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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Missing Reference: 'RFC2119' is mentioned on line 338, but not defined == Unused Reference: 'RFC4684' is defined on line 360, but no explicit reference was found in the text == Outdated reference: A later version (-05) exists of draft-ietf-bess-vpls-multihoming-01 Summary: 1 error (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 BESS Workgroup J. Rabadan 3 Internet Draft K. Nagaraj 4 S. Sathappan 5 Intended status: Informational V. Prabhu 6 W. Henderickx 7 Nokia 9 A. Liu 10 Ericsson 12 W. Lin 13 Juniper Networks 15 Expires: April 14, 2017 October 11, 2016 17 AC-Influenced Designated Forwarder Election for EVPN 18 draft-ietf-bess-evpn-ac-df-00 20 Abstract 22 The Designated Forwarder (DF) in EVPN networks is the PE responsible 23 for sending multicast, broadcast and unknown unicast traffic to a 24 multi-homed CE, on a given Ethernet Tag on a particular Ethernet 25 Segment (ES). The DF is selected based on the list of PEs that 26 advertise the Ethernet Segment Identifier (ESI) to the EVPN network. 27 While PE node or link failures trigger the DF re-election for a given 28 , individual Attachment Circuit (AC) or MAC-VRF failures do 29 not trigger such DF re-election and the traffic may therefore be 30 permanently impacted, even though there is an alternative path. This 31 document improves the DF election algorithm so that the AC status can 32 influence the result of the election and this type of "logical" 33 failures can be protected too. 35 Status of this Memo 37 This Internet-Draft is submitted in full conformance with the 38 provisions of BCP 78 and BCP 79. 40 Internet-Drafts are working documents of the Internet Engineering 41 Task Force (IETF), its areas, and its working groups. Note that 42 other groups may also distribute working documents as Internet- 43 Drafts. 45 Internet-Drafts are draft documents valid for a maximum of six months 46 and may be updated, replaced, or obsoleted by other documents at any 47 time. It is inappropriate to use Internet-Drafts as reference 48 material or to cite them other than as "work in progress." 50 The list of current Internet-Drafts can be accessed at 51 http://www.ietf.org/ietf/1id-abstracts.txt 53 The list of Internet-Draft Shadow Directories can be accessed at 54 http://www.ietf.org/shadow.html 56 This Internet-Draft will expire on April 14, 2017. 58 Copyright Notice 60 Copyright (c) 2016 IETF Trust and the persons identified as the 61 document authors. All rights reserved. 63 This document is subject to BCP 78 and the IETF Trust's Legal 64 Provisions Relating to IETF Documents 65 (http://trustee.ietf.org/license-info) in effect on the date of 66 publication of this document. Please review these documents 67 carefully, as they describe your rights and restrictions with respect 68 to this document. Code Components extracted from this document must 69 include Simplified BSD License text as described in Section 4.e of 70 the Trust Legal Provisions and are provided without warranty as 71 described in the Simplified BSD License. 73 Table of Contents 75 1. Problem Statement . . . . . . . . . . . . . . . . . . . . . . . 3 76 2. Solution Description . . . . . . . . . . . . . . . . . . . . . 4 77 2.1. Current DF Election Procedure And AC Failures . . . . . . . 5 78 2.2. The Attachment Circuit (AC) Influenced DF Election . . . . 6 79 2.3. AC-Influenced DF Election For VLAN-Aware Bundle Services . 7 80 3. Solution benefits . . . . . . . . . . . . . . . . . . . . . . . 8 81 4. Conventions used in this document . . . . . . . . . . . . . . . 8 82 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 8 83 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8 84 7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 85 7.1. Normative References . . . . . . . . . . . . . . . . . . . 9 86 7.2. Informative References . . . . . . . . . . . . . . . . . . 9 87 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 9 88 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 90 1. Problem Statement 92 [RFC7432] defines the Designated Forwarder (DF) as the EVPN PE 93 responsible for: 95 o Flooding Broadcast, Unknown unicast and Multicast traffic (BUM), on 96 a given Ethernet Tag on a particular Ethernet Segment (ES), to the 97 CE. This is valid for single-active and all-active EVPN 98 multi-homing. 100 o Sending unicast traffic on a given Ethernet Tag on a particular ES 101 to the CE. This is valid for single-active multi-homing. 103 The default DF election algorithm defined by [RFC7432] is called 104 service-carving and, for a given ES, is based on a (V mod N)= i 105 function that provides a local DF election of a PEi at 106 level. V is the Ethernet Tag associated to the EVI (the numerically 107 lowest Ethernet Tag value in case of multiple Ethernet Tags), whereas 108 N is the number of PEs for which ES routes have been successfully 109 imported. In other words, EVPN's service-carving takes into account 110 only two variables in the DF election for a given ESI: the existence 111 of the PE's IP address on the candidate list and the locally 112 provisioned Ethernet Tags. 114 If the DF for an fails (due to physical link/node 115 failures) an ES route withdrawn will make the Non-DF (NDF) PEs re- 116 elect the DF for that and the service will be recovered. 118 However the current DF election procedure does not provide a 119 protection against "logical" failures or human errors that may occur 120 at service level on the DF, while the list of active PEs for a given 121 ES does not change. These failures may have an impact not only on the 122 local PE where the issue happens, but also on the rest of the PEs of 123 the ES. Some examples of such logical failures are listed below: 125 a) A given individual Attachment Circuit (AC) defined in an ES is 126 accidentally shutdown or even not provisioned yet (hence the 127 Attachment Circuit Status - ACS - is DOWN), while the ES is 128 operationally active (since the ES route is active). 130 b) A given MAC-VRF - with an ES defined - is shutdown or not 131 provisioned yet, while the ES is operationally active (since the 132 ES route is active). In this case, the ACS of all the AC defined 133 in that MAC-VRF is considered to be DOWN. 135 Neither (a) nor (b) will trigger the DF re-election on the remote PEs 136 for a given ES since the ACS is not taken into account in the DF 137 election procedures. While the ACS is used as a DF election tie- 138 breaker and trigger in [VPLS-MH], there is no procedure defined in 139 [RFC7432] to trigger the DF re-election based on the ACS change on 140 the DF. 142 This document improves the [RFC7432] service-carving procedure so 143 that the ACS may be taken into account as a variable in the DF 144 election, and therefore EVPN can provide protection against logical 145 failures. 147 2. Solution Description 149 The ACS for a given Ethernet Tag on an ES is implicitly conveyed in 150 the corresponding EVPN A-D per EVI route for that given . This section describes how to use the A-D per EVI 152 routes to improve the DF election algorithm. 154 Figure 1 illustrates an example EVPN network that will be used to 155 describe the proposed solution. 157 EVI-1 is defined in PE-1, PE-2, PE-3 and PE-4. CE12 is a multi-homed 158 CE connected to ESI12 in PE-1 and PE-2. Similarly CE23 is multi-homed 159 to PE-2 and PE-3 using ESI23. Both, CE12 and CE23, are connected to 160 EVI-1 through VLAN-based service interfaces: CE12-VID 1 (VLAN ID 1 on 161 CE12) is associated to AC1 and AC2 in EVI-1, whereas CE23-VID 1 is 162 associated to AC3 and AC4 in EVI-1. Note that there are other ACs 163 defined on these ES mapped to different EVIs. 165 +---+ 166 |CE4| 167 +---+ 168 | 169 PE-4 | 170 +-----+-----+ 171 +---------------| +-----+ |---------------+ 172 | | |EVI-1| | | 173 | +-----------+ | 174 | | 175 | EVPN | 176 | | 177 | PE-1 PE-2 PE-3 | 178 | (NDF) (DF) (NDF)| 179 +-----------+ +-----------+ +-----------+ 180 | |EVI-1| | | |EVI-1| | | |EVI-1| | 181 | +-----+ |-------| +-----+ |-------| +-----+ | 182 +-----------+ +-----------+ +-----------+ 183 AC1\ ESI12 /AC2 AC3\ ESI23 /AC4 184 \ / \ / 185 \ / \ / 186 +----+ +----+ 187 |CE12| |CE23| 188 +----+ +----+ 190 Figure 1 EVPN network example 192 2.1. Current DF Election Procedure And AC Failures 194 After running the service-carving DF election algorithm, PE-2 turns 195 out to be the DF for ESI12 and ESI23 in EVI-1. The following two 196 examples illustrate the issues with the existing defined procedure in 197 [RFC7432]: 199 a) If AC2 is accidentally shutdown or even not configured, CE12 200 traffic will be impacted. In case of all-active multi-homing, only 201 the BUM traffic to CE12 will be impacted, whereas for single-active 202 multi-homing all the traffic to/from CE12 will be discarded. This is 203 due to the fact that a logical failure in PE-2 AC2 may not trigger an 204 ES route withdrawn for ESI12 (since there are still other ACs active 205 on ESI12) and therefore PE-1 will not re-run the DF election 206 procedures. 208 b) If EVI-1 is administratively shutdown or even not configured yet 209 on PE-2, CE12 and CE23 will both be impacted: BUM traffic to both CEs 210 will be discarded in case of all-active multi-homing and all traffic 211 will be discarded to/from the CEs in case of single-active 212 multi-homing. This is due to the fact that PE-1 and PE-3 will not 213 re-run the DF election procedures and will keep assuming PE-2 is the 214 DF. 216 According to [RFC7432], "when an Ethernet tag is decommissioned on an 217 Ethernet segment, then the PE MUST withdraw the Ethernet A-D per EVI 218 route(s) announced for the that are impacted by 219 the decommissioning", however, while this A-D per EVI route 220 withdrawal is used at the remote PEs performing aliasing or backup 221 procedures, it is not used to influence the DF election for the 222 affected EVIs. 224 2.2. The Attachment Circuit (AC) Influenced DF Election 226 Modifying the service-carving DF election procedure in the following 227 way solves the issue: 229 1. When PE-1 and PE-2 discover ESI12, they advertise an ES route for 230 ESI12 with the associated ES-import extended community, starting a 231 timer at the same time. Likewise, PE-2 and PE-3 advertise an ES 232 route for ESI23 and start a timer. 234 2. Similarly, PE-1 and PE-2 advertise an Ethernet A-D per ES route 235 for ESI12, and PE-2/PE-3 advertise an Ethernet A-D per ES route 236 for ESI23. 238 3. In addition, PE-1/PE-2/PE-3 advertise an Ethernet A-D per EVI 239 route for AC1, AC2, AC3 and AC4 as soon as the ACs are enabled. 240 Note that the AC can be associated to a single customer VID (e.g. 241 VLAN-based service interfaces) or a bundle of customer VIDs (e.g. 242 VLAN-bundle service interfaces). 244 4. When the timer expires, each PE builds an ordered "candidate" list 245 of the IP addresses of all the PE nodes connected to the Ethernet 246 Segment (including itself), in increasing numeric order. The 247 candidate list is based on the Originator Router's IP addresses of 248 the ES routes, excluding all the PEs for which no Ethernet A-D per 249 ES route has been received. 251 5. When electing the DF for a given EVI, a PE will not be considered 252 candidate until an Ethernet A-D per EVI route has been received 253 from that PE. In other words, the ACS on the ESI for a given PE 254 must be UP so that the PE is considered as candidate for a given 255 EVI. For example, PE-1 will not consider PE-2 as candidate for DF 256 election for until an Ethernet A-D per EVI route is 257 received from PE-2 for . 259 6. Once the PEs with ACS = DOWN for a given EVI have been eliminated 260 from the candidate list, the (V mod N) = i function can be applied 261 for the remaining N candidates, as per [RFC7432]. 263 Note that this procedure does not modify the existing EVPN control 264 plane whatsoever. It only modifies the candidate list of PEs taken 265 into account for the DF election algorithm defined in [RFC7432]. 267 In addition to the procedure described above, the following events 268 SHALL modify the candidate PE list and trigger the DF re-election in 269 a PE for a given : 271 a) Local ES going DOWN due to a physical failure or reception of an 272 ES route withdraw for that ESI. 274 b) Local ES going UP due to its detection/configuration or reception 275 of a new ES route update for that ESI. 277 c) Local AC going DOWN/UP. 279 d) Reception of a new Ethernet A-D per EVI update/withdraw for the 280 . 282 e) Reception of a new Ethernet A-D per ES update/withdraw for the 283 ESI. 285 This procedure is backwards compatible with the DF election 286 procedures described in [RFC7432] since it does not add any new 287 extension in the control plane, however, a PE not supporting the 288 procedures in this document SHOULD NOT share a multi-homed ES with a 289 PE following this solution since both PEs may end up with an 290 inconsistent view on who the DF is. The AC influenced DF election 291 procedures SHOULD be enabled by an administrative option and only 292 used when all the PEs in the ES support it. 294 2.3. AC-Influenced DF Election For VLAN-Aware Bundle Services 296 The procedure described section 2.2 works for VLAN-based and VLAN- 297 bundle service interfaces since, for those service types, a PE 298 advertises only one Ethernet A-D per EVI route per . The 299 withdrawal of such route means that the PE cannot forward traffic on 300 that particular . 302 In VLAN-aware bundle services, the PE advertises multiple Ethernet A- 303 D per EVI routes per (one route per Ethernet Tag). The 304 withdrawal of an individual route only indicates the unavailability 305 of a specific AC but not necessarily all the ACs in the . 307 For the specific case of VLAN-aware bundle services, the DF election 308 will be influenced by the update/withdraw of any of the Ethernet A-D 309 per EVI routes in the . 311 For example, assuming three bridge tables in PE-1 for the same MAC- 312 VRF (each one associated to a different Ethernet Tag), PE-1 will 313 advertise three Ethernet A-D per EVI routes for . Each of 314 the three routes will indicate the status of each AC in . 315 PE-1 will be considered as a valid candidate PE for DF election as 316 long as the three routes are active. If PE-1 withdraws one or more of 317 the Ethernet A-D per EVI routes for , the PEs in ESI12 318 will not consider PE-1 as a suitable DF candidate for . 320 3. Solution benefits 322 The solution described in this document provides the following 323 benefits: 325 a) Improves the DF election procedures for EVPN so that failures due 326 to human errors, logical failures or even delay in provisioning of 327 Attachment Circuits can be protected by multi-homing. 329 b) It does not modify or add any BGP new attributes or NLRI changes. 331 c) It is backwards compatible with the procedures defined in RFC7432. 333 4. Conventions used in this document 335 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 336 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 337 document are to be interpreted as described in RFC-2119 [RFC2119]. 339 In this document, these words will appear with that interpretation 340 only when in ALL CAPS. Lower case uses of these words are not to be 341 interpreted as carrying RFC-2119 significance. 343 In this document, the characters ">>" preceding an indented line(s) 344 indicates a compliance requirement statement using the key words 345 listed above. This convention aids reviewers in quickly identifying 346 or finding the explicit compliance requirements of this RFC. 348 5. Security Considerations 350 The same Security Considerations described in [RFC7432] are valid for 351 this document. 353 6. IANA Considerations 354 There are no new IANA considerations in this document. 356 7. References 358 7.1. Normative References 360 [RFC4684] Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk, 361 R., Patel, K., and J. Guichard, "Constrained Route Distribution for 362 Border Gateway Protocol/MultiProtocol Label Switching (BGP/MPLS) 363 Internet Protocol (IP) Virtual Private Networks (VPNs)", RFC 4684, 364 DOI 10.17487/RFC4684, November 2006, . 367 [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., 368 Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet 369 VPN", RFC 7432, DOI 10.17487/RFC7432, February 2015, . 372 7.2. Informative References 374 [VPLS-MH] Kothari, Henderickx et al., "BGP based Multi-homing in 375 Virtual Private LAN Service", draft-ietf-bess-vpls-multihoming- 376 01.txt, work in progress, January, 2016. 378 8. Acknowledgments 380 Will be added. 382 Authors' Addresses 384 Jorge Rabadan 385 Nokia 386 777 E. Middlefield Road 387 Mountain View, CA 94043 USA 388 Email: jorge.rabadan@nokia.com 390 Kiran Nagaraj 391 Nokia 392 Email: kiran.nagaraj@nokia.com 394 Senthil Sathappan 395 Nokia 396 Email: senthil.sathappan@nokia.com 397 Vinod Prabhu 398 Nokia 399 Email: vinod.prabhu@nokia.com 401 Wim Henderickx 402 Nokia 403 Email: wim.henderickx@nokia.com 405 Autumn Liu 406 Ericsson 407 Email: autumn.liu@ericsson.com 409 Wen Lin 410 Juniper Networks, Inc. 411 Email: wlin@juniper.net