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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 SPRING J. Guichard, Ed. 3 Internet-Draft Futurewei Technologies 4 Intended status: Standards Track J. Tantsura, Ed. 5 Expires: December 10, 2021 Apstra inc. 6 June 8, 2021 8 Integration of Network Service Header (NSH) and Segment Routing for 9 Service Function Chaining (SFC) 10 draft-ietf-spring-nsh-sr-06 12 Abstract 14 This document describes the integration of Network Service Header 15 (NSH) and Segment Routing (SR), as well as encapsulation details, to 16 support Service Function Chaining (SFC) in an efficient manner while 17 maintaining separation of the service and transport planes as 18 originally intended by the SFC architecture. 20 Combining these technologies allows SR to be used for steering 21 packets between Service Function Forwarders (SFF) along a given 22 Service Function Path (SFP) while NSH has the responsibility for 23 maintaining the integrity of the service plane, the SFC instance 24 context, and any associated metadata. 26 The integration described in this document demonstrates that NSH and 27 SR can work jointly and complement each other leaving the network 28 operator with the flexibility to use whichever transport technology 29 makes sense in specific areas of their network infrastructure, and 30 still maintain an end-to-end service plane using NSH. 32 Status of This Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at https://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 This Internet-Draft will expire on December 10, 2021. 49 Copyright Notice 51 Copyright (c) 2021 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (https://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Table of Contents 66 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 67 1.1. SFC Overview and Rationale . . . . . . . . . . . . . . . 2 68 1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4 69 2. SFC within Segment Routing Networks . . . . . . . . . . . . . 4 70 3. NSH-based SFC with SR-MPLS or SRv6 Transport Tunnel . . . . . 5 71 4. SR-based SFC with Integrated NSH Service Plane . . . . . . . 9 72 5. Packet Processing for SR-based SFC . . . . . . . . . . . . . 11 73 5.1. SR-based SFC (SR-MPLS) Packet Processing . . . . . . . . 11 74 5.2. SR-based SFC (SRv6) Packet Processing . . . . . . . . . . 11 75 6. Encapsulation . . . . . . . . . . . . . . . . . . . . . . . . 12 76 6.1. NSH using SR-MPLS Transport . . . . . . . . . . . . . . . 12 77 6.2. NSH using SRv6 Transport . . . . . . . . . . . . . . . . 12 78 7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 79 8. MTU Considerations . . . . . . . . . . . . . . . . . . . . . 14 80 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 81 9.1. Protocol Number for NSH . . . . . . . . . . . . . . . . . 14 82 9.2. SRv6 Endpoint Behavior for NSH . . . . . . . . . . . . . 14 83 10. Contributing Authors . . . . . . . . . . . . . . . . . . . . 14 84 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 85 11.1. Normative References . . . . . . . . . . . . . . . . . . 15 86 11.2. Informative References . . . . . . . . . . . . . . . . . 17 87 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 89 1. Introduction 91 1.1. SFC Overview and Rationale 93 The dynamic enforcement of a service-derived and adequate forwarding 94 policy for packets entering a network that supports advanced Service 95 Functions (SFs) has become a key challenge for network operators. 96 Particularly, cascading SFs at the so-called Third Generation 97 Partnership Project (3GPP) Gi interface (N6 interface in 5G 98 architecture) in the context of mobile network infrastructure, have 99 shown their limitations, such as the same redundant classification 100 features must be supported by many SFs to execute their function, 101 some SFs receive traffic that they are not supposed to process (e.g., 102 TCP proxies receiving UDP traffic), which inevitably affects their 103 dimensioning and performance, an increased design complexity related 104 to the properly ordered invocation of several SFs, etc. 106 In order to solve those problems and to decouple the services 107 topology from the underlying physical network while allowing for 108 simplified service delivery, Service Function Chaining (SFC) 109 techniques have been introduced [RFC7665]. 111 SFC techniques are meant to rationalize the service delivery logic 112 and master the companion complexity while optimizing service 113 activation time cycles for operators that need more agile service 114 delivery procedures to better accommodate ever-demanding customer 115 requirements. Indeed, SFC allows to dynamically create service 116 planes that can be used by specific traffic flows. Each service 117 plane is realized by invoking and chaining the relevant service 118 functions in the right sequence. [RFC7498] provides an overview of 119 the overall SFC problem space and [RFC7665] specifies an SFC data 120 plane architecture. The SFC architecture does not make assumptions 121 on how advanced features (e.g., load-balancing, loose or strict 122 service paths) could be enabled within a domain. Various deployment 123 options are made available to operators with the SFC architecture and 124 this approach is fundamental to accommodate various and heterogeneous 125 deployment contexts. 127 Many approaches can be considered for encoding the information 128 required for SFC purposes (e.g., communicate a service chain pointer, 129 encode a list of loose/explicit paths, or disseminate a service chain 130 identifier together with a set of context information). Likewise, 131 many approaches can also be considered for the channel to be used to 132 carry SFC-specific information (e.g., define a new header, re-use 133 existing packet header fields, or define an IPv6 extension header). 134 Among all these approaches, the IETF created a transport-independent 135 SFC encapsulation scheme: NSH. This design is pragmatic as it does 136 not require replicating the same specification effort as a function 137 of underlying transport encapsulation. Moreover, this design 138 approach encourages consistent SFC-based service delivery in networks 139 enabling distinct transport protocols in various network segments or 140 even between SFFs vs SF-SFF hops. 142 1.2. Requirements Language 144 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 145 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 146 "OPTIONAL" in this document are to be interpreted as described in 147 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, 148 as shown here. 150 2. SFC within Segment Routing Networks 152 As described in [RFC8402], SR leverages the source routing technique. 153 Concretely, a node steers a packet through an SR policy instantiated 154 as an ordered list of instructions called segments. While initially 155 designed for policy-based source routing, SR also finds its 156 application in supporting SFC 157 [I-D.ietf-spring-sr-service-programming]. 159 The two SR data plane encapsulations, namely SR-MPLS [RFC8660] and 160 SRv6 [RFC8754], can both encode an SF as a segment so that an SFC can 161 be specified as a segment list. Nevertheless, and as discussed in 162 [RFC7498], traffic steering is only a subset of the issues that 163 motivated the design of the SFC architecture. Further considerations 164 such as simplifying classification at intermediate SFs and allowing 165 for coordinated behaviors among SFs by means of supplying context 166 information (a.k.a. metadata) should be considered when designing an 167 SFC data plane solution. 169 While each scheme (i.e., NSH-based SFC and SR-based SFC) can work 170 independently, this document describes how the two can be used 171 together in concert and complement each other through two 172 representative application scenarios. Both application scenarios may 173 be supported using either SR-MPLS or SRv6: 175 o NSH-based SFC with SR-based transport plane: in this scenario SR- 176 MPLS or SRv6 provides the transport encapsulation between SFFs 177 while NSH is used to convey and trigger SFC policies. 179 o SR-based SFC with integrated NSH service plane: in this scenario 180 each service hop of the SFC is represented as a segment of the SR 181 segment-list. SR is thus responsible for steering traffic through 182 the necessary SFFs as part of the segment routing path while NSH 183 is responsible for maintaining the service plane and holding the 184 SFC instance context (including associated metadata). 186 It is of course possible to combine both of these two scenarios to 187 support specific deployment requirements and use cases. 189 A classifier MUST assign an NSH Service Path Identifier (SPI) per SR 190 policy so that different traffic flows that use the same NSH Service 191 Function Path (SFP) but different SR policy can coexist on the same 192 SFP without conflict during SFF processing. 194 3. NSH-based SFC with SR-MPLS or SRv6 Transport Tunnel 196 Because of the transport-independent nature of NSH-based service 197 function chains, it is expected that the NSH has broad applicability 198 across different network domains (e.g., access, core). By way of 199 illustration the various SFs involved in a service function chain may 200 be available in a single data center, or spread throughout multiple 201 locations (e.g., data centers, different POPs), depending upon the 202 network operator preference and/or availability of service resources. 203 Regardless of where the SFs are deployed it is necessary to provide 204 traffic steering through a set of SFFs, and when NSH and SR are 205 integrated, this is provided by SR-MPLS or SRv6. 207 The following three figures provide an example of an SFC established 208 flow F that has SF instances located in different data centers, DC1 209 and DC2. For the purpose of illustration, let the SFC's NSH SPI be 210 100 and the initial Service Index (SI) be 255. 212 Referring to Figure 1, packets of flow F in DC1 are classified into 213 an NSH-based SFC and encapsulated after classification as and forwarded to SFF1 215 (which is the first SFF hop for this service function chain). 217 After removing the outer transport encapsulation, SFF1 uses the SPI 218 and SI carried within the NSH encapsulation to determine that it 219 should forward the packet to SF1. SF1 applies its service, 220 decrements the SI by 1, and returns the packet to SFF1. SFF1 221 therefore has when the packet comes back from SF1. 222 SFF1 does a lookup on which results in and forwards the packet to DC1-GW1. 225 +--------------------------- DC1 ----------------------------+ 226 | +-----+ | 227 | | SF1 | | 228 | +--+--+ | 229 | | | 230 | | | 231 | +------------+ | +------------+ | 232 | | N(100,255) | | | F:Inner Pkt| | 233 | +------------+ | +------------+ | 234 | | F:Inner Pkt| | | N(100,254) | | 235 | +------------+ ^ | | +------------+ | 236 | (2) | | | (3) | 237 | | | v | 238 | (1) | (4) | 239 |+------------+ ----> +--+---+ ----> +---------+ | 240 || | NSH | | NSH | | | 241 || Classifier +------------+ SFF1 +--------------+ DC1-GW1 + | 242 || | | | | | | 243 |+------------+ +------+ +---------+ | 244 | | 245 | +------------+ +------------+ | 246 | | N(100,255) | | N(100,254) | | 247 | +------------+ +------------+ | 248 | | F:Inner Pkt| | F:Inner Pkt| | 249 | +------------+ +------------+ | 250 | | 251 +------------------------------------------------------------+ 253 Figure 1: SR for inter-DC SFC - Part 1 255 Referring now to Figure 2, DC1-GW1 performs a lookup using the 256 information conveyed in the NSH which results in . The SR encapsulation, which may be SR-MPLS or 258 SRv6, has the SR segment-list to forward the packet across the inter- 259 DC network to DC2. 261 +----------- Inter DC ----------------+ 262 | (5) | 263 +------+ ----> | +---------+ ----> +---------+ | 264 | | NSH | | | SR | | | 265 + SFF1 +----------|-+ DC1-GW1 +-------------+ DC2-GW1 + | 266 | | | | | | | | 267 +------+ | +---------+ +---------+ | 268 | | 269 | +------------+ | 270 | | S(DC2-GW1) | | 271 | +------------+ | 272 | | N(100,254) | | 273 | +------------+ | 274 | | F:Inner Pkt| | 275 | +------------+ | 276 +-------------------------------------+ 278 Figure 2: SR for inter-DC SFC - Part 2 280 When the packet arrives at DC2, as shown in Figure 3, the SR 281 encapsulation is removed and DC2-GW1 performs a lookup on the NSH 282 which results in next hop: SFF2. When SFF2 receives the packet, it 283 performs a lookup on and determines to forward 284 the packet to SF2. SF2 applies its service, decrements the SI by 1, 285 and returns the packet to SFF2. SFF2 therefore has when the packet comes back from SF2. SFF2 does a lookup on 287 which results in end of service function 288 chain. 290 +------------------------ DC2 ----------------------+ 291 | +-----+ | 292 | | SF2 | | 293 | +--+--+ | 294 | | | 295 | | | 296 | +------------+ | +------------+ | 297 | | N(100,254) | | | F:Inner Pkt| | 298 | +------------+ | +------------+ | 299 | | F:Inner Pkt| | | N(100,253) | | 300 | +------------+ ^ | | +------------+ | 301 | (7) | | | (8) | 302 | | | v | 303 | (6) | (9) | 304 |+----------+ ----> +--+---+ ----> | 305 || | NSH | | IP | 306 || DC2-GW1 +------------+ SFF2 | | 307 || | | | | 308 |+----------+ +------+ | 309 | | 310 | +------------+ +------------+ | 311 | | N(100,254) | | F:Inner Pkt| | 312 | +------------+ +------------+ | 313 | | F:Inner Pkt| | 314 | +------------+ | 315 +---------------------------------------------------+ 317 Figure 3: SR for inter-DC SFC - Part 3 319 The benefits of this scheme are listed hereafter: 321 o The network operator is able to take advantage of the transport- 322 independent nature of the NSH encapsulation, while the service is 323 provisioned end2end. 325 o The network operator is able to take advantage of the traffic 326 steering (traffic engineering) capability of SR where appropriate. 328 o Clear responsibility division and scope between NSH and SR. 330 Note that this scenario is applicable to any case where multiple 331 segments of a service function chain are distributed across multiple 332 domains or where traffic-engineered paths are necessary between SFFs 333 (strict forwarding paths for example). Further note that the above 334 example can also be implemented using end to end segment routing 335 between SFF1 and SFF2. (As such DC-GW1 and DC-GW2 are forwarding the 336 packets based on segment routing instructions and are not looking at 337 the NSH header for forwarding). 339 4. SR-based SFC with Integrated NSH Service Plane 341 In this scenario we assume that the SFs are NSH-aware and therefore 342 it should not be necessary to implement an SFC proxy to achieve SFC. 343 The operation relies upon SR-MPLS or SRv6 to perform SFF-SFF 344 transport and NSH to provide the service plane between SFs thereby 345 maintaining SFC context (e.g., the service plane path referenced by 346 the SPI) and any associated metadata. 348 When a service function chain is established, a packet associated 349 with that chain will first carry an NSH that will be used to maintain 350 the end-to-end service plane through use of the SFC context. The SFC 351 context is used by an SFF to determine the SR segment list for 352 forwarding the packet to the next-hop SFFs. The packet is then 353 encapsulated using the SR header and forwarded in the SR domain 354 following normal SR operations. 356 When a packet has to be forwarded to an SF attached to an SFF, the 357 SFF performs a lookup on the SID associated with the SF. In the case 358 of SR-MPLS this will be a prefix SID [RFC8402]. In the case of SRv6, 359 the behavior described within this document is assigned the name 360 END.NSH, and section 9.2 requests allocation of a code point by IANA. 361 The result of this lookup allows the SFF to retrieve the next hop 362 context between the SFF and SF (e.g., the destination MAC address in 363 case native Ethernet encapsulation is used between SFF and SF). In 364 addition the SFF strips the SR information from the packet, updates 365 the SR information, and saves it to a cache indexed by the NSH 366 Service Path Identifier (SPI) and the Service Index (SI) decremented 367 by 1. This saved SR information is used to encapsulate and forward 368 the packet(s) coming back from the SF. 370 The behavior of remembering the SR segment-list occurs at the end of 371 the regularly defined logic. The behavior of reattaching the 372 segment-list occurs before the SR process of forwarding the packet to 373 the next entry in the segment-list. Both behaviors are further 374 detailed in section 5. 376 When the SF receives the packet, it processes it as usual and sends 377 it back to the SFF. Once the SFF receives this packet, it extracts 378 the SR information using the NSH SPI and SI as the index into the 379 cache. The SFF then pushes the retrieved SR header on top of the NSH 380 header, and forwards the packet to the next segment in the segment- 381 list. 383 Figure 4 illustrates an example of this scenario. 385 +-----+ +-----+ 386 | SF1 | | SF2 | 387 +--+--+ +--+--+ 388 | | 389 | | 390 +-----------+ | +-----------+ +-----------+ | +-----------+ 391 |N(100,255) | | |F:Inner Pkt| |N(100,254) | | |F:Inner Pkt| 392 +-----------+ | +-----------+ +-----------+ | +-----------+ 393 |F:Inner Pkt| | |N(100,254) | |F:Inner Pkt| | |N(100,253) | 394 +-----------+ | +-----------+ +-----------+ | +-----------+ 395 (2) ^ | (3) | (5) ^ | (6) | 396 | | | | | | 397 | | v | | v 398 +------------+ (1)--> +-+----+ (4)--> +---+--+ (7)-->IP 399 | | NSHoSR | | NSHoSR | | 400 | Classifier +--------+ SFF1 +---------------------+ SFF2 | 401 | | | | | | 402 +------------+ +------+ +------+ 404 +------------+ +------------+ 405 | S(SF1) | | S(SF2) | 406 +------------+ +------------+ 407 | S(SFF2) | | N(100,254) | 408 +------------+ +------------+ 409 | S(SF2) | | F:Inner Pkt| 410 +------------+ +------------+ 411 | N(100,255) | 412 +------------+ 413 | F:Inner Pkt| 414 +------------+ 416 Figure 4: NSH over SR for SFC 418 The benefits of this scheme include: 420 o It is economically sound for SF vendors to only support one 421 unified SFC solution. The SF is unaware of the SR. 423 o It simplifies the SFF (i.e., the SR router) by nullifying the 424 needs for re-classification and SR proxy. 426 o SR is also used for forwarding purposes including between SFFs. 428 o It takes advantage of SR to eliminate the NSH forwarding state in 429 SFFs. This applies each time strict or loose SFPs are in use. 431 o It requires no interworking as would be the case if SR-MPLS based 432 SFC and NSH-based SFC were deployed as independent mechanisms in 433 different parts of the network. 435 5. Packet Processing for SR-based SFC 437 This section describes the End.NSH behavior (SRv6), Prefix SID 438 behavior (SR-MPLS) and NSH processing logic. 440 5.1. SR-based SFC (SR-MPLS) Packet Processing 442 When an SFF receives a packet destined to S and S is a local prefix 443 SID associated with an SF, the SFF strips the SR segment-list (label 444 stack) from the packet, updates the SR information, and saves it to a 445 cache indexed by the NSH Service Path Identifier (SPI) and the 446 Service Index (SI) decremented by 1. This saved SR information is 447 used to re-encapsulate and forward the packet(s) coming back from the 448 SF. 450 5.2. SR-based SFC (SRv6) Packet Processing 452 This section describes the End.NSH behavior and NSH processing logic 453 for SRv6. The pseudo code is shown below. 455 When N receives a packet destined to S and S is a local End.NSH SID, 456 the processing is the same as that specified by RFC 8754 section 457 4.3.1.1, up through line S.16. 459 After S.15, if S is a local End.NSH SID, then: 461 S15.1. Remove and store IPv6 and SRH headers in local cache indexed 462 by 464 S15.2. Submit the packet to the NSH FIB lookup and transmit to the 465 destination associated with 467 Note: The End.NSH behavior interrupts the normal SRH packet 468 processing as described in RFC8754 section 4.3.1.1, which does not 469 continue to S16 at this time. 471 When a packet is returned to the SFF from the SF, reattach the cached 472 IPv6 and SRH headers based on the from the NSH header. Then resume processing from [RFC8754] 474 section 4.3.1.1 with line S.16. 476 6. Encapsulation 478 6.1. NSH using SR-MPLS Transport 480 SR-MPLS instantiates Segment IDs (SIDs) as MPLS labels and therefore 481 the segment routing header is a stack of MPLS labels. 483 When carrying NSH within an SR-MPLS transport, the full encapsulation 484 headers are as illustrated in Figure 5. 486 +------------------+ 487 ~ MPLS-SR Labels ~ 488 +------------------+ 489 | NSH Base Hdr | 490 +------------------+ 491 | Service Path Hdr | 492 +------------------+ 493 ~ Metadata ~ 494 +------------------+ 496 Figure 5: NSH using SR-MPLS Transport 498 As described in [RFC8402], the IGP signaling extension for IGP-Prefix 499 segment includes a flag to indicate whether directly connected 500 neighbors of the node on which the prefix is attached should perform 501 the NEXT operation or the CONTINUE operation when processing the SID. 502 When NSH is carried beneath SR-MPLS it is necessary to terminate the 503 NSH-based SFC at the tail-end node of the SR-MPLS label stack. This 504 is the equivalent of MPLS Ultimate Hop Popping (UHP) and therefore 505 the prefix-SID associated with the tail-end of the SFC MUST be 506 advertised with the CONTINUE operation so that the penultimate hop 507 node does not pop the top label of the SR-MPLS label stack and 508 thereby expose NSH to the wrong SFF. This is realized by setting No- 509 PHP flag in Prefix-SID Sub-TLV [RFC8667], [RFC8665]. It is 510 RECOMMENDED that a specific prefix-SID be allocated at each node for 511 use by the SFC application for this purpose. 513 Alternatively, if NEXT operation is performed, then at the end of the 514 SR-MPLS path it is necessary to provide an indication to the tail-end 515 that NSH follows the SR-MPLS label stack as described by [RFC8596]. 517 6.2. NSH using SRv6 Transport 519 When carrying NSH within an SRv6 transport the full encapsulation is 520 as illustrated in Figure 6. 522 0 1 2 3 523 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 1 524 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 525 | Next Header | Hdr Ext Len | Routing Type | Segments Left | 526 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 527 | Last Entry | Flags | Tag | S 528 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ e 529 | | g 530 | Segment List[0] (128 bits IPv6 address) | m 531 | | e 532 | | n 533 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ t 534 | | 535 | | R 536 ~ ... ~ o 537 | | u 538 | | t 539 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ i 540 | | n 541 | Segment List[n] (128 bits IPv6 address) | g 542 | | 543 | | S 544 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ R 545 // // H 546 // Optional Type Length Value objects (variable) // 547 // // 548 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 549 |Ver|O|U| TTL | Length |U|U|U|U|MD Type| Next Protocol | 550 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ N 551 | Service Path Identifier | Service Index | S 552 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ H 553 | | 554 ~ Variable-Length Context Headers (opt.) ~ 555 | | 556 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 558 Figure 6: NSH using SRv6 Transport 560 Encapsulation of NSH following SRv6 is indicated by the IP protocol 561 number for NSH in the Next Header of the SRH. 563 7. Security Considerations 565 Generic SFC-related security considerations are discussed in 566 [RFC7665]. 568 NSH-specific security considerations are discussed in [RFC8300]. 570 Generic segment routing related security considerations are discussed 571 in section 7 of [RFC8754] and section 5 of [RFC8663]. 573 8. MTU Considerations 575 Aligned with Section 5 of [RFC8300] and Section 5.3 of [RFC8754], it 576 is RECOMMENDED for network operators to increase the underlying MTU 577 so that SR/NSH traffic is forwarded within an SR domain without 578 fragmentation. 580 9. IANA Considerations 582 9.1. Protocol Number for NSH 584 IANA is requested to assign a protocol number TBA1 for the NSH from the 585 "Assigned Internet Protocol Numbers" registry available at 586 https://www.iana.org/assignments/protocol-numbers/protocol-numbers.xhtml 588 +---------+---------+--------------+---------------+----------------+ 589 | Decimal | Keyword | Protocol | IPv6 | Reference | 590 | | | | Extension | | 591 | | | | Header | | 592 +---------+---------+--------------+---------------+----------------+ 593 | TBA1 | NSH | Network | N | [ThisDocument] | 594 | | | Service | | | 595 | | | Header | | | 596 +---------+---------+--------------+---------------+----------------+ 598 9.2. SRv6 Endpoint Behavior for NSH 600 This I-D requests IANA to allocate, within the "SRv6 Endpoint Behaviors" 601 sub-registry belonging to the top-level "Segment-routing with IPv6 data 602 plane (SRv6) Parameters" registry, the following allocations: 604 Value Description Reference 605 -------------------------------------------------------------- 606 TBA2 End.NSH - NSH Segment [This.ID] 608 10. Contributing Authors 609 The following co-authors, along with their respective affiliations at 610 the time of WG adoption, provided valuable inputs and text contributions 611 to this document. 613 Mohamed Boucadair 614 Orange 615 mohamed.boucadair@orange.com 617 Joel Halpern 618 Ericsson 619 joel.halpern@ericsson.com 621 Syed Hassan 622 Cisco System, inc. 623 shassan@cisco.com 625 Wim Henderickx 626 Nokia 627 wim.henderickx@nokia.com 629 Haoyu Song 630 Futurewei Technologies 631 haoyu.song@futurewei.com 633 11. References 635 11.1. Normative References 637 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 638 Requirement Levels", BCP 14, RFC 2119, 639 DOI 10.17487/RFC2119, March 1997, 640 . 642 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 643 Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, 644 January 2012, . 646 [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function 647 Chaining (SFC) Architecture", RFC 7665, 648 DOI 10.17487/RFC7665, October 2015, 649 . 651 [RFC8086] Yong, L., Ed., Crabbe, E., Xu, X., and T. Herbert, "GRE- 652 in-UDP Encapsulation", RFC 8086, DOI 10.17487/RFC8086, 653 March 2017, . 655 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 656 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 657 May 2017, . 659 [RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed., 660 "Network Service Header (NSH)", RFC 8300, 661 DOI 10.17487/RFC8300, January 2018, 662 . 664 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 665 Decraene, B., Litkowski, S., and R. Shakir, "Segment 666 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 667 July 2018, . 669 [RFC8596] Malis, A., Bryant, S., Halpern, J., and W. Henderickx, 670 "MPLS Transport Encapsulation for the Service Function 671 Chaining (SFC) Network Service Header (NSH)", RFC 8596, 672 DOI 10.17487/RFC8596, June 2019, 673 . 675 [RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S., 676 Decraene, B., Litkowski, S., and R. Shakir, "Segment 677 Routing with the MPLS Data Plane", RFC 8660, 678 DOI 10.17487/RFC8660, December 2019, 679 . 681 [RFC8663] Xu, X., Bryant, S., Farrel, A., Hassan, S., Henderickx, 682 W., and Z. Li, "MPLS Segment Routing over IP", RFC 8663, 683 DOI 10.17487/RFC8663, December 2019, 684 . 686 [RFC8665] Psenak, P., Ed., Previdi, S., Ed., Filsfils, C., Gredler, 687 H., Shakir, R., Henderickx, W., and J. Tantsura, "OSPF 688 Extensions for Segment Routing", RFC 8665, 689 DOI 10.17487/RFC8665, December 2019, 690 . 692 [RFC8667] Previdi, S., Ed., Ginsberg, L., Ed., Filsfils, C., 693 Bashandy, A., Gredler, H., and B. Decraene, "IS-IS 694 Extensions for Segment Routing", RFC 8667, 695 DOI 10.17487/RFC8667, December 2019, 696 . 698 [RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J., 699 Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header 700 (SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020, 701 . 703 11.2. Informative References 705 [I-D.ietf-spring-sr-service-programming] 706 Clad, F., Xu, X., Filsfils, C., daniel.bernier@bell.ca, 707 d., Li, C., Decraene, B., Ma, S., Yadlapalli, C., 708 Henderickx, W., and S. Salsano, "Service Programming with 709 Segment Routing", draft-ietf-spring-sr-service- 710 programming-03 (work in progress), September 2020. 712 [RFC7498] Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for 713 Service Function Chaining", RFC 7498, 714 DOI 10.17487/RFC7498, April 2015, 715 . 717 Authors' Addresses 719 James N Guichard (editor) 720 Futurewei Technologies 721 2330 Central Express Way 722 Santa Clara 723 USA 725 Email: james.n.guichard@futurewei.com 727 Jeff Tantsura (editor) 728 Apstra inc. 729 USA 731 Email: jefftant.ietf@gmail.com