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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-28) exists of draft-ietf-sfc-multi-layer-oam-06 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 SFC WG G. Mirsky 3 Internet-Draft ZTE Corp. 4 Intended status: Standards Track T. Ao 5 Expires: June 17, 2021 Individual contributor 6 Z. Chen 7 China Telecom 8 K. Leung 9 Cisco System 10 G. Mishra 11 Verizon Inc. 12 December 14, 2020 14 SFC OAM for path consistency 15 draft-ao-sfc-oam-path-consistency-09 17 Abstract 19 Service Function Chain (SFC) defines an ordered set of service 20 functions (SFs) to be applied to packets and/or frames and/or flows 21 selected due to classification. SFC Operation, Administration and 22 Maintenance can monitor the continuity of the SFC, i.e., that all SFC 23 elements are reachable to each other in the downstream direction. 24 But SFC OAM must support verification that the order of traversing 25 these SFs corresponds to the state defined by the SFC control plane 26 or orchestrator, the metric referred to in this document as the path 27 consistency of the SFC. This document defines a new SFC active OAM 28 method to support SFC consistency check, i.e., verification that all 29 elements of the given SFC are being traversed in the expected order. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at https://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on June 17, 2021. 48 Copyright Notice 50 Copyright (c) 2020 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (https://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 66 2. Conventions used in this document . . . . . . . . . . . . . . 3 67 2.1. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 3 68 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 69 3. Consistency OAM: Theory of Operation . . . . . . . . . . . . 3 70 3.1. COAM packet . . . . . . . . . . . . . . . . . . . . . . . 4 71 3.2. SFF Information Record TLV . . . . . . . . . . . . . . . 5 72 3.3. SF Information Sub-TLV . . . . . . . . . . . . . . . . . 5 73 3.4. SF Information Sub-TLV Construction . . . . . . . . . . . 7 74 3.4.1. Multiple SFs as hops of SFP . . . . . . . . . . . . . 7 75 3.4.2. Multiple SFs for load balance . . . . . . . . . . . . 7 76 4. Security Considerations . . . . . . . . . . . . . . . . . . . 8 77 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 78 5.1. COAM Message Types . . . . . . . . . . . . . . . . . . . 8 79 5.2. SFF Information Record TLV Type . . . . . . . . . . . . . 9 80 5.3. SF Information Sub-TLV Type . . . . . . . . . . . . . . . 9 81 5.4. SF Identifier Types . . . . . . . . . . . . . . . . . . . 9 82 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 83 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 84 7.1. Normative References . . . . . . . . . . . . . . . . . . 10 85 7.2. Informational References . . . . . . . . . . . . . . . . 11 86 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 88 1. Introduction 90 Service Function Chain (SFC) is a chain with a series of ordered 91 Service Functions (SFs). Service Function Path (SFP) is a path of a 92 SFC. SFC is described in detail in the SFC architecture document 93 [RFC7665]. The SFs in the SFC are ordered, i.e., only when an SF 94 processes traffic, then it can be processed by the next SF. Changes 95 in the order are very likely to cause errors. That's why an operator 96 needs to ensure that the order of traversing the SFs is as defined by 97 the control plane or the orchestrator. This document refers to the 98 correlation between the state of the control plane and the SFP itself 99 as the SFP consistency. The need to verify the consistency of the 100 particular SFP, using a mechanism of an active OAM protocol, is noted 101 in [RFC8924]. 103 This document defines the method to check the path consistency of the 104 SFP. It is an extension of the SFC Echo-request/Echo-reply specified 105 in the [I-D.ietf-sfc-multi-layer-oam]. 107 2. Conventions used in this document 109 2.1. Acronyms 111 SFC: Service Function Chain. An ordered set of some abstract SFs. 113 SFF: Service Function Forwarder 115 SF: Service Function 117 OAM: Operation, Administration and Maintenance 119 SFP: Service Function Path 121 COAM: Consistency OAM, OAM that can be used to check the consistency 122 of the Service Function Path. 124 2.2. Requirements Language 126 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 127 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 128 "OPTIONAL" in this document are to be interpreted as described in BCP 129 14 [RFC2119] [RFC8174] when, and only when, they appear in all 130 capitals, as shown here. 132 3. Consistency OAM: Theory of Operation 134 Consistency OAM (COAM) uses two functions: COAM Request and COAM 135 Reply. Every SFF that receives the COAM Request MUST perform the 136 following actions: 138 o Collect information of the traversed by the COAM Request packet 139 SFs and send it to the ingress SFF as COAM Reply packet over IP 140 network [I-D.ietf-sfc-multi-layer-oam]; 142 o Forward the COAM Request to the next downstream SFF if the one 143 exists. 145 As a result, the ingress SFF collects information about all traversed 146 SFFs and SFs, information on the actual path the COAM packet has 147 traveled. That information is used to verify the SFC's path 148 consistency. The mechanism for the SFP consistency verification is 149 outside the scope of this document. 151 3.1. COAM packet 153 Consistency OAM introduces two new types of messages to the SFC Echo 154 Request/Reply operation defined in [I-D.ietf-sfc-multi-layer-oam] 155 with the following values detailed in Section 5.1: 157 o TBA1 - COAM Request 159 o TBA2 - COAM Reply 161 Upon receiving the COAM Request, the SFF MUST respond with the COAM 162 Reply. The SFF MUST include the SFs information, as described in 163 Section 3.3 and Section 3.2. 165 The COAM packet, defined in [I-D.ietf-sfc-multi-layer-oam], is 166 displayed in Figure 1. 168 0 1 2 3 169 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 171 | Version Number | Global Flags | 172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 173 | Message Type | Reply mode | Return Code | Return S.code | 174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 175 | Sender's Handle | 176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 177 | Sequence Number | 178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 179 | Type | Reserved | Length | 180 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 181 ~ Value ~ 182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 184 Figure 1: COAM Packet Header 186 The initiator of COAM Request MAY require the collected information 187 in the COAM Reply be sent in the integrity-protected mode using the 188 Authentication TLV, defined in [I-D.ietf-sfc-multi-layer-oam]. If 189 the integrity protection of the information in the SFC Return Path 190 TLV is required, then the Authentication TLV MUST be included in the 191 SFC Echo Reply after the SF Information Record TLV. The text used to 192 calculate the hash is the concatenation of the Sender's Handle, 193 Sequence Number fields and the SFF Information Record TLV. If the 194 received SFC Echo Reply includes the Authentication TLV, the 195 authentication of the packet MUST be verified before using any data. 196 If the verification fails, the receiver MUST stop processing the SFF 197 Information Record TLV and notify an operator. Specification of the 198 notification mechanism is outside the scope of this document. 200 3.2. SFF Information Record TLV 202 For COAM Request, the SFF MUST include the Information of SFs into 203 the SF Information Record TLV in the COAM Reply message. Every SFF 204 sends back a single COAM Reply Message, including information on all 205 the SFs attached to the SFF on the SFP as requested in the COAM 206 Request message. 208 0 1 2 3 209 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 210 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 211 |SFF Record TLV | Reserved | Length | 212 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 213 | Service Path Identifier (SPI) | Reserved | 214 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 215 | | 216 | SF Information Sub-TLV | 217 ~ ~ 218 | | 219 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 221 Figure 2: SFF Information Record TLV 223 SFF Information Record TLV is a variable-length TLV that includes the 224 information of all SFFs mapped to the particular SFF instance for the 225 specified SFP. Figure 2 presents the format of an SFC Echo Request/ 226 Reply TLV, where fields are defined as the following: 228 Reserved - one-octet-long field. 230 Service Path Identifier (SPI): The identifier of SFP to which all 231 the SFs in this TLV belong. 233 SF Information Sub-TLV: The Sub-TLV is as defined in Figure 3. 235 3.3. SF Information Sub-TLV 237 Every SFF receiving COAM Request packet MUST include the SF 238 characteristic data into the COAM Reply packet. The data format of 239 an SF sub-TLV, included in a COAM Reply packet, is displayed in 240 Figure 3. 242 After the COAM Request message traverses the SFP, all the information 243 of the SFs on the SFP is collected from the TLVs included in COAM 244 Reply messages. 246 0 1 2 3 247 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 248 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 249 |SF sub-TLV| Reserved | Length | 250 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 251 |Service Index | SF Type | SF ID Type | 252 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 | SF Identifiers | 254 ~ ~ 255 | | 256 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 258 Figure 3: Service Function information sub-TLV 260 SF sub-TLV Type: Two octets long field. It indicates that the TLV is 261 an SF TLV that contains the information of one SF. 263 Length: Two octets long field. The value of the field is the length 264 of the data following the Length field counted in octets. 266 Service Index: Indicates the SF's position on the SFP. 268 SF Type: Two octets long field. It is defined in 269 [I-D.ietf-bess-nsh-bgp-control-plane] and indicates the type of SF, 270 e.g., Firewall, Deep Packet Inspection, WAN optimization controller, 271 etc. 273 Reserved: For future use. MUST be zeroed on transmission and MUST be 274 ignored on receipt. 276 SF ID Type: One octet-long field with values defined as Section 5.4. 278 SF Identifier: An identifier of the SF. The length of the SF 279 Identifier depends on the type of the SF ID Type. For example, if 280 the SF Identifier is its IPv4 address, the SF Identifier should be 32 281 bits. SF ID Type and SF Identifier may be a list, indicating the 282 list of the SFs are which are included in a load balance group. 284 3.4. SF Information Sub-TLV Construction 286 Each SFF in the SFP MUST send one and only one COAM Reply 287 corresponding to the COAM Request. If only one SF is attached to the 288 SFF in such SFP, only one SF information sub-TLV is included in the 289 COAM Reply. If several SFs attached to the SFF in the SFP, SF 290 Information Sub-TLV MUST be constructed as described below in either 291 Section 3.4.1 and Section 3.4.2. 293 3.4.1. Multiple SFs as hops of SFP 295 Multiple SFs attached to the same SFF are the hops of the SFP. The 296 service indexes of these SFs are different. Service function types 297 of these SFs could be different or be the same. Information about 298 all SFs MAY be included in the COAM Reply message. Information about 299 each SF MUST be listed as separate SF Information Sub-TLVs in the 300 COAM Reply message. 302 An example of the COAM procedure for this case is shown in Figure 4. 303 The Service Function Path(SPI=x) is SF1->SF2->SF4->SF3. The SF1, SF2 304 and SF3 are attached to SFF1, and SF4 is attached to SFF2. The COAM 305 Request message is sent to the SFFs in the sequence of the 306 SFP(SFF1->SFF2->SFF1). Every SFF(SFF1, SFF2) replies with the 307 information of SFs belonging to the SFP. The SF information Sub-TLV 308 in Figure 3 contains information for each SF (SF1, SF2, SF3, and 309 SF4). 311 SF1 SF2 SF4 SF3 312 +------+------+ | | 313 COAM Req ......> SFF1 ......> SFF2 ......> SFF1 314 (SPI=x) . . . 315 <............ <.......... <........... 316 COAM Reply1(SF1,SF2) COAM Reply2(SF4) COAM Reply3(SF3) 318 Figure 4: Example 1 for COAM Reply with multiple SFs 320 3.4.2. Multiple SFs for load balance 322 Multiple SFs may be attached to the same SFF to balance the load; in 323 other words, that means that the particular traffic flow will 324 traverse only one of these SFs. These SFs have the same Service 325 Function Type and Service Index. For this case, the SF identifiers 326 and SF ID Type of all these SFs will be listed in the SF Identifiers 327 field and SF ID Type in a single SF information sub-TLV of COAM Reply 328 message. The number of these SFs can be calculated according to SF 329 ID Type and the value of the Length field of the sub-TLV. 331 An example of the COAM procedure for this case is shown in Figure 5. 332 The Service Function Path (SPI=x) is SF1a/SF1b->SF2a/SF2b. The 333 Service Functions SF1a and SF1b are attached to SFF1, which balances 334 the load among them. The Service Functions SF2a and SF2b are 335 attached to SFF2, which, in turn, balances its load between them. 336 The COAM Request message is sent to the SFFs in the sequence of the 337 SFP (i.e. SFF1->SFF2). Every SFF (SFF1, SFF2) replies with the 338 information of SFs belonging to the SFP. The SF information Sub-TLV 339 in Figure 3 contains information for all SFs at that hop. 341 /SF1a /SF2a 342 \SF1b \SF2b 343 | | 344 SFF1 SFF2 345 COAM Req .........> . .........> . 346 (SPI=x) . . 347 <............ <............... 348 COAM Reply1({SF1a,SF1b}) COAM Reply2({SF2a,SF2b}) 350 Figure 5: Example 2 for COAM Reply with multiple SFs 352 4. Security Considerations 354 Security considerations discussed in [RFC8300] and 355 [I-D.ietf-sfc-multi-layer-oam] apply to this document. 357 Also, since Service Function sub-TLV discloses information about the 358 SFP the spoofed COAM Request packet may be used to obtain network 359 information, it is RECOMMENDED that implementations provide a means 360 of checking the source addresses of COAM Request messages, specified 361 in SFC Source TLV [I-D.ietf-sfc-multi-layer-oam], against an access 362 list before accepting the message. 364 5. IANA Considerations 366 5.1. COAM Message Types 368 IANA is requested to assign values from its Message Types sub- 369 registry in SFC Echo Request/Echo Reply Message Types registry as 370 follows: 372 +-------+------------------------------+---------------+ 373 | Value | Description | Reference | 374 +-------+------------------------------+---------------+ 375 | TBA1 | SFP Consistency Echo Request | This document | 376 | TBA2 | SFP Consistency Echo Reply | This document | 377 +-------+------------------------------+---------------+ 379 Table 1: SFP Consistency Echo Request/Echo Reply Message Types 381 5.2. SFF Information Record TLV Type 383 IANA is requested to assign a new type value from SFC OAM TLV Type 384 registry as follows: 386 +-------+-----------------------------+---------------+ 387 | Value | Description | Reference | 388 +-------+-----------------------------+---------------+ 389 | TBA3 | SFF Information Record Type | This document | 390 +-------+-----------------------------+---------------+ 392 Table 2: SFF-Information Record 394 5.3. SF Information Sub-TLV Type 396 IANA is requested to assign a new type value from SFC OAM TLV Type 397 registry as follows: 399 +-------+----------------+---------------+ 400 | Value | Description | Reference | 401 +-------+----------------+---------------+ 402 | TBA4 | SF Information | This document | 403 +-------+----------------+---------------+ 405 Table 3: SF-Information Sub-TLV Type 407 5.4. SF Identifier Types 409 IANA is requested to create in the registry SF Types the new sub- 410 registry SF Identifier Types. All code points in the range 1 through 411 191 in this registry shall be allocated according to the "IETF 412 Review" procedure as specified in [RFC8126] and assign values as 413 follows: 415 +------------+-------------+-------------------------+ 416 | Value | Description | Reference | 417 +------------+-------------+-------------------------+ 418 | 0 | Reserved | This document | 419 | TBA6 | IPv4 | This document | 420 | TBA7 | IPv6 | This document | 421 | TBA8 | MAC | This document | 422 | TBA8+1-191 | Unassigned | IETF Review | 423 | 192-251 | Unassigned | First Come First Served | 424 | 252-254 | Unassigned | Private Use | 425 | 255 | Reserved | This document | 426 +------------+-------------+-------------------------+ 428 Table 4: SF Identifier Type 430 6. Acknowledgements 432 The authors are thankful to John Drake for his review and the 433 reference to the work on BGP Control Plane for NSH SFC. The authors 434 express their appreciation to Joel M. Halpern for his suggestion 435 about the load balancing scenario. The authors also thank Dirk von 436 Hugo, for his useful comments. 438 7. References 440 7.1. Normative References 442 [I-D.ietf-sfc-multi-layer-oam] 443 Mirsky, G., Meng, W., Khasnabish, B., and C. Wang, "Active 444 OAM for Service Function Chains in Networks", draft-ietf- 445 sfc-multi-layer-oam-06 (work in progress), June 2020. 447 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 448 Requirement Levels", BCP 14, RFC 2119, 449 DOI 10.17487/RFC2119, March 1997, 450 . 452 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 453 Writing an IANA Considerations Section in RFCs", BCP 26, 454 RFC 8126, DOI 10.17487/RFC8126, June 2017, 455 . 457 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 458 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 459 May 2017, . 461 [RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed., 462 "Network Service Header (NSH)", RFC 8300, 463 DOI 10.17487/RFC8300, January 2018, 464 . 466 7.2. Informational References 468 [I-D.ietf-bess-nsh-bgp-control-plane] 469 Farrel, A., Drake, J., Rosen, E., Uttaro, J., and L. 470 Jalil, "BGP Control Plane for the Network Service Header 471 in Service Function Chaining", draft-ietf-bess-nsh-bgp- 472 control-plane-18 (work in progress), August 2020. 474 [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function 475 Chaining (SFC) Architecture", RFC 7665, 476 DOI 10.17487/RFC7665, October 2015, 477 . 479 [RFC8924] Aldrin, S., Pignataro, C., Ed., Kumar, N., Ed., Krishnan, 480 R., and A. Ghanwani, "Service Function Chaining (SFC) 481 Operations, Administration, and Maintenance (OAM) 482 Framework", RFC 8924, DOI 10.17487/RFC8924, October 2020, 483 . 485 Authors' Addresses 487 Greg Mirsky 488 ZTE Corp. 489 1900 McCarthy Blvd. #205 490 Milpitas, CA 95035 491 USA 493 Email: gregimirsky@gmail.com 495 Ting Ao 496 Individual contributor 497 No.889, BiBo Road 498 Shanghai 201203 499 China 501 Phone: +86 17721209283 502 Email: 18555817@qq.com 503 Zhonghua Chen 504 China Telecom 505 No.1835, South PuDong Road 506 Shanghai 201203 507 China 509 Phone: +86 18918588897 510 Email: 18918588897@189.cn 512 Kent Leung 513 Cisco System 514 170 West Tasman Drive 515 San Jose, CA 95134 516 USA 518 Email: kleung@cisco.com 520 Gyan Mishra 521 Verizon Inc. 523 Email: gyan.s.mishra@verizon.com