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Grossman, Ed. 3 Internet-Draft DOLBY 4 Intended status: Informational T. Mizrahi 5 Expires: June 14, 2021 HUAWEI 6 A. Hacker 7 MISTIQ 8 December 11, 2020 10 Deterministic Networking (DetNet) Security Considerations 11 draft-ietf-detnet-security-13 13 Abstract 15 A DetNet (deterministic network) provides specific performance 16 guarantees to its data flows, such as extremely low data loss rates 17 and bounded latency (including bounded latency variation, i.e. 18 "jitter"). As a result, securing a DetNet requires that in addition 19 to the best practice security measures taken for any mission-critical 20 network, additional security measures may be needed to secure the 21 intended operation of these novel service properties. 23 This document addresses DetNet-specific security considerations from 24 the perspectives of both the DetNet system-level designer and 25 component designer. System considerations include a threat model, 26 taxonomy of relevant attacks, and associations of threats versus use 27 cases and service properties. Component-level considerations include 28 ingress filtering and packet arrival time violation detection. 30 This document also addresses security considerations specific to the 31 IP and MPLS data plane technologies, thereby complementing the 32 Security Considerations sections of those documents. 34 Status of This Memo 36 This Internet-Draft is submitted in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF). Note that other groups may also distribute 41 working documents as Internet-Drafts. The list of current Internet- 42 Drafts is at https://datatracker.ietf.org/drafts/current/. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on June 14, 2021. 50 Copyright Notice 52 Copyright (c) 2020 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (https://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 4 68 2. Abbreviations and Terminology . . . . . . . . . . . . . . . . 6 69 3. Security Considerations for DetNet Component Design . . . . . 7 70 3.1. Resource Allocation . . . . . . . . . . . . . . . . . . . 7 71 3.2. Explicit Routes . . . . . . . . . . . . . . . . . . . . . 8 72 3.3. Redundant Path Support . . . . . . . . . . . . . . . . . 8 73 3.4. Timing (or other) Violation Reporting . . . . . . . . . . 9 74 4. DetNet Security Considerations Compared With DiffServ 75 Security Considerations . . . . . . . . . . . . . . . . . . . 10 76 5. Security Threats . . . . . . . . . . . . . . . . . . . . . . 11 77 5.1. Threat Model . . . . . . . . . . . . . . . . . . . . . . 11 78 5.2. Threat Analysis . . . . . . . . . . . . . . . . . . . . . 12 79 5.2.1. Delay . . . . . . . . . . . . . . . . . . . . . . . . 12 80 5.2.2. DetNet Flow Modification or Spoofing . . . . . . . . 12 81 5.2.3. Resource Segmentation (Inter-segment Attack) . . . . 12 82 5.2.4. Packet Replication and Elimination . . . . . . . . . 13 83 5.2.4.1. Replication: Increased Attack Surface . . . . . . 13 84 5.2.4.2. Replication-related Header Manipulation . . . . . 13 85 5.2.5. Controller Plane . . . . . . . . . . . . . . . . . . 14 86 5.2.5.1. Path Choice Manipulation . . . . . . . . . . . . 14 87 5.2.5.2. Compromised Controller . . . . . . . . . . . . . 14 88 5.2.6. Reconnaissance . . . . . . . . . . . . . . . . . . . 14 89 5.2.7. Time Synchronization Mechanisms . . . . . . . . . . . 15 90 5.3. Threat Summary . . . . . . . . . . . . . . . . . . . . . 15 91 6. Security Threat Impacts . . . . . . . . . . . . . . . . . . . 16 92 6.1. Delay-Attacks . . . . . . . . . . . . . . . . . . . . . . 19 93 6.1.1. Data Plane Delay Attacks . . . . . . . . . . . . . . 19 94 6.1.2. Controller Plane Delay Attacks . . . . . . . . . . . 20 95 6.2. Flow Modification and Spoofing . . . . . . . . . . . . . 20 96 6.2.1. Flow Modification . . . . . . . . . . . . . . . . . . 20 97 6.2.2. Spoofing . . . . . . . . . . . . . . . . . . . . . . 20 98 6.2.2.1. Dataplane Spoofing . . . . . . . . . . . . . . . 20 99 6.2.2.2. Controller Plane Spoofing . . . . . . . . . . . . 21 100 6.3. Segmentation Attacks (injection) . . . . . . . . . . . . 21 101 6.3.1. Data Plane Segmentation . . . . . . . . . . . . . . . 21 102 6.3.2. Controller Plane Segmentation . . . . . . . . . . . . 21 103 6.4. Replication and Elimination . . . . . . . . . . . . . . . 22 104 6.4.1. Increased Attack Surface . . . . . . . . . . . . . . 22 105 6.4.2. Header Manipulation at Elimination Routers . . . . . 22 106 6.5. Control or Signaling Packet Modification . . . . . . . . 22 107 6.6. Control or Signaling Packet Injection . . . . . . . . . . 22 108 6.7. Reconnaissance . . . . . . . . . . . . . . . . . . . . . 22 109 6.8. Attacks on Time Synchronization Mechanisms . . . . . . . 23 110 6.9. Attacks on Path Choice . . . . . . . . . . . . . . . . . 23 111 7. Security Threat Mitigation . . . . . . . . . . . . . . . . . 23 112 7.1. Path Redundancy . . . . . . . . . . . . . . . . . . . . . 23 113 7.2. Integrity Protection . . . . . . . . . . . . . . . . . . 24 114 7.3. DetNet Node Authentication . . . . . . . . . . . . . . . 25 115 7.4. Dummy Traffic Insertion . . . . . . . . . . . . . . . . . 26 116 7.5. Encryption . . . . . . . . . . . . . . . . . . . . . . . 26 117 7.5.1. Encryption Considerations for DetNet . . . . . . . . 27 118 7.6. Control and Signaling Message Protection . . . . . . . . 28 119 7.7. Dynamic Performance Analytics . . . . . . . . . . . . . . 28 120 7.8. Mitigation Summary . . . . . . . . . . . . . . . . . . . 30 121 8. Association of Attacks to Use Cases . . . . . . . . . . . . . 32 122 8.1. Association of Attacks to Use Case Common Themes . . . . 32 123 8.1.1. Sub-Network Layer . . . . . . . . . . . . . . . . . . 32 124 8.1.2. Central Administration . . . . . . . . . . . . . . . 33 125 8.1.3. Hot Swap . . . . . . . . . . . . . . . . . . . . . . 33 126 8.1.4. Data Flow Information Models . . . . . . . . . . . . 34 127 8.1.5. L2 and L3 Integration . . . . . . . . . . . . . . . . 34 128 8.1.6. End-to-End Delivery . . . . . . . . . . . . . . . . . 34 129 8.1.7. Replacement for Proprietary Fieldbuses and Ethernet- 130 based Networks . . . . . . . . . . . . . . . . . . . 35 131 8.1.8. Deterministic vs Best-Effort Traffic . . . . . . . . 35 132 8.1.9. Deterministic Flows . . . . . . . . . . . . . . . . . 36 133 8.1.10. Unused Reserved Bandwidth . . . . . . . . . . . . . . 36 134 8.1.11. Interoperability . . . . . . . . . . . . . . . . . . 36 135 8.1.12. Cost Reductions . . . . . . . . . . . . . . . . . . . 37 136 8.1.13. Insufficiently Secure Components . . . . . . . . . . 37 137 8.1.14. DetNet Network Size . . . . . . . . . . . . . . . . . 37 138 8.1.15. Multiple Hops . . . . . . . . . . . . . . . . . . . . 38 139 8.1.16. Level of Service . . . . . . . . . . . . . . . . . . 38 140 8.1.17. Bounded Latency . . . . . . . . . . . . . . . . . . . 39 141 8.1.18. Low Latency . . . . . . . . . . . . . . . . . . . . . 39 142 8.1.19. Bounded Jitter (Latency Variation) . . . . . . . . . 39 143 8.1.20. Symmetrical Path Delays . . . . . . . . . . . . . . . 39 144 8.1.21. Reliability and Availability . . . . . . . . . . . . 40 145 8.1.22. Redundant Paths . . . . . . . . . . . . . . . . . . . 40 146 8.1.23. Security Measures . . . . . . . . . . . . . . . . . . 40 147 8.2. Summary of Attack Types per Use Case Common Theme . . . . 41 148 8.3. Security Considerations for OAM Traffic . . . . . . . . . 43 149 9. DetNet Technology-Specific Threats . . . . . . . . . . . . . 43 150 9.1. IP . . . . . . . . . . . . . . . . . . . . . . . . . . . 44 151 9.2. MPLS . . . . . . . . . . . . . . . . . . . . . . . . . . 45 152 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46 153 11. Security Considerations . . . . . . . . . . . . . . . . . . . 46 154 12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 46 155 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 46 156 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 47 157 14.1. Normative References . . . . . . . . . . . . . . . . . . 47 158 14.2. Informative References . . . . . . . . . . . . . . . . . 48 159 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 52 161 1. Introduction 163 A DetNet is one that can carry data flows for real-time applications 164 with extremely low data loss rates and bounded latency. The bounds 165 on latency defined by DetNet 166 ([I-D.ietf-detnet-flow-information-model]) include both worst case 167 latency (Maximum Latency, Section 5.9.2) and worst case jitter 168 (Maximum Latency Variation, Section 5.9.3). Deterministic networks 169 have been successfully deployed in real-time Operational Technology 170 (OT) applications for some years, however such networks are typically 171 isolated from external access, and thus the security threat from 172 external attackers is low. IETF Deterministic Networking (DetNet, 173 [RFC8655]) specifies a set of technologies that enable creation of 174 deterministic flows on IP-based networks of potentially wide area (on 175 the scale of a corporate network), potentially bringing the OT 176 network into contact with Information Technology (IT) traffic and 177 security threats that lie outside of a tightly controlled and bounded 178 area (such as the internals of an aircraft). 180 These DetNet (OT-type) technologies may not have previously been 181 deployed on a wide area IP-based network that also carries IT 182 traffic, and thus can present security considerations that may be new 183 to IP-based wide area network designers; this document provides 184 insight into such system-level security considerations. In addition, 185 designers of DetNet components (such as routers) face new security- 186 related challenges in providing DetNet services, for example 187 maintaining reliable isolation between traffic flows in an 188 environment where IT traffic co-mingles with critical reserved- 189 bandwidth OT traffic; this document also examines security 190 implications internal to DetNet components. 192 Security is of particularly high importance in DetNet because many of 193 the use cases which are enabled by DetNet [RFC8578] include control 194 of physical devices (power grid devices, industrial controls, 195 building controls) which can have high operational costs for failure, 196 and present potentially attractive targets for cyber-attackers. 198 This situation is even more acute given that one of the goals of 199 DetNet is to provide a "converged network", i.e. one that includes 200 both IT traffic and OT traffic, thus exposing potentially sensitive 201 OT devices to attack in ways that were not previously common (usually 202 because they were under a separate control system or otherwise 203 isolated from the IT network, for example [ARINC664P7]). Security 204 considerations for OT networks are not a new area, and there are many 205 OT networks today that are connected to wide area networks or the 206 Internet; this document focuses on the issues that are specific to 207 the DetNet technologies and use cases. 209 Given the above considerations, securing a DetNet starts with a 210 scrupulously well-designed and well-managed engineered network 211 following industry best practices for security at both the data plane 212 and controller plane; this is the assumed starting point for the 213 considerations discussed herein. Such assumptions also depend on the 214 network components themselves upholding the security-related 215 properties that are to be assumed by DetNet system-level designers; 216 for example, the assumption that network traffic associated with a 217 given flow can never affect traffic associated with a different flow 218 is only true if the underlying components make it so. Such 219 properties, which may represent new challenges to component 220 designers, are also considered herein. 222 In this context we view the "traditional" (i.e. non-time-sensitive) 223 network design and management aspects of network security as being 224 primarily concerned with denial-of service prevention, i.e. they must 225 ensure that DetNet traffic goes where it's supposed to and that an 226 external attacker can't inject traffic that disrupts the delivery 227 timing assurance of the DetNet. The time-specific aspects of DetNet 228 security presented here take up where those "traditional" design and 229 management aspects leave off. 231 However note that "traditional" methods for mitigating (among all the 232 others) denial-of service attack (such as throttling) can only be 233 effectively used in a DetNet when their use does not compromise the 234 required time-sensitive or behavioral properties required for the OT 235 flows on the network. For example, a "retry" protocol is typically 236 not going to be compatible with a low-latency (worst-case maximum 237 latency) requirement, however if in a specific use case and 238 implementation such a retry protocol is able to meet the timing 239 constraints, then it may well be used in that context. Similarly if 240 common security protocols such as TLS/DTLS or IPsec are to be used, 241 it must be verified that their implementations are able to meet the 242 timing and behavioral requirements of the time-sensitive network as 243 implemented for the given use case. An example of "behavioral 244 properties" might be that dropping of more than a specific number of 245 packets in a row is not acceptable according to the service level 246 agreement. 248 The exact security requirements for any given DetNet are necessarily 249 specific to the use cases handled by that network. Thus the reader 250 is assumed to be familiar with the specific security requirements of 251 their use cases, for example those outlined in the DetNet Use Cases 252 [RFC8578] and the Security Considerations sections of the DetNet 253 documents applicable to the network technologies in use, for example 254 [RFC8939]). Readers can find a general introduction to the DetNet 255 Architecture in [RFC8655], the DetNet Data Plane in [RFC8938], and 256 the Flow Information Model in 257 [I-D.ietf-detnet-flow-information-model]. 259 The DetNet technologies include ways to: 261 o Assign data plane resources for DetNet flows in some or all of the 262 intermediate nodes (routers) along the path of the flow 264 o Provide explicit routes for DetNet flows that do not dynamically 265 change with the network topology in ways that affect the quality 266 of service received by the affected flow(s) 268 o Distribute data from DetNet flow packets over time and/or space to 269 ensure delivery of the data in each packet in spite of the loss of 270 a path. 272 This document includes sections considering DetNet component design 273 as well as system design. The latter includes threat modeling and 274 analysis, threat impact and mitigation, and the association of 275 attacks with use cases (based on the Use Case Common Themes section 276 of the DetNet Use Cases [RFC8578]). 278 The structure of the threat model and threat analysis sections were 279 originally derived from [RFC7384], which also considers time-related 280 security considerations in IP networks. 282 2. Abbreviations and Terminology 284 IT: Information Technology (the application of computers to store, 285 study, retrieve, transmit, and manipulate data or information, often 286 in the context of a business or other enterprise - [IT_DEF]). 288 OT: Operational Technology (the hardware and software dedicated to 289 detecting or causing changes in physical processes through direct 290 monitoring and/or control of physical devices such as valves, pumps, 291 etc. - [OT_DEF]) 293 Component: A component of a DetNet system - used here to refer to any 294 hardware or software element of a DetNet which implements DetNet- 295 specific functionality, for example all or part of a router, switch, 296 or end system. 298 Device: Used here to refer to a physical entity controlled by the 299 DetNet, for example a motor. 301 Resource Segmentation Used as a more general form for Network 302 Segmentation (the act or practice of splitting a computer network 303 into subnetworks, each being a network segment - [RS_DEF]) 305 3. Security Considerations for DetNet Component Design 307 As noted above, DetNet provides resource allocation, explicit routes 308 and redundant path support. Each of these has associated security 309 implications, which are discussed in this section, in the context of 310 component design. Detection, reporting and appropriate action in the 311 case of packet arrival time violations are also discussed. 313 3.1. Resource Allocation 315 A DetNet system security designer relies on the premise that any 316 resources allocated to a resource-reserved (OT-type) flow are 317 inviolable, in other words there is no physical possibility within a 318 DetNet component that resources allocated to a given flow can be 319 compromised by any type of traffic in the network; this includes both 320 malicious traffic as well as inadvertent traffic such as might be 321 produced by a malfunctioning component, for example one made by a 322 different manufacturer. From a security standpoint, this is a 323 critical assumption, for example when designing against DOS attacks. 325 It is the responsibility of the component designer to ensure that 326 this condition is met; this implies protection against excess traffic 327 from adjacent flows, and against compromises to the resource 328 allocation/deallocation process, for example through the use of 329 traffic shaping and policing. 331 As an example, consider the implementation of Flow Aggregation for 332 DetNet flows (as discussed in [RFC8938]). In this example say there 333 are N flows that are to be aggregated, thus the bandwidth resources 334 of the aggregate flow must be sufficient to contain the sum of the 335 bandwidth reservation for the N flows. However if one of those flows 336 were to consume more than its individually allocated bandwidth, this 337 could cause starvation of the other flows. Thus simply providing and 338 enforcing the calculated aggregate bandwidth may not be a complete 339 solution - the bandwidth for each individual flow must still be 340 guaranteed, for example via ingress policing of each flow (i.e. 341 before it is aggregated). Alternatively, if by some other means each 342 flow to be aggregated can be trusted not to exceed its allocated 343 bandwidth, the same goal can be achieved. 345 3.2. Explicit Routes 347 The DetNet-specific purpose for constraining the ability of the 348 DetNet to re-route OT traffic is to maintain the specified service 349 parameters (such as upper and lower latency boundaries) for a given 350 flow. For example if the network were to re-route a flow (or some 351 part of a flow) based exclusively on statistical path usage metrics, 352 or due to malicious activity, it is possible that the new path would 353 have a latency that is outside the required latency bounds which were 354 designed into the original TE-designed path, thereby violating the 355 quality of service for the affected flow (or part of that flow). 357 However, it is acceptable for the network to re-route OT traffic in 358 such a way as to maintain the specified latency bounds (and any other 359 specified service properties) for any reason, for example in response 360 to a runtime component or path failure. From a security standpoint, 361 the system designer relies on the premise that the packets will be 362 delivered with the specified latency boundaries; thus any component 363 that is involved in controlling or implementing any change of the 364 initially TE-configured flow routes needs to prevent malicious or 365 accidental re-routing of OT flows that might adversely affect 366 delivering the traffic within the specified service parameters. 368 3.3. Redundant Path Support 370 The DetNet provision for redundant paths (PREOF) (as defined in the 371 DetNet Architecture [RFC8655]) provides the foundation for high 372 reliablity of a DetNet, by virtually eliminating packet loss (i.e. to 373 a degree which is implementation-dependent) through hitless redundant 374 packet delivery. (Note that PREOF is not defined for a DetNet IP 375 data plane). 377 It is the responsibility of the system designer to determine the 378 level of reliability required by their use case, and to specify 379 redundant paths sufficient to provide the desired level of 380 reliability (in as much as that reliability can be provided through 381 the use of redundant paths). It is the responsibility of the 382 component designer to ensure that the relevant PREOF operations are 383 executed reliably and securely, to avoid potentially catastrophic 384 situations for the operational technology relying on them. 386 However, note that not all PREOF operations are necessarily 387 implemented in every network; for example a packet re-ordering 388 function may not be necessary if the packets are either not required 389 to be in order, or if the ordering is performed in some other part of 390 the network. 392 Ideally a redundant path for a flow could be specified from end to 393 end, however given that this is not always possible (as described in 394 [RFC8655]) the system designer will need to consider the resulting 395 end-to-end reliability and security resulting from any given 396 arrangment of network segments along the path, each of which provides 397 its individual PREOF implementation and thus its individual level of 398 reliabiilty and security. 400 At the data plane the implementation of PREOF depends on the correct 401 assignment and interpretation of packet sequence numbers, as well as 402 the actions taken based on them, such as elimination (including 403 elimination of packets with spurious sequence numbers). Thus the 404 integrity of these values must be maintained by the component as they 405 are assigned by the DetNet Data Plane Service sub-layer, and 406 transported by the Forwarding sub-layer. This is no different than 407 the integrity of the values in any header used by the DetNet (or any 408 other) data plane, and is not unique to redundant paths. The 409 integrity protection of header values is technology-dependent; for 410 example, in Layer 2 networks the integrity of the header fields can 411 be protected by using MACsec [IEEE802.1AE-2018]. Similary, from the 412 sequence number injection perspective, it is no different from any 413 other protocols that use sequence numbers. 415 3.4. Timing (or other) Violation Reporting 417 Another fundamental assumption of a secure DetNet is that in any case 418 in which an incoming packet arrives with any timing or bandwidth 419 violation, something can be done about it which doesn't cause damage 420 to the system. For example having the network shut down a link if a 421 packet arrives outside of its prescribed time window may serve the 422 attacker better than it serves the network. That means that the data 423 plane of the component must be able to detect and act on a variety of 424 such violations, at least alerting the controller plane. Any action 425 apart from that needs to be carefully considered in the context of 426 the specific system. Some possible violations that warrant detection 427 include cases where a packet arrives: 429 o Outside of its prescribed time window 430 o Within its time window but with a compromised time stamp that 431 makes it appear that it is not within its window 433 o Exceeding the reserved flow bandwidth 435 Logging of such issues is unlikely to be adequate, since a delay in 436 response to the situation could result in material damage, for 437 example to mechanical devices controlled by the network. Given that 438 the data plane component probably has no knowledge of the use case of 439 the network, or its applications and end systems, it would seem 440 useful for a data plane component to allow the system designer to 441 configure its actions in the face of such violations. 443 Some possible direct actions that may be taken at the data plane 444 include traffic policing and shaping functions (e.g., those described 445 in [RFC2475]), separating flows into per-flow rate-limited queues, 446 and potentially applying active queue management [RFC7567]. However 447 if those (or any other) actions are to be taken, the system designer 448 must ensure that the results of such actions do not compromise the 449 continued safe operation of the system. For example, the network 450 (i.e. the controller plane and data plane working together) must 451 mitigate in a timely fashion any potential adverse effect on 452 mechanical devices controlled by the network. 454 4. DetNet Security Considerations Compared With DiffServ Security 455 Considerations 457 DetNet is designed to be compatible with DiffServ [RFC2474] as 458 applied to IT traffic in the DetNet. DetNet also incorporates the 459 use of the 6-bit value of the DSCP field of the TOS field of the IP 460 header for flow identification for OT traffic, however the DetNet 461 interpretation of the DSCP value for OT traffic is not equivalent to 462 the PHB selection behavior as defined by DiffServ. 464 Thus security consideration for DetNet have some aspects in common 465 with DiffServ, in fact overlapping 100% with respect to IP IT 466 traffic. Security considerations for these aspects are part of the 467 existing literature on IP network security, specifically the Security 468 Considerations sections of [RFC2474] and [RFC2475]. However DetNet 469 also introduces timing and other considerations which are not present 470 in DiffServ, so the DiffServ security considerations are necessary 471 but not sufficient for DetNet. 473 In the case of DetNet OT traffic, the DSCP value is interpreted 474 differently than in DiffServ and contribute to determination of the 475 service provided to the packet. In DetNet, there are similar 476 consequences to DiffServ for lack of detection of, or incorrect 477 handling of, packets with mismarked DSCP values, and many of the 478 points made in the DiffServ Security discussions ([RFC2475] Sec. 6.1 479 , [RFC2474] Sec. 7 and [RFC6274] Sec 3.3.2.1) are also relevant to 480 DetNet OT traffic, though perhaps in modified form. For example, in 481 DetNet the effect of an undetected or incorrectly handled maliciously 482 mismarked DSCP field in an OT packet is not identical to affecting 483 the PHB of that packet, since DetNet does not use the PHB concept for 484 OT traffic; but nonetheless the service provided to the packet could 485 be affected, so mitigation measures analogous to those prescribed by 486 DiffServ would be appropriate for DetNet. For example, mismarked 487 DSCP values should not cause failure of network nodes. The remarks 488 in [RFC2474] regarding IPsec and Tunnelling Interactions are also 489 relevant (though this is not to say that other sections are less 490 relevant). 492 5. Security Threats 494 This section presents a threat model, and analyzes the possible 495 threats in a DetNet-enabled network. The threats considered in this 496 section are independent of any specific technologies used to 497 implement the DetNet; Section 9 considers attacks that are associated 498 with the DetNet technologies encompassed by [RFC8938]. 500 We distinguish controller plane threats from data plane threats. The 501 attack surface may be the same, but the types of attacks as well as 502 the motivation behind them, are different. For example, a delay 503 attack is more relevant to data plane than to controller plane. 504 There is also a difference in terms of security solutions: the way 505 you secure the data plane is often different than the way you secure 506 the controller plane. 508 5.1. Threat Model 510 The threat model used in this document employs organizational 511 elements of the threat models of [RFC7384] and [RFC7835]. This model 512 classifies attackers based on two criteria: 514 o Internal vs. external: internal attackers either have access to a 515 trusted segment of the network or possess the encryption or 516 authentication keys. External attackers, on the other hand, do 517 not have the keys and have access only to the encrypted or 518 authenticated traffic. 520 o On-path vs. off-path: on-path attackers are located in a position 521 that allows interception and modification of in-flight protocol 522 packets, whereas off-path attackers can only attack by generating 523 protocol packets. 525 Care has also been taken to adhere to Section 5 of [RFC3552], both 526 with respect to which attacks are considered out-of-scope for this 527 document, but also which are considered to be the most common threats 528 (explored further in Section 5.2, Threat Analysis). Most of the 529 direct threats to DetNet are active attacks (i.e. attacks that modify 530 DetNet traffic), but it is highly suggested that DetNet application 531 developers take appropriate measures to protect the content of the 532 DetNet flows from passive attacks (i.e. attacks that observe but do 533 not modify DetNet traffic) for example through the use of TLS or 534 DTLS. 536 DetNet-Service, one of the service scenarios described in 537 [I-D.varga-detnet-service-model], is the case where a service 538 connects DetNet islands, i.e. two or more otherwise independent 539 DetNets are connected via a link that is not intrinsically part of 540 either network. This implies that there could be DetNet traffic 541 flowing over a non-DetNet link, which may provide an attacker with an 542 advantageous opportunity to tamper with DetNet traffic. The security 543 properties of non-DetNet links are outside of the scope of DetNet 544 Security, but it should be noted that use of non-DetNet services to 545 interconnect DetNets merits security analysis to ensure the integrity 546 of the networks involved. 548 5.2. Threat Analysis 550 5.2.1. Delay 552 An attacker can maliciously delay DetNet data flow traffic. By 553 delaying the traffic, the attacker can compromise the service of 554 applications that are sensitive to high delays or to high delay 555 variation. The delay may be constant or modulated. 557 5.2.2. DetNet Flow Modification or Spoofing 559 An attacker can modify some header fields of en route packets in a 560 way that causes the DetNet flow identification mechanisms to 561 misclassify the flow. Alternatively, the attacker can inject traffic 562 that is tailored to appear as if it belongs to a legitimate DetNet 563 flow. The potential consequence is that the DetNet flow resource 564 allocation cannot guarantee the performance that is expected when the 565 flow identification works correctly. 567 5.2.3. Resource Segmentation (Inter-segment Attack) 569 An attacker can inject traffic that will consume network resources 570 such that it affects DetNet flows. This can be performed using non- 571 DetNet traffic that indirectly affects DetNet traffic (hardware 572 resource exhaustion), or by using DetNet traffic from one DetNet flow 573 that directly affects traffic from different DetNet flows. 575 5.2.4. Packet Replication and Elimination 577 5.2.4.1. Replication: Increased Attack Surface 579 Redundancy is intended to increase the robustness and survivability 580 of DetNet flows, and replication over multiple paths can potentially 581 mitigate an attack that is limited to a single path. However, the 582 fact that packets are replicated over multiple paths increases the 583 attack surface of the network, i.e., there are more points in the 584 network that may be subject to attacks. 586 5.2.4.2. Replication-related Header Manipulation 588 An attacker can manipulate the replication-related header fields. 589 This capability opens the door for various types of attacks. For 590 example: 592 o Forward both replicas - malicious change of a packet SN (Sequence 593 Number) can cause both replicas of the packet to be forwarded. 594 Note that this attack has a similar outcome to a replay attack. 596 o Eliminate both replicas - SN manipulation can be used to cause 597 both replicas to be eliminated. In this case an attacker that has 598 access to a single path can cause packets from other paths to be 599 dropped, thus compromising some of the advantage of path 600 redundancy. 602 o Flow hijacking - an attacker can hijack a DetNet flow with access 603 to a single path by systematically replacing the SNs on the given 604 path with higher SN values. For example, an attacker can replace 605 every SN value S with a higher value S+C, where C is a constant 606 integer. Thus, the attacker creates a false illusion that the 607 attacked path has the lowest delay, causing all packets from other 608 paths to be eliminated in favor of the attacked path. Once the 609 flow from the compromised path is favored by the elminating 610 bridge, the flow is hijacked by the attacker. It is now posible 611 to either replace en route packets with malicious packets, or 612 simply injecting errors, causing the packets to be dropped at 613 their destination. 615 o Amplification - an attacker who injects packets into a flow that 616 is to be replicated will have their attack amplified through the 617 replication process. This is no different than any attacker who 618 injects packets that are delivered through multicast, broadcast, 619 or other point-to-multi-point mechanisms. 621 5.2.5. Controller Plane 623 5.2.5.1. Path Choice Manipulation 625 5.2.5.1.1. Control or Signaling Packet Modification 627 An attacker can maliciously modify en route control packets in order 628 to disrupt or manipulate the DetNet path/resource allocation. 630 5.2.5.1.2. Control or Signaling Packet Injection 632 An attacker can maliciously inject control packets in order to 633 disrupt or manipulate the DetNet path/resource allocation. 635 5.2.5.1.3. Increased Attack Surface 637 One of the possible consequences of a path manipulation attack is an 638 increased attack surface. Thus, when the attack described in the 639 previous subsection is implemented, it may increase the potential of 640 other attacks to be performed. 642 5.2.5.2. Compromised Controller 644 An attacker can subvert a controller, or enable a compromised 645 controller to falsely represent itself as a controller so that the 646 network nodes believe it to be authorized to instruct them. 648 Presence of compromised nodes in a DetNet is not a new threat that 649 arises as a result of determinism or time sensitivity; the same 650 techniques used to prevent or mitigate against compromised nodes in 651 any network are equally applicable in the DetNet case. However this 652 underscores the requirement for careful system security design in a 653 DetNet, given that the effects of even one bad actor on the network 654 can be potentially catastrophic. 656 Security concerns specific to any given controller plane technology 657 used in DetNet will be addressed by the DetNet documents associated 658 with that technology. 660 5.2.6. Reconnaissance 662 A passive eavesdropper can identify DetNet flows and then gather 663 information about en route DetNet flows, e.g., the number of DetNet 664 flows, their bandwidths, their schedules, or other temporal 665 properties. The gathered information can later be used to invoke 666 other attacks on some or all of the flows. 668 DetNet flows are typically uniquely identified by their 6-tuple, i.e. 669 fields within the IP header, however in some implementations the flow 670 ID may also be augmented by additional per-flow attributes known to 671 the system, e.g. above the IP-layer. For the purpose of this 672 document we assume any such additional fields used for flow ID are 673 encrypted and/or integrity-protected from external attackers. 675 5.2.7. Time Synchronization Mechanisms 677 An attacker can use any of the attacks described in [RFC7384] to 678 attack the synchronization protocol, thus affecting the DetNet 679 service. 681 5.3. Threat Summary 683 A summary of the attacks that were discussed in this section is 684 presented in Figure 1. For each attack, the table specifies the type 685 of attackers that may invoke the attack. In the context of this 686 summary, the distinction between internal and external attacks is 687 under the assumption that a corresponding security mechanism is being 688 used, and that the corresponding network equipment takes part in this 689 mechanism. 691 +-------------------------------------------+----+-----+----+-----+ 692 | Attack | Attacker Type | 693 | +----------+----------+ 694 | | Internal | External | 695 | |On-P|Off-P|On-P|Off-P| 696 +-------------------------------------------+----+-----+----+-----+ 697 |Delay attack | + | + | + | + | 698 +-------------------------------------------+----+-----+----+-----+ 699 |DetNet Flow Modification or Spoofing | + | + | | | 700 +-------------------------------------------+----+-----+----+-----+ 701 |Inter-segment Attack | + | + | + | + | 702 +-------------------------------------------+----+-----+----+-----+ 703 |Replication: Increased Attack Surface | + | + | + | + | 704 +-------------------------------------------+----+-----+----+-----+ 705 |Replication-related Header Manipulation | + | | | | 706 +-------------------------------------------+----+-----+----+-----+ 707 |Path Manipulation | + | + | | | 708 +-------------------------------------------+----+-----+----+-----+ 709 |Path Choice: Increased Attack Surface | + | + | + | + | 710 +-------------------------------------------+----+-----+----+-----+ 711 |Control or Signaling Packet Modification | + | | | | 712 +-------------------------------------------+----+-----+----+-----+ 713 |Control or Signaling Packet Injection | + | + | | | 714 +-------------------------------------------+----+-----+----+-----+ 715 |Reconnaissance | + | | + | | 716 +-------------------------------------------+----+-----+----+-----+ 717 |Attacks on Time Synchronization Mechanisms | + | + | + | + | 718 +-------------------------------------------+----+-----+----+-----+ 720 Figure 1: Threat Analysis Summary 722 6. Security Threat Impacts 724 This section describes and rates the impact of the attacks described 725 in Section 5, Security Threats. In this section, the impacts as 726 described assume that the associated mitigation is not present or has 727 failed. Mitigations are discussed in Section 7, Security Threat 728 Mitigation. 730 In computer security, the impact (or consequence) of an incident can 731 be measured in loss of confidentiality, integrity or availability of 732 information. In the case of time sensitive networks, the impact of a 733 network exploit can also include failure or malfunction of mechanical 734 and/or other OT systems. 736 DetNet raises these stakes significantly for OT applications, 737 particularly those which may have been designed to run in an OT-only 738 environment and thus may not have been designed for security in an IT 739 environment with its associated components, services and protocols. 741 The extent of impact of a successful vulnerability exploit varies 742 considerably by use case and by industry; additional insights 743 regarding the individual use cases is available from [RFC8578], 744 DetNet Use Cases. Each of those use cases is represented in 745 Figure 2, including Pro Audio, Electrical Utilities, Industrial M2M 746 (split into two areas, M2M Data Gathering and M2M Control Loop), and 747 others. 749 Aspects of Impact (left column) include Criticality of Failure, 750 Effects of Failure, Recovery, and DetNet Functional Dependence. 751 Criticality of failure summarizes the seriousness of the impact. The 752 impact of a resulting failure can affect many different metrics that 753 vary greatly in scope and severity. In order to reduce the number of 754 variables, only the following were included: Financial, Health and 755 Safety, People well being (People WB), Affect on a single 756 organization, and affect on multiple organizations. Recovery 757 outlines how long it would take for an affected use case to get back 758 to its pre-failure state (Recovery time objective, RTO), and how much 759 of the original service would be lost in between the time of service 760 failure and recovery to original state (Recovery Point Objective, 761 RPO). DetNet dependence maps how much the following DetNet service 762 objectives contribute to impact of failure: Time dependency, data 763 integrity, source node integrity, availability, latency/jitter. 765 The scale of the Impact mappings is low, medium, and high. In some 766 use cases there may be a multitude of specific applications in which 767 DetNet is used. For simplicity this section attempts to average the 768 varied impacts of different applications. This section does not 769 address the overall risk of a certain impact which would require the 770 likelihood of a failure happening. 772 In practice any such ratings will vary from case to case; the ratings 773 shown here are given as examples. 775 Table, Part One (of Two) 776 +------------------+-----------------------------------------+-----+ 777 | | Pro A | Util | Bldg |Wire- | Cell |M2M |M2M | 778 | | | | | less | |Data |Ctrl | 779 +------------------+-----------------------------------------+-----+ 780 | Criticality | Med | Hi | Low | Med | Med | Med | Med | 781 +------------------+-----------------------------------------+-----+ 782 | Effects 783 +------------------+-----------------------------------------+-----+ 784 | Financial | Med | Hi | Med | Med | Low | Med | Med | 785 +------------------+-----------------------------------------+-----+ 786 | Health/Safety | Med | Hi | Hi | Med | Med | Med | Med | 787 +------------------+-----------------------------------------+-----+ 788 | People WB | Med | Hi | Hi | Low | Hi | Low | Low | 789 +------------------+-----------------------------------------+-----+ 790 | Effect 1 org | Hi | Hi | Med | Hi | Med | Med | Med | 791 +------------------+-----------------------------------------+-----+ 792 | Effect >1 org | Med | Hi | Low | Med | Med | Med | Med | 793 +------------------+-----------------------------------------+-----+ 794 |Recovery 795 +------------------+-----------------------------------------+-----+ 796 | Recov Time Obj | Med | Hi | Med | Hi | Hi | Hi | Hi | 797 +------------------+-----------------------------------------+-----+ 798 | Recov Point Obj | Med | Hi | Low | Med | Low | Hi | Hi | 799 +------------------+-----------------------------------------+-----+ 800 |DetNet Dependence 801 +------------------+-----------------------------------------+-----+ 802 | Time Dependency | Hi | Hi | Low | Hi | Med | Low | Hi | 803 +------------------+-----------------------------------------+-----+ 804 | Latency/Jitter | Hi | Hi | Med | Med | Low | Low | Hi | 805 +------------------+-----------------------------------------+-----+ 806 | Data Integrity | Hi | Hi | Med | Hi | Low | Hi | Low | 807 +------------------+-----------------------------------------+-----+ 808 | Src Node Integ | Hi | Hi | Med | Hi | Med | Hi | Hi | 809 +------------------+-----------------------------------------+-----+ 810 | Availability | Hi | Hi | Med | Hi | Low | Hi | Hi | 811 +------------------+-----------------------------------------+-----+ 813 Table, Part Two (of Two) 814 +------------------+--------------------------+ 815 | | Mining | Block | Network | 816 | | | Chain | Slicing | 817 +------------------+--------------------------+ 818 | Criticality | Hi | Med | Hi | 819 +------------------+--------------------------+ 820 | Effects 821 +------------------+--------------------------+ 822 | Financial | Hi | Hi | Hi | 823 +------------------+--------------------------+ 824 | Health/Safety | Hi | Low | Med | 825 +------------------+--------------------------+ 826 | People WB | Hi | Low | Med | 827 +------------------+--------------------------+ 828 | Effect 1 org | Hi | Hi | Hi | 829 +------------------+--------------------------+ 830 | Effect >1 org | Hi | Low | Hi | 831 +------------------+--------------------------+ 832 |Recovery 833 +------------------+--------------------------+ 834 | Recov Time Obj | Hi | Low | Hi | 835 +------------------+--------------------------+ 836 | Recov Point Obj | Hi | Low | Hi | 837 +------------------+--------------------------+ 838 |DetNet Dependence 839 +------------------+--------------------------+ 840 | Time Dependency | Hi | Low | Hi | 841 +------------------+--------------------------+ 842 | Latency/Jitter | Hi | Low | Hi | 843 +------------------+--------------------------+ 844 | Data Integrity | Hi | Hi | Hi | 845 +------------------+--------------------------+ 846 | Src Node Integ | Hi | Hi | Hi | 847 +------------------+--------------------------+ 848 | Availability | Hi | Hi | Hi | 849 +------------------+--------------------------+ 851 Figure 2: Impact of Attacks by Use Case Industry 853 The rest of this section will cover impact of the different groups in 854 more detail. 856 6.1. Delay-Attacks 858 6.1.1. Data Plane Delay Attacks 860 Note that 'delay attack' also includes the possibility of a 'negative 861 delay' or early arrival of a packet, or possibly adversely changing 862 the timestamp value. 864 Delayed messages in a DetNet link can result in the same behavior as 865 dropped messages in ordinary networks as the services attached to the 866 DetNet flow have strict deterministic requirements. 868 For a single path scenario, disruption is a real possibility, whereas 869 in a multipath scenario, large delays or instabilities in one DetNet 870 flow can lead to increased buffer and processor resources at the 871 eliminating router. 873 A data-plane delay attack on a system controlling substantial moving 874 devices, for example in industrial automation, can cause physical 875 damage. For example, if the network promises a bounded latency of 876 2ms for a flow, yet the machine receives it with 5ms latency, control 877 loop of the machine can become unstable. 879 6.1.2. Controller Plane Delay Attacks 881 In and of itself, this is not directly a threat to the DetNet 882 service, but the effects of delaying control messages can have quite 883 adverse effects later. 885 o Delayed tear-down can lead to resource leakage, which in turn can 886 result in failure to allocate new DetNet flows, finally giving 887 rise to a denial of service attack. 889 o Failure to deliver, or severely delaying, controller plane 890 messages adding an endpoint to a multicast-group will prevent the 891 new endpoint from receiving expected frames thus disrupting 892 expected behavior. 894 o Delaying messages removing an endpoint from a group can lead to 895 loss of privacy as the endpoint will continue to receive messages 896 even after it is supposedly removed. 898 6.2. Flow Modification and Spoofing 900 6.2.1. Flow Modification 902 If the contents of a packet header or body can be modified by the 903 attacker, this can cause the packet to be routed incorrectly or 904 dropped, or the payload to be corrupted or subtly modified. 906 6.2.2. Spoofing 908 6.2.2.1. Dataplane Spoofing 910 Spoofing dataplane messages can result in increased resource 911 consumptions on the routers throughout the network as it will 912 increase buffer usage and processor utilization. This can lead to 913 resource exhaustion and/or increased delay. 915 If the attacker manages to create valid headers, the false messages 916 can be forwarded through the network, using part of the allocated 917 bandwidth. This in turn can cause legitimate messages to be dropped 918 when the resource budget has been exhausted. 920 Finally, the endpoint will have to deal with invalid messages being 921 delivered to the endpoint instead of (or in addition to) a valid 922 message. 924 6.2.2.2. Controller Plane Spoofing 926 A successful controller plane spoofing-attack will potentionally have 927 adverse effects. It can do virtually anything from: 929 o modifying existing DetNet flows by changing the available 930 bandwidth 932 o add or remove endpoints from a DetNet flow 934 o drop DetNet flows completely 936 o falsely create new DetNet flows (exhaust the systems resources, or 937 to enable DetNet flows that are outside the control of the Network 938 Engineer) 940 6.3. Segmentation Attacks (injection) 942 6.3.1. Data Plane Segmentation 944 Injection of false messages in a DetNet flow could lead to exhaustion 945 of the available bandwidth for that flow if the routers attribute 946 these false messages to the resource budget of that flow. 948 In a multipath scenario, injected messages will cause increased 949 processor utilization in elimination routers. If enough paths are 950 subject to malicious injection, the legitimate messages can be 951 dropped. Likewise it can cause an increase in buffer usage. In 952 total, it will consume more resources in the routers than normal, 953 giving rise to a resource exhaustion attack on the routers. 955 If a DetNet flow is interrupted, the end application will be affected 956 by what is now a non-deterministic flow. 958 6.3.2. Controller Plane Segmentation 960 In a successful controller plane segmentation attack, control 961 messages are acted on by nodes in the network, unbeknownst to the 962 central controller or the network engineer. This has the potential 963 to: 965 o create new DetNet flows (exhausting resources) 967 o drop existing DetNet flows (denial of service) 969 o add end-stations to a multicast group (loss of privacy) 971 o remove end-stations from a multicast group (reduction of service) 972 o modify the DetNet flow attributes (affecting available bandwidth) 974 6.4. Replication and Elimination 976 The Replication and Elimination is relevant only to data plane 977 messages as controller plane messages are not subject to multipath 978 routing. 980 6.4.1. Increased Attack Surface 982 Covered briefly in Section 6.3, Segmentation Attacks. 984 6.4.2. Header Manipulation at Elimination Routers 986 Covered briefly in Section 6.3, Segmentation Attacks. 988 6.5. Control or Signaling Packet Modification 990 If control packets are subject to manipulation undetected, the 991 network can be severely compromised. 993 6.6. Control or Signaling Packet Injection 995 If an attacker can inject control packets undetected, the network can 996 be severely compromised. 998 6.7. Reconnaissance 1000 Of all the attacks, this is one of the most difficult to detect and 1001 counter. Often, an attacker will start out by observing the traffic 1002 going through the network and use the knowledge gathered in this 1003 phase to mount future attacks. 1005 The attacker can, at their leisure, observe over time all aspects of 1006 the messaging and signalling, learning the intent and purpose of all 1007 traffic flows. At some later date, possibly at an important time in 1008 an operational context, the attacker can launch a multi-faceted 1009 attack, possibly in conjunction with some demand for ransom. 1011 The flow-id in the header of the data plane messages gives an 1012 attacker a very reliable identifier for DetNet traffic, and this 1013 traffic has a high probability of going to lucrative targets. 1015 Applications which are ported from a private OT network to the higher 1016 visibility DetNet environment may need to be adapted to limit 1017 distinctive flow properties that could make them susceptible to 1018 reconnaissance. 1020 6.8. Attacks on Time Synchronization Mechanisms 1022 Attacks on time synchronization mechanisms are addressed in 1023 [RFC7384]. 1025 6.9. Attacks on Path Choice 1027 This is covered in part in Section 6.3, Segmentation Attacks, and as 1028 with Replication and Elimination ( Section 6.4), this is relevant for 1029 DataPlane messages. 1031 7. Security Threat Mitigation 1033 This section describes a set of measures that can be taken to 1034 mitigate the attacks described in Section 5, Security Threats. These 1035 mitigations should be viewed as a toolset that includes several 1036 different and diverse tools. Each application or system will 1037 typically use a subset of these tools, based on a system-specific 1038 threat analysis. 1040 Some of the technology-specific security considerations and 1041 mitigation approaches are further discussed in the DETNET data plane 1042 solution documents, such as [RFC8939], [RFC8938], 1043 [I-D.ietf-detnet-mpls-over-udp-ip], and 1044 [I-D.ietf-detnet-ip-over-mpls]. 1046 7.1. Path Redundancy 1048 Description 1050 A DetNet flow that can be forwarded simultaneously over multiple 1051 paths. Path replication and elimination [RFC8655] provides 1052 resiliency to dropped or delayed packets. This redundancy 1053 improves the robustness to failures and to on-path attacks. Note: 1054 At the time of this writing, PREOF is not defined for the IP data 1055 plane. 1057 Related attacks 1059 Path redundancy can be used to mitigate various on-path attacks, 1060 including attacks described in Section 5.2.1, Section 5.2.2, 1061 Section 5.2.3, and Section 5.2.7. However it is also possible 1062 that multiple paths may make it more difficult to locate the 1063 source of an on-path attacker. 1065 A delay modulation attack could result in extensively exercising 1066 parts of the code that wouldn't normally be extensively exercised 1067 and thus might expose flaws in the system that might otherwise not 1068 be exposed. 1070 7.2. Integrity Protection 1072 Description 1074 Integrity Protection in the scope of DetNet is the ability to 1075 detect if a header has been modified (either maliciously or by 1076 chance) and propagate a warning to a responsible monitoring agent. 1077 An integrity protection mechanism is designed to counteract header 1078 modification attacks where a Message Authentication Code (MAC) is 1079 the most common. The MAC can be distributed either in-line 1080 (included in the same packet) or via a side channel. Due to the 1081 nature of DetNet traffic. Note: a sideband approach may yield too 1082 high overhead and complexity and should only be used as a very 1083 last resort if in-line approaches are not viable. 1085 There are different levels of security available for integrity 1086 protection, ranging from the basic ability to detect if a header 1087 has been corrupted in transit (no malicious attack) to stopping a 1088 skilled and determined attacker capable of both subtly modifying 1089 fields in the headers as well as updating an unsigned MAC. Common 1090 for all are the 2 steps that need to be performed in both ends. 1091 The first is computing the checksum or MAC. The corresponding 1092 verification step must perform the same steps before comparing the 1093 provided with the computed value. Only then can the receiver be 1094 reasonably sure that the header is authentic. 1096 The most basic protection mechanism consists of computing a simple 1097 checksum of the header fields and provide it to the next entity in 1098 the packets path for verification. Using a MAC combined with a 1099 secret key provides the best protection against modification and 1100 replication attacks (see Section 5.2.2 and Section 5.2.4). This 1101 MAC usage needs to be part of a security association that is 1102 established and managed by a security association protocol (such 1103 as IKEv2 for IPsec security associations). Integrity protection 1104 in the controller plane is discussed in Section 7.6. The secret 1105 key, regardless of MAC used, must be protected from falling into 1106 the hands of unauthorized users. 1108 DetNet system- and/or component- level designers need to be aware 1109 of these distinctions and enforce appropriate integrity protection 1110 mechanisms as needed based on a threat analysis. Note that adding 1111 integrity protection mechanisms may introduce latency, thus many 1112 of the same considerations in Section 7.5.1 also apply here. 1114 Packet Sequence Number Integrity Considerations 1115 The use of PREOF in a DetNet implementation implies the use of a 1116 sequence number for each packet. There is a trust relationship 1117 between the component that adds the sequence number and the 1118 component that removes the sequence number. The sequence number 1119 may be end-to-end source to destination, or may be added/deleted 1120 by network edge components. The adder and remover(s) have the 1121 trust relationship because they are the ones that ensure that the 1122 sequence numbers are not modifiable. Thus, sequence numbers can 1123 be protected by using encryption, or by a MAC without using 1124 encryption. Between the adder and remover there may or may not be 1125 replication and elimination functions. The elimination functions 1126 must be able to see the sequence numbers. Therefore, if 1127 encryption is done between adders and removers it must not obscure 1128 the sequence number. If the sequence removers and the eliminators 1129 are in the same physical component, it may be possible to obscure 1130 the sequence number, however that is a layer violation, and is not 1131 recommended practice. Note: At the time of this writing, PREOF is 1132 not defined for the IP data plane. 1134 Related attacks 1136 Integrity protection mitigates attacks related to modification and 1137 tampering, including the attacks described in Section 5.2.2 and 1138 Section 5.2.4. 1140 7.3. DetNet Node Authentication 1142 Description 1144 Authentication verifies the identity of DetNet nodes (including 1145 DetNet Controller Plane nodes), and this enables mitigation of 1146 spoofing attacks. While integrity protection ( Section 7.2) 1147 prevents intermediate nodes from modifying information, 1148 authentication (such as IPsec [RFC4301] or MACsec 1149 [IEEE802.1AE-2018]) can provide traffic origin verification, i.e. 1150 to verify that each packet in a DetNet flow is from a known 1151 source. 1153 Related attacks 1155 DetNet node authentication is used to mitigate attacks related to 1156 spoofing, including the attacks of Section 5.2.2, and 1157 Section 5.2.4. 1159 7.4. Dummy Traffic Insertion 1161 Description 1163 With some queueing methods such as [IEEE802.1Qch-2017] it is 1164 possible to introduce dummy traffic in order to regularize the 1165 timing of packet transmission. 1167 Related attacks 1169 Removing distinctive temporal properties of individual packets or 1170 flows can be used to mitigate against reconnaissance attacks 1171 Section 5.2.6. For example, dummy traffic can be used to 1172 synthetically maintain constant traffic rate even when no user 1173 data is transmitted, thus making it difficult to collect 1174 information about the times at which users are active, and the 1175 times at which DETNET flows are added or removed. 1177 7.5. Encryption 1179 Description 1181 Reconnaissance attacks (Section 5.2.6) can be mitigated by using 1182 encryption. Specific encryption protocols will depend on the 1183 lower layers that DetNet is forwarded over. For example, IP flows 1184 may be forwarded over IPsec [RFC4301], and Ethernet flows may be 1185 secured using MACsec [IEEE802.1AE-2018]. 1187 DetNet nodes do not have any need to inspect the payload of any 1188 DetNet packets, making them data-agnostic. This means that end- 1189 to-end encryption at the application layer is an acceptable way to 1190 protect user data. 1192 Note that reconnaissance is a threat that is not specific to 1193 DetNet flows, and therefore reconnaissance mitigation will 1194 typically be analyzed and addressed by a network operator 1195 regardless of whether DetNet flows are deployed. Thus, encryption 1196 requirements will typically not be defined in DetNet technology- 1197 specific specifications, but considerations of using DetNet in 1198 encrypted environments will be discussed in these specifications. 1199 For example, Section 5.1.2.3. of [RFC8939] discusses flow 1200 identification of DetNet flows running over IPsec. 1202 Related attacks 1204 As noted above, encryption can be used to mitigate reconnaissance 1205 attacks ( Section 5.2.6). However, for a DetNet to provide 1206 differentiated quality of service on a flow-by-flow basis, the 1207 network must be able to identify the flows individually. This 1208 implies that in a reconnaissance attack the attacker may also be 1209 able to track individual flows to learn more about the system. 1211 7.5.1. Encryption Considerations for DetNet 1213 Any compute time which is required for encryption and decryption 1214 processing ('crypto') must be included in the flow latency 1215 calculations. Thus, crypto algorithms used in a DetNet must have 1216 bounded worst-case execution times, and these values must be used in 1217 the latency calculations. 1219 Some crypto algorithms are symmetric in encode/decode time (such as 1220 AES) and others are asymmetric (such as public key algorithms). 1221 There are advantages and disadvantages to the use of either type in a 1222 given DetNet context. The discussion in this document relates to the 1223 timing implications of crypto for DetNet; it is assumed that 1224 integrity considerations are covered elsewhere in the literature. 1226 Asymmetrical crypto is typically not used in networks on a packet-by- 1227 packet basis due to its computational cost. For example, if only 1228 endpoint checks or checks at a small number of intermediate points 1229 are required, asymmetric crypto can be used to authenticate 1230 distribution or exchange of a secret symmetric crypto key; a 1231 successful check based on that key will provide traffic origin 1232 verification, as long as the key is kept secret by the participants. 1233 TLS (v1.3 [RFC8446], in particular section 4.1 "Key exchange") and 1234 IKEv2 [RFC6071]) are examples of this for endpoint checks. 1236 However, if secret symmetric keys are used for this purpose the key 1237 must be given to all relays, which increases the probability of a 1238 secret key being leaked. Also, if any relay is compromised or faulty 1239 then it may inject traffic into the flow. Group key management 1240 protocols can be used to automate management of such symmetric keys; 1241 for an example in the context of IPsec, see 1242 [I-D.ietf-ipsecme-g-ikev2]. 1244 Alternatively, asymmetric crypto can provide traffic origin 1245 verification at every intermediate node. For example, a DetNet flow 1246 can be associated with an (asymmetric) keypair, such that the private 1247 key is available to the source of the flow and the public key is 1248 distributed with the flow information, allowing verification at every 1249 node for every packet. However, this is more computationally 1250 expensive. 1252 In either case, origin verification also requires replay detection as 1253 part of the security protocol to prevent an attacker from recording 1254 and resending traffic, e.g., as a denial of service attack on flow 1255 forwarding resources. 1257 If crypto keys are to be regenerated over the duration of the flow 1258 then the time required to accomplish this must be accounted for in 1259 the latency calculations. 1261 7.6. Control and Signaling Message Protection 1263 Description 1265 Control and signaling messages can be protected through the use of 1266 any or all of encryption, authentication, and integrity protection 1267 mechanisms. 1269 Related attacks 1271 These mechanisms can be used to mitigate various attacks on the 1272 controller plane, as described in Section 5.2.5, Section 5.2.7 and 1273 Section 5.2.5.1. 1275 7.7. Dynamic Performance Analytics 1277 Description 1279 Incorporating Dynamic Performance Analytics ("DPA") implies that 1280 the DetNet design includes a performance monitoring system to 1281 validate that timing guarantees are being met and to detect timing 1282 violations or other anomalies that may be the symptom of a 1283 security attack or system malfunction. If this monitoring system 1284 detects unexpected behavior, it must then cause action to be 1285 initiated to address the situation in an appropriate and timely 1286 manner, either at the data plane or controller plane, or both in 1287 concert. 1289 The overall DPA system can thus be decomposed into the "detection" 1290 and "notification" functions. Although the time-specific DPA 1291 performance indicators and their implementation will likely be 1292 specific to a given DetNet, and as such are nascent technology at 1293 the time of this writing, DPA is commonly used in existing 1294 networks so we can make some observations on how such a system 1295 might be implemented for a DetNet, given that it would need to be 1296 adapted to address the time-specific performance indicators. 1298 Detection Mechanisms 1300 Measurement of timing performance can be done via "passive" or 1301 "active" monitoring, as discussed below. 1303 Examples of passive monitoring strategies include 1305 * Monitoring of queue and buffer levels, e.g. via Active Queue 1306 Management (e.g. [RFC7567] 1308 * Monitoring of per-flow counters 1310 * Measurement of link statistics such as traffic volume, 1311 bandwidth, and QoS 1313 * Detection of dropped packets 1315 * Use of commercially available Network Monitoring tools 1317 Examples of active monitoring include 1319 * In-band timing measurements (such as packet arrival times) e.g. 1320 by timestamping and packet inspection 1322 * Use of OAM. For DetNet-specific OAM considerations see 1323 [I-D.ietf-detnet-ip-oam], [I-D.ietf-detnet-mpls-oam]. Note: At 1324 the time of this writing, specifics of DPA have not been 1325 developed for the DetNet OAM, but could be a subject for future 1326 investigation 1328 * For OAM for Ethernet specifically, see also Connectivity Fault 1329 Management (CFM, [IEEE802.1Q]) which defines protocols and 1330 practices for OAM for paths through 802.1 bridges and LANs 1332 * Out-of-band detection. following the data path or parts of a 1333 data path, for example Bidirectional Forwarding Detection (BFD, 1334 e.g. [RFC5880]) 1336 Note that for some measurements (e.g. packet delay) it may be 1337 necessary to make and reconcile measurements from more than one 1338 physical location (e.g. a source and destination), possibly in 1339 both directions, in order to arrive at a given performance 1340 indicator value. 1342 Notification Mechanisms 1344 Making DPA measurement results available at the right place(s) and 1345 time(s) to effect timely response can be challenging. Two 1346 notification mechanisms that are in general use are Netconf/YANG 1347 Notifications (e.g. [RFC5880]) and the proprietary local 1348 telemetry interfaces provided with components from some vendors. 1350 At the time of this writing YANG Notifications are not addressed 1351 by the DetNet YANG drafts, however this may be a topic for future 1352 work. It is possible that some of the passive mechanisms could be 1353 covered by notifications from non-DetNet-specific YANG modules; 1354 for example if there is OAM or other performance monitoring that 1355 can monitor delay bounds then that could have its own associated 1356 YANG model which could be relevant to DetNet, for example some 1357 "threshold" values for timing measurement notifications. 1359 At the time of this writing there is an IETF Working Group for 1360 network/performance monitoring (IP Performance Measurement, ippm). 1361 See also previous work by the completed Remote Network Monitoring 1362 Working Group (rmonmib). See also [RFC6632], An Overview of the 1363 IETF Network Management Standards. 1365 Vendor-specific local telemetry may be available on some 1366 commercially available systems, whereby the system can be 1367 programmed (via a proprietary dedicated port and API) to monitor 1368 and report on specific conditions, based on both passive and 1369 active measurements. 1371 Related attacks 1373 Performance analytics can be used to mitigate various attacks, 1374 including the ones described in Section 5.2.1 (Delay Attack), 1375 Section 5.2.3 (Resource Segmentation Attack), and Section 5.2.7 1376 (Time Synchronization Attack). 1378 For example, in the case of data plane delay attacks, one possible 1379 mitigation is to timestamp the data at the source, and timestamp 1380 it again at the destination, and if the resulting latency exceeds 1381 the promised bound, take appropriate action. Note that DetNet 1382 specifies packet sequence numbering, however it does not specify 1383 use of packet timestamps, although they may be used by the 1384 underlying transport (for example TSN, [IEEE802.1BA]) to provide 1385 the service. 1387 7.8. Mitigation Summary 1389 The following table maps the attacks of Section 5, Security Threats, 1390 to the impacts of Section 6, Security Threat Impacts, and to the 1391 mitigations of the current section. Each row specifies an attack, 1392 the impact of this attack if it is successfully implemented, and 1393 possible mitigation methods. 1395 +----------------------+---------------------+---------------------+ 1396 | Attack | Impact | Mitigations | 1397 +----------------------+---------------------+---------------------+ 1398 |Delay Attack |-Non-deterministic |-Path redundancy | 1399 | | delay |-Performance | 1400 | |-Data disruption | analytics | 1401 | |-Increased resource | | 1402 | | consumption | | 1403 +----------------------+---------------------+---------------------+ 1404 |Reconnaissance |-Enabler for other |-Encryption | 1405 | | attacks |-Dummy traffic | 1406 | | | insertion | 1407 +----------------------+---------------------+---------------------+ 1408 |DetNet Flow Modificat-|-Increased resource |-Path redundancy | 1409 |ion or Spoofing | consumption |-Integrity protection| 1410 | |-Data disruption |-DetNet Node | 1411 | | | authentication | 1412 +----------------------+---------------------+---------------------+ 1413 |Inter-Segment Attack |-Increased resource |-Path redundancy | 1414 | | consumption |-Performance | 1415 | |-Data disruption | analytics | 1416 +----------------------+---------------------+---------------------+ 1417 |Replication: Increased|-All impacts of other|-Integrity protection| 1418 |attack surface | attacks |-DetNet Node | 1419 | | | authentication | 1420 +----------------------+---------------------+---------------------+ 1421 |Replication-related |-Non-deterministic |-Integrity protection| 1422 |Header Manipulation | delay |-DetNet Node | 1423 | |-Data disruption | authentication | 1424 +----------------------+---------------------+---------------------+ 1425 |Path Manipulation |-Enabler for other |-Control message | 1426 | | attacks | protection | 1427 +----------------------+---------------------+---------------------+ 1428 |Path Choice: Increased|-All impacts of other|-Control message | 1429 |Attack Surface | attacks | protection | 1430 +----------------------+---------------------+---------------------+ 1431 |Control or Signaling |-Increased resource |-Control message | 1432 |Packet Modification | consumption | protection | 1433 | |-Non-deterministic | | 1434 | | delay | | 1435 | |-Data disruption | | 1436 +----------------------+---------------------+---------------------+ 1437 |Control or Signaling |-Increased resource |-Control message | 1438 |Packet Injection | consumption | protection | 1439 | |-Non-deterministic | | 1440 | | delay | | 1441 | |-Data disruption | | 1442 +----------------------+---------------------+---------------------+ 1443 |Attacks on Time |-Non-deterministic |-Path redundancy | 1444 |Synchronization | delay |-Control message | 1445 |Mechanisms |-Increased resource | protection | 1446 | | consumption |-Performance | 1447 | |-Data disruption | analytics | 1448 +----------------------+---------------------+---------------------+ 1450 Figure 3: Mapping Attacks to Impact and Mitigations 1452 8. Association of Attacks to Use Cases 1454 Different attacks can have different impact and/or mitigation 1455 depending on the use case, so we would like to make this association 1456 in our analysis. However since there is a potentially unbounded list 1457 of use cases, we categorize the attacks with respect to the common 1458 themes of the use cases as identified in the Use Case Common Themes 1459 section of the DetNet Use Cases [RFC8578]. 1461 See also Figure 2 for a mapping of the impact of attacks per use case 1462 by industry. 1464 8.1. Association of Attacks to Use Case Common Themes 1466 In this section we review each theme and discuss the attacks that are 1467 applicable to that theme, as well as anything specific about the 1468 impact and mitigations for that attack with respect to that theme. 1469 The table Figure 5, Mapping Between Themes and Attacks, then provides 1470 a summary of the attacks that are applicable to each theme. 1472 8.1.1. Sub-Network Layer 1474 DetNet is expected to run over various transmission mediums, with 1475 Ethernet being the first identified. Attacks such as Delay or 1476 Reconnaissance might be implemented differently on a different 1477 transmission medium, however the impact on the DetNet as a whole 1478 would be essentially the same. We thus conclude that all attacks and 1479 impacts that would be applicable to DetNet over Ethernet (i.e. all 1480 those named in this document) would also be applicable to DetNet over 1481 other transmission mediums. 1483 With respect to mitigations, some methods are specific to the 1484 Ethernet medium, for example time-aware scheduling using 802.1Qbv 1485 [IEEE802.1Qbv-2015] can protect against excessive use of bandwidth at 1486 the ingress - for other mediums, other mitigations would have to be 1487 implemented to provide analogous protection. 1489 8.1.2. Central Administration 1491 A DetNet network can be controlled by a centralized network 1492 configuration and control system. Such a system may be in a single 1493 central location, or it may be distributed across multiple control 1494 entities that function together as a unified control system for the 1495 network. 1497 All attacks named in this document which are relevant to controller 1498 plane packets (and the controller itself) are relevant to this theme, 1499 including Path Manipulation, Path Choice, Control Packet Modification 1500 or Injection, Reconaissance and Attacks on Time Synchronization 1501 Mechanisms. 1503 8.1.3. Hot Swap 1505 A DetNet network is not expected to be "plug and play" - it is 1506 expected that there is some centralized network configuration and 1507 control system. However, the ability to "hot swap" components (e.g. 1508 due to malfunction) is similar enough to "plug and play" that this 1509 kind of behavior may be expected in DetNet networks, depending on the 1510 implementation. 1512 An attack surface related to Hot Swap is that the DetNet network must 1513 at least consider input at runtime from components that were not part 1514 of the initial configuration of the network. Even a "perfect" (or 1515 "hitless") replacement of a component at runtime would not 1516 necessarily be ideal, since presumably one would want to distinguish 1517 it from the original for OAM purposes (e.g. to report hot swap of a 1518 failed component). 1520 This implies that an attack such as Flow Modification, Spoofing or 1521 Inter-segment (which could introduce packets from a "new" component, 1522 i.e. one heretofore unknown on the network) could be used to exploit 1523 the need to consider such packets (as opposed to rejecting them out 1524 of hand as one would do if one did not have to consider introduction 1525 of a new component). 1527 To mitigate this situation, deployments should provide a method for 1528 dynamic and secure registration of new components, and (possibly 1529 manual) deregistration of retired components. This would avoid the 1530 situation in which the network must accommodate potentially insecure 1531 packet flows from unknown components. 1533 Similarly if the network was designed to support runtime replacement 1534 of a clock component, then presence (or apparent presence) and thus 1535 consideration of packets from a new such component could affect the 1536 network, or the time synchronization of the network, for example by 1537 initiating a new Best Master Clock selection process. These types of 1538 attacks should therefore be considered when designing hot swap type 1539 functionality (see [RFC7384]). 1541 8.1.4. Data Flow Information Models 1543 DetNet specifies new YANG models which may present new attack 1544 surfaces. Per IETF guidelines, security considerations for any YANG 1545 model are expected to be part of the YANG model specification, as 1546 described in [IETF_YANG_SEC]. 1548 8.1.5. L2 and L3 Integration 1550 A DetNet network integrates Layer 2 (bridged) networks (e.g. AVB/TSN 1551 LAN) and Layer 3 (routed) networks (e.g. IP) via the use of well- 1552 known protocols such as IP, MPLS Pseudowire, and Ethernet. Various 1553 DetNet drafts address many specific aspects of Layer 2 and Layer 3 1554 integration within a DetNet, and these are not individually 1555 referenced here; security considerations for those aspects are 1556 covered within those drafts or within the related subsections of the 1557 present document. 1559 Please note that although there are no entries in the L2 and L3 1560 Integration line of the Mapping Between Themes and Attacks table 1561 Figure 4, this does not imply that there could be no relevant attacks 1562 related to L2-L3 integration. 1564 8.1.6. End-to-End Delivery 1566 Packets sent over DetNet are not to be dropped by the network due to 1567 congestion. (Packets may however intentionally be dropped for 1568 intended reasons, e.g. per security measures). 1570 A data plane attack may force packets to be dropped, for example a 1571 "long" Delay or Replication/Elimination or Flow Modification attack. 1573 The same result might be obtained by a controller plane attack, e.g. 1574 Path Manipulation or Signaling Packet Modification. 1576 It may be that such attacks are limited to Internal on-path 1577 attackers, but other possibilities should be considered. 1579 An attack may also cause packets that should not be delivered to be 1580 delivered, such as by forcing packets from one (e.g. replicated) path 1581 to be preferred over another path when they should not be 1582 (Replication attack), or by Flow Modification, or by Path Choice or 1583 Packet Injection. A Time Synchronization attack could cause a system 1584 that was expecting certain packets at certain times to accept 1585 unintended packets based on compromised system time or time windowing 1586 in the scheduler. 1588 8.1.7. Replacement for Proprietary Fieldbuses and Ethernet-based 1589 Networks 1591 There are many proprietary "field buses" used in Industrial and other 1592 industries, as well as proprietary non-interoperable deterministic 1593 Ethernet-based networks. DetNet is intended to provide an open- 1594 standards-based alternative to such buses/networks. In cases where a 1595 DetNet intersects with such fieldbuses/networks or their protocols, 1596 such as by protocol emulation or access via a gateway, new attack 1597 surfaces can be opened. 1599 For example an Inter-Segment or Controller plane attack such as Path 1600 Manipulation, Path Choice or Control Packet Modification/Injection 1601 could be used to exploit commands specific to such a protocol, or 1602 that are interpreted differently by the different protocols or 1603 gateway. 1605 8.1.8. Deterministic vs Best-Effort Traffic 1607 Most of the themes described in this document address OT (reserved) 1608 DetNet flows - this item is intended to address issues related to IT 1609 traffic on a DetNet. 1611 DetNet is intended to support coexistence of time-sensitive 1612 operational (OT, deterministic) traffic and information (IT, "best 1613 effort") traffic on the same ("unified") network. 1615 With DetNet, this coexistance will become more common, and 1616 mitigations will need to be established. The fact that the IT 1617 traffic on a DetNet is limited to a corporate controlled network 1618 makes this a less difficult problem compared to being exposed to the 1619 open Internet, however this aspect of DetNet security should not be 1620 underestimated. 1622 An Inter-segment attack can flood the network with IT-type traffic 1623 with the intent of disrupting handling of IT traffic, and/or the goal 1624 of interfering with OT traffic. Presumably if the DetNet flow 1625 reservation and isolation of the DetNet is well-designed (better- 1626 designed than the attack) then interference with OT traffic should 1627 not result from an attack that floods the network with IT traffic. 1629 However the handling of IT traffic by the DetNet may not (by design) 1630 be as resilient to DOS attack, and thus designers must be otherwise 1631 prepared to mitigate DOS attacks on IT traffic in a DetNet. 1633 The network design as a whole also needs to consider possible 1634 application-level dependencies of "OT"-type applications on services 1635 provided by the "IT part" of the network; for example, does the OT 1636 application depend on IT network services such as DNS or OAM? If 1637 such dependencies exist, how are malicious packet flows handled? 1638 Such considerations are typically outside the scope of DetNet proper, 1639 but nonetheless need to be addressed in the overall DetNet network 1640 design for a given use case. 1642 8.1.9. Deterministic Flows 1644 Reserved bandwidth data flows (deterministic flows) must provide the 1645 allocated bandwidth, and must be isolated from each other. 1647 A Spoofing or Inter-segment attack which adds packet traffic to a 1648 bandwidth-reserved DetNet flow could cause that flow to occupy more 1649 bandwidth than it was allocated, resulting in interference with other 1650 DetNet flows. 1652 A Flow Modification or Spoofing or Header Manipulation or Control 1653 Packet Modification attack could cause packets from one flow to be 1654 directed to another flow, thus breaching isolation between the flows. 1656 8.1.10. Unused Reserved Bandwidth 1658 If bandwidth reservations are made for a DetNet flow but the 1659 associated bandwidth is not used at any point in time, that bandwidth 1660 is made available on the network for best-effort traffic. However, 1661 note that security considerations for best-effort traffic on a DetNet 1662 network is out of scope of the present document, provided that such 1663 an attack does not affect performance for DetNet OT traffic. 1665 8.1.11. Interoperability 1667 The DetNet network specifications are intended to enable an ecosystem 1668 in which multiple vendors can create interoperable products, thus 1669 promoting component diversity and potentially higher numbers of each 1670 component manufactured. 1672 The security mechanisms and protocols that are discussed in this 1673 document also require interoperability. It is expected that DETNET 1674 network specifications that define security measures and protocols 1675 will be defined in a way that allows interoperability. 1677 Given that the DetNet specifications are unambiguously written and 1678 that the implementations are accurate, then this should not in and of 1679 itself cause a security concern; however, in the real world, it could 1680 be. The network operator can mitigate this through sufficient 1681 interoperability testing. 1683 8.1.12. Cost Reductions 1685 The DetNet network specifications are intended to enable an ecosystem 1686 in which multiple vendors can create interoperable products, thus 1687 promoting higher numbers of each component manufactured, promoting 1688 cost reduction and cost competition among vendors. 1690 This envisioned breadth of DetNet-enabled products is in general a 1691 positive factor, however implementation flaws in any individual 1692 component can present an attack surface. In addition, implementation 1693 differences between components from different vendors can result in 1694 attack surfaces (resulting from their interaction) which may not 1695 exist in any individual component. 1697 Network operators can mitigate such concerns through sufficient 1698 product and interoperability testing. 1700 8.1.13. Insufficiently Secure Components 1702 The DetNet network specifications are intended to enable an ecosystem 1703 in which multiple vendors can create interoperable products, thus 1704 promoting component diversity and potentially higher numbers of each 1705 component manufactured. However this raises the possibility that a 1706 vendor might repurpose for DetNet applications a hardware or software 1707 component that was originally designed for operation in an isolated 1708 OT network, and thus may not have been designed to be sufficiently 1709 secure, or secure at all. Deployment of such a component on a DetNet 1710 network that is intended to be highly secure may present an attack 1711 surface. 1713 The DetNet network operator may need to take specific actions to 1714 protect such components, such as implementing a dedicated security 1715 layer around the component. 1717 8.1.14. DetNet Network Size 1719 DetNet networks range in size from very small, e.g. inside a single 1720 industrial machine, to very large, for example a Utility Grid network 1721 spanning a whole country. 1723 The size of the network might be related to how the attack is 1724 introduced into the network, for example if the entire network is 1725 local, there is a threat that power can be cut to the entire network. 1726 If the network is large, perhaps only a part of the network is 1727 attacked. 1729 A Delay attack might be as relevant to a small network as to a large 1730 network, although the amount of delay might be different. 1732 Attacks sourced from IT traffic might be more likely in large 1733 networks, since more people might have access to the network, 1734 presenting a larger attack surface. Similarly Path Manipulation, 1735 Path Choice and Time Synchronization attacks seem more likely 1736 relevant to large networks. 1738 8.1.15. Multiple Hops 1740 Large DetNet networks (e.g. a Utility Grid network) may involve many 1741 "hops" over various kinds of links for example radio repeaters, 1742 microwave links, fiber optic links, etc. 1744 An attack that takes advantage of flaws (or even normal operation) in 1745 the device drivers for the various links (through internal knowledge 1746 of how the individual driver or firmware operates) could take 1747 proportionately greater advantage of this topology. 1749 It is also possible that this DetNet topology will not be in as 1750 common use as other more homogeneous topologies so there may be more 1751 opportunity for attackers to exploit software and/or protocol flaws 1752 in the implementations which have not been tested through extensive 1753 use, particularly in the case of early adopters. 1755 Of the attacks we have defined, the ones identified in Section 8.1.14 1756 as germane to large networks are the most relevant. 1758 8.1.16. Level of Service 1760 A DetNet is expected to provide means to configure the network that 1761 include querying network path latency, requesting bounded latency for 1762 a given DetNet flow, requesting worst case maximum and/or minimum 1763 latency for a given path or DetNet flow, and so on. It is an 1764 expected case that the network cannot provide a given requested 1765 service level. In such cases the network control system should reply 1766 that the requested service level is not available (as opposed to 1767 accepting the parameter but then not delivering the desired 1768 behavior). 1770 Controller plane attacks such as Signaling Packet Modification and 1771 Injection could be used to modify or create control traffic that 1772 could interfere with the process of a user requesting a level of 1773 service and/or the reply from the network. 1775 Reconnaissance could be used to characterize flows and perhaps target 1776 specific flows for attack via the controller plane as noted in 1777 Section 6.7. 1779 8.1.17. Bounded Latency 1781 DetNet provides the expectation of guaranteed bounded latency. 1783 Delay attacks can cause packets to miss their agreed-upon latency 1784 boundaries. 1786 Time Synchronization attacks can corrupt the time reference of the 1787 system, resulting in missed latency deadlines (with respect to the 1788 "correct" time reference). 1790 8.1.18. Low Latency 1792 Applications may require "extremely low latency" however depending on 1793 the application these may mean very different latency values; for 1794 example "low latency" across a Utility grid network is on a different 1795 time scale than "low latency" in a motor control loop in a small 1796 machine. The intent is that the mechanisms for specifying desired 1797 latency include wide ranges, and that architecturally there is 1798 nothing to prevent arbitrarily low latencies from being implemented 1799 in a given network. 1801 Attacks on the controller plane (as described in the Level of Service 1802 theme Section 8.1.16) and Delay and Time attacks (as described in the 1803 Bounded Latency theme Section 8.1.17) both apply here. 1805 8.1.19. Bounded Jitter (Latency Variation) 1807 DetNet is expected to provide bounded jitter (packet to packet 1808 latency variation). 1810 Delay attacks can cause packets to vary in their arrival times, 1811 resulting in packet to packet latency variation, thereby violating 1812 the jitter specification. 1814 8.1.20. Symmetrical Path Delays 1816 Some applications would like to specify that the transit delay time 1817 values be equal for both the transmit and return paths. 1819 Delay attacks can cause path delays to materially differ between 1820 paths. 1822 Time Synchronization attacks can corrupt the time reference of the 1823 system, resulting in path delays that may be perceived to be 1824 different (with respect to the "correct" time reference) even if they 1825 are not materially different. 1827 8.1.21. Reliability and Availability 1829 DetNet based systems are expected to be implemented with essentially 1830 arbitrarily high availability (for example 99.9999% up time, or even 1831 12 nines). The intent is that the DetNet designs should not make any 1832 assumptions about the level of reliability and availability that may 1833 be required of a given system, and should define parameters for 1834 communicating these kinds of metrics within the network. 1836 Any attack on the system, of any type, can affect its overall 1837 reliability and availability, thus in the mapping table Figure 4 we 1838 have marked every attack. Since every DetNet depends to a greater or 1839 lesser degree on reliability and availability, this essentially means 1840 that all networks have to mitigate all attacks, which to a greater or 1841 lesser degree defeats the purpose of associating attacks with use 1842 cases. It also underscores the difficulty of designing "extremely 1843 high reliability" networks. 1845 In practice, network designers can adopt a risk-based approach, in 1846 which only those attacks are mitigated whose potential cost is higher 1847 than the cost of mitigation. 1849 8.1.22. Redundant Paths 1851 DetNet based systems are expected to be implemented with essentially 1852 arbitrarily high reliability/availability. A strategy used by DetNet 1853 for providing such extraordinarily high levels of reliability is to 1854 provide redundant paths that can be seamlessly switched between, all 1855 the while maintaining the required performance of that system. 1857 Replication-related attacks are by definition applicable here. 1858 Controller plane attacks can also interfere with the configuration of 1859 redundant paths. 1861 8.1.23. Security Measures 1863 A DetNet network must be made sufficiently secure against problematic 1864 component or traffic behavior, whether malicious or incidental, and 1865 whether affecting a single component or multiple components. If any 1866 of the security mechanisms which protect the DetNet from such 1867 problems are attacked or subverted, this can result in malfunction of 1868 the network. Thus the design of the security system itself needs to 1869 be robust against attacks. 1871 The general topic of protection of security mechanisms is not unique 1872 to DetNet; it is identical to the case of securing any security 1873 mechanism for any network. This document addresses these concerns 1874 only to the extent that they are unique to DetNet. 1876 8.2. Summary of Attack Types per Use Case Common Theme 1878 The List of Attacks table Figure 4 lists the attacks of Section 5, 1879 Security Threats, assigning a number to each type of attack. That 1880 number is then used as a short form identifier for the attack in 1881 Figure 5, Mapping Between Themes and Attacks. 1883 +----+-------------------------------------------+ 1884 | | Attack | 1885 +----+-------------------------------------------+ 1886 | 1 |Delay Attack | 1887 +----+-------------------------------------------+ 1888 | 2 |DetNet Flow Modification or Spoofing | 1889 +----+-------------------------------------------+ 1890 | 3 |Inter-Segment Attack | 1891 +----+-------------------------------------------+ 1892 | 4 |Replication: Increased attack surface | 1893 +----+-------------------------------------------+ 1894 | 5 |Replication-related Header Manipulation | 1895 +----+-------------------------------------------+ 1896 | 6 |Path Manipulation | 1897 +----+-------------------------------------------+ 1898 | 7 |Path Choice: Increased Attack Surface | 1899 +----+-------------------------------------------+ 1900 | 8 |Control or Signaling Packet Modification | 1901 +----+-------------------------------------------+ 1902 | 9 |Control or Signaling Packet Injection | 1903 +----+-------------------------------------------+ 1904 | 10 |Reconnaissance | 1905 +----+-------------------------------------------+ 1906 | 11 |Attacks on Time Synchronization Mechanisms | 1907 +----+-------------------------------------------+ 1909 Figure 4: List of Attacks 1911 The Mapping Between Themes and Attacks table Figure 5maps the use 1912 case themes of [RFC8578] (as also enumerated in this document) to the 1913 attacks of Figure 4. Each row specifies a theme, and the attacks 1914 relevant to this theme are marked with a '+'. The row items which 1915 have no threats associated with them are included in the table for 1916 completeness of the list of Use Case Common Themes, and do not have 1917 DetNet-specific threats associated with them. 1919 +----------------------------+--------------------------------+ 1920 | Theme | Attack | 1921 | +--+--+--+--+--+--+--+--+--+--+--+ 1922 | | 1| 2| 3| 4| 5| 6| 7| 8| 9|10|11| 1923 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1924 |Network Layer - AVB/TSN Eth.| +| +| +| +| +| +| +| +| +| +| +| 1925 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1926 |Central Administration | | | | | | +| +| +| +| +| +| 1927 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1928 |Hot Swap | | +| +| | | | | | | | +| 1929 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1930 |Data Flow Information Models| | | | | | | | | | | | 1931 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1932 |L2 and L3 Integration | | | | | | | | | | | | 1933 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1934 |End-to-end Delivery | +| +| +| +| +| +| +| +| +| | +| 1935 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1936 |Proprietary Deterministic | | | +| | | +| +| +| +| | | 1937 |Ethernet Networks | | | | | | | | | | | | 1938 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1939 |Replacement for Proprietary | | | +| | | +| +| +| +| | | 1940 |Fieldbuses | | | | | | | | | | | | 1941 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1942 |Deterministic vs. Best- | | | +| | | | | | | | | 1943 |Effort Traffic | | | | | | | | | | | | 1944 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1945 |Deterministic Flows | | +| +| | +| +| | +| | | | 1946 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1947 |Unused Reserved Bandwidth | | +| +| | | | | +| +| | | 1948 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1949 |Interoperability | | | | | | | | | | | | 1950 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1951 |Cost Reductions | | | | | | | | | | | | 1952 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1953 |Insufficiently Secure | | | | | | | | | | | | 1954 |Components | | | | | | | | | | | | 1955 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1956 |DetNet Network Size | +| | | | | +| +| | | | +| 1957 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1958 |Multiple Hops | +| +| | | | +| +| | | | +| 1959 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1960 |Level of Service | | | | | | | | +| +| +| | 1961 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1962 |Bounded Latency | +| | | | | | | | | | +| 1963 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1964 |Low Latency | +| | | | | | | +| +| +| +| 1965 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1966 |Bounded Jitter | +| | | | | | | | | | | 1967 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1968 |Symmetric Path Delays | +| | | | | | | | | | +| 1969 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1970 |Reliability and Availability| +| +| +| +| +| +| +| +| +| +| +| 1971 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1972 |Redundant Paths | | | | +| +| | | +| +| | | 1973 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1974 |Security Measures | | | | | | | | | | | | 1975 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1977 Figure 5: Mapping Between Themes and Attacks 1979 8.3. Security Considerations for OAM Traffic 1981 This section considers DetNet-specific security considerations for 1982 packet traffic that is generated and transmitted over a DetNet as 1983 part of OAM (Operations, Administration, and Maintenance). For the 1984 purposes of this discussion, OAM traffic falls into one of two basic 1985 types: 1987 o OAM traffic generated by the network itself. The additional 1988 bandwidth required for such packets is added by the network 1989 administration, presumably transparent to the customer. Security 1990 considerations for such traffic are not DetNet-specific (apart 1991 from such traffic being subject to the same DetNet-specific 1992 security considerations as any other DetNet data flow) and are 1993 thus not covered in this document. 1995 o OAM traffic generated by the customer. From a DetNet security 1996 point of view, DetNet security considerations for such traffic are 1997 exactly the same as for any other customer data flows. 1999 From the perspective of an attack, OAM traffic is indistinguishable 2000 from DetNet traffic and the network needs to be secure against 2001 injection, removal, or modification of traffic of any kind, including 2002 OAM traffic. A DetNet is sensitive to any form of packet injection, 2003 removal or manipulation and in this respect DetNet OAM traffic is no 2004 different. Techniques for securing a DetNet against these threats 2005 have been discussed elsewhere in this document. 2007 9. DetNet Technology-Specific Threats 2009 Section 5, Security Threats, described threats which are independent 2010 of a DetNet implementation. This section considers threats 2011 specifically related to the IP- and MPLS-specific aspects of DetNet 2012 implementations. 2014 The primary security considerations for the data plane specifically 2015 are to maintain the integrity of the data and the delivery of the 2016 associated DetNet service traversing the DetNet network. 2018 The primary relevant differences between IP and MPLS implementations 2019 are in flow identification and OAM methodologies. 2021 As noted in [RFC8655], DetNet operates at the IP layer ( [RFC8939]) 2022 and delivers service over sub-layer technologies such as MPLS 2023 ([RFC8938]) and IEEE 802.1 Time-Sensitive Networking (TSN) 2024 ([I-D.ietf-detnet-ip-over-tsn]). Application flows can be protected 2025 through whatever means are provided by the layer and sub-layer 2026 technologies. For example, technology-specific encryption may be 2027 used, for example for IP flows, IPSec [RFC4301]. For IP over 2028 Ethernet (Layer 2) flows using an underlying sub-net, MACSec 2029 [IEEE802.1AE-2018] may be appropriate. For some use cases packet 2030 integrity protection without encryption may be sufficient. 2032 However, if the DetNet nodes cannot decrypt IPsec traffic, then 2033 DetNet flow identification for encrypted IP traffic flows must be 2034 performed in a different way than it would be for unencrypted IP 2035 DetNet flows. The DetNet IP Data Plane identifies unencrypted flows 2036 via a 6-tuple that consists of two IP addresses, the transport 2037 protocol ID, two transport protocol port numbers and the DSCP in the 2038 IP header. When IPsec is used, the transport header is encrypted and 2039 the next protocol ID is an IPsec protocol, usually ESP, and not a 2040 transport protocol, leaving only three components of the 6-tuple, 2041 which are the two IP addresses and the DSCP. Identification of 2042 DetNet flows over IPsec is further discussed in Section 5.1.2.3. of 2043 [RFC8939]. 2045 Sections below discuss threats specific to IP and MPLS in more 2046 detail. 2048 9.1. IP 2050 The IP protocol has a long history of security considerations and 2051 architectural protection mechanisms. From a data plane perspective 2052 DetNet does not add or modify any IP header information, so the 2053 carriage of DetNet traffic over an IP data plane does not introduce 2054 any new security issues that were not there before, apart from those 2055 already described in the data-plane-independent threats section 2056 Section 5, Security Threats. 2058 Thus the security considerations for a DetNet based on an IP data 2059 plane are purely inherited from the rich IP Security literature and 2060 code/application base, and the data-plane-independent section of this 2061 document. 2063 Maintaining security for IP segments of a DetNet may be more 2064 challenging than for the MPLS segments of the network, given that the 2065 IP segments of the network may reach the edges of the network, which 2066 are more likely to involve interaction with potentially malevolent 2067 outside actors. Conversely MPLS is inherently more secure than IP 2068 since it is internal to routers and it is well-known how to protect 2069 it from outside influence. 2071 Another way to look at DetNet IP security is to consider it in the 2072 light of VPN security; as an industry we have a lot of experience 2073 with VPNs running through networks with other VPNs, it is well known 2074 how to secure the network for that. However for a DetNet we have the 2075 additional subtlety that any possible interaction of one packet with 2076 another can have a potentially deleterious effect on the time 2077 properties of the flows. So the network must provide sufficient 2078 isolation between flows, for example by protecting the forwarding 2079 bandwidth and related resources so that they are available to detnet 2080 traffic, by whatever means are appropriate for the data plane of that 2081 network, for example through the use of queueing mechanisms. 2083 In a VPN, bandwidth is generally guaranteed over a period of time, 2084 whereas in DetNet it is not aggregated over time. This implies that 2085 any VPN-type protection mechanism must also maintain the DetNet 2086 timing constraints. 2088 9.2. MPLS 2090 An MPLS network carrying DetNet traffic is expected to be a "well- 2091 managed" network. Given that this is the case, it is difficult for 2092 an attacker to pass a raw MPLS encoded packet into a network because 2093 operators have considerable experience at excluding such packets at 2094 the network boundaries, as well as excluding MPLS packets being 2095 inserted through the use of a tunnel. 2097 MPLS security is discussed extensively in [RFC5920] ("Security 2098 Framework for MPLS and GMPLS Networks") to which the reader is 2099 referred. 2101 [RFC6941] builds on [RFC5920] by providing additional security 2102 considerations that are applicable to the MPLS-TP extensions 2103 appropriate to the MPLS Transport Profile [RFC5921], and thus to the 2104 operation of DetNet over some types of MPLS network. 2106 [RFC5921] introduces to MPLS new Operations, Administration, and 2107 Maintenance (OAM) capabilities, a transport-oriented path protection 2108 mechanism, and strong emphasis on static provisioning supported by 2109 network management systems. 2111 The operation of DetNet over an MPLS network is modeled on the 2112 operation of multi-segment pseudowires (MS-PW). Thus for guidance on 2113 securing the DetNet elements of DetNet over MPLS the reader is 2114 referred to the MS-PW security mechanisms as defined in [RFC8077], 2115 [RFC3931], [RFC3985], [RFC6073], and [RFC6478]. 2117 Having attended to the conventional aspects of network security it is 2118 necessary to attend to the dynamic aspects. The closest experience 2119 that the IETF has with securing protocols that are sensitive to 2120 manipulation of delay are the two way time transfer protocols (TWTT), 2121 which are NTP [RFC5905] and Precision Time Protocol [IEEE1588]. The 2122 security requirements for these are described in [RFC7384]. 2124 One particular problem that has been observed in operational tests of 2125 TWTT protocols is the ability for two closely but not completely 2126 synchronized flows to beat and cause a sudden phase hit to one of the 2127 flows. This can be mitigated by the careful use of a scheduling 2128 system in the underlying packet transport. 2130 Further consideration of protection against dynamic attacks is work 2131 in progress. New work on MPLS security may also be applicable, for 2132 example [I-D.ietf-mpls-opportunistic-encrypt]. 2134 10. IANA Considerations 2136 This document includes no requests from IANA. 2138 11. Security Considerations 2140 The security considerations of DetNet networks are presented 2141 throughout this document. 2143 12. Privacy Considerations 2145 Privacy in the context of DetNet is maintained by the base 2146 technologies specific to the DetNet and user traffic. For example 2147 TSN can use MACsec, IP can use IPsec, applications can use IP 2148 transport protocol-provided methods e.g. TLS and DTLS. MPLS 2149 typically uses L2/L3 VPNs combined with the previously mentioned 2150 privacy methods. 2152 13. Contributors 2154 The Editor would like to recognize the contributions of the following 2155 individuals to this draft. 2157 Subir Das (Applied Communication Sciences) 2158 150 Mount Airy Road, Basking Ridge, New Jersey, 07920, USA 2159 email sdas@appcomsci.com 2161 John Dowdell (Airbus Defence and Space) 2162 Celtic Springs, Newport, NP10 8FZ, United Kingdom 2163 email john.dowdell.ietf@gmail.com 2165 Henrik Austad (SINTEF Digital) 2166 Klaebuveien 153, Trondheim, 7037, Norway 2167 email henrik@austad.us 2169 Norman Finn (Huawei) 2170 3101 Rio Way, Spring Valley, California 91977, USA 2171 email nfinn@nfinnconsulting.com 2173 Stewart Bryant (Futurewei Technologies) 2175 email: stewart.bryant@gmail.com 2177 David Black (Dell EMC) 2178 176 South Street, Hopkinton, MA 01748, USA 2179 email: david.black@dell.com 2181 Carsten Bormann (Universitat Bremen TZI) 2182 Postfach 330440, D-28359 Bremen, Germany 2183 email: cabo@tzi.org 2185 14. References 2187 14.1. Normative References 2189 [RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas, 2190 "Deterministic Networking Architecture", RFC 8655, 2191 DOI 10.17487/RFC8655, October 2019, 2192 . 2194 [RFC8938] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., and S. 2195 Bryant, "Deterministic Networking (DetNet) Data Plane 2196 Framework", RFC 8938, DOI 10.17487/RFC8938, November 2020, 2197 . 2199 [RFC8939] Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S. 2200 Bryant, "Deterministic Networking (DetNet) Data Plane: 2201 IP", RFC 8939, DOI 10.17487/RFC8939, November 2020, 2202 . 2204 14.2. Informative References 2206 [ARINC664P7] 2207 ARINC, "ARINC 664 Aircraft Data Network, Part 7, Avionics 2208 Full-Duplex Switched Ethernet Network", 2009. 2210 [I-D.ietf-detnet-flow-information-model] 2211 Varga, B., Farkas, J., Cummings, R., Jiang, Y., and D. 2212 Fedyk, "DetNet Flow Information Model", draft-ietf-detnet- 2213 flow-information-model-12 (work in progress), December 2214 2020. 2216 [I-D.ietf-detnet-ip-oam] 2217 Mirsky, G., Chen, M., and D. Black, "Operations, 2218 Administration and Maintenance (OAM) for Deterministic 2219 Networks (DetNet) with IP Data Plane", draft-ietf-detnet- 2220 ip-oam-00 (work in progress), September 2020. 2222 [I-D.ietf-detnet-ip-over-mpls] 2223 Varga, B., Berger, L., Fedyk, D., Bryant, S., and J. 2224 Korhonen, "DetNet Data Plane: IP over MPLS", draft-ietf- 2225 detnet-ip-over-mpls-09 (work in progress), October 2020. 2227 [I-D.ietf-detnet-ip-over-tsn] 2228 Varga, B., Farkas, J., Malis, A., and S. Bryant, "DetNet 2229 Data Plane: IP over IEEE 802.1 Time Sensitive Networking 2230 (TSN)", draft-ietf-detnet-ip-over-tsn-04 (work in 2231 progress), November 2020. 2233 [I-D.ietf-detnet-mpls-oam] 2234 Mirsky, G. and M. Chen, "Operations, Administration and 2235 Maintenance (OAM) for Deterministic Networks (DetNet) with 2236 MPLS Data Plane", draft-ietf-detnet-mpls-oam-01 (work in 2237 progress), July 2020. 2239 [I-D.ietf-detnet-mpls-over-udp-ip] 2240 Varga, B., Farkas, J., Berger, L., Malis, A., and S. 2241 Bryant, "DetNet Data Plane: MPLS over UDP/IP", draft-ietf- 2242 detnet-mpls-over-udp-ip-07 (work in progress), October 2243 2020. 2245 [I-D.ietf-ipsecme-g-ikev2] 2246 Smyslov, V. and B. Weis, "Group Key Management using 2247 IKEv2", draft-ietf-ipsecme-g-ikev2-01 (work in progress), 2248 July 2020. 2250 [I-D.ietf-mpls-opportunistic-encrypt] 2251 Farrel, A. and S. Farrell, "Opportunistic Security in MPLS 2252 Networks", draft-ietf-mpls-opportunistic-encrypt-03 (work 2253 in progress), March 2017. 2255 [I-D.varga-detnet-service-model] 2256 Varga, B. and J. Farkas, "DetNet Service Model", draft- 2257 varga-detnet-service-model-02 (work in progress), May 2258 2017. 2260 [IEEE1588] 2261 IEEE, "IEEE 1588 Standard for a Precision Clock 2262 Synchronization Protocol for Networked Measurement and 2263 Control Systems Version 2", 2008. 2265 [IEEE802.1AE-2018] 2266 IEEE Standards Association, "IEEE Std 802.1AE-2018 MAC 2267 Security (MACsec)", 2018, 2268 . 2270 [IEEE802.1BA] 2271 IEEE Standards Association, "IEEE Standard for Local and 2272 Metropolitan Area Networks -- Audio Video Bridging (AVB) 2273 Systems", 2011, 2274 . 2276 [IEEE802.1Q] 2277 IEEE Standards Association, "IEEE Standard for Local and 2278 metropolitan area networks--Bridges and Bridged Networks - 2279 Annex J - Connectivity Fault Management", 2014, 2280 . 2282 [IEEE802.1Qbv-2015] 2283 IEEE Standards Association, "IEEE Standard for Local and 2284 metropolitan area networks -- Bridges and Bridged Networks 2285 - Amendment 25: Enhancements for Scheduled Traffic", 2015, 2286 . 2288 [IEEE802.1Qch-2017] 2289 IEEE Standards Association, "IEEE Standard for Local and 2290 metropolitan area networks--Bridges and Bridged Networks-- 2291 Amendment 29: Cyclic Queuing and Forwarding", 2017, 2292 . 2294 [IETF_YANG_SEC] 2295 IETF, "YANG Module Security Considerations", 2018, 2296 . 2299 [IT_DEF] Wikipedia, "IT Definition", 2020, 2300 . 2302 [OT_DEF] Wikipedia, "OT Definition", 2020, 2303 . 2305 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 2306 "Definition of the Differentiated Services Field (DS 2307 Field) in the IPv4 and IPv6 Headers", RFC 2474, 2308 DOI 10.17487/RFC2474, December 1998, 2309 . 2311 [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., 2312 and W. Weiss, "An Architecture for Differentiated 2313 Services", RFC 2475, DOI 10.17487/RFC2475, December 1998, 2314 . 2316 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 2317 Text on Security Considerations", BCP 72, RFC 3552, 2318 DOI 10.17487/RFC3552, July 2003, 2319 . 2321 [RFC3931] Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed., 2322 "Layer Two Tunneling Protocol - Version 3 (L2TPv3)", 2323 RFC 3931, DOI 10.17487/RFC3931, March 2005, 2324 . 2326 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation 2327 Edge-to-Edge (PWE3) Architecture", RFC 3985, 2328 DOI 10.17487/RFC3985, March 2005, 2329 . 2331 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2332 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2333 December 2005, . 2335 [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection 2336 (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010, 2337 . 2339 [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, 2340 "Network Time Protocol Version 4: Protocol and Algorithms 2341 Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, 2342 . 2344 [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS 2345 Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010, 2346 . 2348 [RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau, 2349 L., and L. Berger, "A Framework for MPLS in Transport 2350 Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010, 2351 . 2353 [RFC6071] Frankel, S. and S. Krishnan, "IP Security (IPsec) and 2354 Internet Key Exchange (IKE) Document Roadmap", RFC 6071, 2355 DOI 10.17487/RFC6071, February 2011, 2356 . 2358 [RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M., and M. 2359 Aissaoui, "Segmented Pseudowire", RFC 6073, 2360 DOI 10.17487/RFC6073, January 2011, 2361 . 2363 [RFC6274] Gont, F., "Security Assessment of the Internet Protocol 2364 Version 4", RFC 6274, DOI 10.17487/RFC6274, July 2011, 2365 . 2367 [RFC6478] Martini, L., Swallow, G., Heron, G., and M. Bocci, 2368 "Pseudowire Status for Static Pseudowires", RFC 6478, 2369 DOI 10.17487/RFC6478, May 2012, 2370 . 2372 [RFC6632] Ersue, M., Ed. and B. Claise, "An Overview of the IETF 2373 Network Management Standards", RFC 6632, 2374 DOI 10.17487/RFC6632, June 2012, 2375 . 2377 [RFC6941] Fang, L., Ed., Niven-Jenkins, B., Ed., Mansfield, S., Ed., 2378 and R. Graveman, Ed., "MPLS Transport Profile (MPLS-TP) 2379 Security Framework", RFC 6941, DOI 10.17487/RFC6941, April 2380 2013, . 2382 [RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in 2383 Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384, 2384 October 2014, . 2386 [RFC7567] Baker, F., Ed. and G. Fairhurst, Ed., "IETF 2387 Recommendations Regarding Active Queue Management", 2388 BCP 197, RFC 7567, DOI 10.17487/RFC7567, July 2015, 2389 . 2391 [RFC7835] Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID 2392 Separation Protocol (LISP) Threat Analysis", RFC 7835, 2393 DOI 10.17487/RFC7835, April 2016, 2394 . 2396 [RFC8077] Martini, L., Ed. and G. Heron, Ed., "Pseudowire Setup and 2397 Maintenance Using the Label Distribution Protocol (LDP)", 2398 STD 84, RFC 8077, DOI 10.17487/RFC8077, February 2017, 2399 . 2401 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 2402 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 2403 . 2405 [RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases", 2406 RFC 8578, DOI 10.17487/RFC8578, May 2019, 2407 . 2409 [RS_DEF] Wikipedia, "RS Definition", 2020, 2410 . 2412 Authors' Addresses 2414 Ethan Grossman (editor) 2415 Dolby Laboratories, Inc. 2416 1275 Market Street 2417 San Francisco, CA 94103 2418 USA 2420 Phone: +1 415 465 4339 2421 Email: ethan@ieee.org 2422 URI: http://www.dolby.com 2424 Tal Mizrahi 2425 Huawei Network.IO Innovation Lab 2427 Email: tal.mizrahi.phd@gmail.com 2429 Andrew J. Hacker 2430 MistIQ Technologies, Inc 2431 Harrisburg, PA 2432 USA 2434 Email: ajhacker@mistiqtech.com 2435 URI: http://www.mistiqtech.com