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Hacker 7 MISTIQ 8 October 2, 2020 10 Deterministic Networking (DetNet) Security Considerations 11 draft-ietf-detnet-security-12 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. As a result, securing a DetNet requires that in 18 addition to the best practice security measures taken for any 19 mission-critical network, additional security measures may be needed 20 to secure the intended operation of these novel service properties. 22 This document addresses DetNet-specific security considerations from 23 the perspectives of both the DetNet system-level designer and 24 component designer. System considerations include a threat model, 25 taxonomy of relevant attacks, and associations of threats versus use 26 cases and service properties. Component-level considerations include 27 ingress filtering and packet arrival time violation detection. This 28 document also addresses DetNet security considerations specific to 29 the IP and MPLS data plane technologies thereby complementing the 30 Security Considerations sections of the various DetNet Data Plane 31 (and other) DetNet documents. 33 Status of This Memo 35 This Internet-Draft is submitted in full conformance with the 36 provisions of BCP 78 and BCP 79. 38 Internet-Drafts are working documents of the Internet Engineering 39 Task Force (IETF). Note that other groups may also distribute 40 working documents as Internet-Drafts. The list of current Internet- 41 Drafts is at https://datatracker.ietf.org/drafts/current/. 43 Internet-Drafts are draft documents valid for a maximum of six months 44 and may be updated, replaced, or obsoleted by other documents at any 45 time. It is inappropriate to use Internet-Drafts as reference 46 material or to cite them other than as "work in progress." 48 This Internet-Draft will expire on April 5, 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 . . . . . 6 70 3.1. Resource Allocation . . . . . . . . . . . . . . . . . . . 7 71 3.2. Explicit Routes . . . . . . . . . . . . . . . . . . . . . 7 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 . . . . . . . . . . . . . . . . . . . 9 76 5. Security Threats . . . . . . . . . . . . . . . . . . . . . . 10 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 . . . . . . . . . 12 83 5.2.4.1. Replication: Increased Attack Surface . . . . . . 12 84 5.2.4.2. Replication-related Header Manipulation . . . . . 12 85 5.2.5. Controller Plane . . . . . . . . . . . . . . . . . . 13 86 5.2.5.1. Path Choice Manipulation . . . . . . . . . . . . 13 87 5.2.5.2. Compromised Controller . . . . . . . . . . . . . 14 88 5.2.6. Reconnaissance . . . . . . . . . . . . . . . . . . . 14 89 5.2.7. Time Synchronization Mechanisms . . . . . . . . . . . 14 90 5.3. Threat Summary . . . . . . . . . . . . . . . . . . . . . 14 91 6. Security Threat Impacts . . . . . . . . . . . . . . . . . . . 15 92 6.1. Delay-Attacks . . . . . . . . . . . . . . . . . . . . . . 18 93 6.1.1. Data Plane Delay Attacks . . . . . . . . . . . . . . 18 94 6.1.2. Controller Plane Delay Attacks . . . . . . . . . . . 19 95 6.2. Flow Modification and Spoofing . . . . . . . . . . . . . 19 96 6.2.1. Flow Modification . . . . . . . . . . . . . . . . . . 19 97 6.2.2. Spoofing . . . . . . . . . . . . . . . . . . . . . . 19 98 6.2.2.1. Dataplane Spoofing . . . . . . . . . . . . . . . 19 99 6.2.2.2. Controller Plane Spoofing . . . . . . . . . . . . 20 100 6.3. Segmentation Attacks (injection) . . . . . . . . . . . . 20 101 6.3.1. Data Plane Segmentation . . . . . . . . . . . . . . . 20 102 6.3.2. Controller Plane Segmentation . . . . . . . . . . . . 20 103 6.4. Replication and Elimination . . . . . . . . . . . . . . . 21 104 6.4.1. Increased Attack Surface . . . . . . . . . . . . . . 21 105 6.4.2. Header Manipulation at Elimination Routers . . . . . 21 106 6.5. Control or Signaling Packet Modification . . . . . . . . 21 107 6.6. Control or Signaling Packet Injection . . . . . . . . . . 21 108 6.7. Reconnaissance . . . . . . . . . . . . . . . . . . . . . 21 109 6.8. Attacks on Time Sync Mechanisms . . . . . . . . . . . . . 22 110 6.9. Attacks on Path Choice . . . . . . . . . . . . . . . . . 22 111 7. Security Threat Mitigation . . . . . . . . . . . . . . . . . 22 112 7.1. Path Redundancy . . . . . . . . . . . . . . . . . . . . . 22 113 7.2. Integrity Protection . . . . . . . . . . . . . . . . . . 22 114 7.3. DetNet Node Authentication . . . . . . . . . . . . . . . 23 115 7.4. Dummy Traffic Insertion . . . . . . . . . . . . . . . . . 24 116 7.5. Encryption . . . . . . . . . . . . . . . . . . . . . . . 24 117 7.5.1. Encryption Considerations for DetNet . . . . . . . . 24 118 7.6. Control and Signaling Message Protection . . . . . . . . 25 119 7.7. Dynamic Performance Analytics . . . . . . . . . . . . . . 26 120 7.8. Mitigation Summary . . . . . . . . . . . . . . . . . . . 27 121 8. Association of Attacks to Use Cases . . . . . . . . . . . . . 28 122 8.1. Association of Attacks to Use Case Common Themes . . . . 28 123 8.1.1. Sub-Network Layer . . . . . . . . . . . . . . . . . . 28 124 8.1.2. Central Administration . . . . . . . . . . . . . . . 29 125 8.1.3. Hot Swap . . . . . . . . . . . . . . . . . . . . . . 29 126 8.1.4. Data Flow Information Models . . . . . . . . . . . . 30 127 8.1.5. L2 and L3 Integration . . . . . . . . . . . . . . . . 30 128 8.1.6. End-to-End Delivery . . . . . . . . . . . . . . . . . 30 129 8.1.7. Replacement for Proprietary Fieldbuses and Ethernet- 130 based Networks . . . . . . . . . . . . . . . . . . . 31 131 8.1.8. Deterministic vs Best-Effort Traffic . . . . . . . . 31 132 8.1.9. Deterministic Flows . . . . . . . . . . . . . . . . . 32 133 8.1.10. Unused Reserved Bandwidth . . . . . . . . . . . . . . 32 134 8.1.11. Interoperability . . . . . . . . . . . . . . . . . . 32 135 8.1.12. Cost Reductions . . . . . . . . . . . . . . . . . . . 32 136 8.1.13. Insufficiently Secure Devices . . . . . . . . . . . . 33 137 8.1.14. DetNet Network Size . . . . . . . . . . . . . . . . . 33 138 8.1.15. Multiple Hops . . . . . . . . . . . . . . . . . . . . 34 139 8.1.16. Level of Service . . . . . . . . . . . . . . . . . . 34 140 8.1.17. Bounded Latency . . . . . . . . . . . . . . . . . . . 34 141 8.1.18. Low Latency . . . . . . . . . . . . . . . . . . . . . 35 142 8.1.19. Bounded Jitter (Latency Variation) . . . . . . . . . 35 143 8.1.20. Symmetrical Path Delays . . . . . . . . . . . . . . . 35 144 8.1.21. Reliability and Availability . . . . . . . . . . . . 35 145 8.1.22. Redundant Paths . . . . . . . . . . . . . . . . . . . 36 146 8.1.23. Security Measures . . . . . . . . . . . . . . . . . . 36 147 8.2. Summary of Attack Types per Use Case Common Theme . . . . 36 148 8.3. Security Considerations for OAM Traffic . . . . . . . . . 39 149 9. DetNet Technology-Specific Threats . . . . . . . . . . . . . 39 150 9.1. IP . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 151 9.2. MPLS . . . . . . . . . . . . . . . . . . . . . . . . . . 41 152 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 42 153 11. Security Considerations . . . . . . . . . . . . . . . . . . . 42 154 12. Privacy Considerations . . . . . . . . . . . . . . . . . . . 42 155 13. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 42 156 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 43 157 14.1. Normative References . . . . . . . . . . . . . . . . . . 43 158 14.2. Informative References . . . . . . . . . . . . . . . . . 44 159 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 47 161 1. Introduction 163 A deterministic network is one that can carry data flows for real- 164 time applications with extremely low data loss rates and bounded 165 latency. Deterministic networks have been successfully deployed in 166 real-time Operational Technology (OT) applications for some years. 167 However, such networks are typically isolated from external access, 168 and thus the security threat from external attackers is low. IETF 169 Deterministic Networking (DetNet, [RFC8655]) specifies a set of 170 technologies that enable creation of deterministic networks on IP- 171 based networks of potentially wide area (on the scale of a corporate 172 network) potentially bringing the OT network into contact with 173 Information Technology (IT) traffic and security threats that lie 174 outside of a tightly controlled and bounded area (such as the 175 internals of an aircraft). 177 These DetNet technologies have not previously been deployed together 178 on a wide area IP-based network, and thus can present security 179 considerations that may be new to IP-based wide area network 180 designers; this document provides insight into such system-level 181 security considerations. In addition, designers of DetNet components 182 (such as routers) face new security-related challenges in providing 183 DetNet services, for example maintaining reliable isolation between 184 traffic flows in an environment where IT traffic co-mingles with 185 critical reserved-bandwidth OT traffic; this document also examines 186 security implications internal to DetNet components. 188 Security is of particularly high importance in DetNet networks 189 because many of the use cases which are enabled by DetNet [RFC8578] 190 include control of physical devices (power grid components, 191 industrial controls, building controls) which can have high 192 operational costs for failure, and present potentially attractive 193 targets for cyber-attackers. 195 This situation is even more acute given that one of the goals of 196 DetNet is to provide a "converged network", i.e. one that includes 197 both IT traffic and OT traffic, thus exposing potentially sensitive 198 OT devices to attack in ways that were not previously common (usually 199 because they were under a separate control system or otherwise 200 isolated from the IT network, for example [ARINC664P7]). Security 201 considerations for OT networks are not a new area, and there are many 202 OT networks today that are connected to wide area networks or the 203 Internet; this document focuses on the issues that are specific to 204 the DetNet technologies and use cases. 206 Given the above considerations, securing a DetNet starts with a 207 scrupulously well-designed and well-managed engineered network 208 following industry best practices for security at both the data plane 209 and controller plane; this is the assumed starting point for the 210 considerations discussed herein. Such assumptions also depend on the 211 network components themselves upholding the security-related 212 properties that are to be assumed by DetNet system-level designers; 213 for example, the assumption that network traffic associated with a 214 given flow can never affect traffic associated with a different flow 215 is only true if the underlying components make it so. Such 216 properties, which may represent new challenges to component 217 designers, are also considered herein. 219 In this context we view the network design and management aspects of 220 network security as being primarily concerned with denial-of service 221 prevention by ensuring that DetNet traffic goes where it's supposed 222 to and that an external attacker can't inject traffic that disrupts 223 the DetNet's delivery timing assurance. The time-specific aspects of 224 DetNet security presented here take up where the design and 225 management aspects leave off. 227 The exact security requirements for any given DetNet network are 228 necessarily specific to the use cases handled by that network. Thus 229 the reader is assumed to be familiar with the specific security 230 requirements of their use cases, for example those outlined in the 231 DetNet Use Cases [RFC8578] and the Security Considerations sections 232 of the DetNet documents applicable to the network technologies in 233 use, for example [I-D.ietf-detnet-ip]). A general introduction to 234 the DetNet architecture can be found in [RFC8655] and it is also 235 recommended to be familiar with the DetNet Data Plane 236 [I-D.ietf-detnet-data-plane-framework] and Flow Information Model 237 [I-D.ietf-detnet-flow-information-model]. 239 The DetNet technologies include ways to: 241 o Assign data plane resources for DetNet flows in some or all of the 242 intermediate nodes (routers) along the path of the flow 244 o Provide explicit routes for DetNet flows that do not dynamically 245 change with the network topology in ways that affect the quality 246 of service received by the affected flow(s) 248 o Distribute data from DetNet flow packets over time and/or space to 249 ensure delivery of each packet's data' in spite of the loss of a 250 path 252 This document includes sections considering DetNet component design 253 as well as system design. The latter includes threat modeling and 254 analysis, threat impact and mitigation, and the association of 255 attacks with use cases (based on the Use Case Common Themes section 256 of the DetNet Use Cases [RFC8578]). 258 The structure of the threat model and threat analysis sections were 259 originally derived from [RFC7384], which also considers time-related 260 security considerations in IP networks. 262 2. Abbreviations and Terminology 264 IT Information Technology (the application of computers to 265 store, study, retrieve, transmit, and manipulate data or information, 266 often in the context of a business or other enterprise - [IT_DEF]). 268 OT Operational Technology (the hardware and software 269 dedicated to detecting or causing changes in physical processes 270 through direct monitoring and/or control of physical devices such as 271 valves, pumps, etc. - [OT_DEF]) 273 Component A component of a DetNet system - used here to refer 274 to any hardware or software element of a DetNet network which 275 implements DetNet-specific functionality, for example all or part of 276 a router, switch, or end system. 278 Resource Segmentation Used as a more general form for Network 279 Segmentation (the act or practice of splitting a computer network 280 into subnetworks, each being a network segment - [RS_DEF]) 282 3. Security Considerations for DetNet Component Design 284 As noted above, DetNet provides resource allocation, explicit routes 285 and redundant path support. Each of these has associated security 286 implications, which are discussed in this section, in the context of 287 component design. Detection, reporting and appropriate action in the 288 case of packet arrival time violations are also discussed. 290 3.1. Resource Allocation 292 A DetNet system security designer relies on the premise that any 293 resources allocated to a resource-reserved (OT-type) flow are 294 inviolable, in other words there is no physical possibility within a 295 DetNet component that resources allocated to a given flow can be 296 compromised by any type of traffic in the network; this includes both 297 malicious traffic as well as inadvertent traffic such as might be 298 produced by a malfunctioning component, for example one made by a 299 different manufacturer. From a security standpoint, this is a 300 critical assumption, for example when designing against DOS attacks. 302 It is the responsibility of the component designer to ensure that 303 this condition is met; this implies protection against excess traffic 304 from adjacent flows, and against compromises to the resource 305 allocation/deallocation process, for example through the use of 306 traffic shaping and policing. 308 As an example, consider the implementation of Flow Aggregation for 309 DetNet flows (as discussed in 310 [I-D.ietf-detnet-data-plane-framework]). In this example say there 311 are N flows that are to be aggregated, thus the bandwidth resources 312 of the aggregate flow must be sufficient to contain the sum of the 313 bandwidth reservation for the N flows. However if one of those flows 314 were to consume more than its individually allocated BW, this could 315 cause starvation of the other flows. Thus simply providing and 316 enforcing the calculated aggregate bandwidth may not be a complete 317 solution - the bandwidth for each individual flow must still be 318 guaranteed, for example via ingress policing of each flow (i.e. 319 before it is aggregated). Alternatively, if by some other means each 320 flow to be aggregated can be trusted not to exceed its allocated 321 bandwidth, the same goal can be achieved. 323 3.2. Explicit Routes 325 The DetNet-specific purpose for constraining the network's ability to 326 re-route OT traffic is to maintain the specified service parameters 327 (such as upper and lower latency boundaries) for a given flow. For 328 example if the network were to re-route a flow (or some part of a 329 flow) based exclusively on statistical path usage metrics, or due to 330 malicious activity, it is possible that the new path would have a 331 latency that is outside the required latency bounds which were 332 designed into the original TE-designed path, thereby violating the 333 quality of service for the affected flow (or part of that flow). 335 However, it is acceptable for the network to re-route OT traffic in 336 such a way as to maintain the specified latency bounds (and any other 337 specified service properties) for any reason, for example in response 338 to a runtime component or path failure. From a security standpoint, 339 the system designer relies on the premise that the packets will be 340 delivered with the specified latency boundaries; thus any component 341 that is involved in controlling or implementing any change of the 342 initially TE-configured flow routes needs to prevent malicious or 343 accidental re-routing of OT flows that might adversely affect 344 delivering the traffic within the specified service parameters. 346 3.3. Redundant Path Support 348 The DetNet provision for redundant paths (PREOF) (as defined in the 349 DetNet Architecture [RFC8655]) provides the foundation for high 350 reliablity of a DetNet, by virtually eliminating packet loss (i.e. to 351 a degree which is implementation-dependent) through hitless redundant 352 packet delivery. (Note that PREOF is not defined for a DetNet IP 353 data plane). 355 It is the responsibility of the system designer to determine the 356 level of reliability required by their use case, and to specify 357 redundant paths sufficient to provide the desired level of 358 reliability (in as much as that reliability can be provided through 359 the use of redundant paths). It is the responsibility of the 360 component designer to ensure that the relevant PREOF operations are 361 executed reliably and securely, to avoid potentially catastrophic 362 situations for the operational technology relying on them. 364 However, note that not all PREOF operations are necessarily 365 implemented in every network; for example a packet re-ordering 366 function may not be necessary if the packets are either not required 367 to be in order, or if the ordering is performed in some other part of 368 the network. 370 Ideally a redundant path could be specified from end to end of the 371 flow's path, however given that this is not always possible (as 372 described in [RFC8655]) the system designer will need to consider the 373 resulting end-to-end reliability and security resulting from any 374 given arrangment of network segments along the path, each of which 375 provides its individual PREOF implementation and thus its individual 376 level of reliabiilty and security. 378 At the data plane the implementation of PREOF depends on the correct 379 assignment and interpretation of packet sequence numbers, as well as 380 the actions taken based on them, such as elimination (including 381 elimination of packets with spurious sequence numbers). Thus the 382 integrity of these values must be maintained by the component as they 383 are assigned by the DetNet Data Plane's Service sub-layer, and 384 transported by the Forwarding sub-layer. This is no different than 385 the integrity of the values in any header used by the DetNet (or any 386 other) data plane, and is not unique to redundant paths. From the 387 sequence number injection perspective, it is no different from any 388 other protocols that use sequence numbers. 390 3.4. Timing (or other) Violation Reporting 392 Another fundamental assumption of a secure DetNet is that in any case 393 in which an incoming packet arrives with any timing or bandwidth 394 violation, something can be done about it which doesn't cause damage 395 to the system. For example having the network shut down a link if a 396 packet arrives outside of its prescribed time window may serve the 397 attacker better than it serves the network. That means that the 398 component's data plane must be able to detect and act on a variety of 399 such violations, at least alerting the controller plane. Any action 400 apart from that needs to be carefully considered in the context of 401 the specific system. Some possible violations that warrant detection 402 include cases where a packet arrives: 404 o Outside of its prescribed time window 406 o Within its time window but with a compromised time stamp that 407 makes it appear that it is not within its window 409 o Exceeding the reserved flow bandwidth 411 Logging of such issues is unlikely to be adequate, since a delay in 412 response to the situation could result in material damage, for 413 example to mechanical devices controlled by the network. Given that 414 the data plane component probably has no knowledge of the use case of 415 the network, or its applications and end systems, it would seem 416 useful for a data plane component to allow the system designer to 417 configure its actions in the face of such violations. 419 Possible direct actions that may be taken at the data plane include 420 dropping the packet and/or shutting down the link; however if any 421 such actions are configured to be taken, the system designer must 422 ensure that such actions do not compromise the continued safe 423 operation of the system. For example, the controller plane should 424 mitigate in a timely fashion any potential adverse effect on 425 mechanical devices controlled by the network. 427 4. DetNet Security Considerations Compared With DiffServ Security 428 Considerations 430 DetNet is designed to be compatible with DiffServ [RFC2474] as 431 applied to IT traffic in the DetNet. DetNet also incorporates the 432 use of the 6-bit value of the DSCP field of the TOS field of the IP 433 header for flow identification for OT traffic, however the DetNet 434 interpretation of the DSCP value for OT traffic is not equivalent to 435 the PHB selection behavior as defined by DiffServ. 437 Thus security consideration for DetNet have some aspects in common 438 with DiffServ, in fact overlapping 100% with respect to IP IT 439 traffic. Security considerations for these aspects are part of the 440 existing literature on IP network security, specifically the Security 441 sections of [RFC2474] and [RFC2475]. However DetNet also introduces 442 timing and other considerations which are not present in DiffServ, so 443 the DiffServ security considerations are necessary but not sufficient 444 for DetNet. 446 In the case of DetNet OT traffic, the DSCP value, although 447 interpreted differently than in DiffServ, does contribute to 448 determination of the service provided to the packet. Thus in DetNet 449 there are similar consequences to DiffServ for lack of detection of, 450 or incorrect handling of, packets with mismarked DSCP values, and 451 thus many of the points made in the DiffServ draft Security 452 discussions are also relevant to DetNet OT traffic, though perhaps in 453 modified form. For example, in DetNet the effect of an undetected or 454 incorrectly handled maliciously mismarked DSCP field in an OT packet 455 is not identical to affecting that packet's PHB, since DetNet does 456 not use the PHB concept for OT traffic, but nonetheless the service 457 provided to the packet could be affected, so mitigation measures 458 analogous to those prescribed by DiffServ would be appropriate for 459 DetNet. For example, mismarked DSCP values should not cause failure 460 of network nodes, and any internal link that cannot be adequately 461 secured against modification of DSCP values should be treated as a 462 boundary link (and hence any arriving traffic on that link is treated 463 as if it were entering the domain at an ingress node). The remarks 464 in [RFC2474] regarding IPsec and Tunnelling Interactions are also 465 relevant (though this is not to say that other sections are less 466 relevant). 468 5. Security Threats 470 This section presents a threat model, and analyzes the possible 471 threats in a DetNet-enabled network. The threats considered in this 472 section are independent of any specific technologies used to 473 implement the DetNet; Section 9 considers attacks that are associated 474 with the DetNet technologies encompassed by 475 [I-D.ietf-detnet-data-plane-framework]. 477 We distinguish controller plane threats from data plane threats. The 478 attack surface may be the same, but the types of attacks as well as 479 the motivation behind them, are different. For example, a delay 480 attack is more relevant to data plane than to controller plane. 481 There is also a difference in terms of security solutions: the way 482 you secure the data plane is often different than the way you secure 483 the controller plane. 485 5.1. Threat Model 487 The threat model used in this memo employs organizational elements of 488 the threat models of [RFC7384] and [RFC7835] . This model classifies 489 attackers based on two criteria: 491 o Internal vs. external: internal attackers either have access to a 492 trusted segment of the network or possess the encryption or 493 authentication keys. External attackers, on the other hand, do 494 not have the keys and have access only to the encrypted or 495 authenticated traffic. 497 o On-path vs. off-path: on-path attackers are located in a position 498 that allows interception and modification of in-flight protocol 499 packets, whereas off-path attackers can only attack by generating 500 protocol packets. 502 Care has also been taken to adhere to Section 5 of [RFC3552], both 503 with respect to which attacks are considered out-of-scope for this 504 document, but also which are considered to be the most common threats 505 (explored further in Section 5.2, Threat Analysis). Most of the 506 direct threats to DetNet are active attacks (i.e. attacks that modify 507 DetNet traffic), but it is highly suggested that DetNet application 508 developers take appropriate measures to protect the content of the 509 DetNet flows from passive attacks (i.e. attacks that observe but do 510 not modify DetNet traffic) for example through the use of TLS or 511 DTLS. 513 DetNet-Service, one of the service scenarios described in 514 [I-D.varga-detnet-service-model], is the case where a service 515 connects DetNet networking islands, i.e. two or more otherwise 516 independent DetNet network domains are connected via a link that is 517 not intrinsically part of either network. This implies that there 518 could be DetNet traffic flowing over a non-DetNet link, which may 519 provide an attacker with an advantageous opportunity to tamper with 520 DetNet traffic. The security properties of non-DetNet links are 521 outside of the scope of DetNet Security, but it should be noted that 522 use of non-DetNet services to interconnect DetNet networks merits 523 security analysis to ensure the integrity of the DetNet networks 524 involved. 526 5.2. Threat Analysis 528 5.2.1. Delay 530 An attacker can maliciously delay DetNet data flow traffic. By 531 delaying the traffic, the attacker can compromise the service of 532 applications that are sensitive to high delays or to high delay 533 variation. The delay may be constant or modulated. 535 5.2.2. DetNet Flow Modification or Spoofing 537 An attacker can modify some header fields of en route packets in a 538 way that causes the DetNet flow identification mechanisms to 539 misclassify the flow. Alternatively, the attacker can inject traffic 540 that is tailored to appear as if it belongs to a legitimate DetNet 541 flow. The potential consequence is that the DetNet flow resource 542 allocation cannot guarantee the performance that is expected when the 543 flow identification works correctly. 545 5.2.3. Resource Segmentation (Inter-segment Attack) 547 An attacker can inject traffic that will consume network resources 548 such that it affects DetNet flows. This can be performed using non- 549 DetNet traffic that indirectly affects DetNet traffic (hardware 550 resource exhaustion), or by using DetNet traffic from one DetNet flow 551 that directly affects traffic from different DetNet flows. 553 5.2.4. Packet Replication and Elimination 555 5.2.4.1. Replication: Increased Attack Surface 557 Redundancy is intended to increase the robustness and survivability 558 of DetNet flows, and replication over multiple paths can potentially 559 mitigate an attack that is limited to a single path. However, the 560 fact that packets are replicated over multiple paths increases the 561 attack surface of the network, i.e., there are more points in the 562 network that may be subject to attacks. 564 5.2.4.2. Replication-related Header Manipulation 566 An attacker can manipulate the replication-related header fields. 567 This capability opens the door for various types of attacks. For 568 example: 570 o Forward both replicas - malicious change of a packet SN (Sequence 571 Number) can cause both replicas of the packet to be forwarded. 572 Note that this attack has a similar outcome to a replay attack. 574 o Eliminate both replicas - SN manipulation can be used to cause 575 both replicas to be eliminated. In this case an attacker that has 576 access to a single path can cause packets from other paths to be 577 dropped, thus compromising some of the advantage of path 578 redundancy. 580 o Flow hijacking - an attacker can hijack a DetNet flow with access 581 to a single path by systematically replacing the SNs on the given 582 path with higher SN values. For example, an attacker can replace 583 every SN value S with a higher value S+C, where C is a constant 584 integer. Thus, the attacker creates a false illusion that the 585 attacked path has the lowest delay, causing all packets from other 586 paths to be eliminated in favor of the attacked path. Once the 587 flow from the compromised path is favored by the elminating 588 bridge, the flow is hijacked by the attacker. It is now posible 589 to either replace en route packets with malicious packets, or 590 simply injecting errors, causing the packets to be dropped at 591 their destination. 593 o Amplification - an attacker who injects packets into a flow that 594 is to be replicated will have their attack amplified through the 595 replication process. This is no different than any attacker who 596 injects packets that are delivered through multicast, broadcast, 597 or other point-to-multi-point mechanisms. 599 5.2.5. Controller Plane 601 5.2.5.1. Path Choice Manipulation 603 5.2.5.1.1. Control or Signaling Packet Modification 605 An attacker can maliciously modify en route control packets in order 606 to disrupt or manipulate the DetNet path/resource allocation. 608 5.2.5.1.2. Control or Signaling Packet Injection 610 An attacker can maliciously inject control packets in order to 611 disrupt or manipulate the DetNet path/resource allocation. 613 5.2.5.1.3. Increased Attack Surface 615 One of the possible consequences of a path manipulation attack is an 616 increased attack surface. Thus, when the attack described in the 617 previous subsection is implemented, it may increase the potential of 618 other attacks to be performed. 620 5.2.5.2. Compromised Controller 622 An attacker can subvert a controller, or enable a compromised 623 controller to falsely represent itself as a controller so that the 624 network nodes believe it to be authorized to instruct them. 626 Presence of compromised nodes in a DetNet is not a "new" threat that 627 arises as a result of determinism or time sensitivity; the same 628 techniques used to prevent or mitigate against compromised nodes in 629 any network are equally applicable in the DetNet case. However this 630 underscores the requirement for careful system security design in a 631 DetNet, given that the effects of even one bad actor on the network 632 can be potentially catastrophic. 634 Security concerns specific to any given controller plane technology 635 used in DetNet will be addressed by the DetNet documents associated 636 with that technology. 638 5.2.6. Reconnaissance 640 A passive eavesdropper can identify DetNet flows and then gather 641 information about en route DetNet flows, e.g., the number of DetNet 642 flows, their bandwidths, their schedules, or other temporal 643 properties. The gathered information can later be used to invoke 644 other attacks on some or all of the flows. 646 Note that in some cases DetNet flows may be identified based on an 647 explicit DetNet header, but in some cases the flow identification may 648 be based on fields from the L3/L4 headers. If L3/L4 headers are 649 involved, for the purposes of this document we assume they are 650 encrypted and/or integrity-protected from external attackers. 652 5.2.7. Time Synchronization Mechanisms 654 An attacker can use any of the attacks described in [RFC7384] to 655 attack the synchronization protocol, thus affecting the DetNet 656 service. 658 5.3. Threat Summary 660 A summary of the attacks that were discussed in this section is 661 presented in Figure 1. For each attack, the table specifies the type 662 of attackers that may invoke the attack. In the context of this 663 summary, the distinction between internal and external attacks is 664 under the assumption that a corresponding security mechanism is being 665 used, and that the corresponding network equipment takes part in this 666 mechanism. 668 +-----------------------------------------+----+----+----+----+ 669 | Attack | Attacker Type | 670 | +---------+---------+ 671 | |Internal |External | 672 | |On-P|Off-P|On-P|Off-P| 673 +-----------------------------------------+----+----+----+----+ 674 |Delay attack | + | + | + | + | 675 +-----------------------------------------+----+----+----+----+ 676 |DetNet Flow Modification or Spoofing | + | + | | | 677 +-----------------------------------------+----+----+----+----+ 678 |Inter-segment Attack | + | + | | | 679 +-----------------------------------------+----+----+----+----+ 680 |Replication: Increased Attack Surface | + | + | + | + | 681 +-----------------------------------------+----+----+----+----+ 682 |Replication-related Header Manipulation | + | | | | 683 +-----------------------------------------+----+----+----+----+ 684 |Path Manipulation | + | + | | | 685 +-----------------------------------------+----+----+----+----+ 686 |Path Choice: Increased Attack Surface | + | + | + | + | 687 +-----------------------------------------+----+----+----+----+ 688 |Control or Signaling Packet Modification | + | | | | 689 +-----------------------------------------+----+----+----+----+ 690 |Control or Signaling Packet Injection | | + | | | 691 +-----------------------------------------+----+----+----+----+ 692 |Reconnaissance | + | | + | | 693 +-----------------------------------------+----+----+----+----+ 694 |Attacks on Time Sync Mechanisms | + | + | + | + | 695 +-----------------------------------------+----+----+----+----+ 697 Figure 1: Threat Analysis Summary 699 6. Security Threat Impacts 701 This section describes and rates the impact of the attacks described 702 in Section 5, Security Threats. In this section, the impacts as 703 described assume that the associated mitigation is not present or has 704 failed. Mitigations are discussed in Section 7, Security Threat 705 Mitigation. 707 In computer security, the impact (or consequence) of an incident can 708 be measured in loss of confidentiality, integrity or availability of 709 information. In the case of time sensitive networks, the impact of a 710 network exploit can also include failure or malfunction of mechanical 711 and/or other OT systems. 713 DetNet raises these stakes significantly for OT applications, 714 particularly those which may have been designed to run in an OT-only 715 environment and thus may not have been designed for security in an IT 716 environment with its associated devices, services and protocols. 718 The severity of various components of the impact of a successful 719 vulnerability exploit to use cases by industry is available in more 720 detail in the DetNet Use Cases [RFC8578]. Each of these use cases is 721 represented in the table below, including Pro Audio, Electrical 722 Utilities, Industrial M2M (split into two areas, M2M Data Gathering 723 and M2M Control Loop), and others. 725 Components of Impact (left column) include Criticality of Failure, 726 Effects of Failure, Recovery, and DetNet Functional Dependence. 727 Criticality of failure summarizes the seriousness of the impact. The 728 impact of a resulting failure can affect many different metrics that 729 vary greatly in scope and severity. In order to reduce the number of 730 variables, only the following were included: Financial, Health and 731 Safety, People well being (People WB), Affect on a single 732 organization, and affect on multiple organizations. Recovery 733 outlines how long it would take for an affected use case to get back 734 to its pre-failure state (Recovery time objective, RTO), and how much 735 of the original service would be lost in between the time of service 736 failure and recovery to original state (Recovery Point Objective, 737 RPO). DetNet dependence maps how much the following DetNet service 738 objectives contribute to impact of failure: Time dependency, data 739 integrity, source node integrity, availability, latency/jitter. 741 The scale of the Impact mappings is low, medium, and high. In some 742 use cases there may be a multitude of specific applications in which 743 DetNet is used. For simplicity this section attempts to average the 744 varied impacts of different applications. This section does not 745 address the overall risk of a certain impact which would require the 746 likelihood of a failure happening. 748 In practice any such ratings will vary from case to case; the ratings 749 shown here are given as examples. 751 Table, Part One (of Two) 752 +------------------+-----------------------------------------+-----+ 753 | | Pro A | Util | Bldg |Wire- | Cell |M2M |M2M | 754 | | | | | less | |Data |Ctrl | 755 +------------------+-----------------------------------------+-----+ 756 | Criticality | Med | Hi | Low | Med | Med | Med | Med | 757 +------------------+-----------------------------------------+-----+ 758 | Effects 759 +------------------+-----------------------------------------+-----+ 760 | Financial | Med | Hi | Med | Med | Low | Med | Med | 761 +------------------+-----------------------------------------+-----+ 762 | Health/Safety | Med | Hi | Hi | Med | Med | Med | Med | 763 +------------------+-----------------------------------------+-----+ 764 | People WB | Med | Hi | Hi | Low | Hi | Low | Low | 765 +------------------+-----------------------------------------+-----+ 766 | Effect 1 org | Hi | Hi | Med | Hi | Med | Med | Med | 767 +------------------+-----------------------------------------+-----+ 768 | Effect >1 org | Med | Hi | Low | Med | Med | Med | Med | 769 +------------------+-----------------------------------------+-----+ 770 |Recovery 771 +------------------+-----------------------------------------+-----+ 772 | Recov Time Obj | Med | Hi | Med | Hi | Hi | Hi | Hi | 773 +------------------+-----------------------------------------+-----+ 774 | Recov Point Obj | Med | Hi | Low | Med | Low | Hi | Hi | 775 +------------------+-----------------------------------------+-----+ 776 |DetNet Dependence 777 +------------------+-----------------------------------------+-----+ 778 | Time Dependency | Hi | Hi | Low | Hi | Med | Low | Hi | 779 +------------------+-----------------------------------------+-----+ 780 | Latency/Jitter | Hi | Hi | Med | Med | Low | Low | Hi | 781 +------------------+-----------------------------------------+-----+ 782 | Data Integrity | Hi | Hi | Med | Hi | Low | Hi | Low | 783 +------------------+-----------------------------------------+-----+ 784 | Src Node Integ | Hi | Hi | Med | Hi | Med | Hi | Hi | 785 +------------------+-----------------------------------------+-----+ 786 | Availability | Hi | Hi | Med | Hi | Low | Hi | Hi | 787 +------------------+-----------------------------------------+-----+ 789 Table, Part Two (of Two) 790 +------------------+--------------------------+ 791 | | Mining | Block | Network | 792 | | | Chain | Slicing | 793 +------------------+--------------------------+ 794 | Criticality | Hi | Med | Hi | 795 +------------------+--------------------------+ 796 | Effects 797 +------------------+--------------------------+ 798 | Financial | Hi | Hi | Hi | 799 +------------------+--------------------------+ 800 | Health/Safety | Hi | Low | Med | 801 +------------------+--------------------------+ 802 | People WB | Hi | Low | Med | 803 +------------------+--------------------------+ 804 | Effect 1 org | Hi | Hi | Hi | 805 +------------------+--------------------------+ 806 | Effect >1 org | Hi | Low | Hi | 807 +------------------+--------------------------+ 808 |Recovery 809 +------------------+--------------------------+ 810 | Recov Time Obj | Hi | Low | Hi | 811 +------------------+--------------------------+ 812 | Recov Point Obj | Hi | Low | Hi | 813 +------------------+--------------------------+ 814 |DetNet Dependence 815 +------------------+--------------------------+ 816 | Time Dependency | Hi | Low | Hi | 817 +------------------+--------------------------+ 818 | Latency/Jitter | Hi | Low | Hi | 819 +------------------+--------------------------+ 820 | Data Integrity | Hi | Hi | Hi | 821 +------------------+--------------------------+ 822 | Src Node Integ | Hi | Hi | Hi | 823 +------------------+--------------------------+ 824 | Availability | Hi | Hi | Hi | 825 +------------------+--------------------------+ 827 Figure 2: Impact of Attacks by Use Case Industry 829 The rest of this section will cover impact of the different groups in 830 more detail. 832 6.1. Delay-Attacks 834 6.1.1. Data Plane Delay Attacks 836 Note that 'delay attack' also includes the possibility of a 'negative 837 delay' or early arrival of a packet, or possibly adversely changing 838 the timestamp value. 840 Delayed messages in a DetNet link can result in the same behavior as 841 dropped messages in ordinary networks as the services attached to the 842 DetNet flow have strict deterministic requirements. 844 For a single path scenario, disruption is a real possibility, whereas 845 in a multipath scenario, large delays or instabilities in one DetNet 846 flow can lead to increased buffer and processor resources at the 847 eliminating router. 849 A data-plane delay attack on a system controlling substantial moving 850 devices, for example in industrial automation, can cause physical 851 damage. For example, if the network promises a bounded latency of 852 2ms for a flow, yet the machine receives it with 5ms latency, the 853 machine's control loop can become unstable. 855 6.1.2. Controller Plane Delay Attacks 857 In and of itself, this is not directly a threat to the DetNet 858 service, but the effects of delaying control messages can have quite 859 adverse effects later. 861 o Delayed tear-down can lead to resource leakage, which in turn can 862 result in failure to allocate new DetNet flows, finally giving 863 rise to a denial of service attack. 865 o Failure to deliver, or severely delaying, controller plane 866 messages adding an endpoint to a multicast-group will prevent the 867 new endpoint from receiving expected frames thus disrupting 868 expected behavior. 870 o Delaying messages removing an endpoint from a group can lead to 871 loss of privacy as the endpoint will continue to receive messages 872 even after it is supposedly removed. 874 6.2. Flow Modification and Spoofing 876 6.2.1. Flow Modification 878 If the contents of a packet header or body can be modified by the 879 attacker, this can cause the packet to be routed incorrectly or 880 dropped, or the payload to be corrupted or subtly modified. 882 6.2.2. Spoofing 884 6.2.2.1. Dataplane Spoofing 886 Spoofing dataplane messages can result in increased resource 887 consumptions on the routers throughout the network as it will 888 increase buffer usage and processor utilization. This can lead to 889 resource exhaustion and/or increased delay. 891 If the attacker manages to create valid headers, the false messages 892 can be forwarded through the network, using part of the allocated 893 bandwidth. This in turn can cause legitimate messages to be dropped 894 when the resource budget has been exhausted. 896 Finally, the endpoint will have to deal with invalid messages being 897 delivered to the endpoint instead of (or in addition to) a valid 898 message. 900 6.2.2.2. Controller Plane Spoofing 902 A successful controller plane spoofing-attack will potentionally have 903 adverse effects. It can do virtually anything from: 905 o modifying existing DetNet flows by changing the available 906 bandwidth 908 o add or remove endpoints from a DetNet flow 910 o drop DetNet flows completely 912 o falsely create new DetNet flows (exhaust the systems resources, or 913 to enable DetNet flows that are outside the Network Engineer's 914 control) 916 6.3. Segmentation Attacks (injection) 918 6.3.1. Data Plane Segmentation 920 Injection of false messages in a DetNet flow could lead to exhaustion 921 of the available bandwidth for that flow if the routers attribute 922 these false messages to that flow's budget. 924 In a multipath scenario, injected messages will cause increased 925 processor utilization in elimination routers. If enough paths are 926 subject to malicious injection, the legitimate messages can be 927 dropped. Likewise it can cause an increase in buffer usage. In 928 total, it will consume more resources in the routers than normal, 929 giving rise to a resource exhaustion attack on the routers. 931 If a DetNet flow is interrupted, the end application will be affected 932 by what is now a non-deterministic flow. 934 6.3.2. Controller Plane Segmentation 936 In a successful controller plane segmentation attack, control 937 messages are acted on by nodes in the network, unbeknownst to the 938 central controller or the network engineer. This has the potential 939 to: 941 o create new DetNet flows (exhausting resources) 943 o drop existing DetNet flows (denial of service) 945 o add end-stations to a multicast group (loss of privacy) 947 o remove end-stations from a multicast group (reduction of service) 948 o modify the DetNet flow attributes (affecting available bandwidth) 950 6.4. Replication and Elimination 952 The Replication and Elimination is relevant only to data plane 953 messages as controller plane messages are not subject to multipath 954 routing. 956 6.4.1. Increased Attack Surface 958 Covered briefly in Section 6.3, Segmentation Attacks. 960 6.4.2. Header Manipulation at Elimination Routers 962 Covered briefly in Section 6.3, Segmentation Attacks. 964 6.5. Control or Signaling Packet Modification 966 If control packets are subject to manipulation undetected, the 967 network can be severely compromised. 969 6.6. Control or Signaling Packet Injection 971 If an attacker can inject control packets undetected, the network can 972 be severely compromised. 974 6.7. Reconnaissance 976 Of all the attacks, this is one of the most difficult to detect and 977 counter. Often, an attacker will start out by observing the traffic 978 going through the network and use the knowledge gathered in this 979 phase to mount future attacks. 981 The attacker can, at their leisure, observe over time all aspects of 982 the messaging and signalling, learning the intent and purpose of all 983 traffic flows. At some later date, possibly at an important time in 984 an operational context, the attacker can launch a multi-faceted 985 attack, possibly in conjunction with some demand for ransom. 987 The flow-id in the header of the data plane messages gives an 988 attacker a very reliable identifier for DetNet traffic, and this 989 traffic has a high probability of going to lucrative targets. 991 Applications which are ported from a private OT network to the higher 992 visibility DetNet environment may need to be adapted to limit 993 distinctive flow properties that could make them susceptible to 994 reconnaissance. 996 6.8. Attacks on Time Sync Mechanisms 998 Attacks on time sync mechanisms are addressed in [RFC7384]. 1000 6.9. Attacks on Path Choice 1002 This is covered in part in Section 6.3, Segmentation Attacks, and as 1003 with Replication and Elimination (Section 6.4), this is relevant for 1004 DataPlane messages. 1006 7. Security Threat Mitigation 1008 This section describes a set of measures that can be taken to 1009 mitigate the attacks described in Section 5, Security Threats. These 1010 mitigations should be viewed as a toolset that includes several 1011 different and diverse tools. Each application or system will 1012 typically use a subset of these tools, based on a system-specific 1013 threat analysis. 1015 7.1. Path Redundancy 1017 Description 1019 A DetNet flow that can be forwarded simultaneously over multiple 1020 paths. Path replication and elimination [RFC8655] provides 1021 resiliency to dropped or delayed packets. This redundancy 1022 improves the robustness to failures and to on-path attacks. Note: 1023 At the time of this writing, PREOF is not defined for the IP data 1024 plane. 1026 Related attacks 1028 Path redundancy can be used to mitigate various on-path attacks, 1029 including attacks described in Section 5.2.1, Section 5.2.2, 1030 Section 5.2.3, and Section 5.2.7. However it is also possible 1031 that multiple paths may make it more difficult to locate the 1032 source of an on-path attacker. 1034 A delay modulation attack could result in extensively exercising 1035 parts of the code that wouldn't normally be extensively exercised 1036 and thus might expose flaws in the system that might otherwise not 1037 be exposed. 1039 7.2. Integrity Protection 1041 Description 1042 An integrity protection mechanism, such as a hash-based Message 1043 Authentication Code (MAC) can be used to mitigate modification 1044 attacks on IP packets. Such MAC usage needs to be part of a 1045 security association that is established and managed by a security 1046 association protocol (such as IKEv2 for IPsec security 1047 associations). Integrity protection in the controller plane is 1048 discussed in Section 7.6. 1050 Packet Sequence Number Integrity Considerations 1052 The use of PREOF in a DetNet implementation implies the use of a 1053 sequence number for each packet. There is a trust relationship 1054 between the device that adds the sequence number and the device 1055 that removes the sequence number. The sequence number may be end- 1056 to-end source to destination, or may be added/deleted by network 1057 edge devices. The adder and remover(s) have the trust 1058 relationship because they are the ones that ensure that the 1059 sequence numbers are not modifiable. Between those two points, 1060 there may or may not be replication and elimination functions. 1061 The elimination functions must be able to see the sequence 1062 numbers. Therefore any encryption that is done between adders and 1063 removers must not obscure the sequence number. If the sequence 1064 removers and the eliminators are in the same physical device, it 1065 may be possible to obscure the sequence number, however that is a 1066 layer violation, and is not recommended practice. Note: At the 1067 time of this writing, PREOF is not defined for the IP data plane. 1069 Related attacks 1071 Integrity protection mitigates attacks related to modification and 1072 tampering, including the attacks described in Section 5.2.2 and 1073 Section 5.2.4. 1075 7.3. DetNet Node Authentication 1077 Description 1079 Authentication verifies the identity of DetNet nodes (including 1080 DetNet Controller Plane nodes), enabling mitigation of spoofing 1081 attacks. Note that while integrity protection (Section 7.2) 1082 prevents intermediate nodes from modifying information, 1083 authentication (such as provided by IPsec or MACsec) can provide 1084 traffic origin verification, i.e. to verify that each packet in a 1085 DetNet flow is from a trusted source. 1087 Related attacks 1088 DetNet node authentication is used to mitigate attacks related to 1089 spoofing, including the attacks of Section 5.2.2, and 1090 Section 5.2.4. 1092 7.4. Dummy Traffic Insertion 1094 Description 1096 With some queueing methods such as [IEEE802.1Qch-2017] it is 1097 possible to introduce dummy traffic in order to regularize the 1098 timing of packet transmission. 1100 Related attacks 1102 Removing distinctive temporal properties of individual packets or 1103 flows can be used to mitigate against reconnaissance attacks 1104 Section 5.2.6. 1106 7.5. Encryption 1108 Description 1110 DetNet flows can in principle be forwarded in encrypted form at 1111 the DetNet layer, however, regarding encryption of IP headers see 1112 Section 9. 1114 DetNet nodes do not have any need to inspect the payload of any 1115 DetNet packets, making them data-agnostic. This means that end- 1116 to- end encryption at the application layer is an acceptable way 1117 to protect user data. 1119 Encryption can also be applied at the subnet layer, for example 1120 for Ethernet using MACSec, as noted in Section 9. 1122 Related attacks 1124 Encryption can be used to mitigate recon attacks (Section 5.2.6). 1125 However, for a DetNet network to give differentiated quality of 1126 service on a flow-by-flow basis, the network must be able to 1127 identify the flows individually. This implies that in a recon 1128 attack the attacker may also be able to track individual flows to 1129 learn more about the system. 1131 7.5.1. Encryption Considerations for DetNet 1133 Any compute time which is required for encryption and decryption 1134 processing ('crypto') must be included in the flow latency 1135 calculations. Thus, crypto algorithms used in a DetNet must have 1136 bounded worst-case execution times, and these values must be used in 1137 the latency calculations. 1139 Some crypto algorithms are symmetric in encode/decode time (such as 1140 AES) and others are asymmetric (such as public key algorithms). 1141 There are advantages and disadvantages to the use of either type in a 1142 given DetNet context. The discussion in this document relates to the 1143 timing implications of crypto for DetNet; it is assumed that 1144 integrity considerations are covered elsewhere in the literature. 1146 Asymmetrical crypto is typically not used in networks on a packet-by- 1147 packet basis due to its computational cost. For example, if only 1148 endpoint checks or checks at a small number of intermediate points 1149 are required, asymmetric crypto can be used to authenticate 1150 distribution or exchange of a secret symmetric crypto key; a 1151 successful check based on that key will provide traffic origin 1152 verification, as long as the key is kept secret by the participants. 1153 TLS and IKE (for IPsec) are examples of this for endpoint checks. 1155 However, if secret symmetrical keys are used for this purpose the key 1156 must be given to all relays, which increases the probability of a 1157 secret key being leaked. Also, if any relay is compromised or 1158 misbehaving it may inject traffic into the flow. 1160 Alternatively, asymmetric crypto can provide traffic origin 1161 verification at every intermediate node. For example, a DetNet flow 1162 can be associated with an (asymmetric) keypair, such that the private 1163 key is available to the source of the flow and the public key is 1164 distributed with the flow information, allowing verification at every 1165 node for every packet. However, this is more computationally 1166 expensive. 1168 In either case, origin verification also requires replay detection as 1169 part of the security protocol to prevent an attacker from recording 1170 and resending traffic, e.g., as a denial of service attack on flow 1171 forwarding resources. 1173 If crypto keys are to be regenerated over the duration of the flow 1174 then the time required to accomplish this must be accounted for in 1175 the latency calculations. 1177 7.6. Control and Signaling Message Protection 1179 Description 1181 Control and sigaling messages can be protected using 1182 authentication and integrity protection mechanisms. 1184 Related attacks 1186 These mechanisms can be used to mitigate various attacks on the 1187 controller plane, as described in Section 5.2.5, Section 5.2.7 and 1188 Section 5.2.5.1. 1190 7.7. Dynamic Performance Analytics 1192 Description 1194 The expectation is that the network will have a way to monitor to 1195 detect if timing guarantees are not being met, and a way to alert 1196 the controller plane in that event. Information about the network 1197 performance can be gathered in real-time in order to detect 1198 anomalies and unusual behavior that may be the symptom of a 1199 security attack. The gathered information can be based, for 1200 example, on per-flow counters, bandwidth measurement, and 1201 monitoring of packet arrival times. Unusual behavior or 1202 potentially malicious nodes can be reported to a management 1203 system, or can be used as a trigger for taking corrective actions. 1204 The information can be tracked by DetNet end systems and transit 1205 nodes, and exported to a management system, for example using 1206 YANG. 1208 If the monitoring or reporting mechanism itself is attacked or 1209 subverted, this can result in malfunction of the network. The 1210 design of the monitoring system needs to take this into account 1211 based on the specifics of the monitoring or reporting system being 1212 considered. 1214 Related attacks 1216 Performance analytics can be used to mitigate various attacks, 1217 including the ones described in Section 5.2.1 (Delay Attack), 1218 Section 5.2.3 (Resource Segmentation Attack), and Section 5.2.7 1219 (Time Sync Attack). 1221 For example, in the case of data plane delay attacks, one possible 1222 mitigation is to timestamp the data at the source, and timestamp 1223 it again at the destination, and if the resulting latency exceeds 1224 the promised bound, discard that data and warn the operator (and/ 1225 or enter a fail-safe mode). Note that DetNet specifies packet 1226 sequence numbering, however it does not specify use of packet 1227 timestamps, although they may be used by the underlying transport 1228 (for example TSN) to provide the service. 1230 7.8. Mitigation Summary 1232 The following table maps the attacks of Section 5, Security Threats, 1233 to the impacts of Section 6, Security Threat Impacts, and to the 1234 mitigations of the current section. Each row specifies an attack, 1235 the impact of this attack if it is successfully implemented, and 1236 possible mitigation methods. 1238 +----------------------+---------------------+---------------------+ 1239 | Attack | Impact | Mitigations | 1240 +----------------------+---------------------+---------------------+ 1241 |Delay Attack |-Non-deterministic |-Path redundancy | 1242 | | delay |-Performance | 1243 | |-Data disruption | analytics | 1244 | |-Increased resource | | 1245 | | consumption | | 1246 +----------------------+---------------------+---------------------+ 1247 |Reconnaissance |-Enabler for other |-Encryption | 1248 | | attacks |-Dummy traffic | 1249 | | | insertion | 1250 +----------------------+---------------------+---------------------+ 1251 |DetNet Flow Modificat-|-Increased resource |-Path redundancy | 1252 |ion or Spoofing | consumption |-Integrity protection| 1253 | |-Data disruption |-DetNet Node | 1254 | | | authentication | 1255 +----------------------+---------------------+---------------------+ 1256 |Inter-Segment Attack |-Increased resource |-Path redundancy | 1257 | | consumption |-Performance | 1258 | |-Data disruption | analytics | 1259 +----------------------+---------------------+---------------------+ 1260 |Replication: Increased|-All impacts of other|-Integrity protection| 1261 |attack surface | attacks |-DetNet Node | 1262 | | | authentication | 1263 +----------------------+---------------------+---------------------+ 1264 |Replication-related |-Non-deterministic |-Integrity protection| 1265 |Header Manipulation | delay |-DetNet Node | 1266 | |-Data disruption | authentication | 1267 +----------------------+---------------------+---------------------+ 1268 |Path Manipulation |-Enabler for other |-Control message | 1269 | | attacks | protection | 1270 +----------------------+---------------------+---------------------+ 1271 |Path Choice: Increased|-All impacts of other|-Control message | 1272 |Attack Surface | attacks | protection | 1273 +----------------------+---------------------+---------------------+ 1274 |Control or Signaling |-Increased resource |-Control message | 1275 |Packet Modification | consumption | protection | 1276 | |-Non-deterministic | | 1277 | | delay | | 1278 | |-Data disruption | | 1279 +----------------------+---------------------+---------------------+ 1280 |Control or Signaling |-Increased resource |-Control message | 1281 |Packet Injection | consumption | protection | 1282 | |-Non-deterministic | | 1283 | | delay | | 1284 | |-Data disruption | | 1285 +----------------------+---------------------+---------------------+ 1286 |Attacks on Time Sync |-Non-deterministic |-Path redundancy | 1287 |Mechanisms | delay |-Control message | 1288 | |-Increased resource | protection | 1289 | | consumption |-Performance | 1290 | |-Data disruption | analytics | 1291 +----------------------+---------------------+---------------------+ 1293 Figure 3: Mapping Attacks to Impact and Mitigations 1295 8. Association of Attacks to Use Cases 1297 Different attacks can have different impact and/or mitigation 1298 depending on the use case, so we would like to make this association 1299 in our analysis. However since there is a potentially unbounded list 1300 of use cases, we categorize the attacks with respect to the common 1301 themes of the use cases as identified in the Use Case Common Themes 1302 section of the DetNet Use Cases [RFC8578]. 1304 See also Figure 2 for a mapping of the impact of attacks per use case 1305 by industry. 1307 8.1. Association of Attacks to Use Case Common Themes 1309 In this section we review each theme and discuss the attacks that are 1310 applicable to that theme, as well as anything specific about the 1311 impact and mitigations for that attack with respect to that theme. 1312 The table Figure 5, Mapping Between Themes and Attacks, then provides 1313 a summary of the attacks that are applicable to each theme. 1315 8.1.1. Sub-Network Layer 1317 DetNet is expected to run over various transmission mediums, with 1318 Ethernet being the first identified. Attacks such as Delay or 1319 Reconnaissance might be implemented differently on a different 1320 transmission medium, however the impact on the DetNet as a whole 1321 would be essentially the same. We thus conclude that all attacks and 1322 impacts that would be applicable to DetNet over Ethernet (i.e. all 1323 those named in this document) would also be applicable to DetNet over 1324 other transmission mediums. 1326 With respect to mitigations, some methods are specific to the 1327 Ethernet medium, for example time-aware scheduling using 802.1Qbv 1328 [IEEE802.1Qbv-2015] can protect against excessive use of bandwidth at 1329 the ingress - for other mediums, other mitigations would have to be 1330 implemented to provide analogous protection. 1332 8.1.2. Central Administration 1334 A DetNet network can be controlled by a centralized network 1335 configuration and control system. Such a system may be in a single 1336 central location, or it may be distributed across multiple control 1337 entities that function together as a unified control system for the 1338 network. 1340 All attacks named in this document which are relevant to controller 1341 plane packets (and the controller itself) are relevant to this theme, 1342 including Path Manipulation, Path Choice, Control Packet Modification 1343 or Injection, Reconaissance and Attacks on Time Sync Mechanisms. 1345 8.1.3. Hot Swap 1347 A DetNet network is not expected to be "plug and play" - it is 1348 expected that there is some centralized network configuration and 1349 control system. However, the ability to "hot swap" components (e.g. 1350 due to malfunction) is similar enough to "plug and play" that this 1351 kind of behavior may be expected in DetNet networks, depending on the 1352 implementation. 1354 An attack surface related to Hot Swap is that the DetNet network must 1355 at least consider input at runtime from devices that were not part of 1356 the initial configuration of the network. Even a "perfect" (or 1357 "hitless") replacement of a device at runtime would not necessarily 1358 be ideal, since presumably one would want to distinguish it from the 1359 original for OAM purposes (e.g. to report hot swap of a failed 1360 device). 1362 This implies that an attack such as Flow Modification, Spoofing or 1363 Inter-segment (which could introduce packets from a "new" device 1364 (i.e. one heretofore unknown on the network) could be used to exploit 1365 the need to consider such packets (as opposed to rejecting them out 1366 of hand as one would do if one did not have to consider introduction 1367 of a new device). 1369 Similarly if the network was designed to support runtime replacement 1370 of a clock device, then presence (or apparent presence) and thus 1371 consideration of packets from a new such device could affect the 1372 network, or the time sync of the network, for example by initiating a 1373 new Best Master Clock selection process. Thus attacks on time sync 1374 should be considered when designing hot swap type functionality (see 1375 [RFC7384]). 1377 8.1.4. Data Flow Information Models 1379 Data Flow YANG models specific to DetNet networks are specified by 1380 DetNet, and thus are 'new' and thus potentially present a new attack 1381 surface. 1383 8.1.5. L2 and L3 Integration 1385 A DetNet network integrates Layer 2 (bridged) networks (e.g. AVB/TSN 1386 LAN) and Layer 3 (routed) networks via the use of well-known 1387 protocols such as IP, MPLS Pseudowire, and Ethernet. 1389 There are no specific entries in the mapping table Figure 4, however 1390 that does not imply that there could be no relevant attacks related 1391 to L2-L3 integration. 1393 8.1.6. End-to-End Delivery 1395 Packets sent over DetNet are not to be dropped by the network due to 1396 congestion. (Packets may however intentionally be dropped for 1397 intended reasons, e.g. per security measures). 1399 A data plane attack may force packets to be dropped, for example a 1400 "long" Delay or Replication/Elimination or Flow Modification attack. 1402 The same result might be obtained by a controller plane attack, e.g. 1403 Path Manipulation or Signaling Packet Modification. 1405 It may be that such attacks are limited to Internal on-path 1406 attackers, but other possibilities should be considered. 1408 An attack may also cause packets that should not be delivered to be 1409 delivered, such as by forcing packets from one (e.g. replicated) path 1410 to be preferred over another path when they should not be 1411 (Replication attack), or by Flow Modification, or by Path Choice or 1412 Packet Injection. A Time Sync attack could cause a system that was 1413 expecting certain packets at certain times to accept unintended 1414 packets based on compromised system time or time windowing in the 1415 scheduler. 1417 8.1.7. Replacement for Proprietary Fieldbuses and Ethernet-based 1418 Networks 1420 There are many proprietary "field buses" used in today's industrial 1421 and other industries, as well as proprietary non-interoperable 1422 deterministic Ethernet-based networks. DetNet is intended to provide 1423 an open-standards-based alternative to such buses/networks. In cases 1424 where a DetNet intersects with such fieldbuses/networks or their 1425 protocols, such as by protocol emulation or access via a gateway, new 1426 attack surfaces can be opened. 1428 For example an Inter-Segment or Controller plane attack such as Path 1429 Manipulation, Path Choice or Control Packet Modification/Injection 1430 could be used to exploit commands specific to such a protocol, or 1431 that are interpreted differently by the different protocols or 1432 gateway. 1434 8.1.8. Deterministic vs Best-Effort Traffic 1436 Most of the themes described in this document address OT (reserved) 1437 DetNet flows - this item is intended to address issues related to IT 1438 traffic on a DetNet. 1440 DetNet is intended to support coexistence of time-sensitive 1441 operational (OT, deterministic) traffic and information (IT, "best 1442 effort") traffic on the same ("unified") network. 1444 With DetNet, this coexistance will become more common, and 1445 mitigations will need to be established. The fact that the IT 1446 traffic on a DetNet is limited to a corporate controlled network 1447 makes this a less difficult problem compared to being exposed to the 1448 open Internet, however this aspect of DetNet security should not be 1449 underestimated. 1451 An Inter-segment attack can flood the network with IT-type traffic 1452 with the intent of disrupting handling of IT traffic, and/or the goal 1453 of interfering with OT traffic. Presumably if the DetNet flow 1454 reservation and isolation of the DetNet is well-designed (better- 1455 designed than the attack) then interference with OT traffic should 1456 not result from an attack that floods the network with IT traffic. 1458 However the DetNet's handling of IT traffic may not (by design) be as 1459 resilient to DOS attack, and thus designers must be otherwise 1460 prepared to mitigate DOS attacks on IT traffic in a DetNet. 1462 8.1.9. Deterministic Flows 1464 Reserved bandwidth data flows (deterministic flows) must provide the 1465 allocated bandwidth, and must be isolated from each other. 1467 A Spoofing or Inter-segment attack which adds packet traffic to a 1468 bandwidth-reserved DetNet flow could cause that flow to occupy more 1469 bandwidth than it was allocated, resulting in interference with other 1470 DetNet flows. 1472 A Flow Modification or Spoofing or Header Manipulation or Control 1473 Packet Modification attack could cause packets from one flow to be 1474 directed to another flow, thus breaching isolation between the flows. 1476 8.1.10. Unused Reserved Bandwidth 1478 If bandwidth reservations are made for a DetNet flow but the 1479 associated bandwidth is not used at any point in time, that bandwidth 1480 is made available on the network for best-effort traffic. However, 1481 note that security considerations for best-effort traffic on a DetNet 1482 network is out of scope of the present document, provided that such 1483 an attack does not affect performance for DetNet OT traffic. 1485 8.1.11. Interoperability 1487 The DetNet network specifications are intended to enable an ecosystem 1488 in which multiple vendors can create interoperable products, thus 1489 promoting device diversity and potentially higher numbers of each 1490 device manufactured. 1492 Given that the DetNet specifications are unambiguously written and 1493 that the implementations are accurate, then this should not in and of 1494 itself cause a security concern; however, in the real world, it could 1495 be. The network operator can mitigate this through sufficient 1496 interoperability testing. 1498 8.1.12. Cost Reductions 1500 The DetNet network specifications are intended to enable an ecosystem 1501 in which multiple vendors can create interoperable products, thus 1502 promoting higher numbers of each device manufactured, promoting cost 1503 reduction and cost competition among vendors. 1505 This envisioned breadth of DetNet-enabled products is in general a 1506 positive factor, however implementation flaws in any individual 1507 component can present an attack surface. In addition, implementation 1508 differences between components from different vendors can result in 1509 attack surfaces (resulting from their interaction) which may not 1510 exist in any individual component. 1512 Network operators can mitigate such concerns through sufficient 1513 product and interoperability testing. 1515 8.1.13. Insufficiently Secure Devices 1517 The DetNet network specifications are intended to enable an ecosystem 1518 in which multiple vendors can create interoperable products, thus 1519 promoting device diversity and potentially higher numbers of each 1520 device manufactured. However this raises the possibility that a 1521 vendor might repurpose for DetNet applications a hardware or software 1522 component that was originally designed for operation in an isolated 1523 OT network, and thus may not have been designed to be sufficiently 1524 secure, or secure at all. Deployment of such a device on a DetNet 1525 network that is intended to be highly secure may present an attack 1526 surface. 1528 The DetNet network operator may need to take specific actions to 1529 protect such devices, such as implementing a dedicated security layer 1530 around the device. 1532 8.1.14. DetNet Network Size 1534 DetNet networks range in size from very small, e.g. inside a single 1535 industrial machine, to very large, for example a Utility Grid network 1536 spanning a whole country. 1538 The size of the network might be related to how the attack is 1539 introduced into the network, for example if the entire network is 1540 local, there is a threat that power can be cut to the entire network. 1541 If the network is large, perhaps only a part of the network is 1542 attacked. 1544 A Delay attack might be as relevant to a small network as to a large 1545 network, although the amount of delay might be different. 1547 Attacks sourced from IT traffic might be more likely in large 1548 networks, since more people might have access to the network, 1549 presenting a larger attack surface. Similarly Path Manipulation, 1550 Path Choice and Time Sync attacks seem more likely relevant to large 1551 networks. 1553 8.1.15. Multiple Hops 1555 Large DetNet networks (e.g. a Utility Grid network) may involve many 1556 "hops" over various kinds of links for example radio repeaters, 1557 microwave links, fiber optic links, etc. 1559 An attack that takes advantage of flaws (or even normal operation) in 1560 the device drivers for the various links (through internal knowledge 1561 of how the individual driver or firmware operates) could take 1562 proportionately greater advantage of this topology. 1564 It is also possible that this DetNet topology will not be in as 1565 common use as other more homogeneous topologies so there may be more 1566 opportunity for attackers to exploit software and/or protocol flaws 1567 in the implementations which have not been tested through extensive 1568 use, particularly in the case of early adopters. 1570 Of the attacks we have defined, the ones identified in Section 8.1.14 1571 as germane to large networks are the most relevant. 1573 8.1.16. Level of Service 1575 A DetNet is expected to provide means to configure the network that 1576 include querying network path latency, requesting bounded latency for 1577 a given DetNet flow, requesting worst case maximum and/or minimum 1578 latency for a given path or DetNet flow, and so on. It is an 1579 expected case that the network cannot provide a given requested 1580 service level. In such cases the network control system should reply 1581 that the requested service level is not available (as opposed to 1582 accepting the parameter but then not delivering the desired 1583 behavior). 1585 Controller plane attacks such as Signaling Packet Modification and 1586 Injection could be used to modify or create control traffic that 1587 could interfere with the process of a user requesting a level of 1588 service and/or the network's reply. 1590 Reconnaissance could be used to characterize flows and perhaps target 1591 specific flows for attack via the controller plane as noted in 1592 Section 6.7. 1594 8.1.17. Bounded Latency 1596 DetNet provides the expectation of guaranteed bounded latency. 1598 Delay attacks can cause packets to miss their agreed-upon latency 1599 boundaries. 1601 Time Sync attacks can corrupt the system's time reference, resulting 1602 in missed latency deadlines (with respect to the "correct" time 1603 reference). 1605 8.1.18. Low Latency 1607 Applications may require "extremely low latency" however depending on 1608 the application these may mean very different latency values; for 1609 example "low latency" across a Utility grid network is on a different 1610 time scale than "low latency" in a motor control loop in a small 1611 machine. The intent is that the mechanisms for specifying desired 1612 latency include wide ranges, and that architecturally there is 1613 nothing to prevent arbitrarily low latencies from being implemented 1614 in a given network. 1616 Attacks on the controller plane (as described in the Level of Service 1617 theme Section 8.1.16) and Delay and Time attacks (as described in the 1618 Bounded Latency theme Section 8.1.17) both apply here. 1620 8.1.19. Bounded Jitter (Latency Variation) 1622 DetNet is expected to provide bounded jitter (packet to packet 1623 latency variation). 1625 Delay attacks can cause packets to vary in their arrival times, 1626 resulting in packet to packet latency variation, thereby violating 1627 the jitter specification. 1629 8.1.20. Symmetrical Path Delays 1631 Some applications would like to specify that the transit delay time 1632 values be equal for both the transmit and return paths. 1634 Delay attacks can cause path delays to materially differ between 1635 paths. 1637 Time Sync attacks can corrupt the system's time reference, resulting 1638 in path delays that may be perceived to be different (with respect to 1639 the "correct" time reference) even if they are not materially 1640 different. 1642 8.1.21. Reliability and Availability 1644 DetNet based systems are expected to be implemented with essentially 1645 arbitrarily high availability (for example 99.9999% up time, or even 1646 12 nines). The intent is that the DetNet designs should not make any 1647 assumptions about the level of reliability and availability that may 1648 be required of a given system, and should define parameters for 1649 communicating these kinds of metrics within the network. 1651 Any attack on the system, of any type, can affect its overall 1652 reliability and availability, thus in the mapping table Figure 4 we 1653 have marked every attack. Since every DetNet depends to a greater or 1654 lesser degree on reliability and availability, this essentially means 1655 that all networks have to mitigate all attacks, which to a greater or 1656 lesser degree defeats the purpose of associating attacks with use 1657 cases. It also underscores the difficulty of designing "extremely 1658 high reliability" networks. 1660 8.1.22. Redundant Paths 1662 DetNet based systems are expected to be implemented with essentially 1663 arbitrarily high reliability/availability. A strategy used by DetNet 1664 for providing such extraordinarily high levels of reliability is to 1665 provide redundant paths that can be seamlessly switched between, all 1666 the while maintaining the required performance of that system. 1668 Replication-related attacks are by definition applicable here. 1669 Controller plane attacks can also interfere with the configuration of 1670 redundant paths. 1672 8.1.23. Security Measures 1674 A DetNet network must be made secure against devices failures, 1675 attackers, misbehaving component, and so on. If the security 1676 mechanisms protecting the DetNet are attacked or subverted, this can 1677 result in malfunction of the network. The design of the security 1678 system itself needs to take this into account based on the specifics 1679 of the security system being considered. The general topic of 1680 protection of security mechanisms is not unique to DetNet; it is 1681 identical to the case of securing any security mechanism for any 1682 network. The text of this document addresses these concerns to the 1683 extent that they are relevant to DetNet. 1685 8.2. Summary of Attack Types per Use Case Common Theme 1687 The List of Attacks table Figure 4 lists the attacks of Section 5, 1688 Security Threats, assigning a number to each type of attack. That 1689 number is then used as a short form identifier for the attack in 1690 Figure 5, Mapping Between Themes and Attacks. 1692 +----+----------------------------------------+ 1693 | | Attack | 1694 +----+----------------------------------------+ 1695 | 1 |Delay Attack | 1696 +----+----------------------------------------+ 1697 | 2 |DetNet Flow Modification or Spoofing | 1698 +----+----------------------------------------+ 1699 | 3 |Inter-Segment Attack | 1700 +----+----------------------------------------+ 1701 | 4 |Replication: Increased attack surface | 1702 +----+----------------------------------------+ 1703 | 5 |Replication-related Header Manipulation | 1704 +----+----------------------------------------+ 1705 | 6 |Path Manipulation | 1706 +----+----------------------------------------+ 1707 | 7 |Path Choice: Increased Attack Surface | 1708 +----+----------------------------------------+ 1709 | 8 |Control or Signaling Packet Modification| 1710 +----+----------------------------------------+ 1711 | 9 |Control or Signaling Packet Injection | 1712 +----+----------------------------------------+ 1713 | 10 |Reconnaissance | 1714 +----+----------------------------------------+ 1715 | 11 |Attacks on Time Sync Mechanisms | 1716 +--+----------------------------------------+ 1718 Figure 4: List of Attacks 1720 The Mapping Between Themes and Attacks table Figure 5 maps the use 1721 case themes of [RFC8578] (as also enumerated in this document) to the 1722 attacks of Figure 4. Each row specifies a theme, and the attacks 1723 relevant to this theme are marked with a '+'. The row items which 1724 have no threats associated with them are included in the table for 1725 completeness of the list of Use Case Common Themes, and do not have 1726 DetNet-specific threats associated with them. 1728 +----------------------------+--------------------------------+ 1729 | Theme | Attack | 1730 | +--+--+--+--+--+--+--+--+--+--+--+ 1731 | | 1| 2| 3| 4| 5| 6| 7| 8| 9|10|11| 1732 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1733 |Network Layer - AVB/TSN Eth.| +| +| +| +| +| +| +| +| +| +| +| 1734 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1735 |Central Administration | | | | | | +| +| +| +| +| +| 1736 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1737 |Hot Swap | | +| +| | | | | | | | +| 1738 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1739 |Data Flow Information Models| | | | | | | | | | | | 1740 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1741 |L2 and L3 Integration | | | | | | | | | | | | 1742 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1743 |End-to-end Delivery | +| +| +| +| +| +| +| +| +| | +| 1744 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1745 |Proprietary Deterministic | | | +| | | +| +| +| +| | | 1746 |Ethernet Networks | | | | | | | | | | | | 1747 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1748 |Replacement for Proprietary | | | +| | | +| +| +| +| | | 1749 |Fieldbuses | | | | | | | | | | | | 1750 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1751 |Deterministic vs. Best- | | | +| | | | | | | | | 1752 |Effort Traffic | | | | | | | | | | | | 1753 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1754 |Deterministic Flows | | +| +| | +| +| | +| | | | 1755 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1756 |Unused Reserved Bandwidth | | +| +| | | | | +| +| | | 1757 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1758 |Interoperability | | | | | | | | | | | | 1759 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1760 |Cost Reductions | | | | | | | | | | | | 1761 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1762 |Insufficiently Secure | | | | | | | | | | | | 1763 |Devices | | | | | | | | | | | | 1764 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1765 |DetNet Network Size | +| | | | | +| +| | | | +| 1766 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1767 |Multiple Hops | +| +| | | | +| +| | | | +| 1768 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1769 |Level of Service | | | | | | | | +| +| +| | 1770 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1771 |Bounded Latency | +| | | | | | | | | | +| 1772 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1773 |Low Latency | +| | | | | | | +| +| +| +| 1774 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1775 |Bounded Jitter | +| | | | | | | | | | | 1776 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1777 |Symmetric Path Delays | +| | | | | | | | | | +| 1778 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1779 |Reliability and Availability| +| +| +| +| +| +| +| +| +| +| +| 1780 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1781 |Redundant Paths | | | | +| +| | | +| +| | | 1782 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1783 |Security Measures | | | | | | | | | | | | 1784 +----------------------------+--+--+--+--+--+--+--+--+--+--+--+ 1786 Figure 5: Mapping Between Themes and Attacks 1788 8.3. Security Considerations for OAM Traffic 1790 This section considers DetNet-specific security considerations for 1791 packet traffic that is generated and transmitted over a DetNet as 1792 part of OAM (Operations, Administration, and Maintenance). For the 1793 purposes of this discussion, OAM traffic falls into one of two basic 1794 types: 1796 o OAM traffic generated by the network itself. The additional 1797 bandwidth required for such packets is added by the network 1798 administration, presumably transparent to the customer. Security 1799 considerations for such traffic are not DetNet-specific (apart 1800 from such traffic being subject to the same DetNet-specific 1801 security considerations as any other DetNet data flow) and are 1802 thus not covered in this document. 1804 o OAM traffic generated by the customer. From a DetNet security 1805 point of view, DetNet security considerations for such traffic are 1806 exactly the same as for any other customer data flows. 1808 From the perspective of an attack, OAM traffic is indistinguishable 1809 from DetNet traffic and the network needs to be secure against 1810 injection, removal, or modification of traffic of any kind, including 1811 OAM traffic. A DetNet is sensitive to any form of packet injection, 1812 removal or manipulation and in this respect DetNet OAM traffic is no 1813 different. Techniques for securing a DetNet against these threats 1814 have been discussed elsewhere in this document. 1816 9. DetNet Technology-Specific Threats 1818 Section 5, Security Threats, described threats which are independent 1819 of a DetNet implementation. This section considers threats 1820 specifically related to the IP- and MPLS-specific aspects of DetNet 1821 implementations. 1823 The primary security considerations for the data plane specifically 1824 are to maintain the integrity of the data and the delivery of the 1825 associated DetNet service traversing the DetNet network. 1827 The primary relevant differences between IP and MPLS implementations 1828 are in flow identification and OAM methodologies. 1830 As noted in [RFC8655], DetNet operates at the IP layer 1831 ([I-D.ietf-detnet-ip]) and delivers service over sub-layer 1832 technologies such as MPLS ([I-D.ietf-detnet-mpls]) and IEEE 802.1 1833 Time-Sensitive Networking (TSN) ([I-D.ietf-detnet-ip-over-tsn]). 1834 Application flows can be protected through whatever means are 1835 provided by the layer and sub-layer technologies. For example, 1836 technology-specific encryption may be used, such as that provided by 1837 IPSec [RFC4301] for IP flows and/or by an underlying sub-net using 1838 MACSec [IEEE802.1AE-2018] for IP over Ethernet (Layer-2) flows. 1840 However, if the DetNet nodes cannot decrypt IPsec traffic, IPSec may 1841 not be a valid option; this is because the DetNet IP Data Plane 1842 identifies flows via a 6-tuple that consists of two IP addresses, the 1843 transport protocol ID, two transport protocol port numbers and the 1844 DSCP in the IP header. When IPsec is used, the transport header is 1845 encrypted and the next protocol ID is an IPsec protocol, usually ESP, 1846 and not a transport protocol (e.g., neither TCP nor UDP, etc.) 1847 leaving only three components of the 6-tuple, which are the two IP 1848 addresses and the DSCP, which are in general not sufficient to 1849 identify a DetNet flow. 1851 Sections below discuss threats specific to IP and MPLS in more 1852 detail. 1854 9.1. IP 1856 The IP protocol has a long history of security considerations and 1857 architectural protection mechanisms. From a data plane perspective 1858 DetNet does not add or modify any IP header information, so the 1859 carriage of DetNet traffic over an IP data plane does not introduce 1860 any new security issues that were not there before, apart from those 1861 already described in the data-plane-independent threats section 1862 Section 5, Security Threats. 1864 Thus the security considerations for a DetNet based on an IP data 1865 plane are purely inherited from the rich IP Security literature and 1866 code/application base, and the data-plane-independent section of this 1867 document. 1869 Maintaining security for IP segments of a DetNet may be more 1870 challenging than for the MPLS segments of the network, given that the 1871 IP segments of the network may reach the edges of the network, which 1872 are more likely to involve interaction with potentially malevolent 1873 outside actors. Conversely MPLS is inherently more secure than IP 1874 since it is internal to routers and it is well-known how to protect 1875 it from outside influence. 1877 Another way to look at DetNet IP security is to consider it in the 1878 light of VPN security; as an industry we have a lot of experience 1879 with VPNs running through networks with other VPNs, it is well known 1880 how to secure the network for that. However for a DetNet we have the 1881 additional subtlety that any possible interaction of one packet with 1882 another can have a potentially deleterious effect on the time 1883 properties of the flows. So the network must provide sufficient 1884 isolation between flows, for example by protecting the forwarding 1885 bandwidth and related resources so that they are available to detnet 1886 traffic, by whatever means are appropriate for that network's data 1887 plane, for example through the use of queueing mechanisms. 1889 In a VPN, bandwidth is generally guaranteed over a period of time, 1890 whereas in DetNet it is not aggregated over time. This implies that 1891 any VPN-type protection mechanism must also maintain the DetNet 1892 timing constraints. 1894 9.2. MPLS 1896 An MPLS network carrying DetNet traffic is expected to be a "well- 1897 managed" network. Given that this is the case, it is difficult for 1898 an attacker to pass a raw MPLS encoded packet into a network because 1899 operators have considerable experience at excluding such packets at 1900 the network boundaries, as well as excluding MPLS packets being 1901 inserted through the use of a tunnel. 1903 MPLS security is discussed extensively in [RFC5920] ("Security 1904 Framework for MPLS and GMPLS Networks") to which the reader is 1905 referred. 1907 [RFC6941] builds on [RFC5920] by providing additional security 1908 considerations that are applicable to the MPLS-TP extensions 1909 appropriate to the MPLS Transport Profile [RFC5921], and thus to the 1910 operation of DetNet over some types of MPLS network. 1912 [RFC5921] introduces to MPLS new Operations, Administration, and 1913 Maintenance (OAM) capabilities, a transport-oriented path protection 1914 mechanism, and strong emphasis on static provisioning supported by 1915 network management systems. 1917 The operation of DetNet over an MPLS network is modeled on the 1918 operation of multi-segment pseudowires (MS-PW). Thus for guidance on 1919 securing the DetNet elements of DetNet over MPLS the reader is 1920 referred to the MS-PW security mechanisms as defined in [RFC4447], 1921 [RFC3931], [RFC3985], [RFC6073], and [RFC6478]. 1923 Having attended to the conventional aspects of network security it is 1924 necessary to attend to the dynamic aspects. The closest experience 1925 that the IETF has with securing protocols that are sensitive to 1926 manipulation of delay are the two way time transfer protocols (TWTT), 1927 which are NTP [RFC5905] and Precision Time Protocol [IEEE1588]. The 1928 security requirements for these are described in [RFC7384]. 1930 One particular problem that has been observed in operational tests of 1931 TWTT protocols is the ability for two closely but not completely 1932 synchronized flows to beat and cause a sudden phase hit to one of the 1933 flows. This can be mitigated by the careful use of a scheduling 1934 system in the underlying packet transport. 1936 Further consideration of protection against dynamic attacks is work 1937 in progress. New work on MPLS security may also be applicable, for 1938 example [I-D.ietf-mpls-opportunistic-encrypt]. 1940 10. IANA Considerations 1942 This memo includes no requests from IANA. 1944 11. Security Considerations 1946 The security considerations of DetNet networks are presented 1947 throughout this document. 1949 12. Privacy Considerations 1951 Privacy in the context of DetNet is maintained by the base 1952 technologies specific to the DetNet and user traffic. For example 1953 TSN can use MACsec, IP can use IPsec, applications can use IP 1954 transport protocol-provided methods e.g. TLS and DTLS. MPLS 1955 typically uses L2/L3 VPNs combined with the previously mentioned 1956 privacy methods. 1958 13. Contributors 1960 The Editor would like to recognize the contributions of the following 1961 individuals to this draft. 1963 Subir Das (Applied Communication Sciences) 1964 150 Mount Airy Road, Basking Ridge 1965 New Jersey, 07920, USA 1966 email sdas@appcomsci.com 1968 John Dowdell (Airbus Defence and Space) 1969 Celtic Springs, Newport, NP10 8FZ, United Kingdom 1970 email john.dowdell.ietf@gmail.com 1972 Henrik Austad (SINTEF Digital) 1973 Klaebuveien 153, Trondheim, 7037, Norway 1974 email henrik@austad.us 1976 Norman Finn 1977 email nfinn@nfinnconsulting.com 1979 Stewart Bryant 1980 Futurewei Technologies 1981 email: stewart.bryant@gmail.com 1983 David Black 1984 Dell EMC 1985 176 South Street, Hopkinton, MA 01748, USA 1986 email: david.black@dell.com 1988 Carsten Bormann 1990 14. References 1992 14.1. Normative References 1994 [I-D.ietf-detnet-ip] 1995 Varga, B., Farkas, J., Berger, L., Fedyk, D., and S. 1996 Bryant, "DetNet Data Plane: IP", draft-ietf-detnet-ip-07 1997 (work in progress), July 2020. 1999 [I-D.ietf-detnet-mpls] 2000 Varga, B., Farkas, J., Berger, L., Malis, A., Bryant, S., 2001 and J. Korhonen, "DetNet Data Plane: MPLS", draft-ietf- 2002 detnet-mpls-12 (work in progress), September 2020. 2004 [RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas, 2005 "Deterministic Networking Architecture", RFC 8655, 2006 DOI 10.17487/RFC8655, October 2019, 2007 . 2009 14.2. Informative References 2011 [ARINC664P7] 2012 ARINC, "ARINC 664 Aircraft Data Network, Part 7, Avionics 2013 Full-Duplex Switched Ethernet Network", 2009. 2015 [I-D.ietf-detnet-data-plane-framework] 2016 Varga, B., Farkas, J., Berger, L., Malis, A., and S. 2017 Bryant, "DetNet Data Plane Framework", draft-ietf-detnet- 2018 data-plane-framework-06 (work in progress), May 2020. 2020 [I-D.ietf-detnet-flow-information-model] 2021 Varga, B., Farkas, J., Cummings, R., Jiang, Y., and D. 2022 Fedyk, "DetNet Flow Information Model", draft-ietf-detnet- 2023 flow-information-model-10 (work in progress), May 2020. 2025 [I-D.ietf-detnet-ip-over-tsn] 2026 Varga, B., Farkas, J., Malis, A., and S. Bryant, "DetNet 2027 Data Plane: IP over IEEE 802.1 Time Sensitive Networking 2028 (TSN)", draft-ietf-detnet-ip-over-tsn-03 (work in 2029 progress), June 2020. 2031 [I-D.ietf-mpls-opportunistic-encrypt] 2032 Farrel, A. and S. Farrell, "Opportunistic Security in MPLS 2033 Networks", draft-ietf-mpls-opportunistic-encrypt-03 (work 2034 in progress), March 2017. 2036 [I-D.varga-detnet-service-model] 2037 Varga, B. and J. Farkas, "DetNet Service Model", draft- 2038 varga-detnet-service-model-02 (work in progress), May 2039 2017. 2041 [IEEE1588] 2042 IEEE, "IEEE 1588 Standard for a Precision Clock 2043 Synchronization Protocol for Networked Measurement and 2044 Control Systems Version 2", 2008. 2046 [IEEE802.1AE-2018] 2047 IEEE Standards Association, "IEEE Std 802.1AE-2018 MAC 2048 Security (MACsec)", 2018, 2049 . 2051 [IEEE802.1Qbv-2015] 2052 IEEE Standards Association, "IEEE Standard for Local and 2053 metropolitan area networks -- Bridges and Bridged Networks 2054 - Amendment 25: Enhancements for Scheduled Traffic", 2015, 2055 . 2057 [IEEE802.1Qch-2017] 2058 IEEE Standards Association, "IEEE Standard for Local and 2059 metropolitan area networks--Bridges and Bridged Networks-- 2060 Amendment 29: Cyclic Queuing and Forwarding", 2017, 2061 . 2063 [IT_DEF] Wikipedia, "IT Definition", 2020, 2064 . 2066 [OT_DEF] Wikipedia, "OT Definition", 2020, 2067 . 2069 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 2070 "Definition of the Differentiated Services Field (DS 2071 Field) in the IPv4 and IPv6 Headers", RFC 2474, 2072 DOI 10.17487/RFC2474, December 1998, 2073 . 2075 [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., 2076 and W. Weiss, "An Architecture for Differentiated 2077 Services", RFC 2475, DOI 10.17487/RFC2475, December 1998, 2078 . 2080 [RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC 2081 Text on Security Considerations", BCP 72, RFC 3552, 2082 DOI 10.17487/RFC3552, July 2003, 2083 . 2085 [RFC3931] Lau, J., Ed., Townsley, M., Ed., and I. Goyret, Ed., 2086 "Layer Two Tunneling Protocol - Version 3 (L2TPv3)", 2087 RFC 3931, DOI 10.17487/RFC3931, March 2005, 2088 . 2090 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation 2091 Edge-to-Edge (PWE3) Architecture", RFC 3985, 2092 DOI 10.17487/RFC3985, March 2005, 2093 . 2095 [RFC4301] Kent, S. and K. Seo, "Security Architecture for the 2096 Internet Protocol", RFC 4301, DOI 10.17487/RFC4301, 2097 December 2005, . 2099 [RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and 2100 G. Heron, "Pseudowire Setup and Maintenance Using the 2101 Label Distribution Protocol (LDP)", RFC 4447, 2102 DOI 10.17487/RFC4447, April 2006, 2103 . 2105 [RFC5905] Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch, 2106 "Network Time Protocol Version 4: Protocol and Algorithms 2107 Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010, 2108 . 2110 [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS 2111 Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010, 2112 . 2114 [RFC5921] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau, 2115 L., and L. Berger, "A Framework for MPLS in Transport 2116 Networks", RFC 5921, DOI 10.17487/RFC5921, July 2010, 2117 . 2119 [RFC6073] Martini, L., Metz, C., Nadeau, T., Bocci, M., and M. 2120 Aissaoui, "Segmented Pseudowire", RFC 6073, 2121 DOI 10.17487/RFC6073, January 2011, 2122 . 2124 [RFC6478] Martini, L., Swallow, G., Heron, G., and M. Bocci, 2125 "Pseudowire Status for Static Pseudowires", RFC 6478, 2126 DOI 10.17487/RFC6478, May 2012, 2127 . 2129 [RFC6941] Fang, L., Ed., Niven-Jenkins, B., Ed., Mansfield, S., Ed., 2130 and R. Graveman, Ed., "MPLS Transport Profile (MPLS-TP) 2131 Security Framework", RFC 6941, DOI 10.17487/RFC6941, April 2132 2013, . 2134 [RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in 2135 Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384, 2136 October 2014, . 2138 [RFC7835] Saucez, D., Iannone, L., and O. Bonaventure, "Locator/ID 2139 Separation Protocol (LISP) Threat Analysis", RFC 7835, 2140 DOI 10.17487/RFC7835, April 2016, 2141 . 2143 [RFC8578] Grossman, E., Ed., "Deterministic Networking Use Cases", 2144 RFC 8578, DOI 10.17487/RFC8578, May 2019, 2145 . 2147 [RS_DEF] Wikipedia, "RS Definition", 2020, 2148 . 2150 Authors' Addresses 2152 Ethan Grossman (editor) 2153 Dolby Laboratories, Inc. 2154 1275 Market Street 2155 San Francisco, CA 94103 2156 USA 2158 Phone: +1 415 465 4339 2159 Email: ethan@ieee.org 2160 URI: http://www.dolby.com 2162 Tal Mizrahi 2163 Huawei Network.IO Innovation Lab 2165 Email: tal.mizrahi.phd@gmail.com 2167 Andrew J. Hacker 2168 MistIQ Technologies, Inc 2169 Harrisburg, PA 2170 USA 2172 Email: ajhacker@mistiqtech.com 2173 URI: http://www.mistiqtech.com