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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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-05) exists of draft-ietf-bess-vpls-multihoming-02 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 BESS Workgroup J. Rabadan, Ed. 3 Internet Draft Nokia 4 S. Mohanty, Ed. 5 Intended status: Standards Track A. Sajassi 6 Cisco 7 J. Drake 8 Juniper 9 K. Nagaraj 10 S. Sathappan 11 Nokia 13 Expires: June 23, 2019 December 20, 2018 15 Framework for EVPN Designated Forwarder Election Extensibility 16 draft-ietf-bess-evpn-df-election-framework-07 18 Abstract 20 An alternative to the Default Designated Forwarder (DF) selection 21 algorithm in Ethernet VPN (EVPN) networks is defined. The DF is the 22 Provider Edge (PE) router responsible for sending broadcast, unknown 23 unicast and multicast (BUM) traffic to multi-homed Customer Equipment 24 (CE) on a particular Ethernet Segment (ES) within a VLAN. In 25 addition, the capability to influence the DF election result for a 26 VLAN based on the state of the associated Attachment Circuit (AC) is 27 specified. 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), its areas, and its working groups. Note that 36 other groups may also distribute working documents as Internet- 37 Drafts. 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." 43 The list of current Internet-Drafts can be accessed at 44 http://www.ietf.org/ietf/1id-abstracts.txt 46 The list of Internet-Draft Shadow Directories can be accessed at 47 http://www.ietf.org/shadow.html 49 This Internet-Draft will expire on June 23, 2019. 51 Copyright Notice 53 Copyright (c) 2018 IETF Trust and the persons identified as the 54 document authors. All rights reserved. 56 This document is subject to BCP 78 and the IETF Trust's Legal 57 Provisions Relating to IETF Documents 58 (http://trustee.ietf.org/license-info) in effect on the date of 59 publication of this document. Please review these documents 60 carefully, as they describe your rights and restrictions with respect 61 to this document. Code Components extracted from this document must 62 include Simplified BSD License text as described in Section 4.e of 63 the Trust Legal Provisions and are provided without warranty as 64 described in the Simplified BSD License. 66 Table of Contents 68 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 69 1.1. Default Designated Forwarder (DF) Election in EVPN . . . . 3 70 1.2. Problem Statement . . . . . . . . . . . . . . . . . . . . . 5 71 1.2.1. Unfair Load-Balancing and Service Disruption . . . . . 6 72 1.2.2. Traffic Black-Holing on Individual AC Failures . . . . 7 73 1.3. The Need for Extending the Default DF Election in EVPN . . 9 74 2. Conventions and Terminology . . . . . . . . . . . . . . . . . . 10 75 3. Designated Forwarder Election Protocol and BGP Extensions . . . 11 76 3.1. The DF Election Finite State Machine (FSM) . . . . . . . . 12 77 3.2. The DF Election Extended Community . . . . . . . . . . . . 14 78 3.2.1. Backward Compatibility . . . . . . . . . . . . . . . . 17 79 3.3. Auto-Derivation of ES-Import Route Target . . . . . . . . . 17 80 4. The Highest Random Weight DF Election Algorithm . . . . . . . . 17 81 4.1. HRW and Consistent Hashing . . . . . . . . . . . . . . . . 18 82 4.2. HRW Algorithm for EVPN DF Election . . . . . . . . . . . . 18 83 5. The Attachment Circuit Influenced DF Election Capability . . . 20 84 5.1. AC-Influenced DF Election Capability For VLAN-Aware 85 Bundle Services . . . . . . . . . . . . . . . . . . . . . . 22 86 6. Solution Benefits . . . . . . . . . . . . . . . . . . . . . . . 23 87 7. Security Considerations . . . . . . . . . . . . . . . . . . . . 23 88 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 24 89 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 24 90 9.1. Normative References . . . . . . . . . . . . . . . . . . . 25 91 9.2. Informative References . . . . . . . . . . . . . . . . . . 25 92 10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 26 93 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 26 94 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27 96 1. Introduction 98 The Designated Forwarder (DF) in EVPN networks is the Provider Edge 99 (PE) router responsible for sending broadcast, unknown unicast and 100 multicast (BUM) traffic to a multi-homed Customer Equipment (CE) 101 device, on a given VLAN on a particular Ethernet Segment (ES). The DF 102 is selected out of a list of candidate PEs that advertise the same 103 Ethernet Segment Identifier (ESI) to the EVPN network. By default, 104 EVPN uses a DF Election algorithm referred to as "Service Carving" 105 and it is based on a modulus function (V mod N) that takes the number 106 of PEs in the ES (N) and the VLAN value (V) as input. This Default DF 107 Election algorithm has some inefficiencies that this document 108 addresses by defining a new DF Election algorithm and a capability to 109 influence the DF Election result for a VLAN, depending on the state 110 of the associated Attachment Circuit (AC). In order to avoid any 111 ambiguity with the identifier used in the DF Election Algorithm, this 112 document uses the term Ethernet Tag instead of VLAN. This document 113 also creates a registry with IANA, for future DF Election Algorithms 114 and Capabilities. It also presents a formal definition and 115 clarification of the DF Election Finite State Machine. 117 The procedures described in this document apply to [RFC7432] and 118 [RFC8214] EVPN networks. This document does not intend to update 119 [RFC7432] or [RFC8214] but intends to improve the behavior of the DF 120 Election on PEs that are upgraded to follow the described procedures. 122 1.1. Default Designated Forwarder (DF) Election in EVPN 124 [RFC7432] defines the Designated Forwarder (DF) as the EVPN PE 125 responsible for: 127 o Flooding Broadcast, Unknown unicast and Multicast traffic (BUM), on 128 a given Ethernet Tag on a particular Ethernet Segment (ES), to the 129 CE. This is valid for single-active and all-active EVPN 130 multi-homing. 132 o Sending unicast traffic on a given Ethernet Tag on a particular ES 133 to the CE. This is valid for single-active multi-homing. 135 Figure 1 illustrates an example that we will use to explain the 136 Designated Forwarder function. 138 +---------------+ 139 | IP/MPLS | 140 | CORE | 141 +----+ ES1 +----+ +----+ 142 | CE1|-----| | | |____ES2 143 +----+ | PE1| | PE2| \ 144 | | +----+ \+----+ 145 +----+ | | CE2| 146 | +----+ /+----+ 147 | | |____/ | 148 | | PE3| ES2 / 149 | +----+ / 150 | | / 151 +-------------+----+ / 152 | PE4|____/ES2 153 | | 154 +----+ 156 Figure 1 Multi-homing Network of EVPN 158 Figure 1 illustrates a case where there are two Ethernet Segments, 159 ES1 and ES2. PE1 is attached to CE1 via Ethernet Segment ES1 whereas 160 PE2, PE3 and PE4 are attached to CE2 via ES2 i.e. PE2, PE3 and PE4 161 form a redundancy group. Since CE2 is multi-homed to different PEs on 162 the same Ethernet Segment, it is necessary for PE2, PE3 and PE4 to 163 agree on a DF to satisfy the above mentioned requirements. 165 The effect of forwarding loops in a Layer-2 network is particularly 166 severe because of the broadcast nature of Ethernet traffic and the 167 lack of a Time-To-Live (TTL). Therefore it is very important that in 168 the case of a multi-homed CE only one of the PEs be used to send BUM 169 traffic to it. 171 One of the pre-requisites for this support is that participating PEs 172 must agree amongst themselves as to who would act as the Designated 173 Forwarder (DF). This needs to be achieved through a distributed 174 algorithm in which each participating PE independently and 175 unambiguously selects one of the participating PEs as the DF, and the 176 result should be consistent and unanimous. 178 The default algorithm for DF election defined by [RFC7432] at the 179 granularity of (ESI,EVI) is referred to as "service carving". In this 180 document, service carving and Default DF Election algorithm are used 181 interchangeably. With service carving, it is possible to elect 182 multiple DFs per Ethernet Segment (one per EVI) in order to perform 183 load-balancing of traffic destined to a given Segment. The objective 184 is that the load-balancing procedures should carve up the BD space 185 among the redundant PE nodes evenly, in such a way that every PE is 186 the DF for a distinct set of EVIs. 188 The DF Election algorithm as described in [RFC7432] (Section 8.5) is 189 based on a modulus operation. The PEs to which the ES (for which DF 190 election is to be carried out per EVI) is multi-homed form an ordered 191 (ordinal) list in ascending order of the PE IP address values. For 192 example, there are N PEs: PE0, PE1,... PEN-1 ranked as per increasing 193 IP addresses in the ordinal list; then for each VLAN with Ethernet 194 Tag V, configured on the Ethernet Segment ES1, PEx is the DF for VLAN 195 V on ES1 when x equals (V mod N). In the case of VLAN Bundle only the 196 lowest VLAN is used. In the case when the planned density is high 197 (meaning there are significant number of VLANs and the Ethernet Tags 198 are uniformly distributed), the thinking is that the DF Election will 199 be spread across the PEs hosting that Ethernet Segment and good load- 200 balancing can be achieved. 202 However, the described Default DF Election algorithm has some 203 undesirable properties and in some cases can be somewhat disruptive 204 and unfair. This document describes some of those issues and defines 205 a mechanism for dealing with them. These mechanisms do involve 206 changes to the Default DF Election algorithm, but they do not require 207 any changes to the EVPN Route exchange and have minimal changes in 208 the EVPN routes. 210 In addition, there is a need to extend the DF Election procedures so 211 that new algorithms and capabilities are possible. A single algorithm 212 (the Default DF Election algorithm) may not meet the requirements in 213 all the use-cases. 215 Note that while [RFC7432] elects a DF per , this document 216 elects a DF per . This means that unlike [RFC7432], where for 217 a VLAN-Aware Bundle service EVI there is only one DF for the EVI, 218 this document specifies that there will be multiple DFs, one for each 219 BD configured in that EVI. 221 1.2. Problem Statement 223 This section describes some potential issues with the Default DF 224 Election algorithm. 226 1.2.1. Unfair Load-Balancing and Service Disruption 228 There are three fundamental problems with the current Default DF 229 Election algorithm. 231 1- First, the algorithm will not perform well when the Ethernet Tag 232 follows a non-uniform distribution, for instance when the Ethernet 233 Tags are all even or all odd. In such a case let us assume that 234 the ES is multi-homed to two PEs; one of the PEs will be elected 235 as DF for all of the VLANs. This is very sub-optimal. It defeats 236 the purpose of service carving as the DFs are not really evenly 237 spread across. In fact, in this particular case, one of the PEs 238 does not get elected as DF at all, so it does not participate in 239 the DF responsibilities at all. Consider another example where, 240 referring to Figure 1, lets assume that PE2, PE3, PE4 are in 241 ascending order of the IP address; and each VLAN configured on ES2 242 is associated with an Ethernet Tag of the form (3x+1), where x is 243 an integer. This will result in PE3 always be selected as the DF. 245 2- Even in the case when the Ethernet Tag distribution is uniform the 246 instance of a PE being up or down results in re-computation ((v 247 mod N-1) or (v mod N+1) as is the case); the resulting modulus 248 value need not be uniformly distributed because it can be subject 249 to the primality of N-1 or N+1 as may be the case. 251 3- The third problem is one of disruption. Consider a case when the 252 same Ethernet Segment is multi-homed to a set of PEs. When the ES 253 is down in one of the PEs, say PE1, or PE1 itself reboots, or the 254 BGP process goes down or the connectivity between PE1 and an RR 255 goes down, the effective number of PEs in the system now becomes 256 N-1, and DFs are computed for all the VLANs that are configured on 257 that Ethernet Segment. In general, if the DF for a VLAN v happens 258 not to be PE1, but some other PE, say PE2, it is likely that some 259 other PE (different from PE1 and PE2) will become the new DF. This 260 is not desirable. Similarly when a new PE hosts the same Ethernet 261 Segment, the mapping again changes because of the modulus 262 operation. This results in needless churn. Again referring to 263 Figure 1, say v1, v2 and v3 are VLANs configured on ES2 with 264 associated Ethernet Tags of value 999, 1000 and 1001 respectively. 265 So PE1, PE2 and PE3 are the DFs for v1, v2 and v3 respectively. 266 Now when PE3 goes down, PE2 will become the DF for v1 and PE1 will 267 become the DF for v2. 269 One point to note is that the Default DF election algorithm assumes 270 that all the PEs who are multi-homed to the same Ethernet Segment 271 (and interested in the DF Election by exchanging EVPN routes) use an 272 Originating Router's IP Address of the same family. This does not 273 need to be the case as the EVPN address-family can be carried over an 274 IPv4 or IPv6 peering, and the PEs attached to the same ES may use an 275 address of either family. 277 Mathematically, a conventional hash function maps a key k to a number 278 i representing one of m hash buckets through a function h(k) i.e. 279 i=h(k). In the EVPN case, h is simply a modulo-m hash function viz. 280 h(v) = v mod N, where N is the number of PEs that are multi-homed to 281 the Ethernet Segment in discussion. It is well-known that for good 282 hash distribution using the modulus operation, the modulus N should 283 be a prime-number not too close to a power of 2 [CLRS2009]. When the 284 effective number of PEs changes from N to N-1 (or vice versa); all 285 the objects (VLAN V) will be remapped except those for which V mod N 286 and V mod (N-1) refer to the same PE in the previous and subsequent 287 ordinal rankings respectively. From a forwarding perspective, this is 288 a churn, as it results in re-programming the PE ports as either 289 blocking or non-blocking at the PEs where the DF state changes. 291 This document addresses this problem and furnishes a solution to this 292 undesirable behavior. 294 1.2.2. Traffic Black-Holing on Individual AC Failures 296 As discussed in section 2.1 the Default DF Election algorithm defined 297 by [RFC7432] takes into account only two variables in the modulus 298 function for a given ES: the existence of the PE's IP address on the 299 candidate list and the locally provisioned Ethernet Tags. 301 If the DF for an fails (due to physical link/node 302 failures) an ES route withdrawal will make the Non-DF (NDF) PEs re- 303 elect the DF for that and the service will be recovered. 305 However, the Default DF election procedure does not provide a 306 protection against "logical" failures or human errors that may occur 307 at service level on the DF, while the list of active PEs for a given 308 ES does not change. These failures may have an impact not only on the 309 local PE where the issue happens, but also on the rest of the PEs of 310 the ES. Some examples of such logical failures are listed below: 312 a) A given individual Attachment Circuit (AC) defined in an ES is 313 accidentally shutdown or even not provisioned yet (hence the 314 Attachment Circuit Status - ACS - is DOWN), while the ES is 315 operationally active (since the ES route is active). 317 b) A given MAC-VRF - with a defined ES - is shutdown or not 318 provisioned yet, while the ES is operationally active (since the 319 ES route is active). In this case, the ACS of all the ACs defined 320 in that MAC-VRF is considered to be DOWN. 322 Neither (a) nor (b) will trigger the DF re-election on the remote 323 multi-homed PEs for a given ES since the ACS is not taken into 324 account in the DF election procedures. While the ACS is used as a DF 325 election tie-breaker and trigger in VPLS multi-homing procedures 326 [VPLS-MH], there is no procedure defined in EVPN [RFC7432] to trigger 327 the DF re-election based on the ACS change on the DF. 329 Figure 2 illustrates the described issue with an example. 331 +---+ 332 |CE4| 333 +---+ 334 | 335 PE4 | 336 +-----+-----+ 337 +---------------| +-----+ |---------------+ 338 | | | BD-1| | | 339 | +-----------+ | 340 | | 341 | EVPN | 342 | | 343 | PE1 PE2 PE3 | 344 | (NDF) (DF) (NDF)| 345 +-----------+ +-----------+ +-----------+ 346 | | BD-1| | | | BD-1| | | | BD-1| | 347 | +-----+ |-------| +-----+ |-------| +-----+ | 348 +-----------+ +-----------+ +-----------+ 349 AC1\ ES12 /AC2 AC3\ ES23 /AC4 350 \ / \ / 351 \ / \ / 352 +----+ +----+ 353 |CE12| |CE23| 354 +----+ +----+ 356 Figure 2 Default DF Election and Traffic Black-Holing 358 BD-1 is defined in PE1, PE2, PE3 and PE4. CE12 is a multi-homed CE 359 connected to ES12 in PE1 and PE2. Similarly CE23 is multi-homed to 360 PE2 and PE3 using ES23. Both, CE12 and CE23, are connected to BD-1 361 through VLAN-based service interfaces: CE12-VID 1 (VLAN ID 1 on CE12) 362 is associated to AC1 and AC2 in BD-1, whereas CE23-VID 1 is 363 associated to AC3 and AC4 in BD-1. Assume that, although not 364 represented, there are other ACs defined on these ES mapped to 365 different BDs. 367 After executing the [RFC7432] Default DF election algorithm, PE2 368 turns out to be the DF for ES12 and ES23 in BD-1. The following 369 issues may arise: 371 a) If AC2 is accidentally shutdown or even not configured, CE12 372 traffic will be impacted. In case of all-active multi-homing, the 373 BUM traffic to CE12 will be "black-holed", whereas for single- 374 active multi-homing, all the traffic to/from CE12 will be 375 discarded. This is due to the fact that a logical failure in PE2's 376 AC2 may not trigger an ES route withdrawn for ES12 (since there 377 are still other ACs active on ES12) and therefore PE1 will not re- 378 run the DF election procedures. 380 b) If the Bridge Table for BD-1 is administratively shutdown or even 381 not configured yet on PE2, CE12 and CE23 will both be impacted: 382 BUM traffic to both CEs will be discarded in case of all-active 383 multi-homing and all traffic will be discarded to/from the CEs in 384 case of single-active multi-homing. This is due to the fact that 385 PE1 and PE3 will not re-run the DF election procedures and will 386 keep assuming PE2 is the DF. 388 Quoting [RFC7432], "when an Ethernet Tag is decommissioned on an 389 Ethernet Segment, then the PE MUST withdraw the Ethernet A-D per EVI 390 route(s) announced for the that are impacted by 391 the decommissioning", however, while this A-D per EVI route 392 withdrawal is used at the remote PEs performing aliasing or backup 393 procedures, it is not used to influence the DF election for the 394 affected EVIs. 396 This document adds an optional modification of the DF Election 397 procedure so that the ACS may be taken into account as a variable in 398 the DF election, and therefore EVPN can provide protection against 399 logical failures. 401 1.3. The Need for Extending the Default DF Election in EVPN 403 Section 2.2 describes some of the issues that exist in the Default DF 404 Election procedures. In order to address those issues, this document 405 introduces a new DF Election framework. This framework allows the PEs 406 to agree on a common DF election algorithm, as well as the 407 capabilities to enable during the DF Election procedure. Generally, 408 'DF election algorithm' refers to the algorithm by which a number of 409 input parameters are used to determine the DF PE, while 'DF election 410 capability' refers to an additional feature that can be used prior to 411 the invocation of the DF election algorithm, such as modifying the 412 inputs (or list of candidate PEs). 414 Within this framework, this document defines a new DF Election 415 algorithm and a new capability that can influence the DF Election 416 result: 418 o The new DF Election algorithm is referred to as "Highest Random 419 Weight" (HRW). The HRW procedures are described in section 4. 421 o The new DF Election capability is referred to as "AC-Influenced DF 422 Election" (AC-DF). The AC-DF procedures are described in section 5. 424 o HRW and AC-DF mechanisms are independent of each other. Therefore, 425 a PE MAY support either HRW or AC-DF independently or MAY support 426 both of them together. A PE MAY also support AC-DF capability along 427 with the Default DF election algorithm per [RFC7432]. 429 In addition, this document defines a way to indicate the support of 430 HRW and/or AC-DF along with the EVPN ES routes advertised for a given 431 ES. Refer to section 3.2 for more details. 433 2. Conventions and Terminology 435 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 436 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 437 "OPTIONAL" in this document are to be interpreted as described in BCP 438 14 [RFC2119] [RFC8174] when, and only when, they appear in all 439 capitals, as shown here. 441 o AC and ACS - Attachment Circuit and Attachment Circuit Status. An 442 AC has an Ethernet Tag associated to it. 444 o BUM - refers to the Broadcast, Unknown unicast and Multicast 445 traffic. 447 o DF, NDF and BDF - Designated Forwarder, Non-Designated Forwarder 448 and Backup Designated Forwarder 450 o Ethernet A-D per ES route - refers to [RFC7432] route type 1 or 451 Auto-Discovery per Ethernet Segment route. 453 o Ethernet A-D per EVI route - refers to [RFC7432] route type 1 or 454 Auto-Discovery per EVPN Instance route. 456 o ES and ESI - Ethernet Segment and Ethernet Segment Identifier. 458 o EVI - EVPN Instance. 460 o MAC-VRF - A Virtual Routing and Forwarding table for Media Access 461 Control (MAC) addresses on a PE. 463 o BD - Broadcast Domain. An EVI may be comprised of one (VLAN-Based 464 or VLAN Bundle services) or multiple (VLAN-Aware Bundle services) 465 Broadcast Domains. 467 o Bridge Table - An instantiation of a broadcast domain on a MAC-VRF. 469 o HRW - Highest Random Weight 471 o VID and CE-VID - VLAN Identifier and Customer Equipment VLAN 472 Identifier. 474 o Ethernet Tag - used to represent a Broadcast Domain that is 475 configured on a given ES for the purpose of DF election. Note that 476 any of the following may be used to represent a Broadcast Domain: 477 VIDs (including Q-in-Q tags), configured IDs, VNI (VXLAN Network 478 Identifiers), normalized VID, I-SIDs (Service Instance 479 Identifiers), etc., as long as the representation of the broadcast 480 domains is configured consistently across the multi-homed PEs 481 attached to that ES. The Ethernet Tag value MUST be different from 482 zero. 484 o Ethernet Tag ID - refers to the identifier used in the EVPN routes 485 defined in [RFC7432]. Its value may be the same as the Ethernet Tag 486 value (see Ethernet Tag definition) when advertising routes for 487 VLAN-aware Bundle services. Note that in case of VLAN-based or VLAN 488 Bundle services, the Ethernet Tag ID is zero. 490 o DF Election Procedure and DF Algorithm - The Designated Forwarder 491 Election Procedure or simply DF Election, refers to the process in 492 its entirety, including the discovery of the PEs in the ES, the 493 creation and maintenance of the PE candidate list and the selection 494 of a PE. The Designated Forwarder Algorithm is just a component of 495 the DF Election Procedure and strictly refers to the selection of a 496 PE for a given . 498 o TTL - Time To Live 500 This document also assumes familiarity with the terminology of 501 [RFC7432]. 503 3. Designated Forwarder Election Protocol and BGP Extensions 505 This section describes the BGP extensions required to support the new 506 DF Election procedures. In addition, since the EVPN specification 507 [RFC7432] does leave several questions open as to the precise final 508 state machine behavior of the DF election, section 3.1 describes 509 precisely the intended behavior. 511 3.1. The DF Election Finite State Machine (FSM) 513 Per [RFC7432], the FSM described in Figure 3 is executed per 514 in case of VLAN-based service or in case of VLAN Bundle on each participating PE. 517 Observe that currently the VLANs are derived from local configuration 518 and the FSM does not provide any protection against misconfiguration 519 where the same (EVI,ESI) combination has different set of VLANs on 520 different participating PEs or one of the PEs elects to consider 521 VLANs as VLAN Bundle and another as separate VLANs for election 522 purposes (service type mismatch). 524 The FSM is conceptual and any design or implementation MUST comply 525 with a behavior equivalent to the one outlined in this FSM. 527 VLAN_CHANGE 528 VLAN_CHANGE RCVD_ES 529 RCVD_ES LOST_ES 530 LOST_ES +----+ 531 +----+ | v 532 | | ++----++ 533 | +-+----+ ES_UP | DF | 534 +->+ INIT +---------------> WAIT | 535 ++-----+ +----+-+ 536 ^ | 537 +-----------+ | |DF_TIMER 538 | ANY STATE +-------+ VLAN_CHANGE | 539 +-----------+ ES_DOWN +-----------------+ | 540 | RCVD_ES v v 541 +-----++ LOST_ES ++---+-+ 542 | DF | | DF | 543 | DONE +<--------------+ CALC +<-+ 544 +------+ CALCULATED +----+-+ | 545 | | 546 +----+ 547 VLAN_CHANGE 548 RCVD_ES 549 LOST_ES 551 Figure 3 DF Election Finite State Machine 553 States: 555 1. INIT: Initial State 557 2. DF_WAIT: State in which the participant waits for enough 558 information to perform the DF election for the EVI/ESI/VLAN 559 combination. 561 3. DF_CALC: State in which the new DF is recomputed. 563 4. DF_DONE: State in which the according DF for the EVI/ESI/VLAN 564 combination has been elected. 566 5. ANY_STATE: Refers to any of the above states. 568 Events: 570 1. ES_UP: The ESI has been locally configured as 'up'. 572 2. ES_DOWN: The ESI has been locally configured as 'down'. 574 3. VLAN_CHANGE: The VLANs configured in a bundle (that uses the ESI) 575 changed. This event is necessary for VLAN Bundles only. 577 4. DF_TIMER: DF Wait timer [RFC7432] has expired. 579 5. RCVD_ES: A new or changed Ethernet Segment route is received in a 580 BGP REACH UPDATE. Receiving an unchanged UPDATE MUST NOT trigger 581 this event. 583 6. LOST_ES: A BGP UNREACH UPDATE for a previously received Ethernet 584 Segment route has been received. If an UNREACH is seen for a 585 route that has not been advertised previously, the event MUST NOT 586 be triggered. 588 7. CALCULATED: DF has been successfully calculated. 590 According actions when transitions are performed or states 591 entered/exited: 593 1. ANY_STATE on ES_DOWN: (i) stop DF wait timer (ii) assume NDF for 594 local PE. 596 2. INIT on ES_UP: transition to DF_WAIT. 598 3. INIT on VLAN_CHANGE, RCVD_ES or LOST_ES: do nothing. 600 4. DF_WAIT on entering the state: (i) start DF wait timer if not 601 started already or expired (ii) assume NDF for local PE. 603 5. DF_WAIT on VLAN_CHANGE, RCVD_ES or LOST_ES: do nothing. 605 6. DF_WAIT on DF_TIMER: transition to DF_CALC. 607 7. DF_CALC on entering or re-entering the state: (i) rebuild 608 candidate list, hash and perform election (ii) Afterwards FSM 609 generates CALCULATED event against itself. 611 8. DF_CALC on VLAN_CHANGE, RCVD_ES or LOST_ES: do as in transition 612 7. 614 9. DF_CALC on CALCULATED: mark election result for VLAN or bundle, 615 and transition to DF_DONE. 617 11. DF_DONE on exiting the state: if there is a new DF election 618 triggered and the current DF is lost, then assume NDF for local 619 PE for VLAN or VLAN Bundle. 621 12. DF_DONE on VLAN_CHANGE, RCVD_ES or LOST_ES: transition to 622 DF_CALC. 624 3.2. The DF Election Extended Community 626 For the DF election procedures to be consistent and unanimous, it is 627 necessary that all the participating PEs agree on the DF Election 628 algorithm and capabilities to be used. For instance, it is not 629 possible that some PEs continue to use the Default DF Election 630 algorithm and some PEs use HRW. For brown-field deployments and for 631 interoperability with legacy PEs, it is important that all PEs need 632 to have the capability to fall back on the Default DF Election. A PE 633 can indicate its willingness to support HRW and/or AC-DF by signaling 634 a DF Election Extended Community along with the Ethernet Segment 635 route (Type-4). 637 The DF Election Extended Community is a new BGP transitive extended 638 community attribute [RFC4360] that is defined to identify the DF 639 election procedure to be used for the Ethernet Segment. Figure 4 640 shows the encoding of the DF Election Extended Community. 642 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 1 643 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 644 | Type=0x06 | Sub-Type(0x06)| RSV | DF Alg | Bitmap ~ 645 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 646 ~ Bitmap | Reserved | 647 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 649 Figure 4 DF Election Extended Community 651 Where: 653 o Type is 0x06 as registered with IANA for EVPN Extended Communities. 655 o Sub-Type is 0x06 - "DF Election Extended Community" as requested by 656 this document to IANA. 658 o RSV - Reserved bits for future use. 660 o DF Alg (5 bits) - Encodes the DF Election algorithm values (between 661 0 and 31) that the advertising PE desires to use for the ES. This 662 document requests IANA to set up a registry called "DF Alg 663 Registry" and solicits the following values: 665 - Type 0: Default DF Election algorithm, or modulus-based algorithm 666 as in [RFC7432]. 668 - Type 1: HRW algorithm (explained in this document). 670 - Types 2-30: Unassigned. 672 - Type 31: Reserved for Experimental Use. 674 o Bitmap (2 octets) - Encodes "capabilities" to use with the DF 675 Election algorithm in the field "DF Alg". This document requests 676 IANA to create a registry for the Bitmap field, with values 0-15, 677 called "DF Election Capabilities" and solicits the following 678 values: 680 1 1 1 1 1 1 681 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 682 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 683 | |A| | 684 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 686 Figure 5 Bitmap field in the DF Election Extended Community 688 - Bit 0 (corresponds to Bit 24 of the DF Election Extended 689 Community): Unassigned. 691 - Bit 1: AC-DF (AC-Influenced DF Election, explained in this 692 document). When set to 1, it indicates the desire to use AC- 693 Influenced DF Election with the rest of the PEs in the ES. 695 - Bits 2-15: Unassigned. 697 The DF Election Extended Community is used as follows: 699 o A PE SHOULD attach the DF Election Extended Community to any 700 advertised ES route and the Extended Community MUST be sent if the 701 ES is locally configured with a DF election algorithm other than 702 the Default Election algorithm or if a capability is required to be 703 used. In the Extended Community, the PE indicates the desired "DF 704 Alg" algorithm and "Bitmap" capabilities to be used for the ES. 706 - Only one DF Election Extended Community can be sent along with an 707 ES route. Note that the intent is not for the advertising PE to 708 indicate all the supported DF election algorithms and 709 capabilities, but signal the preferred one. 711 - DF Algs 0 and 1 can be both used with bit AC-DF set to 0 or 1. 713 - In general, a specific DF Alg MAY determine the use of the 714 reserved bits in the Extended Community, which may be used in a 715 different way for a different DF Alg. 717 o When a PE receives the ES Routes from all the other PEs for the ES 718 in question, it checks to see if all the advertisements have the 719 extended community with the same DF Alg and Bitmap: 721 - In the case that they do, this particular PE MUST follow the 722 procedures for the advertised DF Alg and capabilities. For 723 instance, if all ES routes for a given ES indicate DF Alg HRW and 724 AC-DF set to 1, the receiving PE and by induction all the other 725 PEs in the ES will proceed to do DF Election as per the HRW 726 Algorithm and following the AC-DF procedures. 728 - Otherwise if even a single advertisement for the type-4 route is 729 not received with the locally configured DF Alg and capability, 730 the Default DF Election algorithm (modulus) algorithm MUST be 731 used as in [RFC7432]. This procedure handles the case where 732 participating PEs in the ES disagree about the DF algorithm and 733 capability to apply. 735 - The absence of the DF Election Extended Community MUST be 736 interpreted by a receiving PE as an indication of the Default DF 737 Election algorithm on the sending PE, that is, DF Alg 0 and no DF 738 Election capabilities. 740 o When all the PEs in an ES advertise DF Type 31, they will rely on 741 the local policy to decide how to proceed with the DF Election. 743 o For any new capability defined in the future, the 744 applicability/compatibility of this new capability to the existing 745 DF Algs must be assessed on a case by case basis. 747 o Likewise, for any new DF Alg defined in future, its 748 applicability/compatibility to the existing capabilities must be 749 assessed on a case by case basis. 751 3.2.1. Backward Compatibility 753 [RFC7432] implementations (i.e., those that predate this 754 specification) will not advertise the DF Election Extended Community. 755 That means that all other participating PEs in the ES will not 756 receive DF preferences and will revert to the Default DF Election 757 algorithm without AC-Influenced DF Election. 759 Similarly, a [RFC7432] implementation receiving a DF Election 760 Extended Community will ignore it and will continue to use the 761 Default DF Election algorithm. 763 3.3. Auto-Derivation of ES-Import Route Target 765 Section 7.6 of [RFC7432] describes how the value of the ES-Import 766 Route Target for ESI types 1, 2, and 3 can be auto-derived by using 767 the high-order six bytes of the nine byte ESI value. The same auto- 768 derivation procedure can be extended to ESI types 0, 4, and 5 as long 769 as it is ensured that the auto-derived values for ES-Import RT among 770 different ES types don't overlap. 772 4. The Highest Random Weight DF Election Algorithm 774 The procedure discussed in this section is applicable to the DF 775 Election in EVPN Services [RFC7432] and EVPN Virtual Private Wire 776 Services [RFC8214]. 778 Highest Random Weight (HRW) as defined in [HRW1999] is originally 779 proposed in the context of Internet Caching and proxy Server load 780 balancing. Given an object name and a set of servers, HRW maps a 781 request to a server using the object-name (object-id) and server-name 782 (server-id) rather than the server states. HRW forms a hash out of 783 the server-id and the object-id and forms an ordered list of the 784 servers for the particular object-id. The server for which the hash 785 value is highest, serves as the primary responsible for that 786 particular object, and the server with the next highest value in that 787 hash serves as the backup server. HRW always maps a given object name 788 to the same server within a given cluster; consequently it can be 789 used at client sites to achieve global consensus on object-server 790 mappings. When that server goes down, the backup server becomes the 791 responsible designate. 793 Choosing an appropriate hash function that is statistically oblivious 794 to the key distribution and imparts a good uniform distribution of 795 the hash output is an important aspect of the algorithm. Fortunately 796 many such hash functions exist. [HRW1999] provides pseudo-random 797 functions based on the Unix utilities rand and srand and easily 798 constructed XOR functions that perform considerably well. This 799 imparts very good properties in the load balancing context. Also each 800 server independently and unambiguously arrives at the primary server 801 selection. HRW already finds use in multicast and ECMP [RFC2991], 802 [RFC2992]. 804 4.1. HRW and Consistent Hashing 806 HRW is not the only algorithm that addresses the object to server 807 mapping problem with goals of fair load distribution, redundancy and 808 fast access. There is another family of algorithms that also 809 addresses this problem; these fall under the umbrella of the 810 Consistent Hashing Algorithms [CHASH]. These will not be considered 811 here. 813 4.2. HRW Algorithm for EVPN DF Election 815 This section describes the application of HRW to DF election. Let 816 DF(v) denote the Designated Forwarder and BDF(v) the Backup 817 Designated forwarder for the Ethernet Tag v, where v is the VLAN, Si 818 is the IP address of PE i, Es denotes the Ethernet Segment Identifier 819 and weight is a function of v, Si, and Es. 821 Note that while the DF election algorithm in [RFC7432] uses PE 822 address and vlan as inputs, this document uses Ethernet Tag, PE 823 address and ESI as inputs. This is because if the same set of PEs are 824 multi-homed to the same set of ESes, then the DF election algorithm 825 used in [RFC7432] would result in the same PE being elected DF for 826 the same set of broadcast domains on each ES, which can have adverse 827 side-effects on both load balancing and redundancy. Including ESI in 828 the DF election algorithm introduces additional entropy which 829 significantly reduces the probability of the same PE being elected DF 830 for the same set of broadcast domains on each ES. Therefore, the ESI 831 value in the Weight function below SHOULD be set to that of 832 corresponding ES. The ESI value MAY be set to all 0's in the Weight 833 function below if the operator so chooses. 835 In case of a VLAN Bundle service, v denotes the lowest VLAN similar 836 to the 'lowest VLAN in bundle' logic of [RFC7432]. 838 1. DF(v) = Si: Weight(v, Es, Si) >= Weight(v, Es, Sj), for all j. In 839 case of a tie, choose the PE whose IP address is numerically the 840 least. Note 0 <= i,j < Number of PEs in the redundancy group. 842 2. BDF(v) = Sk: Weight(v, Es, Si) >= Weight(v, Es, Sk) and Weight(v, 843 Es, Sk) >= Weight(v, Es, Sj). In case of tie choose the PE whose 844 IP address is numerically the least. 846 Since the Weight is a pseudo-random function with domain as the 847 three-tuple (v, Es, S), it is an efficient and deterministic 848 algorithm that is independent of the Ethernet Tag v sample space 849 distribution. Choosing a good hash function for the pseudo-random 850 function is an important consideration for this algorithm to perform 851 better than the Default algorithm. As mentioned previously, such 852 functions are described in the HRW paper. We take as candidate hash 853 function the first one out of the two that are preferred in 854 [HRW1999]: 856 Wrand(v, Es, Si) = (1103515245((1103515245.Si+12345) XOR 857 D(v,Es))+12345)(mod 2^31) 859 Here D(v,Es) is the 31-bit digest (CRC-32 and discarding the MSB as 860 in [HRW1999]) of the 14-byte stream, the Ethernet Tag v (4 bytes) 861 followed by the Ethernet Segment Identifier (10 bytes). It is 862 mandated that the 14-byte stream is formed by concatenation of the 863 Ethernet tag and the Ethernet Segment identifier in network byte 864 order. The CRC should proceed as if the stream is in network byte 865 order (big-endian). Si is address of the ith server. The server's IP 866 address length does not matter as only the low-order 31 bits are 867 modulo significant. 869 A point to note is that the Weight function takes into consideration 870 the combination of the Ethernet Tag, Ethernet Segment and the PE IP- 871 address, and the actual length of the server IP address (whether IPv4 872 or IPv6) is not really relevant. The Default algorithm in [RFC7432] 873 cannot employ both IPv4 and IPv6 PE addresses, since [RFC7432] does 874 not specify how to decide on the ordering (the ordinal list) when 875 both IPv4 and IPv6 PEs are present. 877 HRW solves the disadvantages pointed out in Section 2.2.1 and 878 ensures: 880 o with very high probability that the task of DF election for the 881 VLANs configured on an ES is more or less equally distributed among 882 the PEs even for the 2 PE case. 884 o If a PE that is not the DF or the BDF for that VLAN, goes down or 885 its connection to the ES goes down, it does not result in a DF or 886 BDF reassignment. This saves computation, especially in the case 887 when the connection flaps. 889 o More importantly it avoids the needless disruption case of Section 890 2.2.1 (3), that is inherent in the existing Default DF Election. 892 o In addition to the DF, the algorithm also furnishes the BDF, which 893 would be the DF if the current DF fails. 895 5. The Attachment Circuit Influenced DF Election Capability 897 The procedure discussed in this section is applicable to the DF 898 Election in EVPN Services [RFC7432] and EVPN Virtual Private Wire 899 Services [RFC8214]. 901 The AC-DF capability MAY be used with any "DF Alg" algorithm. It MUST 902 modify the DF Election procedures by removing from consideration any 903 candidate PE in the ES that cannot forward traffic on the AC that 904 belongs to the BD. This section is applicable to VLAN-Based and VLAN 905 Bundle service interfaces. Section 5.1 describes the procedures for 906 VLAN-Aware Bundle interfaces. 908 In particular, when used with the Default DF Alg, the AC-DF 909 capability modifies the Step 3 in the DF Election procedure described 910 in [RFC7432] Section 8.5, as follows: 912 3. When the timer expires, each PE builds an ordered "candidate" list 913 of the IP addresses of all the PE nodes attached to the Ethernet 914 Segment (including itself), in increasing numeric value. The 915 candidate list is based on the Originator Router's IP addresses of 916 the ES routes, but excludes any PE from whom no Ethernet A-D per 917 ES route has been received, or from whom the route has been 918 withdrawn. Afterwards, the DF Election algorithm is applied on a 919 per or , however, the IP address for a 920 PE will not be considered candidate for a given or 921 until the corresponding Ethernet A-D per EVI 922 route has been received from that PE. In other words, the ACS on 923 the ES for a given PE must be UP so that the PE is considered as 924 candidate for a given BD. 926 The above paragraph differs from [RFC7432] Section 8.5, Step 3, in 927 two aspects: 929 o Any DF Alg algorithm can be used, and not only the modulus-based 930 one (which is the Default DF Election, or DF Alg 0 in this 931 document). 933 o The candidate list is pruned based upon non-receipt of Ethernet A-D 934 routes: a PE's IP address MUST be removed from the ES candidate 935 list if its Ethernet A-D per ES route is withdrawn. A PE's IP 936 address MUST NOT be considered as candidate DF for a or 937 , if its Ethernet A-D per EVI route for the 938 or respectively, is withdrawn. 940 The following example illustrates the AC-DF behavior applied to the 941 Default DF election algorithm, assuming the network in Figure 2: 943 a) When PE1 and PE2 discover ES12, they advertise an ES route for 944 ES12 with the associated ES-import extended community and the DF 945 Election Extended Community indicating AC-DF=1; they start a timer 946 at the same time. Likewise, PE2 and PE3 advertise an ES route for 947 ES23 with AC-DF=1 and start a timer. 949 b) PE1/PE2 advertise an Ethernet A-D per ES route for ES12, and 950 PE2/PE3 advertise an Ethernet A-D per ES route for ES23. 952 c) In addition, PE1/PE2/PE3 advertise an Ethernet A-D per EVI route 953 for AC1, AC2, AC3 and AC4 as soon as the ACs are enabled. Note 954 that the AC can be associated to a single customer VID (e.g. VLAN- 955 based service interfaces) or a bundle of customer VIDs (e.g. VLAN 956 Bundle service interfaces). 958 d) When the timer expires, each PE builds an ordered "candidate" list 959 of the IP addresses of all the PE nodes connected to the Ethernet 960 Segment (including itself) as explained above in [RFC7432] Step 3. 961 Any PE from which an Ethernet A-D per ES route has not been 962 received is pruned from the list. 964 e) When electing the DF for a given BD, a PE will not be considered 965 candidate until an Ethernet A-D per EVI route has been received 966 from that PE. In other words, the ACS on the ES for a given PE 967 must be UP so that the PE is considered as candidate for a given 968 BD. For example, PE1 will not consider PE2 as candidate for DF 969 election for until an Ethernet A-D per EVI route is 970 received from PE2 for . 972 f) Once the PEs with ACS = DOWN for a given BD have been removed from 973 the candidate list, the DF Election can be applied for the 974 remaining N candidates. 976 Note that this procedure only modifies the existing EVPN control 977 plane by adding and processing the DF Election Extended Community, 978 and by pruning the candidate list of PEs that take part in the DF 979 election. 981 In addition to the events defined in the FSM in Section 3.1, the 982 following events SHALL modify the candidate PE list and trigger the 983 DF re-election in a PE for a given or . In 984 the FSM of Figure 3, the events below MUST trigger a transition from 985 DF_DONE to DF_CALC: 987 i. Local AC going DOWN/UP. 989 ii. Reception of a new Ethernet A-D per EVI update/withdraw for the 990 or . 992 iii. Reception of a new Ethernet A-D per ES update/withdraw for the 993 ES. 995 5.1. AC-Influenced DF Election Capability For VLAN-Aware Bundle Services 997 The procedure described in section 5 works for VLAN-based and VLAN 998 Bundle service interfaces since, for those service types, a PE 999 advertises only one Ethernet A-D per EVI route per or 1000 . The withdrawal of such route means that the PE 1001 cannot forward traffic on that particular or , therefore the PE can be removed from consideration for DF. 1004 According to [RFC7432], in VLAN-aware Bundle services, the PE 1005 advertises multiple Ethernet A-D per EVI routes per 1006 (one route per Ethernet Tag), while the DF Election is still 1007 performed per . The withdrawal of an individual route 1008 only indicates the unavailability of a specific AC but not 1009 necessarily all the ACs in the . 1011 This document modifies the DF Election for VLAN-Aware Bundle services 1012 in the following way: 1014 o After confirming that all the PEs in the ES advertise the AC-DF 1015 capability, a PE will perform a DF Election per , as 1016 opposed to per in [RFC7432]. Now, the withdrawal 1017 of an Ethernet A-D per EVI route for a VLAN will indicate that the 1018 advertising PE's ACS is DOWN and the rest of the PEs in the ES can 1019 remove the PE from consideration for DF in the . 1021 o The PEs will now follow the procedures in section 5. 1023 For example, assuming three Bridge Tables in PE1 for the same MAC-VRF 1024 (each one associated to a different Ethernet Tag, e.g. VLAN-1, VLAN-2 1025 and VLAN-3), PE1 will advertise three Ethernet A-D per EVI routes for 1026 ES12. Each of the three routes will indicate the status of each of 1027 the three ACs in ES12. PE1 will be considered as a valid candidate PE 1028 for DF Election in , , as 1029 long as its three routes are active. For instance, if PE1 withdraws 1030 the Ethernet A-D per EVI routes for , the PEs in ES12 1031 will not consider PE1 as a suitable DF candidate for . 1032 PE1 will still be considered for and 1033 since its routes are active. 1035 6. Solution Benefits 1037 The solution described in this document provides the following 1038 benefits: 1040 a) Extends the DF Election in [RFC7432] to address the unfair load- 1041 balancing and potential black-holing issues of the Default DF 1042 Election algorithm. The solution is applicable to the DF Election 1043 in EVPN Services [RFC7432] and EVPN Virtual Private Wire Services 1044 [RFC8214]. 1046 b) It defines a way to signal the DF Election algorithm and 1047 capabilities intended by the advertising PE. This is done by 1048 defining the DF Election Extended Community, which allow signaling 1049 of the capabilities supported by this document as well as any 1050 other future DF Election algorithms and capabilities. 1052 c) The solution is backwards compatible with the procedures defined 1053 in [RFC7432]. If one or more PEs in the ES do not support the new 1054 procedures, they will all follow the [RFC7432] DF Election. 1056 7. Security Considerations 1058 This document addresses some identified issues in the DF Election 1059 procedures described in [RFC7432] by defining a new DF Election 1060 framework. In general, this framework allows the PEs that are part of 1061 the same Ethernet Segment to exchange additional information and 1062 agree on the DF Election Type and Capabilities to be used. 1064 Following the procedures in this document, the operator will minimize 1065 undesired situations such as unfair load-balancing, service 1066 disruption and traffic black-holing. Since those situations may have 1067 been purposely created by a malicious user with access to the 1068 configuration of one PE, this document enhances also the security of 1069 the network. Note that the network will not benefit of the new 1070 procedures if the configuration of one of the PEs in the ES is 1071 changed to the Default [RFC7432] DF Election. 1073 In addition, the new framework is extensible and allows for future 1074 new security enhancements that are out of the scope of this document. 1075 Finally, since this document extends the procedures in [RFC7432], the 1076 same Security Considerations described in [RFC7432] are valid for 1077 this document. 1079 8. IANA Considerations 1081 IANA is requested to: 1083 o Allocate Sub-Type value 0x06 in the "EVPN Extended Community Sub- 1084 Types" registry defined in [RFC7153] as follows: 1086 SUB-TYPE VALUE NAME Reference 1087 -------------- ------------------------- ------------- 1088 0x06 DF Election Extended Community This document 1090 o Set up a registry called "DF Alg" for the DF Alg field in the 1091 Extended Community. New registrations will be made through the "RFC 1092 Required" procedure defined in [RFC8126]. Value 31 is for 1093 Experimental use and does not require any other RFC than this 1094 document. The following initial values in that registry are 1095 requested: 1097 Alg Name Reference 1098 ---- -------------- ------------- 1099 0 Default DF Election This document 1100 1 HRW algorithm This document 1101 2-30 Unassigned 1102 31 Reserved for Experimental use This document 1104 o Set up a registry called "DF Election Capabilities" for the two- 1105 octet Bitmap field in the Extended Community. New registrations 1106 will be made through the "RFC Required" procedure defined in 1107 [RFC8126]. The following initial value in that registry is 1108 requested: 1110 Bit Name Reference 1111 ---- -------------- ------------- 1112 0 Unassigned 1113 1 AC-DF capability This document 1114 2-15 Unassigned 1116 9. References 1117 9.1. Normative References 1119 [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., 1120 Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet 1121 VPN", RFC 7432, DOI 10.17487/RFC7432, February 2015, 1122 . 1124 [RFC8214] Boutros, S., Sajassi, A., Salam, S., Drake, J., and J. 1125 Rabadan, "Virtual Private Wire Service Support in Ethernet VPN", RFC 1126 8214, DOI 10.17487/RFC8214, August 2017, . 1129 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1130 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1131 1997, . 1133 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 1134 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, 1135 . 1137 [RFC4360] Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended 1138 Communities Attribute", RFC 4360, DOI 10.17487/RFC4360, February 1139 2006, . 1141 [RFC7153] Rosen, E. and Y. Rekhter, "IANA Registries for BGP 1142 Extended Communities", RFC 7153, DOI 10.17487/RFC7153, March 2014, 1143 . 1145 [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for 1146 Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, 1147 DOI 10.17487/RFC8126, June 2017, . 1150 9.2. Informative References 1152 [VPLS-MH] Kothari, Henderickx et al., "BGP based Multi-homing in 1153 Virtual Private LAN Service", draft-ietf-bess-vpls-multihoming- 1154 02.txt, work in progress, September, 2018. 1156 [CHASH] Karger, D., Lehman, E., Leighton, T., Panigrahy, R., Levine, 1157 M., and D. Lewin, "Consistent Hashing and Random Trees: Distributed 1158 Caching Protocols for Relieving Hot Spots on the World Wide Web", ACM 1159 Symposium on Theory of Computing ACM Press New York, May 1997. 1161 [CLRS2009] Cormen, T., Leiserson, C., Rivest, R., and C. Stein, 1162 "Introduction to Algorithms (3rd ed.)", MIT Press and McGraw-Hill 1163 ISBN 0-262-03384-4., February 2009. 1165 [RFC2991] Thaler, D. and C. Hopps, "Multipath Issues in Unicast and 1166 Multicast Next-Hop Selection", RFC 2991, DOI 10.17487/RFC2991, 1167 November 2000, . 1169 [RFC2992] Hopps, C., "Analysis of an Equal-Cost Multi-Path 1170 Algorithm", RFC 2992, DOI 10.17487/RFC2992, November 2000, 1171 . 1173 [HRW1999] Thaler, D. and C. Ravishankar, "Using Name-Based Mappings 1174 to Increase Hit Rates", IEEE/ACM Transactions in networking Volume 6 1175 Issue 1, February 1998, . 1178 10. Acknowledgments 1180 The authors want to thank Sriram Venkateswaran, Laxmi Padakanti, 1181 Ranganathan Boovaraghavan, Tamas Mondal, Sami Boutros, Jakob Heitz, 1182 Mrinmoy Ghosh, Leo Mermelstein, Mankamana Mishra, Anoop Ghanwani and 1183 Samir Thoria for their review and contributions. Special thanks to 1184 Stephane Litkowski for his thorough review and detailed 1185 contributions. 1187 11. Contributors 1189 In addition to the authors listed on the front page, the following 1190 coauthors have also contributed to this document: 1192 Antoni Przygienda 1193 Juniper Networks, Inc. 1194 1194 N. Mathilda Drive 1195 Sunnyvale, CA 95134 1196 USA 1197 Email: prz@juniper.net 1199 Vinod Prabhu 1200 Nokia 1201 Email: vinod.prabhu@nokia.com 1203 Wim Henderickx 1204 Nokia 1205 Email: wim.henderickx@nokia.com 1207 Wen Lin 1208 Juniper Networks, Inc. 1209 Email: wlin@juniper.net 1211 Patrice Brissette 1212 Cisco Systems 1213 Email: pbrisset@cisco.com 1215 Keyur Patel 1216 Arrcus, Inc 1217 Email: keyur@arrcus.com 1219 Autumn Liu 1220 Ciena 1221 Email: hliu@ciena.com 1223 Authors' Addresses 1225 Jorge Rabadan 1226 Nokia 1227 777 E. Middlefield Road 1228 Mountain View, CA 94043 USA 1229 Email: jorge.rabadan@nokia.com 1231 Satya Mohanty 1232 Cisco Systems, Inc. 1233 225 West Tasman Drive 1234 San Jose, CA 95134 1235 USA 1236 Email: satyamoh@cisco.com 1238 Ali Sajassi 1239 Cisco Systems, Inc. 1240 225 West Tasman Drive 1241 San Jose, CA 95134 1242 USA 1243 Email: sajassi@cisco.com 1245 John Drake 1246 Juniper Networks, Inc. 1247 1194 N. Mathilda Drive 1248 Sunnyvale, CA 95134 1249 USA 1250 Email: jdrake@juniper.net 1252 Kiran Nagaraj 1253 Nokia 1254 701 E. Middlefield Road 1255 Mountain View, CA 94043 USA 1256 Email: kiran.nagaraj@nokia.com 1257 Senthil Sathappan 1258 Nokia 1259 701 E. Middlefield Road 1260 Mountain View, CA 94043 USA 1261 Email: senthil.sathappan@nokia.com