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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group C. Bormann 3 Internet-Draft Universitaet Bremen TZI 4 Intended status: Standards Track B. Carpenter, Ed. 5 Expires: December 8, 2017 Univ. of Auckland 6 B. Liu, Ed. 7 Huawei Technologies Co., Ltd 8 June 6, 2017 10 A Generic Autonomic Signaling Protocol (GRASP) 11 draft-ietf-anima-grasp-13 13 Abstract 15 This document specifies the GeneRic Autonomic Signaling Protocol 16 (GRASP), which enables autonomic nodes and autonomic service agents 17 to dynamically discover peers, to synchronize state with each other, 18 and to negotiate parameter settings with each other. GRASP depends 19 on an external security environment that is described elsewhere. The 20 technical objectives and parameters for specific application 21 scenarios are to be described in separate documents. Appendices 22 briefly discuss requirements for the protocol and existing protocols 23 with comparable features. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at http://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on December 8, 2017. 42 Copyright Notice 44 Copyright (c) 2017 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents 49 (http://trustee.ietf.org/license-info) in effect on the date of 50 publication of this document. Please review these documents 51 carefully, as they describe your rights and restrictions with respect 52 to this document. Code Components extracted from this document must 53 include Simplified BSD License text as described in Section 4.e of 54 the Trust Legal Provisions and are provided without warranty as 55 described in the Simplified BSD License. 57 Table of Contents 59 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 60 2. GRASP Protocol Overview . . . . . . . . . . . . . . . . . . . 5 61 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 62 2.2. High Level Deployment Model . . . . . . . . . . . . . . . 7 63 2.3. High Level Design . . . . . . . . . . . . . . . . . . . . 8 64 2.4. Quick Operating Overview . . . . . . . . . . . . . . . . 11 65 2.5. GRASP Protocol Basic Properties and Mechanisms . . . . . 12 66 2.5.1. Required External Security Mechanism . . . . . . . . 12 67 2.5.2. Constrained Instances . . . . . . . . . . . . . . . . 12 68 2.5.3. Transport Layer Usage . . . . . . . . . . . . . . . . 14 69 2.5.4. Discovery Mechanism and Procedures . . . . . . . . . 14 70 2.5.5. Negotiation Procedures . . . . . . . . . . . . . . . 18 71 2.5.6. Synchronization and Flooding Procedures . . . . . . . 20 72 2.6. GRASP Constants . . . . . . . . . . . . . . . . . . . . . 22 73 2.7. Session Identifier (Session ID) . . . . . . . . . . . . . 23 74 2.8. GRASP Messages . . . . . . . . . . . . . . . . . . . . . 23 75 2.8.1. Message Overview . . . . . . . . . . . . . . . . . . 23 76 2.8.2. GRASP Message Format . . . . . . . . . . . . . . . . 24 77 2.8.3. Message Size . . . . . . . . . . . . . . . . . . . . 25 78 2.8.4. Discovery Message . . . . . . . . . . . . . . . . . . 25 79 2.8.5. Discovery Response Message . . . . . . . . . . . . . 26 80 2.8.6. Request Messages . . . . . . . . . . . . . . . . . . 27 81 2.8.7. Negotiation Message . . . . . . . . . . . . . . . . . 28 82 2.8.8. Negotiation End Message . . . . . . . . . . . . . . . 29 83 2.8.9. Confirm Waiting Message . . . . . . . . . . . . . 29 84 2.8.10. Synchronization Message . . . . . . . . . . . . . . . 29 85 2.8.11. Flood Synchronization Message . . . . . . . . . . . . 30 86 2.8.12. Invalid Message . . . . . . . . . . . . . . . . . . . 31 87 2.8.13. No Operation Message . . . . . . . . . . . . . . . . 31 88 2.9. GRASP Options . . . . . . . . . . . . . . . . . . . . . . 31 89 2.9.1. Format of GRASP Options . . . . . . . . . . . . . . . 31 90 2.9.2. Divert Option . . . . . . . . . . . . . . . . . . . . 32 91 2.9.3. Accept Option . . . . . . . . . . . . . . . . . . . . 32 92 2.9.4. Decline Option . . . . . . . . . . . . . . . . . . . 32 93 2.9.5. Locator Options . . . . . . . . . . . . . . . . . . . 33 94 2.10. Objective Options . . . . . . . . . . . . . . . . . . . . 35 95 2.10.1. Format of Objective Options . . . . . . . . . . . . 35 96 2.10.2. Objective flags . . . . . . . . . . . . . . . . . . 36 97 2.10.3. General Considerations for Objective Options . . . . 36 98 2.10.4. Organizing of Objective Options . . . . . . . . . . 37 99 2.10.5. Experimental and Example Objective Options . . . . . 39 100 3. Implementation Status [RFC Editor: please remove] . . . . . . 39 101 3.1. BUPT C++ Implementation . . . . . . . . . . . . . . . . . 39 102 3.2. Python Implementation . . . . . . . . . . . . . . . . . . 40 103 4. Security Considerations . . . . . . . . . . . . . . . . . . . 41 104 5. CDDL Specification of GRASP . . . . . . . . . . . . . . . . . 43 105 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 45 106 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 47 107 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 47 108 8.1. Normative References . . . . . . . . . . . . . . . . . . 47 109 8.2. Informative References . . . . . . . . . . . . . . . . . 48 110 Appendix A. Open Issues [RFC Editor: This section should be 111 empty. Please remove] . . . . . . . . . . . . . . . 52 112 Appendix B. Closed Issues [RFC Editor: Please remove] . . . . . 52 113 Appendix C. Change log [RFC Editor: Please remove] . . . . . . . 61 114 Appendix D. Example Message Formats . . . . . . . . . . . . . . 68 115 D.1. Discovery Example . . . . . . . . . . . . . . . . . . . . 68 116 D.2. Flood Example . . . . . . . . . . . . . . . . . . . . . . 69 117 D.3. Synchronization Example . . . . . . . . . . . . . . . . . 69 118 D.4. Simple Negotiation Example . . . . . . . . . . . . . . . 69 119 D.5. Complete Negotiation Example . . . . . . . . . . . . . . 70 120 Appendix E. Requirement Analysis of Discovery, Synchronization 121 and Negotiation . . . . . . . . . . . . . . . . . . 71 122 E.1. Requirements for Discovery . . . . . . . . . . . . . . . 71 123 E.2. Requirements for Synchronization and Negotiation 124 Capability . . . . . . . . . . . . . . . . . . . . . . . 73 125 E.3. Specific Technical Requirements . . . . . . . . . . . . . 75 126 Appendix F. Capability Analysis of Current Protocols . . . . . . 76 127 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 78 129 1. Introduction 131 The success of the Internet has made IP-based networks bigger and 132 more complicated. Large-scale ISP and enterprise networks have 133 become more and more problematic for human based management. Also, 134 operational costs are growing quickly. Consequently, there are 135 increased requirements for autonomic behavior in the networks. 136 General aspects of autonomic networks are discussed in [RFC7575] and 137 [RFC7576]. 139 One approach is to largely decentralize the logic of network 140 management by migrating it into network elements. A reference model 141 for autonomic networking on this basis is given in 142 [I-D.ietf-anima-reference-model]. The reader should consult this 143 document to understand how various autonomic components fit together. 144 In order to fulfill autonomy, devices that embody Autonomic Service 145 Agents (ASAs, [RFC7575]) have specific signaling requirements. In 146 particular they need to discover each other, to synchronize state 147 with each other, and to negotiate parameters and resources directly 148 with each other. There is no limitation on the types of parameters 149 and resources concerned, which can include very basic information 150 needed for addressing and routing, as well as anything else that 151 might be configured in a conventional non-autonomic network. The 152 atomic unit of discovery, synchronization or negotiation is referred 153 to as a technical objective, i.e, a configurable parameter or set of 154 parameters (defined more precisely in Section 2.1). 156 Negotiation is an iterative process, requiring multiple message 157 exchanges forming a closed loop between the negotiating entities. In 158 fact, these entities are ASAs, normally but not necessarily in 159 different network devices. State synchronization, when needed, can 160 be regarded as a special case of negotiation, without iteration. 161 Both negotiation and synchronization must logically follow discovery. 162 More details of the requirements are found in Appendix E. 163 Section 2.3 describes a behavior model for a protocol intended to 164 support discovery, synchronization and negotiation. The design of 165 GeneRic Autonomic Signaling Protocol (GRASP) in Section 2 of this 166 document is based on this behavior model. The relevant capabilities 167 of various existing protocols are reviewed in Appendix F. 169 The proposed discovery mechanism is oriented towards synchronization 170 and negotiation objectives. It is based on a neighbor discovery 171 process on the local link, but also supports diversion to peers on 172 other links. There is no assumption of any particular form of 173 network topology. When a device starts up with no pre-configuration, 174 it has no knowledge of the topology. The protocol itself is capable 175 of being used in a small and/or flat network structure such as a 176 small office or home network as well as in a large professionally 177 managed network. Therefore, the discovery mechanism needs to be able 178 to allow a device to bootstrap itself without making any prior 179 assumptions about network structure. 181 Because GRASP can be used as part of a decision process among 182 distributed devices or between networks, it must run in a secure and 183 strongly authenticated environment. 185 In realistic deployments, not all devices will support GRASP. 186 Therefore, some autonomic service agents will directly manage a group 187 of non-autonomic nodes, and other non-autonomic nodes will be managed 188 traditionally. Such mixed scenarios are not discussed in this 189 specification. 191 2. GRASP Protocol Overview 193 2.1. Terminology 195 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 196 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 197 "OPTIONAL" in this document are to be interpreted as described in 198 [RFC2119] when they appear in ALL CAPS. When these words are not in 199 ALL CAPS (such as "should" or "Should"), they have their usual 200 English meanings, and are not to be interpreted as [RFC2119] key 201 words. 203 This document uses terminology defined in [RFC7575]. 205 The following additional terms are used throughout this document: 207 o Discovery: a process by which an ASA discovers peers according to 208 a specific discovery objective. The discovery results may be 209 different according to the different discovery objectives. The 210 discovered peers may later be used as negotiation counterparts or 211 as sources of synchronization data. 213 o Negotiation: a process by which two ASAs interact iteratively to 214 agree on parameter settings that best satisfy the objectives of 215 both ASAs. 217 o State Synchronization: a process by which ASAs interact to receive 218 the current state of parameter values stored in other ASAs. This 219 is a special case of negotiation in which information is sent but 220 the ASAs do not request their peers to change parameter settings. 221 All other definitions apply to both negotiation and 222 synchronization. 224 o Technical Objective (usually abbreviated as Objective): A 225 technical objective is a data structure, whose main contents are a 226 name and a value. The value consists of a single configurable 227 parameter or a set of parameters of some kind. The exact format 228 of an objective is defined in Section 2.10.1. An objective occurs 229 in three contexts: Discovery, Negotiation and Synchronization. 230 Normally, a given objective will not occur in negotiation and 231 synchronization contexts simultaneously. 233 * One ASA may support multiple independent objectives. 235 * The parameter(s) in the value of a given objective apply to a 236 specific service or function or action. They may in principle 237 be anything that can be set to a specific logical, numerical or 238 string value, or a more complex data structure, by a network 239 node. Each node is expected to contain one or more ASAs which 240 may each manage subsidiary non-autonomic nodes. 242 * Discovery Objective: an objective in the process of discovery. 243 Its value may be undefined. 245 * Synchronization Objective: an objective whose specific 246 technical content needs to be synchronized among two or more 247 ASAs. Thus, each ASA will maintain its own copy of the 248 objective. 250 * Negotiation Objective: an objective whose specific technical 251 content needs to be decided in coordination with another ASA. 252 Again, each ASA will maintain its own copy of the objective. 254 A detailed discussion of objectives, including their format, is 255 found in Section 2.10. 257 o Discovery Initiator: an ASA that starts discovery by sending a 258 discovery message referring to a specific discovery objective. 260 o Discovery Responder: a peer that either contains an ASA supporting 261 the discovery objective indicated by the discovery initiator, or 262 caches the locator(s) of the ASA(s) supporting the objective. It 263 sends a Discovery Response, as described later. 265 o Synchronization Initiator: an ASA that starts synchronization by 266 sending a request message referring to a specific synchronization 267 objective. 269 o Synchronization Responder: a peer ASA which responds with the 270 value of a synchronization objective. 272 o Negotiation Initiator: an ASA that starts negotiation by sending a 273 request message referring to a specific negotiation objective. 275 o Negotiation Counterpart: a peer with which the Negotiation 276 Initiator negotiates a specific negotiation objective. 278 o GRASP Instance: This refers to an instantiation of a GRASP 279 protocol engine, likely including multiple threads or processes as 280 well as dynamic data structures such as a discovery cache, running 281 in a given security environment on a single device. 283 o GRASP Core: This refers to the code and shared data structures of 284 a GRASP instance, which will communicate with individual ASAs via 285 a suitable Application Programming Interface (API). 287 o Interface or GRASP Interface: Unless otherwise stated, these refer 288 to a network interface - which might be physical or virtual - that 289 a specific instance of GRASP is currently using. A device might 290 have other interfaces that are not used by GRASP and which are 291 outside the scope of the autonomic network. 293 2.2. High Level Deployment Model 295 A GRASP implementation will be part of the Autonomic Networking 296 Infrastructure in an autonomic node, which must also provide an 297 appropriate security environment. In accordance with 298 [I-D.ietf-anima-reference-model], this SHOULD be the Autonomic 299 Control Plane (ACP) [I-D.ietf-anima-autonomic-control-plane]. As a 300 result, all autonomic nodes in the ACP are able to trust each other. 301 It is expected that GRASP will access the ACP by using a typical 302 socket programming interface and the ACP will make available only 303 network interfaces within the autonomic network. If there is no ACP, 304 the considerations described in Section 2.5.1 apply. 306 There will also be one or more Autonomic Service Agents (ASAs). In 307 the minimal case of a single-purpose device, these components might 308 be fully integrated with GRASP and the ACP. A more common model is 309 expected to be a multi-purpose device capable of containing several 310 ASAs, such as a router or large switch. In this case it is expected 311 that the ACP, GRASP and the ASAs will be implemented as separate 312 processes, which are able to support asynchronous and simultaneous 313 operations, for example by multi-threading. 315 In some scenarios, a limited negotiation model might be deployed 316 based on a limited trust relationship such as that between two 317 administrative domains. ASAs might then exchange limited information 318 and negotiate some particular configurations. 320 GRASP is explicitly designed to operate within a single addressing 321 realm. Its discovery and flooding mechanisms do not support 322 autonomic operations that cross any form of address translator or 323 upper layer proxy. 325 A suitable Application Programming Interface (API) will be needed 326 between GRASP and the ASAs. In some implementations, ASAs would run 327 in user space with a GRASP library providing the API, and this 328 library would in turn communicate via system calls with core GRASP 329 functions. Details of the API are out of scope for the present 330 document. For further details of possible deployment models, see 331 [I-D.ietf-anima-reference-model]. 333 An instance of GRASP must be aware of the network interfaces it will 334 use, and of the appropriate global-scope and link-local addresses. 336 In the presence of the ACP, such information will be available from 337 the adjacency table discussed in [I-D.ietf-anima-reference-model]. 338 In other cases, GRASP must determine such information for itself. 339 Details depend on the device and operating system. In the rest of 340 this document, the terms 'interfaces' or 'GRASP interfaces' refers 341 only to the set of network interfaces that a specific instance of 342 GRASP is currently using. 344 Because GRASP needs to work with very high reliability, especially 345 during bootstrapping and during fault conditions, it is essential 346 that every implementation continues to operate in adverse conditions. 347 For example, discovery failures, or any kind of socket exception at 348 any time, must not cause irrecoverable failures in GRASP itself, and 349 must return suitable error codes through the API so that ASAs can 350 also recover. 352 GRASP must not depend upon non-volatile data storage. All run time 353 error conditions, and events such as address renumbering, network 354 interface failures, and CPU sleep/wake cycles, must be handled in 355 such a way that GRASP will still operate correctly and securely 356 (Section 2.5.1) afterwards. 358 An autonomic node will normally run a single instance of GRASP, used 359 by multiple ASAs. Possible exceptions are mentioned below. 361 2.3. High Level Design 363 This section describes the behavior model and general design of 364 GRASP, supporting discovery, synchronization and negotiation, to act 365 as a platform for different technical objectives. 367 o A generic platform: 369 The protocol design is generic and independent of the 370 synchronization or negotiation contents. The technical contents 371 will vary according to the various technical objectives and the 372 different pairs of counterparts. 374 o Normally, a single main instance of the GRASP protocol engine will 375 exist in an autonomic node, and each ASA will run as an 376 independent asynchronous process. However, scenarios where 377 multiple instances of GRASP run in a single node, perhaps with 378 different security properties, are possible (Section 2.5.2). In 379 this case, each instance MUST listen independently for GRASP link- 380 local multicasts, and all instances MUST be woken by each such 381 multicast, in order for discovery and flooding to work correctly. 383 o Security infrastructure: 385 As noted above, the protocol itself has no built-in security 386 functionality, and relies on a separate secure infrastructure. 388 o Discovery, synchronization and negotiation are designed together: 390 The discovery method and the synchronization and negotiation 391 methods are designed in the same way and can be combined when this 392 is useful, allowing a rapid mode of operation described in 393 Section 2.5.4. These processes can also be performed 394 independently when appropriate. 396 * Thus, for some objectives, especially those concerned with 397 application layer services, another discovery mechanism such as 398 the future DNS Service Discovery [RFC7558] MAY be used. The 399 choice is left to the designers of individual ASAs. 401 o A uniform pattern for technical objectives: 403 The synchronization and negotiation objectives are defined 404 according to a uniform pattern. The values that they contain 405 could be carried either in a simple binary format or in a complex 406 object format. The basic protocol design uses the Concise Binary 407 Object Representation (CBOR) [RFC7049], which is readily 408 extensible for unknown future requirements. 410 o A flexible model for synchronization: 412 GRASP supports synchronization between two nodes, which could be 413 used repeatedly to perform synchronization among a small number of 414 nodes. It also supports an unsolicited flooding mode when large 415 groups of nodes, possibly including all autonomic nodes, need data 416 for the same technical objective. 418 * There may be some network parameters for which a more 419 traditional flooding mechanism such as DNCP [RFC7787] is 420 considered more appropriate. GRASP can coexist with DNCP. 422 o A simple initiator/responder model for negotiation: 424 Multi-party negotiations are very complicated to model and cannot 425 readily be guaranteed to converge. GRASP uses a simple bilateral 426 model and can support multi-party negotiations by indirect steps. 428 o Organizing of synchronization or negotiation content: 430 The technical content transmitted by GRASP will be organized 431 according to the relevant function or service. The objectives for 432 different functions or services are kept separate, because they 433 may be negotiated or synchronized with different counterparts or 434 have different response times. Thus a normal arrangement would be 435 a single ASA managing a small set of closely related objectives, 436 with a version of that ASA in each relevant autonomic node. 437 Further discussion of this aspect is out of scope for the current 438 document. 440 o Requests and responses in negotiation procedures: 442 The initiator can negotiate a specific negotiation objective with 443 relevant counterpart ASAs. It can request relevant information 444 from a counterpart so that it can coordinate its local 445 configuration. It can request the counterpart to make a matching 446 configuration. It can request simulation or forecast results by 447 sending some dry run conditions. 449 Beyond the traditional yes/no answer, the responder can reply with 450 a suggested alternative value for the objective concerned. This 451 would start a bi-directional negotiation ending in a compromise 452 between the two ASAs. 454 o Convergence of negotiation procedures: 456 To enable convergence, when a responder suggests a new value or 457 condition in a negotiation step reply, it should be as close as 458 possible to the original request or previous suggestion. The 459 suggested value of later negotiation steps should be chosen 460 between the suggested values from the previous two steps. GRASP 461 provides mechanisms to guarantee convergence (or failure) in a 462 small number of steps, namely a timeout and a maximum number of 463 iterations. 465 o Extensibility: 467 GRASP intentionally does not have a version number, and can be 468 extended by adding new message types and options. The Invalid 469 Message (M_INVALID) will be used to signal that an implementation 470 does not recognize a message or option sent by another 471 implementation. In normal use, new semantics will be added by 472 defining new synchronization or negotiation objectives. 474 2.4. Quick Operating Overview 476 An instance of GRASP is expected to run as a separate core module, 477 providing an API (such as [I-D.liu-anima-grasp-api]) to interface to 478 various ASAs. These ASAs may operate without special privilege, 479 unless they need it for other reasons (such as configuring IP 480 addresses or manipulating routing tables). 482 The GRASP mechanisms used by the ASA are built around GRASP 483 objectives defined as data structures containing administrative 484 information such as the objective's unique name, and its current 485 value. The format and size of the value is not restricted by the 486 protocol, except that it must be possible to serialize it for 487 transmission in CBOR, which is no restriction at all in practice. 489 GRASP provides the following mechanisms: 491 o A discovery mechanism (M_DISCOVERY, M_RESPONSE), by which an ASA 492 can discover other ASAs supporting a given objective. 494 o A negotiation request mechanism (M_REQ_NEG), by which an ASA can 495 start negotiation of an objective with a counterpart ASA. Once a 496 negotiation has started, the process is symmetrical, and there is 497 a negotiation step message (M_NEGOTIATE) for each ASA to use in 498 turn. Two other functions support negotiating steps (M_WAIT, 499 M_END). 501 o A synchronization mechanism (M_REQ_SYN), by which an ASA can 502 request the current value of an objective from a counterpart ASA. 503 With this, there is a corresponding response function (M_SYNCH) 504 for an ASA that wishes to respond to synchronization requests. 506 o A flood mechanism (M_FLOOD), by which an ASA can cause the current 507 value of an objective to be flooded throughout the autonomic 508 network so that any ASA can receive it. One application of this 509 is to act as an announcement, avoiding the need for discovery of a 510 widely applicable objective. 512 Some example messages and simple message flows are provided in 513 Appendix D. 515 2.5. GRASP Protocol Basic Properties and Mechanisms 517 2.5.1. Required External Security Mechanism 519 The protocol SHOULD always run within a secure Autonomic Control 520 Plane (ACP) [I-D.ietf-anima-autonomic-control-plane]. The ACP is 521 assumed to carry all messages securely, including link-local 522 multicast when it is virtualized over the ACP. A GRASP instance MUST 523 verify whether the ACP is operational. 525 If there is no ACP, one of the alternatives in Section 2.5.2 applies. 527 Network interfaces could be at different security levels, in 528 particular being part of the ACP or not. All the interfaces 529 supported by a given GRASP instance MUST be at the same security 530 level. 532 The ACP, or in its absence another security mechanism, sets the 533 boundary within which nodes are trusted as GRASP peers. A GRASP 534 implementation MUST refuse to execute GRASP synchronization and 535 negotiation functions if there is neither an operational ACP nor 536 another secure environment. 538 Link-local multicast is used for discovery messages. Responses to 539 discovery messages MUST be secured, with one exception mentioned in 540 the next section. 542 2.5.2. Constrained Instances 544 This section describes some cases where additional instances of GRASP 545 are appropriate, subject to certain security constraints. 547 In these cases, since multicast packets are not secured, Rapid Mode 548 discovery (Section 2.5.4.5) MUST NOT be used. 550 2.5.2.1. No ACP 552 As mentioned in Section 2.3, some GRASP operations might be performed 553 across an administrative domain boundary by mutual agreement, without 554 the benefit of an ACP. Such operations MUST be confined to a 555 separate instance of GRASP with its own copy of all GRASP data 556 structures. Messages MUST be authenticated and encryption MUST be 557 used. Further details may be specified in future documents. 559 2.5.2.2. Discovery Unsolicited Link-Local 561 Some services may need to use insecure GRASP discovery, response and 562 flood messages without being able to use pre-existing security 563 associations. Such operations being intrinsically insecure, they 564 need to be confined to link-local use to minimize the risk of 565 malicious actions. Possible examples include discovery of candidate 566 ACP neighbors [I-D.ietf-anima-autonomic-control-plane], discovery of 567 bootstrap proxies [I-D.ietf-anima-bootstrapping-keyinfra] or perhaps 568 initialization services in networks using GRASP without being fully 569 autonomic (e.g., no ACP). Such usage MUST be limited to link-local 570 operations on a single interface and MUST be confined to a separate 571 insecure instance of GRASP with its own copy of all GRASP data 572 structures. This instance is nicknamed DULL - Discovery Unsolicited 573 Link-Local. 575 The detailed rules for the DULL instance of GRASP are as follows: 577 o An initiator MAY send Discovery or Flood Synchronization link- 578 local multicast messages which MUST have a loop count of 1, to 579 prevent off-link operations. Other GRASP message types MUST NOT 580 be sent. 582 o A responder MUST silently discard any message whose loop count is 583 not 1. 585 o A responder MUST silently discard any message referring to a GRASP 586 Objective that is not directly part of a service that requires 587 this insecure mode. 589 o A responder MUST NOT relay any multicast messages. 591 o A Discovery Response MUST indicate a link-local address. 593 o A Discovery Response MUST NOT include a Divert option. 595 o A node MUST silently discard any message whose source address is 596 not link-local. 598 To minimize traffic possibly observed by third parties, GRASP traffic 599 SHOULD be minimized by using only Flood Synchronization to announce 600 objectives and their associated locators, rather than by using 601 Discovery and Response. Further details are out of scope for this 602 document 604 2.5.3. Transport Layer Usage 606 All GRASP messages, after they are serialized as a CBOR byte string, 607 are transmitted as such directly over the transport protocol in use, 608 which itself runs within the security environment discussed in the 609 previous section. 611 GRASP discovery and flooding messages are designed for use over link- 612 local multicast UDP. They MUST NOT be fragmented, and therefore MUST 613 NOT exceed the link MTU size. An implementation should report any 614 attempt to send a longer message as a run-time error. 616 All other GRASP messages are unicast and could in principle run over 617 any transport protocol. An implementation MUST support use of TCP. 618 It MAY support use of another transport protocol but the details are 619 out of scope for this specification. However, GRASP itself does not 620 provide for error detection or retransmission. Use of an unreliable 621 transport protocol is therefore NOT RECOMMENDED. 623 For considerations when running without an ACP, see Section 2.5.2.1. 625 For link-local multicast, the GRASP protocol listens to the well- 626 known GRASP Listen Port (Section 2.6). For unicast transport 627 sessions used for discovery responses, synchronization and 628 negotiation, the ASA concerned normally listens on its own 629 dynamically assigned ports, which are communicated to its peers 630 during discovery. However, a minimal implementation MAY use the 631 GRASP Listen Port for this purpose. 633 2.5.4. Discovery Mechanism and Procedures 635 2.5.4.1. Separated discovery and negotiation mechanisms 637 Although discovery and negotiation or synchronization are defined 638 together in GRASP, they are separate mechanisms. The discovery 639 process could run independently from the negotiation or 640 synchronization process. Upon receiving a Discovery (Section 2.8.4) 641 message, the recipient node should return a response message in which 642 it either indicates itself as a discovery responder or diverts the 643 initiator towards another more suitable ASA. However, this response 644 may be delayed if the recipient needs to relay the discovery onwards, 645 as described below. 647 The discovery action (M_DISCOVERY) will normally be followed by a 648 negotiation (M_REQ_NEG) or synchronization (M_REQ_SYN) action. The 649 discovery results could be utilized by the negotiation protocol to 650 decide which ASA the initiator will negotiate with. 652 The initiator of a discovery action for a given objective need not be 653 capable of responding to that objective as a Negotiation Counterpart, 654 as a Synchronization Responder or as source for flooding. For 655 example, an ASA might perform discovery even if it only wishes to act 656 a Synchronization Initiator or Negotiation Initiator. Such an ASA 657 does not itself need to respond to discovery messages. 659 It is also entirely possible to use GRASP discovery without any 660 subsequent negotiation or synchronization action. In this case, the 661 discovered objective is simply used as a name during the discovery 662 process and any subsequent operations between the peers are outside 663 the scope of GRASP. 665 2.5.4.2. Discovery Overview 667 A complete discovery process will start with a multicast (of 668 M_DISCOVERY) on the local link. On-link neighbors supporting the 669 discovery objective will respond directly (with M_RESPONSE). A 670 neighbor with multiple interfaces may respond with a cached discovery 671 response. If it has no cached response, it will relay the discovery 672 on its other GRASP interfaces. If a node receiving the relayed 673 discovery supports the discovery objective, it will respond to the 674 relayed discovery. If it has a cached response, it will respond with 675 that. If not, it will repeat the discovery process, which thereby 676 becomes iterative. The loop count and timeout will ensure that the 677 process ends. Further details are given below. 679 A Discovery message MAY be sent unicast (via UDP or TCP) to a peer 680 node, which SHOULD then proceed exactly as if the message had been 681 multicast, except that when TCP is used, the response will be on the 682 same socket as the query. However, this mode does not guarantee 683 successful discovery in the general case. 685 2.5.4.3. Discovery Procedures 687 Discovery starts as an on-link operation. The Divert option can tell 688 the discovery initiator to contact an off-link ASA for that discovery 689 objective. A Discovery message is sent by a discovery initiator via 690 UDP to the ALL_GRASP_NEIGHBORS link-local multicast address 691 (Section 2.6). Every network device that supports GRASP always 692 listens to a well-known UDP port to capture the discovery messages. 693 Because this port is unique in a device, this is a function of the 694 GRASP instance and not of an individual ASA. As a result, each ASA 695 will need to register the objectives that it supports with the local 696 GRASP instance. 698 If an ASA in a neighbor device supports the requested discovery 699 objective, the device SHOULD respond to the link-local multicast with 700 a unicast Discovery Response message (Section 2.8.5) with locator 701 option(s), unless it is temporarily unavailable. Otherwise, if the 702 neighbor has cached information about an ASA that supports the 703 requested discovery objective (usually because it discovered the same 704 objective before), it SHOULD respond with a Discovery Response 705 message with a Divert option pointing to the appropriate Discovery 706 Responder. However, on a link that supports link-local multicast, it 707 SHOULD NOT respond with a cached response on an interface if it 708 learnt that information from the same interface, because the peer in 709 question will answer directly if still operational. 711 If a device has no information about the requested discovery 712 objective, and is not acting as a discovery relay (see below) it MUST 713 silently discard the Discovery message. 715 The discovery initiator MUST set a reasonable timeout on the 716 discovery process. A suggested value is 100 milliseconds multiplied 717 by the loop count embedded in the objective. 719 If no discovery response is received within the timeout, the 720 Discovery message MAY be repeated, with a newly generated Session ID 721 (Section 2.7). An exponential backoff SHOULD be used for subsequent 722 repetitions, to limit the load during busy periods. The details of 723 the backoff algorithm will depend on the use case for the objective 724 concerned but MUST be consistent with the recommendations in 725 [RFC8085] for low data-volume multicast. Frequent repetition might 726 be symptomatic of a denial of service attack. 728 After a GRASP device successfully discovers a locator for a Discovery 729 Responder supporting a specific objective, it SHOULD cache this 730 information, including the interface index [RFC3493] via which it was 731 discovered. This cache record MAY be used for future negotiation or 732 synchronization, and the locator SHOULD be passed on when appropriate 733 as a Divert option to another Discovery Initiator. 735 The cache mechanism MUST include a lifetime for each entry. The 736 lifetime is derived from a time-to-live (ttl) parameter in each 737 Discovery Response message. Cached entries MUST be ignored or 738 deleted after their lifetime expires. In some environments, 739 unplanned address renumbering might occur. In such cases, the 740 lifetime SHOULD be short compared to the typical address lifetime. 741 The discovery mechanism needs to track the node's current address to 742 ensure that Discovery Responses always indicate the correct address. 744 If multiple Discovery Responders are found for the same objective, 745 they SHOULD all be cached, unless this creates a resource shortage. 746 The method of choosing between multiple responders is an 747 implementation choice. This choice MUST be available to each ASA but 748 the GRASP implementation SHOULD provide a default choice. 750 Because Discovery Responders will be cached in a finite cache, they 751 might be deleted at any time. In this case, discovery will need to 752 be repeated. If an ASA exits for any reason, its locator might still 753 be cached for some time, and attempts to connect to it will fail. 754 ASAs need to be robust in these circumstances. 756 2.5.4.4. Discovery Relaying 758 A GRASP instance with multiple link-layer interfaces (typically 759 running in a router) MUST support discovery on all GRASP interfaces. 760 We refer to this as a 'relaying instance'. 762 Constrained Instances (Section 2.5.2) are always single-interface 763 instances and therefore MUST NOT perform discovery relaying. 765 If a relaying instance receives a Discovery message on a given 766 interface for a specific objective that it does not support and for 767 which it has not previously cached a Discovery Responder, it MUST 768 relay the query by re-issuing a new Discovery message as a link-local 769 multicast on its other GRASP interfaces. 771 The relayed discovery message MUST have the same Session ID as the 772 incoming discovery message and MUST be tagged with the IP address of 773 its original initiator (see Section 2.8.4). Note that this initiator 774 address is only used to allow for disambiguation of the Session ID 775 and is never used to address Response packets, which are sent to the 776 relaying instance, not the original initiator. 778 The relaying instance MUST decrement the loop count within the 779 objective, and MUST NOT relay the Discovery message if the result is 780 zero. Also, it MUST limit the total rate at which it relays 781 discovery messages to a reasonable value, in order to mitigate 782 possible denial of service attacks. For example, the rate limit 783 could be set to a small multiple of the observed rate of discovery 784 messages during normal operation. The relaying instance MUST cache 785 the Session ID value and initiator address of each relayed Discovery 786 message until any Discovery Responses have arrived or the discovery 787 process has timed out. To prevent loops, it MUST NOT relay a 788 Discovery message which carries a given cached Session ID and 789 initiator address more than once. These precautions avoid discovery 790 loops and mitigate potential overload. 792 Since the relay device is unaware of the timeout set by the original 793 initiator it SHOULD set a suitable timeout for the relayed discovery. 795 A suggested value is 100 milliseconds multiplied by the remaining 796 loop count. 798 The discovery results received by the relaying instance MUST in turn 799 be sent as a Discovery Response message to the Discovery message that 800 caused the relay action. 802 2.5.4.5. Rapid Mode (Discovery with Negotiation or Synchronization ) 804 A Discovery message MAY include an Objective option. This allows a 805 rapid mode of negotiation (Section 2.5.5.1) or synchronization 806 (Section 2.5.6.3). Rapid mode is currently limited to a single 807 objective for simplicity of design and implementation. A possible 808 future extension is to allow multiple objectives in rapid mode for 809 greater efficiency. 811 2.5.5. Negotiation Procedures 813 A negotiation initiator opens a transport connection to a counterpart 814 ASA using the address, protocol and port obtained during discovery. 815 It then sends a negotiation request (using M_REQ_NEG) to the 816 counterpart, including a specific negotiation objective. It may 817 request the negotiation counterpart to make a specific configuration. 818 Alternatively, it may request a certain simulation or forecast result 819 by sending a dry run configuration. The details, including the 820 distinction between a dry run and a live configuration change, will 821 be defined separately for each type of negotiation objective. Any 822 state associated with a dry run operation, such as temporarily 823 reserving a resource for subsequent use in a live run, is entirely a 824 matter for the designer of the ASA concerned. 826 Each negotiation session as a whole is subject to a timeout (default 827 GRASP_DEF_TIMEOUT milliseconds, Section 2.6), initialised when the 828 request is sent (see Section 2.8.6). If no reply message of any kind 829 is received within the timeout, the negotiation request MAY be 830 repeated, with a newly generated Session ID (Section 2.7). An 831 exponential backoff SHOULD be used for subsequent repetitions. The 832 details of the backoff algorithm will depend on the use case for the 833 objective concerned. 835 If the counterpart can immediately apply the requested configuration, 836 it will give an immediate positive (O_ACCEPT) answer (using M_END). 837 This will end the negotiation phase immediately. Otherwise, it will 838 negotiate (using M_NEGOTIATE). It will reply with a proposed 839 alternative configuration that it can apply (typically, a 840 configuration that uses fewer resources than requested by the 841 negotiation initiator). This will start a bi-directional negotiation 842 (using M_NEGOTIATE) to reach a compromise between the two ASAs. 844 The negotiation procedure is ended when one of the negotiation peers 845 sends a Negotiation Ending (M_END) message, which contains an accept 846 (O_ACCEPT) or decline (O_DECLINE) option and does not need a response 847 from the negotiation peer. Negotiation may also end in failure 848 (equivalent to a decline) if a timeout is exceeded or a loop count is 849 exceeded. When the procedure ends for whatever reason, the transport 850 connection SHOULD be closed. A transport session failure is treated 851 as a negotiation failure. 853 A negotiation procedure concerns one objective and one counterpart. 854 Both the initiator and the counterpart may take part in simultaneous 855 negotiations with various other ASAs, or in simultaneous negotiations 856 about different objectives. Thus, GRASP is expected to be used in a 857 multi-threaded mode or its logical equivalent. Certain negotiation 858 objectives may have restrictions on multi-threading, for example to 859 avoid over-allocating resources. 861 Some configuration actions, for example wavelength switching in 862 optical networks, might take considerable time to execute. The ASA 863 concerned needs to allow for this by design, but GRASP does allow for 864 a peer to insert latency in a negotiation process if necessary 865 (Section 2.8.9, M_WAIT). 867 2.5.5.1. Rapid Mode (Discovery/Negotiation Linkage) 869 A Discovery message MAY include a Negotiation Objective option. In 870 this case it is as if the initiator sent the sequence M_DISCOVERY, 871 immediately followed by M_REQ_NEG. This has implications for the 872 construction of the GRASP core, as it must carefully pass the 873 contents of the Negotiation Objective option to the ASA so that it 874 may evaluate the objective directly. When a Negotiation Objective 875 option is present the ASA replies with an M_NEGOTIATE message (or 876 M_END with O_ACCEPT if it is immediately satisfied with the 877 proposal), rather than with an M_RESPONSE. However, if the recipient 878 node does not support rapid mode, discovery will continue normally. 880 It is possible that a Discovery Response will arrive from a responder 881 that does not support rapid mode, before such a Negotiation message 882 arrives. In this case, rapid mode will not occur. 884 This rapid mode could reduce the interactions between nodes so that a 885 higher efficiency could be achieved. However, a network in which 886 some nodes support rapid mode and others do not will have complex 887 timing-dependent behaviors. Therefore, the rapid negotiation 888 function SHOULD be disabled by default. 890 2.5.6. Synchronization and Flooding Procedures 892 2.5.6.1. Unicast Synchronization 894 A synchronization initiator opens a transport connection to a 895 counterpart ASA using the address, protocol and port obtained during 896 discovery. It then sends a synchronization request (using M_REQ_SYN) 897 to the counterpart, including a specific synchronization objective. 898 The counterpart responds with a Synchronization message (M_SYNCH, 899 Section 2.8.10) containing the current value of the requested 900 synchronization objective. No further messages are needed and the 901 transport connection SHOULD be closed. A transport session failure 902 is treated as a synchronization failure. 904 If no reply message of any kind is received within a given timeout 905 (default GRASP_DEF_TIMEOUT milliseconds, Section 2.6), the 906 synchronization request MAY be repeated, with a newly generated 907 Session ID (Section 2.7). An exponential backoff SHOULD be used for 908 subsequent repetitions. The details of the backoff algorithm will 909 depend on the use case for the objective concerned. 911 2.5.6.2. Flooding 913 In the case just described, the message exchange is unicast and 914 concerns only one synchronization objective. For large groups of 915 nodes requiring the same data, synchronization flooding is available. 916 For this, a flooding initiator MAY send an unsolicited Flood 917 Synchronization message containing one or more Synchronization 918 Objective option(s), if and only if the specification of those 919 objectives permits it. This is sent as a multicast message to the 920 ALL_GRASP_NEIGHBORS multicast address (Section 2.6). 922 Receiving flood multicasts is a function of the GRASP core, as in the 923 case of discovery multicasts (Section 2.5.4.3). 925 To ensure that flooding does not result in a loop, the originator of 926 the Flood Synchronization message MUST set the loop count in the 927 objectives to a suitable value (the default is GRASP_DEF_LOOPCT). 928 Also, a suitable mechanism is needed to avoid excessive multicast 929 traffic. This mechanism MUST be defined as part of the specification 930 of the synchronization objective(s) concerned. It might be a simple 931 rate limit or a more complex mechanism such as the Trickle algorithm 932 [RFC6206]. 934 A GRASP device with multiple link-layer interfaces (typically a 935 router) MUST support synchronization flooding on all GRASP 936 interfaces. If it receives a multicast Flood Synchronization message 937 on a given interface, it MUST relay it by re-issuing a Flood 938 Synchronization message as a link-local multicast on its other GRASP 939 interfaces. The relayed message MUST have the same Session ID as the 940 incoming message and MUST be tagged with the IP address of its 941 original initiator. 943 Link-layer Flooding is supported by GRASP by setting the loop count 944 to 1, and sending with a link-local source address. Floods with 945 link-local source addresses and a loop count other than 1 are 946 invalid, and such messages MUST be discarded. 948 The relaying device MUST decrement the loop count within the first 949 objective, and MUST NOT relay the Flood Synchronization message if 950 the result is zero. Also, it MUST limit the total rate at which it 951 relays Flood Synchronization messages to a reasonable value, in order 952 to mitigate possible denial of service attacks. For example, the 953 rate limit could be set to a small multiple of the observed rate of 954 flood messages during normal operation. The relaying device MUST 955 cache the Session ID value and initiator address of each relayed 956 Flood Synchronization message for a time not less than twice 957 GRASP_DEF_TIMEOUT milliseconds. To prevent loops, it MUST NOT relay 958 a Flood Synchronization message which carries a given cached Session 959 ID and initiator address more than once. These precautions avoid 960 synchronization loops and mitigate potential overload. 962 Note that this mechanism is unreliable in the case of sleeping nodes, 963 or new nodes that join the network, or nodes that rejoin the network 964 after a fault. An ASA that initiates a flood SHOULD repeat the flood 965 at a suitable frequency, which MUST be consistent with the 966 recommendations in [RFC8085] for low data-volume multicast. The ASA 967 SHOULD also act as a synchronization responder for the objective(s) 968 concerned. Thus nodes that require an objective subject to flooding 969 can either wait for the next flood or request unicast synchronization 970 for that objective. 972 The multicast messages for synchronization flooding are subject to 973 the security rules in Section 2.5.1. In practice this means that 974 they MUST NOT be transmitted and MUST be ignored on receipt unless 975 there is an operational ACP or equivalent strong security in place. 976 However, because of the security weakness of link-local multicast 977 (Section 4), synchronization objectives that are flooded SHOULD NOT 978 contain unencrypted private information and SHOULD be validated by 979 the recipient ASA. 981 2.5.6.3. Rapid Mode (Discovery/Synchronization Linkage) 983 A Discovery message MAY include a Synchronization Objective option. 984 In this case the Discovery message also acts as a Request 985 Synchronization message to indicate to the Discovery Responder that 986 it could directly reply to the Discovery Initiator with a 987 Synchronization message Section 2.8.10 with synchronization data for 988 rapid processing, if the discovery target supports the corresponding 989 synchronization objective. The design implications are similar to 990 those discussed in Section 2.5.5.1. 992 It is possible that a Discovery Response will arrive from a responder 993 that does not support rapid mode, before such a Synchronization 994 message arrives. In this case, rapid mode will not occur. 996 This rapid mode could reduce the interactions between nodes so that a 997 higher efficiency could be achieved. However, a network in which 998 some nodes support rapid mode and others do not will have complex 999 timing-dependent behaviors. Therefore, the rapid synchronization 1000 function SHOULD be configured off by default and MAY be configured on 1001 or off by Intent. 1003 2.6. GRASP Constants 1005 o ALL_GRASP_NEIGHBORS 1007 A link-local scope multicast address used by a GRASP-enabled 1008 device to discover GRASP-enabled neighbor (i.e., on-link) devices. 1009 All devices that support GRASP are members of this multicast 1010 group. 1012 * IPv6 multicast address: TBD1 1014 * IPv4 multicast address: TBD2 1016 o GRASP_LISTEN_PORT (TBD3) 1018 A well-known UDP user port that every GRASP-enabled network device 1019 MUST always listen to for link-local multicasts. This user port 1020 MAY also be used to listen for TCP or UDP unicast messages in a 1021 simple implementation of GRASP (Section 2.5.3). 1023 o GRASP_DEF_TIMEOUT (60000 milliseconds) 1025 The default timeout used to determine that an operation has failed 1026 to complete. 1028 o GRASP_DEF_LOOPCT (6) 1030 The default loop count used to determine that a negotiation has 1031 failed to complete, and to avoid looping messages. 1033 o GRASP_DEF_MAX_SIZE (2048) 1034 The default maximum message size in bytes. 1036 2.7. Session Identifier (Session ID) 1038 This is an up to 32-bit opaque value used to distinguish multiple 1039 sessions between the same two devices. A new Session ID MUST be 1040 generated by the initiator for every new Discovery, Flood 1041 Synchronization or Request message. All responses and follow-up 1042 messages in the same discovery, synchronization or negotiation 1043 procedure MUST carry the same Session ID. 1045 The Session ID SHOULD have a very low collision rate locally. It 1046 MUST be generated by a pseudo-random number generator (PRNG) using a 1047 locally generated seed which is unlikely to be used by any other 1048 device in the same network. The PRNG SHOULD be cryptographically 1049 strong [RFC4086]. When allocating a new Session ID, GRASP MUST check 1050 that the value is not already in use and SHOULD check that it has not 1051 been used recently, by consulting a cache of current and recent 1052 sessions. In the unlikely event of a clash, GRASP MUST generate a 1053 new value. 1055 However, there is a finite probability that two nodes might generate 1056 the same Session ID value. For that reason, when a Session ID is 1057 communicated via GRASP, the receiving node MUST tag it with the 1058 initiator's IP address to allow disambiguation. In the highly 1059 unlikely event of two peers opening sessions with the same Session ID 1060 value, this tag will allow the two sessions to be distinguished. 1061 Multicast GRASP messages and their responses, which may be relayed 1062 between links, therefore include a field that carries the initiator's 1063 global IP address. 1065 There is a highly unlikely race condition in which two peers start 1066 simultaneous negotiation sessions with each other using the same 1067 Session ID value. Depending on various implementation choices, this 1068 might lead to the two sessions being confused. See Section 2.8.6 for 1069 details of how to avoid this. 1071 2.8. GRASP Messages 1073 2.8.1. Message Overview 1075 This section defines the GRASP message format and message types. 1076 Message types not listed here are reserved for future use. 1078 The messages currently defined are: 1080 Discovery and Discovery Response (M_DISCOVERY, M_RESPONSE). 1082 Request Negotiation, Negotiation, Confirm Waiting and Negotiation 1083 End (M_REQ_NEG, M_NEGOTIATE, M_WAIT, M_END). 1085 Request Synchronization, Synchronization, and Flood 1086 Synchronization (M_REQ_SYN, M_SYNCH, M_FLOOD. 1088 No Operation and Invalid (M_NOOP, M_INVALID). 1090 2.8.2. GRASP Message Format 1092 GRASP messages share an identical header format and a variable format 1093 area for options. GRASP message headers and options are transmitted 1094 in Concise Binary Object Representation (CBOR) [RFC7049]. In this 1095 specification, they are described using CBOR data definition language 1096 (CDDL) [I-D.greevenbosch-appsawg-cbor-cddl]. Fragmentary CDDL is 1097 used to describe each item in this section. A complete and normative 1098 CDDL specification of GRASP is given in Section 5, including 1099 constants such as message types. 1101 Every GRASP message, except the No Operation message, carries a 1102 Session ID (Section 2.7). Options are then presented serially in the 1103 options field. 1105 In fragmentary CDDL, every GRASP message follows the pattern: 1107 grasp-message = (message .within message-structure) / noop-message 1109 message-structure = [MESSAGE_TYPE, session-id, ?initiator, 1110 *grasp-option] 1112 MESSAGE_TYPE = 1..255 1113 session-id = 0..4294967295 ;up to 32 bits 1114 grasp-option = any 1116 The MESSAGE_TYPE indicates the type of the message and thus defines 1117 the expected options. Any options received that are not consistent 1118 with the MESSAGE_TYPE SHOULD be silently discarded. 1120 The No Operation (noop) message is described in Section 2.8.13. 1122 The various MESSAGE_TYPE values are defined in Section 5. 1124 All other message elements are described below and formally defined 1125 in Section 5. 1127 If an unrecognized MESSAGE_TYPE is received in a unicast message, an 1128 Invalid message (Section 2.8.12) MAY be returned. Otherwise the 1129 message MAY be logged and MUST be discarded. If an unrecognized 1130 MESSAGE_TYPE is received in a multicast message, it MAY be logged and 1131 MUST be silently discarded. 1133 2.8.3. Message Size 1135 GRASP nodes MUST be able to receive unicast messages of at least 1136 GRASP_DEF_MAX_SIZE bytes. GRASP nodes MUST NOT send unicast messages 1137 longer than GRASP_DEF_MAX_SIZE bytes unless a longer size is 1138 explicitly allowed for the objective concerned. For example, GRASP 1139 negotiation itself could be used to agree on a longer message size. 1141 The message parser used by GRASP should be configured to know about 1142 the GRASP_DEF_MAX_SIZE, or any larger negotiated message size, so 1143 that it may defend against overly long messages. 1145 The maximum size of multicast messages (M_DISCOVERY and M_FLOOD) 1146 depends on the link layer technology or link adaptation layer in use. 1148 2.8.4. Discovery Message 1150 In fragmentary CDDL, a Discovery message follows the pattern: 1152 discovery-message = [M_DISCOVERY, session-id, initiator, objective] 1154 A discovery initiator sends a Discovery message to initiate a 1155 discovery process for a particular objective option. 1157 The discovery initiator sends all Discovery messages via UDP to port 1158 GRASP_LISTEN_PORT at the link-local ALL_GRASP_NEIGHBORS multicast 1159 address on each link-layer interface in use by GRASP. It then 1160 listens for unicast TCP responses on a given port, and stores the 1161 discovery results (including responding discovery objectives and 1162 corresponding unicast locators). 1164 The listening port used for TCP MUST be the same port as used for 1165 sending the Discovery UDP multicast, on a given interface. In an 1166 implementation with a single GRASP instance in a node this MAY be 1167 GRASP_LISTEN_PORT. To support multiple instances in the same node, 1168 the GRASP discovery mechanism in each instance needs to find, for 1169 each interface, a dynamic port that it can bind to for both sending 1170 UDP link-local multicast and listening for TCP, before initiating any 1171 discovery. 1173 The 'initiator' field in the message is a globally unique IP address 1174 of the initiator, for the sole purpose of disambiguating the Session 1175 ID in other nodes. If for some reason the initiator does not have a 1176 globally unique IP address, it MUST use a link-local address for this 1177 purpose that is highly likely to be unique, for example using 1179 [RFC7217]. Determination of a node's globally unique IP address is 1180 implementation-dependent. 1182 A Discovery message MUST include exactly one of the following: 1184 o a discovery objective option (Section 2.10.1). Its loop count 1185 MUST be set to a suitable value to prevent discovery loops 1186 (default value is GRASP_DEF_LOOPCT). If the discovery initiator 1187 requires only on-link responses, the loop count MUST be set to 1. 1189 o a negotiation objective option (Section 2.10.1). This is used 1190 both for the purpose of discovery and to indicate to the discovery 1191 target that it MAY directly reply to the discovery initiatior with 1192 a Negotiation message for rapid processing, if it could act as the 1193 corresponding negotiation counterpart. The sender of such a 1194 Discovery message MUST initialize a negotiation timer and loop 1195 count in the same way as a Request Negotiation message 1196 (Section 2.8.6). 1198 o a synchronization objective option (Section 2.10.1). This is used 1199 both for the purpose of discovery and to indicate to the discovery 1200 target that it MAY directly reply to the discovery initiator with 1201 a Synchronization message for rapid processing, if it could act as 1202 the corresponding synchronization counterpart. Its loop count 1203 MUST be set to a suitable value to prevent discovery loops 1204 (default value is GRASP_DEF_LOOPCT). 1206 As mentioned in Section 2.5.4.2, a Discovery message MAY be sent 1207 unicast to a peer node, which SHOULD then proceed exactly as if the 1208 message had been multicast. 1210 2.8.5. Discovery Response Message 1212 In fragmentary CDDL, a Discovery Response message follows the 1213 pattern: 1215 response-message = [M_RESPONSE, session-id, initiator, ttl, 1216 (+locator-option // divert-option), ?objective)] 1218 ttl = 0..4294967295 ; in milliseconds 1220 A node which receives a Discovery message SHOULD send a Discovery 1221 Response message if and only if it can respond to the discovery. 1223 It MUST contain the same Session ID and initiator as the Discovery 1224 message. 1226 It MUST contain a time-to-live (ttl) for the validity of the 1227 response, given as a positive integer value in milliseconds. Zero 1228 implies a value significantly greater than GRASP_DEF_TIMEOUT 1229 milliseconds (Section 2.6). A suggested value is ten times that 1230 amount. 1232 It MAY include a copy of the discovery objective from the 1233 Discovery message. 1235 It is sent to the sender of the Discovery message via TCP at the port 1236 used to send the Discovery message (as explained in Section 2.8.4). 1237 In the case of a relayed Discovery message, the Discovery Response is 1238 thus sent to the relay, not the original initiator. 1240 In all cases, the transport session SHOULD be closed after sending 1241 the Discovery Response. A transport session failure is treated as no 1242 response. 1244 If the responding node supports the discovery objective of the 1245 discovery, it MUST include at least one kind of locator option 1246 (Section 2.9.5) to indicate its own location. A sequence of multiple 1247 kinds of locator options (e.g. IP address option and FQDN option) is 1248 also valid. 1250 If the responding node itself does not support the discovery 1251 objective, but it knows the locator of the discovery objective, then 1252 it SHOULD respond to the discovery message with a divert option 1253 (Section 2.9.2) embedding a locator option or a combination of 1254 multiple kinds of locator options which indicate the locator(s) of 1255 the discovery objective. 1257 More details on the processing of Discovery Responses are given in 1258 Section 2.5.4. 1260 2.8.6. Request Messages 1262 In fragmentary CDDL, Request Negotiation and Request Synchronization 1263 messages follow the patterns: 1265 request-negotiation-message = [M_REQ_NEG, session-id, objective] 1267 request-synchronization-message = [M_REQ_SYN, session-id, objective] 1269 A negotiation or synchronization requesting node sends the 1270 appropriate Request message to the unicast address of the negotiation 1271 or synchronization counterpart, using the appropriate protocol and 1272 port numbers (selected from the discovery result). If the discovery 1273 result is an FQDN, it will be resolved first. 1275 A Request message MUST include the relevant objective option. In the 1276 case of Request Negotiation, the objective option MUST include the 1277 requested value. 1279 When an initiator sends a Request Negotiation message, it MUST 1280 initialize a negotiation timer for the new negotiation thread. The 1281 default is GRASP_DEF_TIMEOUT milliseconds. Unless this timeout is 1282 modified by a Confirm Waiting message (Section 2.8.9), the initiator 1283 will consider that the negotiation has failed when the timer expires. 1285 Similarly, when an initiator sends a Request Synchronization, it 1286 SHOULD initialize a synchronization timer. The default is 1287 GRASP_DEF_TIMEOUT milliseconds. The initiator will consider that 1288 synchronization has failed if there is no response before the timer 1289 expires. 1291 When an initiator sends a Request message, it MUST initialize the 1292 loop count of the objective option with a value defined in the 1293 specification of the option or, if no such value is specified, with 1294 GRASP_DEF_LOOPCT. 1296 If a node receives a Request message for an objective for which no 1297 ASA is currently listening, it MUST immediately close the relevant 1298 socket to indicate this to the initiator. This is to avoid 1299 unnecessary timeouts if, for example, an ASA exits prematurely but 1300 the GRASP core is listening on its behalf. 1302 To avoid the highly unlikely race condition in which two nodes 1303 simultaneously request sessions with each other using the same 1304 Session ID (Section 2.7), when a node receives a Request message, it 1305 MUST verify that the received Session ID is not already locally 1306 active. In case of a clash, it MUST discard the Request message, in 1307 which case the initiator will detect a timeout. 1309 2.8.7. Negotiation Message 1311 In fragmentary CDDL, a Negotiation message follows the pattern: 1313 negotiate-message = [M_NEGOTIATE, session-id, objective] 1315 A negotiation counterpart sends a Negotiation message in response to 1316 a Request Negotiation message, a Negotiation message, or a Discovery 1317 message in Rapid Mode. A negotiation process MAY include multiple 1318 steps. 1320 The Negotiation message MUST include the relevant Negotiation 1321 Objective option, with its value updated according to progress in the 1322 negotiation. The sender MUST decrement the loop count by 1. If the 1323 loop count becomes zero the message MUST NOT be sent. In this case 1324 the negotiation session has failed and will time out. 1326 2.8.8. Negotiation End Message 1328 In fragmentary CDDL, a Negotiation End message follows the pattern: 1330 end-message = [M_END, session-id, accept-option / decline-option] 1332 A negotiation counterpart sends an Negotiation End message to close 1333 the negotiation. It MUST contain either an accept or a decline 1334 option, defined in Section 2.9.3 and Section 2.9.4. It could be sent 1335 either by the requesting node or the responding node. 1337 2.8.9. Confirm Waiting Message 1339 In fragmentary CDDL, a Confirm Waiting message follows the pattern: 1341 wait-message = [M_WAIT, session-id, waiting-time] 1342 waiting-time = 0..4294967295 ; in milliseconds 1344 A responding node sends a Confirm Waiting message to ask the 1345 requesting node to wait for a further negotiation response. It might 1346 be that the local process needs more time or that the negotiation 1347 depends on another triggered negotiation. This message MUST NOT 1348 include any other options. When received, the waiting time value 1349 overwrites and restarts the current negotiation timer 1350 (Section 2.8.6). 1352 The responding node SHOULD send a Negotiation, Negotiation End or 1353 another Confirm Waiting message before the negotiation timer expires. 1354 If not, when the initiator's timer expires, the initiator MUST treat 1355 the negotiation procedure as failed. 1357 2.8.10. Synchronization Message 1359 In fragmentary CDDL, a Synchronization message follows the pattern: 1361 synch-message = [M_SYNCH, session-id, objective] 1363 A node which receives a Request Synchronization, or a Discovery 1364 message in Rapid Mode, sends back a unicast Synchronization message 1365 with the synchronization data, in the form of a GRASP Option for the 1366 specific synchronization objective present in the Request 1367 Synchronization. 1369 2.8.11. Flood Synchronization Message 1371 In fragmentary CDDL, a Flood Synchronization message follows the 1372 pattern: 1374 flood-message = [M_FLOOD, session-id, initiator, ttl, 1375 +[objective, (locator-option / [])]] 1377 ttl = 0..4294967295 ; in milliseconds 1379 A node MAY initiate flooding by sending an unsolicited Flood 1380 Synchronization Message with synchronization data. This MAY be sent 1381 to port GRASP_LISTEN_PORT at the link-local ALL_GRASP_NEIGHBORS 1382 multicast address, in accordance with the rules in Section 2.5.6. 1384 The initiator address is provided, as described for Discovery 1385 messages (Section 2.8.4), only to disambiguate the Session ID. 1387 The message MUST contain a time-to-live (ttl) for the validity of 1388 the contents, given as a positive integer value in milliseconds. 1389 There is no default; zero indicates an indefinite lifetime. 1391 The synchronization data are in the form of GRASP Option(s) for 1392 specific synchronization objective(s). The loop count(s) MUST be 1393 set to a suitable value to prevent flood loops (default value is 1394 GRASP_DEF_LOOPCT). 1396 Each objective option MAY be followed by a locator option 1397 associated with the flooded objective. In its absence, an empty 1398 option MUST be included to indicate a null locator. 1400 A node that receives a Flood Synchronization message MUST cache the 1401 received objectives for use by local ASAs. Each cached objective 1402 MUST be tagged with the locator option sent with it, or with a null 1403 tag if an empty locator option was sent. If a subsequent Flood 1404 Synchronization message carrying an objective with same name and the 1405 same tag, the corresponding cached copy of the objective MUST be 1406 overwritten. If a subsequent Flood Synchronization message carrying 1407 an objective with same name arrives with a different tag, a new 1408 cached entry MUST be created. 1410 Note: the purpose of this mechanism is to allow the recipient of 1411 flooded values to distinguish between different senders of the same 1412 objective, and if necessary communicate with them using the locator, 1413 protocol and port included in the locator option. Many objectives 1414 will not need this mechanism, so they will be flooded with a null 1415 locator. 1417 Cached entries MUST be ignored or deleted after their lifetime 1418 expires. 1420 2.8.12. Invalid Message 1422 In fragmentary CDDL, an Invalid message follows the pattern: 1424 invalid-message = [M_INVALID, session-id, ?any] 1426 This message MAY be sent by an implementation in response to an 1427 incoming unicast message that it considers invalid. The session-id 1428 MUST be copied from the incoming message. The content SHOULD be 1429 diagnostic information such as a partial copy of the invalid message 1430 up to the maximum message size. An M_INVALID message MAY be silently 1431 ignored by a recipient. However, it could be used in support of 1432 extensibility, since it indicates that the remote node does not 1433 support a new or obsolete message or option. 1435 An M_INVALID message MUST NOT be sent in response to an M_INVALID 1436 message. 1438 2.8.13. No Operation Message 1440 In fragmentary CDDL, a No Operation message follows the pattern: 1442 noop-message = [M_NOOP] 1444 This message MAY be sent by an implementation that for practical 1445 reasons needs to initialize a socket. It MUST be silently ignored by 1446 a recipient. 1448 2.9. GRASP Options 1450 This section defines the GRASP options for the negotiation and 1451 synchronization protocol signaling. Additional options may be 1452 defined in the future. 1454 2.9.1. Format of GRASP Options 1456 GRASP options are CBOR objects that MUST start with an unsigned 1457 integer identifying the specific option type carried in this option. 1458 These option types are formally defined in Section 5. Apart from 1459 that the only format requirement is that each option MUST be a well- 1460 formed CBOR object. In general a CBOR array format is RECOMMENDED to 1461 limit overhead. 1463 GRASP options may be defined to include encapsulated GRASP options. 1465 2.9.2. Divert Option 1467 The Divert option is used to redirect a GRASP request to another 1468 node, which may be more appropriate for the intended negotiation or 1469 synchronization. It may redirect to an entity that is known as a 1470 specific negotiation or synchronization counterpart (on-link or off- 1471 link) or a default gateway. The divert option MUST only be 1472 encapsulated in Discovery Response messages. If found elsewhere, it 1473 SHOULD be silently ignored. 1475 A discovery initiator MAY ignore a Divert option if it only requires 1476 direct discovery responses. 1478 In fragmentary CDDL, the Divert option follows the pattern: 1480 divert-option = [O_DIVERT, +locator-option] 1482 The embedded Locator Option(s) (Section 2.9.5) point to diverted 1483 destination target(s) in response to a Discovery message. 1485 2.9.3. Accept Option 1487 The accept option is used to indicate to the negotiation counterpart 1488 that the proposed negotiation content is accepted. 1490 The accept option MUST only be encapsulated in Negotiation End 1491 messages. If found elsewhere, it SHOULD be silently ignored. 1493 In fragmentary CDDL, the Accept option follows the pattern: 1495 accept-option = [O_ACCEPT] 1497 2.9.4. Decline Option 1499 The decline option is used to indicate to the negotiation counterpart 1500 the proposed negotiation content is declined and end the negotiation 1501 process. 1503 The decline option MUST only be encapsulated in Negotiation End 1504 messages. If found elsewhere, it SHOULD be silently ignored. 1506 In fragmentary CDDL, the Decline option follows the pattern: 1508 decline-option = [O_DECLINE, ?reason] 1509 reason = text ;optional UTF-8 error message 1511 Note: there might be scenarios where an ASA wants to decline the 1512 proposed value and restart the negotiation process. In this case it 1513 is an implementation choice whether to send a Decline option or to 1514 continue with a Negotiate message, with an objective option that 1515 contains a null value, or one that contains a new value that might 1516 achieve convergence. 1518 2.9.5. Locator Options 1520 These locator options are used to present reachability information 1521 for an ASA, a device or an interface. They are Locator IPv6 Address 1522 Option, Locator IPv4 Address Option, Locator FQDN (Fully Qualified 1523 Domain Name) Option and URI (Uniform Resource Identifier) Option. 1525 Since ASAs will normally run as independent user programs, locator 1526 options need to indicate the network layer locator plus the transport 1527 protocol and port number for reaching the target. For this reason, 1528 the Locator Options for IP addresses and FQDNs include this 1529 information explicitly. In the case of the URI Option, this 1530 information can be encoded in the URI itself. 1532 Note: It is assumed that all locators used in locator options are in 1533 scope throughout the GRASP domain. As stated in Section 2.2, GRASP 1534 is not intended to work across disjoint addressing or naming realms. 1536 2.9.5.1. Locator IPv6 address option 1538 In fragmentary CDDL, the IPv6 address option follows the pattern: 1540 ipv6-locator-option = [O_IPv6_LOCATOR, ipv6-address, 1541 transport-proto, port-number] 1542 ipv6-address = bytes .size 16 1544 transport-proto = IPPROTO_TCP / IPPROTO_UDP 1545 IPPROTO_TCP = 6 1546 IPPROTO_UDP = 17 1547 port-number = 0..65535 1549 The content of this option is a binary IPv6 address followed by the 1550 protocol number and port number to be used. 1552 Note 1: The IPv6 address MUST normally have global scope. However, 1553 during initialization, a link-local address MAY be used for specific 1554 objectives only (Section 2.5.2). In this case the corresponding 1555 Discovery Response message MUST be sent via the interface to which 1556 the link-local address applies. 1558 Note 2: A link-local IPv6 address MUST NOT be used when this option 1559 is included in a Divert option. 1561 Note 3: The IPPROTO values are taken from the existing IANA Protocol 1562 Numbers registry in order to specify TCP or UDP. If GRASP requires 1563 future values that are not in that registry, a new registry for 1564 values outside the range 0..255 will be needed. 1566 2.9.5.2. Locator IPv4 address option 1568 In fragmentary CDDL, the IPv4 address option follows the pattern: 1570 ipv4-locator-option = [O_IPv4_LOCATOR, ipv4-address, 1571 transport-proto, port-number] 1572 ipv4-address = bytes .size 4 1574 The content of this option is a binary IPv4 address followed by the 1575 protocol number and port number to be used. 1577 Note: If an operator has internal network address translation for 1578 IPv4, this option MUST NOT be used within the Divert option. 1580 2.9.5.3. Locator FQDN option 1582 In fragmentary CDDL, the FQDN option follows the pattern: 1584 fqdn-locator-option = [O_FQDN_LOCATOR, text, 1585 transport-proto, port-number] 1587 The content of this option is the Fully Qualified Domain Name of the 1588 target followed by the protocol number and port number to be used. 1590 Note 1: Any FQDN which might not be valid throughout the network in 1591 question, such as a Multicast DNS name [RFC6762], MUST NOT be used 1592 when this option is used within the Divert option. 1594 Note 2: Normal GRASP operations are not expected to use this option. 1595 It is intended for special purposes such as discovering external 1596 services. 1598 2.9.5.4. Locator URI option 1600 In fragmentary CDDL, the URI option follows the pattern: 1602 uri-locator = [O_URI_LOCATOR, text, 1603 transport-proto / null, port-number / null] 1605 The content of this option is the Uniform Resource Identifier of the 1606 target followed by the protocol number and port number to be used (or 1607 by null values if not required) [RFC3986]. 1609 Note 1: Any URI which might not be valid throughout the network in 1610 question, such as one based on a Multicast DNS name [RFC6762], MUST 1611 NOT be used when this option is used within the Divert option. 1613 Note 2: Normal GRASP operations are not expected to use this option. 1614 It is intended for special purposes such as discovering external 1615 services. Therefore its use is not further described in this 1616 specification. 1618 2.10. Objective Options 1620 2.10.1. Format of Objective Options 1622 An objective option is used to identify objectives for the purposes 1623 of discovery, negotiation or synchronization. All objectives MUST be 1624 in the following format, described in fragmentary CDDL: 1626 objective = [objective-name, objective-flags, loop-count, ?objective-value] 1628 objective-name = text 1629 objective-value = any 1630 loop-count = 0..255 1632 All objectives are identified by a unique name which is a UTF-8 1633 string [RFC3629], to be compared byte by byte. 1635 The names of generic objectives MUST NOT include a colon (":") and 1636 MUST be registered with IANA (Section 6). 1638 The names of privately defined objectives MUST include at least one 1639 colon (":"). The string preceding the last colon in the name MUST be 1640 globally unique and in some way identify the entity or person 1641 defining the objective. The following three methods MAY be used to 1642 create such a globally unique string: 1644 1. The unique string is a decimal number representing a registered 1645 32 bit Private Enterprise Number (PEN) [I-D.liang-iana-pen] that 1646 uniquely identifies the enterprise defining the objective. 1648 2. The unique string is a fully qualified domain name that uniquely 1649 identifies the entity or person defining the objective. 1651 3. The unique string is an email address that uniquely identifies 1652 the entity or person defining the objective. 1654 The GRASP protocol treats the objective name as an opaque string. 1655 For example, "EX1", "411:EX1", "example.com:EX1", "example.org:EX1 1656 and "user@example.org:EX1" would be five different objectives. 1658 The 'objective-flags' field is described below. 1660 The 'loop-count' field is used for terminating negotiation as 1661 described in Section 2.8.7. It is also used for terminating 1662 discovery as described in Section 2.5.4, and for terminating flooding 1663 as described in Section 2.5.6.2. It is placed in the objective 1664 rather than in the GRASP message format because, as far as the ASA is 1665 concerned, it is a property of the objective itself. 1667 The 'objective-value' field is to express the actual value of a 1668 negotiation or synchronization objective. Its format is defined in 1669 the specification of the objective and may be a simple value or a 1670 data structure of any kind, as long as it can be represented in CBOR. 1671 It is optional because it is optional in a Discovery or Discovery 1672 Response message. 1674 2.10.2. Objective flags 1676 An objective may be relevant for discovery only, for discovery and 1677 negotiation, or for discovery and synchronization. This is expressed 1678 in the objective by logical flag bits: 1680 objective-flags = uint .bits objective-flag 1681 objective-flag = &( 1682 F_DISC: 0 ; valid for discovery 1683 F_NEG: 1 ; valid for negotiation 1684 F_SYNCH: 2 ; valid for synchronization 1685 F_NEG_DRY: 3 ; negotiation is dry-run 1686 ) 1688 These bits are independent and may be combined appropriately, e.g. 1689 (F_DISC and F_SYNCH) or (F_DISC and F_NEG) or (F_DISC and F_NEG and 1690 F_NEG_DRY). 1692 Note that for a given negotiation session, an objective must be 1693 either used for negotiation, or for dry-run negotiation. Mixing the 1694 two modes in a single negotiation is not possible. 1696 2.10.3. General Considerations for Objective Options 1698 As mentioned above, Objective Options MUST be assigned a unique name. 1699 As long as privately defined Objective Options obey the rules above, 1700 this document does not restrict their choice of name, but the entity 1701 or person concerned SHOULD publish the names in use. 1703 Names are expressed as UTF-8 strings for convenience in designing 1704 Objective Options for localized use. For generic usage, names 1705 expressed in the ASCII subset of UTF-8 are RECOMMENDED. Designers 1706 planning to use non-ASCII names are strongly advised to consult 1707 [RFC7564] or its successor to understand the complexities involved. 1708 Since the GRASP protocol compares names byte by byte, all issues of 1709 Unicode profiling and canonicalization MUST be specified in the 1710 design of the Objective Option. 1712 All Objective Options MUST respect the CBOR patterns defined above as 1713 "objective" and MUST replace the "any" field with a valid CBOR data 1714 definition for the relevant use case and application. 1716 An Objective Option that contains no additional fields beyond its 1717 "loop-count" can only be a discovery objective and MUST only be used 1718 in Discovery and Discovery Response messages. 1720 The Negotiation Objective Options contain negotiation objectives, 1721 which vary according to different functions/services. They MUST be 1722 carried by Discovery, Request Negotiation or Negotiation messages 1723 only. The negotiation initiator MUST set the initial "loop-count" to 1724 a value specified in the specification of the objective or, if no 1725 such value is specified, to GRASP_DEF_LOOPCT. 1727 For most scenarios, there should be initial values in the negotiation 1728 requests. Consequently, the Negotiation Objective options MUST 1729 always be completely presented in a Request Negotiation message, or 1730 in a Discovery message in rapid mode. If there is no initial value, 1731 the value field SHOULD be set to the 'null' value defined by CBOR. 1733 Synchronization Objective Options are similar, but MUST be carried by 1734 Discovery, Discovery Response, Request Synchronization, or Flood 1735 Synchronization messages only. They include value fields only in 1736 Synchronization or Flood Synchronization messages. 1738 The design of an objective interacts in various ways with the design 1739 of the ASAs that will use it. ASA design considerations are 1740 discussed in [I-D.carpenter-anima-asa-guidelines]. 1742 2.10.4. Organizing of Objective Options 1744 Generic objective options MUST be specified in documents available to 1745 the public and SHOULD be designed to use either the negotiation or 1746 the synchronization mechanism described above. 1748 As noted earlier, one negotiation objective is handled by each GRASP 1749 negotiation thread. Therefore, a negotiation objective, which is 1750 based on a specific function or action, SHOULD be organized as a 1751 single GRASP option. It is NOT RECOMMENDED to organize multiple 1752 negotiation objectives into a single option, nor to split a single 1753 function or action into multiple negotiation objectives. 1755 It is important to understand that GRASP negotiation does not support 1756 transactional integrity. If transactional integrity is needed for a 1757 specific objective, this must be ensured by the ASA. For example, an 1758 ASA might need to ensure that it only participates in one negotiation 1759 thread at the same time. Such an ASA would need to stop listening 1760 for incoming negotiation requests before generating an outgoing 1761 negotiation request. 1763 A synchronization objective SHOULD be organized as a single GRASP 1764 option. 1766 Some objectives will support more than one operational mode. An 1767 example is a negotiation objective with both a "dry run" mode (where 1768 the negotiation is to find out whether the other end can in fact make 1769 the requested change without problems) and a "live" mode, as 1770 explained in Section 2.5.5. The semantics of such modes will be 1771 defined in the specification of the objectives. These objectives 1772 SHOULD include flags indicating the applicable mode(s). 1774 An issue requiring particular attention is that GRASP itself is not a 1775 transactionally safe protocol. Any state associated with a dry run 1776 operation, such as temporarily reserving a resource for subsequent 1777 use in a live run, is entirely a matter for the designer of the ASA 1778 concerned. 1780 As indicated in Section 2.1, an objective's value may include 1781 multiple parameters. Parameters might be categorized into two 1782 classes: the obligatory ones presented as fixed fields; and the 1783 optional ones presented in some other form of data structure embedded 1784 in CBOR. The format might be inherited from an existing management 1785 or configuration protocol, with the objective option acting as a 1786 carrier for that format. The data structure might be defined in a 1787 formal language, but that is a matter for the specifications of 1788 individual objectives. There are many candidates, according to the 1789 context, such as ABNF, RBNF, XML Schema, YANG, etc. The GRASP 1790 protocol itself is agnostic on these questions. The only restriction 1791 is that the format can be mapped into CBOR. 1793 It is NOT RECOMMENDED to mix parameters that have significantly 1794 different response time characteristics in a single objective. 1795 Separate objectives are more suitable for such a scenario. 1797 All objectives MUST support GRASP discovery. However, as mentioned 1798 in Section 2.3, it is acceptable for an ASA to use an alternative 1799 method of discovery. 1801 Normally, a GRASP objective will refer to specific technical 1802 parameters as explained in Section 2.1. However, it is acceptable to 1803 define an abstract objective for the purpose of managing or 1804 coordinating ASAs. It is also acceptable to define a special-purpose 1805 objective for purposes such as trust bootstrapping or formation of 1806 the ACP. 1808 To guarantee convergence, a limited number of rounds or a timeout is 1809 needed for each negotiation objective. Therefore, the definition of 1810 each negotiation objective SHOULD clearly specify this, for example a 1811 default loop count and timeout, so that the negotiation can always be 1812 terminated properly. If not, the GRASP defaults will apply. 1814 There must be a well-defined procedure for concluding that a 1815 negotiation cannot succeed, and if so deciding what happens next 1816 (e.g., deadlock resolution, tie-breaking, or revert to best-effort 1817 service). This MUST be specified for individual negotiation 1818 objectives. 1820 2.10.5. Experimental and Example Objective Options 1822 The names "EX0" through "EX9" have been reserved for experimental 1823 options. Multiple names have been assigned because a single 1824 experiment may use multiple options simultaneously. These 1825 experimental options are highly likely to have different meanings 1826 when used for different experiments. Therefore, they SHOULD NOT be 1827 used without an explicit human decision and MUST NOT be used in 1828 unmanaged networks such as home networks. 1830 These names are also RECOMMENDED for use in documentation examples. 1832 3. Implementation Status [RFC Editor: please remove] 1834 Two prototype implementations of GRASP have been made. 1836 3.1. BUPT C++ Implementation 1838 o Name: BaseNegotiator.cpp, msg.cpp, Client.cpp, Server.cpp 1840 o Description: C++ implementation of GRASP core and API 1842 o Maturity: Prototype code, interoperable between Ubuntu. 1844 o Coverage: Corresponds to draft-carpenter-anima-gdn-protocol-03. 1845 Since it was implemented based on the old version draft, the most 1846 significant limitations comparing to current protocol design 1847 include: 1849 * Not support CBOR 1850 * Not support Flooding 1852 * Not support loop avoidance 1854 * only coded for IPv6, any IPv4 is accidental 1856 o Licensing: Huawei License. 1858 o Experience: https://github.com/liubingpang/IETF-Anima-Signaling- 1859 Protocol/blob/master/README.md 1861 o Contact: https://github.com/liubingpang/IETF-Anima-Signaling- 1862 Protocol 1864 3.2. Python Implementation 1866 o Name: graspy 1868 o Description: Python 3 implementation of GRASP core and API. 1870 o Maturity: Prototype code, interoperable between Windows 7 and 1871 Linux. 1873 o Coverage: Corresponds to draft-ietf-anima-grasp-13. Limitations 1874 include: 1876 * insecure: uses a dummy ACP module 1878 * only coded for IPv6, any IPv4 is accidental 1880 * FQDN and URI locators incompletely supported 1882 * no code for rapid mode 1884 * relay code is lazy (no rate control) 1886 * all unicast transactions use TCP (no unicast UDP). 1887 Experimental code for unicast UDP proved to be complex and 1888 brittle. 1890 * optional Objective option in Response messages not implemented 1892 * workarounds for defects in Python socket module and Windows 1893 socket peculiarities 1895 o Licensing: Simplified BSD 1896 o Experience: Tested on Windows, Linux and MacOS. 1897 https://www.cs.auckland.ac.nz/~brian/graspy/graspy.pdf 1899 o Contact: https://www.cs.auckland.ac.nz/~brian/graspy/ 1901 4. Security Considerations 1903 A successful attack on negotiation-enabled nodes would be extremely 1904 harmful, as such nodes might end up with a completely undesirable 1905 configuration that would also adversely affect their peers. GRASP 1906 nodes and messages therefore require full protection. As explained 1907 in Section 2.5.1, GRASP MUST run within a secure environment such as 1908 the Autonomic Control Plane [I-D.ietf-anima-autonomic-control-plane], 1909 except for the constrained instances described in Section 2.5.2. 1911 - Authentication 1913 A cryptographically authenticated identity for each device is 1914 needed in an autonomic network. It is not safe to assume that a 1915 large network is physically secured against interference or that 1916 all personnel are trustworthy. Each autonomic node MUST be 1917 capable of proving its identity and authenticating its messages. 1918 GRASP relies on a separate external certificate-based security 1919 mechanism to support authentication, data integrity protection, 1920 and anti-replay protection. 1922 Since GRASP must be deployed in an existing secure environment, 1923 the protocol itself specifies nothing concerning the trust anchor 1924 and certification authority. For example, in the Autonomic 1925 Control Plane [I-D.ietf-anima-autonomic-control-plane], all nodes 1926 can trust each other and the ASAs installed in them. 1928 If GRASP is used temporarily without an external security 1929 mechanism, for example during system bootstrap (Section 2.5.1), 1930 the Session ID (Section 2.7) will act as a nonce to provide 1931 limited protection against third parties injecting responses. A 1932 full analysis of the secure bootstrap process is in 1933 [I-D.ietf-anima-bootstrapping-keyinfra]. 1935 - Authorization and Roles 1937 The GRASP protocol is agnostic about the roles and capabilities of 1938 individual ASAs and about which objectives a particular ASA is 1939 authorized to support. An implementation might support 1940 precautions such as allowing only one ASA in a given node to 1941 modify a given objective, but this may not be appropriate in all 1942 cases. For example, it might be operationally useful to allow an 1943 old and a new version of the same ASA to run simultaneously during 1944 an overlap period. These questions are out of scope for the 1945 present specification. 1947 - Privacy and confidentiality 1949 GRASP is intended for network management purposes involving 1950 network elements, not end hosts. Therefore, no personal 1951 information is expected to be involved in the signaling protocol, 1952 so there should be no direct impact on personal privacy. 1953 Nevertheless, applications that do convey personal information 1954 cannot be excluded. Also, traffic flow paths, VPNs, etc. could be 1955 negotiated, which could be of interest for traffic analysis. 1956 Operators generally want to conceal details of their network 1957 topology and traffic density from outsiders. Therefore, since 1958 insider attacks cannot be excluded in a large network, the 1959 security mechanism for the protocol MUST provide message 1960 confidentiality. This is why Section 2.5.1 requires either an ACP 1961 or an alternative security mechanism. 1963 - Link-local multicast security 1965 GRASP has no reasonable alternative to using link-local multicast 1966 for Discovery or Flood Synchronization messages and these messages 1967 are sent in clear and with no authentication. They are only sent 1968 on interfaces within the autonomic network (see Section 2.1 and 1969 Section 2.5.1). They are however available to on-link 1970 eavesdroppers, and could be forged by on-link attackers. In the 1971 case of Discovery, the Discovery Responses are unicast and will 1972 therefore be protected (Section 2.5.1), and an untrusted forger 1973 will not be able to receive responses. In the case of Flood 1974 Synchronization, an on-link eavesdropper will be able to receive 1975 the flooded objectives but there is no response message to 1976 consider. Some precautions for Flood Synchronization messages are 1977 suggested in Section 2.5.6.2. 1979 - DoS Attack Protection 1981 GRASP discovery partly relies on insecure link-local multicast. 1982 Since routers participating in GRASP sometimes relay discovery 1983 messages from one link to another, this could be a vector for 1984 denial of service attacks. Some mitigations are specified in 1985 Section 2.5.4. However, malicious code installed inside the 1986 Autonomic Control Plane could always launch DoS attacks consisting 1987 of spurious discovery messages, or of spurious discovery 1988 responses. It is important that firewalls prevent any GRASP 1989 messages from entering the domain from an unknown source. 1991 - Security during bootstrap and discovery 1992 A node cannot trust GRASP traffic from other nodes until the 1993 security environment (such as the ACP) has identified the trust 1994 anchor and can authenticate traffic by validating certificates for 1995 other nodes. Also, until it has succesfully enrolled 1996 [I-D.ietf-anima-bootstrapping-keyinfra] a node cannot assume that 1997 other nodes are able to authenticate its own traffic. Therefore, 1998 GRASP discovery during the bootstrap phase for a new device will 1999 inevitably be insecure. Secure synchronization and negotiation 2000 will be impossible until enrollment is complete. Further details 2001 are given in Section 2.5.2. 2003 - Security of discovered locators 2005 When GRASP discovery returns an IP address, it MUST be that of a 2006 node within the secure environment (Section 2.5.1). If it returns 2007 an FQDN or a URI, the ASA that receives it MUST NOT assume that 2008 the target of the locator is within the secure environment. 2010 5. CDDL Specification of GRASP 2012 2013 grasp-message = (message .within message-structure) / noop-message 2015 message-structure = [MESSAGE_TYPE, session-id, ?initiator, 2016 *grasp-option] 2018 MESSAGE_TYPE = 0..255 2019 session-id = 0..4294967295 ;up to 32 bits 2020 grasp-option = any 2022 message /= discovery-message 2023 discovery-message = [M_DISCOVERY, session-id, initiator, objective] 2025 message /= response-message ;response to Discovery 2026 response-message = [M_RESPONSE, session-id, initiator, ttl, 2027 (+locator-option // divert-option), ?objective] 2029 message /= synch-message ;response to Synchronization request 2030 synch-message = [M_SYNCH, session-id, objective] 2032 message /= flood-message 2033 flood-message = [M_FLOOD, session-id, initiator, ttl, 2034 +[objective, (locator-option / [])]] 2036 message /= request-negotiation-message 2037 request-negotiation-message = [M_REQ_NEG, session-id, objective] 2039 message /= request-synchronization-message 2040 request-synchronization-message = [M_REQ_SYN, session-id, objective] 2042 message /= negotiation-message 2043 negotiation-message = [M_NEGOTIATE, session-id, objective] 2045 message /= end-message 2046 end-message = [M_END, session-id, accept-option / decline-option ] 2048 message /= wait-message 2049 wait-message = [M_WAIT, session-id, waiting-time] 2051 message /= invalid-message 2052 invalid-message = [M_INVALID, session-id, ?any] 2054 noop-message = [M_NOOP] 2056 divert-option = [O_DIVERT, +locator-option] 2058 accept-option = [O_ACCEPT] 2060 decline-option = [O_DECLINE, ?reason] 2061 reason = text ;optional UTF-8 error message 2063 waiting-time = 0..4294967295 ; in milliseconds 2064 ttl = 0..4294967295 ; in milliseconds 2066 locator-option /= [O_IPv4_LOCATOR, ipv4-address, 2067 transport-proto, port-number] 2068 ipv4-address = bytes .size 4 2070 locator-option /= [O_IPv6_LOCATOR, ipv6-address, 2071 transport-proto, port-number] 2072 ipv6-address = bytes .size 16 2074 locator-option /= [O_FQDN_LOCATOR, text, transport-proto, port-number] 2076 locator-option /= [O_URI_LOCATOR, text, 2077 transport-proto / null, port-number / null] 2079 transport-proto = IPPROTO_TCP / IPPROTO_UDP 2080 IPPROTO_TCP = 6 2081 IPPROTO_UDP = 17 2082 port-number = 0..65535 2084 initiator = ipv4-address / ipv6-address 2086 objective-flags = uint .bits objective-flag 2087 objective-flag = &( 2088 F_DISC: 0 ; valid for discovery 2089 F_NEG: 1 ; valid for negotiation 2090 F_SYNCH: 2 ; valid for synchronization 2091 F_NEG_DRY: 3 ; negotiation is dry-run 2092 ) 2094 objective = [objective-name, objective-flags, loop-count, ?objective-value] 2096 objective-name = text ;see section "Format of Objective Options" 2098 objective-value = any 2100 loop-count = 0..255 2102 ; Constants for message types and option types 2104 M_NOOP = 0 2105 M_DISCOVERY = 1 2106 M_RESPONSE = 2 2107 M_REQ_NEG = 3 2108 M_REQ_SYN = 4 2109 M_NEGOTIATE = 5 2110 M_END = 6 2111 M_WAIT = 7 2112 M_SYNCH = 8 2113 M_FLOOD = 9 2114 M_INVALID = 99 2116 O_DIVERT = 100 2117 O_ACCEPT = 101 2118 O_DECLINE = 102 2119 O_IPv6_LOCATOR = 103 2120 O_IPv4_LOCATOR = 104 2121 O_FQDN_LOCATOR = 105 2122 O_URI_LOCATOR = 106 2123 2125 6. IANA Considerations 2127 This document defines the GeneRic Autonomic Signaling Protocol 2128 (GRASP). 2130 Section 2.6 explains the following link-local multicast addresses, 2131 which IANA is requested to assign for use by GRASP: 2133 ALL_GRASP_NEIGHBORS multicast address (IPv6): (TBD1). Assigned in 2134 the IPv6 Link-Local Scope Multicast Addresses registry. 2136 ALL_GRASP_NEIGHBORS multicast address (IPv4): (TBD2). Assigned in 2137 the IPv4 Multicast Local Network Control Block. 2139 Section 2.6 explains the following User Port, which IANA is requested 2140 to assign for use by GRASP for both UDP and TCP: 2142 GRASP_LISTEN_PORT: (TBD3) 2143 Service Name: Generic Autonomic Signaling Protocol (GRASP) 2144 Transport Protocols: UDP, TCP 2145 Assignee: iesg@ietf.org 2146 Contact: chair@ietf.org 2147 Description: See Section 2.6 2148 Reference: RFC XXXX (this document) 2150 The IANA is requested to create a GRASP Parameter Registry including 2151 two registry tables. These are the GRASP Messages and Options 2152 Table and the GRASP Objective Names Table. 2154 GRASP Messages and Options Table. The values in this table are names 2155 paired with decimal integers. Future values MUST be assigned using 2156 the Standards Action policy defined by [RFC5226]. The following 2157 initial values are assigned by this document: 2159 M_NOOP = 0 2160 M_DISCOVERY = 1 2161 M_RESPONSE = 2 2162 M_REQ_NEG = 3 2163 M_REQ_SYN = 4 2164 M_NEGOTIATE = 5 2165 M_END = 6 2166 M_WAIT = 7 2167 M_SYNCH = 8 2168 M_FLOOD = 9 2169 M_INVALID = 99 2171 O_DIVERT = 100 2172 O_ACCEPT = 101 2173 O_DECLINE = 102 2174 O_IPv6_LOCATOR = 103 2175 O_IPv4_LOCATOR = 104 2176 O_FQDN_LOCATOR = 105 2177 O_URI_LOCATOR = 106 2179 GRASP Objective Names Table. The values in this table are UTF-8 2180 strings which MUST NOT include a colon (":"), according to 2181 Section 2.10.1. Future values MUST be assigned using the 2182 Specification Required policy defined by [RFC5226]. 2184 To assist expert review of a new objective, the specification should 2185 include a precise description of the format of the new objective, 2186 with sufficient explanation of its semantics to allow independent 2187 implementations. See Section 2.10.3 for more details. If the new 2188 objective is similar in name or purpose to a previously registered 2189 objective, the specification should explain why a new objective is 2190 justified. 2192 The following initial values are assigned by this document: 2194 EX0 2195 EX1 2196 EX2 2197 EX3 2198 EX4 2199 EX5 2200 EX6 2201 EX7 2202 EX8 2203 EX9 2205 7. Acknowledgements 2207 A major contribution to the original version of this document was 2208 made by Sheng Jiang. Significant early review inputs were received 2209 from Toerless Eckert, Joel Halpern, Barry Leiba, Charles E. Perkins, 2210 and Michael Richardson. William Atwood provided important assistance 2211 in debugging a prototype implementation. 2213 Valuable comments were received from Michael Behringer, Jeferson 2214 Campos Nobre, Laurent Ciavaglia, Zongpeng Du, Yu Fu, Joel Jaeggli, 2215 Zhenbin Li, Dimitri Papadimitriou, Pierre Peloso, Reshad Rahman, 2216 Markus Stenberg, Martin Stiemerling, Rene Struik, Martin Thomson, 2217 Dacheng Zhang, and participants in the NMRG research group, the ANIMA 2218 working group, and the IESG. 2220 8. References 2222 8.1. Normative References 2224 [I-D.greevenbosch-appsawg-cbor-cddl] 2225 Birkholz, H., Vigano, C., and C. Bormann, "CBOR data 2226 definition language (CDDL): a notational convention to 2227 express CBOR data structures", draft-greevenbosch-appsawg- 2228 cbor-cddl-10 (work in progress), March 2017. 2230 [I-D.ietf-anima-autonomic-control-plane] 2231 Behringer, M., Eckert, T., and S. Bjarnason, "An Autonomic 2232 Control Plane", draft-ietf-anima-autonomic-control- 2233 plane-06 (work in progress), March 2017. 2235 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 2236 Requirement Levels", BCP 14, RFC 2119, 2237 DOI 10.17487/RFC2119, March 1997, 2238 . 2240 [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO 2241 10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November 2242 2003, . 2244 [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform 2245 Resource Identifier (URI): Generic Syntax", STD 66, 2246 RFC 3986, DOI 10.17487/RFC3986, January 2005, 2247 . 2249 [RFC4086] Eastlake 3rd, D., Schiller, J., and S. Crocker, 2250 "Randomness Requirements for Security", BCP 106, RFC 4086, 2251 DOI 10.17487/RFC4086, June 2005, 2252 . 2254 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 2255 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 2256 October 2013, . 2258 [RFC7217] Gont, F., "A Method for Generating Semantically Opaque 2259 Interface Identifiers with IPv6 Stateless Address 2260 Autoconfiguration (SLAAC)", RFC 7217, 2261 DOI 10.17487/RFC7217, April 2014, 2262 . 2264 [RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage 2265 Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, 2266 March 2017, . 2268 8.2. Informative References 2270 [I-D.carpenter-anima-asa-guidelines] 2271 Carpenter, B. and S. Jiang, "Guidelines for Autonomic 2272 Service Agents", draft-carpenter-anima-asa-guidelines-01 2273 (work in progress), January 2017. 2275 [I-D.chaparadza-intarea-igcp] 2276 Behringer, M., Chaparadza, R., Petre, R., Li, X., and H. 2277 Mahkonen, "IP based Generic Control Protocol (IGCP)", 2278 draft-chaparadza-intarea-igcp-00 (work in progress), July 2279 2011. 2281 [I-D.ietf-anima-bootstrapping-keyinfra] 2282 Pritikin, M., Richardson, M., Behringer, M., Bjarnason, 2283 S., and K. Watsen, "Bootstrapping Remote Secure Key 2284 Infrastructures (BRSKI)", draft-ietf-anima-bootstrapping- 2285 keyinfra-06 (work in progress), May 2017. 2287 [I-D.ietf-anima-reference-model] 2288 Behringer, M., Carpenter, B., Eckert, T., Ciavaglia, L., 2289 Pierre, P., Liu, B., Nobre, J., and J. Strassner, "A 2290 Reference Model for Autonomic Networking", draft-ietf- 2291 anima-reference-model-03 (work in progress), March 2017. 2293 [I-D.ietf-anima-stable-connectivity] 2294 Eckert, T. and M. Behringer, "Using Autonomic Control 2295 Plane for Stable Connectivity of Network OAM", draft-ietf- 2296 anima-stable-connectivity-02 (work in progress), February 2297 2017. 2299 [I-D.liang-iana-pen] 2300 Liang, P., Melnikov, A., and D. Conrad, "Private 2301 Enterprise Number (PEN) practices and Internet Assigned 2302 Numbers Authority (IANA) registration considerations", 2303 draft-liang-iana-pen-06 (work in progress), July 2015. 2305 [I-D.liu-anima-grasp-api] 2306 Carpenter, B., Liu, B., Wang, W., and X. Gong, "Generic 2307 Autonomic Signaling Protocol Application Program Interface 2308 (GRASP API)", draft-liu-anima-grasp-api-03 (work in 2309 progress), February 2017. 2311 [I-D.stenberg-anima-adncp] 2312 Stenberg, M., "Autonomic Distributed Node Consensus 2313 Protocol", draft-stenberg-anima-adncp-00 (work in 2314 progress), March 2015. 2316 [RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S. 2317 Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 2318 Functional Specification", RFC 2205, DOI 10.17487/RFC2205, 2319 September 1997, . 2321 [RFC2334] Luciani, J., Armitage, G., Halpern, J., and N. Doraswamy, 2322 "Server Cache Synchronization Protocol (SCSP)", RFC 2334, 2323 DOI 10.17487/RFC2334, April 1998, 2324 . 2326 [RFC2608] Guttman, E., Perkins, C., Veizades, J., and M. Day, 2327 "Service Location Protocol, Version 2", RFC 2608, 2328 DOI 10.17487/RFC2608, June 1999, 2329 . 2331 [RFC2865] Rigney, C., Willens, S., Rubens, A., and W. Simpson, 2332 "Remote Authentication Dial In User Service (RADIUS)", 2333 RFC 2865, DOI 10.17487/RFC2865, June 2000, 2334 . 2336 [RFC3315] Droms, R., Ed., Bound, J., Volz, B., Lemon, T., Perkins, 2337 C., and M. Carney, "Dynamic Host Configuration Protocol 2338 for IPv6 (DHCPv6)", RFC 3315, DOI 10.17487/RFC3315, July 2339 2003, . 2341 [RFC3416] Presuhn, R., Ed., "Version 2 of the Protocol Operations 2342 for the Simple Network Management Protocol (SNMP)", 2343 STD 62, RFC 3416, DOI 10.17487/RFC3416, December 2002, 2344 . 2346 [RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W. 2347 Stevens, "Basic Socket Interface Extensions for IPv6", 2348 RFC 3493, DOI 10.17487/RFC3493, February 2003, 2349 . 2351 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 2352 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, 2353 DOI 10.17487/RFC4861, September 2007, 2354 . 2356 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 2357 IANA Considerations Section in RFCs", BCP 26, RFC 5226, 2358 DOI 10.17487/RFC5226, May 2008, 2359 . 2361 [RFC5971] Schulzrinne, H. and R. Hancock, "GIST: General Internet 2362 Signalling Transport", RFC 5971, DOI 10.17487/RFC5971, 2363 October 2010, . 2365 [RFC6206] Levis, P., Clausen, T., Hui, J., Gnawali, O., and J. Ko, 2366 "The Trickle Algorithm", RFC 6206, DOI 10.17487/RFC6206, 2367 March 2011, . 2369 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., 2370 and A. Bierman, Ed., "Network Configuration Protocol 2371 (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, 2372 . 2374 [RFC6733] Fajardo, V., Ed., Arkko, J., Loughney, J., and G. Zorn, 2375 Ed., "Diameter Base Protocol", RFC 6733, 2376 DOI 10.17487/RFC6733, October 2012, 2377 . 2379 [RFC6762] Cheshire, S. and M. Krochmal, "Multicast DNS", RFC 6762, 2380 DOI 10.17487/RFC6762, February 2013, 2381 . 2383 [RFC6763] Cheshire, S. and M. Krochmal, "DNS-Based Service 2384 Discovery", RFC 6763, DOI 10.17487/RFC6763, February 2013, 2385 . 2387 [RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and 2388 P. Selkirk, "Port Control Protocol (PCP)", RFC 6887, 2389 DOI 10.17487/RFC6887, April 2013, 2390 . 2392 [RFC7558] Lynn, K., Cheshire, S., Blanchet, M., and D. Migault, 2393 "Requirements for Scalable DNS-Based Service Discovery 2394 (DNS-SD) / Multicast DNS (mDNS) Extensions", RFC 7558, 2395 DOI 10.17487/RFC7558, July 2015, 2396 . 2398 [RFC7564] Saint-Andre, P. and M. Blanchet, "PRECIS Framework: 2399 Preparation, Enforcement, and Comparison of 2400 Internationalized Strings in Application Protocols", 2401 RFC 7564, DOI 10.17487/RFC7564, May 2015, 2402 . 2404 [RFC7575] Behringer, M., Pritikin, M., Bjarnason, S., Clemm, A., 2405 Carpenter, B., Jiang, S., and L. Ciavaglia, "Autonomic 2406 Networking: Definitions and Design Goals", RFC 7575, 2407 DOI 10.17487/RFC7575, June 2015, 2408 . 2410 [RFC7576] Jiang, S., Carpenter, B., and M. Behringer, "General Gap 2411 Analysis for Autonomic Networking", RFC 7576, 2412 DOI 10.17487/RFC7576, June 2015, 2413 . 2415 [RFC7787] Stenberg, M. and S. Barth, "Distributed Node Consensus 2416 Protocol", RFC 7787, DOI 10.17487/RFC7787, April 2016, 2417 . 2419 [RFC7788] Stenberg, M., Barth, S., and P. Pfister, "Home Networking 2420 Control Protocol", RFC 7788, DOI 10.17487/RFC7788, April 2421 2016, . 2423 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF 2424 Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, 2425 . 2427 Appendix A. Open Issues [RFC Editor: This section should be empty. 2428 Please remove] 2430 o 68. (Placeholder) 2432 Appendix B. Closed Issues [RFC Editor: Please remove] 2434 o 1. UDP vs TCP: For now, this specification suggests UDP and TCP 2435 as message transport mechanisms. This is not clarified yet. UDP 2436 is good for short conversations, is necessary for multicast 2437 discovery, and generally fits the discovery and divert scenarios 2438 well. However, it will cause problems with large messages. TCP 2439 is good for stable and long sessions, with a little bit of time 2440 consumption during the session establishment stage. If messages 2441 exceed a reasonable MTU, a TCP mode will be required in any case. 2442 This question may be affected by the security discussion. 2444 RESOLVED by specifying UDP for short message and TCP for longer 2445 one. 2447 o 2. DTLS or TLS vs built-in security mechanism. For now, this 2448 specification has chosen a PKI based built-in security mechanism 2449 based on asymmetric cryptography. However, (D)TLS might be chosen 2450 as security solution to avoid duplication of effort. It also 2451 allows essentially similar security for short messages over UDP 2452 and longer ones over TCP. The implementation trade-offs are 2453 different. The current approach requires expensive asymmetric 2454 cryptographic calculations for every message. (D)TLS has startup 2455 overheads but cheaper crypto per message. DTLS is less mature 2456 than TLS. 2458 RESOLVED by specifying external security (ACP or (D)TLS). 2460 o The following open issues applied only if the original security 2461 model was retained: 2463 * 2.1. For replay protection, GRASP currently requires every 2464 participant to have an NTP-synchronized clock. Is this OK for 2465 low-end devices, and how does it work during device 2466 bootstrapping? We could take the Timestamp out of signature 2467 option, to become an independent and OPTIONAL (or RECOMMENDED) 2468 option. 2470 * 2.2. The Signature Option states that this option could be any 2471 place in a message. Wouldn't it be better to specify a 2472 position (such as the end)? That would be much simpler to 2473 implement. 2475 RESOLVED by changing security model. 2477 o 3. DoS Attack Protection needs work. 2479 RESOLVED by adding text. 2481 o 4. Should we consider preferring a text-based approach to 2482 discovery (after the initial discovery needed for bootstrapping)? 2483 This could be a complementary mechanism for multicast based 2484 discovery, especially for a very large autonomic network. 2485 Centralized registration could be automatically deployed 2486 incrementally. At the very first stage, the repository could be 2487 empty; then it could be filled in by the objectives discovered by 2488 different devices (for example using Dynamic DNS Update). The 2489 more records are stored in the repository, the less the multicast- 2490 based discovery is needed. However, if we adopt such a mechanism, 2491 there would be challenges: stateful solution, and security. 2493 RESOLVED for now by adding optional use of DNS-SD by ASAs. 2494 Subsequently removed by editors as irrelevant to GRASP istelf. 2496 o 5. Need to expand description of the minimum requirements for the 2497 specification of an individual discovery, synchronization or 2498 negotiation objective. 2500 RESOLVED for now by extra wording. 2502 o 6. Use case and protocol walkthrough. A description of how a 2503 node starts up, performs discovery, and conducts negotiation and 2504 synchronisation for a sample use case would help readers to 2505 understand the applicability of this specification. Maybe it 2506 should be an artificial use case or maybe a simple real one, based 2507 on a conceptual API. However, the authors have not yet decided 2508 whether to have a separate document or have it in the protocol 2509 document. 2511 RESOLVED: recommend a separate document. 2513 o 7. Cross-check against other ANIMA WG documents for consistency 2514 and gaps. 2516 RESOLVED: Satisfied by WGLC. 2518 o 8. Consideration of ADNCP proposal. 2520 RESOLVED by adding optional use of DNCP for flooding-type 2521 synchronization. 2523 o 9. Clarify how a GDNP instance knows whether it is running inside 2524 the ACP. (Sheng) 2526 RESOLVED by improved text. 2528 o 10. Clarify how a non-ACP GDNP instance initiates (D)TLS. 2529 (Sheng) 2531 RESOLVED by improved text and declaring DTLS out of scope for this 2532 draft. 2534 o 11. Clarify how UDP/TCP choice is made. (Sheng) [Like DNS? - 2535 Brian] 2537 RESOLVED by improved text. 2539 o 12. Justify that IP address within ACP or (D)TLS environment is 2540 sufficient to prove AN identity; or explain how Device Identity 2541 Option is used. (Sheng) 2543 RESOLVED for now: we assume that all ASAs in a device are trusted 2544 as soon as the device is trusted, so they share credentials. In 2545 that case the Device Identity Option is useless. This needs to be 2546 reviewed later. 2548 o 13. Emphasise that negotiation/synchronization are independent 2549 from discovery, although the rapid discovery mode includes the 2550 first step of a negotiation/synchronization. (Sheng) 2552 RESOLVED by improved text. 2554 o 14. Do we need an unsolicited flooding mechanism for discovery 2555 (for discovery results that everyone needs), to reduce scaling 2556 impact of flooding discovery messages? (Toerless) 2558 RESOLVED: Yes, added to requirements and solution. 2560 o 15. Do we need flag bits in Objective Options to distinguish 2561 distinguish Synchronization and Negotiation "Request" or rapid 2562 mode "Discovery" messages? (Bing) 2564 RESOLVED: yes, work on the API showed that these flags are 2565 essential. 2567 o 16. (Related to issue 14). Should we revive the "unsolicited 2568 Response" for flooding synchronisation data? This has to be done 2569 carefully due to the well-known issues with flooding, but it could 2570 be useful, e.g. for Intent distribution, where DNCP doesn't seem 2571 applicable. 2573 RESOLVED: Yes, see #14. 2575 o 17. Ensure that the discovery mechanism is completely proof 2576 against loops and protected against duplicate responses. 2578 RESOLVED: Added loop count mechanism. 2580 o 18. Discuss the handling of multiple valid discovery responses. 2582 RESOLVED: Stated that the choice must be available to the ASA but 2583 GRASP implementation should pick a default. 2585 o 19. Should we use a text-oriented format such as JSON/CBOR 2586 instead of native binary TLV format? 2588 RESOLVED: Yes, changed to CBOR. 2590 o 20. Is the Divert option needed? If a discovery response 2591 provides a valid IP address or FQDN, the recipient doesn't gain 2592 any extra knowledge from the Divert. On the other hand, the 2593 presence of Divert informs the receiver that the target is off- 2594 link, which might be useful sometimes. 2596 RESOLVED: Decided to keep Divert option. 2598 o 21. Rename the protocol as GRASP (GeneRic Autonomic Signaling 2599 Protocol)? 2601 RESOLVED: Yes, name changed. 2603 o 22. Does discovery mechanism scale robustly as needed? Need hop 2604 limit on relaying? 2606 RESOLVED: Added hop limit. 2608 o 23. Need more details on TTL for caching discovery responses. 2610 RESOLVED: Done. 2612 o 24. Do we need "fast withdrawal" of discovery responses? 2614 RESOLVED: This doesn't seem necessary. If an ASA exits or stops 2615 supporting a given objective, peers will fail to start future 2616 sessions and will simply repeat discovery. 2618 o 25. Does GDNP discovery meet the needs of multi-hop DNS-SD? 2620 RESOLVED: Decided not to consider this further as a GRASP protocol 2621 issue. GRASP objectives could embed DNS-SD formats if needed. 2623 o 26. Add a URL type to the locator options (for security bootstrap 2624 etc.) 2626 RESOLVED: Done, later renamed as URI. 2628 o 27. Security of Flood multicasts (Section 2.5.6.2). 2630 RESOLVED: added text. 2632 o 28. Does ACP support secure link-local multicast? 2634 RESOLVED by new text in the Security Considerations. 2636 o 29. PEN is used to distinguish vendor options. Would it be 2637 better to use a domain name? Anything unique will do. 2639 RESOLVED: Simplified this by removing PEN field and changing 2640 naming rules for objectives. 2642 o 30. Does response to discovery require randomized delays to 2643 mitigate amplification attacks? 2645 RESOLVED: WG feedback is that it's unnecessary. 2647 o 31. We have specified repeats for failed discovery etc. Is that 2648 sufficient to deal with sleeping nodes? 2650 RESOLVED: WG feedback is that it's unnecessary to say more. 2652 o 32. We have one-to-one synchronization and flooding 2653 synchronization. Do we also need selective flooding to a subset 2654 of nodes? 2655 RESOLVED: This will be discussed as a protocol extension in a 2656 separate draft (draft-liu-anima-grasp-distribution). 2658 o 33. Clarify if/when discovery needs to be repeated. 2660 RESOLVED: Done. 2662 o 34. Clarify what is mandatory for running in ACP, expand 2663 discussion of security boundary when running with no ACP - might 2664 rely on the local PKI infrastructure. 2666 RESOLVED: Done. 2668 o 35. State that role-based authorization of ASAs is out of scope 2669 for GRASP. GRASP doesn't recognize/handle any "roles". 2671 RESOLVED: Done. 2673 o 36. Reconsider CBOR definition for PEN syntax. ( objective-name 2674 = text / [pen, text] ; pen = uint ) 2676 RESOLVED: See issue 29. 2678 o 37. Are URI locators really needed? 2680 RESOLVED: Yes, e.g. for security bootstrap discovery, but added 2681 note that addresses are the normal case (same for FQDN locators). 2683 o 38. Is Session ID sufficient to identify relayed responses? 2684 Isn't the originator's address needed too? 2686 RESOLVED: Yes, this is needed for multicast messages and their 2687 responses. 2689 o 39. Clarify that a node will contain one GRASP instance 2690 supporting multiple ASAs. 2692 RESOLVED: Done. 2694 o 40. Add a "reason" code to the DECLINE option? 2696 RESOLVED: Done. 2698 o 41. What happens if an ASA cannot conveniently use one of the 2699 GRASP mechanisms? Do we (a) add a message type to GRASP, or (b) 2700 simply pass the discovery results to the ASA so that it can open 2701 its own socket? 2702 RESOLVED: Both would be possible, but (b) is preferred. 2704 o 42. Do we need a feature whereby an ASA can bypass the ACP and 2705 use the data plane for efficiency/throughput? This would require 2706 discovery to return non-ACP addresses and would evade ACP 2707 security. 2709 RESOLVED: This is considered out of scope for GRASP, but a comment 2710 has been added in security considerations. 2712 o 43. Rapid mode synchronization and negotiation is currently 2713 limited to a single objective for simplicity of design and 2714 implementation. A future consideration is to allow multiple 2715 objectives in rapid mode for greater efficiency. 2717 RESOLVED: This is considered out of scope for this version. 2719 o 44. In requirement T9, the words that encryption "may not be 2720 required in all deployments" were removed. Is that OK?. 2722 RESOLVED: No objections. 2724 o 45. Device Identity Option is unused. Can we remove it 2725 completely?. 2727 RESOLVED: No objections. Done. 2729 o 46. The 'initiator' field in DISCOVER, RESPONSE and FLOOD 2730 messages is intended to assist in loop prevention. However, we 2731 also have the loop count for that. Also, if we create a new 2732 Session ID each time a DISCOVER or FLOOD is relayed, that ID can 2733 be disambiguated by recipients. It would be simpler to remove the 2734 initiator from the messages, making parsing more uniform. Is that 2735 OK? 2737 RESOLVED: Yes. Done. 2739 o 47. REQUEST is a dual purpose message (request negotiation or 2740 request synchronization). Would it be better to split this into 2741 two different messages (and adjust various message names 2742 accordingly)? 2744 RESOLVED: Yes. Done. 2746 o 48. Should the Appendix "Capability Analysis of Current 2747 Protocols" be deleted before RFC publication? 2749 RESOLVED: No (per WG meeting at IETF 96). 2751 o 49. Section 2.5.1 Should say more about signaling between two 2752 autonomic networks/domains. 2754 RESOLVED: Description of separate GRASP instance added. 2756 o 50. Is Rapid mode limited to on-link only? What happens if first 2757 discovery responder does not support Rapid Mode? Section 2.5.5, 2758 Section 2.5.6) 2760 RESOLVED: Not limited to on-link. First responder wins. 2762 o 51. Should flooded objectives have a time-to-live before they are 2763 deleted from the flood cache? And should they be tagged in the 2764 cache with their source locator? 2766 RESOLVED: TTL added to Flood (and Discovery Response) messages. 2767 Cached flooded objectives must be tagged with their originating 2768 ASA locator, and multiple copies must be kept if necessary. 2770 o 52. Describe in detail what is allowed and disallowed in an 2771 insecure instance of GRASP. 2773 RESOLVED: Done. 2775 o 53. Tune IANA Considerations to support early assignment request. 2777 o 54. Is there a highly unlikely race condition if two peers 2778 simultaneously choose the same Session ID and send each other 2779 simultaneous M_REQ_NEG messages? 2781 RESOLVED: Yes. Enhanced text on Session ID generation, and added 2782 precaution when receiving a Request message. 2784 o 55. Could discovery be performed over TCP? 2786 RESOLVED: Unicast discovery added as an option. 2788 o 56. Change Session-ID to 32 bits? 2790 RESOLVED: Done. 2792 o 57. Add M_INVALID message? 2794 RESOLVED: Done. 2796 o 58. Maximum message size? 2797 RESOLVED by specifying default maximum message size (2048 bytes). 2799 o 59. Add F_NEG_DRY flag to specify a "dry run" objective?. 2801 RESOLVED: Done. 2803 o 60. Change M_FLOOD syntax to associate a locator with each 2804 objective? 2806 RESOLVED: Done. 2808 o 61. Is the SONN constrained instance really needed? 2810 RESOLVED: Retained but only as an option. 2812 o 62. Is it helpful to tag descriptive text with message names 2813 (M_DISCOVER etc.)? 2815 RESOLVED: Yes, done in various parts of the text. 2817 o 63. Should encryption be MUST instead of SHOULD in Section 2.5.1 2818 and Section 2.5.2.1? 2820 RESOLVED: Yes, MUST implement in both cases. 2822 o 64. Should more security text be moved from the main text into 2823 the Security Considerations? 2825 RESOLVED: No, on AD advice. 2827 o 65. Do we need to formally restrict Unicode characters allowed in 2828 objective names? 2830 RESOLVED: No, but need to point to guidance from PRECIS WG. 2832 o 66. Split requirements into separate document? 2834 RESOLVED: No, on AD advice. 2836 o 67. Remove normative dependency on draft-greevenbosch-appsawg- 2837 cbor-cddl? 2839 RESOLVED: No, on AD advice. In worst case, fix at AUTH48. 2841 Appendix C. Change log [RFC Editor: Please remove] 2843 draft-ietf-anima-grasp-13, 2017-06-06: 2845 Updates following additional IESG comments: 2847 Removed all mention of TLS, including SONN, since it was under- 2848 specified. 2850 Clarified other text about trust and security model. 2852 Banned Rapid Mode when multicast is insecure. 2854 Explained use of M_INVALID to support extensibility 2856 Corrected details on discovery cache TTL and discovery timeout. 2858 Improved description of multicast UDP w.r.t. RFC8085. 2860 Clarified when transport connections are opened or closed. 2862 Noted that IPPROTO values come from the Protocol Numbers registry 2864 Protocol change: Added protocol and port numbers to URI locator. 2866 Removed inaccurate text about routing protocols 2868 Moved Requirements section to an Appendix. 2870 Other editorial and technical clarifications. 2872 draft-ietf-anima-grasp-12, 2017-05-19: 2874 Updates following IESG comments: 2876 Clarified that GRASP runs in a single addressing realm 2878 Improved wording about FQDN resolution, clarified that URI usage is 2879 out of scope. 2881 Clarified description of negotiation timeout. 2883 Noted that 'dry run' semantics are ASA-dependent 2885 Made the ACP a normative reference 2887 Clarified that LL multicasts are limited to GRASP interfaces 2888 Unicast UDP moved out of scope 2890 Editorial clarifications 2892 draft-ietf-anima-grasp-11, 2017-03-30: 2894 Updates following IETF 98 discussion: 2896 Encryption changed to a MUST implement. 2898 Pointed to guidance on UTF-8 names. 2900 draft-ietf-anima-grasp-10, 2017-03-10: 2902 Updates following IETF Last call: 2904 Protocol change: Specify that an objective with no initial value 2905 should have its value field set to CBOR 'null'. 2907 Protocol change: Specify behavior on receiving unrecognized message 2908 type. 2910 Noted that UTF-8 names are matched byte-for-byte. 2912 Added brief guidance for Expert Reviewer of new generic objectives. 2914 Numerous editorial improvements and clarifications and minor text 2915 rearrangements, none intended to change the meaning. 2917 draft-ietf-anima-grasp-09, 2016-12-15: 2919 Protocol change: Add F_NEG_DRY flag to specify a "dry run" objective. 2921 Protocol change: Change M_FLOOD syntax to associate a locator with 2922 each objective. 2924 Concentrated mentions of TLS in one section, with all details out of 2925 scope. 2927 Clarified text around constrained instances of GRASP. 2929 Strengthened text restricting LL addresses in locator options. 2931 Clarified description of rapid mode processsing. 2933 Specified that cached discovery results should not be returned on the 2934 same interface where they were learned. 2936 Shortened text in "High Level Design Choices" 2938 Dropped the word 'kernel' to avoid confusion with o/s kernel mode. 2940 Editorial improvements and clarifications. 2942 draft-ietf-anima-grasp-08, 2016-10-30: 2944 Protocol change: Added M_INVALID message. 2946 Protocol change: Increased Session ID space to 32 bits. 2948 Enhanced rules to avoid Session ID clashes. 2950 Corrected and completed description of timeouts for Request messages. 2952 Improved wording about exponential backoff and DoS. 2954 Clarified that discovery relaying is not done by limited security 2955 instances. 2957 Corrected and expanded explanation of port used for Discovery 2958 Response. 2960 Noted that Discovery message could be sent unicast in special cases. 2962 Added paragraph on extensibility. 2964 Specified default maximum message size. 2966 Added Appendix for sample messages. 2968 Added short protocol overview. 2970 Editorial fixes, including minor re-ordering for readability. 2972 draft-ietf-anima-grasp-07, 2016-09-13: 2974 Protocol change: Added TTL field to Flood message (issue 51). 2976 Protocol change: Added Locator option to Flood message (issue 51). 2978 Protocol change: Added TTL field to Discovery Response message 2979 (corrollary to issue 51). 2981 Clarified details of rapid mode (issues 43 and 50). 2983 Description of inter-domain GRASP instance added (issue 49). 2985 Description of limited security GRASP instances added (issue 52). 2987 Strengthened advice to use TCP rather than UDP. 2989 Updated IANA considerations and text about well-known port usage 2990 (issue 53). 2992 Amended text about ASA authorization and roles to allow for 2993 overlapping ASAs. 2995 Added text recommending that Flood should be repeated periodically. 2997 Editorial fixes. 2999 draft-ietf-anima-grasp-06, 2016-06-27: 3001 Added text on discovery cache timeouts. 3003 Noted that ASAs that are only initiators do not need to respond to 3004 discovery message. 3006 Added text on unexpected address changes. 3008 Added text on robust implementation. 3010 Clarifications and editorial fixes for numerous review comments 3012 Added open issues for some review comments. 3014 draft-ietf-anima-grasp-05, 2016-05-13: 3016 Noted in requirement T1 that it should be possible to implement ASAs 3017 independently as user space programs. 3019 Protocol change: Added protocol number and port to discovery 3020 response. Updated protocol description, CDDL and IANA considerations 3021 accordingly. 3023 Clarified that discovery and flood multicasts are handled by the 3024 GRASP core, not directly by ASAs. 3026 Clarified that a node may discover an objective without supporting it 3027 for synchronization or negotiation. 3029 Added Implementation Status section. 3031 Added reference to SCSP. 3033 Editorial fixes. 3035 draft-ietf-anima-grasp-04, 2016-03-11: 3037 Protocol change: Restored initiator field in certain messages and 3038 adjusted relaying rules to provide complete loop detection. 3040 Updated IANA Considerations. 3042 draft-ietf-anima-grasp-03, 2016-02-24: 3044 Protocol change: Removed initiator field from certain messages and 3045 adjusted relaying requirement to simplify loop detection. Also 3046 clarified narrative explanation of discovery relaying. 3048 Protocol change: Split Request message into two (Request Negotiation 3049 and Request Synchronization) and updated other message names for 3050 clarity. 3052 Protocol change: Dropped unused Device ID option. 3054 Further clarified text on transport layer usage. 3056 New text about multicast insecurity in Security Considerations. 3058 Various other clarifications and editorial fixes, including moving 3059 some material to Appendix. 3061 draft-ietf-anima-grasp-02, 2016-01-13: 3063 Resolved numerous issues according to WG discussions. 3065 Renumbered requirements, added D9. 3067 Protocol change: only allow one objective in rapid mode. 3069 Protocol change: added optional error string to DECLINE option. 3071 Protocol change: removed statement that seemed to say that a Request 3072 not preceded by a Discovery should cause a Discovery response. That 3073 made no sense, because there is no way the initiator would know where 3074 to send the Request. 3076 Protocol change: Removed PEN option from vendor objectives, changed 3077 naming rule accordingly. 3079 Protocol change: Added FLOOD message to simplify coding. 3081 Protocol change: Added SYNCH message to simplify coding. 3083 Protocol change: Added initiator id to DISCOVER, RESPONSE and FLOOD 3084 messages. But also allowed the relay process for DISCOVER and FLOOD 3085 to regenerate a Session ID. 3087 Protocol change: Require that discovered addresses must be global 3088 (except during bootstrap). 3090 Protocol change: Receiver of REQUEST message must close socket if no 3091 ASA is listening for the objective. 3093 Protocol change: Simplified Waiting message. 3095 Protocol change: Added No Operation message. 3097 Renamed URL locator type as URI locator type. 3099 Updated CDDL definition. 3101 Various other clarifications and editorial fixes. 3103 draft-ietf-anima-grasp-01, 2015-10-09: 3105 Updated requirements after list discussion. 3107 Changed from TLV to CBOR format - many detailed changes, added co- 3108 author. 3110 Tightened up loop count and timeouts for various cases. 3112 Noted that GRASP does not provide transactional integrity. 3114 Various other clarifications and editorial fixes. 3116 draft-ietf-anima-grasp-00, 2015-08-14: 3118 File name and protocol name changed following WG adoption. 3120 Added URL locator type. 3122 draft-carpenter-anima-gdn-protocol-04, 2015-06-21: 3124 Tuned wording around hierarchical structure. 3126 Changed "device" to "ASA" in many places. 3128 Reformulated requirements to be clear that the ASA is the main 3129 customer for signaling. 3131 Added requirement for flooding unsolicited synch, and added it to 3132 protocol spec. Recognized DNCP as alternative for flooding synch 3133 data. 3135 Requirements clarified, expanded and rearranged following design team 3136 discussion. 3138 Clarified that GDNP discovery must not be a prerequisite for GDNP 3139 negotiation or synchronization (resolved issue 13). 3141 Specified flag bits for objective options (resolved issue 15). 3143 Clarified usage of ACP vs TLS/DTLS and TCP vs UDP (resolved issues 3144 9,10,11). 3146 Updated DNCP description from latest DNCP draft. 3148 Editorial improvements. 3150 draft-carpenter-anima-gdn-protocol-03, 2015-04-20: 3152 Removed intrinsic security, required external security 3154 Format changes to allow DNCP co-existence 3156 Recognized DNS-SD as alternative discovery method. 3158 Editorial improvements 3160 draft-carpenter-anima-gdn-protocol-02, 2015-02-19: 3162 Tuned requirements to clarify scope, 3164 Clarified relationship between types of objective, 3166 Clarified that objectives may be simple values or complex data 3167 structures, 3169 Improved description of objective options, 3171 Added loop-avoidance mechanisms (loop count and default timeout, 3172 limitations on discovery relaying and on unsolicited responses), 3174 Allow multiple discovery objectives in one response, 3175 Provided for missing or multiple discovery responses, 3177 Indicated how modes such as "dry run" should be supported, 3179 Minor editorial and technical corrections and clarifications, 3181 Reorganized future work list. 3183 draft-carpenter-anima-gdn-protocol-01, restructured the logical flow 3184 of the document, updated to describe synchronization completely, add 3185 unsolicited responses, numerous corrections and clarifications, 3186 expanded future work list, 2015-01-06. 3188 draft-carpenter-anima-gdn-protocol-00, combination of draft-jiang- 3189 config-negotiation-ps-03 and draft-jiang-config-negotiation-protocol- 3190 02, 2014-10-08. 3192 Appendix D. Example Message Formats 3194 For readers unfamiliar with CBOR, this appendix shows a number of 3195 example GRASP messages conforming to the CDDL syntax given in 3196 Section 5. Each message is shown three times in the following 3197 formats: 3199 1. CBOR diagnostic notation. 3201 2. Similar, but showing the names of the constants. (Details of the 3202 flag bit encoding are omitted.) 3204 3. Hexadecimal version of the CBOR wire format. 3206 Long lines are split for display purposes only. 3208 D.1. Discovery Example 3210 The initiator (2001:db8:f000:baaa:28cc:dc4c:9703:6781) multicasts a 3211 discovery message looking for objective EX1: 3213 [1, 13948744, h'20010db8f000baaa28ccdc4c97036781', ["EX1", 5, 2, 0]] 3214 [M_DISCOVERY, 13948744, h'20010db8f000baaa28ccdc4c97036781', 3215 ["EX1", F_SYNCH_bits, 2, 0]] 3216 h'84011a00d4d7485020010db8f000baaa28ccdc4c970367818463455831050200' 3218 A peer (2001:0db8:f000:baaa:f000:baaa:f000:baaa) responds with a 3219 locator: 3221 [2, 13948744, h'20010db8f000baaa28ccdc4c97036781', 60000, 3222 [103, h'20010db8f000baaaf000baaaf000baaa', 6, 49443]] 3223 [M_RESPONSE, 13948744, h'20010db8f000baaa28ccdc4c97036781', 60000, 3224 [O_IPv6_LOCATOR, h'20010db8f000baaaf000baaaf000baaa', 3225 IPPROTO_TCP, 49443]] 3226 h'85021a00d4d7485020010db8f000baaa28ccdc4c9703678119ea6084186750 3227 20010db8f000baaaf000baaaf000baaa0619c123' 3229 D.2. Flood Example 3231 The initiator multicasts a flood message. The single objective has a 3232 null locator. There is no response: 3234 [9, 3504974, h'20010db8f000baaa28ccdc4c97036781', 10000, 3235 [["EX1", 5, 2, ["Example 1 value=", 100]],[] ] ] 3236 [M_FLOOD, 3504974, h'20010db8f000baaa28ccdc4c97036781', 10000, 3237 [["EX1", F_SYNCH_bits, 2, ["Example 1 value=", 100]],[] ] ] 3238 h'86091a00357b4e5020010db8f000baaa28ccdc4c97036781192710 3239 828463455831050282704578616d706c6520312076616c75653d186480' 3241 D.3. Synchronization Example 3243 Following successful discovery of objective EX2, the initiator 3244 unicasts a request: 3246 [4, 4038926, ["EX2", 5, 5, 0]] 3247 [M_REQ_SYN, 4038926, ["EX2", F_SYNCH_bits, 5, 0]] 3248 h'83041a003da10e8463455832050500' 3250 The peer responds with a value: 3252 [8, 4038926, ["EX2", 5, 5, ["Example 2 value=", 200]]] 3253 [M_SYNCH, 4038926, ["EX2", F_SYNCH_bits, 5, ["Example 2 value=", 200]]] 3254 h'83081a003da10e8463455832050582704578616d706c6520322076616c75653d18c8' 3256 D.4. Simple Negotiation Example 3258 Following successful discovery of objective EX3, the initiator 3259 unicasts a request: 3261 [3, 802813, ["EX3", 3, 6, ["NZD", 47]]] 3262 [M_REQ_NEG, 802813, ["EX3", F_NEG_bits, 6, ["NZD", 47]]] 3263 h'83031a000c3ffd8463455833030682634e5a44182f' 3265 The peer responds with immediate acceptance. Note that no objective 3266 is needed, because the initiator's request was accepted without 3267 change: 3269 [6, 802813, [101]] 3270 [M_END , 802813, [O_ACCEPT]] 3271 h'83061a000c3ffd811865' 3273 D.5. Complete Negotiation Example 3275 Again the initiator unicasts a request: 3277 [3, 13767778, ["EX3", 3, 6, ["NZD", 410]]] 3278 [M_REQ_NEG, 13767778, ["EX3", F_NEG_bits, 6, ["NZD", 410]]] 3279 h'83031a00d214628463455833030682634e5a4419019a' 3281 The responder starts to negotiate (making an offer): 3283 [5, 13767778, ["EX3", 3, 6, ["NZD", 80]]] 3284 [M_NEGOTIATE, 13767778, ["EX3", F_NEG_bits, 6, ["NZD", 80]]] 3285 h'83051a00d214628463455833030682634e5a441850' 3287 The initiator continues to negotiate (reducing its request, and note 3288 that the loop count is decremented): 3290 [5, 13767778, ["EX3", 3, 5, ["NZD", 307]]] 3291 [M_NEGOTIATE, 13767778, ["EX3", F_NEG_bits, 5, ["NZD", 307]]] 3292 h'83051a00d214628463455833030582634e5a44190133' 3294 The responder asks for more time: 3296 [7, 13767778, 34965] 3297 [M_WAIT, 13767778, 34965] 3298 h'83071a00d21462198895' 3300 The responder continues to negotiate (increasing its offer): 3302 [5, 13767778, ["EX3", 3, 4, ["NZD", 120]]] 3303 [M_NEGOTIATE, 13767778, ["EX3", F_NEG_bits, 4, ["NZD", 120]]] 3304 h'83051a00d214628463455833030482634e5a441878' 3306 The initiator continues to negotiate (reducing its request): 3308 [5, 13767778, ["EX3", 3, 3, ["NZD", 246]]] 3309 [M_NEGOTIATE, 13767778, ["EX3", F_NEG_bits, 3, ["NZD", 246]]] 3310 h'83051a00d214628463455833030382634e5a4418f6' 3312 The responder refuses to negotiate further: 3314 [6, 13767778, [102, "Insufficient funds"]] 3315 [M_END , 13767778, [O_DECLINE, "Insufficient funds"]] 3316 h'83061a00d2146282186672496e73756666696369656e742066756e6473' 3317 This negotiation has failed. If either side had sent [M_END, 3318 13767778, [O_ACCEPT]] it would have succeeded, converging on the 3319 objective value in the preceding M_NEGOTIATE. Note that apart from 3320 the initial M_REQ_NEG, the process is symmetrical. 3322 Appendix E. Requirement Analysis of Discovery, Synchronization and 3323 Negotiation 3325 This section discusses the requirements for discovery, negotiation 3326 and synchronization capabilities. The primary user of the protocol 3327 is an autonomic service agent (ASA), so the requirements are mainly 3328 expressed as the features needed by an ASA. A single physical device 3329 might contain several ASAs, and a single ASA might manage several 3330 technical objectives. If a technical objective is managed by several 3331 ASAs, any necessary coordination is outside the scope of the GRASP 3332 signaling protocol. Furthermore, requirements for ASAs themselves, 3333 such as the processing of Intent [RFC7575], are out of scope for the 3334 present document. 3336 E.1. Requirements for Discovery 3338 D1. ASAs may be designed to manage any type of configurable device 3339 or software, as required in Appendix E.2. A basic requirement is 3340 therefore that the protocol can represent and discover any kind of 3341 technical objective (as defined in Section 2.1) among arbitrary 3342 subsets of participating nodes. 3344 In an autonomic network we must assume that when a device starts up 3345 it has no information about any peer devices, the network structure, 3346 or what specific role it must play. The ASA(s) inside the device are 3347 in the same situation. In some cases, when a new application session 3348 starts up within a device, the device or ASA may again lack 3349 information about relevant peers. For example, it might be necessary 3350 to set up resources on multiple other devices, coordinated and 3351 matched to each other so that there is no wasted resource. Security 3352 settings might also need updating to allow for the new device or 3353 user. The relevant peers may be different for different technical 3354 objectives. Therefore discovery needs to be repeated as often as 3355 necessary to find peers capable of acting as counterparts for each 3356 objective that a discovery initiator needs to handle. From this 3357 background we derive the next three requirements: 3359 D2. When an ASA first starts up, it may have no knowledge of the 3360 specific network to which it is attached. Therefore the discovery 3361 process must be able to support any network scenario, assuming only 3362 that the device concerned is bootstrapped from factory condition. 3364 D3. When an ASA starts up, it must require no configured location 3365 information about any peers in order to discover them. 3367 D4. If an ASA supports multiple technical objectives, relevant peers 3368 may be different for different discovery objectives, so discovery 3369 needs to be performed separately to find counterparts for each 3370 objective. Thus, there must be a mechanism by which an ASA can 3371 separately discover peer ASAs for each of the technical objectives 3372 that it needs to manage, whenever necessary. 3374 D5. Following discovery, an ASA will normally perform negotiation or 3375 synchronization for the corresponding objectives. The design should 3376 allow for this by conveniently linking discovery to negotiation and 3377 synchronization. It may provide an optional mechanism to combine 3378 discovery and negotiation/synchronization in a single protocol 3379 exchange. 3381 D6. Some objectives may only be significant on the local link, but 3382 others may be significant across the routed network and require off- 3383 link operations. Thus, the relevant peers might be immediate 3384 neighbors on the same layer 2 link, or they might be more distant and 3385 only accessible via layer 3. The mechanism must therefore provide 3386 both on-link and off-link discovery of ASAs supporting specific 3387 technical objectives. 3389 D7. The discovery process should be flexible enough to allow for 3390 special cases, such as the following: 3392 o During initialization, a device must be able to establish mutual 3393 trust with autonomic nodes elsewhere in the network and 3394 participate in an authentication mechanism. Although this will 3395 inevitably start with a discovery action, it is a special case 3396 precisely because trust is not yet established. This topic is the 3397 subject of [I-D.ietf-anima-bootstrapping-keyinfra]. We require 3398 that once trust has been established for a device, all ASAs within 3399 the device inherit the device's credentials and are also trusted. 3400 This does not preclude the device having multiple credentials. 3402 o Depending on the type of network involved, discovery of other 3403 central functions might be needed, such as the Network Operations 3404 Center (NOC) [I-D.ietf-anima-stable-connectivity]. The protocol 3405 must be capable of supporting such discovery during 3406 initialization, as well as discovery during ongoing operation. 3408 D8. The discovery process must not generate excessive traffic and 3409 must take account of sleeping nodes. 3411 D9. There must be a mechanism for handling stale discovery results. 3413 E.2. Requirements for Synchronization and Negotiation Capability 3415 Autonomic networks need to be able to manage many different types of 3416 parameter and consider many dimensions, such as latency, load, unused 3417 or limited resources, conflicting resource requests, security 3418 settings, power saving, load balancing, etc. Status information and 3419 resource metrics need to be shared between nodes for dynamic 3420 adjustment of resources and for monitoring purposes. While this 3421 might be achieved by existing protocols when they are available, the 3422 new protocol needs to be able to support parameter exchange, 3423 including mutual synchronization, even when no negotiation as such is 3424 required. In general, these parameters do not apply to all 3425 participating nodes, but only to a subset. 3427 SN1. A basic requirement for the protocol is therefore the ability 3428 to represent, discover, synchronize and negotiate almost any kind of 3429 network parameter among selected subsets of participating nodes. 3431 SN2. Negotiation is an iterative request/response process that must 3432 be guaranteed to terminate (with success or failure). While tie- 3433 breaking rules must be defined specifically for each use case, the 3434 protocol should have some general mechanisms in support of loop and 3435 deadlock prevention, such as hop count limits or timeouts. 3437 SN3. Synchronization must be possible for groups of nodes ranging 3438 from small to very large. 3440 SN4. To avoid "reinventing the wheel", the protocol should be able 3441 to encapsulate the data formats used by existing configuration 3442 protocols (such as NETCONF/YANG) in cases where that is convenient. 3444 SN5. Human intervention in complex situations is costly and error- 3445 prone. Therefore, synchronization or negotiation of parameters 3446 without human intervention is desirable whenever the coordination of 3447 multiple devices can improve overall network performance. It follows 3448 that the protocol's resource requirements must be small enough to fit 3449 in any device that would otherwise need human intervention. The 3450 issue of running in constrained nodes is discussed in 3451 [I-D.ietf-anima-reference-model]. 3453 SN6. Human intervention in large networks is often replaced by use 3454 of a top-down network management system (NMS). It therefore follows 3455 that the protocol, as part of the Autonomic Networking 3456 Infrastructure, should be capable of running in any device that would 3457 otherwise be managed by an NMS, and that it can co-exist with an NMS, 3458 and with protocols such as SNMP and NETCONF. 3460 SN7. Specific autonomic features are expected to be implemented by 3461 individual ASAs, but the protocol must be general enough to allow 3462 them. Some examples follow: 3464 o Dependencies and conflicts: In order to decide upon a 3465 configuration for a given device, the device may need information 3466 from neighbors. This can be established through the negotiation 3467 procedure, or through synchronization if that is sufficient. 3468 However, a given item in a neighbor may depend on other 3469 information from its own neighbors, which may need another 3470 negotiation or synchronization procedure to obtain or decide. 3471 Therefore, there are potential dependencies and conflicts among 3472 negotiation or synchronization procedures. Resolving dependencies 3473 and conflicts is a matter for the individual ASAs involved. To 3474 allow this, there need to be clear boundaries and convergence 3475 mechanisms for negotiations. Also some mechanisms are needed to 3476 avoid loop dependencies or uncontrolled growth in a tree of 3477 dependencies. It is the ASA designer's responsibility to avoid or 3478 detect looping dependencies or excessive growth of dependency 3479 trees. The protocol's role is limited to bilateral signaling 3480 between ASAs, and the avoidance of loops during bilateral 3481 signaling. 3483 o Recovery from faults and identification of faulty devices should 3484 be as automatic as possible. The protocol's role is limited to 3485 discovery, synchronization and negotiation. These processes can 3486 occur at any time, and an ASA may need to repeat any of these 3487 steps when the ASA detects an event such as a negotiation 3488 counterpart failing. 3490 o Since a major goal is to minimize human intervention, it is 3491 necessary that the network can in effect "think ahead" before 3492 changing its parameters. One aspect of this is an ASA that relies 3493 on a knowledge base to predict network behavior. This is out of 3494 scope for the signaling protocol. However, another aspect is 3495 forecasting the effect of a change by a "dry run" negotiation 3496 before actually installing the change. Signaling a dry run is 3497 therefore a desirable feature of the protocol. 3499 Note that management logging, monitoring, alerts and tools for 3500 intervention are required. However, these can only be features of 3501 individual ASAs, not of the protocol itself. Another document 3502 [I-D.ietf-anima-stable-connectivity] discusses how such agents may be 3503 linked into conventional OAM systems via an Autonomic Control Plane 3504 [I-D.ietf-anima-autonomic-control-plane]. 3506 SN8. The protocol will be able to deal with a wide variety of 3507 technical objectives, covering any type of network parameter. 3509 Therefore the protocol will need a flexible and easily extensible 3510 format for describing objectives. At a later stage it may be 3511 desirable to adopt an explicit information model. One consideration 3512 is whether to adopt an existing information model or to design a new 3513 one. 3515 E.3. Specific Technical Requirements 3517 T1. It should be convenient for ASA designers to define new 3518 technical objectives and for programmers to express them, without 3519 excessive impact on run-time efficiency and footprint. In 3520 particular, it should be convenient for ASAs to be implemented 3521 independently of each other as user space programs rather than as 3522 kernel code, where such a programming model is possible. The classes 3523 of device in which the protocol might run is discussed in 3524 [I-D.ietf-anima-reference-model]. 3526 T2. The protocol should be easily extensible in case the initially 3527 defined discovery, synchronization and negotiation mechanisms prove 3528 to be insufficient. 3530 T3. To be a generic platform, the protocol payload format should be 3531 independent of the transport protocol or IP version. In particular, 3532 it should be able to run over IPv6 or IPv4. However, some functions, 3533 such as multicasting on a link, might need to be IP version 3534 dependent. By default, IPv6 should be preferred. 3536 T4. The protocol must be able to access off-link counterparts via 3537 routable addresses, i.e., must not be restricted to link-local 3538 operation. 3540 T5. It must also be possible for an external discovery mechanism to 3541 be used, if appropriate for a given technical objective. In other 3542 words, GRASP discovery must not be a prerequisite for GRASP 3543 negotiation or synchronization. 3545 T6. The protocol must be capable of distinguishing multiple 3546 simultaneous operations with one or more peers, especially when wait 3547 states occur. 3549 T7. Intent: Although the distribution of Intent is out of scope for 3550 this document, the protocol must not by design exclude its use for 3551 Intent distribution. 3553 T8. Management monitoring, alerts and intervention: Devices should 3554 be able to report to a monitoring system. Some events must be able 3555 to generate operator alerts and some provision for emergency 3556 intervention must be possible (e.g. to freeze synchronization or 3557 negotiation in a mis-behaving device). These features might not use 3558 the signaling protocol itself, but its design should not exclude such 3559 use. 3561 T9. Because this protocol may directly cause changes to device 3562 configurations and have significant impacts on a running network, all 3563 protocol exchanges need to be fully secured against forged messages 3564 and man-in-the middle attacks, and secured as much as reasonably 3565 possible against denial of service attacks. There must also be an 3566 encryption mechanism to resist unwanted monitoring. However, it is 3567 not required that the protocol itself provides these security 3568 features; it may depend on an existing secure environment. 3570 Appendix F. Capability Analysis of Current Protocols 3572 This appendix discusses various existing protocols with properties 3573 related to the requirements described in Appendix E. The purpose is 3574 to evaluate whether any existing protocol, or a simple combination of 3575 existing protocols, can meet those requirements. 3577 Numerous protocols include some form of discovery, but these all 3578 appear to be very specific in their applicability. Service Location 3579 Protocol (SLP) [RFC2608] provides service discovery for managed 3580 networks, but requires configuration of its own servers. DNS-SD 3581 [RFC6763] combined with mDNS [RFC6762] provides service discovery for 3582 small networks with a single link layer. [RFC7558] aims to extend 3583 this to larger autonomous networks but this is not yet standardized. 3584 However, both SLP and DNS-SD appear to target primarily application 3585 layer services, not the layer 2 and 3 objectives relevant to basic 3586 network configuration. Both SLP and DNS-SD are text-based protocols. 3588 Simple Network Management Protocol (SNMP) [RFC3416] uses a command/ 3589 response model not well suited for peer negotiation. Network 3590 Configuration Protocol (NETCONF) [RFC6241] uses an RPC model that 3591 does allow positive or negative responses from the target system, but 3592 this is still not adequate for negotiation. 3594 There are various existing protocols that have elementary negotiation 3595 abilities, such as Dynamic Host Configuration Protocol for IPv6 3596 (DHCPv6) [RFC3315], Neighbor Discovery (ND) [RFC4861], Port Control 3597 Protocol (PCP) [RFC6887], Remote Authentication Dial In User Service 3598 (RADIUS) [RFC2865], Diameter [RFC6733], etc. Most of them are 3599 configuration or management protocols. However, they either provide 3600 only a simple request/response model in a master/slave context or 3601 very limited negotiation abilities. 3603 There are some signaling protocols with an element of negotiation. 3604 For example Resource ReSerVation Protocol (RSVP) [RFC2205] was 3605 designed for negotiating quality of service parameters along the path 3606 of a unicast or multicast flow. RSVP is a very specialised protocol 3607 aimed at end-to-end flows. A more generic design is General Internet 3608 Signalling Transport (GIST) [RFC5971], but it is complex, tries to 3609 solve many problems, and is also aimed at per-flow signaling across 3610 many hops rather than at device-to-device signaling. However, we 3611 cannot completely exclude extended RSVP or GIST as a synchronization 3612 and negotiation protocol. They do not appear to be directly useable 3613 for peer discovery. 3615 RESTCONF [RFC8040] is a protocol intended to convey NETCONF 3616 information expressed in the YANG language via HTTP, including the 3617 ability to transit HTML intermediaries. While this is a powerful 3618 approach in the context of centralised configuration of a complex 3619 network, it is not well adapted to efficient interactive negotiation 3620 between peer devices, especially simple ones that might not include 3621 YANG processing already. 3623 The Distributed Node Consensus Protocol (DNCP) [RFC7787] is defined 3624 as a generic form of state synchronization protocol, with a proposed 3625 usage profile being the Home Networking Control Protocol (HNCP) 3626 [RFC7788] for configuring Homenet routers. A specific application of 3627 DNCP for autonomic networking was proposed in 3628 [I-D.stenberg-anima-adncp]. 3630 DNCP "is designed to provide a way for each participating node to 3631 publish a set of TLV (Type-Length-Value) tuples, and to provide a 3632 shared and common view about the data published... DNCP is most 3633 suitable for data that changes only infrequently... If constant rapid 3634 state changes are needed, the preferable choice is to use an 3635 additional point-to-point channel..." 3637 Specific features of DNCP include: 3639 o Every participating node has a unique node identifier. 3641 o DNCP messages are encoded as a sequence of TLV objects, sent over 3642 unicast UDP or TCP, with or without (D)TLS security. 3644 o Multicast is used only for discovery of DNCP neighbors when lower 3645 security is acceptable. 3647 o Synchronization of state is maintained by a flooding process using 3648 the Trickle algorithm. There is no bilateral synchronization or 3649 negotiation capability. 3651 o The HNCP profile of DNCP is designed to operate between directly 3652 connected neighbors on a shared link using UDP and link-local IPv6 3653 addresses. 3655 DNCP does not meet the needs of a general negotiation protocol, 3656 because it is designed specifically for flooding synchronization. 3657 Also, in its HNCP profile it is limited to link-local messages and to 3658 IPv6. However, at the minimum it is a very interesting test case for 3659 this style of interaction between devices without needing a central 3660 authority, and it is a proven method of network-wide state 3661 synchronization by flooding. 3663 The Server Cache Synchronization Protocol (SCSP) [RFC2334] also 3664 describes a method for cache synchronization and cache replication 3665 among a group of nodes. 3667 A proposal was made some years ago for an IP based Generic Control 3668 Protocol (IGCP) [I-D.chaparadza-intarea-igcp]. This was aimed at 3669 information exchange and negotiation but not directly at peer 3670 discovery. However, it has many points in common with the present 3671 work. 3673 None of the above solutions appears to completely meet the needs of 3674 generic discovery, state synchronization and negotiation in a single 3675 solution. Many of the protocols assume that they are working in a 3676 traditional top-down or north-south scenario, rather than a fluid 3677 peer-to-peer scenario. Most of them are specialized in one way or 3678 another. As a result, we have not identified a combination of 3679 existing protocols that meets the requirements in Appendix E. Also, 3680 we have not identified a path by which one of the existing protocols 3681 could be extended to meet the requirements. 3683 Authors' Addresses 3685 Carsten Bormann 3686 Universitaet Bremen TZI 3687 Postfach 330440 3688 D-28359 Bremen 3689 Germany 3691 Email: cabo@tzi.org 3692 Brian Carpenter (editor) 3693 Department of Computer Science 3694 University of Auckland 3695 PB 92019 3696 Auckland 1142 3697 New Zealand 3699 Email: brian.e.carpenter@gmail.com 3701 Bing Liu (editor) 3702 Huawei Technologies Co., Ltd 3703 Q14, Huawei Campus 3704 No.156 Beiqing Road 3705 Hai-Dian District, Beijing 100095 3706 P.R. China 3708 Email: leo.liubing@huawei.com