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Mirsky 5 Expires: June 30, 2019 ZTE Corp. 6 Z. Chen 7 China Telecom 8 K. Leung 9 Cisco 10 Dec 27, 2018 12 SFC OAM for path consistency 13 draft-ao-sfc-oam-path-consistency-04 15 Abstract 17 Service Function Chain (SFC) defines an ordered set of service 18 functions (SFs) to be applied to packets and/or frames and/or flows 19 selected as a result of classification. SFC Operation, 20 Administration and Maintenance can monitor the continuity of the SFC, 21 i.e., that all elements of the SFC are reachable to each other in the 22 downstream direction. But SFC OAM must support verification that the 23 order of traversing these SFs corresponds to the state defined by the 24 SFC control plane or orchestrator, the metric referred in this 25 document as the path consistency of the SFC. This document defines a 26 new SFC OAM method to support SFC consistency check, i.e. 27 verification that all elements of the given SFC are being traversed 28 in the expected order. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at https://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on June 30, 2019. 47 Copyright Notice 49 Copyright (c) 2018 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (https://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 65 2. Conventions used in this document . . . . . . . . . . . . . . 3 66 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 67 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 68 3. Consistency OAM: Theory of Operation . . . . . . . . . . . . 3 69 3.1. COAM packet . . . . . . . . . . . . . . . . . . . . . . . 4 70 3.2. SFF Information Record TLV . . . . . . . . . . . . . . . 4 71 3.3. SF Information Sub-TLV . . . . . . . . . . . . . . . . . 5 72 3.4. SF Information Sub-TLV Construction . . . . . . . . . . . 6 73 3.4.1. Multiple SFs as hops of SFP . . . . . . . . . . . . . 6 74 3.4.2. Multiple SFs for load balance . . . . . . . . . . . . 7 75 4. Security Considerations . . . . . . . . . . . . . . . . . . . 7 76 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 77 5.1. COAM Message Types . . . . . . . . . . . . . . . . . . . 8 78 5.2. SFF Information Record TLV Type . . . . . . . . . . . . . 8 79 5.3. SF Information Sub-TLV Type . . . . . . . . . . . . . . . 8 80 5.4. SF Identifier Types . . . . . . . . . . . . . . . . . . . 9 81 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 82 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 83 7.1. Normative References . . . . . . . . . . . . . . . . . . 9 84 7.2. Informational References . . . . . . . . . . . . . . . . 10 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 87 1. Introduction 89 Service Function Chain (SFC) is a chain with a series of ordered 90 Service Functions (SFs). Service Function Path (SFP) is a path of a 91 SFC. SFC is described in detail in the SFC architecture document 92 [RFC7665]. The SFs in the SFC are ordered and only when one SF 93 processes traffic then it can be processed by the next SF. Otherwise 94 errors may occur. Sometimes, a SF needs to use the metadata from its 95 upstream SF process. That's why it's very important for the operator 96 to make sure that the order of traversing the SFs is exactly as 97 defined by the control plane or the orchestrator. This document 98 refers to the correspondence between the state of the control plane 99 and the SFP itself as the SFP consistency. 101 This document defines the method to check the path consistency of the 102 SFP. It is an extension of the SFC Echo-request/Echo-reply specified 103 in the [I-D.ietf-sfc-multi-layer-oam]. 105 2. Conventions used in this document 107 2.1. Terminology 109 SFC(Service Function Chain): An ordered set of some abstract SFs. 111 SFF: Service Function Forwarder 113 SF: Service Function 115 OAM: Operation, Administration and Maintenance 117 SFP: Service Function Path 119 COAM(Consistency OAM): OAM that can be used to check the consistency 120 of the Service Function Path. 122 2.2. Requirements Language 124 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 125 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 126 "OPTIONAL" in this document are to be interpreted as described in BCP 127 14 [RFC2119] [RFC8174] when, and only when, they appear in all 128 capitals, as shown here. 130 3. Consistency OAM: Theory of Operation 132 Consistency OAM uses two functions: COAM Request and COAM Reply. The 133 SFF, that is ingress of the SFP, transmits COAM Request packet. 134 Every intermediate SFF that receives the COAM Request MUST perform 135 the following actions: 137 o Collect information of traversed by the COAM Request packet SFs 138 and send it to the ingress SFF as COAM Reply packet over IP 139 network [I-D.ietf-sfc-multi-layer-oam]; 141 o Forward the COAM Request to next downstream SFF if the one exists. 143 As result, the ingress SFF collects information about all traversed 144 SFFs and SFs, information of the actual path the COAM packet has 145 traveled, so that we can verify the path consistency of the SFC. The 146 mechanism for the SFP consistency verification is outside the scope 147 of this document. 149 3.1. COAM packet 151 Consistency OAM introduces two new types of messages to the SFC Echo 152 request/reply operation [I-D.ietf-sfc-multi-layer-oam] with the 153 following values Section 5.1: 155 o TBA1 - COAM Request 157 o TBA2 - COAM Reply 159 Upon receiving the Consistency OAM(COAM) Request, the SFF MUST 160 respond with the COAM Reply. The SFF MUST include the SFs 161 information, as as described in Section 3.3 and Section 3.2. 163 The COAM packet is displayed in Figure 1. 165 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 1 166 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 167 | Message Type | Reply mode | Return Code | Return S.code | 168 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 169 | Sender's Handle | 170 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 171 | Sequence Number | 172 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 173 | Type | Length | 174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 175 ~ Value ~ 176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 178 Figure 1: COAM Packet Header 180 3.2. SFF Information Record TLV 182 For COAM Request, the SFF MUST include the Information of SFs into 183 the SF Information Record TLV in the COAM Reply message. Every SFF 184 send back one COAM Reply Message with all the SFs that are attaching 185 to the SFF along the SFP indicated by the COAM Request. 187 0 1 2 3 188 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 1 189 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 190 | SFF Record TLV Type | Length | 191 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 192 | Service Path Identifier(SPI) | Reserved | 193 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 194 | | 195 | SF Information Sub-TLV | 196 ~ ~ 197 | | 198 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 200 Figure 2: SFF Information Record TLV 202 Service Path Identifier(SPI): The identifier of SFP to which all the 203 SFs in this TLV belong. 205 SF Information Sub-TLV: The Sub-TLV as defined in Figure 3. 207 3.3. SF Information Sub-TLV 209 Every SFF receiving COAM Request packet MUST include the SF 210 characteristic data into the COAM Reply packet. The per SF data 211 included in COAM Reply packet as SF Information sub-TLV that is 212 displayed in Figure 3. 214 After the COAM traversed the SFP, all the information of the SFs on 215 the SFP are collected from the TLVs with COAM Reply. 217 0 1 2 3 218 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 1 219 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 220 | SF sub-TLV Type | Length | 221 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 222 |Service Index | SF Type | SF ID Type | 223 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 224 | SF Identifiers | 225 ~ ~ 226 | | 227 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 229 Figure 3: Service Function information sub-TLV 231 SF sub-TLV Type: Two octets long field. It indicates that the TLV is 232 a SF TLV which contains the information of one SF. 234 Length: Two octets long field. The value of the field is the length 235 of the data following the Length field counted in octets. 237 Service Index: Indicates the SF's position on the SFP. 239 SF Type: Two octets long field. It is defined in 240 [I-D.ietf-bess-nsh-bgp-control-plane] and indicates the type of SF, 241 e.g., Firewall, Deep Packet Inspection, WAN optimization controller, 242 etc. 244 Reserved: For future use. MUST be zeroed on transmission and MUST be 245 ignored on receipt. 247 SF ID Type: One octet long field with values defined as Section 5.4. 249 SF Identifier: An identifier of the SF. The length of the SF 250 Identifier depends on the type of the SF ID Type. For example, if 251 the SF Identifier is its IPv4 address, the SF Identifier should be 32 252 bits. SF ID Type and SF Identifier may be a list, indicating the 253 list of the SFs are in load balance group. 255 3.4. SF Information Sub-TLV Construction 257 Each SFF in the SFP MUST send one and only one COAM Reply 258 corresponding to the COAM Request. If there is only one SF attached 259 to the SFF in such SFP, only one SF information sub-TLV is included 260 in the on COAM Reply. If there are several SFs attached to the SFF 261 in the SFP, SF Information Sub-TLV MUST be constructed as described 262 below in either Section 3.4.1 and Section 3.4.2. 264 3.4.1. Multiple SFs as hops of SFP 266 Multiple SFs attached to one SFF are the hops of the SFP, the service 267 indexes of these SFs are different. Service function types of these 268 SFs could be different or be the same. Information about all SFs MAY 269 be included in the COAM Reply message. Information about each SF 270 MUST be listed as separate SF Information Sub-TLVs in the COAM Reply 271 message. 273 An example of the COAM procedure for this case is shown in Figure 4. 274 The Service Function Path(SPI=x) is SF1->SF2->SF4->SF3. The SF1,SF2 275 and SF3 are attached to SFF1, and SF4 is attached to SFF2. The COAM 276 Request message is sent to the SFFs in the sequence of the 277 SFP(SFF1->SFF2->SFF1). Every SFF(SFF1,SFF2) replies with the 278 information of SFs belonging to the SFP. The SF information Sub-TLV 279 in Figure 3 contains information for each SF(SF1, SF2,SF3 and SF4). 281 SF1 SF2 SF4 SF3 282 +------+------+ | | 283 COAM Req ......> SFF1 ......> SFF2 ......> SFF1 284 (SPI=x) . . . 285 <............ <.......... <........... 286 COAM Reply1(SF1,SF2) COAM Reply2(SF4) COAM Reply3(SF3) 288 Figure 4: Example 1 for COAM Reply with multiple SFs 290 3.4.2. Multiple SFs for load balance 292 Multiple SFs may be attached to one SFF to balance the load, in other 293 words, that means that the particular traffic flow will transmit only 294 one of these SFs . These SFs have the same Service Function Type and 295 Service Index. For this case, the SF identifiers and SF ID Type of 296 all these SFs will be listed in the SF Identifiers field and SF ID 297 Type in a single SF information sub-TLV of COAM Reply message. The 298 number of these SFs can be calculated according to SF ID Type and the 299 value of Length field of the sub-TLV. 301 An example of the COAM procedure for this case is shown in Figure 4. 302 The Service Function Path(SPI=x) is SF1a/SF1b->SF2a/SF2b. The 303 Service Functions SF1a and SF1b are attached to SFF1 which are load 304 balance for each other, and the Service Functions SF2a and SF2b are 305 attached to SFF2 which are load balance for each other as well. The 306 COAM Request message is sent to the SFFs in the sequence of the SFP 307 (i.e. SFF1->SFF2). Every SFF(SFF1,SFF2) replies with the 308 information of SFs belonging to the SFP. The SF information Sub-TLV 309 in Figure 3 contains information for all SFs at that hop. 311 /SF1a /SF2a 312 \SF1b \SF2b 313 | | 314 SFF1 SFF2 315 COAM Req .........> . .........> . 316 (SPI=x) . . 317 <............ <............... 318 COAM Reply1({SF1a,SF1b}) COAM Reply2({SF2a,SF2b}) 320 Figure 5: Example 2 for COAM Reply with multiple SFs 322 4. Security Considerations 324 Security considerations discussed in [RFC8300] apply to this 325 document. 327 Also, since Service Function sub-TLV discloses information about the 328 SFP the spoofed COAM Request packet may be used to obtain network 329 information, it is RECOMMENDED that implementations provide a means 330 of checking the source addresses of COAM Request messages, specified 331 in SFC Source TLV [I-D.ietf-sfc-multi-layer-oam], against an access 332 list before accepting the message. 334 5. IANA Considerations 336 5.1. COAM Message Types 338 IANA is requested to assign values from its Message Types sub- 339 registry in SFC Echo Request/Echo Reply Message Types registry as 340 follows: 342 +-------+------------------------------+---------------+ 343 | Value | Description | Reference | 344 +-------+------------------------------+---------------+ 345 | TBA1 | SFP Consistency Echo Request | This document | 346 | TBA2 | SFP Consistency Echo Reply | This document | 347 +-------+------------------------------+---------------+ 349 Table 1: SFP Consistency Echo Request/Echo Reply Message Types 351 5.2. SFF Information Record TLV Type 353 IANA is requested to assign new type value from SFC OAM TLV Type 354 registry as follows: 356 +-------+-----------------------------+---------------+ 357 | Value | Description | Reference | 358 +-------+-----------------------------+---------------+ 359 | TBA3 | SFF Information Record Type | This document | 360 +-------+-----------------------------+---------------+ 362 Table 2: SFF-Information Record 364 5.3. SF Information Sub-TLV Type 366 IANA is requested to assign new type value from SFC OAM TLV Type 367 registry as follows: 369 +-------+----------------+---------------+ 370 | Value | Description | Reference | 371 +-------+----------------+---------------+ 372 | TBA4 | SF Information | This document | 373 +-------+----------------+---------------+ 375 Table 3: SF-Information Sub-TLV Type 377 5.4. SF Identifier Types 379 IANA is requested create in the registry SF Types the new sub- 380 registry SF Identifier Types. All code points in the range 1 through 381 191 in this registry shall be allocated according to the "IETF 382 Review" procedure as specified in [RFC8126] and assign values as 383 follows: 385 +------------+-------------+-------------------------+ 386 | Value | Description | Reference | 387 +------------+-------------+-------------------------+ 388 | 0 | Reserved | This document | 389 | TBA6 | IPv4 | This document | 390 | TBA7 | IPv6 | This document | 391 | TBA8 | MAC | This document | 392 | TBA8+1-191 | Unassigned | IETF Review | 393 | 192-251 | Unassigned | First Come First Served | 394 | 252-254 | Unassigned | Private Use | 395 | 255 | Reserved | This document | 396 +------------+-------------+-------------------------+ 398 Table 4: SF Identifier Type 400 6. Acknowledgements 402 Thanks to John Drake for his review and the reference to the work on 403 BGP Control Plane for NSH SFC. 405 Thanks to Joel M. Halpern for their suggestion about the load 406 balance scenario. 408 7. References 410 7.1. Normative References 412 [I-D.ietf-bess-nsh-bgp-control-plane] 413 Farrel, A., Drake, J., Rosen, E., Uttaro, J., and L. 414 Jalil, "BGP Control Plane for NSH SFC", draft-ietf-bess- 415 nsh-bgp-control-plane-04 (work in progress), July 2018. 417 [I-D.ietf-sfc-multi-layer-oam] 418 Mirsky, G., Meng, W., Khasnabish, B., and C. Wang, "Active 419 OAM for Service Function Chains in Networks", draft-ietf- 420 sfc-multi-layer-oam-00 (work in progress), November 2018. 422 [I-D.ietf-sfc-nsh-tlv] 423 Quinn, P., Elzur, U., and S. Majee, "Network Service 424 Header TLVs", draft-ietf-sfc-nsh-tlv-00 (work in 425 progress), January 2018. 427 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 428 Requirement Levels", BCP 14, RFC 2119, 429 DOI 10.17487/RFC2119, March 1997, 430 . 432 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 433 Writing an IANA Considerations Section in RFCs", BCP 26, 434 RFC 8126, DOI 10.17487/RFC8126, June 2017, 435 . 437 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 438 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 439 May 2017, . 441 [RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed., 442 "Network Service Header (NSH)", RFC 8300, 443 DOI 10.17487/RFC8300, January 2018, 444 . 446 7.2. Informational References 448 [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function 449 Chaining (SFC) Architecture", RFC 7665, 450 DOI 10.17487/RFC7665, October 2015, 451 . 453 Authors' Addresses 455 Ting Ao 456 ZTE Corporation 457 No.889, BiBo Road 458 Shanghai 201203 459 China 461 Phone: +86 21 68897642 462 Email: ao.ting@zte.com.cn 463 Greg Mirsky 464 ZTE Corp. 465 1900 McCarthy Blvd. #205 466 Milpitas, CA 95035 467 USA 469 Email: gregimirsky@gmail.com 471 Zhonghua Chen 472 China Telecom 473 No.1835, South PuDong Road 474 Shanghai 201203 475 China 477 Phone: +86 18918588897 478 Email: 18918588897@189.cn 480 Kent Leung 481 Cisco 483 Email: kleung@cisco.com