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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 6 Wim Henderickx 7 Jorge Rabadan Jim Uttaro 8 Alcatel-Lucent AT&T 10 John Drake Aldrin Isaac 11 Wen Lin Juniper 12 Juniper 14 Expires: April 10, 2016 October 10, 2015 16 E-TREE Support in EVPN & PBB-EVPN 17 draft-ietf-bess-evpn-etree-03 19 Abstract 21 The Metro Ethernet Forum (MEF) has defined a rooted-multipoint 22 Ethernet service known as Ethernet Tree (E-Tree). [ETREE-FMWK] 23 proposes a solution framework for supporting this service in MPLS 24 networks. This document discusses how those functional requirements 25 can be easily met with (PBB-)EVPN and how (PBB-)EVPN offers a more 26 efficient implementation of these functions. 28 Status of this Memo 30 This Internet-Draft is submitted to IETF in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF), its areas, and its working groups. Note that 35 other groups may also distribute working documents as 36 Internet-Drafts. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 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/1id-abstracts.html 46 The list of Internet-Draft Shadow Directories can be accessed at 47 http://www.ietf.org/shadow.html 49 Copyright and License Notice 51 Copyright (c) 2013 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (http://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Table of Contents 66 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 67 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 68 2 E-Tree Scenarios and EVPN / PBB-EVPN Support . . . . . . . . . 4 69 2.1 Scenario 1: Leaf OR Root site(s) per PE . . . . . . . . . . 4 70 2.2 Scenario 2: Leaf OR Root site(s) per AC . . . . . . . . . . 5 71 2.3 Scenario 3: Leaf OR Root site(s) per MAC . . . . . . . . . . 6 72 3 Operation for EVPN . . . . . . . . . . . . . . . . . . . . . . . 7 73 3.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 7 74 3.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 8 75 3.2.1 BUM traffic originated from a single-homed site on a 76 leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 9 77 3.2.2 BUM traffic originated from a single-homed site on a 78 root AC . . . . . . . . . . . . . . . . . . . . . . . . 9 79 3.2.3 BUM traffic originated from a multi-homed site on a 80 leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 9 81 3.2.4 BUM traffic originated from a multi-homed site on a 82 root AC . . . . . . . . . . . . . . . . . . . . . . . . 9 83 3.3 E-TREE Traffic Flows for EVPN . . . . . . . . . . . . . . . 10 84 3.3.1 E-Tree with MAC Learning . . . . . . . . . . . . . . . . 10 85 3.3.2 E-Tree without MAC Learning . . . . . . . . . . . . . . 11 86 4 Operation for PBB-EVPN . . . . . . . . . . . . . . . . . . . . . 11 87 4.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 12 88 4.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 12 89 5 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 13 90 5.1 E-TREE Extended Community . . . . . . . . . . . . . . . . . 13 91 5.2 PMSI Tunnel Attribute . . . . . . . . . . . . . . . . . . . 14 93 6 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 14 94 7 Security Considerations . . . . . . . . . . . . . . . . . . . . 14 95 8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 14 96 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 97 9.1 Normative References . . . . . . . . . . . . . . . . . . . 15 98 9.2 Informative References . . . . . . . . . . . . . . . . . . 15 99 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 101 1 Introduction 103 The Metro Ethernet Forum (MEF) has defined a rooted-multipoint 104 Ethernet service known as Ethernet Tree (E-Tree). In an E-Tree 105 service, endpoints are labeled as either Root or Leaf sites. Root 106 sites can communicate with all other sites. Leaf sites can 107 communicate with Root sites but not with other Leaf sites. 109 [ETREE-FMWK] proposes the solution framework for supporting E-Tree 110 service in MPLS networks. The document identifies the functional 111 components of the overall solution to emulate E-Tree services in 112 addition to Ethernet LAN (E-LAN) services on an existing MPLS 113 network. 115 [EVPN] is a solution for multipoint L2VPN services, with advanced 116 multi-homing capabilities, using BGP for distributing customer/client 117 MAC address reach-ability information over the MPLS/IP network. [PBB- 118 EVPN] combines the functionality of EVPN with [802.1ah] Provider 119 Backbone Bridging for MAC address scalability. 121 This document discusses how the functional requirements for E-Tree 122 service can be easily met with (PBB-)EVPN and how (PBB-)EVPN offers a 123 more efficient implementation of these functions. 125 1.1 Terminology 127 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 128 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 129 document are to be interpreted as described in RFC 2119 [KEYWORDS]. 131 2 E-Tree Scenarios and EVPN / PBB-EVPN Support 133 In this section, we will categorize support for E-Tree into three 134 different scenarios, depending on the nature of the site association 135 (Root/Leaf) per PE or per Ethernet Segment: 137 - Leaf OR Root site(s) per PE 139 - Leaf OR Root site(s) per AC 141 - Leaf OR Root site(s) per MAC 143 2.1 Scenario 1: Leaf OR Root site(s) per PE 145 In this scenario, a PE may receive traffic from either Root sites OR 146 Leaf sites for a given MAC-VRF/bridge table, but not both 147 concurrently. In other words, a given EVI on a PE is either 148 associated with a root or leaf. The PE may have both Root and Leaf 149 sites albeit for different EVIs. 151 +---------+ +---------+ 152 | PE1 | | PE2 | 153 +---+ | +---+ | +------+ | +---+ | +---+ 154 |CE1+---ES1----+--+ | | | MPLS | | | +--+----ES2-----+CE2| 155 +---+ (Root) | |MAC| | | /IP | | |MAC| | (Leaf) +---+ 156 | |VRF| | | | | |VRF| | 157 | | | | | | | | | | +---+ 158 | | | | | | | | +--+----ES3-----+CE3| 159 | +---+ | +------+ | +---+ | (Leaf) +---+ 160 +---------+ +---------+ 162 Figure 1: Scenario 1 164 In such scenario, an EVPN PE implementation MAY provide E-TREE 165 service using topology constraint among the PEs belonging to the same 166 EVI. The purpose of this topology constraint is to avoid having PEs 167 with only Leaf sites importing and processing BGP MAC routes from 168 each other. To support such topology constrain in EVPN, two BGP 169 Route-Targets (RTs) are used for every EVPN Instance (EVI): one RT is 170 associated with the Root sites and the other is associated with the 171 Leaf sites. On a per EVI basis, every PE exports the single RT 172 associated with its type of site(s). Furthermore, a PE with Root 173 site(s) imports both Root and Leaf RTs, whereas a PE with Leaf 174 site(s) only imports the Root RT. If the number of EVIs is very large 175 (e.g., more than 32K or 64K), then RT type 0 as defined in [RFC4360] 176 SHOULD be used; otherwise, RT type 2 is sufficient. 178 2.2 Scenario 2: Leaf OR Root site(s) per AC 180 In this scenario, a PE receives traffic from either Root OR Leaf 181 sites (but not both) on a given Attachment Circuit (AC) of an EVI. In 182 other words, an AC (ES or ES/VLAN) is either associated with a Root 183 or Leaf (but not both). 185 +---------+ +---------+ 186 | PE1 | | PE2 | 187 +---+ | +---+ | +------+ | +---+ | +---+ 188 |CE1+-----ES1----+--+ | | | | | | +--+---ES2/AC1--+CE2| 189 +---+ (Leaf) | |MAC| | | MPLS | | |MAC| | (Leaf) +---+ 190 | |VRF| | | /IP | | |VRF| | 191 | | | | | | | | | | +---+ 192 | | | | | | | | +--+---ES2/AC2--+CE3| 193 | +---+ | +------+ | +---+ | (Root) +---+ 194 +---------+ +---------+ 196 Figure 2: Scenario 2 198 In this scenario, if there are PEs with only root (or leaf) sites per 199 EVI, then the RT constrain procedures described in section 2.1 can 200 also be used here. However, when a Root site is added to a Leaf PE, 201 then that PE needs to process MAC routes from all other Leaf PEs and 202 add them to its forwarding table. For this scenario, if for a given 203 EVI, the majority of PEs will eventually have both Leaf and Root 204 sites attached, even though they may start as Root-only or Leaf-only 205 PEs, then it is recommended to use a single RT per EVI and avoid 206 additional configuration and operational overhead. 208 2.3 Scenario 3: Leaf OR Root site(s) per MAC 210 In this scenario, a PE may receive traffic from both Root AND Leaf 211 sites on a given Attachment Circuit (AC) of an EVI. Since an 212 Attachment Circuit (ES or ES/VLAN) carries traffic from both Root and 213 Leaf sites, the granularity at which Root or Leaf sites are 214 identifies is on a per MAC address. This scenario is considered in 215 this draft for EVPN service with only known unicast traffic - i.e., 216 there is no BUM traffic. 218 +---------+ +---------+ 219 | PE1 | | PE2 | 220 +---+ | +---+ | +------+ | +---+ | +---+ 221 |CE1+-----ES1----+--+ | | | | | | +--+---ES2/AC1--+CE2| 222 +---+ (Root) | | E | | | MPLS | | | E | | (Leaf/Root)+---+ 223 | | V | | | /IP | | | V | | 224 | | I | | | | | | I | | +---+ 225 | | | | | | | | +--+---ES2/AC2--+CE3| 226 | +---+ | +------+ | +---+ | (Leaf) +---+ 227 +---------+ +---------+ 229 Figure 3: Scenario 3 231 3 Operation for EVPN 233 [EVPN] defines the notion of ESI MPLS label used for split-horizon 234 filtering of BUM traffic at the egress PE. Such egress filtering 235 capabilities can be leveraged in provision of E-TREE services as seen 236 shortly. In other words, [EVPN] has inherent capability to support E- 237 TREE services without defining any new BGP routes but by just 238 defining a new BGP Extended Community for leaf indication as shown 239 later in this document. 241 3.1 Known Unicast Traffic 243 Since in EVPN, MAC learning is performed in control plane via 244 advertisement of BGP routes, the filtering needed by E-TREE service 245 for known unicast traffic can be performed at the ingress PE, thus 246 providing very efficient filtering and avoiding sending known unicast 247 traffic over MPLS/IP core to be filtered at the egress PE as done in 248 traditional E-TREE solutions (e.g., E-TREE for VPLS). 250 To provide such ingress filtering for known unicast traffic, a PE 251 MUST indicate to other PEs what kind of sites (root or leaf) its MAC 252 addresses are associated with by advertising a leaf indication flag 253 (via an Extended Community) along with each of its MAC/IP 254 Advertisement route. The lack of such flag indicates that the MAC 255 address is associated with a root site. This scheme applies to all 256 scenarios described in section 2. 258 Furthermore, for multi-homing scenario of section 2.2, where an AC is 259 either root or leaf (but not both), the PE MAY advertise leaf 260 indication along with the Ethernet A-D per EVI route. This 261 advertisement is used for sanity checking in control-plane to ensure 262 that there is no discrepancy in configuration among different PEs of 263 the same redundancy group. For example, if a leaf site is multi-homed 264 to PE1 an PE2, and PE1 advertises the Ethernet A-D per EVI 265 corresponding to this leaf site with the leaf-indication flag but PE2 266 does not, then the receiving PE notifies the operator of such 267 discrepancy and ignore the leaf-indication flag on PE1. In other 268 words, in case of discrepancy, the multi-homing for that pair of PEs 269 is assumed to be in default "root" mode for that or . The leaf indication flag on Ethernet A-D per EVI route 271 tells the receiving PEs that all MAC addresses associated with this 272 or are from a leaf site. Therefore, if a 273 PE receives a leaf indication for an AC via the Ethernet A-D per EVI 274 route but doesn't receive a leaf indication in the corresponding MAC 275 route, then it notify the operator and ignore the leaf indication on 276 the Ethernet A-D per EVI route. 278 Tagging MAC addresses with a leaf indication enables remote PEs to 279 perform ingress filtering for known unicast traffic - i.e., on the 280 ingress PE, the MAC destination address lookup yields, in addition to 281 the forwarding adjacency, a flag which indicates whether the target 282 MAC is associated with a Leaf site or not. The ingress PE cross- 283 checks this flag with the status of the originating AC, and if both 284 are Leafs, then the packet is not forwarded. 286 To support the above ingress filtering functionality, a new E-TREE 287 Extended Community with a Leaf indication flag is introduced [section 288 5.2]. This new Extended Community MUST be advertised with MAC/IP 289 Advertisement route and MAY be advertised with an Ethernet A-D per 290 EVI route as described above. 292 3.2 BUM Traffic 294 For BUM traffic, it is not possible to perform filtering on the 295 ingress PE, as is the case with known unicast, because of the multi- 296 destination nature of the traffic. As such, the solution relies on 297 egress filtering. In order to apply the proper egress filtering, 298 which varies based on whether a packet is sent from a Leaf AC or a 299 root AC, the MPLS-encapsulated frames MUST be tagged with an 300 indication of whether they originated from a Leaf AC or not. In other 301 words, leaf/root indication for BUM traffic is done at the 302 granularity of AC. This can be achieved in EVPN through the use of 303 the ESI MPLS label. Therefore, the ESI MPLS label can be used to 304 either identify the Ethernet segment of origin per [RFC 7432] or it 305 can be used to indicate that the packet is originated from a leaf 306 site. 308 BUM traffic sent over a P2MP LSP or ingress replication, may need to 309 carry an upstream assigned or downstream assigned MPLS label 310 (respectively) for the purpose of egress filtering to indicate to the 311 egress PEs whether this packet is originated from a root AC or a leaf 312 AC. 314 The main difference between downstream and upstream assigned ESI MPLS 315 label is that in case of downstream assigned not all egress PE 316 devices need to receive the ESI label just like ingress replication 317 procedures defined in [RFC7432]. 319 There are four scenarios to consider as follow. In all these 320 scenarios, the imposition PE imposes the right ESI MPLS label 321 depending on whether the Ethernet frame originated from a Root or a 322 Leaf site on that Ethernet Segment. The mechanism by which the PE 323 identifies whether a given frame originated from a Root or a Leaf 324 site on the segment is based on the Ethernet Tag associated with the 325 frame (e.g., whether the frame received on a leaf or a root AC). 327 Other mechanisms for identifying whether an egress AC is a root or 328 leaf is beyond the scope of this document. 330 3.2.1 BUM traffic originated from a single-homed site on a leaf AC 332 In this scenario, the ingress PE adds a special MPLS label indicating 333 a Leaf site. This special Leaf MPLS label, used for single-homing 334 scenarios, is not on a per ES basis but rather on a per PE basis - 335 i.e., a single Leaf MPLS label is used for all single-homed ES's on 336 that PE. This Leaf MPLS label is advertised to other PE devices, 337 using a new EVPN Extended Community called E-TREE Extended Community 338 (section 5.1) along with an Ethernet A-D per ES route with ESI of 339 zero and a set of Route Targets (RTs) corresponding to all the leaf 340 ACs on the PE. The set of Ethernet A-D per ES routes may be needed if 341 the number of Route Targets (RTs) that need to be sent exceed the 342 limit on a single route per [RFC 7432]. The RT(s) represent EVIs with 343 at least a leaf site in them. The ESI for the Ethernet A-D per ES 344 route is set to zero to indicate single-homed sites. 346 When a PE receives this special ESI MPLS label in the data path, it 347 blocks the packet if the destination AC is of type Leaf; otherwise, 348 it forwards the packet. 350 3.2.2 BUM traffic originated from a single-homed site on a root AC 352 In this scenario, the ingress PE does not add any ESI or Leaf MPLS 353 label and it operates per [RFC7432] procedures. 355 3.2.3 BUM traffic originated from a multi-homed site on a leaf AC 357 In this scenario, it is assumed that a multi-homed Ethernet Segment 358 (ES) can have a mixed of both leaf and root ACs with each AC 359 designating a subnet (e.g., a VLAN). Furthermore, it is assumed that 360 there is no forwarding among subnets - ie, the service is EVPN L2 and 361 not EVPN IRB. IRB use case is for further study. 363 In such scenarios, If a multicast packet is originated from a leaf 364 AC, then it only needs to carry Leaf MPLS label described in section 365 3.2.1. This label is sufficient in providing the necessary egress 366 filtering of BUM traffic from getting sent to leaf ACs including the 367 leaf AC on the same Ethernet Segment. 369 3.2.4 BUM traffic originated from a multi-homed site on a root AC 371 In this scenario, both the ingress and egress PE devices follows the 372 procedure defined in [RFC 7432] for adding and/or processing an ESI 373 MPLS label. 375 3.3 E-TREE Traffic Flows for EVPN 377 Per [ETREE-FMWK], a generic E-Tree service supports all of the 378 following traffic flows: 380 - Ethernet Unicast from Root to Roots & Leaf 381 - Ethernet Unicast from Leaf to Root 382 - Ethernet Broadcast/Multicast from Root to Roots & Leafs 383 - Ethernet Broadcast/Multicast from Leaf to Roots 385 A particular E-Tree service may need to support all of the above 386 types of flows or only a select subset, depending on the target 387 application. In the case where unicast flows need not be supported, 388 the L2VPN PEs can avoid performing any MAC learning function. 390 In the subsections that follow, we will describe the operation of 391 EVPN to support E-Tree service with and without MAC learning. 393 3.3.1 E-Tree with MAC Learning 395 The PEs implementing an E-Tree service must perform MAC learning when 396 unicast traffic flows must be supported among Root and Leaf sites. In 397 this case, the PE with Root sites performs MAC learning in the data- 398 path over the Ethernet Segments, and advertises reachability in EVPN 399 MAC Advertisement routes. These routes will be imported by PEs that 400 have Leaf sites as well as by PEs that have Root sites, in a given 401 EVI. Similarly, the PEs with Leaf sites perform MAC learning in the 402 data-path over their Ethernet Segments, and advertise reachability in 403 EVPN MAC Advertisement routes which are imported only by PEs with at 404 least one Root site in the EVI. A PE with only Leaf sites will not 405 import these routes. PEs with Root and/or Leaf sites may use the 406 Ethernet A-D routes for aliasing (in the case of multi-homed 407 segments) and for mass MAC withdrawal per [RFC 7432]. 409 To support multicast/broadcast from Root to Leaf sites, either a P2MP 410 tree rooted at the PE(s) with the Root site(s) or ingress replication 411 can be used. The multicast tunnels are set up through the exchange of 412 the EVPN Inclusive Multicast route, as defined in [RFC7432]. 414 To support multicast/broadcast from Leaf to Root sites, ingress 415 replication should be sufficient for most scenarios where there are 416 only a few Roots (typically two). Therefore, in a typical scenario, a 417 root PE needs to support both a P2MP tunnel in transmit direction 418 from itself to leaf PEs and at the same time it needs to support 419 ingress-replication tunnels in receive direction from leaf PEs to 420 itself. In order to signal this efficiently from the root PE, a new 421 composite tunnel type is defined per section 5.3. This new composite 422 tunnel type is advertised by the root PE to simultaneously indicate a 423 P2MP tunnel in transmit direction and an ingress-replication tunnel 424 in the receive direction for the BUM traffic. 426 If the number of Roots is large, P2MP tunnels originated at the PEs 427 with Leaf sites may be used and thus there will be no need to use the 428 modified PMSI tunnel attribute in section 5.2 for composite tunnel 429 type. 431 3.3.2 E-Tree without MAC Learning 433 The PEs implementing an E-Tree service need not perform MAC learning 434 when the traffic flows between Root and Leaf sites are multicast or 435 broadcast. In this case, the PEs do not exchange EVPN MAC 436 Advertisement routes. Instead, the Inclusive Multicast Ethernet Tag 437 (IMET) routes are used to support BUM traffic. 439 The fields of the IMET route are populated per the procedures defined 440 in [RFC7432], and the route import rules are as described in previous 441 sections. 443 Just as in the previous section, if the number of PEs with root sites 444 are only a few and thus ingress replication is desired from leaf PEs 445 to these root PEs, then the modified PMSI attribute as defined in 446 section 5.3 should be used. 448 4 Operation for PBB-EVPN 450 In PBB-EVPN, the PE must advertise a Root/Leaf indication along with 451 each B-MAC Advertisement route, to indicate whether the associated B- 452 MAC address corresponds to a Root or a Leaf site. Similar to the EVPN 453 case, this flag will be added to the new E-TREE Extended Community 454 defined in section [5.2], and advertised with each MAC Advertisement 455 route. 457 In the case where a multi-homed Ethernet Segment has both Root and 458 Leaf sites attached, two B-MAC addresses are allocated and 459 advertised: one B-MAC address implicitly denoting Root and the other 460 explicitly denoting Leaf. The former B-MAC address is not advertised 461 with the E-TREE extended community but the latter B-MAC denoting Leaf 462 is advertised with the new E-TREE extended community. 464 The ingress PE uses the right B-MAC source address depending on 465 whether the Ethernet frame originated from the Root or Leaf site on 466 that Ethernet Segment. The mechanism by which the PE identifies 467 whether a given frame originated from a Root or Leaf site on the 468 segment is based on the Ethernet Tag associated with the frame. Other 469 mechanisms of identification, beyond the Ethernet Tag, are outside 470 the scope of this document. It should be noted that support for both 471 Root and Leaf sites on a single Ethernet Segment requires that the PE 472 performs the Ethernet Segment split-horizon check on a per Ethernet 473 Tag basis. 475 In the case where a multi-homed Ethernet Segment has only Root OR 476 Leaf sites attached, then a single B-MAC address is allocated and 477 advertised per segment. 479 Furthermore, a PE advertises two special global B-MAC addresses: one 480 for Root and another for Leaf, and tags the Leaf one as such in the 481 MAC Advertisement route. These B-MAC addresses are used as source 482 addresses for traffic originating from single-homed segments. 484 4.1 Known Unicast Traffic 486 For known unicast traffic, the PEs perform ingress filtering: On the 487 ingress PE, the C-MAC destination address lookup yields, in addition 488 to the target B-MAC address and forwarding adjacency, a flag which 489 indicates whether the target B-MAC is associated with a Root or a 490 Leaf site. The ingress PE cross-checks this flag with the status of 491 the originating site, and if both are a Leaf, then the packet is not 492 forwarded. 494 4.2 BUM Traffic 496 For BUM traffic, the PEs must perform egress filtering. When a PE 497 receives a MAC advertisement route, it updates its Ethernet Segment 498 egress filtering function (based on the B-MAC source address), as 499 follows: 501 - If the MAC Advertisement route indicates that the advertised B-MAC 502 is a Leaf, and the local Ethernet Segment is a Leaf as well, then the 503 source B-MAC address is added to the B-MAC filtering list. 505 - Otherwise, the B-MAC filtering list is not updated. 507 When the egress PE receives the packet, it examines the B-MAC source 508 address to check whether it should filter or forward the frame. Note 509 that this uses the same filtering logic as baseline [PBB-EVPN] and 510 does not require any additional flags in the data-plane. 512 The PE places all Leaf Ethernet Segments of a given bridge domain in 513 a single split-horizon group in order to prevent intra-PE forwarding 514 among Leaf segments. This split-horizon function applies to BUM 515 traffic. 517 5 BGP Encoding 519 This document defines two new BGP Extended Community for EVPN. 521 5.1 E-TREE Extended Community 523 This Extended Community is a new transitive Extended Community having 524 a Type field value of 0x06 (EVPN) and the Sub-Type 0x05. It is used 525 for leaf indication of known unicast and BUM traffic. For BUM 526 traffic, the Leaf Label field is set to a valid MPLS label and this 527 EC is advertised along with Ethernet A-D per ES route with an ESI of 528 zero to enable egress filtering on disposition PEs per section 3.2.1 529 and 3.2.3. For known unicast traffic, the Leaf flag bit is set to one 530 and this EC is advertised along with MAC/IP Advertisement route per 531 section 3.1. 533 The E-TREE Extended Community is encoded as an 8-octet value as 534 follows: 536 0 1 2 3 537 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 1 538 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 539 | Type=0x06 | Sub-Type=0x04 | Flags(1 Octet)| | 540 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 541 | Reserved=0 | Leaf Label | 542 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 544 The low-order bit of the Flags octet is defined as the "Leaf- 545 Indication" bit. A value of one indicates a Leaf AC/Site. 547 When this EC is advertised along with MAC/IP Advertisement route, the 548 Leaf-Indication flag MUST be set to one and Leaf Label is set to 549 zero. The received PE should ignore Leaf Label and only processes 550 Leaf-Indication flag. A value of zero for Leaf-Indication flag is 551 invalid when sent along with MAC/IP advertisement route and an error 552 should be logged. 554 When this EC is advertised along with Ethernet A-D per ES route (with 555 ESI of zero), the Leaf Label MUST be set to a valid MPLS label and 556 the Leaf-Indication flag should be set to zero. The received PE 557 should ignore the Leaf-Indication flag. A non-valid MPLS label when 558 sent along with the Ethernet A-D per ES route, should be logged as an 559 error. 561 5.2 PMSI Tunnel Attribute 563 [RFC 6514] defines PMSI Tunnel attribute which is an optional 564 transitive attribute with the following format: 566 +---------------------------------+ 567 | Flags (1 octet) | 568 +---------------------------------+ 569 | Tunnel Type (1 octets) | 570 +---------------------------------+ 571 | MPLS Label (3 octets) | 572 +---------------------------------+ 573 | Tunnel Identifier (variable) | 574 +---------------------------------+ 576 This draft uses all the fields per existing definition except for the 577 following modifications to the Tunnel Type and Tunnel Identifier: 579 When receiver ingress-replication label is needed, the high-order bit 580 of the tunnel type field (C bit - Composite tunnel bit) is set while 581 the remaining low-order seven bits indicate the tunnel type as 582 before. When this C bit is set, the "tunnel identifier" field would 583 begin with a three-octet label, followed by the actual tunnel 584 identifier for the transmit tunnel. PEs that don't understand the 585 new meaning of the high-order bit would treat the tunnel type as an 586 invalid tunnel type. For the PEs that do understand the new meaning 587 of the high-order, if ingress replication is desired when sending BUM 588 traffic, the PE will use the the label in the Tunnel Identifier field 589 when sending its BUM traffic. 591 6 Acknowledgement 593 We would like to thank Dennis Cai, Antoni Przygienda, and Jeffrey 594 Zhang for their valueable comments. 596 7 Security Considerations 598 Same security considerations as [RFC7432]. 600 8 IANA Considerations 602 Allocation of Extended Community Type and Sub-Type for EVPN. 604 9 References 605 9.1 Normative References 607 [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate 608 Requirement Levels", BCP 14, RFC 2119, March 1997. 610 [RFC4360] S. Sangli et al, ""BGP Extended Communities Attribute", 611 February, 2006. 613 [RFC7432] Sajassi et al., "BGP MPLS Based Ethernet VPN", February, 614 2015. 616 9.2 Informative References 618 [ETREE-FMWK] Key et al., "A Framework for E-Tree Service over MPLS 619 Network", draft-ietf-l2vpn-etree-frwk-03, work in progress, September 620 2013. 622 [PBB-EVPN] Sajassi et al., "PBB-EVPN", draft-ietf-l2vpn-pbb-evpn- 623 05.txt, work in progress, October, 2013. 625 Authors' Addresses 627 Ali Sajassi 628 Cisco 629 Email: sajassi@cisco.com 631 Samer Salam 632 Cisco 633 Email: ssalam@cisco.com 635 Wim Henderickx 636 Alcatel-Lucent 637 Email: wim.henderickx@alcatel-lucent.com 639 Jim Uttaro 640 AT&T 641 Email: ju1738@att.com 643 Aldrin 644 Bloomberg Issac 645 Email: aisaac71@bloomberg.net 647 Sami Boutros 648 Cisco 649 Email: sboutros@cisco.com