" 1602 o CBOR Key Value: 2 1603 o CBOR Major Type: 5 1604 o Change Controller: IESG 1605 o Specification Document(s): this document 1607 o Parameter Name: "mitigation-id" 1608 o CBOR Key Value: 3 1609 o CBOR Major Type: 0 1610 o Change Controller: IESG 1611 o Specification Document(s): this document 1613 o Parameter Name:target-ip 1614 o CBOR Key Value: 4 1615 o CBOR Major Type: 4 1616 o Change Controller: IESG 1617 o Specification Document(s): this document 1619 o Parameter Name: target-port-range 1620 o CBOR Key Value: 5 1621 o CBOR Major Type: 4 1622 o Change Controller: IESG 1623 o Specification Document(s): this document 1625 o Parameter Name: "lower-port" 1626 o CBOR Key Value: 6 1627 o CBOR Major Type: 0 1628 o Change Controller: IESG 1629 o Specification Document(s): this document 1631 o Parameter Name: "upper-port" 1632 o CBOR Key Value: 7 1633 o CBOR Major Type: 0 1634 o Change Controller: IESG 1635 o Specification Document(s): this document 1637 o Parameter Name: target-protocol 1638 o CBOR Key Value: 8 1639 o CBOR Major Type: 4 1640 o Change Controller: IESG 1641 o Specification Document(s): this document 1643 o Parameter Name: "FQDN" 1644 o CBOR Key Value: 9 1645 o CBOR Major Type: 4 1646 o Change Controller: IESG 1647 o Specification Document(s): this document 1649 o Parameter Name: "URI" 1650 o CBOR Key Value: 10 1651 o CBOR Major Type: 4 1652 o Change Controller: IESG 1653 o Specification Document(s): this document 1655 o Parameter Name: alias 1656 o CBOR Key Value: 11 1657 o CBOR Major Type: 4 1658 o Change Controller: IESG 1659 o Specification Document(s): this document 1661 o Parameter Name: "lifetime" 1662 o CBOR Key Value: 12 1663 o CBOR Major Type: 0 1664 o Change Controller: IESG 1665 o Specification Document(s): this document 1667 o Parameter Name: attack-status 1668 o CBOR Key Value: 13 1669 o CBOR Major Type: 0 1670 o Change Controller: IESG 1671 o Specification Document(s): this document 1673 o Parameter Name: signal-config 1674 o CBOR Key Value: 14 1675 o CBOR Major Type: 5 1676 o Change Controller: IESG 1677 o Specification Document(s): this document 1679 o Parameter Name: heartbeat-timeout 1680 o CBOR Key Value: 15 1681 o CBOR Major Type: 0 1682 o Change Controller: IESG 1683 o Specification Document(s): this document 1685 o Parameter Name: max-retransmit 1686 o CBOR Key Value: 16 1687 o CBOR Major Type: 0 1688 o Change Controller: IESG 1689 o Specification Document(s): this document 1691 o Parameter Name: ack-timeout 1692 o CBOR Key Value: 17 1693 o CBOR Major Type: 0 1694 o Change Controller: IESG 1695 o Specification Document(s): this document 1697 o Parameter Name: ack-random-factor 1698 o CBOR Key Value: 18 1699 o CBOR Major Type: 7 1700 o Change Controller: IESG 1701 o Specification Document(s): this document 1703 o Parameter Name: MinValue 1704 o CBOR Key Value: 19 1705 o CBOR Major Type: 0 1706 o Change Controller: IESG 1707 o Specification Document(s): this document 1709 o Parameter Name: MaxValue 1710 o CBOR Key Value: 20 1711 o CBOR Major Type: 0 1712 o Change Controller: IESG 1713 o Specification Document(s): this document 1715 o Parameter Name: status 1716 o CBOR Key Value: 21 1717 o CBOR Major Type: 0 1718 o Change Controller: IESG 1719 o Specification Document(s): this document 1721 o Parameter Name: bytes-dropped 1722 o CBOR Key Value: 22 1723 o CBOR Major Type: 0 1724 o Change Controller: IESG 1725 o Specification Document(s): this document 1727 o Parameter Name: bps-dropped 1728 o CBOR Key Value: 23 1729 o CBOR Major Type: 0 1730 o Change Controller: IESG 1731 o Specification Document(s): this document 1733 o Parameter Name: pkts-dropped 1734 o CBOR Key Value: 24 1735 o CBOR Major Type: 0 1736 o Change Controller: IESG 1737 o Specification Document(s): this document 1739 o Parameter Name: pps-dropped 1740 o CBOR Key Value: 25 1741 o CBOR Major Type: 0 1742 o Change Controller: IESG 1743 o Specification Document(s): this document 1745 o Parameter Name: session-id 1746 o CBOR Key Value: 26 1747 o CBOR Major Type: 0 1748 o Change Controller: IESG 1749 o Specification Document(s): this document 1751 11. Implementation Status 1753 [Note to RFC Editor: Please remove this section and reference to 1754 [RFC6982] prior to publication.] 1756 This section records the status of known implementations of the 1757 protocol defined by this specification at the time of posting of this 1758 Internet-Draft, and is based on a proposal described in [RFC6982]. 1759 The description of implementations in this section is intended to 1760 assist the IETF in its decision processes in progressing drafts to 1761 RFCs. Please note that the listing of any individual implementation 1762 here does not imply endorsement by the IETF. Furthermore, no effort 1763 has been spent to verify the information presented here that was 1764 supplied by IETF contributors. This is not intended as, and must not 1765 be construed to be, a catalog of available implementations or their 1766 features. Readers are advised to note that other implementations may 1767 exist. 1769 According to [RFC6982], "this will allow reviewers and working groups 1770 to assign due consideration to documents that have the benefit of 1771 running code, which may serve as evidence of valuable experimentation 1772 and feedback that have made the implemented protocols more mature. 1773 It is up to the individual working groups to use this information as 1774 they see fit". 1776 11.1. nttdots 1778 Organization: NTT Communication is developing a DOTS client and 1779 DOTS server software based on DOTS signal channel specified in 1780 this draft. It will be open-sourced. 1781 Description: Early implementation of DOTS protocol. It is aimed to 1782 implement a full DOTS protocol spec in accordance with maturing of 1783 DOTS protocol itself. 1784 Implementation: To be open-sourced. 1785 Level of maturity: It is a early implementation of DOTS protocol. 1786 Messaging between DOTS clients and DOTS servers has been tested. 1787 Level of maturity will increase in accordance with maturing of 1788 DOTS protocol itself. 1789 Coverage: Capability of DOTS client: sending DOTS messages to the 1790 DOTS server in CoAP over DTLS as dots-signal. Capability of DOTS 1791 server: receiving dots-signal, validating received dots-signal, 1792 starting mitigation by handing over the dots-signal to DDOS 1793 mitigator. 1794 Licensing: It will be open-sourced with BSD 3-clause license. 1795 Implementation experience: It is implemented in Go-lang. Core 1796 specification of signaling is mature to be implemented, however, 1797 finding good libraries(like DTLS, CoAP) is rather difficult. 1798 Contact: Kaname Nishizuka 1800 12. Security Considerations 1802 Authenticated encryption MUST be used for data confidentiality and 1803 message integrity. (D)TLS based on client certificate MUST be used 1804 for mutual authentication. The interaction between the DOTS agents 1805 requires Datagram Transport Layer Security (DTLS) and Transport Layer 1806 Security (TLS) with a cipher suite offering confidentiality 1807 protection and the guidance given in [RFC7525] MUST be followed to 1808 avoid attacks on (D)TLS. 1810 A single DOTS signal channel between DOTS agents can be used to 1811 exchange multiple DOTS signal messages. To reduce DOTS client and 1812 DOTS server workload, DOTS client SHOULD re-use the (D)TLS session. 1814 If TCP is used between DOTS agents, an attacker may be able to inject 1815 RST packets, bogus application segments, etc., regardless of whether 1816 TLS authentication is used. Because the application data is TLS 1817 protected, this will not result in the application receiving bogus 1818 data, but it will constitute a DoS on the connection. This attack 1819 can be countered by using TCP-AO [RFC5925]. If TCP-AO is used, then 1820 any bogus packets injected by an attacker will be rejected by the 1821 TCP-AO integrity check and therefore will never reach the TLS layer. 1823 Special care should be taken in order to ensure that the activation 1824 of the proposed mechanism won't have an impact on the stability of 1825 the network (including connectivity and services delivered over that 1826 network). 1828 Involved functional elements in the cooperation system must establish 1829 exchange instructions and notification over a secure and 1830 authenticated channel. Adequate filters can be enforced to avoid 1831 that nodes outside a trusted domain can inject request such as 1832 deleting filtering rules. Nevertheless, attacks can be initiated 1833 from within the trusted domain if an entity has been corrupted. 1834 Adequate means to monitor trusted nodes should also be enabled. 1836 13. Contributors 1838 The following individuals have contributed to this document: 1840 Mike Geller Cisco Systems, Inc. 3250 Florida 33309 USA Email: 1841 mgeller@cisco.com 1843 Robert Moskowitz HTT Consulting Oak Park, MI 42837 United States 1844 Email: rgm@htt-consult.com 1846 Dan Wing Email: dwing-ietf@fuggles.com 1848 14. Acknowledgements 1850 Thanks to Christian Jacquenet, Roland Dobbins, Andrew Mortensen, 1851 Roman D. Danyliw, Michael Richardson, Ehud Doron, Kaname Nishizuka, 1852 Dave Dolson and Gilbert Clark for the discussion and comments. 1854 15. References 1856 15.1. Normative References 1858 [I-D.ietf-core-coap-tcp-tls] 1859 Bormann, C., Lemay, S., Tschofenig, H., Hartke, K., 1860 Silverajan, B., and B. Raymor, "CoAP (Constrained 1861 Application Protocol) over TCP, TLS, and WebSockets", 1862 draft-ietf-core-coap-tcp-tls-07 (work in progress), March 1863 2017. 1865 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1866 Requirement Levels", BCP 14, RFC 2119, 1867 DOI 10.17487/RFC2119, March 1997, 1868 . 1870 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1871 (TLS) Protocol Version 1.2", RFC 5246, 1872 DOI 10.17487/RFC5246, August 2008, 1873 . 1875 [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP 1876 Authentication Option", RFC 5925, DOI 10.17487/RFC5925, 1877 June 2010, . 1879 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 1880 Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, 1881 January 2012, . 1883 [RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J., 1884 Weiler, S., and T. Kivinen, "Using Raw Public Keys in 1885 Transport Layer Security (TLS) and Datagram Transport 1886 Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250, 1887 June 2014, . 1889 [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained 1890 Application Protocol (CoAP)", RFC 7252, 1891 DOI 10.17487/RFC7252, June 2014, 1892 . 1894 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 1895 "Recommendations for Secure Use of Transport Layer 1896 Security (TLS) and Datagram Transport Layer Security 1897 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 1898 2015, . 1900 [RFC7641] Hartke, K., "Observing Resources in the Constrained 1901 Application Protocol (CoAP)", RFC 7641, 1902 DOI 10.17487/RFC7641, September 2015, 1903 . 1905 15.2. Informative References 1907 [I-D.ietf-core-comi] 1908 Stok, P., Bierman, A., Veillette, M., and A. Pelov, "CoAP 1909 Management Interface", draft-ietf-core-comi-00 (work in 1910 progress), January 2017. 1912 [I-D.ietf-core-yang-cbor] 1913 Veillette, M., Pelov, A., Somaraju, A., Turner, R., and A. 1914 Minaburo, "CBOR Encoding of Data Modeled with YANG", 1915 draft-ietf-core-yang-cbor-04 (work in progress), February 1916 2017. 1918 [I-D.ietf-dots-architecture] 1919 Mortensen, A., Andreasen, F., Reddy, T., 1920 christopher_gray3@cable.comcast.com, c., Compton, R., and 1921 N. Teague, "Distributed-Denial-of-Service Open Threat 1922 Signaling (DOTS) Architecture", draft-ietf-dots- 1923 architecture-01 (work in progress), October 2016. 1925 [I-D.ietf-dots-requirements] 1926 Mortensen, A., Moskowitz, R., and T. Reddy, "Distributed 1927 Denial of Service (DDoS) Open Threat Signaling 1928 Requirements", draft-ietf-dots-requirements-04 (work in 1929 progress), March 2017. 1931 [I-D.ietf-dots-use-cases] 1932 Dobbins, R., Fouant, S., Migault, D., Moskowitz, R., 1933 Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS 1934 Open Threat Signaling", draft-ietf-dots-use-cases-04 (work 1935 in progress), March 2017. 1937 [I-D.ietf-tls-tls13] 1938 Rescorla, E., "The Transport Layer Security (TLS) Protocol 1939 Version 1.3", draft-ietf-tls-tls13-19 (work in progress), 1940 March 2017. 1942 [I-D.ietf-tsvwg-rfc5405bis] 1943 Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage 1944 Guidelines", draft-ietf-tsvwg-rfc5405bis-19 (work in 1945 progress), October 2016. 1947 [I-D.reddy-dots-data-channel] 1948 Reddy, T., Boucadair, M., Nishizuka, K., Xia, L., Patil, 1949 P., Mortensen, A., and N. Teague, "Distributed Denial-of- 1950 Service Open Threat Signaling (DOTS) Data Channel", draft- 1951 reddy-dots-data-channel-05 (work in progress), March 2017. 1953 [I-D.rescorla-tls-dtls13] 1954 Rescorla, E., Tschofenig, H., and N. Modadugu, "The 1955 Datagram Transport Layer Security (DTLS) Protocol Version 1956 1.3", draft-rescorla-tls-dtls13-01 (work in progress), 1957 March 2017. 1959 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1960 DOI 10.17487/RFC0791, September 1981, 1961 . 1963 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 1964 (CIDR): The Internet Address Assignment and Aggregation 1965 Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August 1966 2006, . 1968 [RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet 1969 Denial-of-Service Considerations", RFC 4732, 1970 DOI 10.17487/RFC4732, December 2006, 1971 . 1973 [RFC4987] Eddy, W., "TCP SYN Flooding Attacks and Common 1974 Mitigations", RFC 4987, DOI 10.17487/RFC4987, August 2007, 1975 . 1977 [RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig, 1978 "Transport Layer Security (TLS) Session Resumption without 1979 Server-Side State", RFC 5077, DOI 10.17487/RFC5077, 1980 January 2008, . 1982 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 1983 the Network Configuration Protocol (NETCONF)", RFC 6020, 1984 DOI 10.17487/RFC6020, October 2010, 1985 . 1987 [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with 1988 Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555, April 1989 2012, . 1991 [RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown, 1992 "Default Address Selection for Internet Protocol Version 6 1993 (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012, 1994 . 1996 [RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 1997 Code: The Implementation Status Section", RFC 6982, 1998 DOI 10.17487/RFC6982, July 2013, 1999 . 2001 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 2002 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 2003 October 2013, . 2005 [RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP 2006 Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014, 2007 . 2009 [RFC7918] Langley, A., Modadugu, N., and B. Moeller, "Transport 2010 Layer Security (TLS) False Start", RFC 7918, 2011 DOI 10.17487/RFC7918, August 2016, 2012 . 2014 [RFC7924] Santesson, S. and H. Tschofenig, "Transport Layer Security 2015 (TLS) Cached Information Extension", RFC 7924, 2016 DOI 10.17487/RFC7924, July 2016, 2017 . 2019 Authors' Addresses 2021 Tirumaleswar Reddy 2022 Cisco Systems, Inc. 2023 Cessna Business Park, Varthur Hobli 2024 Sarjapur Marathalli Outer Ring Road 2025 Bangalore, Karnataka 560103 2026 India 2028 Email: kondtir@gmail.com 2030 Mohamed Boucadair 2031 Orange 2032 Rennes 35000 2033 France 2035 Email: mohamed.boucadair@orange.com 2036 Prashanth Patil 2037 Cisco Systems, Inc. 2039 Email: praspati@cisco.com 2041 Andrew Mortensen 2042 Arbor Networks, Inc. 2043 2727 S. State St 2044 Ann Arbor, MI 48104 2045 United States 2047 Email: amortensen@arbor.net 2049 Nik Teague 2050 Verisign, Inc. 2051 United States 2053 Email: nteague@verisign.com