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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: September 29, 2017 Orange 6 P. Patil 7 Cisco 8 A. Mortensen 9 Arbor Networks, Inc. 10 N. Teague 11 Verisign, Inc. 12 March 28, 2017 14 Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal 15 Channel 16 draft-reddy-dots-signal-channel-10 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 September 29, 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 . . . . . . . . . . 22 77 5.4. DOTS Signal Channel Session Configuration . . . . . . . . 24 78 5.4.1. Discover Acceptable Configuration Parameters . . . . 25 79 5.4.2. Convey DOTS Signal Channel Session Configuration . . 26 80 5.4.3. Delete DOTS Signal Channel Session Configuration . . 28 81 5.4.4. Retrieving DOTS Signal Channel Session Configuration 28 82 5.5. Redirected Signaling . . . . . . . . . . . . . . . . . . 29 83 5.6. Heartbeat Mechanism . . . . . . . . . . . . . . . . . . . 30 84 6. Mapping parameters to CBOR . . . . . . . . . . . . . . . . . 31 85 7. (D)TLS Protocol Profile and Performance considerations . . . 31 86 7.1. MTU and Fragmentation Issues . . . . . . . . . . . . . . 32 87 8. (D)TLS 1.3 considerations . . . . . . . . . . . . . . . . . . 33 88 9. Mutual Authentication of DOTS Agents & Authorization of DOTS 89 Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . 34 90 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 36 91 10.1. DOTS signal channel CBOR Mappings Registry . . . . . . . 36 92 10.1.1. Registration Template . . . . . . . . . . . . . . . 36 93 10.1.2. Initial Registry Contents . . . . . . . . . . . . . 36 94 11. Implementation Status . . . . . . . . . . . . . . . . . . . . 39 95 11.1. nttdots . . . . . . . . . . . . . . . . . . . . . . . . 40 96 12. Security Considerations . . . . . . . . . . . . . . . . . . . 40 97 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 41 98 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 41 99 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 42 100 15.1. Normative References . . . . . . . . . . . . . . . . . . 42 101 15.2. Informative References . . . . . . . . . . . . . . . . . 43 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 45 104 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* [policy-id] 347 +--rw policy-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 policy-id; 385 description "Identifier for the mitigation request"; 386 leaf policy-id { 387 type int32; 388 description "policy 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 policy-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 policy-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 "policy-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 policy-id: Identifier for the mitigation request represented using 587 an integer. This identifier MUST be unique for each mitigation 588 request bound to the DOTS client, i.e., the policy-id parameter 589 value in the mitigation request needs to be unique relative to the 590 policy-id parameter values of active mitigation requests conveyed 591 from the DOTS client to the DOTS server. This identifier MUST be 592 generated by the DOTS client. This document does not make any 593 assumption about how this identifier is generated. This is a 594 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 (see Section 3.1.1 in 614 [I-D.reddy-dots-data-channel]). This is an optional attribute. 615 lifetime: Lifetime of the mitigation request in seconds. Upon the 616 expiry of this lifetime, and if the request is not refreshed, the 617 mitigation request is removed. The request can be refreshed by 618 sending the same request again. The default lifetime of the 619 mitigation request is 3600 seconds (60 minutes) -- this value was 620 chosen to be long enough so that refreshing is not typically a 621 burden on the DOTS client, while expiring the request where the 622 client has unexpectedly quit in a timely manner. A lifetime of 623 zero indicates indefinite lifetime for the mitigation request. 624 The server MUST always indicate the actual lifetime in the 625 response and the remaining lifetime in status messages sent to the 626 client. This is an optional attribute in the request. 628 The CBOR key values for the parameters are defined in Section 6. The 629 IANA Considerations section defines how the CBOR key values can be 630 allocated to standards bodies and vendors. In the PUT request at 631 least one of the attributes target-ip or target-prefix or FQDN or URI 632 or alias MUST be present. DOTS agents can safely ignore Vendor- 633 Specific parameters they don't understand. The relative order of two 634 mitigation requests from a DOTS client is determined by comparing 635 their respective policy-id values. If two mitigation requests have 636 overlapping mitigation scopes the mitigation request with higher 637 numeric policy-id value will override the mitigation request with a 638 lower numeric policy-id value. The Uri-Path option carries a major 639 and minor version nomenclature to manage versioning and DOTS signal 640 channel in this specification uses v1 major version. 642 In both DOTS signal and data channel sessions, the DOTS client MUST 643 authenticate itself to the DOTS server (Section 9). The DOTS server 644 couples the DOTS signal and data channel sessions using the DOTS 645 client identity, so the DOTS server can validate whether the aliases 646 conveyed in the mitigation request were indeed created by the same 647 DOTS client using the DOTS data channel session. If the aliases were 648 not created by the DOTS client then the DOTS server returns 4.00 (Bad 649 Request) in the response. The DOTS server couples the DOTS signal 650 channel sessions using the DOTS client identity, the DOTS server uses 651 policy-id parameter value to detect duplicate mitigation requests. 653 Figure 6 shows a PUT request example to signal that ports 80, 8080, 654 and 443 on the servers 2002:db8:6401::1 and 2002:db8:6401::2 are 655 being attacked (illustrated in JSON diagnostic notation). 657 Header: PUT (Code=0.03) 658 Uri-Host: "www.example.com" 659 Uri-Path: "v1" 660 Uri-Path: "dots-signal" 661 Uri-Path: "signal" 662 Content-Format: "application/cbor" 663 { 664 "mitigation-scope": { 665 "scope": [ 666 { 667 "policy-id": 12332, 668 "target-ip": [ 669 "2002:db8:6401::1", 670 "2002:db8:6401::2" 671 ], 672 "target-port-range": [ 673 { 674 "lower-port": 80 675 }, 676 { 677 "lower-port": 443 678 }, 679 { 680 "lower-port": 8080 681 } 682 ], 683 "target-protocol": [ 684 6 686 ] 687 } 688 ] 689 } 690 } 692 The CBOR encoding format is shown below: 694 a1 # map(1) 695 01 # unsigned(1) 696 a1 # map(1) 697 02 # unsigned(2) 698 81 # array(1) 699 a4 # map(4) 700 03 # unsigned(3) 701 19 302c # unsigned(12332) 702 04 # unsigned(4) 703 82 # array(2) 704 70 # text(16) 705 323030323a6462383a363430313a3a31 # "2002:db8:6401::1" 706 70 # text(16) 707 323030323a6462383a363430313a3a32 # "2002:db8:6401::2" 708 05 # unsigned(5) 709 83 # array(3) 710 a1 # map(1) 711 06 # unsigned(6) 712 18 50 # unsigned(80) 713 a1 # map(1) 714 06 # unsigned(6) 715 19 01bb # unsigned(443) 716 a1 # map(1) 717 06 # unsigned(6) 718 19 1f90 # unsigned(8080) 719 08 # unsigned(8) 720 81 # array(1) 721 06 # unsigned(6) 723 Figure 6: POST for DOTS signal 725 The DOTS server indicates the result of processing the PUT request 726 using CoAP response codes. CoAP 2.xx codes are success. CoAP 4.xx 727 codes are some sort of invalid requests. COAP 5.xx codes are 728 returned if the DOTS server has erred or is currently unavailable to 729 provide mitigation in response to the mitigation request from the 730 DOTS client. If the DOTS server does not find the policy-id 731 parameter value conveyed in the PUT request in its configuration data 732 then the server MAY accept the mitigation request, and a 2.01 733 (Created) response is returned to the DOTS client, and the DOTS 734 server will try to mitigate the attack. If the DOTS server finds the 735 policy-id parameter value conveyed in the PUT request in its 736 configuration data then the server MAY update the mitigation request, 737 and a 2.04 (Changed) response is returned to indicate a successful 738 updation of the mitigation request. If the request is missing one or 739 more mandatory attributes, then 4.00 (Bad Request) will be returned 740 in the response or if the request contains invalid or unknown 741 parameters then 4.02 (Invalid query) will be returned in the 742 response. For responses indicating a client or server error, the 743 payload explains the error situation of the result of the requested 744 action (Section 5.5 in [RFC7252]). 746 5.3.2. Withdraw a DOTS Signal 748 A DELETE request is used to withdraw a DOTS signal from a DOTS server 749 (Figure 7). 751 Header: DELETE (Code=0.04) 752 Uri-Host: "host" 753 Uri-Path: "version" 754 Uri-Path: "dots-signal" 755 Uri-Path: "signal" 756 Content-Format: "application/cbor" 757 { 758 "mitigation-scope": { 759 "scope": [ 760 { 761 "policy-id": integer 762 } 763 ] 764 } 765 } 767 Figure 7: Withdraw DOTS signal 769 If the DOTS server does not find the policy-id parameter value 770 conveyed in the DELETE request in its configuration data, then it 771 responds with a 4.04 (Not Found) error response code. The DOTS 772 server successfully acknowledges a DOTS client's request to withdraw 773 the DOTS signal using 2.02 (Deleted) response code, and ceases 774 mitigation activity as quickly as possible. 776 To protect against route or DNS flapping caused by a client rapidly 777 toggling mitigation, and to dampen the effect of oscillating attacks, 778 DOTS servers MAY continue mitigation for a period of up to fifteen 779 minutes after acknowledging a DOTS client's withdrawal of a 780 mitigation request. During this period, DOTS server mitigation 781 status messages SHOULD indicate that mitigation is active but 782 terminating. After the fifteen-minute period elapses, the DOTS 783 server MUST treat the mitigation as terminated, as the DOTS client is 784 no longer responsible for the mitigation. 786 5.3.3. Retrieving a DOTS Signal 788 A GET request is used to retrieve information and status of a DOTS 789 signal from a DOTS server (Figure 8). If the DOTS server does not 790 find the policy-id parameter value conveyed in the GET request in its 791 configuration data, then it responds with a 4.04 (Not Found) error 792 response code. The 'c' (content) parameter and its permitted values 793 defined in [I-D.ietf-core-comi] can be used to retrieve non- 794 configuration data or configuration data or both. 796 1) To retrieve all DOTS signals signaled by the DOTS client. 798 Header: GET (Code=0.01) 799 Uri-Host: "host" 800 Uri-Path: "version" 801 Uri-Path: "dots-signal" 802 Uri-Path: "signal" 803 Observe : 0 805 2) To retrieve a specific DOTS signal signaled by the DOTS client. 806 The configuration data in the response will be formatted in the 807 same order it was processed at the DOTS server. 809 Header: GET (Code=0.01) 810 Uri-Host: "host" 811 Uri-Path: "version" 812 Uri-Path: "dots-signal" 813 Uri-Path: "signal" 814 Observe : 0 815 Content-Format: "application/cbor" 816 { 817 "mitigation-scope": { 818 "scope": [ 819 { 820 "policy-id": integer 821 } 822 ] 823 } 824 } 826 Figure 8: GET to retrieve the rules 828 Figure 9 shows a response example of all the active mitigation 829 requests associated with the DOTS client on the DOTS server and the 830 mitigation status of each mitigation request. 832 { 833 "mitigation-scope":[ 834 { 835 "scope": [ 836 { 837 "policy-id": 12332, 838 "target-protocol": [ 839 17 840 ], 841 "lifetime":1800, 842 "status":2, 843 "bytes_dropped": 134334555, 844 "bps_dropped": 43344, 845 "pkts_dropped": 333334444, 846 "pps_dropped": 432432 847 } 848 ] 849 }, 850 { 851 "scope": [ 852 { 853 "policy-id": 12333, 854 "target-protocol": [ 855 6 856 ], 857 "lifetime":1800, 858 "status":3 859 "bytes_dropped": 0, 860 "bps_dropped": 0, 861 "pkts_dropped": 0, 862 "pps_dropped": 0 863 } 864 ] 865 } 866 ] 867 } 869 Figure 9: Response body 871 The mitigation status parameters are described below. 873 bytes_dropped: The total dropped byte count for the mitigation 874 request. This is a optional attribute. 876 bps_dropped: The average dropped bytes per second for the mitigation 877 request. This is a optional attribute. 878 pkts_dropped: The total dropped packet count for the mitigation 879 request. This is a optional attribute. 880 pps_dropped: The average dropped packets per second for the 881 mitigation request. This is a optional attribute. 882 status: Status of attack mitigation. The 'status' parameter is a 883 mandatory attribute. 885 The various possible values of 'status' parameter are explained 886 below: 888 /--------------------+---------------------------------------------------\ 889 | Parameter value | Description | 890 |--------------------+---------------------------------------------------| 891 | 1 | Attack mitigation is in progress | 892 | | (e.g., changing the network path to re-route the | 893 | | inbound traffic to DOTS mitigator). | 894 +------------------------------------------------------------------------+ 895 | 2 | Attack is successfully mitigated | 896 | | (e.g., traffic is redirected to a DDOS mitigator | 897 | | and attack traffic is dropped). | 898 +------------------------------------------------------------------------+ 899 | 3 | Attack has stopped and the DOTS client | 900 | | can withdraw the mitigation request. | 901 +------------------------------------------------------------------------+ 902 | 4 | Attack has exceeded the mitigation provider | 903 | | capability. | 904 +------------------------------------------------------------------------+ 905 | 5 | DOTS client has withdrawn the mitigation request | 906 and the mitigation is active but terminating. | 907 | | | 908 \--------------------+---------------------------------------------------/ 910 The observe option defined in [RFC7641] extends the CoAP core 911 protocol with a mechanism for a CoAP client to "observe" a resource 912 on a CoAP server: the client retrieves a representation of the 913 resource and requests this representation be updated by the server as 914 long as the client is interested in the resource. A DOTS client 915 conveys the observe option set to 0 in the GET request to receive 916 unsolicited notifications of attack mitigation status from the DOTS 917 server. Unidirectional notifications within the bidirectional signal 918 channel allows unsolicited message delivery, enabling asynchronous 919 notifications between the agents. A DOTS client that is no longer 920 interested in receiving notifications from the DOTS server can simply 921 "forget" the observation. When the DOTS server then sends the next 922 notification, the DOTS client will not recognize the token in the 923 message and thus will return a Reset message. This causes the DOTS 924 server to remove the associated entry. 926 DOTS Client DOTS Server 927 | | 928 | GET / | 929 | Token: 0x4a | Registration 930 | Observe: 0 | 931 +-------------------------->| 932 | | 933 | 2.05 Content | 934 | Token: 0x4a | Notification of 935 | Observe: 12 | the current state 936 | status: "mitigation | 937 | in progress" | 938 |<--------------------------+ 939 | 2.05 Content | 940 | Token: 0x4a | Notification upon 941 | Observe: 44 | a state change 942 | status: "mitigation | 943 | complete" | 944 |<--------------------------+ 945 | 2.05 Content | 946 | Token: 0x4a | Notification upon 947 | Observe: 60 | a state change 948 | status: "attack stopped" | 949 |<--------------------------+ 950 | | 952 Figure 10: Notifications of attack mitigation status 954 5.3.3.1. Mitigation Status 956 A DOTS client retrieves the information about a DOTS signal at 957 frequent intervals to determine the status of an attack. If the DOTS 958 server has been able to mitigate the attack and the attack has 959 stopped, the DOTS server indicates as such in the status, and the 960 DOTS client recalls the mitigation request. 962 A DOTS client should react to the status of the attack from the DOTS 963 server and not the fact that it has recognized, using its own means, 964 that the attack has been mitigated. This ensures that the DOTS 965 client does not recall a mitigation request in a premature fashion 966 because it is possible that the DOTS client does not sense the DDOS 967 attack on its resources but the DOTS server could be actively 968 mitigating the attack and the attack is not completely averted. 970 5.3.4. Efficacy Update from DOTS Client 972 While DDoS mitigation is active, a DOTS client MAY frequently 973 transmit DOTS mitigation efficacy updates to the relevant DOTS 974 server. An PUT request (Figure 11) is used to convey the mitigation 975 efficacy update to the DOTS server. The PUT request MUST include all 976 the parameters used in the PUT request to convey the DOTS signal 977 (Section 5.3.1). 979 Header: PUT (Code=0.03) 980 Uri-Host: "host" 981 Uri-Path: "version" 982 Uri-Path: "dots-signal" 983 Uri-Path: "signal" 984 Content-Format: "application/cbor" 985 { 986 "mitigation-scope": { 987 "scope": [ 988 { 989 "policy-id": integer, 990 "target-ip": [ 991 "string" 992 ], 993 "target-port-range": [ 994 { 995 "lower-port": integer, 996 "upper-port": integer 997 } 998 ], 999 "target-protocol": [ 1000 integer 1001 ], 1002 "FQDN": [ 1003 "string" 1004 ], 1005 "URI": [ 1006 "string" 1007 ], 1008 "alias": [ 1009 "string" 1010 ], 1011 "lifetime": integer, 1012 "attack-status": integer 1013 } 1014 ] 1015 } 1016 } 1018 Figure 11: Efficacy Update 1020 The 'attack-status' parameter is a mandatory attribute. The various 1021 possible values contained in the 'attack-status' parameter are 1022 explained below: 1024 /--------------------+------------------------------------------------------\ 1025 | Parameter value | Description | 1026 |--------------------+------------------------------------------------------| 1027 | 1 | DOTS client determines that it is still under attack.| 1028 +---------------------------------------------------------------------------+ 1029 | 2 | DOTS client determines that the attack is | 1030 | | successfully mitigated | 1031 | | (e.g., attack traffic is not seen). | 1032 \--------------------+------------------------------------------------------/ 1034 The DOTS server indicates the result of processing the PUT request 1035 using CoAP response codes. The response code 2.04 (Changed) will be 1036 returned in the response if the DOTS server has accepted the 1037 mitigation efficacy update. If the DOTS server does not find the 1038 policy-id parameter value conveyed in the PUT request in its 1039 configuration data then the server MAY accept the mitigation request 1040 and will try to mitigate the attack, resulting in a 2.01 (Created) 1041 Response Code. The 5.xx response codes are returned if the DOTS 1042 server has erred or is incapable of performing the mitigation. 1044 5.4. DOTS Signal Channel Session Configuration 1046 The DOTS client can negotiate, configure and retrieve the DOTS signal 1047 channel session behavior. The DOTS signal channel can be used, for 1048 example, to configure the following: 1050 a. Heartbeat timeout: DOTS agents regularly send heartbeats (Ping/ 1051 Pong) to each other after mutual authentication in order to keep 1052 the DOTS signal channel open, heartbeat timeout is the time to 1053 wait for a Pong in milliseconds. 1054 b. Acceptable signal loss ratio: Maximum retransmissions, 1055 retransmission timeout value and other message transmission 1056 parameters for the DOTS signal channel. 1058 Reliability is provided to requests and responses by marking them as 1059 Confirmable (CON) messages. DOTS signal channel session 1060 configuration requests and responses are marked as Confirmable (CON) 1061 messages. As explained in Section 2.1 of [RFC7252], a Confirmable 1062 message is retransmitted using a default timeout and exponential 1063 back-off between retransmissions, until the DOTS server sends an 1064 Acknowledgement message (ACK) with the same Message ID conveyed from 1065 the DOTS client. Message transmission parameters are defined in 1066 Section 4.8 of [RFC7252]. Reliability is provided to the responses 1067 by marking them as Confirmable (CON) messages. The DOTS server can 1068 either piggyback the response in the acknowledgement message or if 1069 the DOTS server is not able to respond immediately to a request 1070 carried in a Confirmable message, it simply responds with an Empty 1071 Acknowledgement message so that the DOTS client can stop 1072 retransmitting the request. Empty Acknowledgement message is 1073 explained in Section 2.2 of [RFC7252]. When the response is ready, 1074 the server sends it in a new Confirmable message which then in turn 1075 needs to be acknowledged by the DOTS client (see Sections 5.2.1 and 1076 Sections 5.2.2 in [RFC7252]). Requests and responses exchanged 1077 between DOTS agents during peacetime are marked as Confirmable 1078 messages. 1080 Implementation Note: A DOTS client that receives a response in a CON 1081 message may want to clean up the message state right after sending 1082 the ACK. If that ACK is lost and the DOTS server retransmits the 1083 CON, the DOTS client may no longer have any state to which to 1084 correlate this response, making the retransmission an unexpected 1085 message; the DOTS client will send a Reset message so it does not 1086 receive any more retransmissions. This behavior is normal and not an 1087 indication of an error (see Section 5.3.2 in [RFC7252] for more 1088 details). 1090 5.4.1. Discover Acceptable Configuration Parameters 1092 A GET request is used to obtain acceptable configuration parameters 1093 on the DOTS server for DOTS signal channel session configuration. 1094 Figure 12 shows how to obtain acceptable configuration parameters for 1095 the server. 1097 Header: GET (Code=0.01) 1098 Uri-Host: "host" 1099 Uri-Path: "version" 1100 Uri-Path: "dots-signal" 1101 Uri-Path: "config" 1103 Figure 12: GET to retrieve configuration 1105 The DOTS server in the 2.05 (Content) response conveys the minimum 1106 and maximum attribute values acceptable by the DOTS server. 1108 Content-Format: "application/cbor" 1109 { 1110 "heartbeat-timeout": {"MinValue": integer, "MaxValue" : integer}, 1111 "max-retransmit": {"MinValue": integer, "MaxValue" : integer}, 1112 "ack-timeout": {"MinValue": integer, "MaxValue" : integer}, 1113 "ack-random-factor": {"MinValue": number, "MaxValue" : number} 1114 } 1116 Figure 13: GET response body 1118 5.4.2. Convey DOTS Signal Channel Session Configuration 1120 A POST request is used to convey the configuration parameters for the 1121 signaling channel (e.g., heartbeat timeout, maximum retransmissions 1122 etc). Message transmission parameters for CoAP are defined in 1123 Section 4.8 of [RFC7252]. If the DOTS agent wishes to change the 1124 default values of message transmission parameters then it should 1125 follow the guidance given in Section 4.8.1 of [RFC7252]. The DOTS 1126 agents MUST use the negotiated values for message transmission 1127 parameters and default values for non-negotiated message transmission 1128 parameters. The signaling channel session configuration is 1129 applicable to a single DOTS signal channel session between the DOTS 1130 agents. 1132 Header: POST (Code=0.02) 1133 Uri-Host: "host" 1134 Uri-Path: "version" 1135 Uri-Path: "dots-signal" 1136 Uri-Path: "config" 1137 Content-Format: "application/cbor" 1138 { 1139 "signal-config": { 1140 "policy-id": integer, 1141 "heartbeat-timeout": integer, 1142 "max-retransmit": integer, 1143 "ack-timeout": integer, 1144 "ack-random-factor": number 1145 } 1146 } 1148 Figure 14: POST to convey the DOTS signal channel session 1149 configuration data. 1151 The parameters are described below: 1153 policy-id: Identifier for the DOTS signal channel session 1154 configuration data represented as an integer. This identifier 1155 MUST be generated by the DOTS client. This document does not make 1156 any assumption about how this identifier is generated. This is a 1157 mandatory attribute. 1158 heartbeat-timeout: Heartbeat timeout is the time to wait for a 1159 response in milliseconds to check the DOTS peer health. This is 1160 an optional attribute. 1161 max-retransmit: Maximum number of retransmissions for a message 1162 (referred to as MAX_RETRANSMIT parameter in CoAP). This is an 1163 optional attribute. 1165 ack-timeout: Timeout value in seconds used to calculate the intial 1166 retransmission timeout value (referred to as ACK_TIMEOUT parameter 1167 in CoAP). This is an optional attribute. 1168 ack-random-factor: Random factor used to influence the timing of 1169 retransmissions (referred to as ACK_RANDOM_FACTOR parameter in 1170 CoAP). This is an optional attribute. 1172 In the POST request at least one of the attributes heartbeat-timeout 1173 or max-retransmit or ack-timeout or ack-random-factor MUST be 1174 present. The POST request with higher numeric policy-id value over- 1175 rides the DOTS signal channel session configuration data installed by 1176 a POST request with a lower numeric policy-id value. 1178 Figure 15 shows a POST request example to convey the configuration 1179 parameters for the DOTS signal channel. 1181 Header: POST (Code=0.02) 1182 Uri-Host: "www.example.com" 1183 Uri-Path: "v1" 1184 Uri-Path: "dots-signal" 1185 Uri-Path: "config" 1186 Content-Format: "application/cbor" 1187 { 1188 "signal-config": { 1189 "policy-id": 1234534333242, 1190 "heartbeat-timeout": 30, 1191 "max-retransmit": 7, 1192 "ack-timeout": 5, 1193 "ack-random-factor": 1.5 1194 } 1195 } 1197 Figure 15: POST to convey the configuration parameters 1199 The DOTS server indicates the result of processing the POST request 1200 using CoAP response codes. The CoAP response will include the CBOR 1201 body received in the request. Response code 2.01 (Created) will be 1202 returned in the response if the DOTS server has accepted the 1203 configuration parameters. If the request is missing one or more 1204 mandatory attributes then 4.00 (Bad Request) will be returned in the 1205 response or if the request contains invalid or unknown parameters 1206 then 4.02 (Invalid query) will be returned in the response. Response 1207 code 4.22 (Unprocessable Entity) will be returned in the response if 1208 any of the heartbeat-timeout, max-retransmit, target-protocol, ack- 1209 timeout and ack-random-factor attribute values is not acceptable to 1210 the DOTS server. The DOTS server in the error response conveys the 1211 minimum and maximum attribute values acceptable by the DOTS server. 1213 The DOTS client can re-try and send the POST request with updated 1214 attribute values acceptable to the DOTS server. 1216 Content-Format: "application/cbor" 1217 { 1218 "heartbeat-timeout": {"MinValue": 15, "MaxValue" : 60}, 1219 "max-retransmit": {"MinValue": 3, "MaxValue" : 15}, 1220 "ack-timeout": {"MinValue": 1, "MaxValue" : 30}, 1221 "ack-random-factor": {"MinValue": 1.0, "MaxValue" : 4.0} 1222 } 1224 Figure 16: Error response body 1226 5.4.3. Delete DOTS Signal Channel Session Configuration 1228 A DELETE request is used to delete the installed DOTS signal channel 1229 session configuration data (Figure 17). 1231 Header: DELETE (Code=0.04) 1232 Uri-Host: "host" 1233 Uri-Path: "version" 1234 Uri-Path: "dots-signal" 1235 Uri-Path: "config" 1236 Content-Format: "application/cbor" 1237 { 1238 "signal-config": { 1239 "policy-id": integer 1240 } 1241 } 1243 Figure 17: DELETE configuration 1245 If the DOTS server does not find the policy-id parameter value 1246 conveyed in the DELETE request in its configuration data, then it 1247 responds with a 4.04 (Not Found) error response code. The DOTS 1248 server successfully acknowledges a DOTS client's request to remove 1249 the DOTS signal channel session configuration using 2.02 (Deleted) 1250 response code. 1252 5.4.4. Retrieving DOTS Signal Channel Session Configuration 1254 A GET request is used to retrieve the installed DOTS signal channel 1255 session configuration data from a DOTS server. Figure 18 shows how 1256 to retrieve the DOTS signal channel session configuration data. 1258 Header: GET (Code=0.01) 1259 Uri-Host: "host" 1260 Uri-Path: "version" 1261 Uri-Path: "dots-signal" 1262 Uri-Path: "config" 1263 Content-Format: "application/cbor" 1264 { 1265 "signal-config": { 1266 "policy-id": integer 1267 } 1268 } 1270 Figure 18: GET to retrieve configuration 1272 5.5. Redirected Signaling 1274 Redirected Signaling is discussed in detail in Section 3.2.2 of 1275 [I-D.ietf-dots-architecture]. If the DOTS server wants to redirect 1276 the DOTS client to an alternative DOTS server for a signaling session 1277 then the response code 3.00 (alternate server) will be returned in 1278 the response to the client. The DOTS server can return the error 1279 response code 3.00 in response to a POST or PUT request from the DOTS 1280 client or convey the error response code 3.00 in a unidirectional 1281 notification response from the DOTS server. 1283 The DOTS server in the error response conveys the alternate DOTS 1284 server FQDN, and the alternate DOTS server IP addresses and TTL (time 1285 to live) values in the CBOR body. 1287 { 1288 "alt-server": "string", 1289 "alt-server-record": [ 1290 { 1291 "addr": "string", 1292 "TTL" : integer, 1293 } 1294 ] 1295 } 1297 Figure 19: Error response body 1299 The parameters are described below: 1301 alt-server: FQDN of alternate DOTS server. 1302 addr: IP address of alternate DOTS server. 1303 TTL: Time to live represented as an integer number of seconds. 1305 Figure 20 shows a 3.00 response example to convey the DOTS alternate 1306 server www.example-alt.com, its IP addresses 2002:db8:6401::1 and 1307 2002:db8:6401::2, and TTL values 3600 and 1800. 1309 { 1311 "alt-server": "www.example-alt.com", 1312 "alt-server-record": [ 1313 { 1314 "TTL" : 3600, 1315 "addr": "2002:db8:6401::1" 1316 }, 1317 { 1318 "TTL" : 1800, 1319 "addr": "2002:db8:6401::2" 1320 } 1321 ] 1322 } 1324 Figure 20: Example of error response body 1326 When the DOTS client receives 3.00 response, it considers the current 1327 request as having failed, but SHOULD try the request with the 1328 alternate DOTS server. During a DDOS attack, the DNS server may be 1329 subjected to DDOS attack, alternate DOTS server IP addresses conveyed 1330 in the 3.00 response help the DOTS client to skip DNS lookup of the 1331 alternate DOTS server and can try to establish UDP or TCP session 1332 with the alternate DOTS server IP addresses. The DOTS client SHOULD 1333 implement DNS64 function to handle the scenario where IPv6-only DOTS 1334 client communicates with IPv4-only alternate DOTS server. 1336 5.6. Heartbeat Mechanism 1338 While the communication between the DOTS agents is quiescent, the 1339 DOTS client will probe the DOTS server to ensure it has maintained 1340 cryptographic state and vice versa. Such probes can also keep alive 1341 firewall or NAT bindings. This probing reduces the frequency of 1342 needing a new handshake when a DOTS signal needs to be conveyed to 1343 the DOTS server. In DOTS over UDP, heartbeat messages can be 1344 exchanged between the DOTS agents using the "COAP ping" mechanism 1345 (Section 4.2 in [RFC7252]). The DOTS agent sends an Empty 1346 Confirmable message and the peer DOTS agent will respond by sending 1347 an Reset message. In DOTS over TCP, heartbeat messages can be 1348 exchanged between the DOTS agents using the Ping and Pong messages 1349 (Section 4.4 in [I-D.ietf-core-coap-tcp-tls]). The DOTS agent sends 1350 an Ping message and the peer DOTS agent will respond by sending an 1351 single Pong message. 1353 6. Mapping parameters to CBOR 1355 All parameters in DOTS signal channel are mapped to CBOR types as 1356 follows and are given an integer key value to save space. 1358 /--------------------+------------------------+--------------------------\ 1359 | Parameter name | CBOR key | CBOR major type of value | 1360 |--------------------+------------------------+--------------------------| 1361 | mitigation-scope | 1 | 5 (map) | 1362 | scope | 2 | 5 (map) | 1363 | policy-id | 3 | 0 (unsigned) | 1364 | target-ip | 4 | 4 (array) | 1365 | target-port-range | 5 | 4 | 1366 | lower-port | 6 | 0 | 1367 | upper-port | 7 | 0 | 1368 | target-protocol | 8 | 4 | 1369 | FQDN | 9 | 4 | 1370 | URI | 10 | 4 | 1371 | alias | 11 | 4 | 1372 | lifetime | 12 | 0 | 1373 | attack-status | 13 | 0 | 1374 | signal-config | 14 | 5 | 1375 | heartbeat-timeout | 15 | 0 | 1376 | max-retransmit | 16 | 0 | 1377 | ack-timeout | 17 | 0 | 1378 | ack-random-factor | 18 | 7 | 1379 | MinValue | 19 | 0 | 1380 | MaxValue | 20 | 0 | 1381 | status | 21 | 0 | 1382 | bytes_dropped | 22 | 0 | 1383 | bps_dropped | 23 | 0 | 1384 | pkts_dropped | 24 | 0 | 1385 | pps_dropped | 25 | 0 | 1386 \--------------------+------------------------+--------------------------/ 1388 Figure 21: CBOR mappings used in DOTS signal channel message 1390 7. (D)TLS Protocol Profile and Performance considerations 1392 This section defines the (D)TLS protocol profile of DOTS signal 1393 channel over (D)TLS and DOTS data channel over TLS. 1395 There are known attacks on (D)TLS, such as machine-in-the-middle and 1396 protocol downgrade. These are general attacks on (D)TLS and not 1397 specific to DOTS over (D)TLS; please refer to the (D)TLS RFCs for 1398 discussion of these security issues. DOTS agents MUST adhere to the 1399 (D)TLS implementation recommendations and security considerations of 1400 [RFC7525] except with respect to (D)TLS version. Since encryption of 1401 DOTS using (D)TLS is virtually a green-field deployment DOTS agents 1402 MUST implement only (D)TLS 1.2 or later. 1404 Implementations compliant with this profile MUST implement all of the 1405 following items: 1407 o DOTS agents MUST support DTLS record replay detection (Section 3.3 1408 in [RFC6347]) to protect against replay attacks. 1409 o DOTS client can use (D)TLS session resumption without server-side 1410 state [RFC5077] to resume session and convey the DOTS signal. 1411 o Raw public keys [RFC7250] which reduce the size of the 1412 ServerHello, and can be used by servers that cannot obtain 1413 certificates (e.g., DOTS gateways on private networks). 1415 Implementations compliant with this profile SHOULD implement all of 1416 the following items to reduce the delay required to deliver a DOTS 1417 signal: 1419 o TLS False Start [RFC7918] which reduces round-trips by allowing 1420 the TLS second flight of messages (ChangeCipherSpec) to also 1421 contain the DOTS signal. 1422 o Cached Information Extension [RFC7924] which avoids transmitting 1423 the server's certificate and certificate chain if the client has 1424 cached that information from a previous TLS handshake. 1425 o TCP Fast Open [RFC7413] can reduce the number of round-trips to 1426 convey DOTS signal. 1428 7.1. MTU and Fragmentation Issues 1430 To avoid DOTS signal message fragmentation and the consequently 1431 decreased probability of message delivery, DOTS agents MUST ensure 1432 that the DTLS record MUST fit within a single datagram. If the Path 1433 MTU is not known to the DOTS server, an IP MTU of 1280 bytes SHOULD 1434 be assumed. The length of the URL MUST NOT exceed 256 bytes. If UDP 1435 is used to convey the DOTS signal messages then the DOTS client must 1436 consider the amount of record expansion expected by the DTLS 1437 processing when calculating the size of CoAP message that fits within 1438 the path MTU. Path MTU MUST be greater than or equal to [CoAP 1439 message size + DTLS overhead of 13 octets + authentication overhead 1440 of the negotiated DTLS cipher suite + block padding (Section 4.1.1.1 1441 of [RFC6347]]. If the request size exceeds the Path MTU then the 1442 DOTS client MUST split the DOTS signal into separate messages, for 1443 example the list of addresses in the 'target-ip' parameter could be 1444 split into multiple lists and each list conveyed in a new POST 1445 request. 1447 Implementation Note: DOTS choice of message size parameters works 1448 well with IPv6 and with most of today's IPv4 paths. However, with 1449 IPv4, it is harder to absolutely ensure that there is no IP 1450 fragmentation. If IPv4 support on unusual networks is a 1451 consideration and path MTU is unknown, implementations may want to 1452 limit themselves to more conservative IPv4 datagram sizes such as 576 1453 bytes, as per [RFC0791] IP packets up to 576 bytes should never need 1454 to be fragmented, thus sending a maximum of 500 bytes of DOTS signal 1455 over a UDP datagram will generally avoid IP fragmentation. 1457 8. (D)TLS 1.3 considerations 1459 TLS 1.3 [I-D.ietf-tls-tls13] provides critical latency improvements 1460 for connection establishment over TLS 1.2. The DTLS 1.3 protocol 1461 [I-D.rescorla-tls-dtls13] is based on the TLS 1.3 protocol and 1462 provides equivalent security guarantees. (D)TLS 1.3 provides two 1463 basic handshake modes of interest to DOTS signal channel: 1465 o Absent packet loss, a full handshake in which the DOTS client is 1466 able to send the DOTS signal message after one round trip and the 1467 DOTS server immediately after receiving the first DOTS signal 1468 message from the client. 1469 o 0-RTT mode in which the DOTS client can authenticate itself and 1470 send DOTS signal message on its first flight, thus reducing 1471 handshake latency. 0-RTT only works if the DOTS client has 1472 previously communicated with that DOTS server, which is very 1473 likely with the DOTS signal channel. The DOTS client SHOULD 1474 establish a (D)TLS session with the DOTS server during peacetime 1475 and share a PSK. During DDOS attack, the DOTS client can use the 1476 (D)TLS session to convey the DOTS signal message and if there is 1477 no response from the server after multiple re-tries then the DOTS 1478 client can resume the (D)TLS session in 0-RTT mode using PSK. A 1479 simplified TLS 1.3 handshake with 0-RTT DOTS signal message 1480 exchange is shown in Figure 22. 1482 DOTS Client DOTS Server 1484 ClientHello 1485 (Finished) 1486 (0-RTT DOTS signal message) 1487 (end_of_early_data) --------> 1488 ServerHello 1489 {EncryptedExtensions} 1490 {ServerConfiguration} 1491 {Certificate} 1492 {CertificateVerify} 1493 {Finished} 1494 <-------- [DOTS signal message] 1495 {Finished} --------> 1497 [DOTS signal message] <-------> [DOTS signal message] 1499 Figure 22: TLS 1.3 handshake with 0-RTT 1501 9. Mutual Authentication of DOTS Agents & Authorization of DOTS Clients 1503 (D)TLS based on client certificate can be used for mutual 1504 authentication between DOTS agents. If a DOTS gateway is involved, 1505 DOTS clients and DOTS gateway MUST perform mutual authentication; 1506 only authorized DOTS clients are allowed to send DOTS signals to a 1507 DOTS gateway. DOTS gateway and DOTS server MUST perform mutual 1508 authentication; DOTS server only allows DOTS signals from authorized 1509 DOTS gateway, creating a two-link chain of transitive authentication 1510 between the DOTS client and the DOTS server. 1512 +-------------------------------------------------+ 1513 | example.com domain +---------+ | 1514 | | AAA | | 1515 | +---------------+ | Server | | 1516 | | Application | +------+--+ | 1517 | | server + ^ 1518 | | (DOTS client) |<-----------------+ | | 1519 | +---------------+ + | | example.net domain 1520 | V V | 1521 | +-------------+ | +---------------+ 1522 | +--------------+ | | | | | 1523 | | Guest +<-----x----->+ +<---------------->+ DOTS | 1524 | | (DOTS client)| | DOTS | | | Server | 1525 | +--------------+ | Gateway | | | | 1526 | +----+--------+ | +---------------+ 1527 | ^ | 1528 | | | 1529 | +----------------+ | | 1530 | | DDOS detector | | | 1531 | | (DOTS client) +<--------------+ | 1532 | +----------------+ | 1533 | | 1534 +-------------------------------------------------+ 1536 Figure 23: Example of Authentication and Authorization of DOTS Agents 1538 In the example depicted in Figure 23, the DOTS gateway and DOTS 1539 clients within the 'example.com' domain mutually authenticate with 1540 each other. After the DOTS gateway validates the identity of a DOTS 1541 client, it communicates with the AAA server in the 'example.com' 1542 domain to determine if the DOTS client is authorized to request DDOS 1543 mitigation. If the DOTS client is not authorized, a 4.01 1544 (Unauthorized) is returned in the response to the DOTS client. In 1545 this example, the DOTS gateway only allows the application server and 1546 DDOS detector to request DDOS mitigation, but does not permit the 1547 user of type 'guest' to request DDOS mitigation. 1549 Also, DOTS gateway and DOTS server MUST perform mutual authentication 1550 using certificates. A DOTS server will only allow a DOTS gateway 1551 with a certificate for a particular domain to request mitigation for 1552 that domain. In reference to Figure 23, the DOTS server only allows 1553 the DOTS gateway to request mitigation for 'example.com' domain and 1554 not for other domains. 1556 10. IANA Considerations 1558 This specification registers new parameters for DOTS signal channel 1559 and establishes registries for mappings to CBOR. 1561 10.1. DOTS signal channel CBOR Mappings Registry 1563 A new registry will be requested from IANA, entitled "DOTS signal 1564 channel CBOR Mappings Registry". The registry is to be created as 1565 Expert Review Required. 1567 10.1.1. Registration Template 1569 Parameter name: 1570 Parameter names (e.g., "target_ip") in the DOTS signal channel. 1571 CBOR Key Value: 1572 Key value for the parameter. The key value MUST be an integer in 1573 the range of 1 to 65536. The key values in the range of 32768 to 1574 65536 are assigned for Vendor-Specific parameters. 1575 CBOR Major Type: 1576 CBOR Major type and optional tag for the claim. 1577 Change Controller: 1578 For Standards Track RFCs, list the "IESG". For others, give the 1579 name of the responsible party. Other details (e.g., postal 1580 address, email address, home page URI) may also be included. 1581 Specification Document(s): 1582 Reference to the document or documents that specify the parameter, 1583 preferably including URIs that can be used to retrieve copies of 1584 the documents. An indication of the relevant sections may also be 1585 included but is not required. 1587 10.1.2. Initial Registry Contents 1589 o Parameter Name: "mitigation-scope" 1590 o CBOR Key Value: 1 1591 o CBOR Major Type: 5 1592 o Change Controller: IESG 1593 o Specification Document(s): this document 1595 o Parameter Name: "scope" 1596 o CBOR Key Value: 2 1597 o CBOR Major Type: 5 1598 o Change Controller: IESG 1599 o Specification Document(s): this document 1601 o Parameter Name: "policy-id" 1602 o CBOR Key Value: 3 1603 o CBOR Major Type: 0 1604 o Change Controller: IESG 1605 o Specification Document(s): this document 1607 o Parameter Name:target-ip 1608 o CBOR Key Value: 4 1609 o CBOR Major Type: 4 1610 o Change Controller: IESG 1611 o Specification Document(s): this document 1613 o Parameter Name: target-port-range 1614 o CBOR Key Value: 5 1615 o CBOR Major Type: 4 1616 o Change Controller: IESG 1617 o Specification Document(s): this document 1619 o Parameter Name: "lower-port" 1620 o CBOR Key Value: 6 1621 o CBOR Major Type: 0 1622 o Change Controller: IESG 1623 o Specification Document(s): this document 1625 o Parameter Name: "upper-port" 1626 o CBOR Key Value: 7 1627 o CBOR Major Type: 0 1628 o Change Controller: IESG 1629 o Specification Document(s): this document 1631 o Parameter Name: target-protocol 1632 o CBOR Key Value: 8 1633 o CBOR Major Type: 4 1634 o Change Controller: IESG 1635 o Specification Document(s): this document 1637 o Parameter Name: "FQDN" 1638 o CBOR Key Value: 9 1639 o CBOR Major Type: 4 1640 o Change Controller: IESG 1641 o Specification Document(s): this document 1643 o Parameter Name: "URI" 1644 o CBOR Key Value: 10 1645 o CBOR Major Type: 4 1646 o Change Controller: IESG 1647 o Specification Document(s): this document 1649 o Parameter Name: alias 1650 o CBOR Key Value: 11 1651 o CBOR Major Type: 4 1652 o Change Controller: IESG 1653 o Specification Document(s): this document 1655 o Parameter Name: "lifetime" 1656 o CBOR Key Value: 12 1657 o CBOR Major Type: 0 1658 o Change Controller: IESG 1659 o Specification Document(s): this document 1661 o Parameter Name: attack-status 1662 o CBOR Key Value: 13 1663 o CBOR Major Type: 0 1664 o Change Controller: IESG 1665 o Specification Document(s): this document 1667 o Parameter Name: signal-config 1668 o CBOR Key Value: 14 1669 o CBOR Major Type: 5 1670 o Change Controller: IESG 1671 o Specification Document(s): this document 1673 o Parameter Name: heartbeat-timeout 1674 o CBOR Key Value: 15 1675 o CBOR Major Type: 0 1676 o Change Controller: IESG 1677 o Specification Document(s): this document 1679 o Parameter Name: max-retransmit 1680 o CBOR Key Value: 16 1681 o CBOR Major Type: 0 1682 o Change Controller: IESG 1683 o Specification Document(s): this document 1685 o Parameter Name: ack-timeout 1686 o CBOR Key Value: 17 1687 o CBOR Major Type: 0 1688 o Change Controller: IESG 1689 o Specification Document(s): this document 1691 o Parameter Name: ack-random-factor 1692 o CBOR Key Value: 18 1693 o CBOR Major Type: 7 1694 o Change Controller: IESG 1695 o Specification Document(s): this document 1697 o Parameter Name: MinValue 1698 o CBOR Key Value: 19 1699 o CBOR Major Type: 0 1700 o Change Controller: IESG 1701 o Specification Document(s): this document 1703 o Parameter Name: MaxValue 1704 o CBOR Key Value: 20 1705 o CBOR Major Type: 0 1706 o Change Controller: IESG 1707 o Specification Document(s): this document 1709 o Parameter Name: status 1710 o CBOR Key Value: 21 1711 o CBOR Major Type: 0 1712 o Change Controller: IESG 1713 o Specification Document(s): this document 1715 o Parameter Name: bytes_dropped 1716 o CBOR Key Value: 22 1717 o CBOR Major Type: 0 1718 o Change Controller: IESG 1719 o Specification Document(s): this document 1721 o Parameter Name: bps_dropped 1722 o CBOR Key Value: 23 1723 o CBOR Major Type: 0 1724 o Change Controller: IESG 1725 o Specification Document(s): this document 1727 o Parameter Name: pkts_dropped 1728 o CBOR Key Value: 24 1729 o CBOR Major Type: 0 1730 o Change Controller: IESG 1731 o Specification Document(s): this document 1733 o Parameter Name: pps_dropped 1734 o CBOR Key Value: 25 1735 o CBOR Major Type: 0 1736 o Change Controller: IESG 1737 o Specification Document(s): this document 1739 11. Implementation Status 1741 [Note to RFC Editor: Please remove this section and reference to 1742 [RFC6982] prior to publication.] 1744 This section records the status of known implementations of the 1745 protocol defined by this specification at the time of posting of this 1746 Internet-Draft, and is based on a proposal described in [RFC6982]. 1747 The description of implementations in this section is intended to 1748 assist the IETF in its decision processes in progressing drafts to 1749 RFCs. Please note that the listing of any individual implementation 1750 here does not imply endorsement by the IETF. Furthermore, no effort 1751 has been spent to verify the information presented here that was 1752 supplied by IETF contributors. This is not intended as, and must not 1753 be construed to be, a catalog of available implementations or their 1754 features. Readers are advised to note that other implementations may 1755 exist. 1757 According to [RFC6982], "this will allow reviewers and working groups 1758 to assign due consideration to documents that have the benefit of 1759 running code, which may serve as evidence of valuable experimentation 1760 and feedback that have made the implemented protocols more mature. 1761 It is up to the individual working groups to use this information as 1762 they see fit". 1764 11.1. nttdots 1766 Organization: NTT Communication is developing a DOTS client and 1767 DOTS server software based on DOTS signal channel specified in 1768 this draft. It will be open-sourced. 1769 Description: Early implementation of DOTS protocol. It is aimed to 1770 implement a full DOTS protocol spec in accordance with maturing of 1771 DOTS protocol itself. 1772 Implementation: To be open-sourced. 1773 Level of maturity: It is a early implementation of DOTS protocol. 1774 Messaging between DOTS clients and DOTS servers has been tested. 1775 Level of maturity will increase in accordance with maturing of 1776 DOTS protocol itself. 1777 Coverage: Capability of DOTS client: sending DOTS messages to the 1778 DOTS server in CoAP over DTLS as dots-signal. Capability of DOTS 1779 server: receiving dots-signal, validating received dots-signal, 1780 starting mitigation by handing over the dots-signal to DDOS 1781 mitigator. 1782 Licensing: It will be open-sourced with BSD 3-clause license. 1783 Implementation experience: It is implemented in Go-lang. Core 1784 specification of signaling is mature to be implemented, however, 1785 finding good libraries(like DTLS, CoAP) is rather difficult. 1786 Contact: Kaname Nishizuka 1788 12. Security Considerations 1790 Authenticated encryption MUST be used for data confidentiality and 1791 message integrity. (D)TLS based on client certificate MUST be used 1792 for mutual authentication. The interaction between the DOTS agents 1793 requires Datagram Transport Layer Security (DTLS) and Transport Layer 1794 Security (TLS) with a cipher suite offering confidentiality 1795 protection and the guidance given in [RFC7525] MUST be followed to 1796 avoid attacks on (D)TLS. 1798 A single DOTS signal channel between DOTS agents can be used to 1799 exchange multiple DOTS signal messages. To reduce DOTS client and 1800 DOTS server workload, DOTS client SHOULD re-use the (D)TLS session. 1802 If TCP is used between DOTS agents, an attacker may be able to inject 1803 RST packets, bogus application segments, etc., regardless of whether 1804 TLS authentication is used. Because the application data is TLS 1805 protected, this will not result in the application receiving bogus 1806 data, but it will constitute a DoS on the connection. This attack 1807 can be countered by using TCP-AO [RFC5925]. If TCP-AO is used, then 1808 any bogus packets injected by an attacker will be rejected by the 1809 TCP-AO integrity check and therefore will never reach the TLS layer. 1811 Special care should be taken in order to ensure that the activation 1812 of the proposed mechanism won't have an impact on the stability of 1813 the network (including connectivity and services delivered over that 1814 network). 1816 Involved functional elements in the cooperation system must establish 1817 exchange instructions and notification over a secure and 1818 authenticated channel. Adequate filters can be enforced to avoid 1819 that nodes outside a trusted domain can inject request such as 1820 deleting filtering rules. Nevertheless, attacks can be initiated 1821 from within the trusted domain if an entity has been corrupted. 1822 Adequate means to monitor trusted nodes should also be enabled. 1824 13. Contributors 1826 The following individuals have contributed to this document: 1828 Mike Geller Cisco Systems, Inc. 3250 Florida 33309 USA Email: 1829 mgeller@cisco.com 1831 Robert Moskowitz HTT Consulting Oak Park, MI 42837 United States 1832 Email: rgm@htt-consult.com 1834 Dan Wing Email: dwing-ietf@fuggles.com 1836 14. Acknowledgements 1838 Thanks to Christian Jacquenet, Roland Dobbins, Andrew Mortensen, 1839 Roman D. Danyliw, Michael Richardson, Ehud Doron, Kaname Nishizuka, 1840 Dave Dolson and Gilbert Clark for the discussion and comments. 1842 15. References 1844 15.1. Normative References 1846 [I-D.ietf-core-coap-tcp-tls] 1847 Bormann, C., Lemay, S., Tschofenig, H., Hartke, K., 1848 Silverajan, B., and B. Raymor, "CoAP (Constrained 1849 Application Protocol) over TCP, TLS, and WebSockets", 1850 draft-ietf-core-coap-tcp-tls-07 (work in progress), March 1851 2017. 1853 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1854 Requirement Levels", BCP 14, RFC 2119, 1855 DOI 10.17487/RFC2119, March 1997, 1856 . 1858 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 1859 (TLS) Protocol Version 1.2", RFC 5246, 1860 DOI 10.17487/RFC5246, August 2008, 1861 . 1863 [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP 1864 Authentication Option", RFC 5925, DOI 10.17487/RFC5925, 1865 June 2010, . 1867 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 1868 Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, 1869 January 2012, . 1871 [RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J., 1872 Weiler, S., and T. Kivinen, "Using Raw Public Keys in 1873 Transport Layer Security (TLS) and Datagram Transport 1874 Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250, 1875 June 2014, . 1877 [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained 1878 Application Protocol (CoAP)", RFC 7252, 1879 DOI 10.17487/RFC7252, June 2014, 1880 . 1882 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 1883 "Recommendations for Secure Use of Transport Layer 1884 Security (TLS) and Datagram Transport Layer Security 1885 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 1886 2015, . 1888 [RFC7641] Hartke, K., "Observing Resources in the Constrained 1889 Application Protocol (CoAP)", RFC 7641, 1890 DOI 10.17487/RFC7641, September 2015, 1891 . 1893 15.2. Informative References 1895 [I-D.ietf-core-comi] 1896 Stok, P., Bierman, A., Veillette, M., and A. Pelov, "CoAP 1897 Management Interface", draft-ietf-core-comi-00 (work in 1898 progress), January 2017. 1900 [I-D.ietf-core-yang-cbor] 1901 Veillette, M., Pelov, A., Somaraju, A., Turner, R., and A. 1902 Minaburo, "CBOR Encoding of Data Modeled with YANG", 1903 draft-ietf-core-yang-cbor-04 (work in progress), February 1904 2017. 1906 [I-D.ietf-dots-architecture] 1907 Mortensen, A., Andreasen, F., Reddy, T., 1908 christopher_gray3@cable.comcast.com, c., Compton, R., and 1909 N. Teague, "Distributed-Denial-of-Service Open Threat 1910 Signaling (DOTS) Architecture", draft-ietf-dots- 1911 architecture-01 (work in progress), October 2016. 1913 [I-D.ietf-dots-requirements] 1914 Mortensen, A., Moskowitz, R., and T. Reddy, "Distributed 1915 Denial of Service (DDoS) Open Threat Signaling 1916 Requirements", draft-ietf-dots-requirements-04 (work in 1917 progress), March 2017. 1919 [I-D.ietf-dots-use-cases] 1920 Dobbins, R., Fouant, S., Migault, D., Moskowitz, R., 1921 Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS 1922 Open Threat Signaling", draft-ietf-dots-use-cases-04 (work 1923 in progress), March 2017. 1925 [I-D.ietf-tls-tls13] 1926 Rescorla, E., "The Transport Layer Security (TLS) Protocol 1927 Version 1.3", draft-ietf-tls-tls13-19 (work in progress), 1928 March 2017. 1930 [I-D.ietf-tsvwg-rfc5405bis] 1931 Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage 1932 Guidelines", draft-ietf-tsvwg-rfc5405bis-19 (work in 1933 progress), October 2016. 1935 [I-D.reddy-dots-data-channel] 1936 Reddy, T., Boucadair, M., Nishizuka, K., Xia, L., Patil, 1937 P., Mortensen, A., and N. Teague, "Distributed Denial-of- 1938 Service Open Threat Signaling (DOTS) Data Channel", draft- 1939 reddy-dots-data-channel-05 (work in progress), March 2017. 1941 [I-D.rescorla-tls-dtls13] 1942 Rescorla, E., Tschofenig, H., and N. Modadugu, "The 1943 Datagram Transport Layer Security (DTLS) Protocol Version 1944 1.3", draft-rescorla-tls-dtls13-01 (work in progress), 1945 March 2017. 1947 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 1948 DOI 10.17487/RFC0791, September 1981, 1949 . 1951 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 1952 (CIDR): The Internet Address Assignment and Aggregation 1953 Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August 1954 2006, . 1956 [RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet 1957 Denial-of-Service Considerations", RFC 4732, 1958 DOI 10.17487/RFC4732, December 2006, 1959 . 1961 [RFC4987] Eddy, W., "TCP SYN Flooding Attacks and Common 1962 Mitigations", RFC 4987, DOI 10.17487/RFC4987, August 2007, 1963 . 1965 [RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig, 1966 "Transport Layer Security (TLS) Session Resumption without 1967 Server-Side State", RFC 5077, DOI 10.17487/RFC5077, 1968 January 2008, . 1970 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 1971 the Network Configuration Protocol (NETCONF)", RFC 6020, 1972 DOI 10.17487/RFC6020, October 2010, 1973 . 1975 [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with 1976 Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555, April 1977 2012, . 1979 [RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown, 1980 "Default Address Selection for Internet Protocol Version 6 1981 (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012, 1982 . 1984 [RFC6982] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 1985 Code: The Implementation Status Section", RFC 6982, 1986 DOI 10.17487/RFC6982, July 2013, 1987 . 1989 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 1990 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 1991 October 2013, . 1993 [RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP 1994 Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014, 1995 . 1997 [RFC7918] Langley, A., Modadugu, N., and B. Moeller, "Transport 1998 Layer Security (TLS) False Start", RFC 7918, 1999 DOI 10.17487/RFC7918, August 2016, 2000 . 2002 [RFC7924] Santesson, S. and H. Tschofenig, "Transport Layer Security 2003 (TLS) Cached Information Extension", RFC 7924, 2004 DOI 10.17487/RFC7924, July 2016, 2005 . 2007 Authors' Addresses 2009 Tirumaleswar Reddy 2010 Cisco Systems, Inc. 2011 Cessna Business Park, Varthur Hobli 2012 Sarjapur Marathalli Outer Ring Road 2013 Bangalore, Karnataka 560103 2014 India 2016 Email: tireddy@cisco.com 2018 Mohamed Boucadair 2019 Orange 2020 Rennes 35000 2021 France 2023 Email: mohamed.boucadair@orange.com 2025 Prashanth Patil 2026 Cisco Systems, Inc. 2028 Email: praspati@cisco.com 2029 Andrew Mortensen 2030 Arbor Networks, Inc. 2031 2727 S. State St 2032 Ann Arbor, MI 48104 2033 United States 2035 Email: amortensen@arbor.net 2037 Nik Teague 2038 Verisign, Inc. 2039 United States 2041 Email: nteague@verisign.com