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Qin 6 China Mobile 7 March 5, 2020 9 PCEP Extension for SR-MPLS Entropy Label Position 10 draft-peng-pce-entropy-label-position-03 12 Abstract 14 This document proposes a set of extensions for PCEP to configure the 15 entropy label position for SR-MPLS networks. 17 Status of This Memo 19 This Internet-Draft is submitted in full conformance with the 20 provisions of BCP 78 and BCP 79. 22 Internet-Drafts are working documents of the Internet Engineering 23 Task Force (IETF). Note that other groups may also distribute 24 working documents as Internet-Drafts. The list of current Internet- 25 Drafts is at https://datatracker.ietf.org/drafts/current/. 27 Internet-Drafts are draft documents valid for a maximum of six months 28 and may be updated, replaced, or obsoleted by other documents at any 29 time. It is inappropriate to use Internet-Drafts as reference 30 material or to cite them other than as "work in progress." 32 This Internet-Draft will expire on September 6, 2020. 34 Copyright Notice 36 Copyright (c) 2020 IETF Trust and the persons identified as the 37 document authors. All rights reserved. 39 This document is subject to BCP 78 and the IETF Trust's Legal 40 Provisions Relating to IETF Documents 41 (https://trustee.ietf.org/license-info) in effect on the date of 42 publication of this document. Please review these documents 43 carefully, as they describe your rights and restrictions with respect 44 to this document. Code Components extracted from this document must 45 include Simplified BSD License text as described in Section 4.e of 46 the Trust Legal Provisions and are provided without warranty as 47 described in the Simplified BSD License. 49 Table of Contents 51 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 52 2. Conventions used in this document . . . . . . . . . . . . . . 3 53 2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 54 2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3 55 3. Entropy Labels in SR-MPLS Scenario with PCE . . . . . . . . . 3 56 4. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . . . 4 57 4.1. The OPEN Object . . . . . . . . . . . . . . . . . . . . . 4 58 4.2. The LSP Object . . . . . . . . . . . . . . . . . . . . . 5 59 4.3. The ERO Object . . . . . . . . . . . . . . . . . . . . . 5 60 5. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 6 61 6. Security Considerations . . . . . . . . . . . . . . . . . . . 6 62 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 63 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 64 8.1. New SR PCE Capability Flag Registry . . . . . . . . . . . 6 65 8.2. New LSP Flag Registry . . . . . . . . . . . . . . . . . . 7 66 8.3. New SR-ERO Flag Registry . . . . . . . . . . . . . . . . 7 67 9. Normative References . . . . . . . . . . . . . . . . . . . . 7 68 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9 70 1. Introduction 72 [RFC5440] describes the Path Computation Element Protocol (PCEP) 73 which is used between a Path Computation Element (PCE) and a Path 74 Computation Client (PCC) (or other PCE) to enable computation of 75 Multi-protocol Label Switching (MPLS) for Traffic Engineering Label 76 Switched Path (TE LSP). PCEP Extensions for the Stateful PCE Model 77 [RFC8231] describes a set of extensions to PCEP to enable active 78 control of MPLS-TE and Generalized MPLS (GMPLS) tunnels. [RFC8281] 79 describes the setup and teardown of PCE-initiated LSPs under the 80 active stateful PCE model, without the need for local configuration 81 on the PCC, thus allowing for dynamic centralized control of a 82 network. 84 Segment Routing (SR) leverages the source routing paradigm. Segment 85 Routing can be instantiated on MPLS data plane which is referred to 86 as SR-MPLS [RFC8660]. SR-MPLS leverages the MPLS label stack to 87 construct the SR path. PCEP Extensions for Segment Routing [RFC8664] 88 specifies extensions to the PCEP that allow a stateful PCE to compute 89 and initiate TE paths, as well as a PCC to request a path subject to 90 certain constraint(s) and optimization criteria in SR networks. 92 Entropy label (EL) [RFC6790] is a technique used in the MPLS data 93 plane to improve load-balancing. Entropy Label Indicator (ELI) can 94 be immediately preceding an EL in the MPLS label stack. The idea 95 behind the EL is that the ingress router computes a hash based on 96 several fields from a given packet and places the result in an 97 additional label, named "entropy label". Then, this entropy label 98 can be used as part of the hash keys used by an LSR. Using the 99 entropy label as part of the hash keys reduces the need for deep 100 packet inspection in the LSR while keeping a good level of entropy in 101 the load-balancing. When the entropy label is used, the keys used in 102 the hashing functions are still a local configuration matter and an 103 LSR may use solely the entropy label or a combination of multiple 104 fields from the incoming packet. 106 [RFC8662] proposes to use entropy labels for SR-MPLS networks and 107 mutiple pairs SHOULD be inserted in the SR-MPLS label 108 stack. The ingress node may decide the number and place of the ELI/ 109 ELs which need to be inserted into the label stack. But in some 110 cases, the the controller (e.g. PCE) could be used to perform the TE 111 path computation as well as the Entropy Label Position (ELP) which is 112 useful for inter-domain scenarios. This document proposes a set of 113 extensions for PCEP to configure the ELP information for SR-MPLS 114 networks. 116 2. Conventions used in this document 118 2.1. Terminology 120 The terminology is defined as [RFC5440], [RFC6790], [RFC8664] and 121 [RFC8662]. 123 2.2. Requirements Language 125 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 126 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 127 "OPTIONAL" in this document are to be interpreted as described in BCP 128 14 [RFC2119] [RFC8174] when, and only when, they appear in all 129 capitals, as shown here. 131 3. Entropy Labels in SR-MPLS Scenario with PCE 133 [RFC8662] proposes to use entropy labels for SR-MPLS networks. The 134 Entropy Readable Label Depth (ERLD) is defined as the number of 135 labels which means that the router will perform load-balancing using 136 the ELI/EL. An appropriate algorithm should consider the following 137 criteria: 139 o a limited number of pairs SHOULD be inserted in the SR- 140 MPLS label stack; 142 o the inserted positions SHOULD be whithin the ERLD of a maximize 143 number of transit LSRs; 145 o a minimum number of pairs SHOULD be inserted while 146 satisfying the above criteria. 148 As the Figure 1 shown, in SR-MPLS inter-domain scenario, the ingress 149 node of the first domain could not get the ERLD information of other 150 nodes of other domains. The PCE MUST perform the computation of the 151 end-to-end path as well as the the Entropy Label Position (ELP) 152 including the number and the place of the ELI/ELs. The PCEs has the 153 capability to get the ERLD information of all nodes in inter-domain 154 scenarios. 156 +-----+ +-----+ +-----+ 157 |PCE-1| |PCE-2| |PCE-3| 158 +--+--+ +--+--+ +--+--+ 159 | | | 160 .........+.......... .........+.......... .........+........... 161 . . . . . . 162 .+---+ +---+ . . +---+ +---+ . .+---+ +----+ . 163 .| A |-------| B |------ | C |------| X |-------| Y |------| Z | . 164 .+---+ +---+ . . +---+ +---+ . .+---+ +----+ . 165 . SR-AS 1 . . SR-AS 2 . . SR-AS 3 . 166 .................... .................... ..................... 168 Figure 1: Entropy Labels in SR-MPLS Inter-Domain Scenario 170 4. PCEP Extensions 172 4.1. The OPEN Object 174 As defined in [RFC8664], PCEP speakers use SR PCE Capability sub-TLV 175 to exchange information about their SR capability when PST=1 in the 176 PST List of the PATH-SETUP-TYPE-CAPABILITY TLV carried in Open 177 object. This document defined a new flag (E-flag) for SR PCE 178 Capability sub-TLV as shown in Figure 2. 180 0 1 2 3 181 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 1 182 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 183 | Type=TBD11 | Length=4 | 184 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 185 | Reserved | Flags |E|N|X| MSD | 186 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 188 Figure 2: E-flag in SR-PCE-CAPABILITY sub-TLV 190 E (ELP Configuration is supported) : A PCE sets this flag bit to 1 191 carried in Open message to indicate that it supports the computation 192 of SR path with ELP information. A PCC sets this flag to 1 to 193 indicate that it supports the capability of inserting multiple ELI/EL 194 pairs and and supports the results of SR path with ELP from PCE. 196 4.2. The LSP Object 198 The LSP Object is defined in Section 7.3 of [RFC8231]. This document 199 defiend a new flag (E-flag) for the LSP Object as Figure 3 shown: 201 0 1 2 3 202 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 1 203 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 204 | PLSP-ID | Flag|E|C| O |A|R|S|D| 205 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 206 // TLVs // 207 | | 208 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 210 Figure 3: E-flag in LSP Object 212 E (Request for ELP Configuration) : If the bit is set to 1, it 213 indicates that the PCC requests PCE to compute the SR path with ELP 214 information. A PCE would also set this bit to 1 to indicate that the 215 ELP information is included by PCE and encoded in the PCRep, PCUpd or 216 PCInitiate message. 218 4.3. The ERO Object 220 SR-ERO subobject is used for SR-TE path which consists of one or more 221 SIDs as defined in [RFC8664]. This document defiend a new flag 222 (E-flag) for the SR-ERO subobject as Figure 4 shown: 224 0 1 2 3 225 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 1 226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 227 |L| Type=36 | Length | NT | Flags |E|F|S|C|M| 228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 229 | SID (optional) | 230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 231 // NAI (variable, optional) // 232 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 234 Figure 4: E-flag in SR-ERO subobject 236 E (ELP Configuration) : If this flag is set, it means that the 237 position after this SR-ERO subobject is the position to insert , otherwise it cannot insert after this segment. 240 5. Operations 242 The SR path is initiated by PCE or PCC with PCReq, PCInitiated or 243 PCUpd messages and the E bit is set to 1 in LSP object to request the 244 ELP configuration. The SR-TE path being recieved by PCC with SR-ERO 245 segment list, for example, , especially S3 246 and S6 with E-flag set. It indicates that two pairs MUST 247 be inserted into the label stack of the SR-TE forwarding entry, 248 repectively after the label for S3 and label for S6. With EL 249 information, the label stack for SR-MPLS would be . 252 6. Security Considerations 254 TBA 256 7. Acknowledgements 258 TBA 260 8. IANA Considerations 262 8.1. New SR PCE Capability Flag Registry 264 SR PCE Capability TLV is defined in [RFC8664], and the registry to 265 manage the Flag field of the SR PCE Capability TLV is requested in 266 [RFC8664]. IANA is requested to make allocations from the registry, 267 as follows: 269 +---------+--------------------------------------+------------------+ 270 | Value | Name | Reference | 271 +---------+--------------------------------------+------------------+ 272 | TBD11 | ELP Configuration is supported (E) | [this document] | 273 +---------+--------------------------------------+------------------+ 275 Table 1 277 8.2. New LSP Flag Registry 279 [RFC8231] defines the LSP object; per that RFC, IANA created a 280 registry to manage the value of the LSP object's Flag field. IANA is 281 requested to make allocations from the registry, as follows: 283 +---------+-------------------------------------+------------------+ 284 | Value | Name | Reference | 285 +---------+-------------------------------------+------------------+ 286 | TBD | Request for ELP Configuration (E) | [this document] | 287 +---------+-------------------------------------+------------------+ 289 Table 2 291 8.3. New SR-ERO Flag Registry 293 SR-ERO subobject is defined in [RFC8664], and the registry to manage 294 the Flag field of SR-ERO is requested in [RFC8664]. IANA is 295 requested to make allocations from the registry, as follows: 297 +---------+-------------------------+------------------+ 298 | Value | Name | Reference | 299 +---------+-------------------------+------------------+ 300 | 36 | ELP Configuration (E) | [this document] | 301 +---------+-------------------------+------------------+ 303 Table 3 305 9. Normative References 307 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 308 Requirement Levels", BCP 14, RFC 2119, 309 DOI 10.17487/RFC2119, March 1997, 310 . 312 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation 313 Element (PCE) Communication Protocol (PCEP)", RFC 5440, 314 DOI 10.17487/RFC5440, March 2009, 315 . 317 [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and 318 L. Yong, "The Use of Entropy Labels in MPLS Forwarding", 319 RFC 6790, DOI 10.17487/RFC6790, November 2012, 320 . 322 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 323 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 324 May 2017, . 326 [RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path 327 Computation Element Communication Protocol (PCEP) 328 Extensions for Stateful PCE", RFC 8231, 329 DOI 10.17487/RFC8231, September 2017, 330 . 332 [RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path 333 Computation Element Communication Protocol (PCEP) 334 Extensions for PCE-Initiated LSP Setup in a Stateful PCE 335 Model", RFC 8281, DOI 10.17487/RFC8281, December 2017, 336 . 338 [RFC8623] Palle, U., Dhody, D., Tanaka, Y., and V. Beeram, "Stateful 339 Path Computation Element (PCE) Protocol Extensions for 340 Usage with Point-to-Multipoint TE Label Switched Paths 341 (LSPs)", RFC 8623, DOI 10.17487/RFC8623, June 2019, 342 . 344 [RFC8660] Bashandy, A., Ed., Filsfils, C., Ed., Previdi, S., 345 Decraene, B., Litkowski, S., and R. Shakir, "Segment 346 Routing with the MPLS Data Plane", RFC 8660, 347 DOI 10.17487/RFC8660, December 2019, 348 . 350 [RFC8662] Kini, S., Kompella, K., Sivabalan, S., Litkowski, S., 351 Shakir, R., and J. Tantsura, "Entropy Label for Source 352 Packet Routing in Networking (SPRING) Tunnels", RFC 8662, 353 DOI 10.17487/RFC8662, December 2019, 354 . 356 [RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., 357 and J. Hardwick, "Path Computation Element Communication 358 Protocol (PCEP) Extensions for Segment Routing", RFC 8664, 359 DOI 10.17487/RFC8664, December 2019, 360 . 362 Authors' Addresses 364 Shaofu Peng 365 ZTE Corporation 366 No.50 Software Avenue 367 Nanjing, Jiangsu 210012 368 China 370 Email: peng.shaofu@zte.com.cn 372 Quan Xiong 373 ZTE Corporation 374 No.6 Huashi Park Rd 375 Wuhan, Hubei 430223 376 China 378 Email: xiong.quan@zte.com.cn 380 Fengwei Qin 381 China Mobile 382 Beijing 383 China 385 Email: qinfengwei@chinamobile.com