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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 L2VPN Workgroup Ali Sajassi 3 INTERNET-DRAFT Samer Salam 4 Intended Status: Standards Track Sami Boutros 5 Cisco 7 Wim Henderickx Jim Uttaro 8 Jorge Rabadan AT&T 9 Alcatel-Lucent 10 Aldrin Isaac 11 Bloomberg 13 Expires: April 27, 2015 October 27, 2014 15 E-TREE Support in EVPN & PBB-EVPN 16 draft-sajassi-bess-evpn-etree-00 18 Abstract 20 The Metro Ethernet Forum (MEF) has defined a rooted-multipoint 21 Ethernet service known as Ethernet Tree (E-Tree). [ETREE-FMWK] 22 proposes a solution framework for supporting this service in MPLS 23 networks. This document discusses how those functional requirements 24 can be easily met with EVPN. 26 Status of this Memo 28 This Internet-Draft is submitted to IETF in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF), its areas, and its working groups. Note that 33 other groups may also distribute working documents as 34 Internet-Drafts. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 The list of current Internet-Drafts can be accessed at 42 http://www.ietf.org/1id-abstracts.html 44 The list of Internet-Draft Shadow Directories can be accessed at 45 http://www.ietf.org/shadow.html 47 Copyright and License Notice 49 Copyright (c) 2013 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (http://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 3 66 2 E-Tree Scenarios and EVPN / PBB-EVPN Support . . . . . . . . . 3 67 2.1 Scenario 1: Leaf OR Root site(s) per PE . . . . . . . . . . 3 68 2.2 Scenario 2: Leaf AND Root site(s) per PE . . . . . . . . . . 4 69 2.3 Scenario 3: Leaf AND Root site(s) per Ethernet Segment . . . 4 70 3 Operation for EVPN . . . . . . . . . . . . . . . . . . . . . . . 5 71 3.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 5 72 3.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 6 73 3.3 E-TREE Traffic Flows for EVPN . . . . . . . . . . . . . . . 7 74 3.3.1 E-Tree with MAC Learning . . . . . . . . . . . . . . . . 7 75 3.3.2 E-Tree without MAC Learning . . . . . . . . . . . . . . 8 76 4 Operation for PBB-EVPN . . . . . . . . . . . . . . . . . . . . . 8 77 4.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 9 78 4.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 9 79 5 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 10 80 6 Security Considerations . . . . . . . . . . . . . . . . . . . . 10 81 7 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 10 82 8 References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 83 8.1 Normative References . . . . . . . . . . . . . . . . . . . 10 84 8.2 Informative References . . . . . . . . . . . . . . . . . . 10 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 87 1 Introduction 89 The Metro Ethernet Forum (MEF) has defined a rooted-multipoint 90 Ethernet service known as Ethernet Tree (E-Tree). In an E-Tree 91 service, endpoints are labeled as either Root or Leaf sites. Root 92 sites can communicate with all other sites. Leaf sites can 93 communicate with Root sites but not with other Leaf sites. 95 [ETREE-FMWK] proposes the solution framework for supporting E-Tree 96 service in MPLS networks. The document identifies the functional 97 components of the overall solution to emulate E-Tree services in 98 addition to Ethernet LAN (E-LAN) services on an existing MPLS 99 network. 101 [EVPN] is a solution for multipoint L2VPN services, with advanced 102 multi-homing capabilities, using BGP for distributing customer/client 103 MAC address reach-ability information over the MPLS/IP network. [PBB- 104 EVPN] combines the functionality of EVPN with [802.1ah] Provider 105 Backbone Bridging for MAC address scalability. 107 This document discusses how the functional requirements for E-Tree 108 service can be easily met with EVPN and PBB-EVPN. 110 1.1 Terminology 112 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 113 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 114 document are to be interpreted as described in RFC 2119 [KEYWORDS]. 116 2 E-Tree Scenarios and EVPN / PBB-EVPN Support 118 In this section, we will categorize support for E-Tree into three 119 different scenarios, depending on the nature of the site association 120 (Root/Leaf) per PE or per Ethernet Segment: 122 - Leaf OR Root site(s) per PE 124 - Leaf AND Root site(s) per PE 126 - Leaf AND Root site(s) per Ethernet Segment 128 2.1 Scenario 1: Leaf OR Root site(s) per PE 130 In this scenario, a PE may have Root sites OR Leaf sites for a given 131 VPN instance, but not both concurrently. The PE may have both Root 132 and Leaf sites albeit for different VPNs. Every Ethernet Segment 133 connected to the PE is uniquely identified as either a Root or a Leaf 134 site. 136 +---------+ +---------+ 137 | PE1 | | PE2 | 138 +---+ | +---+ | +------+ | +---+ | +---+ 139 |CE1+-----ES1----+--+ | | | MPLS | | | +--+----ES2-----+CE2| 140 +---+ (Root) | | E | | | /IP | | | E | | (Leaf) +---+ 141 | | V | | | | | | V | | 142 | | I | | | | | | I | | +---+ 143 | | | | | | | | +--+----ES3-----+CE3| 144 | +---+ | +------+ | +---+ | (Leaf) +---+ 145 +---------+ +---------+ 147 Figure 1: Scenario 1 149 2.2 Scenario 2: Leaf AND Root site(s) per PE 151 In this scenario, a PE may have a set of one or more Root sites AND a 152 set of one or more Leaf sites for a given VPN instance. Every 153 Ethernet Segment connected to the PE is uniquely identified as either 154 a Root or a Leaf site. 156 +---------+ +---------+ 157 | PE1 | | PE2 | 158 +---+ | +---+ | +------+ | +---+ | +---+ 159 |CE1+-----ES1----+--+ | | | | | | +--+----ES2-----+CE2| 160 +---+ (Leaf) | | E | | | MPLS | | | E | | (Leaf) +---+ 161 | | V | | | /IP | | | V | | 162 | | I | | | | | | I | | +---+ 163 | | | | | | | | +--+----ES3-----+CE3| 164 | +---+ | +------+ | +---+ | (Root) +---+ 165 +---------+ +---------+ 167 Figure 2: Scenario 2 169 2.3 Scenario 3: Leaf AND Root site(s) per Ethernet Segment 171 In this scenario, a PE may have a set of one or more Root sites AND a 172 set of one or more Leaf sites for a given VPN instance. An Ethernet 173 Segment connected to the PE may be identified as both a Root and a 174 Leaf site concurrently. 176 +---------+ +---------+ 177 | PE1 | | PE2 | 178 +---+ | +---+ | +------+ | +---+ | +---+ 179 |CE1+-----ES1----+--+ | | | | | | +--+----ES2-----+CE2| 180 +---+ (Leaf/Root)| | E | | | MPLS | | | E | | (Leaf/Root)+---+ 181 | | V | | | /IP | | | V | | 182 | | I | | | | | | I | | +---+ 183 | | | | | | | | +--+----ES3-----+CE3| 184 | +---+ | +------+ | +---+ | (Leaf) +---+ 185 +---------+ +---------+ 187 Figure 3: Scenario 3 189 3 Operation for EVPN 191 [EVPN] defines the notion of an Ethernet Segment which can be readily 192 used to identify a Root and/or Leaf site in E-TREE services. In other 193 words, [EVPN] has inherent capability to support E-TREE services 194 without defining any new BGP routes. It only requires a minor 195 modification to the existing procedures and a modification to a BGP 196 attribute as shown in this section. 198 The following procedures are used consistently for all the scenarios 199 highlighted in the previous section. 201 3.1 Known Unicast Traffic 203 For known unicast traffic, the PE must advertise a Root/Leaf 204 indication along with each MAC Advertisement route, to indicate 205 whether the associated MAC address was learnt from a Root or a Leaf. 206 This enables remote PEs to perform ingress filtering for known 207 unicast traffic: On the ingress PE, the MAC destination address 208 lookup yields, in addition to the forwarding adjacency, a flag which 209 indicates whether the target MAC is associated with a Root or a Leaf 210 site. The ingress PE cross-checks this flag with the status of the 211 originating site, and if both are a Leaf, then the packet is not 212 forwarded. 214 The PE places all Leaf Ethernet Segments of a given bridge domain in 215 a single split-horizon group in order to prevent intra-PE forwarding 216 among Leaf segments. This split-horizon function applies to BUM 217 traffic as well. 219 To support the above ingress filtering functionality, a new Root/Leaf 220 indication flag will added to the Tunnel Encapsulation Type Extended 221 Community [RFC5512]. This extended community will be advertised with 222 each EVPN MAC Advertisement route. 224 3.2 BUM Traffic 226 For BUM traffic, it is not possible to perform filtering on the 227 ingress PE, as is the case with known unicast, because of the multi- 228 destination nature of the traffic. As such, the solution relies on 229 egress filtering. In order to apply the proper egress filtering, 230 which varies based on whether a packet is sent from a Root or a Leaf, 231 the MPLS-encapsulated frames MUST be tagged with an indication of 232 whether they originated from a Root or a Leaf Ethernet Segment. This 233 can be achieved in EVPN through the use of the ESI MPLS label, since 234 this label identifies the Ethernet Segment of origin of a given 235 frame. The egress PE determines whether or not to forward a 236 particular frame to an Ethernet Segment depending on the split- 237 horizon rule defined in [EVPN]: 239 - If the ESI Label indicates that the source Ethernet Segment is a 240 Root, then the frame can be forwarded on a segment granted that it 241 passes the split-horizon check. 243 - If the ESI Label indicates that the source Ethernet Segment is a 244 Leaf, then the frame can be forwarded only on a Root segment, granted 245 that it passes the split-horizon check. 247 When advertising the ESI MPLS label for a given Ethernet Segment, a 248 PE must indicate whether the corresponding ESI is a Root or a Leaf 249 site. This can be done by encoding the Root or Leaf indication in the 250 Flags field of the ESI MPLS label Extended Community attribute 251 ([EVPN] Section 8) to indicate Root/Leaf status. 253 In the case where a multi-homed Ethernet Segment has both Root and 254 Leaf sites attached, two ESI MPLS labels are allocated and 255 advertised: one ESI MPLS label denotes Root and the other denotes 256 Leaf. The ingress PE imposes the right ESI MPLS label depending on 257 whether the Ethernet frame originated from the Root or Leaf site on 258 that Ethernet Segment. The mechanism by which the PE identifies 259 whether a given frame originated from a Root or Leaf site on the 260 segment is based on the Ethernet Tag associated with the frame. Other 261 mechanisms of identification, beyond the Ethernet Tag, are outside 262 the scope of this document. It should be noted that support for both 263 Root and Leaf sites on a single Ethernet Segment requires that the PE 264 performs the Ethernet Segment split-horizon check on a per Ethernet 265 Tag basis. In the case where a multi-homed Ethernet Segment has 266 either Root or Leaf sites attached, then a single ESI MPL label is 267 allocated and advertised. 269 Furthermore, a PE advertises two special ESI MPLS labels: one for 270 Root and another for Leaf. These are used by remote PEs for traffic 271 originating from single-homed segments and for multi-homed segments 272 that are not connected to the advertising PE. Note that these special 273 labels are advertised on a per PE basis (i.e. each PE advertises only 274 two such special labels). 276 In addition to egress filtering (which is a MUST requirement), an 277 EVPN PE implementation MAY provide topology constraint among the PEs 278 belonging to the same EVI associated with an E-TREE service. The 279 purpose of this topology constraint is to avoid having PEs with only 280 host Leaf sites importing and processing BGP MAC routes from each 281 other, thereby unnecessarily exhausting their RIB tables. However, as 282 soon as a Root site is added to a Leaf PE, then that PE needs to 283 process MAC routes from all other Leaf PEs and add them to its 284 forwarding table. To support such topology constrain in EVPN, two BGP 285 Route-Targets (RTs) are used for every EVPN Instance (EVI): one RT is 286 associated with the Root sites and the other is associated with the 287 Leaf sites. On a per EVI basis, every PE exports the single RT 288 associated with its type of site(s). Furthermore, a PE with Root 289 site(s) imports both Root and Leaf RTs, whereas a PE with Leaf 290 site(s) only imports the Root RT. If for a given EVI, the PEs can 291 eventually have both Leaf and Root sites attached, even though they 292 may start as Root-only or Leaf-only PEs, then it is recommended to 293 use a single RT per EVI and avoid additional configuration and 294 operational overhead. If the number of EVIs is very large (e.g., more 295 than 32K or 64K), then RT type 0 as defined in [RFC4360] SHOULD be 296 used; otherwise, RT type 2 is sufficient. 298 3.3 E-TREE Traffic Flows for EVPN 300 Per [ETREE-FMWK], a generic E-Tree service supports all of the 301 following traffic flows: 303 - Ethernet Unicast from Root to Roots & Leaf 304 - Ethernet Unicast from Leaf to Root 305 - Ethernet Broadcast/Multicast from Root to Roots & Leafs 306 - Ethernet Broadcast/Multicast from Leaf to Roots 308 A particular E-Tree service may need to support all of the above 309 types of flows or only a select subset, depending on the target 310 application. In the case where unicast flows need not be supported, 311 the L2VPN PEs can avoid performing any MAC learning function. 313 In the subsections that follow, we will describe the operation of 314 EVPN to support E-Tree service with and without MAC learning. 316 3.3.1 E-Tree with MAC Learning 318 The PEs implementing an E-Tree service must perform MAC learning when 319 unicast traffic flows must be supported from Root to Leaf or from 320 Leaf to Root sites. In this case, the PE with Root sites performs MAC 321 learning in the data-path over the Ethernet Segments, and advertises 322 reachability in EVPN MAC Advertisement routes. These routes will be 323 imported by PEs that have Leaf sites as well as by PEs that have Root 324 sites, in a given EVI. Similarly, the PEs with Leaf sites perform MAC 325 learning in the data-path over their Ethernet Segments, and advertise 326 reachability in EVPN MAC Advertisement routes which are imported only 327 by PEs with at least one Root site in the EVI. A PE with only Leaf 328 sites will not import these routes. PEs with Root and/or Leaf sites 329 may use the Ethernet A-D routes for aliasing (in the case of multi- 330 homed segments) and for mass MAC withdrawal. 332 To support multicast/broadcast from Root to Leaf sites, either a P2MP 333 tree rooted at the PE(s) with the Root site(s) or ingress replication 334 can be used. The multicast tunnels are set up through the exchange of 335 the EVPN Inclusive Multicast route, as defined in [EVPN]. 337 To support multicast/broadcast from Leaf to Root sites, ingress 338 replication should be sufficient for most scenarios where there is a 339 single Root or few Roots. If the number of Roots is large, a P2MP 340 tree rooted at the PEs with Leaf sites may be used. 342 3.3.2 E-Tree without MAC Learning 344 The PEs implementing an E-Tree service need not perform MAC learning 345 when the traffic flows between Root and Leaf sites are multicast or 346 broadcast. In this case, the PEs do not exchange EVPN MAC 347 Advertisement routes. Instead, the Ethernet A-D routes are used to 348 exchange the EVPN labels. 350 The fields of the Ethernet A-D route are populated per the procedures 351 defined in [EVPN], and the route import rules are as described in 352 previous sections. 354 4 Operation for PBB-EVPN 356 In PBB-EVPN, the PE must advertise a Root/Leaf indication along with 357 each MAC Advertisement route, to indicate whether the associated B- 358 MAC address corresponds to a Root or a Leaf site. Similar to the EVPN 359 case, this flag will be added to the Tunnel Encapsulation Type 360 Extended Community [RFC5512], and advertised with each MAC 361 Advertisement route. 363 In the case where a multi-homed Ethernet Segment has both Root and 364 Leaf sites attached, two B-MAC addresses are allocated and 365 advertised: one B-MAC address denotes Root and the other denotes 366 Leaf. The ingress PE uses the right B-MAC source address depending on 367 whether the Ethernet frame originated from the Root or Leaf site on 368 that Ethernet Segment. The mechanism by which the PE identifies 369 whether a given frame originated from a Root or Leaf site on the 370 segment is based on the Ethernet Tag associated with the frame. Other 371 mechanisms of identification, beyond the Ethernet Tag, are outside 372 the scope of this document. It should be noted that support for both 373 Root and Leaf sites on a single Ethernet Segment requires that the PE 374 performs the Ethernet Segment split-horizon check on a per Ethernet 375 Tag basis. In the case where a multi-homed Ethernet Segment has 376 either Root or Leaf sites attached, then a single B-MAC address is 377 allocated and advertised per segment. 379 Furthermore, a PE advertises two global B-MAC addresses: one for Root 380 and another for Leaf, and tags them as such in the MAC Advertisement 381 routes. These B-MAC addresses are used as source addresses for 382 traffic originating from single-homed segments. 384 4.1 Known Unicast Traffic 386 For known unicast traffic, the PEs perform ingress filtering: On the 387 ingress PE, the C-MAC destination address lookup yields, in addition 388 to the target B-MAC address and forwarding adjacency, a flag which 389 indicates whether the target B-MAC is associated with a Root or a 390 Leaf site. The ingress PE cross-checks this flag with the status of 391 the originating site, and if both are a Leaf, then the packet is not 392 forwarded. 394 The PE places all Leaf Ethernet Segments of a given bridge domain in 395 a single split-horizon group in order to prevent intra-PE forwarding 396 among Leaf segments. This split-horizon function applies to BUM 397 traffic as well. 399 4.2 BUM Traffic 401 For BUM traffic, the PEs must perform egress filtering. When a PE 402 receives a MAC advertisement route, it updates its Ethernet Segment 403 egress filtering function (based on the B-MAC source address), as 404 follows: 406 - If the MAC Advertisement route indicates that the advertised B-MAC 407 is a Leaf, and the local Ethernet Segment is a Leaf as well, then the 408 source B-MAC address is added to the B-MAC filtering list. 410 - Otherwise, the B-MAC filtering list is not updated. 412 When the egress PE receives the packet, it examines the B-MAC source 413 address to check whether it should filter or forward the frame. Note 414 that this uses the same filtering logic as baseline [PBB-EVPN] and 415 does not require any additional flags in the data-plane. 417 5 Acknowledgement 419 We would like to thank Sami Boutros and Dennis Cai for their 420 comments. 422 6 Security Considerations 424 Same security considerations as [EVPN]. 426 7 IANA Considerations 428 Allocation of Extended Community Type and Sub-Type for EVPN. 430 8 References 432 8.1 Normative References 434 [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate 435 Requirement Levels", BCP 14, RFC 2119, March 1997. 437 [RFC4360] S. Sangli et al, ""BGP Extended Communities Attribute", 438 February, 2006. 440 [RFC5512] Mohapatra, P. and E. Rosen, "The BGP 441 Encapsulation Subsequent Address Family Identifier (SAFI) 442 and the BGP Tunnel Encapsulation Attribute", RFC 5512, 443 April 2009. 445 8.2 Informative References 447 [ETREE-FMWK] Key et al., "A Framework for E-Tree Service over MPLS 448 Network", draft-ietf-l2vpn-etree-frwk-03, work in progress, September 449 2013. 451 [EVPN] Sajassi et al., "BGP MPLS Based Ethernet VPN", draft-ietf- 452 l2vpn-evpn-04.txt, work in progress, July, 2013. 454 [PBB-EVPN] Sajassi et al., "PBB-EVPN", draft-ietf-l2vpn-pbb-evpn- 455 05.txt, work in progress, October, 2013. 457 Authors' Addresses 458 Ali Sajassi 459 Cisco 460 Email: sajassi@cisco.com 462 Samer Salam 463 Cisco 464 Email: ssalam@cisco.com 466 Wim Henderickx 467 Alcatel-Lucent 468 Email: wim.henderickx@alcatel-lucent.com 470 Jim Uttaro 471 AT&T 472 Email: ju1738@att.com 474 Aldrin 475 Bloomberg Issac 476 Email: aisaac71@bloomberg.net 478 Sami Boutros 479 Cisco 480 Email: sboutros@cisco.com