idnits 2.17.1 draft-ietf-pce-binding-label-sid-06.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (February 9, 2021) is 1172 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 7525 (Obsoleted by RFC 9325) == Outdated reference: A later version (-14) exists of draft-ietf-pce-pcep-extension-for-pce-controller-10 == Outdated reference: A later version (-22) exists of draft-ietf-spring-segment-routing-policy-09 == Outdated reference: A later version (-23) exists of draft-ietf-pce-pcep-yang-15 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 PCE Working Group S. Sivabalan 3 Internet-Draft Ciena Corporation 4 Intended status: Standards Track C. Filsfils 5 Expires: August 13, 2021 Cisco Systems, Inc. 6 J. Tantsura 7 Apstra, Inc. 8 S. Previdi 9 C. Li 10 Huawei Technologies 11 February 9, 2021 13 Carrying Binding Label/Segment-ID in PCE-based Networks. 14 draft-ietf-pce-binding-label-sid-06 16 Abstract 18 In order to provide greater scalability, network opacity, and service 19 independence, Segment Routing (SR) utilizes a Binding Segment 20 Identifier (BSID). It is possible to associate a BSID to RSVP-TE 21 signaled Traffic Engineering Label Switching Path or binding Segment- 22 ID (SID) to SR Traffic Engineering path. Such a binding label/SID 23 can be used by an upstream node for steering traffic into the 24 appropriate TE path to enforce SR policies. This document proposes 25 an approach for reporting binding label/SID to Path Computation 26 Element (PCE) for supporting PCE-based Traffic Engineering policies. 28 Requirements Language 30 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 31 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 32 "OPTIONAL" in this document are to be interpreted as described in BCP 33 14 [RFC2119] [RFC8174] when, and only when, they appear in all 34 capitals, as shown here. 36 Status of This Memo 38 This Internet-Draft is submitted in full conformance with the 39 provisions of BCP 78 and BCP 79. 41 Internet-Drafts are working documents of the Internet Engineering 42 Task Force (IETF). Note that other groups may also distribute 43 working documents as Internet-Drafts. The list of current Internet- 44 Drafts is at https://datatracker.ietf.org/drafts/current/. 46 Internet-Drafts are draft documents valid for a maximum of six months 47 and may be updated, replaced, or obsoleted by other documents at any 48 time. It is inappropriate to use Internet-Drafts as reference 49 material or to cite them other than as "work in progress." 51 This Internet-Draft will expire on August 13, 2021. 53 Copyright Notice 55 Copyright (c) 2021 IETF Trust and the persons identified as the 56 document authors. All rights reserved. 58 This document is subject to BCP 78 and the IETF Trust's Legal 59 Provisions Relating to IETF Documents 60 (https://trustee.ietf.org/license-info) in effect on the date of 61 publication of this document. Please review these documents 62 carefully, as they describe your rights and restrictions with respect 63 to this document. Code Components extracted from this document must 64 include Simplified BSD License text as described in Section 4.e of 65 the Trust Legal Provisions and are provided without warranty as 66 described in the Simplified BSD License. 68 Table of Contents 70 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 71 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 72 3. Path Binding TLV . . . . . . . . . . . . . . . . . . . . . . 6 73 3.1. SRv6 Endpoint Behavior and SID Structure . . . . . . . . 7 74 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 8 75 5. Binding SID in SR-ERO . . . . . . . . . . . . . . . . . . . . 10 76 6. Binding SID in SRv6-ERO . . . . . . . . . . . . . . . . . . . 10 77 7. PCE Allocation of Binding SID . . . . . . . . . . . . . . . . 10 78 8. Implementation Status . . . . . . . . . . . . . . . . . . . . 12 79 8.1. Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 12 80 8.2. Cisco . . . . . . . . . . . . . . . . . . . . . . . . . . 13 81 9. Security Considerations . . . . . . . . . . . . . . . . . . . 13 82 10. Manageability Considerations . . . . . . . . . . . . . . . . 13 83 10.1. Control of Function and Policy . . . . . . . . . . . . . 13 84 10.2. Information and Data Models . . . . . . . . . . . . . . 14 85 10.3. Liveness Detection and Monitoring . . . . . . . . . . . 14 86 10.4. Verify Correct Operations . . . . . . . . . . . . . . . 14 87 10.5. Requirements On Other Protocols . . . . . . . . . . . . 14 88 10.6. Impact On Network Operations . . . . . . . . . . . . . . 14 89 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 90 11.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 14 91 11.1.1. TE-PATH-BINDING TLV . . . . . . . . . . . . . . . . 14 92 11.1.2. Binding SID Flags . . . . . . . . . . . . . . . . . 15 93 11.2. LSP Object . . . . . . . . . . . . . . . . . . . . . . . 15 94 11.3. PCEP Error Type and Value . . . . . . . . . . . . . . . 15 95 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 16 96 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 97 13.1. Normative References . . . . . . . . . . . . . . . . . . 16 98 13.2. Informative References . . . . . . . . . . . . . . . . . 18 99 Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 19 100 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 102 1. Introduction 104 A PCE can compute Traffic Engineering paths (TE paths) through a 105 network that are subject to various constraints. Currently, TE paths 106 are either set up using the RSVP-TE signaling protocol or Segment 107 Routing (SR). We refer to such paths as RSVP-TE paths and SR-TE 108 paths respectively in this document. 110 As per [RFC8402] SR allows a headend node to steer a packet flow 111 along any path. The headend node is said to steer a flow into an 112 Segment Routing Policy (SR Policy). Further, as per 113 [I-D.ietf-spring-segment-routing-policy], an SR Policy is a framework 114 that enables instantiation of an ordered list of segments on a node 115 for implementing a source routing policy with a specific intent for 116 traffic steering from that node. 118 As described in [RFC8402], Binding Segment Identifier (BSID) is bound 119 to an Segment Routed (SR) Policy, instantiation of which may involve 120 a list of SIDs. Any packets received with an active segment equal to 121 BSID are steered onto the bound SR Policy. A BSID may be either a 122 local (SR Local Block (SRLB)) or a global (SR Global Block (SRGB)) 123 SID. As per Section 6.4 of [I-D.ietf-spring-segment-routing-policy] 124 a BSID can also be associated with any type of interfaces or tunnel 125 to enable the use of a non-SR interface or tunnels as segments in a 126 SID-list. 128 [RFC5440] describes the Path Computation Element Protocol (PCEP) for 129 communication between a Path Computation Client (PCC) and a PCE or 130 between a pair of PCEs as per [RFC4655]. [RFC8231] specifies 131 extension to PCEP that allows a PCC to delegate its LSPs to a 132 stateful PCE. A stateful PCE can then update the state of LSPs 133 delegated to it. [RFC8281] specifies a mechanism allowing a PCE to 134 dynamically instantiate an LSP on a PCC by sending the path and 135 characteristics. The PCEP extension to setup and maintain SR-TE 136 paths is specified in [RFC8664]. 138 [RFC8664] provides a mechanism for a network controller (acting as a 139 PCE) to instantiate candidate paths for an SR Policy onto a head-end 140 node (acting as a PCC) using PCEP. For more information on the SR 141 Policy Architecture, see [I-D.ietf-spring-segment-routing-policy]. 143 Binding label/SID has local significance to the ingress node of the 144 corresponding TE path. When a stateful PCE is deployed for setting 145 up TE paths, it may be desirable to report the binding label or SID 146 to the stateful PCE for the purpose of enforcing end-to-end TE/SR 147 policy. A sample Data Center (DC) use-case is illustrated in the 148 following diagram. In the MPLS DC network, an SR LSP (without 149 traffic engineering) is established using a prefix SID advertised by 150 BGP (see [RFC8669]). In IP/MPLS WAN, an SR-TE LSP is setup using the 151 PCE. The list of SIDs of the SR-TE LSP is {A, B, C, D}. The gateway 152 node 1 (which is the PCC) allocates a binding SID X and reports it to 153 the PCE. In order for the access node to steer the traffic over the 154 SR-TE LSP, the PCE passes the SID stack {Y, X} where Y is the prefix 155 SID of the gateway node-1 to the access node. In the absence of the 156 binding SID X, the PCE should pass the SID stack {Y, A, B, C, D} to 157 the access node. This example also illustrates the additional 158 benefit of using the binding SID to reduce the number of SIDs imposed 159 on the access nodes with a limited forwarding capacity. 161 SID stack 162 {Y, X} +-----+ 163 _ _ _ _ _ _ _ _ _ _ _ _ _ _| PCE | 164 | +-----+ 165 | ^ 166 | | Binding 167 | .-----. | SID (X) .-----. 168 | ( ) | ( ) 169 V .--( )--. | .--( )--. 170 +------+ ( ) +-------+ ( ) +-------+ 171 |Access|_( MPLS DC Network )_|Gateway|_( IP/MPLS WAN )_|Gateway| 172 | Node | ( ==============> ) |Node-1 | ( ================> ) |Node-2 | 173 +------+ ( SR path ) +-------+ ( SR-TE path ) +-------+ 174 '--( )--' Prefix '--( )--' 175 ( ) SID of ( ) 176 '-----' Node-1 '-----' 177 is Y SIDs for SR-TE LSP: 178 {A, B, C, D} 180 Figure 1: A sample Use-case of Binding SID 182 A PCC could report the binding label/SID allocated by it to the 183 stateful PCE via Path Computation State Report (PCRpt) message. It 184 is also possible for a stateful PCE to request a PCC to allocate a 185 specific binding label/SID by sending a Path Computation Update 186 Request (PCUpd) message. If the PCC can successfully allocate the 187 specified binding value, it reports the binding value to the PCE. 189 Otherwise, the PCC sends an error message to the PCE indicating the 190 cause of the failure. A local policy or configuration at the PCC 191 SHOULD dictate if the binding label/SID needs to be assigned. 193 In this document, we introduce a new OPTIONAL TLV that a PCC can use 194 in order to report the binding label/SID associated with a TE LSP, or 195 a PCE to request a PCC to allocate a specific binding label/SID 196 value. This TLV is intended for TE LSPs established using RSVP-TE, 197 SR, or any other future method. Also, in the case of SR-TE LSPs, the 198 TLV can carry a binding MPLS label (for SR-TE path with MPLS data- 199 plane) or a binding IPv6 SID (e.g., IPv6 address for SR-TE paths with 200 IPv6 data-plane). Binding value means either MPLS label or SID 201 throughout this document. 203 Additionally, to support the PCE based central controller [RFC8283] 204 operation where the PCE would take responsibility for managing some 205 part of the MPLS label space for each of the routers that it 206 controls, the PCE could directly make the binding label/SID 207 allocation and inform the PCC. See Section 7 for details. 209 2. Terminology 211 The following terminologies are used in this document: 213 BSID: Binding Segment Identifier. 215 LER: Label Edge Router. 217 LSP: Label Switched Path. 219 LSR: Label Switching Router. 221 PCC: Path Computation Client. 223 PCE: Path Computation Element 225 PCEP: Path Computation Element Protocol. 227 RSVP-TE: Resource ReserVation Protocol-Traffic Engineering. 229 SID: Segment Identifier. 231 SR: Segment Routing. 233 SRGB: Segment Routing Global Block. 235 SRLB: Segment Routing Local Block. 237 TLV: Type, Length, and Value. 239 3. Path Binding TLV 241 The new optional TLV is called "TE-PATH-BINDING TLV" (whose format is 242 shown in the figure below) is defined to carry the binding label or 243 SID for a TE path. This TLV is associated with the LSP object 244 specified in ([RFC8231]). The type of this TLV is to be allocated by 245 IANA. 247 0 1 2 3 248 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 1 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 | Type | Length | 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 252 | BT | Flags | Reserved | 253 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 254 ~ Binding Value (variable length) ~ 255 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 257 Figure 2: TE-PATH-BINDING TLV 259 TE-PATH-BINDING TLV is a generic TLV such that it is able to carry 260 MPLS label binding as well as SRv6 Binding SID. It is formatted 261 according to the rules specified in [RFC5440]. 263 Binding Type (BT): A one-octet field identifies the type of binding 264 included in the TLV. This document specifies the following BT 265 values: 267 o BT = 0: The binding value is an MPLS label carried in the format 268 specified in [RFC5462] where only the label value is valid, and 269 other fields MUST be considered invalid. The Length MUST be set 270 to 7. 272 o BT = 1: Similar to the case where BT is 0 except that all the 273 fields on the MPLS label entry are set on transmission. However, 274 the receiver MAY choose to override TC, S, and TTL values 275 according its local policy. The Length MUST be set to 8. 277 o BT = 2: The binding value is an SRv6 SID with a format of a 16 278 octet IPv6 address, representing the binding SID for SRv6. The 279 Length MUST be set to 20. 281 o BT = 3: The binding value is a 24 octet field, defined in 282 Section 3.1, that contains the SRv6 SID as well as its Behavior 283 and Structure. The Length MUST be set to 28. 285 Flags: 1 octet of flags. Following flags are defined in the new 286 registry "SR Policy Binding SID Flags" as described in 287 Section 11.1.2: 289 0 1 2 3 4 5 6 7 290 +-+-+-+-+-+-+-+-+ 291 | |I|S| 292 +-+-+-+-+-+-+-+-+ 294 where: 296 o S-Flag: This flag encodes the "Specified-BSID-only" behavior. It 297 is used as described in Section 6.2.3 of 298 [I-D.ietf-spring-segment-routing-policy]. 300 o I-Flag: This flag encodes the "Drop Upon Invalid" behavior. It is 301 used as described in Section 8.2 of 302 [I-D.ietf-spring-segment-routing-policy]. 304 Reserved: MUST be set to 0 while sending and ignored on receipt. 306 Binding Value: A variable-length field, padded with trailing zeros to 307 a 4-octet boundary. For the BT as 0, the 20 bits represent the MPLS 308 label. For the BT as 1, the 32-bits represent the label stack entry 309 as per [RFC5462]. For the BT as 2, the 128-bits represent the SRv6 310 SID. For the BT as 3, the Binding Value contains SRv6 Endpoint 311 Behavior and SID Structure, defined in Section 3.1. 313 3.1. SRv6 Endpoint Behavior and SID Structure 315 Carried as the Binding Value in the TE-PATH-BINDING TLV when the BT 316 is set to 3. Applicable for SRv6 Binding SIDs 317 [I-D.ietf-spring-srv6-network-programming]. 319 0 1 2 3 320 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 1 321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 322 | SRv6 Binding SID (16 octets) | 323 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 324 | Reserved | Endpoint Behavior | 325 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 326 | LB Length | LN Length | Fun. Length | Arg. Length | 327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 329 Figure 4: SRv6 Endpoint Behavior and SID Structure 331 Reserved: 2 octets. MUST be set to 0 on transmit and ignored on 332 receipt. 334 Endpoint Behavior: 2 octets. The Endpoint Behavior code point for 335 this SRv6 SID as defined in section 9.2 of 336 [I-D.ietf-spring-srv6-network-programming]. When set with the value 337 0, the choice of behavior is considered unset. 339 LB Length: 1 octet. SRv6 SID Locator Block length in bits. 341 LN Length: 1 octet. SRv6 SID Locator Node length in bits. 343 Function Length: 1 octet. SRv6 SID Function length in bits. 345 Argument Length: 1 octet. SRv6 SID Arguments length in bits. 347 4. Operation 349 The binding value is allocated by the PCC and reported to a PCE via 350 PCRpt message. If a PCE does not recognize the TE-PATH-BINDING TLV, 351 it would ignore the TLV in accordance with ([RFC5440]). If a PCE 352 recognizes the TLV but does not support the TLV, it MUST send PCErr 353 with Error-Type = 2 (Capability not supported). 355 If a TE-PATH-BINDING TLV is absent in the PCRpt message, PCE MUST 356 assume that the corresponding LSP does not have any binding. If a 357 PCE recognizes an invalid binding value (e.g., label value from the 358 reserved label space when MPLS label binding is used), it MUST send 359 the PCErr message with Error-Type = 10 ("Reception of an invalid 360 object") and Error Value = 2 ("Bad label value") as specified in 361 [RFC8664]. 363 Multiple TE-PATH-BINDING TLVs are allowed to be present in the same 364 LSP object. This signifies the presence of multiple binding SIDs for 365 the given LSP. 367 For SRv6 BSIDs, it is RECOMMENDED to always explicitly specify the 368 SRv6 Endpoint Behavior and SID Structure in the TE-PATH-BINDING TLV 369 by setting the BT (Binding Type) to 3, instead of 2. The choice of 370 interpreting SRv6 Endpoint Behavior and SID Structure when none is 371 explicitly specified is left up to the implementation. 373 If a PCE requires a PCC to allocate a specific binding value, it may 374 do so by sending a PCUpd or PCInitiate message containing a TE-PATH- 375 BINDING TLV. If the value can be successfully allocated, the PCC 376 reports the binding value to the PCE. If the PCC considers the 377 binding value specified by the PCE invalid, it MUST send a PCErr 378 message with Error-Type = TBD2 ("Binding label/SID failure") and 379 Error Value = TBD3 ("Invalid SID"). If the binding value is valid, 380 but the PCC is unable to allocate the binding value, it MUST send a 381 PCErr message with Error-Type = TBD2 ("Binding label/SID failure") 382 and Error Value = TBD4 ("Unable to allocate the specified label/ 383 SID"). 385 If a PCC receives TE-PATH-BINDING TLV in any message other than PCUpd 386 or PCInitiate, it MUST close the corresponding PCEP session with the 387 reason "Reception of a malformed PCEP message" (according to 388 [RFC5440]). Similarly, if a PCE receives a TE-PATH-BINDING TLV in 389 any message other than a PCRpt or if the TE-PATH-BINDING TLV is 390 associated with any object other than LSP object, the PCE MUST close 391 the corresponding PCEP session with the reason "Reception of a 392 malformed PCEP message" (according to [RFC5440]). 394 If a PCC wishes to withdraw or modify a previously reported binding 395 value, it MUST send a PCRpt message without any TE-PATH-BINDING TLV 396 or with the TE-PATH-BINDING TLV containing the new binding value 397 respectively. 399 If a PCE wishes to modify a previously requested binding value, it 400 MUST send a PCUpd message with TE-PATH-BINDING TLV containing the new 401 binding value. The absence of TE-PATH-BINDING TLV in PCUpd message 402 means that the PCE does not specify a binding value in which case the 403 binding value allocation is governed by the PCC's local policy. 405 If a PCC receives a valid binding value from a PCE which is different 406 than the current binding value, it MUST try to allocate the new 407 value. If the new binding value is successfully allocated, the PCC 408 MUST report the new value to the PCE. Otherwise, it MUST send a 409 PCErr message with Error-Type = TBD2 ("Binding label/SID failure") 410 and Error Value = TBD4 ("Unable to allocate the specified label/ 411 SID"). 413 In some cases, a stateful PCE can request the PCC to allocate a 414 binding value. It may do so by sending a PCUpd message containing an 415 empty TE-PATH-BINDING TLV, i.e., no binding value is specified 416 (making the length field of the TLV as 4). A PCE can also request 417 PCC to allocate a binding value at the time of initiation by sending 418 a PCInitiate message with an empty TE-PATH-BINDING TLV. If the PCC 419 is unable to allocate a binding value, it MUST send a PCErr message 420 with Error-Type = TBD2 ("Binding label/SID failure") and Error-Value 421 = TBD5 ("Unable to allocate label/SID"). 423 5. Binding SID in SR-ERO 425 In PCEP messages, LSP route information is carried in the Explicit 426 Route Object (ERO), which consists of a sequence of subobjects. 427 [RFC8664] defines a new ERO subobject "SR-ERO subobject" capable of 428 carrying a SID as well as the identity of the node/adjacency (NAI) 429 represented by the SID. The NAI Type (NT) field indicates the type 430 and format of the NAI contained in the SR-ERO. In case of binding 431 SID, the NAI MUST NOT be included and NT MUST be set to zero. So as 432 per Section 5.2.1 of [RFC8664], for NT=0, the F bit is set to 1, the 433 S bit needs to be zero and the Length is 8. Further, the M bit is 434 set. If these conditions are not met, the entire ERO MUST be 435 considered invalid and a PCErr message is sent with Error-Type = 10 436 ("Reception of an invalid object") and Error-Value = 11 ("Malformed 437 object"). 439 6. Binding SID in SRv6-ERO 441 [RFC8664] defines a new ERO subobject "SRv6-ERO subobject" for SRv6 442 SID. The NAI MUST NOT be included and NT MUST be set to zero. So as 443 per Section 5.2.1 of [RFC8664], for NT=0, the F bit is set to 1, the 444 S bit needs to be zero and the Length is 24. If these conditions are 445 not met, the entire ERO is considered invalid and a PCErr message is 446 sent with Error-Type = 10 ("Reception of an invalid object") and 447 Error-Value = 11 ("Malformed object") (as per [RFC8664]). 449 7. PCE Allocation of Binding SID 451 Section 4 already includes the scenario where a PCE requires a PCC to 452 allocate a specified binding value by sending a PCUpd or PCInitiate 453 message containing a TE-PATH-BINDING TLV. This section specify an 454 OPTIONAL feature for the PCE to allocate the binding label on its own 455 accord in the case where the PCE also controls the label space of the 456 PCC and can make the label allocation on its own as described in 457 [RFC8283]. Note that the act of requesting a specific binding value 458 (Section 4) is different from the act of allocating a binding label/ 459 SID as described in this section. 461 [RFC8283] introduces the architecture for PCE as a central controller 462 as an extension of the architecture described in [RFC4655] and 463 assumes the continued use of PCEP as the protocol used between PCE 464 and PCC. [I-D.ietf-pce-pcep-extension-for-pce-controller] specifies 465 the procedures and PCEP extensions for using the PCE as the central 466 controller. 468 For an implementation that supports PCECC operations as per 469 [I-D.ietf-pce-pcep-extension-for-pce-controller], the binding label/ 470 SID MAY also be allocated by the PCE itself. Both peers need to 471 exchange the PCECC capability as described in 472 [I-D.ietf-pce-pcep-extension-for-pce-controller] before PCE could 473 allocate the binding label/SID on its own. 475 A new P flag in the LSP object [RFC8231] is introduced to indicate 476 the allocation needs to be made by the PCE: 478 o P (PCE-allocated binding label/SID - TBD6): If the bit is set to 479 1, it indicates that the PCC requests PCE to make allocations for 480 this LSP. The TLV in LSP object identifies what should be 481 allocated, such as Binding label/SID. A PCC would set this bit to 482 1 and include a TE-PATH-BINDING TLV in the LSP object to request 483 for allocation of Binding label/SID by the PCE in the PCEP 484 message. A PCE would also set this bit to 1 and include a TE- 485 PATH-BINDING TLV to indicate that the Binding label/SID is 486 allocated by PCE and encoded in the PCEP message towards PCC. 487 Further, a PCE would set this bit to 0 and include a TE-PATH- 488 BINDING TLV in the LSP object to indicate that the Binding label/ 489 SID should be allocated by the PCC as described in Section 4. 491 Note that, 493 o a PCE could allocate the binding label/SID on its own accord for a 494 PCE-initiated or delegated LSP, and inform the PCC in the 495 PCInitiate message or PCUpd message by setting P=1 and including 496 TE-PATH-BINDING TLV in the LSP object. 498 o to let the PCC allocates the binding label/SID, a PCE could set 499 P=0 and empty TE-PATH-BINDING TLV ( i.e., no binding value is 500 specified) in the LSP object in PCInitiate/PCUpd message. 502 o a PCC could request that the PCE allocate the binding label/SID by 503 setting P=1, D=1, and empty TE-PATH-BINDING TLV in PCRpt message. 504 The PCE would allocate it and respond to the PCC with PCUpd 505 message including the allocated binding label/SID in the TE-PATH- 506 BINDING TLV and P=1, D=1 in the LSP object. 508 o if both peers have not exchanged the PCECC capabilities as per 509 [I-D.ietf-pce-pcep-extension-for-pce-controller] and it receives 510 P=1 in the LSP object, it needs to act as per 511 [I-D.ietf-pce-pcep-extension-for-pce-controller]: 513 * Send a PCErr message with Error-Type=19 (Invalid Operation) and 514 Error-Value=TBD (Attempted PCECC operations when PCECC 515 capability was not advertised) 517 * Terminate the PCEP session 519 It is assumed that the label range to be used by a PCE is known and 520 set on both PCEP peers. The exact mechanism is out of scope of 521 [I-D.ietf-pce-pcep-extension-for-pce-controller] or this document. 522 Note that the specific BSID could be from the PCE-controlled or the 523 PCC-controlled label space. PCE would directly allocate the label 524 from the PCE-controlled label space using P=1 as described above, 525 whereas PCE would request for the allocation of a specific BSID from 526 the PCC-controlled label space with P=0 as described in Section 4. 528 8. Implementation Status 530 [Note to the RFC Editor - remove this section before publication, as 531 well as remove the reference to RFC 7942.] 533 This section records the status of known implementations of the 534 protocol defined by this specification at the time of posting of this 535 Internet-Draft, and is based on a proposal described in [RFC7942]. 536 The description of implementations in this section is intended to 537 assist the IETF in its decision processes in progressing drafts to 538 RFCs. Please note that the listing of any individual implementation 539 here does not imply endorsement by the IETF. Furthermore, no effort 540 has been spent to verify the information presented here that was 541 supplied by IETF contributors. This is not intended as, and must not 542 be construed to be, a catalog of available implementations or their 543 features. Readers are advised to note that other implementations may 544 exist. 546 According to [RFC7942], "this will allow reviewers and working groups 547 to assign due consideration to documents that have the benefit of 548 running code, which may serve as evidence of valuable experimentation 549 and feedback that have made the implemented protocols more mature. 550 It is up to the individual working groups to use this information as 551 they see fit". 553 8.1. Huawei 555 o Organization: Huawei 557 o Implementation: Huawei's Router and Controller 559 o Description: An experimental code-point is used and plan to 560 request early code-point allocation from IANA after WG adoption. 562 o Maturity Level: Production 564 o Coverage: Full 566 o Contact: chengli13@huawei.com 568 8.2. Cisco 570 o Organization: Cisco Systems 572 o Implementation: Head-end and controller. 574 o Description: An experimental code-point is currently used. 576 o Maturity Level: Production 578 o Coverage: Full 580 o Contact: mkoldych@cisco.com 582 9. Security Considerations 584 The security considerations described in [RFC5440], [RFC8231], 585 [RFC8281] and [RFC8664] are applicable to this specification. No 586 additional security measure is required. 588 As described [RFC8664], SR allows a network controller to instantiate 589 and control paths in the network. A rouge PCE can manipulate binding 590 SID allocations to move traffic around for some other LSPs that uses 591 BSID in its SR-ERO. 593 Thus, as per [RFC8231], it is RECOMMENDED that these PCEP extensions 594 only be activated on authenticated and encrypted sessions across PCEs 595 and PCCs belonging to the same administrative authority, using 596 Transport Layer Security (TLS) [RFC8253], as per the recommendations 597 and best current practices in BCP195 [RFC7525] (unless explicitly set 598 aside in [RFC8253]). 600 10. Manageability Considerations 602 All manageability requirements and considerations listed in 603 [RFC5440], [RFC8231], and [RFC8664] apply to PCEP protocol extensions 604 defined in this document. In addition, requirements and 605 considerations listed in this section apply. 607 10.1. Control of Function and Policy 609 A PCC implementation SHOULD allow the operator to configure the 610 policy based on which PCC needs to allocates the binding label/SID. 612 10.2. Information and Data Models 614 The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to 615 include policy configuration for binding label/SID allocation. 617 10.3. Liveness Detection and Monitoring 619 Mechanisms defined in this document do not imply any new liveness 620 detection and monitoring requirements in addition to those already 621 listed in [RFC5440]. 623 10.4. Verify Correct Operations 625 Mechanisms defined in this document do not imply any new operation 626 verification requirements in addition to those already listed in 627 [RFC5440], [RFC8231], and [RFC8664]. 629 10.5. Requirements On Other Protocols 631 Mechanisms defined in this document do not imply any new requirements 632 on other protocols. 634 10.6. Impact On Network Operations 636 Mechanisms defined in [RFC5440], [RFC8231], and [RFC8664] also apply 637 to PCEP extensions defined in this document. Further, the mechanism 638 described in this document can help the operator to request control 639 of the LSPs at a particular PCE. 641 11. IANA Considerations 643 11.1. PCEP TLV Type Indicators 645 This document defines a new PCEP TLV; IANA is requested to make the 646 following allocations from the "PCEP TLV Type Indicators" sub- 647 registry of the PCEP Numbers registry, as follows: 649 Value Name Reference 651 TBD1 TE-PATH-BINDING This document 653 11.1.1. TE-PATH-BINDING TLV 655 IANA is requested to create a sub-registry to manage the value of the 656 Binding Type field in the TE-PATH-BINDING TLV. 658 Value Description Reference 660 0 MPLS Label This document 661 1 MPLS Label Stack This document 662 Entry 663 2 SRv6 SID This document 664 3 SRv6 SID with This document 665 Behavior and 666 Structure 668 11.1.2. Binding SID Flags 670 IANA is requested to create a sub-registry to manage the value of the 671 Binding SID Flags field in the TE-PATH-BINDING-TLV. New values are 672 to be assigned by Standards Action [RFC8126]. Each bit should be 673 tracked with the following qualities: 675 o Bit number (count from 0 as the most significant bit) 677 o Flag Name 679 o Reference 681 Bit Description Reference 683 7 Specified-BSID-Only This document 684 Flag (S-Flag) 685 6 Drop Upon Invalid This document 686 Flag (I-Flag) 688 11.2. LSP Object 690 IANA is requested to allocate new code-point in the "LSP Object Flag 691 Field" sub-registry for the new P flag as follows: 693 Bit Description Reference 695 TBD6 PCE-allocated binding This document 696 label/SID 698 11.3. PCEP Error Type and Value 700 This document defines a new Error-type and Error-Values for the PCErr 701 message. IANA is requested to allocate new error-type and error- 702 values within the "PCEP-ERROR Object Error Types and Values" 703 subregistry of the PCEP Numbers registry, as follows: 705 Error-Type Meaning 706 ---------- ------- 707 TBD2 Binding label/SID failure: 709 Error-value = TBD3: Invalid SID 710 Error-value = TBD4: Unable to allocate 711 the specified 712 label/SID 713 Error-value = TBD5: Unable to allocate 714 label/SID 716 12. Acknowledgements 718 We like to thank Milos Fabian, Mrinmoy Das, and Andrew Stone for 719 their valuable comments. 721 13. References 723 13.1. Normative References 725 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 726 Requirement Levels", BCP 14, RFC 2119, 727 DOI 10.17487/RFC2119, March 1997, 728 . 730 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 731 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 732 DOI 10.17487/RFC5440, March 2009, 733 . 735 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 736 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 737 Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 738 2009, . 740 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 741 "Recommendations for Secure Use of Transport Layer 742 Security (TLS) and Datagram Transport Layer Security 743 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 744 2015, . 746 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 747 Code: The Implementation Status Section", BCP 205, 748 RFC 7942, DOI 10.17487/RFC7942, July 2016, 749 . 751 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 752 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 753 May 2017, . 755 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 756 Computation Element Communication Protocol (PCEP) 757 Extensions for Stateful PCE", RFC 8231, 758 DOI 10.17487/RFC8231, September 2017, 759 . 761 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 762 "PCEPS: Usage of TLS to Provide a Secure Transport for the 763 Path Computation Element Communication Protocol (PCEP)", 764 RFC 8253, DOI 10.17487/RFC8253, October 2017, 765 . 767 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 768 Computation Element Communication Protocol (PCEP) 769 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 770 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 771 . 773 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 774 Decraene, B., Litkowski, S., and R. Shakir, "Segment 775 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 776 July 2018, . 778 [RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 779 and J. Hardwick, "Path Computation Element Communication 780 Protocol (PCEP) Extensions for Segment Routing", RFC 8664, 781 DOI 10.17487/RFC8664, December 2019, 782 . 784 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 785 Writing an IANA Considerations Section in RFCs", BCP 26, 786 RFC 8126, DOI 10.17487/RFC8126, June 2017, 787 . 789 [I-D.ietf-spring-srv6-network-programming] 790 Filsfils, C., Camarillo, P., Leddy, J., Voyer, D., 791 Matsushima, S., and Z. Li, "SRv6 Network Programming", 792 draft-ietf-spring-srv6-network-programming-28 (work in 793 progress), December 2020. 795 [I-D.ietf-pce-pcep-extension-for-pce-controller] 796 Li, Z., Peng, S., Negi, M., Zhao, Q., and C. Zhou, "PCEP 797 Procedures and Protocol Extensions for Using PCE as a 798 Central Controller (PCECC) of LSPs", draft-ietf-pce-pcep- 799 extension-for-pce-controller-10 (work in progress), 800 January 2021. 802 13.2. Informative References 804 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 805 Element (PCE)-Based Architecture", RFC 4655, 806 DOI 10.17487/RFC4655, August 2006, 807 . 809 [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An 810 Architecture for Use of PCE and the PCE Communication 811 Protocol (PCEP) in a Network with Central Control", 812 RFC 8283, DOI 10.17487/RFC8283, December 2017, 813 . 815 [RFC8669] Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah, 816 A., and H. Gredler, "Segment Routing Prefix Segment 817 Identifier Extensions for BGP", RFC 8669, 818 DOI 10.17487/RFC8669, December 2019, 819 . 821 [I-D.ietf-spring-segment-routing-policy] 822 Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and 823 P. Mattes, "Segment Routing Policy Architecture", draft- 824 ietf-spring-segment-routing-policy-09 (work in progress), 825 November 2020. 827 [I-D.ietf-pce-pcep-yang] 828 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 829 YANG Data Model for Path Computation Element 830 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 831 yang-15 (work in progress), October 2020. 833 Appendix A. Contributor Addresses 835 Jonathan Hardwick 836 Metaswitch Networks 837 100 Church Street 838 Enfield, Middlesex 839 UK 841 EMail: Jonathan.Hardwick@metaswitch.com 843 Dhruv Dhody 844 Huawei Technologies 845 Divyashree Techno Park, Whitefield 846 Bangalore, Karnataka 560066 847 India 849 EMail: dhruv.ietf@gmail.com 851 Mahendra Singh Negi 852 RtBrick India 853 N-17L, Floor-1, 18th Cross Rd, HSR Layout Sector-3 854 Bangalore, Karnataka 560102 855 India 857 EMail: mahend.ietf@gmail.com 859 Mike Koldychev 860 Cisco Systems, Inc. 861 2000 Innovation Drive 862 Kanata, Ontario K2K 3E8 863 Canada 865 Email: mkoldych@cisco.com 867 Zafar Ali 868 Cisco Systems, Inc. 870 Email: zali@cisco.com 872 Authors' Addresses 874 Siva Sivabalan 875 Ciena Corporation 877 EMail: msiva282@gmail.com 878 Clarence Filsfils 879 Cisco Systems, Inc. 880 Pegasus Parc 881 De kleetlaan 6a, DIEGEM BRABANT 1831 882 BELGIUM 884 EMail: cfilsfil@cisco.com 886 Jeff Tantsura 887 Apstra, Inc. 889 EMail: jefftant.ietf@gmail.com 891 Stefano Previdi 892 Huawei Technologies 894 EMail: stefano@previdi.net 896 Cheng Li 897 Huawei Technologies 898 Huawei Campus, No. 156 Beiqing Rd. 899 Beijing 100095 900 China 902 EMail: c.l@huawei.com