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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 opsawg F. Brockners 3 Internet-Draft S. Bhandari 4 Intended status: Best Current Practice Cisco 5 Expires: May 2, 2020 D. Bernier 6 Bell Canada 7 October 30, 2019 9 In-situ OAM Deployment 10 draft-brockners-opsawg-ioam-deployment-00 12 Abstract 14 In-situ Operations, Administration, and Maintenance (IOAM) records 15 operational and telemetry information in the packet while the packet 16 traverses a path between two points in the network. This document 17 provides a framework for IOAM deployment and provides best current 18 practices. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at https://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on May 2, 2020. 37 Copyright Notice 39 Copyright (c) 2019 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (https://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Conventions . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 3. IOAM Deployment: Domains And Nodes . . . . . . . . . . . . . 4 57 4. Types of IOAM . . . . . . . . . . . . . . . . . . . . . . . . 5 58 4.1. Per-hop Tracing IOAM . . . . . . . . . . . . . . . . . . 6 59 4.2. Proof of Transit IOAM . . . . . . . . . . . . . . . . . . 8 60 4.3. Edge to Edge IOAM . . . . . . . . . . . . . . . . . . . . 8 61 4.4. Direct Export IOAM . . . . . . . . . . . . . . . . . . . 8 62 5. IOAM Encapsulations . . . . . . . . . . . . . . . . . . . . . 8 63 5.1. IPv6 . . . . . . . . . . . . . . . . . . . . . . . . . . 8 64 5.2. NSH . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 65 5.3. GRE . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 66 5.4. Geneve . . . . . . . . . . . . . . . . . . . . . . . . . 9 67 5.5. Segment Routing . . . . . . . . . . . . . . . . . . . . . 9 68 5.6. Segment Routing for IPv6 . . . . . . . . . . . . . . . . 9 69 5.7. VXLAN-GPE . . . . . . . . . . . . . . . . . . . . . . . . 9 70 6. IOAM Data Export . . . . . . . . . . . . . . . . . . . . . . 9 71 7. IOAM Deployment Considerations . . . . . . . . . . . . . . . 11 72 7.1. IOAM Namespaces . . . . . . . . . . . . . . . . . . . . . 11 73 7.2. IOAM Layering . . . . . . . . . . . . . . . . . . . . . . 12 74 7.3. IOAM Trace Option Types . . . . . . . . . . . . . . . . . 13 75 7.4. Traffic-sets That IOAM Is Applied To . . . . . . . . . . 15 76 7.5. IOAM Loopback Mode . . . . . . . . . . . . . . . . . . . 15 77 7.6. IOAM Active Mode . . . . . . . . . . . . . . . . . . . . 15 78 7.7. Brown Field Deployments: IOAM Unaware Nodes . . . . . . . 16 79 8. IOAM Manageability . . . . . . . . . . . . . . . . . . . . . 16 80 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 81 10. Security Considerations . . . . . . . . . . . . . . . . . . . 16 82 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 83 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 18 84 12.1. Normative References . . . . . . . . . . . . . . . . . . 18 85 12.2. Informative References . . . . . . . . . . . . . . . . . 18 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 21 88 1. Introduction 90 "In-situ" Operations, Administration, and Maintenance (IOAM) records 91 OAM information within the packet while the packet traverses a 92 particular network domain. The term "in-situ" refers to the fact 93 that the OAM data is added to the data packets rather than is being 94 sent within packets specifically dedicated to OAM. IOAM is to 95 complement mechanisms such as Ping or Traceroute, or more recent 96 active probing mechanisms as described in 98 [I-D.lapukhov-dataplane-probe]. In terms of "active" or "passive" 99 OAM, "in-situ" OAM can be considered a hybrid OAM type. "In-situ" 100 mechanisms do not require extra packets to be sent. IOAM adds 101 information to the already available data packets and therefore 102 cannot be considered passive. In terms of the classification given 103 in [RFC7799] IOAM could be portrayed as Hybrid Type 1. IOAM 104 mechanisms can be leveraged where mechanisms using e.g. ICMP do not 105 apply or do not offer the desired results, such as proving that a 106 certain traffic flow takes a pre-defined path, SLA verification for 107 the live data traffic, detailed statistics on traffic distribution 108 paths in networks that distribute traffic across multiple paths, or 109 scenarios in which probe traffic is potentially handled differently 110 from regular data traffic by the network devices. 112 2. Conventions 114 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 115 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 116 document are to be interpreted as described in [RFC2119]. 118 Abbreviations used in this document: 120 E2E Edge to Edge 122 Geneve: Generic Network Virtualization Encapsulation 123 [I-D.ietf-nvo3-geneve] 125 IOAM: In-situ Operations, Administration, and Maintenance 127 MTU: Maximum Transmit Unit 129 NSH: Network Service Header [RFC8300] 131 OAM: Operations, Administration, and Maintenance 133 POT: Proof of Transit 135 SFC: Service Function Chain 137 SID: Segment Identifier 139 SR: Segment Routing 141 VXLAN-GPE: Virtual eXtensible Local Area Network, Generic Protocol 142 Extension [I-D.ietf-nvo3-vxlan-gpe] 144 3. IOAM Deployment: Domains And Nodes 146 IOAM is a network domain specific feature, with "network domain" 147 being a set of network devices or entities within a single 148 administration. IOAM is not targeted for a deployment on the global 149 Internet. The part of the network which employs IOAM is referred to 150 as the "IOAM-Domain". For example, an IOAM-domain can include an 151 enterprise campus using physical connections between devices or an 152 overlay network using virtual connections / tunnels for connectivity 153 between said devices. An IOAM-domain is defined by its perimeter or 154 edge. The operator of an IOAM-domain is expected to put provisions 155 in place to ensure that packets which contain IOAM data fields do not 156 leak beyond the edge of an IOAM domain, e.g. using for example packet 157 filtering methods. The operator should consider the potential 158 operational impact of IOAM to mechanisms such as ECMP processing 159 (e.g. load-balancing schemes based on packet length could be impacted 160 by the increased packet size due to IOAM), path MTU (i.e. ensure that 161 the MTU of all links within a domain is sufficiently large to support 162 the increased packet size due to IOAM) and ICMP message handling. 164 An IOAM-Domain consists of "IOAM encapsulating nodes", "IOAM 165 decapsulating nodes" and "IOAM transit nodes". The role of a node 166 (i.e. encapsulating, transit, decapsulating) is defined within an 167 IOAM-Namespace (see below). A node can have different roles in 168 different IOAM-Namespaces. 170 An "IOAM encapsulating node" incorporates one or more IOAM-Option- 171 Types into packets that IOAM is enabled for. If IOAM is enabled for 172 a selected subset of the traffic, the IOAM encapsulating node is 173 responsible for applying the IOAM functionality to the selected 174 subset. 176 An "IOAM transit node" updates one or more of the IOAM-Data-Fields. 177 If both the Pre-allocated and the Incremental Trace Option-Types are 178 present in the packet, each IOAM transit node will update at most one 179 of these Option-Types. A transit node does not add new IOAM-Option- 180 Types to a packet, and does not change the IOAM-Data-Fields of an 181 IOAM Edge-to-Edge Option-Type. 183 An "IOAM decapsulating node" removes IOAM-Option-Type(s) from 184 packets. 186 The role of an IOAM-encapsulating, IOAM-transit or IOAM-decapsulating 187 node is always performed within a specific IOAM-Namespace. This 188 means that an IOAM node which is e.g. an IOAM-decapsulating node for 189 IOAM-Namespace "A" but not for IOAM-Namespace "B" will only remove 190 the IOAM-Option-Types for IOAM-Namespace "A" from the packet. An 191 IOAM decapsulating node situated at the edge of an IOAM domain 192 removes all IOAM-Option-Types and associated encapsulation headers 193 for all IOAM-Namespaces from the packet. 195 IOAM-Namespaces allow for a namespace-specific definition and 196 interpretation of IOAM-Data-Fields. An interface-id could for 197 example point to a physical interface (e.g., to understand which 198 physical interface of an aggregated link is used when receiving or 199 transmitting a packet) whereas in another case it could refer to a 200 logical interface (e.g., in case of tunnels). Please refer to 201 Section 7.1 for a discussion of IOAM-Namespaces. 203 Export of Export of Export of Export of 204 IOAM data IOAM data IOAM data IOAM data 205 (optional) (optional) (optional) (optional) 206 ^ ^ ^ ^ 207 | | | | 208 | | | | 209 User +---+----+ +---+----+ +---+----+ +---+----+ 210 packets |Encapsu-| | Transit| | Transit| |Decapsu-| 211 -------->|lating |====>| Node |====>| Node |====>|lating |--> 212 |Node | | A | | B | |Node | 213 +--------+ +--------+ +--------+ +--------+ 215 Figure 1: Roles of IOAM nodes 217 IOAM nodes which add or remove the IOAM-Data-Fields can also update 218 the IOAM-Data-Fields at the same time. Or in other words, IOAM 219 encapsulating or decapsulating nodes can also serve as IOAM transit 220 nodes at the same time. Note that not every node in an IOAM domain 221 needs to be an IOAM transit node. For example, a deployment might 222 require that packets traverse a set of firewalls which support IOAM. 223 In that case, only the set of firewall nodes would be IOAM transit 224 nodes rather than all nodes. 226 4. Types of IOAM 228 IOAM supports different modes of operation, which are differentiated 229 by the type of IOAM data fields being carried in the packet, the data 230 being collected, the type of nodes which collect or update data as 231 well as whether and how nodes export IOAM information. 233 o Per-hop tracing: OAM information about each IOAM node a packet 234 traverses is collected and stored within the user data packet as 235 the packet progresses through the IOAM domain. Potential uses of 236 IOAM per-hop tracing include: 238 * Optimization: Understand the different paths different packets 239 traverse between a source and a sink in a network that uses 240 load balancing such as Equal Cost Load Balancing (ECMP). This 241 information could be used to tune the algorithm for ECMP for 242 optimized network resource usage. 244 * Operations/Troubleshooting: Understand which path a particular 245 packet or set of packets take as well as what amount of jitter 246 and delay different nodes in the path contribute to the overall 247 end-to-end delay and jitter. 249 o Proof-of-transit: Information that a verifier node can use to 250 verify whether a packet has traversed all nodes that is supposed 251 to traverse is stored within the user data packet. Proof-of- 252 transit could for example be used to verify that a packet indeed 253 passes through all services of a service function chain (e.g. 254 verify whether a packet indeed traversed the set of firewalls that 255 it is expected to traverse), or whether a packet indeed took the 256 expected path. 258 o Edge-to-edge: OAM information which is specific to the edges of an 259 IOAM domain is collected and stored within the user data packet. 260 Edge-to-Edge OAM could be used to gather operational information 261 about a particular network domain, such as the delay and jitter 262 incurred by that network domain or the traffic matrix of the 263 network domain. 265 o Direct export: OAM information about each IOAM node a packet 266 traverses is collected and immediately exported to a collector. 267 Direct export could be used in situations where per-hop tracing 268 information is desired, but gathering the information within the 269 packet - as with per-hop tracing - is not feasible. Rather than 270 automatically correlating the per-hop tracing information, as done 271 with per-hop tracing, direct export requires a collector to 272 correlate the information from the individual nodes. In addition, 273 all nodes enabled for direct export need to be capable to export 274 the IOAM information to the collector. 276 4.1. Per-hop Tracing IOAM 278 "IOAM tracing data" is expected to be collected at every IOAM transit 279 node that a packet traverses to ensure visibility into the entire 280 path a packet takes within an IOAM-Domain. I.e., in a typical 281 deployment all nodes in an IOAM-Domain would participate in IOAM and 282 thus be IOAM transit nodes, IOAM encapsulating or IOAM decapsulating 283 nodes. If not all nodes within a domain are IOAM capable, IOAM 284 tracing information (i.e., node data, see below) will only be 285 collected on those nodes which are IOAM capable. Nodes which are not 286 IOAM capable will forward the packet without any changes to the IOAM- 287 Data-Fields. The maximum number of hops and the minimum path MTU of 288 the IOAM domain is assumed to be known. 290 IOAM offers two different trace Option-Types, the "incremental" 291 Option-Type as well as the "pre-allocated" Option-Type. For a 292 discussion which of the two option types is the most suitable for an 293 implementation and/or deployment, see Section 7.3. 295 Every node data entry holds information for a particular IOAM transit 296 node that is traversed by a packet. The IOAM decapsulating node 297 removes the IOAM-Option-Type(s) and processes and/or exports the 298 associated data. All IOAM-Data-Fields are defined in the context of 299 an IOAM-Namespace. 301 IOAM tracing can collect the following types of information: 303 o Identification of the IOAM node. An IOAM node identifier can 304 match to a device identifier or a particular control point or 305 subsystem within a device. 307 o Identification of the interface that a packet was received on, 308 i.e. ingress interface. 310 o Identification of the interface that a packet was sent out on, 311 i.e. egress interface. 313 o Time of day when the packet was processed by the node as well as 314 the transit delay. Different definitions of processing time are 315 feasible and expected, though it is important that all devices of 316 an in-situ OAM domain follow the same definition. 318 o Generic data: Format-free information where syntax and semantic of 319 the information is defined by the operator in a specific 320 deployment. For a specific IOAM-Namespace, all IOAM nodes should 321 interpret the generic data the same way. Examples for generic 322 IOAM data include geo-location information (location of the node 323 at the time the packet was processed), buffer queue fill level or 324 cache fill level at the time the packet was processed, or even a 325 battery charge level. 327 o Information to detect whether IOAM trace data was added at every 328 hop or whether certain hops in the domain weren't IOAM transit 329 nodes. 331 o Data that relates to how the packet traversed a node (transit 332 delay, buffer occupancy in case the packet was buffered, queue 333 depth in case the packet was queued) 335 The Option-Types of incremental tracing and pre-allocated tracing are 336 defined in [I-D.ietf-ippm-ioam-data]. 338 4.2. Proof of Transit IOAM 340 IOAM Proof of Transit Option-Type is to support path or service 341 function chain [RFC7665] verification use cases. Proof-of-transit 342 uses methods like nested hashing or nested encryption of the IOAM 343 data or mechanisms such as Shamir's Secret Sharing Schema (SSSS). 345 The IOAM Proof of Transit Option-Type consist of a fixed size "IOAM 346 proof of transit option header" and "IOAM proof of transit option 347 data fields". For details see [I-D.ietf-ippm-ioam-data]. 349 4.3. Edge to Edge IOAM 351 The IOAM Edge-to-Edge Option-Type is to carry data that is added by 352 the IOAM encapsulating node and interpreted by IOAM decapsulating 353 node. The IOAM transit nodes may process the data but must not 354 modify it. 356 The IOAM Edge-to-Edge Option-Type consist of a fixed size "IOAM Edge- 357 to-Edge Option-Type header" and "IOAM Edge-to-Edge Option-Type data 358 fields". For details see [I-D.ietf-ippm-ioam-data]. 360 4.4. Direct Export IOAM 362 Direct Export is an IOAM mode of operation within which IOAM data to 363 be directly exported to a collector rather than being collected 364 within the data packets. The IOAM Direct Export Option-Type consist 365 of a fixed size "IOAM direct export option header". Direct Export 366 for IOAM is defined in [I-D.ioamteam-ippm-ioam-direct-export]. 368 5. IOAM Encapsulations 370 IOAM data fields and associated data types for in-situ OAM are 371 defined in [I-D.ietf-ippm-ioam-data]. The in-situ OAM data field can 372 be transported by a variety of transport protocols, including NSH, 373 Segment Routing, Geneve, IPv6, etc. 375 5.1. IPv6 377 IOAM encapsulation for IPv6 is defined in 378 [I-D.ietf-ippm-ioam-ipv6-options]. IOAM deployment considerations 379 for IPv6 networks are found in 380 [I-D.ioametal-ippm-6man-ioam-ipv6-deployment]. 382 5.2. NSH 384 IOAM encapsulation for NSH is defined in [I-D.ietf-sfc-ioam-nsh]. 386 5.3. GRE 388 IOAM encapsulation for NSH is defined in [I-D.weis-ippm-ioam-eth]. 390 5.4. Geneve 392 IOAM encapsulation for Geneve is defined in 393 [I-D.brockners-ippm-ioam-geneve]. 395 5.5. Segment Routing 397 IOAM encapsulation for Segment Routing is defined in 398 [I-D.gandhi-spring-ioam-sr-mpls]. 400 5.6. Segment Routing for IPv6 402 IOAM encapsulation for Segment Routing over IPv6 is defined in 403 [I-D.ali-spring-ioam-srv6]. 405 5.7. VXLAN-GPE 407 IOAM encapsulation for VXLAN-GPE is defined in 408 [I-D.brockners-ippm-ioam-vxlan-gpe]. 410 6. IOAM Data Export 412 IOAM nodes collect information for packets traversing a domain that 413 supports IOAM. IOAM decapsulating nodes as well as IOAM transit 414 nodes can choose to retrieve IOAM information from the packet, 415 process the information further and export the information using 416 e.g., IPFIX. 418 Raw data export of IOAM data using IPFIX is discussed in 419 [I-D.spiegel-ippm-ioam-rawexport]. "Raw export of IOAM data" refers 420 to a mode of operation where a node exports the IOAM data as it is 421 received in the packet. The exporting node neither interprets, 422 aggregates nor reformats the IOAM data before it is exported. Raw 423 export of IOAM data is to support an operational model where the 424 processing and interpretation of IOAM data is decoupled from the 425 operation of encapsulating/updating/decapsulating IOAM data, which is 426 also referred to as IOAM data-plane operation. The figure below 427 shows the separation of concerns for IOAM export: Exporting IOAM data 428 is performed by the "IOAM node" which performs IOAM data-plane 429 operation, whereas the interpretation of IOAM data is performed by 430 one or several IOAM data processing systems. The separation of 431 concerns is to off-load interpretation, aggregation and formatting of 432 IOAM data from the node which performs data-plane operations. In 433 other words, a node which is focused on data-plane operations, i.e. 434 forwarding of packets and handling IOAM data will not be tasked to 435 also interpret the IOAM data, but can leave this task to another 436 system or a set of systems. For scalability reasons, a single IOAM 437 node could choose to export IOAM data to several IOAM data processing 438 systems. Similarly, there several monitoring systems or analytics 439 systems can be used to further process the data received from the 440 IOAM preprocessing systems. Figure 2 shows an overview of IOAM 441 export, including IOAM data processing systems and monitoring/ 442 analytics systems. 444 +--------------+ 445 +-------------+ | 446 | Monitoring/ | | 447 | Analytics | | 448 | system(s) |-+ 449 +-------------+ 450 ^ 451 | Processed/interpreted/ 452 | aggregated IOAM data 453 | 454 +--------------+ 455 +-------------+ | 456 | IOAM data | | 457 | processing | | 458 | system(s) |-+ 459 +-------------+ 460 ^ 461 | Raw export of 462 | IOAM data 463 | 464 +--------------+-------+------+--------------+ 465 | | | | 466 | | | | 467 User +---+----+ +---+----+ +---+----+ +---+----+ 468 packets |Encapsu-| | Transit| | Transit| |Decapsu-| 469 -------->|lating |====>| Node |====>| Node |====>|lating |--> 470 |Node | | A | | B | |Node | 471 +--------+ +--------+ +--------+ +--------+ 473 Figure 2: IOAM framework with data export 475 7. IOAM Deployment Considerations 477 This section discusses several aspects of an IOAM deployment, 478 including IOAM Namespaces, IOAM Layering, traffic-sets that IOAM is 479 applied to and IOAM loopback mode. 481 7.1. IOAM Namespaces 483 IOAM-Namespaces add further context to IOAM-Option-Types and 484 associated IOAM-Data-Fields. IOAM-Namespaces support several 485 different uses: 487 o IOAM-Namespaces can be used by an operator to distinguish 488 different operational domains. Devices at domain edges can filter 489 on Namespace-IDs to provide for proper IOAM-Domain isolation. 491 o IOAM-Namespaces provide additional context for IOAM-Data-Fields 492 and thus ensure that IOAM-Data-Fields are unique and can be 493 interpreted properly by management stations or network 494 controllers. While, for example, the node identifier field does 495 not need to be unique in a deployment (e.g. an operator may wish 496 to use different node identifiers for different IOAM layers, even 497 within the same device; or node identifiers might not be unique 498 for other organizational reasons, such as after a merger of two 499 formerly separated organizations), the combination of node_id and 500 Namespace-ID will always be unique. Similarly, IOAM-Namespaces 501 can be used to define how certain IOAM-Data-Fields are 502 interpreted: IOAM offers three different timestamp format options. 503 The Namespace-ID can be used to determine the timestamp format. 504 IOAM-Data-Fields (e.g. buffer occupancy) which do not have a unit 505 associated are to be interpreted within the context of a IOAM- 506 Namespace. 508 o IOAM-Namespaces can be used to identify different sets of devices 509 (e.g., different types of devices) in a deployment: If an operator 510 desires to insert different IOAM-Data-Fields based on the device, 511 the devices could be grouped into multiple IOAM-Namespaces. This 512 could be due to the fact that the IOAM feature set differs between 513 different sets of devices, or it could be for reasons of optimized 514 space usage in the packet header. It could also stem from 515 hardware or operational limitations on the size of the trace data 516 that can be added and processed, preventing collection of a full 517 trace for a flow. 519 * Assigning different IOAM Namespace-IDs to different sets of 520 nodes or network partitions and using the Namespace-ID as a 521 selector at the IOAM encapsulating node, a full trace for a 522 flow could be collected and constructed via partial traces in 523 different packets of the same flow. Example: An operator could 524 choose to group the devices of a domain into two IOAM- 525 Namespaces, in a way that at average, only every second hop 526 would be recorded by any device. To retrieve a full view of 527 the deployment, the captured IOAM-Data-Fields of the two IOAM- 528 Namespaces need to be correlated. 530 * Assigning different IOAM Namespace-IDs to different sets of 531 nodes or network partitions and using a separate instance of an 532 IOAM-Option-Type for each Namespace-ID, a full trace for a flow 533 could be collected and constructed via partial traces from each 534 IOAM-Option-Type in each of the packets in the flow. Example: 535 An operator could choose to group the devices of a domain into 536 two IOAM-Namespaces, in a way that each IOAM-Namespace is 537 represented by one of two IOAM-Option-Types in the packet. 538 Each node would record data only for the IOAM-Namespace that it 539 belongs to, ignoring the other IOAM-Option-Type with a IOAM- 540 Namespace to which it doesn't belong. To retrieve a full view 541 of the deployment, the captured IOAM-Data-Fields of the two 542 IOAM-Namespaces need to be correlated. 544 7.2. IOAM Layering 546 If several encapsulation protocols (e.g., in case of tunneling) are 547 stacked on top of each other, IOAM-Data-Fields could be present in 548 different protocol fields at different layers. The behavior follows 549 the ships-in-the-night model, i.e. IOAM-Data-Fields in one layer are 550 independent from IOAM-Data-Fields in another layer. Layering allows 551 operators to instrument the protocol layer they want to measure. The 552 different layers could, but do not have to share the same IOAM 553 encapsulation mechanisms. 555 Figure 3 shows an example of IOAM layering. The figure shows a 556 Geneve tunnel carried over IPv6 which starts at node A and ends at 557 node D. IOAM information is encapsulated in IPv6 as well as in 558 Geneve. At the IPv6 layer, node A is IOAM encapsulating node (into 559 IPv6), node D is the IOAM decapsulating node and node B and node C 560 are IOAM transit nodes. At the Geneve layer, node A is IOAM 561 encapsulating node (into Geneve) and node D is IOAM decapsulating 562 node (from Geneve). The use of IOAM at both layers as shown in the 563 example here could be used to reveal which nodes of an underlay (here 564 the IPv6 network) are traversed by tunneled packet in an overlay 565 (here the Geneve network). 567 +---+----+ +---+----+ 568 User |Geneve | |Geneve | 569 packets |Encapsu-| |Decapsu-| 570 -------->|lating |==================================>|lating |--> 571 | Node | | Node | 572 | A | | D | 573 +--------+ +--------+ 574 ^ ^ 575 | | 576 v v 577 +--------+ +--------+ +--------+ +--------+ 578 |IPv6 | | IPv6 | | IPv6 | |IPv6 | 579 |Encapsu-| | Transit| | Transit| |Decapsu-| 580 |lating |====>| Node |====>| Node |====>|lating | 581 | Node | | | | | | Node | 582 | A | | B | | C | | D | 583 +--------+ +--------+ +--------+ +--------+ 585 Figure 3: IOAM layering example 587 7.3. IOAM Trace Option Types 589 IOAM offers two different IOAM Option-Types for tracing: 590 "Incremental" Trace-Option-Type and "Pre-allocated" Trace-Option- 591 Type. "Incremental" refers to a mode of operation where the packet 592 is expanded at every IOAM node that addes IOAM-Data-Fields. "Pre- 593 Allocated" describes a mode of operation where the IOAM encapsulating 594 node allocates room for all IOAM-Data-Fields in the entire IOAM 595 domain. More specifically: 597 Pre-allocated Trace-Option: This trace option is defined as a 598 container of node data fields with pre-allocated space for each 599 node to populate its information. This option is useful for 600 implementations where it is efficient to allocate the space once 601 and index into the array to populate the data during transit 602 (e.g., software forwarders often fall into this class). 604 Incremental Trace-Option: This trace option is defined as a 605 container of node data fields where each node allocates and pushes 606 its node data immediately following the option header. 608 A deployment can choose to configure and support one or both of the 609 IOAM Trace-Option-Types. The operator decides by means of 610 configuration which Trace-Option-Type(s) will be used for a 611 particular domain. Deployments can mix devices which include either 612 the Incremental Trace-Option-Type or the Pre-allocated Trace-Option- 613 Type, e.g. in case different types of packet forwarders and 614 associated different types of IOAM implementations exist in a 615 deployment. As a result, both Option-Types can be present in a 616 packet. IOAM decapsulating nodes remove both types of Trace-Option- 617 Types from the packet. 619 The two different Option-Types cater to different packet forwarding 620 infrastructures and are to allow an optimized implementation of IOAM 621 tracing: 623 Pre-allocated Trace-Option: For some implementations of packet 624 forwarders it is efficient to allocate the space for the maximum 625 number of nodes that IOAM Trace Data-Fields should be collected 626 from and insert/update information in the packet at flexible 627 locations, based on a pointer retrieved from a field in the 628 packet. The IOAM encapsulating node allocates an array of the 629 size of the maximum number of nodes that IOAM Trace Data-Fields 630 should be collected from. IOAM transit nodes index into the array 631 to populate the data during transit. Software forwarders often 632 fall into this class of packet forwarder implementations. The 633 maximum number of nodes that IOAM information could be collected 634 from is configured by the operator on the IOAM encapsulating node. 635 The operator has to ensure that the packet with the pre-allocated 636 array that carries the IOAM Data-Fields does not exceed the MTU of 637 any of the links in the IOAM domain. 639 Incremental Trace-Option: Looking up a pointer contained in the 640 packet and inserting/updating information at a flexible location 641 in the packet as a result of the pointer lookup is costly for some 642 forwarding infrastructures. Hardware-based packet forwarding 643 infrastructures often fall into this category. Consequently, 644 hardware-based packet forwarders could choose to support the 645 incremental IOAM-Trace-Option-Type. The incremental IOAM-Trace- 646 Option-Type eliminates the need for the IOAM transit nodes to read 647 the full array in the Trace-Option-Type and allows packets to grow 648 to the size of the MTU of the IOAM domain. IOAM transit nodes 649 will expand the packet and insert the IOAM-Data-Fields as long as 650 there is space available in the packet, i.e. as long as the size 651 of the packet stays within the bounds of the MTU of any of the 652 links in the IOAM domain. There is no need for the operator to 653 configure the IOAM encapsulation node with the maximum number of 654 nodes that IOAM information could be collected from. The operator 655 has to ensure that the minimum MTU of any of the links in the IOAM 656 domain is known to all IOAM transit nodes. 658 7.4. Traffic-sets That IOAM Is Applied To 660 IOAM can be deployed on all or only on subsets of the live user 661 traffic,e.g. per interface, based on an access control list or flow 662 specification defining a specific set of traffic, etc. 664 7.5. IOAM Loopback Mode 666 IOAM Loopback is used for triggering each transit device along the 667 path to loop back a copy of the data packet. Loopback allows an IOAM 668 encapsulating node to trace the path to a given destination, and to 669 receive per-hop data about both the forward and the return path. For 670 details on IOAM loopback, please refer to [I-D.ietf-ippm-ioam-flags]. 672 7.6. IOAM Active Mode 674 The IOAM active mode flag indicates that a packet is an active OAM 675 packet as opposed to regular user data traffic. Active mode is 676 expected to be used for active measurement using IOAM. Example use- 677 cases include: 679 o Endpoint active measurement: Synthetic probe packets are sent 680 between the source and destination, traversing the IOAM domain. 681 Since the probe packets are sent between the endpoints, these 682 packets are treated as data packets by the IOAM domain, and do not 683 require special treatment at the IOAM layer. 685 o IOAM active measurement using probe packets: Probe packets are 686 generated and transmitted by the IOAM encapsulating node, and are 687 expected to be terminated by the decapsulating node. Probe 688 packets include a Trace Option-Type (i.e., either incremental or 689 pre-allocated) which has its Active flag set, indicating that the 690 decapsulating node must terminate them. 692 o IOAM active measurement using replicated data packets: Probe 693 packets are created by the encapsulating node by selecting some or 694 all of the en route data packets and replicating them. A selected 695 data packet that is replicated, and its (possibly truncated) copy 696 is forwarded with one or more IOAM option, while the original 697 packet is forwarded normally, without IOAM options. To the extent 698 possible, the original data packet and its replica are forwarded 699 through the same path. The replica includes a Trace Option-Type 700 that has its Active flag set, indicating that the decapsulating 701 node should terminate it. 703 For details on IOAM active mode, please refer to 704 [I-D.ietf-ippm-ioam-flags]. 706 7.7. Brown Field Deployments: IOAM Unaware Nodes 708 A network can consist of a mix of IOAM aware and IOAM unaware nodes. 709 The encapsulation of IOAM-Data-Fields into different protocols (see 710 also Section 5) are defined such that data packets that include IOAM- 711 Data-Fields do not get dropped by IOAM unaware nodes. For example, 712 packets which contain the IOAM-Trace-Option-Types in IPv6 Hop by Hop 713 extension headers are defined with bits to indicate "00 - skip over 714 this option and continue processing the header". This will ensure 715 that when a node that is IOAM unaware receives a packet with IOAM- 716 Data-Fields included, does not drop the packet. 718 Deployments which leverage the IOAM-Trace-Option-Type(s) could 719 benefit from the ability to detect the presence of IOAM unaware 720 nodes, i.e. nodes which forward the packet but do not update/add 721 IOAM-Data-Fields in IOAM-Trace-Option-Type(s). The node data that is 722 defined as part of the IOAM-Trace-Option-Type(s) includes a Hop_Lim 723 field associated to the node identifier to detect missed nodes, i.e. 724 "holes" in the trace. Monitoring/Analytics system(s) could utilize 725 this information to account for the presence of IOAM unaware nodes in 726 the network. 728 8. IOAM Manageability 730 The YANG model for configuring IOAM in network nodes which support 731 IOAM is defined in [I-D.zhou-ippm-ioam-yang]. 733 A deployment can leverage IOAM profiles is to limit the scope of IOAM 734 features, allowing simpler implementation, verification, and 735 interoperability testing in the context of specific use cases that do 736 not require the full functionality of IOAM. An IOAM profile defines 737 a use case or a set of use cases for IOAM, and an associated set of 738 rules that restrict the scope and features of the IOAM specification, 739 thereby limiting it to a subset of the full functionality. IOAM 740 profiles are defined in [I-D.mizrahi-ippm-ioam-profile]. 742 9. IANA Considerations 744 This document does not request any IANA actions. 746 10. Security Considerations 748 As discussed in [RFC7276], a successful attack on an OAM protocol in 749 general, and specifically on IOAM, can prevent the detection of 750 failures or anomalies, or create a false illusion of nonexistent 751 ones. 753 The Proof of Transit Option-Type (Section Section 4.2) is used for 754 verifying the path of data packets. The security considerations of 755 POT are further discussed in [I-D.ietf-sfc-proof-of-transit]. 757 The data elements of IOAM can be used for network reconnaissance, 758 allowing attackers to collect information about network paths, 759 performance, queue states, buffer occupancy and other information. 760 Note that in case IOAM is used in "immediate export" mode (reference 761 to be added in a future revision), the IOAM related trace information 762 would not be available in the customer data packets, but would 763 trigger export of packet related IOAM information at every node. 764 IOAM data export and securing IOAM data export is outside the scope 765 of this document. 767 IOAM can be used as a means for implementing Denial of Service (DoS) 768 attacks, or for amplifying them. For example, a malicious attacker 769 can add an IOAM header to packets in order to consume the resources 770 of network devices that take part in IOAM or collectors that analyze 771 the IOAM data. Another example is a packet length attack, in which 772 an attacker pushes headers associated with IOAM Option-Types into 773 data packets, causing these packets to be increased beyond the MTU 774 size, resulting in fragmentation or in packet drops. 776 Since IOAM options may include timestamps, if network devices use 777 synchronization protocols then any attack on the time protocol 778 [RFC7384] can compromise the integrity of the timestamp-related data 779 fields. 781 At the management plane, attacks may be implemented by misconfiguring 782 or by maliciously configuring IOAM-enabled nodes in a way that 783 enables other attacks. Thus, IOAM configuration should be secured in 784 a way that authenticates authorized users and verifies the integrity 785 of configuration procedures. 787 Notably, IOAM is expected to be deployed in specific network domains, 788 thus confining the potential attack vectors to within the network 789 domain. Indeed, in order to limit the scope of threats to within the 790 current network domain the network operator is expected to enforce 791 policies that prevent IOAM traffic from leaking outside of the IOAM 792 domain, and prevent IOAM data from outside the domain to be processed 793 and used within the domain. Note that the Immediate Export mode 794 (reference to be added in a future revision) can mitigate the 795 potential threat of IOAM data leaking through data packets. 797 11. Acknowledgements 799 The authors would like to thank Tal Mizrahi, Eric Vyncke, Nalini 800 Elkins, Srihari Raghavan, Ranganathan T S, Barak Gafni, Karthik Babu 801 Harichandra Babu, Akshaya Nadahalli, LJ Wobker, Erik Nordmark, 802 Vengada Prasad Govindan, Andrew Yourtchenko, Aviv Kfir, Tianran Zhou, 803 Zhenbin (Robin), Joe Clarke, Al Morton, Tom Herbet, Haoyu song, and 804 Mickey Spiegel for the comments and advice on IOAM. 806 12. References 808 12.1. Normative References 810 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 811 Requirement Levels", BCP 14, RFC 2119, 812 DOI 10.17487/RFC2119, March 1997, 813 . 815 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 816 Writing an IANA Considerations Section in RFCs", BCP 26, 817 RFC 8126, DOI 10.17487/RFC8126, June 2017, 818 . 820 12.2. Informative References 822 [I-D.ali-spring-ioam-srv6] 823 Ali, Z., Gandhi, R., Filsfils, C., Brockners, F., Kumar, 824 N., Pignataro, C., Li, C., Chen, M., and G. Dawra, 825 "Segment Routing Header encapsulation for In-situ OAM 826 Data", draft-ali-spring-ioam-srv6-01 (work in progress), 827 July 2019. 829 [I-D.brockners-ippm-ioam-geneve] 830 Brockners, F., Bhandari, S., Govindan, V., Pignataro, C., 831 Gredler, H., Leddy, J., Youell, S., Mizrahi, T., Lapukhov, 832 P., Gafni, B., Kfir, A., and M. Spiegel, "Geneve 833 encapsulation for In-situ OAM Data", draft-brockners-ippm- 834 ioam-geneve-03 (work in progress), September 2019. 836 [I-D.brockners-ippm-ioam-vxlan-gpe] 837 Brockners, F., Bhandari, S., Govindan, V., Pignataro, C., 838 Gredler, H., Leddy, J., Youell, S., Mizrahi, T., Kfir, A., 839 Gafni, B., Lapukhov, P., and M. Spiegel, "VXLAN-GPE 840 Encapsulation for In-situ OAM Data", draft-brockners-ippm- 841 ioam-vxlan-gpe-02 (work in progress), July 2019. 843 [I-D.gandhi-spring-ioam-sr-mpls] 844 Gandhi, R., Ali, Z., Filsfils, C., Brockners, F., Wen, B., 845 and V. Kozak, "Segment Routing with MPLS Data Plane 846 Encapsulation for In-situ OAM Data", draft-gandhi-spring- 847 ioam-sr-mpls-02 (work in progress), August 2019. 849 [I-D.ietf-ippm-ioam-data] 850 Brockners, F., Bhandari, S., Pignataro, C., Gredler, H., 851 Leddy, J., Youell, S., Mizrahi, T., Mozes, D., Lapukhov, 852 P., remy@barefootnetworks.com, r., daniel.bernier@bell.ca, 853 d., and J. Lemon, "Data Fields for In-situ OAM", draft- 854 ietf-ippm-ioam-data-08 (work in progress), October 2019. 856 [I-D.ietf-ippm-ioam-flags] 857 Mizrahi, T., Brockners, F., Bhandari, S., Sivakolundu, R., 858 Pignataro, C., Kfir, A., Gafni, B., Spiegel, M., and J. 859 Lemon, "In-situ OAM Flags", draft-ietf-ippm-ioam-flags-00 860 (work in progress), October 2019. 862 [I-D.ietf-ippm-ioam-ipv6-options] 863 Bhandari, S., Brockners, F., Pignataro, C., Gredler, H., 864 Leddy, J., Youell, S., Mizrahi, T., Kfir, A., Gafni, B., 865 Lapukhov, P., Spiegel, M., Krishnan, S., and R. Asati, 866 "In-situ OAM IPv6 Options", draft-ietf-ippm-ioam- 867 ipv6-options-00 (work in progress), September 2019. 869 [I-D.ietf-ntp-packet-timestamps] 870 Mizrahi, T., Fabini, J., and A. Morton, "Guidelines for 871 Defining Packet Timestamps", draft-ietf-ntp-packet- 872 timestamps-07 (work in progress), August 2019. 874 [I-D.ietf-nvo3-geneve] 875 Gross, J., Ganga, I., and T. Sridhar, "Geneve: Generic 876 Network Virtualization Encapsulation", draft-ietf- 877 nvo3-geneve-14 (work in progress), September 2019. 879 [I-D.ietf-nvo3-vxlan-gpe] 880 Maino, F., Kreeger, L., and U. Elzur, "Generic Protocol 881 Extension for VXLAN", draft-ietf-nvo3-vxlan-gpe-08 (work 882 in progress), October 2019. 884 [I-D.ietf-sfc-ioam-nsh] 885 Brockners, F. and S. Bhandari, "Network Service Header 886 (NSH) Encapsulation for In-situ OAM (IOAM) Data", draft- 887 ietf-sfc-ioam-nsh-02 (work in progress), September 2019. 889 [I-D.ietf-sfc-proof-of-transit] 890 Brockners, F., Bhandari, S., Mizrahi, T., Dara, S., and S. 891 Youell, "Proof of Transit", draft-ietf-sfc-proof-of- 892 transit-03 (work in progress), September 2019. 894 [I-D.ioametal-ippm-6man-ioam-ipv6-deployment] 895 Bhandari, S., Brockners, F., Mizrahi, T., Kfir, A., Gafni, 896 B., Spiegel, M., Krishnan, S., and M. Smith, "Deployment 897 Considerations for In-situ OAM with IPv6 Options", draft- 898 ioametal-ippm-6man-ioam-ipv6-deployment-02 (work in 899 progress), September 2019. 901 [I-D.ioamteam-ippm-ioam-direct-export] 902 Song, H., Gafni, B., Zhou, T., Li, Z., Brockners, F., 903 Bhandari, S., Sivakolundu, R., and T. Mizrahi, "In-situ 904 OAM Direct Exporting", draft-ioamteam-ippm-ioam-direct- 905 export-00 (work in progress), October 2019. 907 [I-D.kitamura-ipv6-record-route] 908 Kitamura, H., "Record Route for IPv6 (PR6) Hop-by-Hop 909 Option Extension", draft-kitamura-ipv6-record-route-00 910 (work in progress), November 2000. 912 [I-D.lapukhov-dataplane-probe] 913 Lapukhov, P. and r. remy@barefootnetworks.com, "Data-plane 914 probe for in-band telemetry collection", draft-lapukhov- 915 dataplane-probe-01 (work in progress), June 2016. 917 [I-D.mizrahi-ippm-ioam-profile] 918 Mizrahi, T., Brockners, F., Bhandari, S., Sivakolundu, R., 919 Pignataro, C., Kfir, A., Gafni, B., Spiegel, M., Zhou, T., 920 and J. Lemon, "In Situ OAM Profiles", draft-mizrahi-ippm- 921 ioam-profile-01 (work in progress), September 2019. 923 [I-D.spiegel-ippm-ioam-rawexport] 924 Spiegel, M., Brockners, F., Bhandari, S., and R. 925 Sivakolundu, "In-situ OAM raw data export with IPFIX", 926 draft-spiegel-ippm-ioam-rawexport-02 (work in progress), 927 July 2019. 929 [I-D.weis-ippm-ioam-eth] 930 Weis, B., Brockners, F., Hill, C., Bhandari, S., Govindan, 931 V., Pignataro, C., Gredler, H., Leddy, J., Youell, S., 932 Mizrahi, T., Kfir, A., Gafni, B., Lapukhov, P., and M. 933 Spiegel, "EtherType Protocol Identification of In-situ OAM 934 Data", draft-weis-ippm-ioam-eth-02 (work in progress), 935 September 2019. 937 [I-D.zhou-ippm-ioam-yang] 938 Zhou, T., Guichard, J., Brockners, F., and S. Raghavan, "A 939 YANG Data Model for In-Situ OAM", draft-zhou-ippm-ioam- 940 yang-04 (work in progress), June 2019. 942 [RFC7276] Mizrahi, T., Sprecher, N., Bellagamba, E., and Y. 943 Weingarten, "An Overview of Operations, Administration, 944 and Maintenance (OAM) Tools", RFC 7276, 945 DOI 10.17487/RFC7276, June 2014, 946 . 948 [RFC7384] Mizrahi, T., "Security Requirements of Time Protocols in 949 Packet Switched Networks", RFC 7384, DOI 10.17487/RFC7384, 950 October 2014, . 952 [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function 953 Chaining (SFC) Architecture", RFC 7665, 954 DOI 10.17487/RFC7665, October 2015, 955 . 957 [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with 958 Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, 959 May 2016, . 961 [RFC7820] Mizrahi, T., "UDP Checksum Complement in the One-Way 962 Active Measurement Protocol (OWAMP) and Two-Way Active 963 Measurement Protocol (TWAMP)", RFC 7820, 964 DOI 10.17487/RFC7820, March 2016, 965 . 967 [RFC7821] Mizrahi, T., "UDP Checksum Complement in the Network Time 968 Protocol (NTP)", RFC 7821, DOI 10.17487/RFC7821, March 969 2016, . 971 [RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed., 972 "Network Service Header (NSH)", RFC 8300, 973 DOI 10.17487/RFC8300, January 2018, 974 . 976 Authors' Addresses 978 Frank Brockners 979 Cisco Systems, Inc. 980 Hansaallee 249, 3rd Floor 981 DUESSELDORF, NORDRHEIN-WESTFALEN 40549 982 Germany 984 Email: fbrockne@cisco.com 985 Shwetha Bhandari 986 Cisco Systems, Inc. 987 Cessna Business Park, Sarjapura Marathalli Outer Ring Road 988 Bangalore, KARNATAKA 560 087 989 India 991 Email: shwethab@cisco.com 993 Daniel Bernier 994 Bell Canada 995 Canada 997 Email: daniel.bernier@bell.ca