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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references to lower-maturity documents in RFCs) ** Obsolete normative reference: RFC 7525 (Obsoleted by RFC 9325) == Outdated reference: A later version (-14) exists of draft-ietf-pce-pcep-extension-for-pce-controller-10 == Outdated reference: A later version (-22) exists of draft-ietf-spring-segment-routing-policy-09 == Outdated reference: A later version (-23) exists of draft-ietf-pce-pcep-yang-15 == Outdated reference: A later version (-25) exists of draft-ietf-pce-segment-routing-ipv6-08 Summary: 1 error (**), 0 flaws (~~), 5 warnings (==), 1 comment (--).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: October 16, 2021 Cisco Systems, Inc. 6 J. Tantsura 7 Juniper Networks 8 S. Previdi 9 C. Li 10 Huawei Technologies 11 April 14, 2021 13 Carrying Binding Label/Segment Identifier in PCE-based Networks. 14 draft-ietf-pce-binding-label-sid-08 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 an RSVP-TE 21 signaled Traffic Engineering Label Switching Path or an SR Traffic 22 Engineering path. The BSID can be used by an upstream node for 23 steering traffic into the appropriate TE path to enforce SR policies. 24 This document specifies the binding value as an MPLS label or Segment 25 Identifier. It further specify an approach for reporting binding 26 label/SID by a Path Computation Client (PCC) to the Path Computation 27 Element (PCE) to support PCE-based Traffic Engineering policies. 29 Status of This Memo 31 This Internet-Draft is submitted in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF). Note that other groups may also distribute 36 working documents as Internet-Drafts. The list of current Internet- 37 Drafts is at https://datatracker.ietf.org/drafts/current/. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 This Internet-Draft will expire on October 16, 2021. 46 Copyright Notice 48 Copyright (c) 2021 IETF Trust and the persons identified as the 49 document authors. All rights reserved. 51 This document is subject to BCP 78 and the IETF Trust's Legal 52 Provisions Relating to IETF Documents 53 (https://trustee.ietf.org/license-info) in effect on the date of 54 publication of this document. Please review these documents 55 carefully, as they describe your rights and restrictions with respect 56 to this document. Code Components extracted from this document must 57 include Simplified BSD License text as described in Section 4.e of 58 the Trust Legal Provisions and are provided without warranty as 59 described in the Simplified BSD License. 61 Table of Contents 63 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 64 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5 65 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 66 4. Path Binding TLV . . . . . . . . . . . . . . . . . . . . . . 6 67 4.1. SRv6 Endpoint Behavior and SID Structure . . . . . . . . 7 68 5. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 8 69 6. Binding SID in SR-ERO . . . . . . . . . . . . . . . . . . . . 10 70 7. Binding SID in SRv6-ERO . . . . . . . . . . . . . . . . . . . 11 71 8. PCE Allocation of Binding label/SID . . . . . . . . . . . . . 11 72 9. Implementation Status . . . . . . . . . . . . . . . . . . . . 13 73 9.1. Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 13 74 9.2. Cisco . . . . . . . . . . . . . . . . . . . . . . . . . . 13 75 10. Security Considerations . . . . . . . . . . . . . . . . . . . 14 76 11. Manageability Considerations . . . . . . . . . . . . . . . . 14 77 11.1. Control of Function and Policy . . . . . . . . . . . . . 14 78 11.2. Information and Data Models . . . . . . . . . . . . . . 14 79 11.3. Liveness Detection and Monitoring . . . . . . . . . . . 14 80 11.4. Verify Correct Operations . . . . . . . . . . . . . . . 15 81 11.5. Requirements On Other Protocols . . . . . . . . . . . . 15 82 11.6. Impact On Network Operations . . . . . . . . . . . . . . 15 83 12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 84 12.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 15 85 12.1.1. TE-PATH-BINDING TLV . . . . . . . . . . . . . . . . 15 86 12.2. LSP Object . . . . . . . . . . . . . . . . . . . . . . . 16 87 12.3. PCEP Error Type and Value . . . . . . . . . . . . . . . 16 88 13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 89 14. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 90 14.1. Normative References . . . . . . . . . . . . . . . . . . 17 91 14.2. Informative References . . . . . . . . . . . . . . . . . 19 92 Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 20 93 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 95 1. Introduction 97 A Path Computation Element (PCE) can compute Traffic Engineering 98 paths (TE paths) through a network where those paths are subject to 99 various constraints. Currently, TE paths are either set up using the 100 RSVP-TE signaling protocol or Segment Routing (SR). We refer to such 101 paths as RSVP-TE paths and SR-TE paths respectively in this document. 103 As per [RFC8402] SR allows a headend node to steer a packet flow 104 along any path. The headend node is said to steer a flow into an 105 Segment Routing Policy (SR Policy). Further, as per 106 [I-D.ietf-spring-segment-routing-policy], an SR Policy is a framework 107 that enables instantiation of an ordered list of segments on a node 108 for implementing a source routing policy with a specific intent for 109 traffic steering from that node. 111 As described in [RFC8402], a Binding Segment Identifier (BSID) is 112 bound to a Segment Routed (SR) Policy, instantiation of which may 113 involve a list of SIDs. Any packets received with an active segment 114 equal to a BSID are steered onto the bound SR Policy. A BSID may be 115 either a local (SR Local Block (SRLB)) or a global (SR Global Block 116 (SRGB)) SID. As per Section 6.4 of 117 [I-D.ietf-spring-segment-routing-policy] a BSID can also be 118 associated with any type of interfaces or tunnel to enable the use of 119 a non-SR interface or tunnel as a segment in a SID-list. In this 120 document, binding label/SID is used to generalize the allocation of 121 binding value for both SR and non-SR paths. 123 [RFC5440] describes the Path Computation Element Protocol (PCEP) for 124 communication between a Path Computation Client (PCC) and a PCE or 125 between a pair of PCEs as per [RFC4655]. [RFC8231] specifies 126 extensions to PCEP that allow a PCC to delegate its Label Switched 127 Paths (LSPs) to a stateful PCE. A stateful PCE can then update the 128 state of LSPs delegated to it. [RFC8281] specifies a mechanism 129 allowing a PCE to dynamically instantiate an LSP on a PCC by sending 130 the path and characteristics. 132 [RFC8664] provides a mechanism for a network controller (acting as a 133 PCE) to instantiate SR-TE paths (candidate paths) for an SR Policy 134 onto a head-end node (acting as a PCC) using PCEP. For more 135 information on the SR Policy Architecture, see 136 [I-D.ietf-spring-segment-routing-policy]. 138 A binding label/SID has local significance to the ingress node of the 139 corresponding TE path. When a stateful PCE is deployed for setting 140 up TE paths, it may be desirable for PCC to report the binding label/ 141 SID to the stateful PCE for the purpose of enforcing end-to-end TE/SR 142 policy. A sample Data Center (DC) use-case is illustrated in the 143 Figure 1. In the MPLS DC network, an SR LSP (without traffic 144 engineering) is established using a prefix SID advertised by BGP (see 145 [RFC8669]). In the IP/MPLS WAN, an SR-TE LSP is set up using the 146 PCE. The list of SIDs of the SR-TE LSP is {A, B, C, D}. The gateway 147 node 1 (which is the PCC) allocates a binding SID X and reports it to 148 the PCE. In order for the access node to steer the traffic over the 149 SR-TE LSP, the PCE passes the SID stack {Y, X} where Y is the prefix 150 SID of the gateway node-1 to the access node. In the absence of the 151 binding SID X, the PCE should pass the SID stack {Y, A, B, C, D} to 152 the access node. This example also illustrates the additional 153 benefit of using the binding SID to reduce the number of SIDs imposed 154 on the access nodes with a limited forwarding capacity. 156 SID stack 157 {Y, X} +-----+ 158 _ _ _ _ _ _ _ _ _ _ _ _ _ _| PCE | 159 | +-----+ 160 | ^ 161 | | Binding 162 | .-----. | SID (X) .-----. 163 | ( ) | ( ) 164 V .--( )--. | .--( )--. 165 +------+ ( ) +-------+ ( ) +-------+ 166 |Access|_( MPLS DC Network )_|Gateway|_( IP/MPLS WAN )_|Gateway| 167 | Node | ( ==============> ) |Node-1 | ( ================> ) |Node-2 | 168 +------+ ( SR path ) +-------+ ( SR-TE path ) +-------+ 169 '--( )--' Prefix '--( )--' 170 ( ) SID of ( ) 171 '-----' Node-1 '-----' 172 is Y SIDs for SR-TE LSP: 173 {A, B, C, D} 175 Figure 1: A sample Use-case of Binding SID 177 A PCC could report the binding label/SID allocated by it to the 178 stateful PCE via Path Computation State Report (PCRpt) message. It 179 is also possible for a stateful PCE to request a PCC to allocate a 180 specific binding label/SID by sending a Path Computation Update 181 Request (PCUpd) message. If the PCC can successfully allocate the 182 specified binding value, it reports the binding value to the PCE. 183 Otherwise, the PCC sends an error message to the PCE indicating the 184 cause of the failure. A local policy or configuration at the PCC 185 SHOULD dictate if the binding label/SID needs to be assigned. 187 In this document, we introduce a new OPTIONAL TLV that a PCC can use 188 in order to report the binding label/SID associated with a TE LSP, or 189 a PCE to request a PCC to allocate a specific binding label/SID 190 value. This TLV is intended for TE LSPs established using RSVP-TE, 191 SR, or any other future method. Also, in the case of SR-TE LSPs, the 192 TLV can carry a binding label (for SR-TE path with MPLS data-plane) 193 or a binding IPv6 SID (e.g., IPv6 address for SR-TE paths with IPv6 194 data-plane). Throughout this document, the term "binding value" 195 means either an MPLS label or SID. 197 Additionally, to support the PCE based central controller [RFC8283] 198 operation where the PCE would take responsibility for managing some 199 part of the MPLS label space for each of the routers that it 200 controls, the PCE could directly make the binding label/SID 201 allocation and inform the PCC. See Section 8 for details. 203 2. Requirements Language 205 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 206 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 207 "OPTIONAL" in this document are to be interpreted as described in BCP 208 14 [RFC2119] [RFC8174] when, and only when, they appear in all 209 capitals, as shown here. 211 3. Terminology 213 The following terminologies are used in this document: 215 BSID: Binding Segment Identifier. 217 LSP: Label Switched Path. 219 PCC: Path Computation Client. 221 PCE: Path Computation Element 223 PCEP: Path Computation Element Protocol. 225 RSVP-TE: Resource ReserVation Protocol-Traffic Engineering. 227 SID: Segment Identifier. 229 SR: Segment Routing. 231 TLV: Type, Length, and Value. 233 4. Path Binding TLV 235 The new optional TLV is called "TE-PATH-BINDING TLV" (whose format is 236 shown in the Figure 2) is defined to carry the binding label/SID for 237 a TE path. This TLV is associated with the LSP object specified in 238 [RFC8231]. This TLV can also be carried in the PCEP-ERROR object 239 [RFC5440] in case of error. Multiple instance of TE-PATH-BINDING 240 TLVs MAY be present in the LSP and PCEP-ERROR object. The type of 241 this TLV is 55 (early allocated by IANA). The length is variable. 243 0 1 2 3 244 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 1 245 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 246 | Type | Length | 247 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 248 | BT | Flags | Reserved | 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 ~ Binding Value (variable length) ~ 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 253 Figure 2: TE-PATH-BINDING TLV 255 TE-PATH-BINDING TLV is a generic TLV such that it is able to carry 256 binding label/SID (i.e. MPLS label or SRv6 SID). It is formatted 257 according to the rules specified in [RFC5440]. The value portion of 258 the TLV comprise of: 260 Binding Type (BT): A one-octet field identifies the type of binding 261 included in the TLV. This document specifies the following BT 262 values: 264 o BT = 0: The binding value is a 20-bit MPLS label value. The TLV 265 is padded to 4-bytes alignment. The Length MUST be set to 7 and 266 first 20 bits are used to encode the MPLS label value. 268 o BT = 1: The binding value is a 32-bit MPLS label stack entry as 269 per [RFC3032] with Label, TC [RFC5462], S, and TTL values encoded. 270 Note that the receiver MAY choose to override TC, S, and TTL 271 values according to its local policy. The Length MUST be set to 272 8. 274 o BT = 2: The binding value is an SRv6 SID with a format of a 16 275 octet IPv6 address, representing the binding SID for SRv6. The 276 Length MUST be set to 20. 278 o BT = 3: The binding value is a 24 octet field, defined in 279 Section 4.1, that contains the SRv6 SID as well as its Behavior 280 and Structure. The Length MUST be set to 28. 282 Section 12.1.1 defines the IANA registry used to maintain all these 283 binding types as well as any future ones. Note that, multiple TE- 284 PATH-BINDING TLVs with different Binding Types MAY be present for the 285 same LSP. 287 Flags: 1 octet of flags. Following flag is defined in the new 288 registry "TE-PATH-BINDING TLV Flag field" as described in 289 Section 12.1.1: 291 0 1 2 3 4 5 6 7 292 +-+-+-+-+-+-+-+-+ 293 |R| | 294 +-+-+-+-+-+-+-+-+ 296 Figure 3: Flags 298 where: 300 o R (Removal - 1 bit): When set, the requesting PCEP peer requires 301 the removal of the binding value for the LSP. When unset, the 302 PCEP peer indicates that the binding value is added or retained 303 for the LSP. This flag is used in the PCRpt and PCUpd messages. 304 It is ignored in other PCEP messages. 306 o The unassigned flags MUST be set to 0 while sending and ignored on 307 receipt. 309 Reserved: MUST be set to 0 while sending and ignored on receipt. 311 Binding Value: A variable-length field, padded with trailing zeros to 312 a 4-octet boundary. For the BT as 0, the 20 bits represent the MPLS 313 label. For the BT as 1, the 32-bits represent the MPLS label stack 314 entry as per [RFC3032]. For the BT as 2, the 128-bits represent the 315 SRv6 SID. For the BT as 3, the Binding Value also contains the SRv6 316 Endpoint Behavior and SID Structure, defined in Section 4.1. 318 4.1. SRv6 Endpoint Behavior and SID Structure 320 This section specify the format of the Binding Value in the TE-PATH- 321 BINDING TLV when the BT is set to 3 for the SRv6 Binding SIDs 322 [RFC8986], as shown in Figure 4. 324 0 1 2 3 325 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 1 326 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 327 | SRv6 Binding SID (16 octets) | 328 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 329 | Reserved | Endpoint Behavior | 330 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 331 | LB Length | LN Length | Fun. Length | Arg. Length | 332 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 334 Figure 4: SRv6 Endpoint Behavior and SID Structure 336 The Binding Value consist of: 338 o SRv6 Binding SID: 16 octets. The 128-bits IPv6 address, 339 representing the binding SID for SRv6. 341 o Reserved: 2 octets. It MUST be set to 0 on transmit and ignored 342 on receipt. 344 o Endpoint Behavior: 2 octets. The Endpoint Behavior code point for 345 this SRv6 SID as per the IANA subregistry called "SRv6 Endpoint 346 Behaviors", created by [RFC8986]. When the field is set with the 347 value 0, the endpoint behavior is considered unknown. 349 o The following fields are used to advertise the length of each 350 individual part of the SRv6 SID as defined in [RFC8986]: 352 * LB Length: 1 octet. SRv6 SID Locator Block length in bits. 354 * LN Length: 1 octet. SRv6 SID Locator Node length in bits. 356 * Function Length: 1 octet. SRv6 SID Function length in bits. 358 * Argument Length: 1 octet. SRv6 SID Arguments length in bits. 360 5. Operation 362 The binding value is allocated by the PCC and reported to a PCE via 363 PCRpt message. If a PCE does not recognize the TE-PATH-BINDING TLV, 364 it would ignore the TLV in accordance with [RFC5440]. If a PCE 365 recognizes the TLV but does not support the TLV, it MUST send PCErr 366 with Error-Type = 2 (Capability not supported). 368 Multiple TE-PATH-BINDING TLVs are allowed to be present in the same 369 LSP object. This signifies the presence of multiple binding SIDs for 370 the given LSP. In the case of multiple TE-PATH-BINDING TLVs, 371 existing instances of TE-PATH-BINDING TLVs MAY be included in the LSP 372 object. In case of an error condition, the whole message is rejected 373 and the resulting PCErr message MAY include the offending TE-PATH- 374 BINDING TLV in the PCEP-ERROR object. 376 If a PCE recognizes an invalid binding value (e.g., label value from 377 the reserved MPLS label space), it MUST send a PCErr message with 378 Error-Type = 10 ("Reception of an invalid object") and Error Value = 379 2 ("Bad label value") as specified in [RFC8664]. 381 For SRv6 BSIDs, it is RECOMMENDED to always explicitly specify the 382 SRv6 Endpoint Behavior and SID Structure in the TE-PATH-BINDING TLV 383 by setting the BT (Binding Type) to 3. This enables the sender to 384 have control of the SRv6 Endpoint Behavior and SID Structure. A 385 sender MAY choose to set the BT to 2, in which case the receiving 386 implementation chooses how to interpret the SRv6 Endpoint Behavior 387 and SID Structure according to local policy. 389 If a PCC wishes to withdraw a previously reported binding value, it 390 MUST send a PCRpt message with the specific TE-PATH-BINDING TLV with 391 R flag set to 1. If a PCC wishes to modify a previously reported 392 binding, it MUST withdraw the old binding value (with R flag set in 393 the old TE-PATH-BINDING TLV) and include a new TE-PATH-BINDING TLV 394 containing the new binding value. Note that, other instances of TE- 395 PATH-BINDING TLVs that are unchanged MAY also be included. 397 If a PCE requires a PCC to allocate a specific binding value(s), it 398 may do so by sending a PCUpd or PCInitiate message containing a TE- 399 PATH-BINDING TLV(s). If the value(s) can be successfully allocated, 400 the PCC reports the binding value(s) to the PCE. If the PCC 401 considers the binding value specified by the PCE invalid, it MUST 402 send a PCErr message with Error-Type = TBD2 ("Binding label/SID 403 failure") and Error Value = TBD3 ("Invalid SID"). If the binding 404 value is valid, but the PCC is unable to allocate the binding value, 405 it MUST send a PCErr message with Error-Type = TBD2 ("Binding label/ 406 SID failure") and Error Value = TBD4 ("Unable to allocate the 407 specified binding value"). Note that in case of an error, the PCC 408 rejects the PCUpd or PCInitiate message in its entirety and can carry 409 the offending TE-PATH-BINDING TLV in the PCEP-ERROR object. 411 If a PCE wishes to request withdrawal of a previously reported 412 binding value, it MUST send a PCUpd message with the specific TE- 413 PATH-BINDING TLV with R flag set to 1. If a PCE wishes to modify a 414 previously requested binding value, it MUST request withdrawal of the 415 old binding value (with R flag set in the old TE-PATH-BINDING TLV) 416 and include a new TE-PATH-BINDING TLV containing the new binding 417 value. 419 In some cases, a stateful PCE can request the PCC to allocate any 420 binding value. It instructs the PCC by sending a PCUpd message 421 containing an empty TE-PATH-BINDING TLV, i.e., no binding value is 422 specified (making the length field of the TLV as 4). A PCE can also 423 request PCC to allocate a binding value at the time of initiation by 424 sending a PCInitiate message with an empty TE-PATH-BINDING TLV. Only 425 one such instance of empty TE-PATH-BINDING TLV SHOULD be included in 426 the LSP object and others ignored on receipt. If the PCC is unable 427 to allocate a new binding value as per the specified BT, it MUST send 428 a PCErr message with Error-Type = TBD2 ("Binding label/SID failure") 429 and Error-Value = TBD5 ("Unable to allocate a new binding label/ 430 SID"). 432 As previously noted, if a message contains an invalid TE-PATH-BINDING 433 TLV that leads to an error condition, the whole message is rejected 434 including any other valid instances of TE-PATH-BINDING TLVs, if any. 435 The resulting error message MAY include the offending TE-PATH-BINDING 436 TLV in the PCEP-ERROR object. 438 If a PCC receives a TE-PATH-BINDING TLV in any message other than 439 PCUpd or PCInitiate, it MUST close the corresponding PCEP session 440 with the reason "Reception of a malformed PCEP message" (according to 441 [RFC5440]). Similarly, if a PCE receives a TE-PATH-BINDING TLV in 442 any message other than a PCRpt or if the TE-PATH-BINDING TLV is 443 associated with any object other than an LSP or PCEP-ERROR object, 444 the PCE MUST close the corresponding PCEP session with the reason 445 "Reception of a malformed PCEP message" (according to [RFC5440]). 447 If a TE-PATH-BINDING TLV is absent in the PCRpt message and no 448 binding values were reported before, the PCE MUST assume that the 449 corresponding LSP does not have any binding. Similarly, if TE-PATH- 450 BINDING TLV is absent in the PCUpd message and no binding values were 451 reported before, the PCC's local policy dictates how the binding 452 allocations are made for a given LSP. 454 6. Binding SID in SR-ERO 456 In PCEP messages, LSP route information is carried in the Explicit 457 Route Object (ERO), which consists of a sequence of subobjects. 458 [RFC8664] defines a new ERO subobject "SR-ERO subobject" capable of 459 carrying a SID as well as the identity of the node/adjacency (NAI) 460 represented by the SID. The NAI Type (NT) field indicates the type 461 and format of the NAI contained in the SR-ERO. In case of binding 462 SID, the NAI MUST NOT be included and NT MUST be set to zero. So as 463 per Section 5.2.1 of [RFC8664], for NT=0, the F bit is set to 1, the 464 S bit needs to be zero and the Length is 8. Further, the M bit is 465 set. If these conditions are not met, the entire ERO MUST be 466 considered invalid and a PCErr message is sent by the PCC with Error- 467 Type = 10 ("Reception of an invalid object") and Error-Value = 11 468 ("Malformed object"). 470 7. Binding SID in SRv6-ERO 472 [I-D.ietf-pce-segment-routing-ipv6] defines a new ERO subobject 473 "SRv6-ERO subobject" for an SRv6 SID. As stated in Section 6, in 474 case of binding SID, the NAI is not included and NT is set to zero 475 i.e., NT=0, the F bit is set to 1, the S bit needs to be zero and the 476 Length is 24 [I-D.ietf-pce-segment-routing-ipv6]. As per [RFC8664], 477 if these conditions are not met, the entire ERO is considered invalid 478 and a PCErr message is sent by the PCC with Error-Type = 10 479 ("Reception of an invalid object") and Error-Value = 11 ("Malformed 480 object"). 482 8. PCE Allocation of Binding label/SID 484 Section 5 already includes the scenario where a PCE requires a PCC to 485 allocate a specified binding value by sending a PCUpd or PCInitiate 486 message containing a TE-PATH-BINDING TLV. This section specifies an 487 OPTIONAL feature for the PCE to allocate the binding label/SID on its 488 own accord in the case where the PCE also controls the label space of 489 the PCC and can make the label allocation on its own as described in 490 [RFC8283]. Note that the act of requesting a specific binding value 491 (Section 5) is different from the act of allocating a binding label/ 492 SID as described in this section. 494 [RFC8283] introduces the architecture for PCE as a central controller 495 as an extension of the architecture described in [RFC4655] and 496 assumes the continued use of PCEP as the protocol used between PCE 497 and PCC. [I-D.ietf-pce-pcep-extension-for-pce-controller] specifies 498 the procedures and PCEP extensions for using the PCE as the central 499 controller. 501 For an implementation that supports PCECC operations as per 502 [I-D.ietf-pce-pcep-extension-for-pce-controller], the binding label/ 503 SID MAY also be allocated by the PCE itself. Both peers need to 504 exchange the PCECC capability as described in 505 [I-D.ietf-pce-pcep-extension-for-pce-controller] before the PCE can 506 allocate the binding label/SID on its own. 508 A new P flag in the LSP object [RFC8231] is introduced to indicate 509 the allocation needs to be made by the PCE: 511 o P (PCE-allocated binding label/SID): If the bit is set to 1, it 512 indicates that the PCC requests PCE to make allocations for this 513 LSP. The TE-PATH-BINDING TLV in the LSP object identifies that 514 the allocation is for binding label/SID. A PCC would set this bit 515 to 1 and include a TE-PATH-BINDING TLV in the LSP object to 516 request for allocation of binding label/SID by the PCE in the PCEP 517 message. A PCE would also set this bit to 1 and include a TE- 518 PATH-BINDING TLV to indicate that the binding label/SID is 519 allocated by PCE and encoded in the PCEP message towards PCC. 520 Further, a PCE would set this bit to 0 and include a TE-PATH- 521 BINDING TLV in the LSP object to indicate that the binding label/ 522 SID should be allocated by the PCC as described in Section 5. 524 Note that - 526 o A PCE could allocate the binding label/SID on its own accord for a 527 PCE-initiated or delegated LSP, and inform the PCC in the 528 PCInitiate message or PCUpd message by setting P=1 and including 529 TE-PATH-BINDING TLV in the LSP object. 531 o To let the PCC allocates the binding label/SID, a PCE could set 532 P=0 and include an empty TE-PATH-BINDING TLV ( i.e., no binding 533 value is specified) in the LSP object in PCInitiate/PCUpd message. 535 o A PCC could request that the PCE allocate the binding label/SID by 536 setting P=1, D=1, and including an empty TE-PATH-BINDING TLV in 537 PCRpt message. The PCE would allocate it and respond to the PCC 538 with PCUpd message including the allocated binding label/SID in 539 the TE-PATH-BINDING TLV and P=1, D=1 in the LSP object. 541 o If both peers have not exchanged the PCECC capabilities as per 542 [I-D.ietf-pce-pcep-extension-for-pce-controller] and a PCEP peer 543 receives P=1 in the LSP object, it needs to act as per 544 [I-D.ietf-pce-pcep-extension-for-pce-controller]: 546 * Send a PCErr message with Error-Type=19 (Invalid Operation) and 547 Error-Value=16 (Attempted PCECC operations when PCECC 548 capability was not advertised) 550 * Terminate the PCEP session 552 It is assumed that the label range to be used by a PCE is known and 553 set on both PCEP peers. The exact mechanism is out of scope of 554 [I-D.ietf-pce-pcep-extension-for-pce-controller] or this document. 555 Note that the specific BSID could be from the PCE-controlled or the 556 PCC-controlled label space. The PCE can directly allocate the label 557 from the PCE-controlled label space using P=1 as described above, 558 whereas the PCE can request for the allocation of a specific BSID 559 from the PCC-controlled label space with P=0 as described in 560 Section 5. 562 9. Implementation Status 564 [Note to the RFC Editor - remove this section before publication, as 565 well as remove the reference to RFC 7942.] 567 This section records the status of known implementations of the 568 protocol defined by this specification at the time of posting of this 569 Internet-Draft, and is based on a proposal described in [RFC7942]. 570 The description of implementations in this section is intended to 571 assist the IETF in its decision processes in progressing drafts to 572 RFCs. Please note that the listing of any individual implementation 573 here does not imply endorsement by the IETF. Furthermore, no effort 574 has been spent to verify the information presented here that was 575 supplied by IETF contributors. This is not intended as, and must not 576 be construed to be, a catalog of available implementations or their 577 features. Readers are advised to note that other implementations may 578 exist. 580 According to [RFC7942], "this will allow reviewers and working groups 581 to assign due consideration to documents that have the benefit of 582 running code, which may serve as evidence of valuable experimentation 583 and feedback that have made the implemented protocols more mature. 584 It is up to the individual working groups to use this information as 585 they see fit". 587 9.1. Huawei 589 o Organization: Huawei 591 o Implementation: Huawei's Router and Controller 593 o Description: An experimental code-point is used and plan to 594 request early code-point allocation from IANA after WG adoption. 596 o Maturity Level: Production 598 o Coverage: Full 600 o Contact: chengli13@huawei.com 602 9.2. Cisco 604 o Organization: Cisco Systems 606 o Implementation: Head-end and controller. 608 o Description: An experimental code-point is currently used. 610 o Maturity Level: Production 612 o Coverage: Full 614 o Contact: mkoldych@cisco.com 616 10. Security Considerations 618 The security considerations described in [RFC5440], [RFC8231], 619 [RFC8281] and [RFC8664] are applicable to this specification. No 620 additional security measure is required. 622 As described [RFC8664], SR allows a network controller to instantiate 623 and control paths in the network. A rogue PCE can manipulate binding 624 SID allocations to move traffic around for some other LSP that uses 625 BSID in its SR-ERO. 627 Thus, as per [RFC8231], it is RECOMMENDED that these PCEP extensions 628 only be activated on authenticated and encrypted sessions across PCEs 629 and PCCs belonging to the same administrative authority, using 630 Transport Layer Security (TLS) [RFC8253], as per the recommendations 631 and best current practices in BCP195 [RFC7525] (unless explicitly set 632 aside in [RFC8253]). 634 11. Manageability Considerations 636 All manageability requirements and considerations listed in 637 [RFC5440], [RFC8231], and [RFC8664] apply to PCEP protocol extensions 638 defined in this document. In addition, requirements and 639 considerations listed in this section apply. 641 11.1. Control of Function and Policy 643 A PCC implementation SHOULD allow the operator to configure the 644 policy based on which PCC needs to allocates the binding label/SID. 646 11.2. Information and Data Models 648 The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to 649 include policy configuration for binding label/SID allocation. 651 11.3. Liveness Detection and Monitoring 653 Mechanisms defined in this document do not imply any new liveness 654 detection and monitoring requirements in addition to those already 655 listed in [RFC5440]. 657 11.4. Verify Correct Operations 659 Mechanisms defined in this document do not imply any new operation 660 verification requirements in addition to those already listed in 661 [RFC5440], [RFC8231], and [RFC8664]. 663 11.5. Requirements On Other Protocols 665 Mechanisms defined in this document do not imply any new requirements 666 on other protocols. 668 11.6. Impact On Network Operations 670 Mechanisms defined in [RFC5440], [RFC8231], and [RFC8664] also apply 671 to PCEP extensions defined in this document. Further, the mechanism 672 described in this document can help the operator to request control 673 of the LSPs at a particular PCE. 675 12. IANA Considerations 677 IANA maintains the "Path Computation Element Protocol (PCEP) Numbers" 678 registry. This document requests IANA actions to allocate code 679 points for the protocol elements defined in this document. 681 12.1. PCEP TLV Type Indicators 683 This document defines a new PCEP TLV; IANA is requested to confirm 684 the following early allocations from the "PCEP TLV Type Indicators" 685 subregistry of the PCEP Numbers registry, as follows: 687 Value Description Reference 689 55 TE-PATH-BINDING This document 691 12.1.1. TE-PATH-BINDING TLV 693 IANA is requested to create a new subregistry "TE-PATH-BINDING TLV BT 694 field" to manage the value of the Binding Type field in the TE-PATH- 695 BINDING TLV. Initial values for the subregistry are given below. 696 New values are assigned by Standards Action [RFC8126]. 698 Value Description Reference 700 0 MPLS Label This document 701 1 MPLS Label Stack This document 702 Entry 703 2 SRv6 SID This document 704 3 SRv6 SID with This document 705 Behavior and 706 Structure 707 4-255 Unassigned This document 709 IANA is requested to create a new subregistry "TE-PATH-BINDING TLV 710 Flag field" to manage the Flag field in the TE-PATH-BINDING TLV. New 711 values are to be assigned by Standards Action [RFC8126]. Each bit 712 should be tracked with the following qualities: 714 o Bit number (count from 0 as the most significant bit) 716 o Description 718 o Reference 720 Bit Description Reference 722 0 R (Removal) This document 723 1-7 Unassigned This document 725 12.2. LSP Object 727 IANA is requested to confirm the early allocation for a new code- 728 point in the "LSP Object Flag Field" sub-registry for the new P flag 729 as follows: 731 Bit Description Reference 733 0 PCE-allocated binding This document 734 label/SID 736 12.3. PCEP Error Type and Value 738 This document defines a new Error-type and Error-Values for the PCErr 739 message. IANA is requested to allocate new error-type and error- 740 values within the "PCEP-ERROR Object Error Types and Values" 741 subregistry of the PCEP Numbers registry, as follows: 743 Error-Type Meaning Error-value Reference 745 TBD2 Binding label/SID This 746 failure document 747 TBD3: Invalid SID This 748 document 749 TBD4: Unable to allocate the This 750 specified binding value document 751 TBD5: Unable to allocate a This 752 new binding label/SID document 754 13. Acknowledgements 756 We like to thank Milos Fabian, Mrinmoy Das, Andrew Stone, Tom Petch, 757 Aijun Wang, Olivier Dugeon, and Adrian Farrel for their valuable 758 comments. 760 14. References 762 14.1. Normative References 764 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 765 Requirement Levels", BCP 14, RFC 2119, 766 DOI 10.17487/RFC2119, March 1997, 767 . 769 [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., 770 Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack 771 Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001, 772 . 774 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 775 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 776 DOI 10.17487/RFC5440, March 2009, 777 . 779 [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching 780 (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic 781 Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 782 2009, . 784 [RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre, 785 "Recommendations for Secure Use of Transport Layer 786 Security (TLS) and Datagram Transport Layer Security 787 (DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May 788 2015, . 790 [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running 791 Code: The Implementation Status Section", BCP 205, 792 RFC 7942, DOI 10.17487/RFC7942, July 2016, 793 . 795 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 796 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 797 May 2017, . 799 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 800 Computation Element Communication Protocol (PCEP) 801 Extensions for Stateful PCE", RFC 8231, 802 DOI 10.17487/RFC8231, September 2017, 803 . 805 [RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody, 806 "PCEPS: Usage of TLS to Provide a Secure Transport for the 807 Path Computation Element Communication Protocol (PCEP)", 808 RFC 8253, DOI 10.17487/RFC8253, October 2017, 809 . 811 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 812 Computation Element Communication Protocol (PCEP) 813 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 814 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 815 . 817 [RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L., 818 Decraene, B., Litkowski, S., and R. Shakir, "Segment 819 Routing Architecture", RFC 8402, DOI 10.17487/RFC8402, 820 July 2018, . 822 [RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 823 and J. Hardwick, "Path Computation Element Communication 824 Protocol (PCEP) Extensions for Segment Routing", RFC 8664, 825 DOI 10.17487/RFC8664, December 2019, 826 . 828 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 829 Writing an IANA Considerations Section in RFCs", BCP 26, 830 RFC 8126, DOI 10.17487/RFC8126, June 2017, 831 . 833 [RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer, 834 D., Matsushima, S., and Z. Li, "Segment Routing over IPv6 835 (SRv6) Network Programming", RFC 8986, 836 DOI 10.17487/RFC8986, February 2021, 837 . 839 [I-D.ietf-pce-pcep-extension-for-pce-controller] 840 Li, Z., Peng, S., Negi, M., Zhao, Q., and C. Zhou, "PCEP 841 Procedures and Protocol Extensions for Using PCE as a 842 Central Controller (PCECC) of LSPs", draft-ietf-pce-pcep- 843 extension-for-pce-controller-10 (work in progress), 844 January 2021. 846 14.2. Informative References 848 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation 849 Element (PCE)-Based Architecture", RFC 4655, 850 DOI 10.17487/RFC4655, August 2006, 851 . 853 [RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An 854 Architecture for Use of PCE and the PCE Communication 855 Protocol (PCEP) in a Network with Central Control", 856 RFC 8283, DOI 10.17487/RFC8283, December 2017, 857 . 859 [RFC8669] Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah, 860 A., and H. Gredler, "Segment Routing Prefix Segment 861 Identifier Extensions for BGP", RFC 8669, 862 DOI 10.17487/RFC8669, December 2019, 863 . 865 [I-D.ietf-spring-segment-routing-policy] 866 Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and 867 P. Mattes, "Segment Routing Policy Architecture", draft- 868 ietf-spring-segment-routing-policy-09 (work in progress), 869 November 2020. 871 [I-D.ietf-pce-pcep-yang] 872 Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A 873 YANG Data Model for Path Computation Element 874 Communications Protocol (PCEP)", draft-ietf-pce-pcep- 875 yang-15 (work in progress), October 2020. 877 [I-D.ietf-pce-segment-routing-ipv6] 878 Li, C., Negi, M., Sivabalan, S., Koldychev, M., 879 Kaladharan, P., and Y. Zhu, "PCEP Extensions for Segment 880 Routing leveraging the IPv6 data plane", draft-ietf-pce- 881 segment-routing-ipv6-08 (work in progress), November 2020. 883 Appendix A. Contributor Addresses 885 Jonathan Hardwick 886 Metaswitch Networks 887 33 Genotin Road 888 Enfield 889 United Kingdom 891 EMail: Jonathan.Hardwick@metaswitch.com 893 Dhruv Dhody 894 Huawei Technologies 895 Divyashree Techno Park, Whitefield 896 Bangalore, Karnataka 560066 897 India 899 EMail: dhruv.ietf@gmail.com 901 Mahendra Singh Negi 902 RtBrick India 903 N-17L, Floor-1, 18th Cross Rd, HSR Layout Sector-3 904 Bangalore, Karnataka 560102 905 India 907 EMail: mahend.ietf@gmail.com 909 Mike Koldychev 910 Cisco Systems, Inc. 911 2000 Innovation Drive 912 Kanata, Ontario K2K 3E8 913 Canada 915 Email: mkoldych@cisco.com 917 Zafar Ali 918 Cisco Systems, Inc. 920 Email: zali@cisco.com 922 Authors' Addresses 924 Siva Sivabalan 925 Ciena Corporation 927 EMail: msiva282@gmail.com 928 Clarence Filsfils 929 Cisco Systems, Inc. 930 Pegasus Parc 931 De kleetlaan 6a, DIEGEM BRABANT 1831 932 BELGIUM 934 EMail: cfilsfil@cisco.com 936 Jeff Tantsura 937 Juniper Networks 939 EMail: jefftant.ietf@gmail.com 941 Stefano Previdi 942 Huawei Technologies 944 EMail: stefano@previdi.net 946 Cheng Li 947 Huawei Technologies 948 Huawei Campus, No. 156 Beiqing Rd. 949 Beijing 100095 950 China 952 EMail: c.l@huawei.com