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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 McAfee 4 Intended status: Standards Track M. Boucadair 5 Expires: April 30, 2018 Orange 6 P. Patil 7 Cisco 8 A. Mortensen 9 Arbor Networks, Inc. 10 N. Teague 11 Verisign, Inc. 12 October 27, 2017 14 Distributed Denial-of-Service Open Threat Signaling (DOTS) Signal 15 Channel 16 draft-ietf-dots-signal-channel-06 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 https://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 April 30, 2018. 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 (https://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 . . . . . . . . . . . . . . . . . . . . . 6 66 5.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 7 67 5.2. DOTS Signal YANG Module . . . . . . . . . . . . . . . . . 8 68 5.2.1. Mitigation Request YANG Module Tree Structure . . . . 8 69 5.2.2. Mitigation Request YANG Module . . . . . . . . . . . 8 70 5.2.3. Session Configuration YANG Module Tree Structure . . 11 71 5.2.4. Session Configuration YANG Module . . . . . . . . . . 12 72 5.3. Mitigation Request . . . . . . . . . . . . . . . . . . . 14 73 5.3.1. Requesting mitigation . . . . . . . . . . . . . . . . 15 74 5.3.2. Withdraw a DOTS Signal . . . . . . . . . . . . . . . 23 75 5.3.3. Retrieving a DOTS Signal . . . . . . . . . . . . . . 24 76 5.3.4. Efficacy Update from DOTS Client . . . . . . . . . . 29 77 5.4. DOTS Signal Channel Session Configuration . . . . . . . . 31 78 5.4.1. Discover Configuration Parameters . . . . . . . . . . 32 79 5.4.2. Convey DOTS Signal Channel Session Configuration . . 34 80 5.4.3. Delete DOTS Signal Channel Session Configuration . . 38 81 5.5. Redirected Signaling . . . . . . . . . . . . . . . . . . 38 82 5.6. Heartbeat Mechanism . . . . . . . . . . . . . . . . . . . 40 83 6. Mapping parameters to CBOR . . . . . . . . . . . . . . . . . 40 84 7. (D)TLS Protocol Profile and Performance considerations . . . 41 85 7.1. MTU and Fragmentation Issues . . . . . . . . . . . . . . 42 86 8. (D)TLS 1.3 considerations . . . . . . . . . . . . . . . . . . 43 87 9. Mutual Authentication of DOTS Agents & Authorization of DOTS 88 Clients . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 89 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46 90 10.1. CoAP Response Code . . . . . . . . . . . . . . . . . . . 46 91 10.2. DOTS signal channel CBOR Mappings Registry . . . . . . . 46 92 10.2.1. Registration Template . . . . . . . . . . . . . . . 46 93 10.2.2. Initial Registry Contents . . . . . . . . . . . . . 47 94 11. Implementation Status . . . . . . . . . . . . . . . . . . . . 51 95 11.1. nttdots . . . . . . . . . . . . . . . . . . . . . . . . 51 96 12. Security Considerations . . . . . . . . . . . . . . . . . . . 52 97 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 53 98 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 53 99 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 53 100 15.1. Normative References . . . . . . . . . . . . . . . . . . 53 101 15.2. Informative References . . . . . . . . . . . . . . . . . 54 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 57 104 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 network administrators to 114 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 document adheres to the DOTS architecture 123 [I-D.ietf-dots-architecture]. The requirements for DOTS signal 124 channel protocol are obtained from [I-D.ietf-dots-requirements]. 125 This document satisfies all the use cases discussed in 126 [I-D.ietf-dots-use-cases]. 128 This is a companion document to the DOTS data channel specification 129 [I-D.ietf-dots-data-channel] that defines a configuration and bulk 130 data exchange mechanism supporting the DOTS signal channel. 132 2. Notational Conventions and Terminology 134 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 135 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 136 "OPTIONAL" in this document are to be interpreted as described in 137 [RFC2119]. 139 (D)TLS: For brevity this term is used for statements that apply to 140 both Transport Layer Security [RFC5246] and Datagram Transport Layer 141 Security [RFC6347]. Specific terms will be used for any statement 142 that applies to either protocol alone. 144 The reader should be familiar with the terms defined in 145 [I-D.ietf-dots-architecture]. 147 3. Solution Overview 149 Network applications have finite resources like CPU cycles, number of 150 processes or threads they can create and use, maximum number of 151 simultaneous connections it can handle, limited resources of the 152 control plane, etc. When processing network traffic, such 153 applications are supposed to use these resources to offer the 154 intended task in the most efficient fashion. However, an attacker 155 may be able to prevent an application from performing its intended 156 task by causing the application to exhaust the finite supply of a 157 specific resource. 159 TCP DDoS SYN-flood, for example, is a memory-exhaustion attack on the 160 victim and ACK-flood is a CPU exhaustion attack on the victim 161 ([RFC4987]). Attacks on the link are carried out by sending enough 162 traffic such that the link becomes excessively congested, and 163 legitimate traffic suffers high packet loss. Stateful firewalls can 164 also be attacked by sending traffic that causes the firewall to hold 165 excessive state. The firewall then runs out of memory, and can no 166 longer instantiate the state required to pass legitimate flows. 167 Other possible DDoS attacks are discussed in [RFC4732]. 169 In each of the cases described above, the possible arrangements 170 between the DOTS client and DOTS server to mitigate the attack are 171 discussed in [I-D.ietf-dots-use-cases]. An example of network 172 diagram showing a deployment of these elements is shown in Figure 1. 173 Architectural relationships between involved DOTS agents is explained 174 in [I-D.ietf-dots-architecture]. In this example, the DOTS server is 175 operating on the access network. 177 Network 178 Resource CPE router Access network __________ 179 +-----------+ +--------------+ +-------------+ / \ 180 | |____| |_______| |___ | Internet | 181 |DOTS client| | DOTS gateway | | DOTS server | | | 182 | | | | | | | | 183 +-----------+ +--------------+ +-------------+ \__________/ 185 Figure 1: Sample DOTS Deployment (1) 187 The DOTS server can also be running on the Internet, as depicted in 188 Figure 2. 190 Network DDoS mitigation 191 Resource CPE router __________ service 192 +-----------+ +-------------+ / \ +-------------+ 193 | |____| |_______| |___ | | 194 |DOTS client| |DOTS gateway | | Internet | | DOTS server | 195 | | | | | | | | 196 +-----------+ +-------------+ \__________/ +-------------+ 198 Figure 2: Sample DOTS Deployment (2) 200 In typical deployments, the DOTS client belongs to a different 201 administrative domain than the DOTS server. For example, the DOTS 202 client is a firewall protecting services owned and operated by an 203 domain, while the DOTS server is owned and operated by a different 204 domain providing DDoS mitigation services. That domain providing 205 DDoS mitigation service might, or might not, also provide Internet 206 access service to the website operator. 208 The DOTS server may (not) be co-located with the DOTS mitigator. In 209 typical deployments, the DOTS server belongs to the same 210 administrative domain as the mitigator. 212 The DOTS client can communicate directly with the DOTS server or 213 indirectly via a DOTS gateway. 215 This document focuses on the DOTS signal channel. 217 4. Happy Eyeballs for DOTS Signal Channel 219 DOTS signaling can happen with DTLS [RFC6347] over UDP and TLS 220 [RFC5246] over TCP. A DOTS client can use DNS to determine the IP 221 address(es) of a DOTS server or a DOTS client may be provided with 222 the list of DOTS server IP addresses. The DOTS client MUST know a 223 DOTS server's domain name; hard-coding the domain name of the DOTS 224 server into software is NOT RECOMMENDED in case the domain name is 225 not valid or needs to change for legal or other reasons. The DOTS 226 client performs A and/or AAAA record lookup of the domain name and 227 the result will be a list of IP addresses, each of which can be used 228 to contact the DOTS server using UDP and TCP. 230 If an IPv4 path to reach a DOTS server is found, but the DOTS 231 server's IPv6 path is not working, a dual-stack DOTS client can 232 experience a significant connection delay compared to an IPv4-only 233 DOTS client. The other problem is that if a middlebox between the 234 DOTS client and DOTS server is configured to block UDP, the DOTS 235 client will fail to establish a DTLS session with the DOTS server and 236 will, then, have to fall back to TLS over TCP incurring significant 237 connection delays. [I-D.ietf-dots-requirements] discusses that DOTS 238 client and server will have to support both connectionless and 239 connection-oriented protocols. 241 To overcome these connection setup problems, the DOTS client can try 242 connecting to the DOTS server using both IPv6 and IPv4, and try both 243 DTLS over UDP and TLS over TCP in a fashion similar to the Happy 244 Eyeballs mechanism [RFC6555]. These connection attempts are 245 performed by the DOTS client when its initializes, and the client 246 uses that information for its subsequent alert to the DOTS server. 247 In order of preference (most preferred first), it is UDP over IPv6, 248 UDP over IPv4, TCP over IPv6, and finally TCP over IPv4, which 249 adheres to address preference order [RFC6724] and the DOTS preference 250 that UDP be used over TCP (to avoid TCP's head of line blocking). 252 DOTS client DOTS server 253 | | 254 |--DTLS ClientHello, IPv6 ---->X | 255 |--TCP SYN, IPv6-------------->X | 256 |--DTLS ClientHello, IPv4 ---->X | 257 |--TCP SYN, IPv4----------------------------------------->| 258 |--DTLS ClientHello, IPv6 ---->X | 259 |--TCP SYN, IPv6-------------->X | 260 |<-TCP SYNACK---------------------------------------------| 261 |--DTLS ClientHello, IPv4 ---->X | 262 |--TCP ACK----------------------------------------------->| 263 |<------------Establish TLS Session---------------------->| 264 |----------------DOTS signal----------------------------->| 265 | | 267 Figure 3: Happy Eyeballs 269 In reference to Figure 3, the DOTS client sends two TCP SYNs and two 270 DTLS ClientHello messages at the same time over IPv6 and IPv4. In 271 this example, it is assumed that the IPv6 path is broken and UDP is 272 dropped by a middlebox but has little impact to the DOTS client 273 because there is no long delay before using IPv4 and TCP. The DOTS 274 client repeats the mechanism to discover if DOTS signaling with DTLS 275 over UDP becomes available from the DOTS server, so the DOTS client 276 can migrate the DOTS signal channel from TCP to UDP, but such probing 277 SHOULD NOT be done more frequently than every 24 hours and MUST NOT 278 be done more frequently than every 5 minutes. 280 5. DOTS Signal Channel 281 5.1. Overview 283 The DOTS signal channel is built on top of the Constrained 284 Application Protocol (CoAP) [RFC7252], a lightweight protocol 285 originally designed for constrained devices and networks. CoAP's 286 expectation of packet loss, support for asynchronous non-confirmable 287 messaging, congestion control, small message overhead limiting the 288 need for fragmentation, use of minimal resources, and support for 289 (D)TLS make it a good foundation on which to build the DOTS signaling 290 mechanism. 292 The DOTS signal channel is layered on existing standards (Figure 4). 294 TBD: The default port number for DOTS signal channel is 5684 295 (Section 12.7 of [RFC7252] and Section 10.4 of 296 [I-D.ietf-core-coap-tcp-tls]), for both UDP and TCP. 298 +--------------+ 299 | DOTS | 300 +--------------+ 301 | CoAP | 302 +--------------+ 303 | TLS | DTLS | 304 +--------------+ 305 | TCP | UDP | 306 +--------------+ 307 | IP | 308 +--------------+ 310 Figure 4: Abstract Layering of DOTS signal channel over CoAP over 311 (D)TLS 313 The signal channel is initiated by the DOTS client. Once the signal 314 channel is established, the DOTS agents periodically send heartbeats 315 to keep the channel active. At any time, the DOTS client may send a 316 mitigation request message to the DOTS server over the active 317 channel. While mitigation is active, due to the higher likelihood of 318 packet loss during a DDoS attack, the DOTS server periodically sends 319 status messages to the client, including basic mitigation feedback 320 details. Mitigation remains active until the DOTS client explicitly 321 terminates mitigation, or the mitigation lifetime expires. 323 Messages exchanged between DOTS client and server are serialized 324 using Concise Binary Object Representation (CBOR) [RFC7049], CBOR is 325 a binary encoding designed for small code and message size. CBOR 326 encoded payloads are used to convey signal channel specific payload 327 messages that convey request parameters and response information such 328 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 DOTS agents MUST support GET, PUT, and DELETE CoAP methods. The 335 payload included in CoAP responses with 2.xx and 3.xx Response Codes 336 MUST be of content type "application/cbor" (Section 5.5.1 of 337 [RFC7252]). CoAP responses with 4.xx and 5.xx error Response Codes 338 MUST include a diagnostic payload (Section 5.5.2 of [RFC7252]). The 339 Diagnostic Payload may contain additional information to aid 340 troubleshooting. 342 5.2. DOTS Signal YANG Module 344 This document defines a YANG [RFC6020] module for mitigation scope 345 and DOTS signal channel session configuration data. 347 5.2.1. Mitigation Request YANG Module Tree Structure 349 This document defines the YANG module "ietf-dots-signal", which has 350 the following tree structure: 352 module: ietf-dots-signal 353 +--rw mitigation-scope 354 +--rw client-identifier* binary 355 +--rw scope* [mitigation-id] 356 +--rw mitigation-id int32 357 +--rw target-ip* inet:ip-address 358 +--rw target-prefix* inet:ip-prefix 359 +--rw target-port-range* [lower-port upper-port] 360 | +--rw lower-port inet:port-number 361 | +--rw upper-port inet:port-number 362 +--rw target-protocol* uint8 363 +--rw fqdn* inet:domain-name 364 +--rw uri* inet:uri 365 +--rw alias-name* string 366 +--rw lifetime? int32 368 5.2.2. Mitigation Request YANG Module 370 file "ietf-dots-signal@2017-10-04.yang" 372 module ietf-dots-signal { 373 yang-version 1.1; 374 namespace "urn:ietf:params:xml:ns:yang:ietf-dots-signal"; 375 prefix "signal"; 377 import ietf-inet-types { 378 prefix "inet"; 379 } 381 organization "IETF DOTS Working Group"; 383 contact 384 "Konda, Tirumaleswar Reddy 385 Mohamed Boucadair 386 Prashanth Patil 387 Andrew Mortensen 388 Nik Teague "; 390 description 391 "This module contains YANG definition for DOTS 392 signal sent by the DOTS client to the DOTS server. 394 Copyright (c) 2017 IETF Trust and the persons identified as 395 authors of the code. All rights reserved. 397 Redistribution and use in source and binary forms, with or 398 without modification, is permitted pursuant to, and subject 399 to the license terms contained in, the Simplified BSD License 400 set forth in Section 4.c of the IETF Trust's Legal Provisions 401 Relating to IETF Documents 402 (http://trustee.ietf.org/license-info). 404 This version of this YANG module is part of RFC XXXX; see 405 the RFC itself for full legal notices."; 407 revision 2017-10-04 { 408 description 409 "Add units and fix some nits."; 410 reference 411 "-05"; 412 } 414 revision 2017-08-03 { 415 reference 416 "https://tools.ietf.org/html/draft-reddy-dots-signal-channel"; 417 } 419 container mitigation-scope { 420 description 421 "Top level container for a mitigation request."; 423 leaf-list client-identifier { 424 type binary; 425 description 426 "A client identifier conveyed by a DOTS gateway 427 to a remote DOTS server."; 428 } 430 list scope { 431 key mitigation-id; 432 description "Identifier for the mitigation request."; 434 leaf mitigation-id { 435 type int32; 436 description "Mitigation request identifier."; 437 } 438 leaf-list target-ip { 439 type inet:ip-address; 440 description 441 "IPv4 or IPv6 address identifying the target."; 442 } 444 leaf-list target-prefix { 445 type inet:ip-prefix; 446 description 447 "IPv4 or IPv6 prefix identifying the target."; 448 } 450 list target-port-range { 451 key "lower-port upper-port"; 453 description "Port range. When only lower-port is present, 454 it represents a single port."; 456 leaf lower-port { 457 type inet:port-number; 458 mandatory true; 459 description "Lower port number."; 460 } 462 leaf upper-port { 463 type inet:port-number; 464 must ". >= ../lower-port" { 465 error-message 466 "The upper port number must be greater than or 467 equal to lower port number."; 468 } 469 description "Upper port number."; 470 } 471 } 473 leaf-list target-protocol { 474 type uint8; 475 description "Identifies the target protocol number."; 476 } 478 leaf-list fqdn { 479 type inet:domain-name; 480 description "FQDN"; 481 } 483 leaf-list uri { 484 type inet:uri; 485 description "URI"; 486 } 488 leaf-list alias-name { 489 type string; 490 description "alias name"; 491 } 493 leaf lifetime { 494 type int32; 495 units "seconds"; 496 default 3600; 498 description 499 "Indicates the lifetime of the mitigation request."; 500 } 501 } 502 } 503 } 504 506 5.2.3. Session Configuration YANG Module Tree Structure 508 This document defines the YANG module "ietf-dots-signal-config", 509 which has the following structure: 511 module: ietf-dots-signal-config 512 +--rw signal-config 513 +--rw session-id? int32 514 +--rw heartbeat-interval? int16 515 +--rw missing-hb-allowed? int16 516 +--rw max-retransmit? int16 517 +--rw ack-timeout? int16 518 +--rw ack-random-factor? decimal64 519 +--rw trigger-mitigation? boolean 521 5.2.4. Session Configuration YANG Module 523 file "ietf-dots-signal-config@2017-10-04.yang" 525 module ietf-dots-signal-config { 526 yang-version 1.1; 527 namespace "urn:ietf:params:xml:ns:yang:ietf-dots-signal-config"; 528 prefix "config"; 530 organization "IETF DOTS Working Group"; 532 contact 533 "Konda, Tirumaleswar Reddy 534 Mohamed Boucadair 535 Prashanth Patil 536 Andrew Mortensen 537 Nik Teague "; 539 description 540 "This module contains YANG definition for DOTS 541 signal channel session configuration. 543 Copyright (c) 2017 IETF Trust and the persons identified as 544 authors of the code. All rights reserved. 546 Redistribution and use in source and binary forms, with or 547 without modification, is permitted pursuant to, and subject 548 to the license terms contained in, the Simplified BSD License 549 set forth in Section 4.c of the IETF Trust's Legal Provisions 550 Relating to IETF Documents 551 (http://trustee.ietf.org/license-info). 553 This version of this YANG module is part of RFC XXXX; see 554 the RFC itself for full legal notices."; 556 revision 2017-10-04 { 557 description 558 "Add units/defaults and fix some nits."; 559 reference 560 "-05"; 561 } 563 revision 2016-11-28 { 564 reference 565 "https://tools.ietf.org/html/draft-reddy-dots-signal-channel"; 566 } 568 container signal-config { 569 description "Top level container for DOTS signal channel session 570 configuration."; 572 leaf session-id { 573 type int32; 574 description "An identifier for the DOTS signal channel 575 session configuration data."; 576 } 578 leaf heartbeat-interval { 579 type int16; 580 units "seconds"; 581 default 30; 583 description 584 "DOTS agents regularly send heartbeats to each other 585 after mutual authentication in order to keep 586 the DOTS signal channel open."; 587 } 589 leaf missing-hb-allowed { 590 type int16; 591 default 5; 593 description 594 "Maximum number of missing heartbeats allowed."; 595 } 597 leaf max-retransmit { 598 type int16; 599 default 3; 601 description 602 "Maximum number of retransmissions of a 603 Confirmable message."; 604 } 606 leaf ack-timeout { 607 type int16; 608 units "seconds"; 609 default 2; 611 description 612 "Initial retransmission timeout value."; 613 } 615 leaf ack-random-factor { 616 type decimal64 { 617 fraction-digits 2; 618 } 620 default 1.5; 622 description 623 "Random factor used to influence the timing of 624 retransmissions"; 625 } 626 leaf trigger-mitigation { 627 type boolean; 628 default true; 630 description 631 "If false, then mitigation is triggered 632 only when the DOTS server channel session is lost"; 633 } 634 } 635 } 636 638 5.3. Mitigation Request 640 The following methods are used to request or withdraw mitigation 641 requests: 643 PUT: DOTS clients use the PUT method to request mitigation 644 (Section 5.3.1). During active mitigation, DOTS clients may use 645 PUT requests to convey mitigation efficacy updates to the DOTS 646 server (Section 5.3.4). 648 DELETE: DOTS clients use the DELETE method to withdraw a request for 649 mitigation from the DOTS server (Section 5.3.2). 651 GET: DOTS clients may use the GET method to subscribe to DOTS server 652 status messages, or to retrieve the list of existing mitigations 653 (Section 5.3.3). 655 Mitigation request and response messages are marked as Non- 656 confirmable messages. DOTS agents SHOULD follow the data 657 transmission guidelines discussed in Section 3.1.3 of [RFC8085] and 658 control transmission behavior by not sending on average more than one 659 UDP datagram per RTT to the peer DOTS agent. 661 Requests marked by the DOTS client as Non-confirmable messages are 662 sent at regular intervals until a response is received from the DOTS 663 server and if the DOTS client cannot maintain a RTT estimate then it 664 SHOULD NOT send more than one Non-confirmable request every 3 665 seconds, and SHOULD use an even less aggressive rate when possible 666 (case 2 in Section 3.1.3 of [RFC8085]). 668 5.3.1. Requesting mitigation 670 When a DOTS client requires mitigation for any reason, the DOTS 671 client uses CoAP PUT method to send a mitigation request to the DOTS 672 server (Figure 5, illustrated in JSON diagnostic notation). The DOTS 673 server can enable mitigation on behalf of the DOTS client by 674 communicating the DOTS client's request to the mitigator and relaying 675 selected mitigator feedback to the requesting DOTS client. 677 Header: PUT (Code=0.03) 678 Uri-Host: "host" 679 Uri-Path: "version" 680 Uri-Path: "dots-signal" 681 Uri-Path: "signal" 682 Content-Type: "application/cbor" 683 { 684 "mitigation-scope": { 685 "client-identifier": [ 686 "string" 687 ], 688 "scope": [ 689 { 690 "mitigation-id": integer, 691 "target-ip": [ 692 "string" 693 ], 694 "target-prefix": [ 695 "string" 696 ], 697 "target-port-range": [ 698 { 699 "lower-port": integer, 700 "upper-port": integer 701 } 702 ], 703 "target-protocol": [ 704 integer 705 ], 706 "fqdn": [ 707 "string" 708 ], 709 "uri": [ 710 "string" 711 ], 712 "alias-name": [ 713 "string" 714 ], 715 "lifetime": integer 716 } 717 ] 718 } 719 } 721 Figure 5: PUT to convey DOTS signals 723 The parameters are described below. 725 client-identifier: The client identifier MAY be conveyed by the DOTS 726 gateway to propagate the DOTS client identity from the gateway's 727 client-side to the gateway's server-side, and from the gateway's 728 server-side to the DOTS server. This allows the final DOTS server 729 to accept mitigation requests with scopes which the DOTS client is 730 authorized to manage. 732 The 'client-identifier' value MUST be assigned by the DOTS gateway 733 in a manner that ensures that there is no probability that the 734 same value will be assigned to a different DOTS client. The DOTS 735 gateway MUST obscure potentially sensitive DOTS client identity 736 information. The client-identifier attribute SHOULD NOT to be 737 generated and included by the DOTS client. 739 This is an optional attribute. 741 mitigation-id: Identifier for the mitigation request represented 742 using an integer. This identifier MUST be unique for each 743 mitigation request bound to the DOTS client, i.e., the mitigation- 744 id parameter value in the mitigation request needs to be unique 745 relative to the mitigation-id parameter values of active 746 mitigation requests conveyed from the DOTS client to the DOTS 747 server. This identifier MUST be generated by the DOTS client. 748 This document does not make any assumption about how this 749 identifier is generated. This is a mandatory attribute. 751 target-ip: A list of IP addresses under attack. This is an optional 752 attribute. 754 target-prefix: A list of prefixes under attack. Prefixes are 755 represented using CIDR notation [RFC4632]. This is an optional 756 attribute. 758 target-port-range: A list of ports under attack. The port range, 759 lower-port for lower port number and upper-port for upper port 760 number. When only lower-port is present, it represents a single 761 port. For TCP, UDP, Stream Control Transmission Protocol (SCTP) 762 [RFC4960], or Datagram Congestion Control Protocol (DCCP) 763 [RFC4340]: the range of ports (e.g., 1024-65535). This is an 764 optional attribute. 766 target-protocol: A list of protocols under attack. Values are taken 767 from the IANA protocol registry [proto_numbers]. The value 0 has 768 a special meaning for 'all protocols'. This is an optional 769 attribute. 771 fqdn: A list of Fully Qualified Domain Names. Fully Qualified 772 Domain Name (FQDN) is the full name of a system, rather than just 773 its hostname. For example, "venera" is a hostname, and 774 "venera.isi.edu" is an FQDN. This is an optional attribute. 776 uri: A list of Uniform Resource Identifiers (URI). This is an 777 optional attribute. 779 alias-name: A list of aliases. Aliases can be created using the 780 DOTS data channel (Section 3.1.1 of [I-D.ietf-dots-data-channel]) 781 or direct configuration, or other means and then used in 782 subsequent signal channel exchanges to refer more efficiently to 783 the resources under attack. This is an optional attribute. 785 lifetime: Lifetime of the mitigation request in seconds. The 786 default lifetime of a mitigation request is 3600 seconds (60 787 minutes) -- this value was chosen to be long enough so that 788 refreshing is not typically a burden on the DOTS client, while 789 expiring the request where the client has unexpectedly quit in a 790 timely manner. 792 A lifetime of negative one (-1) indicates indefinite lifetime for 793 the mitigation request. 795 DOTS clients SHOULD include this parameter in their mitigation 796 requests. If no lifetime is supplied by a DOTS client, the DOTS 797 server uses the default lifetime value (3600 seconds). Upon the 798 expiry of this lifetime, and if the request is not refreshed, the 799 mitigation request is removed. The request can be refreshed by 800 sending the same request again. The server MAY refuse indefinite 801 lifetime; the granted lifetime value is returned in the response. 802 The server MUST always indicate the actual lifetime in the 803 response and the remaining lifetime in status messages sent to the 804 client. This is a mandatory parameter for responses. 806 The CBOR key values for the parameters are defined in Section 6. 807 Section 10 defines how the CBOR key values can be allocated to 808 standards bodies and vendors. 810 FQDN and URI mitigation scopes may be thought of as a form of scope 811 alias, in which the addresses to which the domain name or URI resolve 812 represent the full scope of the mitigation. 814 In the PUT request at least one of the attributes 'target-ip' or 815 'target-prefix' or 'fqdn' or 'uri 'or 'alias-name' MUST be present. 816 DOTS agents can safely ignore Vendor-Specific parameters they don't 817 understand. 819 The relative order of two mitigation requests from a DOTS client is 820 determined by comparing their respective 'mitigation-id' values. If 821 two mitigation requests have overlapping mitigation scopes, the 822 mitigation request with higher numeric 'mitigation-id' value will 823 override the mitigation request with a lower numeric 'mitigation-id' 824 value. Two mitigation-ids are overlapping if there is a common IP 825 address, IP prefix, FQDN, URI, or alias-name. The overlapped lower 826 numeric 'mitigation-id' MUST be automatically deleted and no longer 827 available at the DOTS server. 829 The Uri-Path option carries a major and minor version nomenclature to 830 manage versioning and DOTS signal channel in this specification uses 831 v1 major version. 833 If the DOTS client is using the certificate provisioned by the 834 Enrollment over Secure Transport (EST) server [RFC6234] in the DOTS 835 gateway-domain to authenticate itself to the DOTS gateway, then the 836 'client-identifier' value will be the output of a cryptographic hash 837 algorithm whose input is the DER-encoded ASN.1 representation of the 838 Subject Public Key Info (SPKI) of an X.509 certificate. The output 839 of the cryptographic hash algorithm is base64url encoded. In this 840 version of the specification, the cryptographic hash algorithm used 841 is SHA-256 [RFC6234]. If the 'client-identifier' value is already 842 present in the mitigation request received from the DOTS client, the 843 DOTS gateway computes the 'client-identifier' value, as discussed 844 above, and adds the computed 'client-identifier' value to the end of 845 the 'client-identifier' list. The DOTS server MUST NOT use the 846 'client-identifier' for the DOTS client authentication process. 848 In both DOTS signal and data channel sessions, the DOTS client MUST 849 authenticate itself to the DOTS server (Section 9). The DOTS server 850 may use the algorithm in Section 7 of [RFC7589] to derive the DOTS 851 client identity or username from the client certificate. The DOTS 852 client identity allows the DOTS server to accept mitigation requests 853 with scopes which the DOTS client is authorized to manage. The DOTS 854 server couples the DOTS signal and data channel sessions using the 855 DOTS client identity and the 'client-identifier' parameter value, so 856 the DOTS server can validate whether the aliases conveyed in the 857 mitigation request were indeed created by the same DOTS client using 858 the DOTS data channel session. If the aliases were not created by 859 the DOTS client, the DOTS server returns 4.00 (Bad Request) in the 860 response. 862 The DOTS server couples the DOTS signal channel sessions using the 863 DOTS client identity and the 'client-identifier' parameter value, and 864 the DOTS server uses 'mitigation-id' parameter value to detect 865 duplicate mitigation requests. If the mitigation request contains 866 both alias-name and other parameters identifying the target resources 867 (such as, 'target-ip', 'target-prefix', 'target-port-range', 'fqdn', 868 or 'uri'), then the DOTS server appends the parameter values in 869 'alias-name' with the corresponding parameter values in 'target-ip', 870 'target-prefix', 'target-port-range', 'fqdn', or 'uri'. 872 Figure 6 shows a PUT request example to signal that ports 80, 8080, 873 and 443 on the servers 2001:db8:6401::1 and 2001:db8:6401::2 are 874 being attacked (illustrated in JSON diagnostic notation). 876 Header: PUT (Code=0.03) 877 Uri-Host: "www.example.com" 878 Uri-Path: "v1" 879 Uri-Path: "dots-signal" 880 Uri-Path: "signal" 881 Content-Format: "application/cbor" 882 { 883 "mitigation-scope": { 884 "client-identifier": [ 885 "E9CZ9INDbd+2eRQozYqqbQ2yXLVKB9+xcprMF+44U1g=" 886 ], 887 "scope": [ 888 { 889 "mitigation-id": 12332, 890 "target-ip": [ 891 "2001:db8:6401::1", 892 "2001:db8:6401::2" 893 ], 894 "target-port-range": [ 895 { 896 "lower-port": 80 897 }, 898 { 899 "lower-port": 443 900 }, 901 { 902 "lower-port": 8080 903 } 904 ], 905 "target-protocol": [ 906 6 907 ] 908 } 909 ] 910 } 911 } 913 The CBOR encoding format is shown below: 915 A1 # map(1) 916 01 # unsigned(1) 917 A2 # map(2) 918 18 20 # unsigned(32) 919 81 # array(1) 920 78 2C # text(44) 921 4539435A39494E4462642B326552516F7A59717162513279584C564B42392B786370724D462B34345531673D 922 # "E9CZ9INDbd+2eRQozYqqbQ2yXLVKB9+xcprMF+44U1g=" 923 02 # unsigned(2) 924 81 # array(1) 925 A4 # map(4) 926 03 # unsigned(3) 927 19 302C # unsigned(12332) 928 04 # unsigned(4) 929 82 # array(2) 930 70 # text(16) 931 323030313A6462383A363430313A3A31 # "2001:db8:6401::1" 932 70 # text(16) 933 323030313A6462383A363430313A3A32 # "2001:db8:6401::2" 934 05 # unsigned(5) 935 83 # array(3) 936 A1 # map(1) 937 06 # unsigned(6) 938 18 50 # unsigned(80) 939 A1 # map(1) 940 06 # unsigned(6) 941 19 01BB # unsigned(443) 942 A1 # map(1) 943 06 # unsigned(6) 944 19 1F90 # unsigned(8080) 945 08 # unsigned(8) 946 81 # array(1) 947 06 # unsigned(6) 949 Figure 6: PUT for DOTS signal 951 The DOTS server indicates the result of processing the PUT request 952 using CoAP response codes. CoAP 2.xx codes are success. CoAP 4.xx 953 codes are some sort of invalid requests. Figure 7 shows a PUT 954 response for CoAP 2.xx response codes. 956 { 957 "mitigation-scope": { 958 "client-identifier": [ 959 "string" 960 ], 961 "scope": [ 962 { 963 "mitigation-id": integer, 964 "lifetime": integer 965 } 966 ] 967 } 968 } 970 Figure 7: 2.xx response body 972 COAP 5.xx codes are returned if the DOTS server has erred or is 973 currently unavailable to provide mitigation in response to the 974 mitigation request from the DOTS client. 976 If the DOTS server does not find the 'mitigation-id' parameter value 977 conveyed in the PUT request in its configuration data, then the 978 server MAY accept the mitigation request by sending back a 2.01 979 (Created) response to the DOTS client; the DOTS server will 980 consequently try to mitigate the attack. 982 If the DOTS server finds the 'mitigation-id' parameter value conveyed 983 in the PUT request in its configuration data, then the server MAY 984 update the mitigation request, and a 2.04 (Changed) response is 985 returned to indicate a successful update of the mitigation request. 987 If the request is missing one or more mandatory attributes, then 4.00 988 (Bad Request) will be returned in the response or if the request 989 contains invalid or unknown parameters then 4.02 (Invalid query) is 990 returned in the response. 992 For a mitigation request to continue beyond the initial negotiated 993 lifetime, the DOTS client need to refresh the current mitigation 994 request by sending a new PUT request. The PUT request MUST use the 995 same 'mitigation-id' value, and MUST repeat all the other parameters 996 as sent in the original mitigation request apart from a possible 997 change to the lifetime parameter value. 999 A DOTS gateway MUST update the 'client-identifier' list in the 1000 response to remove the 'client-identifier' value it had added in the 1001 corresponding request before forwarding the response to the DOTS 1002 client. 1004 5.3.2. Withdraw a DOTS Signal 1006 A DELETE request is used to withdraw a DOTS signal from a DOTS server 1007 (Figure 8). 1009 Header: DELETE (Code=0.04) 1010 Uri-Host: "host" 1011 Uri-Path: "version" 1012 Uri-Path: "dots-signal" 1013 Uri-Path: "signal" 1014 Content-Format: "application/cbor" 1015 { 1016 "mitigation-scope": { 1017 "client-identifier": [ 1018 "string" 1019 ], 1020 "scope": [ 1021 { 1022 "mitigation-id": integer 1023 } 1024 ] 1025 } 1026 } 1028 Figure 8: Withdraw DOTS signal 1030 The DOTS server immediately acknowledges a DOTS client's request to 1031 withdraw the DOTS signal using 2.02 (Deleted) response code with no 1032 response payload. A 2.02 (Deleted) Response Code is returned even if 1033 the 'mitigation-id' parameter value conveyed in the DELETE request 1034 does not exist in its configuration data before the request. 1036 If the DOTS server finds the 'mitigation-id' parameter value conveyed 1037 in the DELETE request in its configuration data, then to protect 1038 against route or DNS flapping caused by a client rapidly toggling 1039 mitigation, and to dampen the effect of oscillating attacks, DOTS 1040 servers MAY allow mitigation to continue for a limited period after 1041 acknowledging a DOTS client's withdrawal of a mitigation request. 1042 During this period, the DOTS server status messages SHOULD indicate 1043 that mitigation is active but terminating. The active-but- 1044 terminating period MUST be set by default to 30 seconds. If the DOTS 1045 client requests mitigation again before that 30 second expires, the 1046 DOTS server MAY exponentially increase the active-but-terminating 1047 timeout up to a maximum of 240 seconds (4 minutes). After the 1048 active-but-terminating period expires, the DOTS server MUST treat the 1049 mitigation as terminated. That is, the DOTS client is no longer 1050 responsible for the mitigation. For example, if there is a financial 1051 relationship between the DOTS client and server domains, the DOTS 1052 client ceases incurring cost at this point. 1054 5.3.3. Retrieving a DOTS Signal 1056 A GET request is used to retrieve information (including status) of a 1057 DOTS signal from a DOTS server (Figure 9). If the DOTS server does 1058 not find the 'mitigation-id' parameter value conveyed in the GET 1059 request in its configuration data, then it responds with a 4.04 (Not 1060 Found) error response code. The 'c' (content) parameter and its 1061 permitted values defined in [I-D.ietf-core-comi] can be used to 1062 retrieve non-configuration data (attack mitigation status) or 1063 configuration data or both. 1065 1) To retrieve all DOTS signals signaled by the DOTS client. 1067 Header: GET (Code=0.01) 1068 Uri-Host: "host" 1069 Uri-Path: "version" 1070 Uri-Path: "dots-signal" 1071 Uri-Path: "signal" 1072 Observe : 0 1073 { 1074 "mitigation-scope": { 1075 "client-identifier": [ 1076 "string" 1077 ] 1078 } 1079 } 1081 2) To retrieve a specific DOTS signal signaled by the DOTS client. 1082 The configuration data in the response will be formatted in the 1083 same order it was processed at the DOTS server. 1085 Header: GET (Code=0.01) 1086 Uri-Host: "host" 1087 Uri-Path: "version" 1088 Uri-Path: "dots-signal" 1089 Uri-Path: "signal" 1090 Observe : 0 1091 Content-Format: "application/cbor" 1092 { 1093 "mitigation-scope": { 1094 "client-identifier": [ 1095 "string" 1096 ], 1097 "scope": [ 1098 { 1099 "mitigation-id": integer 1100 } 1101 ] 1102 } 1103 } 1105 Figure 9: GET to retrieve the rules 1107 Figure 10 shows a response example of all the active mitigation 1108 requests associated with the DOTS client on the DOTS server and the 1109 mitigation status of each mitigation request. 1111 { 1112 "mitigation-scope": { 1113 "scope": [ 1114 { 1115 "mitigation-id": 12332, 1116 "mitigation-start": 1507818434.00, 1117 "target-protocol": [ 1118 17 1119 ], 1120 "lifetime":1800, 1121 "status":2, 1122 "bytes-dropped": 134334555, 1123 "bps-dropped": 43344, 1124 "pkts-dropped": 333334444, 1125 "pps-dropped": 432432 1126 }, 1127 { 1128 "mitigation-id": 12333, 1129 "mitigation-start": 1507818393.00, 1130 "target-protocol": [ 1131 6 1132 ], 1133 "lifetime":1800, 1134 "status":3 1135 "bytes-dropped": 0, 1136 "bps-dropped": 0, 1137 "pkts-dropped": 0, 1138 "pps-dropped": 0 1139 } 1140 ] 1141 } 1142 } 1144 Figure 10: Response body 1146 The mitigation status parameters are described below. 1148 lifetime: The remaining lifetime of the mitigation request in 1149 seconds. 1151 mitigation-start: Mitigation start time is represented in seconds 1152 relative to 1970-01-01T00:00Z in UTC time (Section 2.4.1 of 1153 [RFC7049]). The encoding is modified so that the leading tag 1 1154 (epoch-based date/time) MUST be omitted. 1156 bytes-dropped: The total dropped byte count for the mitigation 1157 request since the attack mitigation is triggered. The count wraps 1158 around when it reaches the maximum value of unsigned integer. 1159 This is an optional attribute. 1161 bps-dropped: The average dropped bytes per second for the mitigation 1162 request since the attack mitigation is triggered. This SHOULD be 1163 a five-minute average. This is an optional attribute. 1165 pkts-dropped: The total dropped packet count for the mitigation 1166 request since the attack mitigation is triggered. This is an 1167 optional attribute. 1169 pps-dropped: The average dropped packets per second for the 1170 mitigation request since the attack mitigation is triggered. This 1171 SHOULD be a five-minute average. This is an optional attribute. 1173 status: Status of attack mitigation. The 'status' parameter is a 1174 mandatory attribute. 1176 The various possible values of 'status' parameter are explained 1177 below: 1179 /--------------------+---------------------------------------------------\ 1180 | Parameter value | Description | 1181 +--------------------+---------------------------------------------------+ 1182 | 1 | Attack mitigation is in progress | 1183 | | (e.g., changing the network path to re-route the | 1184 | | inbound traffic to DOTS mitigator). | 1185 +--------------------+---------------------------------------------------+ 1186 | 2 | Attack is successfully mitigated | 1187 | | (e.g., traffic is redirected to a DDOS mitigator | 1188 | | and attack traffic is dropped). | 1189 +--------------------+---------------------------------------------------+ 1190 | 3 | Attack has stopped and the DOTS client | 1191 | | can withdraw the mitigation request. | 1192 +--------------------+---------------------------------------------------+ 1193 | 4 | Attack has exceeded the mitigation provider | 1194 | | capability. | 1195 +--------------------+---------------------------------------------------+ 1196 | 5 | DOTS client has withdrawn the mitigation request | 1197 | | and the mitigation is active but terminating. | 1198 \--------------------+---------------------------------------------------/ 1200 The observe option defined in [RFC7641] extends the CoAP core 1201 protocol with a mechanism for a CoAP client to "observe" a resource 1202 on a CoAP server: the client retrieves a representation of the 1203 resource and requests this representation be updated by the server as 1204 long as the client is interested in the resource. A DOTS client 1205 conveys the observe option set to 0 in the GET request to receive 1206 unsolicited notifications of attack mitigation status from the DOTS 1207 server. Unidirectional notifications within the bidirectional signal 1208 channel allows unsolicited message delivery, enabling asynchronous 1209 notifications between the agents. Due to the higher likelihood of 1210 packet loss during a DDoS attack, DOTS server periodically sends 1211 attack mitigation status to the DOTS client and also notifies the 1212 DOTS client whenever the status of the attack mitigation changes. If 1213 the DOTS server cannot maintain a RTT estimate then it SHOULD NOT 1214 send more than one unsolicited notification every 3 seconds, and 1215 SHOULD use an even less aggressive rate when possible (case 2 in 1216 Section 3.1.3 of [RFC8085]). A DOTS client that is no longer 1217 interested in receiving notifications from the DOTS server can simply 1218 "forget" the observation. When the DOTS server then sends the next 1219 notification, the DOTS client will not recognize the token in the 1220 message and thus will return a Reset message. This causes the DOTS 1221 server to remove the associated entry. Alternatively, the DOTS 1222 client can explicitly deregister by issuing a GET request that has 1223 the Token field set to the token of the observation to be cancelled 1224 and includes an Observe Option with the value set to 1 (deregister). 1226 DOTS Client DOTS Server 1227 | | 1228 | GET / | 1229 | Token: 0x4a | Registration 1230 | Observe: 0 | 1231 +------------------------------>| 1232 | | 1233 | 2.05 Content | 1234 | Token: 0x4a | Notification of 1235 | Observe: 12 | the current state 1236 | status: "mitigation | 1237 | in progress" | 1238 |<------------------------------+ 1239 | 2.05 Content | 1240 | Token: 0x4a | Notification upon 1241 | Observe: 44 | a state change 1242 | status: "mitigation | 1243 | complete" | 1244 |<------------------------------+ 1245 | 2.05 Content | 1246 | Token: 0x4a | Notification upon 1247 | Observe: 60 | a state change 1248 | status: "attack stopped" | 1249 |<------------------------------+ 1250 | | 1252 Figure 11: Notifications of attack mitigation status 1254 5.3.3.1. Mitigation Status 1256 The DOTS client can send the GET request at frequent intervals 1257 without the Observe option to retrieve the configuration data of the 1258 mitigation request and non-configuration data (i.e., the attack 1259 status). The frequency of polling the DOTS server to get the 1260 mitigation status should follow the transmission guidelines given in 1261 Section 3.1.3 of [RFC8085]. If the DOTS server has been able to 1262 mitigate the attack and the attack has stopped, the DOTS server 1263 indicates as such in the status, and the DOTS client recalls the 1264 mitigation request by issuing a DELETE for the mitigation-id. 1266 A DOTS client should react to the status of the attack from the DOTS 1267 server and not the fact that it has recognized, using its own means, 1268 that the attack has been mitigated. This ensures that the DOTS 1269 client does not recall a mitigation request in a premature fashion 1270 because it is possible that the DOTS client does not sense the DDOS 1271 attack on its resources but the DOTS server could be actively 1272 mitigating the attack and the attack is not completely averted. 1274 5.3.4. Efficacy Update from DOTS Client 1276 While DDoS mitigation is active, due to the likelihood of packet 1277 loss, a DOTS client MAY periodically transmit DOTS mitigation 1278 efficacy updates to the relevant DOTS server. A PUT request 1279 (Figure 12) is used to convey the mitigation efficacy update to the 1280 DOTS server. 1282 The PUT request MUST include all the parameters used in the PUT 1283 request to convey the DOTS signal (Section 5.3.1) unchanged apart 1284 from the lifetime parameter value. If this is not the case, the DOTS 1285 server MUST reject the request with a 4.02 error response code. 1287 The If-Match Option (Section 5.10.8.1 of [RFC7252]) with an empty 1288 value is used to make the PUT request conditional on the current 1289 existence of the mitigation request. If UDP is used as transport, 1290 CoAP requests may arrive out-of-order. For example, the DOTS client 1291 may send a PUT request to convey an efficacy update to the DOTS 1292 server followed by a DELETE request to withdraw the mitigation 1293 request, but the DELETE request arrives at the DOTS server before the 1294 PUT request. To handle out-of-order delivery of requests, if an If- 1295 Match option is present in the PUT request and the 'mitigation-id' in 1296 the request matches a mitigation request from that DOTS client, then 1297 the request is processed. If no match is found, the PUT request is 1298 silently ignored. 1300 Header: PUT (Code=0.03) 1301 Uri-Host: "host" 1302 Uri-Path: "version" 1303 Uri-Path: "dots-signal" 1304 Uri-Path: "signal" 1305 Content-Format: "application/cbor" 1306 { 1307 "mitigation-scope": { 1308 "client-identifier": [ 1309 "string" 1310 ], 1311 "scope": [ 1312 { 1313 "mitigation-id": integer, 1314 "target-ip": [ 1315 "string" 1316 ], 1317 "target-port-range": [ 1318 { 1319 "lower-port": integer, 1320 "upper-port": integer 1321 } 1322 ], 1323 "target-protocol": [ 1324 integer 1325 ], 1326 "fqdn": [ 1327 "string" 1328 ], 1329 "uri": [ 1330 "string" 1331 ], 1332 "alias-name": [ 1333 "string" 1334 ], 1335 "lifetime": integer, 1336 "attack-status": integer 1337 } 1338 ] 1339 } 1340 } 1342 Figure 12: Efficacy Update 1344 The 'attack-status' parameter is a mandatory attribute when doing a 1345 efficacy update. The various possible values contained in the 1346 'attack-status' parameter are described below: 1348 /--------------------+------------------------------------------------------\ 1349 | Parameter value | Description | 1350 +--------------------+------------------------------------------------------+ 1351 | 1 | DOTS client determines that it is still under attack.| 1352 +--------------------+------------------------------------------------------+ 1353 | 2 | DOTS client determines that the attack is | 1354 | | successfully mitigated | 1355 | | (e.g., attack traffic is not seen). | 1356 \--------------------+------------------------------------------------------/ 1358 The DOTS server indicates the result of processing a PUT request 1359 using CoAP response codes. The response code 2.04 (Changed) is 1360 returned if the DOTS server has accepted the mitigation efficacy 1361 update. The error response code 5.03 (Service Unavailable) is 1362 returned if the DOTS server has erred or is incapable of performing 1363 the mitigation. 1365 5.4. DOTS Signal Channel Session Configuration 1367 The DOTS client can negotiate, configure, and retrieve the DOTS 1368 signal channel session behavior. The DOTS signal channel can be 1369 used, for example, to configure the following: 1371 a. Heartbeat interval: DOTS agents regularly send heartbeats (CoAP 1372 Ping/Pong) to each other after mutual authentication in order to 1373 keep the DOTS signal channel open, heartbeat messages are 1374 exchanged between the DOTS agents every heartbeat-interval 1375 seconds to detect the current status of the DOTS signal channel 1376 session. 1378 b. Missing heartbeats allowed: This variable indicates the maximum 1379 number of consecutive heartbeat messages for which a DOTS agent 1380 did not receive a response before concluding that the session is 1381 disconnected or defunct. 1383 c. Acceptable signal loss ratio: Maximum retransmissions, 1384 retransmission timeout value and other message transmission 1385 parameters for the DOTS signal channel. 1387 Reliability is provided to requests and responses by marking them as 1388 Confirmable (CON) messages. DOTS signal channel session 1389 configuration requests and responses are marked as Confirmable (CON) 1390 messages. As explained in Section 2.1 of [RFC7252], a Confirmable 1391 message is retransmitted using a default timeout and exponential 1392 back-off between retransmissions, until the DOTS server sends an 1393 Acknowledgement message (ACK) with the same Message ID conveyed from 1394 the DOTS client. Message transmission parameters are defined in 1395 Section 4.8 of [RFC7252]. Reliability is provided to the responses 1396 by marking them as Confirmable (CON) messages. The DOTS server can 1397 either piggyback the response in the acknowledgement message or if 1398 the DOTS server is not able to respond immediately to a request 1399 carried in a Confirmable message, it simply responds with an Empty 1400 Acknowledgement message so that the DOTS client can stop 1401 retransmitting the request. Empty Acknowledgement message is 1402 explained in Section 2.2 of [RFC7252]. When the response is ready, 1403 the server sends it in a new Confirmable message which then in turn 1404 needs to be acknowledged by the DOTS client (see Sections 5.2.1 and 1405 Sections 5.2.2 of [RFC7252]). Requests and responses exchanged 1406 between DOTS agents during peacetime are marked as Confirmable 1407 messages. 1409 Implementation Note: A DOTS client that receives a response in a CON 1410 message may want to clean up the message state right after sending 1411 the ACK. If that ACK is lost and the DOTS server retransmits the 1412 CON, the DOTS client may no longer have any state to which to 1413 correlate this response, making the retransmission an unexpected 1414 message; the DOTS client will send a Reset message so it does not 1415 receive any more retransmissions. This behavior is normal and not an 1416 indication of an error (see Section 5.3.2 of [RFC7252] for more 1417 details). 1419 5.4.1. Discover Configuration Parameters 1421 A GET request is used to obtain acceptable and current configuration 1422 parameters on the DOTS server for DOTS signal channel session 1423 configuration. Figure 13 shows how to obtain acceptable 1424 configuration parameters for the server. 1426 Header: GET (Code=0.01) 1427 Uri-Host: "host" 1428 Uri-Path: "version" 1429 Uri-Path: "dots-signal" 1430 Uri-Path: "config" 1432 Figure 13: GET to retrieve configuration 1434 The DOTS server in the 2.05 (Content) response conveys the current, 1435 minimum and maximum attribute values acceptable by the DOTS server. 1437 Content-Format: "application/cbor" 1438 { 1439 "heartbeat-interval": { 1440 "CurrentValue": integer, 1441 "MinValue": integer, 1442 "MaxValue" : integer, 1443 }, 1444 "missing-hb-allowed": { 1445 "CurrentValue": integer, 1446 "MinValue": integer, 1447 "MaxValue" : integer, 1448 }, 1449 "max-retransmit": { 1450 "CurrentValue": integer, 1451 "MinValue": integer, 1452 "MaxValue" : integer, 1453 }, 1454 "ack-timeout": { 1455 "CurrentValue": integer, 1456 "MinValue": integer, 1457 "MaxValue" : integer, 1458 }, 1459 "ack-random-factor": { 1460 "CurrentValue": number, 1461 "MinValue": number, 1462 "MaxValue" : number, 1463 }, 1464 "trigger-mitigation": { 1465 "CurrentValue": boolean, 1466 } 1467 } 1469 Figure 14: GET response body 1471 Figure 15 shows an example of acceptable and current configuration 1472 parameters on the DOTS server for DOTS signal channel session 1473 configuration. 1475 Content-Format: "application/cbor" 1476 { 1477 "heartbeat-interval": { 1478 "CurrentValue": 30, 1479 "MinValue": 15, 1480 "MaxValue" : 240, 1481 }, 1482 "missing-hb-allowed": { 1483 "CurrentValue": 5, 1484 "MinValue": 3, 1485 "MaxValue" : 9, 1486 }, 1487 "max-retransmit": { 1488 "CurrentValue": 3, 1489 "MinValue": 2, 1490 "MaxValue" : 15, 1491 }, 1492 "ack-timeout": { 1493 "CurrentValue": 2, 1494 "MinValue": 1, 1495 "MaxValue" : 30, 1496 }, 1497 "ack-random-factor": { 1498 "CurrentValue": 1.5, 1499 "MinValue": 1.1, 1500 "MaxValue" : 4.0, 1501 }, 1502 "trigger-mitigation": { 1503 "CurrentValue": true, 1504 } 1505 } 1507 Figure 15: configuration response body 1509 5.4.2. Convey DOTS Signal Channel Session Configuration 1511 A PUT request is used to convey the configuration parameters for the 1512 signaling channel (e.g., heartbeat interval, maximum 1513 retransmissions). Message transmission parameters for CoAP are 1514 defined in Section 4.8 of [RFC7252]. The RECOMMENDED values of 1515 transmission parameter values are ack_timeout (2 seconds), max- 1516 retransmit (3), ack-random-factor (1.5). In addition to those 1517 parameters, the RECOMMENDED specific DOTS transmission parameter 1518 values are heartbeat-interval (30 seconds) and missing-hb-allowed 1519 (5). 1521 Note: heartbeat-interval should be tweaked to also assist DOTS 1522 messages for NAT traversal (SIG-010 of 1524 [I-D.ietf-dots-requirements]). According to [RFC8085], keepalive 1525 messages must not be sent more frequently than once every 15 1526 seconds and should use longer intervals when possible. 1527 Furthermore, [RFC4787] recommends NATs to use a state timeout of 2 1528 minutes or longer, but experience shows that sending packets every 1529 15 to 30 seconds is necessary to prevent the majority of 1530 middleboxes from losing state for UDP flows. From that 1531 standpoint, this specification recommends a minimum heartbeat- 1532 interval of 15 seconds and a maximum heartbeat-interval of 240 1533 seconds. The recommended value of 30 seconds is selected to 1534 anticipate the expiry of NAT state. 1536 A heartbeat-interval of 30 second may be seen as too chatty in 1537 some deployments. For such deployments, DOTS agents may negotiate 1538 longer heartbeat-interval values to avoid overloading the network 1539 with too frequent keepalives. 1541 When a confirmable "CoAP ping" is sent, and if there is no response, 1542 the "CoAP ping" will get retransmitted max-retransmit number of times 1543 by the CoAP layer using an initial timeout set to a random duration 1544 between ack_timeout and (ack-timeout*ack-random-factor) and 1545 exponential back-off between retransmissions. By choosing the 1546 recommended transmission parameters, the "CoAP ping" will timeout 1547 after 45 seconds. If the DOTS agent does not receive any response 1548 from the peer DOTS agent for missing-hb-allowed number of consecutive 1549 "CoAP ping" confirmable messages, then it concludes that the DOTS 1550 signal channel session is disconnected. A DOTS client MUST NOT 1551 transmit a "CoAP ping" while waiting for the previous "CoAP ping" 1552 response from the same DOTS server. 1554 If the DOTS agent wishes to change the default values of message 1555 transmission parameters, then it should follow the guidance given in 1556 Section 4.8.1 of [RFC7252]. The DOTS agents MUST use the negotiated 1557 values for message transmission parameters and default values for 1558 non-negotiated message transmission parameters. 1560 The signaling channel session configuration is applicable to a single 1561 DOTS signal channel session between the DOTS agents. 1563 Header: PUT (Code=0.03) 1564 Uri-Host: "host" 1565 Uri-Path: "version" 1566 Uri-Path: "dots-signal" 1567 Uri-Path: "config" 1568 Content-Format: "application/cbor" 1569 { 1570 "signal-config": { 1571 "session-id": integer, 1572 "heartbeat-interval": integer, 1573 "missing-hb-allowed": integer, 1574 "max-retransmit": integer, 1575 "ack-timeout": integer, 1576 "ack-random-factor": number 1577 "trigger-mitigation": boolean 1578 } 1579 } 1581 Figure 16: PUT to convey the DOTS signal channel session 1582 configuration data. 1584 The parameters are described below: 1586 session-id: Identifier for the DOTS signal channel session 1587 configuration data represented as an integer. This identifier 1588 MUST be generated by the DOTS client. This document does not make 1589 any assumption about how this identifier is generated. This is a 1590 mandatory attribute. 1592 heartbeat-interval: Time interval in seconds between two 1593 consecutive heartbeat messages. This is an optional attribute. 1595 missing-hb-allowed: Maximum number of consecutive heartbeat 1596 messages for which the DOTS agent did not receive a response 1597 before concluding that the session is disconnected. This is an 1598 optional attribute. 1600 max-retransmit: Maximum number of retransmissions for a message 1601 (referred to as MAX_RETRANSMIT parameter in CoAP). This is an 1602 optional attribute. 1604 ack-timeout: Timeout value in seconds used to calculate the initial 1605 retransmission timeout value (referred to as ACK_TIMEOUT parameter 1606 in CoAP). This is an optional attribute. 1608 ack-random-factor: Random factor used to influence the timing of 1609 retransmissions (referred to as ACK_RANDOM_FACTOR parameter in 1610 CoAP). This is an optional attribute. 1612 trigger-mitigation: If the parameter value is set to 'false', then 1613 DDoS mitigation is triggered only when the DOTS signal channel 1614 session is lost. Automated mitigation on loss of signal is 1615 discussed in Section 3.3.3 of [I-D.ietf-dots-architecture]. If 1616 the DOTS client ceases to respond to heartbeat messages, then the 1617 DOTS server can detect that the DOTS session is lost. The default 1618 value of the parameter is 'true'. This is an optional attribute. 1620 In the PUT request at least one of the attributes heartbeat-interval, 1621 missing-hb-allowed, max-retransmit, ack-timeout, ack-random-factor, 1622 and trigger-mitigation MUST be present. The PUT request with higher 1623 numeric session-id value over-rides the DOTS signal channel session 1624 configuration data installed by a PUT request with a lower numeric 1625 session-id value. 1627 Figure 17 shows a PUT request example to convey the configuration 1628 parameters for the DOTS signal channel. 1630 Header: PUT (Code=0.03) 1631 Uri-Host: "www.example.com" 1632 Uri-Path: "v1" 1633 Uri-Path: "dots-signal" 1634 Uri-Path: "config" 1635 Content-Format: "application/cbor" 1636 { 1637 "signal-config": { 1638 "session-id": 1234534333242, 1639 "heartbeat-interval": 91, 1640 "missing-hb-allowed": 3, 1641 "max-retransmit": 7, 1642 "ack-timeout": 5, 1643 "ack-random-factor": 1.5, 1644 "trigger-mitigation": false 1645 } 1646 } 1648 Figure 17: PUT to convey the configuration parameters 1650 The DOTS server indicates the result of processing the PUT request 1651 using CoAP response codes: 1653 o If the DOTS server finds the 'session-id' parameter value conveyed 1654 in the PUT request in its configuration data and if the DOTS 1655 server has accepted the updated configuration parameters, then 1656 2.04 (Changed) code is returned in the response. 1658 o If the DOTS server does not find the 'session-id' parameter value 1659 conveyed in the PUT request in its configuration data and if the 1660 DOTS server has accepted the configuration parameters, then a 1661 response code 2.01 (Created) is returned in the response. 1663 o If the request is missing one or more mandatory attributes, then 1664 4.00 (Bad Request) is returned in the response. 1666 o If the request contains one or more invalid or unknown parameters, 1667 then 4.02 (Invalid query) code is returned in the response. 1669 o Response code 4.22 (Unprocessable Entity) is returned in the 1670 response, if any of the heartbeat-interval, missing-hb-allowed, 1671 max-retransmit, target-protocol, ack-timeout, and ack-random- 1672 factor attribute values are not acceptable to the DOTS server. 1673 Upon receipt of the 4.22 error response code, the DOTS client 1674 should request the maximum and minimum attribute values acceptable 1675 to the DOTS server (Section 5.4.1). The DOTS client may re-try 1676 and send the PUT request with updated attribute values acceptable 1677 to the DOTS server. 1679 5.4.3. Delete DOTS Signal Channel Session Configuration 1681 A DELETE request is used to delete the installed DOTS signal channel 1682 session configuration data (Figure 18). 1684 Header: DELETE (Code=0.04) 1685 Uri-Host: "host" 1686 Uri-Path: "version" 1687 Uri-Path: "dots-signal" 1688 Uri-Path: "config" 1689 Content-Format: "application/cbor" 1691 Figure 18: DELETE configuration 1693 The DOTS server resets the DOTS signal channel session configuration 1694 back to the default values and acknowledges a DOTS client's request 1695 to remove the DOTS signal channel session configuration using 2.02 1696 (Deleted) response code. 1698 5.5. Redirected Signaling 1700 Redirected Signaling is discussed in detail in Section 3.2.2 of 1701 [I-D.ietf-dots-architecture]. If the DOTS server wants to redirect 1702 the DOTS client to an alternative DOTS server for a signaling session 1703 then the response code 3.00 (alternate server) will be returned in 1704 the response to the client. The DOTS server can return the error 1705 response code 3.00 in response to a PUT request from the DOTS client 1706 or convey the error response code 3.00 in a unidirectional 1707 notification response from the DOTS server. 1709 The DOTS server in the error response conveys the alternate DOTS 1710 server FQDN, and the alternate DOTS server IP addresses and time to 1711 live values in the CBOR body. 1713 { 1714 "alt-server": "string", 1715 "alt-server-record": [ 1716 { 1717 "addr": "string", 1718 "ttl" : integer, 1719 } 1720 ] 1721 } 1723 Figure 19: Error response body 1725 The parameters are described below: 1727 alt-server: FQDN of an alternate DOTS server. 1729 addr: IP address of an alternate DOTS server. 1731 ttl: Time to live (TTL) represented as an integer number of seconds. 1733 Figure 20 shows a 3.00 response example to convey the DOTS alternate 1734 server www.example-alt.com, its IP addresses 2001:db8:6401::1 and 1735 2001:db8:6401::2, and TTL values 3600 and 1800. 1737 { 1739 "alt-server": "www.example-alt.com", 1740 "alt-server-record": [ 1741 { 1742 "ttl" : 3600, 1743 "addr": "2001:db8:6401::1" 1744 }, 1745 { 1746 "ttl" : 1800, 1747 "addr": "2001:db8:6401::2" 1748 } 1749 ] 1750 } 1752 Figure 20: Example of error response body 1754 When the DOTS client receives 3.00 response, it considers the current 1755 request as having failed, but SHOULD try the request with the 1756 alternate DOTS server. During a DDOS attack, the DNS server may be 1757 subjected to DDOS attack, alternate DOTS server IP addresses conveyed 1758 in the 3.00 response help the DOTS client to skip DNS lookup of the 1759 alternate DOTS server and can try to establish UDP or TCP session 1760 with the alternate DOTS server IP addresses. The DOTS client SHOULD 1761 implement DNS64 function to handle the scenario where IPv6-only DOTS 1762 client communicates with IPv4-only alternate DOTS server. 1764 5.6. Heartbeat Mechanism 1766 To provide a metric of signal health and distinguish an 'idle' signal 1767 channel from a 'disconnected' or 'defunct' session, the DOTS agent 1768 sends a heartbeat over the signal channel to maintain its half of the 1769 channel. The DOTS agent similarly expects a heartbeat from its peer 1770 DOTS agent, and may consider a session terminated in the extended 1771 absence of a peer agent heartbeat. 1773 While the communication between the DOTS agents is quiescent, the 1774 DOTS client will probe the DOTS server to ensure it has maintained 1775 cryptographic state and vice versa. Such probes can also keep alive 1776 firewall and/or NAT bindings. This probing reduces the frequency of 1777 establishing a new handshake when a DOTS signal needs to be conveyed 1778 to the DOTS server. 1780 In DOTS over UDP, heartbeat messages may be exchanged between the 1781 DOTS agents using the "COAP ping" mechanism defined in Section 4.2 of 1782 [RFC7252]. Concretely, the DOTS agent sends an Empty Confirmable 1783 message and the peer DOTS agent will respond by sending an Reset 1784 message. 1786 In DOTS over TCP, heartbeat messages can be exchanged between the 1787 DOTS agents using the Ping and Pong messages specified in Section 4.4 1788 of [I-D.ietf-core-coap-tcp-tls]. That is, the DOTS agent sends a 1789 Ping message and the peer DOTS agent would respond by sending a 1790 single Pong message. 1792 6. Mapping parameters to CBOR 1794 All parameters in the payload in the DOTS signal channel MUST be 1795 mapped to CBOR types as follows and are given an integer key to save 1796 space. The recipient of the payload MAY reject the information if it 1797 is not suitably mapped. 1799 /--------------------+------------------------+--------------------------\ 1800 | Parameter name | CBOR key | CBOR major type of value | 1801 +--------------------+------------------------+--------------------------+ 1802 | mitigation-scope | 1 | 5 (map) | 1803 | scope | 2 | 5 (map) | 1804 | mitigation-id | 3 | 0 (unsigned) | 1805 | target-ip | 4 | 4 (array) | 1806 | target-port-range | 5 | 4 | 1807 | lower-port | 6 | 0 | 1808 | upper-port | 7 | 0 | 1809 | target-protocol | 8 | 4 | 1810 | fqdn | 9 | 4 | 1811 | uri | 10 | 4 | 1812 | alias-name | 11 | 4 | 1813 | lifetime | 12 | 0 | 1814 | attack-status | 13 | 0 | 1815 | signal-config | 14 | 5 | 1816 | heartbeat-interval | 15 | 0 | 1817 | max-retransmit | 16 | 0 | 1818 | ack-timeout | 17 | 0 | 1819 | ack-random-factor | 18 | 7 | 1820 | MinValue | 19 | 0 | 1821 | MaxValue | 20 | 0 | 1822 | status | 21 | 0 | 1823 | bytes-dropped | 22 | 0 | 1824 | bps-dropped | 23 | 0 | 1825 | pkts-dropped | 24 | 0 | 1826 | pps-dropped | 25 | 0 | 1827 | session-id | 26 | 0 | 1828 | trigger-mitigation | 27 | 7 (simple types) | 1829 | missing-hb-allowed | 28 | 0 | 1830 | CurrentValue | 29 | 0 | 1831 | mitigation-start | 30 | 7 (floating-point) | 1832 | target-prefix | 31 | 4 (array) | 1833 | client-identifier | 32 | 2 (byte string) | 1834 \--------------------+------------------------+--------------------------/ 1836 Figure 21: CBOR mappings used in DOTS signal channel message 1838 7. (D)TLS Protocol Profile and Performance considerations 1840 This section defines the (D)TLS protocol profile of DOTS signal 1841 channel over (D)TLS and DOTS data channel over TLS. 1843 There are known attacks on (D)TLS, such as machine-in-the-middle and 1844 protocol downgrade. These are general attacks on (D)TLS and not 1845 specific to DOTS over (D)TLS; please refer to the (D)TLS RFCs for 1846 discussion of these security issues. DOTS agents MUST adhere to the 1847 (D)TLS implementation recommendations and security considerations of 1848 [RFC7525] except with respect to (D)TLS version. Since encryption of 1849 DOTS using (D)TLS is virtually a green-field deployment DOTS agents 1850 MUST implement only (D)TLS 1.2 or later. 1852 Implementations compliant with this profile MUST implement all of the 1853 following items: 1855 o DOTS agents MUST support DTLS record replay detection (Section 3.3 1856 of [RFC6347]) to protect against replay attacks. 1858 o DOTS client can use (D)TLS session resumption without server-side 1859 state [RFC5077] to resume session and convey the DOTS signal. 1861 o Raw public keys [RFC7250] which reduce the size of the 1862 ServerHello, and can be used by servers that cannot obtain 1863 certificates (e.g., DOTS gateways on private networks). 1865 Implementations compliant with this profile SHOULD implement all of 1866 the following items to reduce the delay required to deliver a DOTS 1867 signal: 1869 o TLS False Start [RFC7918] which reduces round-trips by allowing 1870 the TLS second flight of messages (ChangeCipherSpec) to also 1871 contain the DOTS signal. 1873 o Cached Information Extension [RFC7924] which avoids transmitting 1874 the server's certificate and certificate chain if the client has 1875 cached that information from a previous TLS handshake. 1877 o TCP Fast Open [RFC7413] can reduce the number of round-trips to 1878 convey DOTS signal. 1880 7.1. MTU and Fragmentation Issues 1882 To avoid DOTS signal message fragmentation and the consequently 1883 decreased probability of message delivery, DOTS agents MUST ensure 1884 that the DTLS record MUST fit within a single datagram. If the Path 1885 MTU is not known to the DOTS server, an IP MTU of 1280 bytes SHOULD 1886 be assumed. The length of the URL MUST NOT exceed 256 bytes. If UDP 1887 is used to convey the DOTS signal messages then the DOTS client must 1888 consider the amount of record expansion expected by the DTLS 1889 processing when calculating the size of CoAP message that fits within 1890 the path MTU. Path MTU MUST be greater than or equal to [CoAP 1891 message size + DTLS overhead of 13 octets + authentication overhead 1892 of the negotiated DTLS cipher suite + block padding (Section 4.1.1.1 1893 of [RFC6347]]. If the request size exceeds the Path MTU then the 1894 DOTS client MUST split the DOTS signal into separate messages, for 1895 example the list of addresses in the 'target-ip' parameter could be 1896 split into multiple lists and each list conveyed in a new PUT 1897 request. 1899 Implementation Note: DOTS choice of message size parameters works 1900 well with IPv6 and with most of today's IPv4 paths. However, with 1901 IPv4, it is harder to absolutely ensure that there is no IP 1902 fragmentation. If IPv4 support on unusual networks is a 1903 consideration and path MTU is unknown, implementations may want to 1904 limit themselves to more conservative IPv4 datagram sizes such as 576 1905 bytes, as per [RFC0791] IP packets up to 576 bytes should never need 1906 to be fragmented, thus sending a maximum of 500 bytes of DOTS signal 1907 over a UDP datagram will generally avoid IP fragmentation. 1909 8. (D)TLS 1.3 considerations 1911 TLS 1.3 [I-D.ietf-tls-tls13] provides critical latency improvements 1912 for connection establishment over TLS 1.2. The DTLS 1.3 protocol 1913 [I-D.rescorla-tls-dtls13] is based on the TLS 1.3 protocol and 1914 provides equivalent security guarantees. (D)TLS 1.3 provides two 1915 basic handshake modes of interest to DOTS signal channel: 1917 o Absent packet loss, a full handshake in which the DOTS client is 1918 able to send the DOTS signal message after one round trip and the 1919 DOTS server immediately after receiving the first DOTS signal 1920 message from the client. 1922 o 0-RTT mode in which the DOTS client can authenticate itself and 1923 send DOTS signal message on its first flight, thus reducing 1924 handshake latency. 0-RTT only works if the DOTS client has 1925 previously communicated with that DOTS server, which is very 1926 likely with the DOTS signal channel. The DOTS client SHOULD 1927 establish a (D)TLS session with the DOTS server during peacetime 1928 and share a PSK. During DDOS attack, the DOTS client can use the 1929 (D)TLS session to convey the DOTS signal message and if there is 1930 no response from the server after multiple re-tries then the DOTS 1931 client can resume the (D)TLS session in 0-RTT mode using PSK. A 1932 simplified TLS 1.3 handshake with 0-RTT DOTS signal message 1933 exchange is shown in Figure 22. 1935 DOTS Client DOTS Server 1937 ClientHello 1938 (Finished) 1939 (0-RTT DOTS signal message) 1940 (end_of_early_data) --------> 1941 ServerHello 1942 {EncryptedExtensions} 1943 {ServerConfiguration} 1944 {Certificate} 1945 {CertificateVerify} 1946 {Finished} 1947 <-------- [DOTS signal message] 1948 {Finished} --------> 1950 [DOTS signal message] <-------> [DOTS signal message] 1952 Figure 22: TLS 1.3 handshake with 0-RTT 1954 9. Mutual Authentication of DOTS Agents & Authorization of DOTS Clients 1956 (D)TLS based on client certificate can be used for mutual 1957 authentication between DOTS agents. If a DOTS gateway is involved, 1958 DOTS clients and DOTS gateway MUST perform mutual authentication; 1959 only authorized DOTS clients are allowed to send DOTS signals to a 1960 DOTS gateway. DOTS gateway and DOTS server MUST perform mutual 1961 authentication; DOTS server only allows DOTS signals from authorized 1962 DOTS gateway, creating a two-link chain of transitive authentication 1963 between the DOTS client and the DOTS server. 1965 +-------------------------------------------------+ 1966 | example.com domain +---------+ | 1967 | | AAA | | 1968 | +---------------+ | Server | | 1969 | | Application | +------+--+ | 1970 | | server + ^ 1971 | | (DOTS client) |<-----------------+ | | 1972 | +---------------+ | | | example.net domain 1973 | V V | 1974 | +-------------+ | +---------------+ 1975 | +--------------+ | | | | | 1976 | | Guest +<-----x----->+ +<---------------->+ DOTS | 1977 | | (DOTS client)| | DOTS | | | Server | 1978 | +--------------+ | Gateway | | | | 1979 | +----+--------+ | +---------------+ 1980 | ^ | 1981 | | | 1982 | +----------------+ | | 1983 | | DDOS detector | | | 1984 | | (DOTS client) +<--------------+ | 1985 | +----------------+ | 1986 | | 1987 +-------------------------------------------------+ 1989 Figure 23: Example of Authentication and Authorization of DOTS Agents 1991 In the example depicted in Figure 23, the DOTS gateway and DOTS 1992 clients within the 'example.com' domain mutually authenticate with 1993 each other. After the DOTS gateway validates the identity of a DOTS 1994 client, it communicates with the AAA server in the 'example.com' 1995 domain to determine if the DOTS client is authorized to request DDOS 1996 mitigation. If the DOTS client is not authorized, a 4.01 1997 (Unauthorized) is returned in the response to the DOTS client. In 1998 this example, the DOTS gateway only allows the application server and 1999 DDOS detector to request DDOS mitigation, but does not permit the 2000 user of type 'guest' to request DDOS mitigation. 2002 Also, DOTS gateway and DOTS server located in different domains MUST 2003 perform mutual authentication (e.g., using certificates). A DOTS 2004 server will only allow a DOTS gateway with a certificate for a 2005 particular domain to request mitigation for that domain. In 2006 reference to Figure 23, the DOTS server only allows the DOTS gateway 2007 to request mitigation for 'example.com' domain and not for other 2008 domains. 2010 10. IANA Considerations 2012 This specification registers new CoAP response code, new parameters 2013 for DOTS signal channel and establishes registries for mappings to 2014 CBOR. 2016 10.1. CoAP Response Code 2018 The following entry is added to the "CoAP Response Codes" sub- 2019 registry: 2021 +------+------------------------------+-----------+ 2022 | Code | Description | Reference | 2023 +------+------------------------------+-----------+ 2024 | 3.00 | Alternate server | [RFCXXXX] | 2025 +------+------------------------------+-----------+ 2027 Figure 24: CoAP Response Code 2029 [Note to RFC Editor: Please replace XXXX with the RFC number of this 2030 specification.] 2032 10.2. DOTS signal channel CBOR Mappings Registry 2034 A new registry will be requested from IANA, entitled "DOTS signal 2035 channel CBOR Mappings Registry". The registry is to be created as 2036 Expert Review Required. 2038 10.2.1. Registration Template 2040 Parameter name: 2041 Parameter names (e.g., "target_ip") in the DOTS signal channel. 2043 CBOR Key Value: 2044 Key value for the parameter. The key value MUST be an integer in 2045 the range of 1 to 65536. The key values in the range of 32768 to 2046 65536 are assigned for Vendor-Specific parameters. 2048 CBOR Major Type: 2049 CBOR Major type and optional tag for the claim. 2051 Change Controller: 2052 For Standards Track RFCs, list the "IESG". For others, give the 2053 name of the responsible party. Other details (e.g., postal 2054 address, email address, home page URI) may also be included. 2056 Specification Document(s): 2058 Reference to the document or documents that specify the parameter, 2059 preferably including URIs that can be used to retrieve copies of 2060 the documents. An indication of the relevant sections may also be 2061 included but is not required. 2063 10.2.2. Initial Registry Contents 2065 o Parameter Name: "mitigation-scope" 2066 o CBOR Key Value: 1 2067 o CBOR Major Type: 5 2068 o Change Controller: IESG 2069 o Specification Document(s): this document 2071 o Parameter Name: "scope" 2072 o CBOR Key Value: 2 2073 o CBOR Major Type: 5 2074 o Change Controller: IESG 2075 o Specification Document(s): this document 2077 o Parameter Name: "mitigation-id" 2078 o CBOR Key Value: 3 2079 o CBOR Major Type: 0 2080 o Change Controller: IESG 2081 o Specification Document(s): this document 2083 o Parameter Name:target-ip 2084 o CBOR Key Value: 4 2085 o CBOR Major Type: 4 2086 o Change Controller: IESG 2087 o Specification Document(s): this document 2089 o Parameter Name: target-port-range 2090 o CBOR Key Value: 5 2091 o CBOR Major Type: 4 2092 o Change Controller: IESG 2093 o Specification Document(s): this document 2095 o Parameter Name: "lower-port" 2096 o CBOR Key Value: 6 2097 o CBOR Major Type: 0 2098 o Change Controller: IESG 2099 o Specification Document(s): this document 2101 o Parameter Name: "upper-port" 2102 o CBOR Key Value: 7 2103 o CBOR Major Type: 0 2104 o Change Controller: IESG 2105 o Specification Document(s): this document 2106 o Parameter Name: target-protocol 2107 o CBOR Key Value: 8 2108 o CBOR Major Type: 4 2109 o Change Controller: IESG 2110 o Specification Document(s): this document 2112 o Parameter Name: "fqdn" 2113 o CBOR Key Value: 9 2114 o CBOR Major Type: 4 2115 o Change Controller: IESG 2116 o Specification Document(s): this document 2118 o Parameter Name: "uri" 2119 o CBOR Key Value: 10 2120 o CBOR Major Type: 4 2121 o Change Controller: IESG 2122 o Specification Document(s): this document 2124 o Parameter Name: alias-name 2125 o CBOR Key Value: 11 2126 o CBOR Major Type: 4 2127 o Change Controller: IESG 2128 o Specification Document(s): this document 2130 o Parameter Name: "lifetime" 2131 o CBOR Key Value: 12 2132 o CBOR Major Type: 0 2133 o Change Controller: IESG 2134 o Specification Document(s): this document 2136 o Parameter Name: attack-status 2137 o CBOR Key Value: 13 2138 o CBOR Major Type: 0 2139 o Change Controller: IESG 2140 o Specification Document(s): this document 2142 o Parameter Name: signal-config 2143 o CBOR Key Value: 14 2144 o CBOR Major Type: 5 2145 o Change Controller: IESG 2146 o Specification Document(s): this document 2148 o Parameter Name: heartbeat-interval 2149 o CBOR Key Value: 15 2150 o CBOR Major Type: 0 2151 o Change Controller: IESG 2152 o Specification Document(s): this document 2153 o Parameter Name: max-retransmit 2154 o CBOR Key Value: 16 2155 o CBOR Major Type: 0 2156 o Change Controller: IESG 2157 o Specification Document(s): this document 2159 o Parameter Name: ack-timeout 2160 o CBOR Key Value: 17 2161 o CBOR Major Type: 0 2162 o Change Controller: IESG 2163 o Specification Document(s): this document 2165 o Parameter Name: ack-random-factor 2166 o CBOR Key Value: 18 2167 o CBOR Major Type: 7 2168 o Change Controller: IESG 2169 o Specification Document(s): this document 2171 o Parameter Name: MinValue 2172 o CBOR Key Value: 19 2173 o CBOR Major Type: 0 2174 o Change Controller: IESG 2175 o Specification Document(s): this document 2177 o Parameter Name: MaxValue 2178 o CBOR Key Value: 20 2179 o CBOR Major Type: 0 2180 o Change Controller: IESG 2181 o Specification Document(s): this document 2183 o Parameter Name: status 2184 o CBOR Key Value: 21 2185 o CBOR Major Type: 0 2186 o Change Controller: IESG 2187 o Specification Document(s): this document 2189 o Parameter Name: bytes-dropped 2190 o CBOR Key Value: 22 2191 o CBOR Major Type: 0 2192 o Change Controller: IESG 2193 o Specification Document(s): this document 2195 o Parameter Name: bps-dropped 2196 o CBOR Key Value: 23 2197 o CBOR Major Type: 0 2198 o Change Controller: IESG 2199 o Specification Document(s): this document 2200 o Parameter Name: pkts-dropped 2201 o CBOR Key Value: 24 2202 o CBOR Major Type: 0 2203 o Change Controller: IESG 2204 o Specification Document(s): this document 2206 o Parameter Name: pps-dropped 2207 o CBOR Key Value: 25 2208 o CBOR Major Type: 0 2209 o Change Controller: IESG 2210 o Specification Document(s): this document 2212 o Parameter Name: session-id 2213 o CBOR Key Value: 26 2214 o CBOR Major Type: 0 2215 o Change Controller: IESG 2216 o Specification Document(s): this document 2218 o Parameter Name: trigger-mitigation 2219 o CBOR Key Value: 27 2220 o CBOR Major Type: 7 2221 o Change Controller: IESG 2222 o Specification Document(s): this document 2224 o Parameter Name: missing-hb-allowed 2225 o CBOR Key Value: 28 2226 o CBOR Major Type: 0 2227 o Change Controller: IESG 2228 o Specification Document(s): this document 2230 o Parameter Name: CurrentValue 2231 o CBOR Key Value: 29 2232 o CBOR Major Type: 0 2233 o Change Controller: IESG 2234 o Specification Document(s): this document 2236 o Parameter Name:mitigation-start 2237 o CBOR Key Value: 30 2238 o CBOR Major Type: 7 2239 o Change Controller: IESG 2240 o Specification Document(s): this document 2242 o Parameter Name:target-prefix 2243 o CBOR Key Value: 31 2244 o CBOR Major Type: 4 2245 o Change Controller: IESG 2246 o Specification Document(s): this document 2247 o Parameter Name:client-identifier 2248 o CBOR Key Value: 32 2249 o CBOR Major Type: 2 2250 o Change Controller: IESG 2251 o Specification Document(s): this document 2253 11. Implementation Status 2255 [Note to RFC Editor: Please remove this section and reference to 2256 [RFC7942] prior to publication.] 2258 This section records the status of known implementations of the 2259 protocol defined by this specification at the time of posting of this 2260 Internet-Draft, and is based on a proposal described in [RFC7942]. 2261 The description of implementations in this section is intended to 2262 assist the IETF in its decision processes in progressing drafts to 2263 RFCs. Please note that the listing of any individual implementation 2264 here does not imply endorsement by the IETF. Furthermore, no effort 2265 has been spent to verify the information presented here that was 2266 supplied by IETF contributors. This is not intended as, and must not 2267 be construed to be, a catalog of available implementations or their 2268 features. Readers are advised to note that other implementations may 2269 exist. 2271 According to [RFC7942], "this will allow reviewers and working groups 2272 to assign due consideration to documents that have the benefit of 2273 running code, which may serve as evidence of valuable experimentation 2274 and feedback that have made the implemented protocols more mature. 2275 It is up to the individual working groups to use this information as 2276 they see fit". 2278 11.1. nttdots 2280 Organization: NTT Communication is developing a DOTS client and 2281 DOTS server software based on DOTS signal channel specified in 2282 this draft. It will be open-sourced. 2283 Description: Early implementation of DOTS protocol. It is aimed to 2284 implement a full DOTS protocol spec in accordance with maturing of 2285 DOTS protocol itself. 2286 Implementation: https://github.com/nttdots/go-dots 2287 Level of maturity: It is a early implementation of DOTS protocol. 2288 Messaging between DOTS clients and DOTS servers has been tested. 2289 Level of maturity will increase in accordance with maturing of 2290 DOTS protocol itself. 2291 Coverage: Capability of DOTS client: sending DOTS messages to the 2292 DOTS server in CoAP over DTLS as dots-signal. Capability of DOTS 2293 server: receiving dots-signal, validating received dots-signal, 2294 starting mitigation by handing over the dots-signal to DDOS 2295 mitigator. 2296 Licensing: It will be open-sourced with BSD 3-clause license. 2297 Implementation experience: It is implemented in Go-lang. Core 2298 specification of signaling is mature to be implemented, however, 2299 finding good libraries(like DTLS, CoAP) is rather difficult. 2300 Contact: Kaname Nishizuka 2302 12. Security Considerations 2304 Authenticated encryption MUST be used for data confidentiality and 2305 message integrity. (D)TLS based on client certificate MUST be used 2306 for mutual authentication. The interaction between the DOTS agents 2307 requires Datagram Transport Layer Security (DTLS) and Transport Layer 2308 Security (TLS) with a cipher suite offering confidentiality 2309 protection and the guidance given in [RFC7525] MUST be followed to 2310 avoid attacks on (D)TLS. 2312 A single DOTS signal channel between DOTS agents can be used to 2313 exchange multiple DOTS signal messages. To reduce DOTS client and 2314 DOTS server workload, DOTS client SHOULD re-use the (D)TLS session. 2316 If TCP is used between DOTS agents, an attacker may be able to inject 2317 RST packets, bogus application segments, etc., regardless of whether 2318 TLS authentication is used. Because the application data is TLS 2319 protected, this will not result in the application receiving bogus 2320 data, but it will constitute a DoS on the connection. This attack 2321 can be countered by using TCP-AO [RFC5925]. If TCP-AO is used, then 2322 any bogus packets injected by an attacker will be rejected by the 2323 TCP-AO integrity check and therefore will never reach the TLS layer. 2325 In order to prevent leaking internal information outside a client- 2326 domain, DOTS gateways located in the client-domain SHOULD NOT reveal 2327 the identity of internal DOTS clients (client-identifier) unless 2328 explicitly configured to do so. 2330 Special care should be taken in order to ensure that the activation 2331 of the proposed mechanism won't have an impact on the stability of 2332 the network (including connectivity and services delivered over that 2333 network). 2335 Involved functional elements in the cooperation system must establish 2336 exchange instructions and notification over a secure and 2337 authenticated channel. Adequate filters can be enforced to avoid 2338 that nodes outside a trusted domain can inject request such as 2339 deleting filtering rules. Nevertheless, attacks can be initiated 2340 from within the trusted domain if an entity has been corrupted. 2341 Adequate means to monitor trusted nodes should also be enabled. 2343 13. Contributors 2345 The following individuals have contributed to this document: 2347 Mike Geller Cisco Systems, Inc. 3250 Florida 33309 USA Email: 2348 mgeller@cisco.com 2350 Robert Moskowitz HTT Consulting Oak Park, MI 42837 United States 2351 Email: rgm@htt-consult.com 2353 Dan Wing Email: dwing-ietf@fuggles.com 2355 14. Acknowledgements 2357 Thanks to Christian Jacquenet, Roland Dobbins, Roman D. Danyliw, 2358 Michael Richardson, Ehud Doron, Kaname Nishizuka, Dave Dolson, Liang 2359 Xia, Jon Shallow, and Gilbert Clark for the discussion and comments. 2361 15. References 2363 15.1. Normative References 2365 [I-D.ietf-core-coap-tcp-tls] 2366 Bormann, C., Lemay, S., Tschofenig, H., Hartke, K., 2367 Silverajan, B., and B. Raymor, "CoAP (Constrained 2368 Application Protocol) over TCP, TLS, and WebSockets", 2369 draft-ietf-core-coap-tcp-tls-09 (work in progress), May 2370 2017. 2372 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2373 Requirement Levels", BCP 14, RFC 2119, 2374 DOI 10.17487/RFC2119, March 1997, 2375 . 2377 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 2378 (TLS) Protocol Version 1.2", RFC 5246, 2379 DOI 10.17487/RFC5246, August 2008, 2380 . 2382 [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP 2383 Authentication Option", RFC 5925, DOI 10.17487/RFC5925, 2384 June 2010, . 2386 [RFC6234] Eastlake 3rd, D. and T. Hansen, "US Secure Hash Algorithms 2387 (SHA and SHA-based HMAC and HKDF)", RFC 6234, 2388 DOI 10.17487/RFC6234, May 2011, 2389 . 2391 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 2392 Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, 2393 January 2012, . 2395 [RFC7250] Wouters, P., Ed., Tschofenig, H., Ed., Gilmore, J., 2396 Weiler, S., and T. Kivinen, "Using Raw Public Keys in 2397 Transport Layer Security (TLS) and Datagram Transport 2398 Layer Security (DTLS)", RFC 7250, DOI 10.17487/RFC7250, 2399 June 2014, . 2401 [RFC7252] Shelby, Z., Hartke, K., and C. Bormann, "The Constrained 2402 Application Protocol (CoAP)", RFC 7252, 2403 DOI 10.17487/RFC7252, June 2014, 2404 . 2406 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 2407 "Recommendations for Secure Use of Transport Layer 2408 Security (TLS) and Datagram Transport Layer Security 2409 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 2410 2015, . 2412 [RFC7641] Hartke, K., "Observing Resources in the Constrained 2413 Application Protocol (CoAP)", RFC 7641, 2414 DOI 10.17487/RFC7641, September 2015, 2415 . 2417 15.2. Informative References 2419 [I-D.ietf-core-comi] 2420 Veillette, M., Stok, P., Pelov, A., and A. Bierman, "CoAP 2421 Management Interface", draft-ietf-core-comi-01 (work in 2422 progress), July 2017. 2424 [I-D.ietf-core-yang-cbor] 2425 Veillette, M., Pelov, A., Somaraju, A., Turner, R., and A. 2426 Minaburo, "CBOR Encoding of Data Modeled with YANG", 2427 draft-ietf-core-yang-cbor-05 (work in progress), August 2428 2017. 2430 [I-D.ietf-dots-architecture] 2431 Mortensen, A., Andreasen, F., Reddy, T., 2432 christopher_gray3@cable.comcast.com, c., Compton, R., and 2433 N. Teague, "Distributed-Denial-of-Service Open Threat 2434 Signaling (DOTS) Architecture", draft-ietf-dots- 2435 architecture-05 (work in progress), October 2017. 2437 [I-D.ietf-dots-data-channel] 2438 Reddy, T., Boucadair, M., Nishizuka, K., Xia, L., Patil, 2439 P., Mortensen, A., and N. Teague, "Distributed Denial-of- 2440 Service Open Threat Signaling (DOTS) Data Channel", draft- 2441 ietf-dots-data-channel-05 (work in progress), October 2442 2017. 2444 [I-D.ietf-dots-requirements] 2445 Mortensen, A., Moskowitz, R., and T. Reddy, "Distributed 2446 Denial of Service (DDoS) Open Threat Signaling 2447 Requirements", draft-ietf-dots-requirements-06 (work in 2448 progress), July 2017. 2450 [I-D.ietf-dots-use-cases] 2451 Dobbins, R., Migault, D., Fouant, S., Moskowitz, R., 2452 Teague, N., Xia, L., and K. Nishizuka, "Use cases for DDoS 2453 Open Threat Signaling", draft-ietf-dots-use-cases-08 (work 2454 in progress), October 2017. 2456 [I-D.ietf-tls-tls13] 2457 Rescorla, E., "The Transport Layer Security (TLS) Protocol 2458 Version 1.3", draft-ietf-tls-tls13-21 (work in progress), 2459 July 2017. 2461 [I-D.rescorla-tls-dtls13] 2462 Rescorla, E., Tschofenig, H., and N. Modadugu, "The 2463 Datagram Transport Layer Security (DTLS) Protocol Version 2464 1.3", draft-rescorla-tls-dtls13-01 (work in progress), 2465 March 2017. 2467 [proto_numbers] 2468 "IANA, "Protocol Numbers"", 2011, 2469 . 2471 [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, 2472 DOI 10.17487/RFC0791, September 1981, 2473 . 2475 [RFC4340] Kohler, E., Handley, M., and S. Floyd, "Datagram 2476 Congestion Control Protocol (DCCP)", RFC 4340, 2477 DOI 10.17487/RFC4340, March 2006, 2478 . 2480 [RFC4632] Fuller, V. and T. Li, "Classless Inter-domain Routing 2481 (CIDR): The Internet Address Assignment and Aggregation 2482 Plan", BCP 122, RFC 4632, DOI 10.17487/RFC4632, August 2483 2006, . 2485 [RFC4732] Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet 2486 Denial-of-Service Considerations", RFC 4732, 2487 DOI 10.17487/RFC4732, December 2006, 2488 . 2490 [RFC4787] Audet, F., Ed. and C. Jennings, "Network Address 2491 Translation (NAT) Behavioral Requirements for Unicast 2492 UDP", BCP 127, RFC 4787, DOI 10.17487/RFC4787, January 2493 2007, . 2495 [RFC4960] Stewart, R., Ed., "Stream Control Transmission Protocol", 2496 RFC 4960, DOI 10.17487/RFC4960, September 2007, 2497 . 2499 [RFC4987] Eddy, W., "TCP SYN Flooding Attacks and Common 2500 Mitigations", RFC 4987, DOI 10.17487/RFC4987, August 2007, 2501 . 2503 [RFC5077] Salowey, J., Zhou, H., Eronen, P., and H. Tschofenig, 2504 "Transport Layer Security (TLS) Session Resumption without 2505 Server-Side State", RFC 5077, DOI 10.17487/RFC5077, 2506 January 2008, . 2508 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 2509 the Network Configuration Protocol (NETCONF)", RFC 6020, 2510 DOI 10.17487/RFC6020, October 2010, 2511 . 2513 [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with 2514 Dual-Stack Hosts", RFC 6555, DOI 10.17487/RFC6555, April 2515 2012, . 2517 [RFC6724] Thaler, D., Ed., Draves, R., Matsumoto, A., and T. Chown, 2518 "Default Address Selection for Internet Protocol Version 6 2519 (IPv6)", RFC 6724, DOI 10.17487/RFC6724, September 2012, 2520 . 2522 [RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed., 2523 "Enrollment over Secure Transport", RFC 7030, 2524 DOI 10.17487/RFC7030, October 2013, 2525 . 2527 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 2528 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 2529 October 2013, . 2531 [RFC7413] Cheng, Y., Chu, J., Radhakrishnan, S., and A. Jain, "TCP 2532 Fast Open", RFC 7413, DOI 10.17487/RFC7413, December 2014, 2533 . 2535 [RFC7589] Badra, M., Luchuk, A., and J. Schoenwaelder, "Using the 2536 NETCONF Protocol over Transport Layer Security (TLS) with 2537 Mutual X.509 Authentication", RFC 7589, 2538 DOI 10.17487/RFC7589, June 2015, 2539 . 2541 [RFC7918] Langley, A., Modadugu, N., and B. Moeller, "Transport 2542 Layer Security (TLS) False Start", RFC 7918, 2543 DOI 10.17487/RFC7918, August 2016, 2544 . 2546 [RFC7924] Santesson, S. and H. Tschofenig, "Transport Layer Security 2547 (TLS) Cached Information Extension", RFC 7924, 2548 DOI 10.17487/RFC7924, July 2016, 2549 . 2551 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 2552 Code: The Implementation Status Section", BCP 205, 2553 RFC 7942, DOI 10.17487/RFC7942, July 2016, 2554 . 2556 [RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage 2557 Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, 2558 March 2017, . 2560 Authors' Addresses 2562 Tirumaleswar Reddy 2563 McAfee, Inc. 2564 Embassy Golf Link Business Park 2565 Bangalore, Karnataka 560071 2566 India 2568 Email: kondtir@gmail.com 2570 Mohamed Boucadair 2571 Orange 2572 Rennes 35000 2573 France 2575 Email: mohamed.boucadair@orange.com 2576 Prashanth Patil 2577 Cisco Systems, Inc. 2579 Email: praspati@cisco.com 2581 Andrew Mortensen 2582 Arbor Networks, Inc. 2583 2727 S. State St 2584 Ann Arbor, MI 48104 2585 United States 2587 Email: amortensen@arbor.net 2589 Nik Teague 2590 Verisign, Inc. 2591 United States 2593 Email: nteague@verisign.com