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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 RTGWG Working Group G. Mirsky 3 Internet-Draft ZTE Corp. 4 Intended status: Informational August 27, 2019 5 Expires: February 28, 2020 7 Identification of Overlay Operations, Administration, and Maintenance 8 (OAM) 9 draft-mirsky-rtgwg-oam-identify-03 11 Abstract 13 This document analyzes how the presence of Operations, 14 Administration, and Maintenance (OAM) control command and/or special 15 data is identified in some overlay networks and an impact on the 16 choice of identification may have on OAM functionality. 18 Status of This Memo 20 This Internet-Draft is submitted in full conformance with the 21 provisions of BCP 78 and BCP 79. 23 Internet-Drafts are working documents of the Internet Engineering 24 Task Force (IETF). Note that other groups may also distribute 25 working documents as Internet-Drafts. The list of current Internet- 26 Drafts is at https://datatracker.ietf.org/drafts/current/. 28 Internet-Drafts are draft documents valid for a maximum of six months 29 and may be updated, replaced, or obsoleted by other documents at any 30 time. It is inappropriate to use Internet-Drafts as reference 31 material or to cite them other than as "work in progress." 33 This Internet-Draft will expire on February 28, 2020. 35 Copyright Notice 37 Copyright (c) 2019 IETF Trust and the persons identified as the 38 document authors. All rights reserved. 40 This document is subject to BCP 78 and the IETF Trust's Legal 41 Provisions Relating to IETF Documents 42 (https://trustee.ietf.org/license-info) in effect on the date of 43 publication of this document. Please review these documents 44 carefully, as they describe your rights and restrictions with respect 45 to this document. Code Components extracted from this document must 46 include Simplified BSD License text as described in Section 4.e of 47 the Trust Legal Provisions and are provided without warranty as 48 described in the Simplified BSD License. 50 Table of Contents 52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 53 2. Conventions used in this document . . . . . . . . . . . . . . 2 54 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 2 55 2.2. Keywords . . . . . . . . . . . . . . . . . . . . . . . . 3 56 3. Overlay Network Encapsulations . . . . . . . . . . . . . . . 3 57 3.1. Encapsulations with Meta-data . . . . . . . . . . . . . . 3 58 3.1.1. Available Solutions . . . . . . . . . . . . . . . . . 5 59 3.2. Fixed-size Encapsulations . . . . . . . . . . . . . . . . 6 60 3.3. Source Information Availability . . . . . . . . . . . . . 7 61 3.4. On-path OAM . . . . . . . . . . . . . . . . . . . . . . . 7 62 4. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 7 63 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 64 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 65 7. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . 8 66 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 8 67 8.1. Normative References . . . . . . . . . . . . . . . . . . 8 68 8.2. Informational References . . . . . . . . . . . . . . . . 8 69 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11 71 1. Introduction 73 Operations, Administration, and Maintenance (OAM) protocols are used 74 to detect, localize defects in the network, and monitor network 75 performance. Some OAM functions, e.g., failure detection, work in 76 the network proactively, while others, e.g., defect localization, 77 usually performed on-demand. These tasks achieved by a combination 78 of active, passive, and hybrid OAM methods, as defined in [RFC7799]. 80 This document analyzes how the presence of Operations, 81 Administration, and Maintenance (OAM) control command and/or special 82 data, i.e., OAM packet, is identified in some overlay networks, and 83 an impact the choice of identification may have on OAM functionality 84 of active and hybrid OAM methods for the respective overlay network 85 encapsulation. 87 2. Conventions used in this document 89 2.1. Terminology 91 AMM Alternate Marking method 93 BIER Bit Indexed Explicit Replication 95 DetNet Deterministic Networks 97 GUE Generic UDP Encapsulation 98 HTS Hybrid Two-step 100 NSH Network Service Header 102 NVO3 Network Virtualization Overlays 104 OAM Operations, Administration and Maintenance 106 SFC Service Function Chaining 108 TLV Type-Length-Value 110 VXLAN-GPE Generic Protocol Extension for VXLAN 112 ACH Associated Channed Header 114 Underlay Network or Underlay Layer: The network that provides 115 connectivity between the DetNet nodes. MPLS network that provides 116 LSP connectivity between DetNet nodes is an example of an underlay 117 layer. 119 2.2. Keywords 121 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 122 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 123 "OPTIONAL" in this document are to be interpreted as described in BCP 124 14 [RFC2119] [RFC8174] when, and only when, they appear in all 125 capitals, as shown here. 127 3. Overlay Network Encapsulations 129 New overlay network encapsulations analyzed in two groups: 131 o encapsulations that support optional meta-data; 133 o fixed-size encapsulations. 135 3.1. Encapsulations with Meta-data 137 Number of the new encapsulation protocols (e.g., Geneve 138 [I-D.ietf-nvo3-geneve], GUE [I-D.ietf-intarea-gue], and SFC NSH 139 [RFC8300]) support use of Type-Length-Value (TLV) encoding to include 140 optional information into the header. The identification of OAM in 141 these protocols is as the following: 143 Geneve: 145 O (1 bit): after the WGLC discussion, the interpretation of the 146 O field has changed. The O field now identifies a control 147 packet. This packet contains a control message. Control 148 messages are sent between tunnel endpoints. Tunnel Endpoints 149 MUST NOT forward the payload and transit devices MUST NOT 150 attempt to interpret it. Since these are infrequent control 151 messages, it is RECOMMENDED that tunnel endpoints direct these 152 packets to a high priority control queue (for example, to 153 direct the packet to a general purpose CPU from a forwarding 154 ASIC or to separate out control traffic on a NIC). Transit 155 devices MUST NOT alter forwarding behavior on the basis of this 156 bit, such as ECMP link selection. 158 [I-D.mmbb-nvo3-geneve-oam] defines the Geneve encapsulation for 159 active OAM. Initially, four options have been presented: 161 + with IP/UDP header demultiplexing active OAM protocols, 162 e.g., Fault Management and Performance Monitoring, can be 163 done using the destination UDP port number. 165 + demultiplex active OAM protocols by the value of the 166 Protocol Type field in the Geneve header. 168 + with using MPLS Generic Associated Channel Label [RFC5586] 169 and Associated Channel Header (ACH) [RFC4385]. Active OAM 170 protocols are demultiplexed using the value of the Channel 171 Type field. 173 + using the new EtherType to identify Geneve OAM and the ACH. 174 Active OAM protocols will be demultiplexed based on the 175 Channel Type field's value. 177 GUE: 179 C-bit provides the separate namespace to carry formatted data 180 that are implicitly addressed to the decapsulator to monitor or 181 control the state or behavior of a tunnel. The payload is 182 interpreted as a control message with the type specified in the 183 proto/ctype field. The format and contents of the control 184 message are indicated by the type and can be variable length. 186 SFC NSH: 188 O bit: Setting this bit indicates an OAM packet. 190 Common between Geneve and NSH is the use of the dedicated flag to 191 identify the OAM packet and, at the same time, the presence of the 192 field that identifies the protocol of the payload that immediately 193 follows after the encapsulation header. [RFC8393] points out that if 194 the value of that field interpreted as none, i.e., no payload follows 195 the header, then OAM may be included in TLVs, thus creating an active 196 OAM packet. The problem with this mechanism to support active OAM 197 methods may be a limitation of the size of data that can be included 198 in a TLV. For example, the maximum size of data in an NSH Meta-data 199 Type 2, as defined in section 2.5.1 [RFC8300], is 512 octets. The 200 maximum length of data in Geneve Option, per section 3.5 201 [I-D.ietf-nvo3-geneve], is 128 octets. Thus, using one TLV as active 202 OAM packet, would not allow creating test packets of larger size, 203 which is useful when measuring packet loss and latency with synthetic 204 traffic as part of the service activation procedure. 206 [I-D.ietf-sfc-oam-framework] suggests that the O bit used to identify 207 OAM packet and the Next Protocol field identifies the OAM function: 209 While the presence of OAM marker in the overlay header (e.g., O 210 bit in the NSH header) indicates it as OAM packet, it is not 211 sufficient to signal for which OAM function the packet is 212 intended. 214 At the same time, some of in-situ OAM proposals, e.g., 215 [I-D.ietf-sfc-ioam-nsh], suggest using TLV to communicate hybrid OAM 216 commands and data. The proposed resolution of using the combination 217 of O bit and the Next Protocol field: 219 ... the O bit MUST NOT be set for regular customer traffic which 220 also carries IOAM data and the O bit MUST be set for OAM packets 221 which carry only IOAM data without any regular data payload. 223 implies that the O bit only identifies the active OAM packet and not 224 set when hybrid OAM methods used. 226 3.1.1. Available Solutions 228 One of the possible solutions for encapsulations with meta-data has 229 been specified in [I-D.ietf-sfc-multi-layer-oam]: 231 To identify the active OAM message the value on the Next Protocol 232 field MUST be set to Active SFC OAM. The rules of interpreting the 233 values of O bit and the Next Protocol field are as follows: 235 o O bit set and the Next Protocol value is not one of identifying 236 active or hybrid OAM protocol (per [RFC7799] definitions), e.g., 237 defined in this specification Active SFC OAM - a Fixed-Length 238 Context Header or Variable-Length Context Header(s) contain OAM 239 command or data and the type of payload determined by the Next 240 Protocol field; 242 o O bit set and the Next Protocol value is one of identifying active 243 or hybrid OAM protocol - the payload that immediately follows SFC 244 NSH contains OAM command or data; 246 o O bit is clear - no OAM in a Fixed-Length Context Header or 247 Variable-Length Context Header(s) and the payload determined by 248 the value of the Next Protocol field; 250 o O bit is clear, and the Next Protocol value is one of identifying 251 active or hybrid OAM protocol MUST be identified and reported as 252 the erroneous combination. An implementation MAY have control to 253 enable processing of the OAM payload. 255 From the above-listed rules follows the recommendation to avoid the 256 combination of OAM in a Fixed-Length Context Header or Variable- 257 Length Context Header(s) and in the payload immediately following the 258 SFC NSH because there is no unambiguous way to identify such 259 combination using the O bit and the Next Protocol field. 261 3.2. Fixed-size Encapsulations 263 Number of the new encapsulation protocols (e.g., VXLAN-GPE 264 [I-D.ietf-nvo3-vxlan-gpe], BIER [RFC8296]) suse fixed-size header. 265 The identification of OAM in these protocols is as the following: 267 VXLAN-GPE: 269 OAM Flag Bit (O bit): The O bit is set to indicate that the 270 packet is an OAM packet. 272 BIER: 274 OAM packet identified by the value of the Next Protocol field. 275 IANA BIER Next Protocol Identifiers registry includes the 276 identifier for OAM (5). 278 The use of a combination of OAM Flag Bit and the Next Protocol field 279 in VXLAN-GPE requires clarification of the header interpretation when 280 the OAM Flag Bit is set, and the value of the Next Protocol field is 281 one of defined in section 3.2 of [I-D.ietf-nvo3-vxlan-gpe]. 283 BIER encapsulation, defined in [RFC8296], identifies OAM message 284 immediately following the BIER header by the value of the Next 285 Protocol field. 287 3.3. Source Information Availability 289 Availability of the packet originator's source information is 290 required for active two-way OAM, e.g., echo request/reply. In cases 291 when the underlay network is IPv4/IPv6 the source information will be 292 derived from the underlay. But when using MPLS underlay network 293 encapsulation of an active OAM packet have to follow specific rules: 295 o if available, use Sender ID in the overlay domain (example BFIR ID 296 in BIER [RFC8296]; 298 o use IP/UDP encapsulation of an OAM packet in the overlay (similar 299 to Section 4.3 [RFC8029]). 301 3.4. On-path OAM 303 In addition to active methods, OAM toolset may include methods that 304 don't use specially constructed and injected in the network test 305 packets. [RFC7799] defines OAM methods that are neither entirely 306 active nor passive but are a combination of both as hybrid methods. 308 One of the examples of the hybrid OAM methods, in-situ OAM, mentioned 309 in Section 3.1. Another example, Alternate Marking method (AMM) 310 [RFC8321], enables on-path OAM functions, e.g., delay and loss 311 measurements, using the data traffic. Because AMM impact on the 312 network can be minimized, measured metrics can be correlated to the 313 network conditions experienced by the specific service. Of all 314 listed in Section 3, BIER allocated the field that may be used for 315 AMM, as discussed in [I-D.ietf-bier-pmmm-oam]. Applicability of AMM 316 to other overlay protocols, i.e., SFC NSH discussed in 317 [I-D.mirsky-sfc-pmamm], Geneve [I-D.fmm-nvo3-pm-alt-mark], and in 318 IPv6 networks [I-D.fioccola-v6ops-ipv6-alt-mark], been actively 319 discussed. 321 Hybrid Two-step (HTS), defined in [I-D.mirsky-ippm-hybrid-two-step], 322 provides on-path collection and transport of the telemetry 323 information. HTS enables accurate and consistent measurements by 324 separating the measurement action from the transporting data while 325 ensuring that the follow-up packet that carries the telemetry 326 information does follow the data packet that had triggered the 327 measurement. 329 4. Conclusions 331 OAM control commands and data may be present as part of the overlay 332 encapsulation header or as a payload that follows the overlay network 333 header. The recommendations: 335 o OAM in the overlay header, if supported by the overlay network, 336 identified by the dedicated flag. Use of this method as active 337 OAM is possible, but functionality is limited. 339 o OAM that follows the overlay header identified as payload type, 340 e.g., by the value of the Next Protocol field. 342 5. IANA Considerations 344 This document does not propose any IANA consideration. This section 345 may be removed. 347 6. Security Considerations 349 This document lists the OAM requirements for a DetNet domain and does 350 not raise any security concerns or issues in addition to ones common 351 to networking. 353 7. Acknowledgment 355 TBD 357 8. References 359 8.1. Normative References 361 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 362 Requirement Levels", BCP 14, RFC 2119, 363 DOI 10.17487/RFC2119, March 1997, 364 . 366 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 367 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 368 May 2017, . 370 8.2. Informational References 372 [I-D.fioccola-v6ops-ipv6-alt-mark] 373 Fioccola, G., Velde, G., Cociglio, M., and P. Muley, "IPv6 374 Performance Measurement with Alternate Marking Method", 375 draft-fioccola-v6ops-ipv6-alt-mark-01 (work in progress), 376 June 2018. 378 [I-D.fmm-nvo3-pm-alt-mark] 379 Fioccola, G., Mirsky, G., and T. Mizrahi, "Performance 380 Measurement (PM) with Alternate Marking in Network 381 Virtualization Overlays (NVO3)", draft-fmm-nvo3-pm-alt- 382 mark-03 (work in progress), October 2018. 384 [I-D.ietf-bier-pmmm-oam] 385 Mirsky, G., Zheng, L., Chen, M., and G. Fioccola, 386 "Performance Measurement (PM) with Marking Method in Bit 387 Index Explicit Replication (BIER) Layer", draft-ietf-bier- 388 pmmm-oam-06 (work in progress), July 2019. 390 [I-D.ietf-intarea-gue] 391 Herbert, T., Yong, L., and O. Zia, "Generic UDP 392 Encapsulation", draft-ietf-intarea-gue-07 (work in 393 progress), March 2019. 395 [I-D.ietf-nvo3-geneve] 396 Gross, J., Ganga, I., and T. Sridhar, "Geneve: Generic 397 Network Virtualization Encapsulation", draft-ietf- 398 nvo3-geneve-13 (work in progress), March 2019. 400 [I-D.ietf-nvo3-vxlan-gpe] 401 Maino, F., Kreeger, L., and U. Elzur, "Generic Protocol 402 Extension for VXLAN", draft-ietf-nvo3-vxlan-gpe-07 (work 403 in progress), April 2019. 405 [I-D.ietf-sfc-ioam-nsh] 406 Brockners, F., Bhandari, S., Govindan, V., Pignataro, C., 407 Gredler, H., Leddy, J., Youell, S., Mizrahi, T., Mozes, 408 D., Lapukhov, P., and R. Chang, "Network Service Header 409 (NSH) Encapsulation for In-situ OAM (IOAM) Data", draft- 410 ietf-sfc-ioam-nsh-01 (work in progress), March 2019. 412 [I-D.ietf-sfc-multi-layer-oam] 413 Mirsky, G., Meng, W., Khasnabish, B., and C. Wang, "Active 414 OAM for Service Function Chains in Networks", draft-ietf- 415 sfc-multi-layer-oam-03 (work in progress), May 2019. 417 [I-D.ietf-sfc-oam-framework] 418 Aldrin, S., Pignataro, C., Kumar, N., Krishnan, R., and A. 419 Ghanwani, "Service Function Chaining (SFC) Operations, 420 Administration and Maintenance (OAM) Framework", draft- 421 ietf-sfc-oam-framework-10 (work in progress), July 2019. 423 [I-D.mirsky-ippm-hybrid-two-step] 424 Mirsky, G., Lingqiang, W., and G. Zhui, "Hybrid Two-Step 425 Performance Measurement Method", draft-mirsky-ippm-hybrid- 426 two-step-03 (work in progress), April 2019. 428 [I-D.mirsky-sfc-pmamm] 429 Mirsky, G., Fioccola, G., and T. Mizrahi, "Performance 430 Measurement (PM) with Alternate Marking Method in Service 431 Function Chaining (SFC) Domain", draft-mirsky-sfc-pmamm-08 432 (work in progress), June 2019. 434 [I-D.mmbb-nvo3-geneve-oam] 435 Mirsky, G., Xiao, M., Boutros, S., and D. Black, "OAM for 436 use in GENEVE", draft-mmbb-nvo3-geneve-oam-00 (work in 437 progress), July 2019. 439 [RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, 440 "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for 441 Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385, 442 February 2006, . 444 [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., 445 "MPLS Generic Associated Channel", RFC 5586, 446 DOI 10.17487/RFC5586, June 2009, 447 . 449 [RFC7799] Morton, A., "Active and Passive Metrics and Methods (with 450 Hybrid Types In-Between)", RFC 7799, DOI 10.17487/RFC7799, 451 May 2016, . 453 [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N., 454 Aldrin, S., and M. Chen, "Detecting Multiprotocol Label 455 Switched (MPLS) Data-Plane Failures", RFC 8029, 456 DOI 10.17487/RFC8029, March 2017, 457 . 459 [RFC8296] Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., 460 Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation 461 for Bit Index Explicit Replication (BIER) in MPLS and Non- 462 MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, January 463 2018, . 465 [RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed., 466 "Network Service Header (NSH)", RFC 8300, 467 DOI 10.17487/RFC8300, January 2018, 468 . 470 [RFC8321] Fioccola, G., Ed., Capello, A., Cociglio, M., Castaldelli, 471 L., Chen, M., Zheng, L., Mirsky, G., and T. Mizrahi, 472 "Alternate-Marking Method for Passive and Hybrid 473 Performance Monitoring", RFC 8321, DOI 10.17487/RFC8321, 474 January 2018, . 476 [RFC8393] Farrel, A. and J. Drake, "Operating the Network Service 477 Header (NSH) with Next Protocol "None"", RFC 8393, 478 DOI 10.17487/RFC8393, May 2018, 479 . 481 Author's Address 483 Greg Mirsky 484 ZTE Corp. 486 Email: gregimirsky@gmail.com