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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 BESS Workgroup A. Sajassi, Ed. 3 INTERNET-DRAFT S. Salam 4 Intended Status: Standards Track Cisco 5 Updates: RFC7385 J. Drake 6 Juniper 7 J. Uttaro 8 ATT 9 S. Boutros 10 VMware 11 J. Rabadan 12 Nokia 14 Expires: March 1, 2017 September 1, 2016 16 E-TREE Support in EVPN & PBB-EVPN 17 draft-ietf-bess-evpn-etree-07 19 Abstract 21 The Metro Ethernet Forum (MEF) has defined a rooted-multipoint 22 Ethernet service known as Ethernet Tree (E-Tree). A solution 23 framework for supporting this service in MPLS networks is proposed in 24 and RFC called "A Framework for E-Tree Service over MPLS Network". 25 This document discusses how those functional requirements can be 26 easily met with (PBB-)EVPN and how (PBB-)EVPN offers a more efficient 27 implementation of these functions. This document makes use of the 28 most significant bit of the scope governed by the IANA registry 29 created by RFC7385, and hence updates that RFC accordingly. 31 Status of this Memo 33 This Internet-Draft is submitted to IETF in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF), its areas, and its working groups. Note that 38 other groups may also distribute working documents as 39 Internet-Drafts. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 The list of current Internet-Drafts can be accessed at 47 http://www.ietf.org/1id-abstracts.html 49 The list of Internet-Draft Shadow Directories can be accessed at 50 http://www.ietf.org/shadow.html 52 Copyright and License Notice 54 Copyright (c) 2016 IETF Trust and the persons identified as the 55 document authors. All rights reserved. 57 This document is subject to BCP 78 and the IETF Trust's Legal 58 Provisions Relating to IETF Documents 59 (http://trustee.ietf.org/license-info) in effect on the date of 60 publication of this document. Please review these documents 61 carefully, as they describe your rights and restrictions with respect 62 to this document. Code Components extracted from this document must 63 include Simplified BSD License text as described in Section 4.e of 64 the Trust Legal Provisions and are provided without warranty as 65 described in the Simplified BSD License. 67 Table of Contents 69 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 70 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 71 2 E-Tree Scenarios and EVPN / PBB-EVPN Support . . . . . . . . . 4 72 2.1 Scenario 1: Leaf OR Root site(s) per PE . . . . . . . . . . 4 73 2.2 Scenario 2: Leaf OR Root site(s) per AC . . . . . . . . . . 5 74 2.3 Scenario 3: Leaf OR Root site(s) per MAC . . . . . . . . . . 6 75 3 Operation for EVPN . . . . . . . . . . . . . . . . . . . . . . . 7 76 3.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 7 77 3.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 8 78 3.2.1 BUM traffic originated from a single-homed site on a 79 leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 9 80 3.2.2 BUM traffic originated from a single-homed site on a 81 root AC . . . . . . . . . . . . . . . . . . . . . . . . 9 82 3.2.3 BUM traffic originated from a multi-homed site on a 83 leaf AC . . . . . . . . . . . . . . . . . . . . . . . . 9 84 3.2.4 BUM traffic originated from a multi-homed site on a 85 root AC . . . . . . . . . . . . . . . . . . . . . . . . 10 86 3.3 E-TREE Traffic Flows for EVPN . . . . . . . . . . . . . . . 10 87 3.3.1 E-Tree with MAC Learning . . . . . . . . . . . . . . . . 10 88 3.3.2 E-Tree without MAC Learning . . . . . . . . . . . . . . 11 89 4 Operation for PBB-EVPN . . . . . . . . . . . . . . . . . . . . . 11 90 4.1 Known Unicast Traffic . . . . . . . . . . . . . . . . . . . 12 91 4.2 BUM Traffic . . . . . . . . . . . . . . . . . . . . . . . . 12 92 4.3 E-Tree without MAC Learning . . . . . . . . . . . . . . . . 13 93 5 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 13 94 5.1 E-TREE Extended Community . . . . . . . . . . . . . . . . . 13 95 5.2 PMSI Tunnel Attribute . . . . . . . . . . . . . . . . . . . 14 96 6 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 15 97 7 Security Considerations . . . . . . . . . . . . . . . . . . . . 15 98 8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 15 99 8.1 Considerations for PMSI Tunnel Types . . . . . . . . . . . . 15 100 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 101 9.1 Normative References . . . . . . . . . . . . . . . . . . . 16 102 9.2 Informative References . . . . . . . . . . . . . . . . . . 16 103 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 104 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 106 1 Introduction 108 The Metro Ethernet Forum (MEF) has defined a rooted-multipoint 109 Ethernet service known as Ethernet Tree (E-Tree). In an E-Tree 110 service, endpoints are labeled as either Root or Leaf sites. Root 111 sites can communicate with all other sites. Leaf sites can 112 communicate with Root sites but not with other Leaf sites. 114 [RFC7387] proposes the solution framework for supporting E-Tree 115 service in MPLS networks. The document identifies the functional 116 components of the overall solution to emulate E-Tree services in 117 addition to Ethernet LAN (E-LAN) services on an existing MPLS 118 network. 120 [RFC7432] is a solution for multipoint L2VPN services, with advanced 121 multi-homing capabilities, using BGP for distributing customer/client 122 MAC address reach-ability information over the MPLS/IP network. 123 [RFC7623] combines the functionality of EVPN with [802.1ah] Provider 124 Backbone Bridging for MAC address scalability. 126 This document discusses how the functional requirements for E-Tree 127 service can be easily met with (PBB-)EVPN and how (PBB-)EVPN offers a 128 more efficient implementation of these functions. 130 1.1 Terminology 132 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 133 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 134 document are to be interpreted as described in RFC 2119 [KEYWORDS]. 136 2 E-Tree Scenarios and EVPN / PBB-EVPN Support 138 In this section, we will categorize support for E-Tree into three 139 different scenarios, depending on the nature of the site association 140 (Root/Leaf) per PE or per Ethernet Segment: 142 - Leaf OR Root site(s) per PE 144 - Leaf OR Root site(s) per AC 146 - Leaf OR Root site(s) per MAC 148 2.1 Scenario 1: Leaf OR Root site(s) per PE 150 In this scenario, a PE may receive traffic from either Root sites OR 151 Leaf sites for a given MAC-VRF/bridge table, but not both 152 concurrently. In other words, a given EVI on a PE is either 153 associated with root(s) or leaf(s). The PE may have both Root and 154 Leaf sites albeit for different EVIs. 156 +---------+ +---------+ 157 | PE1 | | PE2 | 158 +---+ | +---+ | +------+ | +---+ | +---+ 159 |CE1+---ES1----+--+ | | | MPLS | | | +--+----ES2-----+CE2| 160 +---+ (Root) | |MAC| | | /IP | | |MAC| | (Leaf) +---+ 161 | |VRF| | | | | |VRF| | 162 | | | | | | | | | | +---+ 163 | | | | | | | | +--+----ES3-----+CE3| 164 | +---+ | +------+ | +---+ | (Leaf) +---+ 165 +---------+ +---------+ 167 Figure 1: Scenario 1 169 In such scenario, topology constraint, provided by BGP Route Target 170 (RT) import/export policies among the PEs belonging to the same EVI, 171 can be used to restrict the communications among Leaf PEs. The 172 purpose of this topology constraint is to avoid having PEs with only 173 Leaf sites importing and processing BGP MAC routes from each other. 174 To support such topology constrain in EVPN, two BGP Route-Targets 175 (RTs) are used for every EVPN Instance (EVI): one RT is associated 176 with the Root sites and the other is associated with the Leaf sites. 177 On a per EVI basis, every PE exports the single RT associated with 178 its type of site(s). Furthermore, a PE with Root site(s) imports both 179 Root and Leaf RTs, whereas a PE with Leaf site(s) only imports the 180 Root RT. 182 2.2 Scenario 2: Leaf OR Root site(s) per AC 184 In this scenario, a PE receives traffic from either Root OR Leaf 185 sites (but not both) on a given Attachment Circuit (AC) of an EVI. In 186 other words, an AC (ES or ES/VLAN) is either associated with Root(s) 187 or Leaf(s) (but not both). 189 +---------+ +---------+ 190 | PE1 | | PE2 | 191 +---+ | +---+ | +------+ | +---+ | +---+ 192 |CE1+-----ES1----+--+ | | | | | | +--+---ES2/AC1--+CE2| 193 +---+ (Leaf) | |MAC| | | MPLS | | |MAC| | (Leaf) +---+ 194 | |VRF| | | /IP | | |VRF| | 195 | | | | | | | | | | +---+ 196 | | | | | | | | +--+---ES2/AC2--+CE3| 197 | +---+ | +------+ | +---+ | (Root) +---+ 198 +---------+ +---------+ 200 Figure 2: Scenario 2 202 In this scenario, if there are PEs with only root (or leaf) sites per 203 EVI, then the RT constrain procedures described in section 2.1 can 204 also be used here. However, when a Root site is added to a Leaf PE, 205 then that PE needs to process MAC routes from all other Leaf PEs and 206 add them to its forwarding table. For this scenario, if for a given 207 EVI, the vast majority of PEs will eventually have both Leaf and Root 208 sites attached, even though they may start as Root-only or Leaf-only 209 PEs, then it is recommended to use a single RT per EVI and avoid 210 additional configuration and operational overhead. 212 2.3 Scenario 3: Leaf OR Root site(s) per MAC 214 In this scenario, a PE may receive traffic from both Root AND Leaf 215 sites on a single Attachment Circuit (AC) of an EVI. Since an 216 Attachment Circuit (ES or ES/VLAN) carries traffic from both Root and 217 Leaf sites, the granularity at which Root or Leaf sites are 218 identified is on a per MAC address. This scenario is considered in 219 this draft for EVPN service with only known unicast traffic - i.e., 220 BUM traffic is not supported in this scenario and it is dropped . 222 +---------+ +---------+ 223 | PE1 | | PE2 | 224 +---+ | +---+ | +------+ | +---+ | +---+ 225 |CE1+-----ES1----+--+ | | | | | | +--+---ES2/AC1--+CE2| 226 +---+ (Root) | | E | | | MPLS | | | E | | (Leaf/Root)+---+ 227 | | V | | | /IP | | | V | | 228 | | I | | | | | | I | | +---+ 229 | | | | | | | | +--+---ES2/AC2--+CE3| 230 | +---+ | +------+ | +---+ | (Leaf) +---+ 231 +---------+ +---------+ 233 Figure 3: Scenario 3 235 3 Operation for EVPN 237 [RFC7432] defines the notion of ESI MPLS label used for split-horizon 238 filtering of BUM traffic at the egress PE. Such egress filtering 239 capabilities can be leveraged in provision of E-TREE services as seen 240 shortly. In other words, [RFC7432] has inherent capability to support 241 E-TREE services without defining any new BGP routes but by just 242 defining a new BGP Extended Community for leaf indication as shown 243 later in this document. 245 3.1 Known Unicast Traffic 247 Since in EVPN, MAC learning is performed in control plane via 248 advertisement of BGP routes, the filtering needed by E-TREE service 249 for known unicast traffic can be performed at the ingress PE, thus 250 providing very efficient filtering and avoiding sending known unicast 251 traffic over MPLS/IP core to be filtered at the egress PE as done in 252 traditional E-TREE solutions (e.g., E-TREE for VPLS). 254 To provide such ingress filtering for known unicast traffic, a PE 255 MUST indicate to other PEs what kind of sites (root or leaf) its MAC 256 addresses are associated with by advertising a leaf indication flag 257 (via an Extended Community) along with each of its MAC/IP 258 Advertisement route. The lack of such flag indicates that the MAC 259 address is associated with a root site. This scheme applies to all 260 scenarios described in section 2. 262 Furthermore, for multi-homing scenario of section 2.2, where an AC is 263 either root or leaf (but not both), the PE MAY advertise leaf 264 indication along with the Ethernet A-D per EVI route. This 265 advertisement is used for sanity checking in control-plane to ensure 266 that there is no discrepancy in configuration among different PEs of 267 the same redundancy group. For example, if a leaf site is multi-homed 268 to PE1 an PE2, and PE1 advertises the Ethernet A-D per EVI 269 corresponding to this leaf site with the leaf-indication flag but PE2 270 does not, then the receiving PE notifies the operator of such 271 discrepancy and ignore the leaf-indication flag on PE1. In other 272 words, in case of discrepancy, the multi-homing for that pair of PEs 273 is assumed to be in default "root" mode for that or . The leaf indication flag on Ethernet A-D per EVI route 275 tells the receiving PEs that all MAC addresses associated with this 276 or are from a leaf site. Therefore, if a 277 PE receives a leaf indication for an AC via the Ethernet A-D per EVI 278 route but doesn't receive a leaf indication in the corresponding 279 MAC/IP Advertisement route, then it notifies the operator and ignore 280 the leaf indication on the Ethernet A-D per EVI route. 282 Tagging MAC addresses with a leaf indication enables remote PEs to 283 perform ingress filtering for known unicast traffic - i.e., on the 284 ingress PE, the MAC destination address lookup yields, in addition to 285 the forwarding adjacency, a flag which indicates whether the target 286 MAC is associated with a Leaf site or not. The ingress PE cross- 287 checks this flag with the status of the originating AC, and if both 288 are Leafs, then the packet is not forwarded. 290 In situation where MAC moves are allowed among Leaf and Root sites 291 (e.g., non-static MAC), PEs can receive multiple MAC/IP 292 advertisements routes for the same MAC address with different 293 Leaf/Root indications (and possibly different ESIs for multi-homing 294 scenarios). In such situations, MAC mobility procedures take 295 precedence to first identify the location of the MAC before 296 associating that MAC with a Root or a Leaf site. 298 To support the above ingress filtering functionality, a new E-TREE 299 Extended Community with a Leaf indication flag is introduced [section 300 5.2]. This new Extended Community MUST be advertised with MAC/IP 301 Advertisement route and MAY be advertised with an Ethernet A-D per 302 EVI route as described above. 304 3.2 BUM Traffic 306 This specification does not provide support for filtering BUM traffic 307 on the ingress PE because it is not possible to perform filtering of 308 BUM traffic on the ingress PE, as is the case with known unicast 309 described above, due to the multi-destination nature of BUM traffic. 310 As such, the solution relies on egress filtering. In order to apply 311 the proper egress filtering, which varies based on whether a packet 312 is sent from a Leaf AC or a root AC, the MPLS-encapsulated frames 313 MUST be tagged with an indication when they originated from a Leaf 314 AC. In other words, leaf indication for BUM traffic is done at the 315 granularity of AC. This can be achieved in EVPN through the use of a 316 MPLS label where it can be used to either identify the Ethernet 317 segment of origin per [RFC7432] (i.e., ESI label) or it can be used 318 to indicate that the packet is originated from a leaf site (Leaf 319 label). 321 BUM traffic sent over a P2MP LSP or ingress replication, may need to 322 carry an upstream assigned or downstream assigned MPLS label 323 (respectively) for the purpose of egress filtering to indicate to the 324 egress PEs whether this packet is originated from a leaf AC. 326 The main difference between downstream and upstream assigned MPLS 327 label is that in case of downstream assigned not all egress PE 328 devices need to receive the label just like ingress replication 329 procedures defined in [RFC7432]. 331 The PE places all Leaf Ethernet Segments of a given bridge domain in 332 a single split-horizon group in order to prevent intra-PE forwarding 333 among Leaf segments. This split-horizon function applies to BUM 334 traffic as well as known-unicast traffic. 336 There are four scenarios to consider as follows. In all these 337 scenarios, the ingress PE imposes the right MPLS label associated 338 with the originated Ethernet Segment (ES) depending on whether the 339 Ethernet frame originated from a Root or a Leaf site on that Ethernet 340 Segment (ESI or Leaf label). The mechanism by which the PE identifies 341 whether a given frame originated from a Root or a Leaf site on the 342 segment is based on the AC identifier for that segment (e.g., 343 Ethernet Tag of the frame for 802.1Q frames). Other mechanisms for 344 identifying root or leaf (e.g., on a per MAC address basis) is beyond 345 the scope of this document. 347 3.2.1 BUM traffic originated from a single-homed site on a leaf AC 349 In this scenario, the ingress PE adds a special MPLS label indicating 350 a Leaf site. This special Leaf MPLS label, used for single-homing 351 scenarios, is not on a per ES basis but rather on a per PE basis - 352 i.e., a single Leaf MPLS label is used for all single-homed ES's on 353 that PE. This Leaf label is advertised to other PE devices, using a 354 new EVPN Extended Community called E-TREE Extended Community (section 355 5.1) along with an Ethernet A-D per ES route with ESI of zero and a 356 set of Route Targets (RTs) corresponding to all EVIs on the PE with 357 at least one leaf site per EVI. The set of Ethernet A-D per ES routes 358 may be needed if the number of Route Targets (RTs) that need to be 359 sent exceed the limit on a single route per [RFC7432]. The ESI for 360 the Ethernet A-D per ES route is set to zero to indicate single-homed 361 sites. 363 When a PE receives this special Leaf label in the data path, it 364 blocks the packet if the destination AC is of type Leaf; otherwise, 365 it forwards the packet. 367 3.2.2 BUM traffic originated from a single-homed site on a root AC 369 In this scenario, the ingress PE does not add any ESI or Leaf label 370 and it operates per [RFC7432] procedures. 372 3.2.3 BUM traffic originated from a multi-homed site on a leaf AC 374 In this scenario, it is assumed that while different ACs (VLANs) on 375 the same ES could have different root/leaf designation (some being 376 roots and some being leafs), the same AC (e.g., VLAN) does have the 377 same root/leaf designation on all PEs on the same ES. Furthermore, it 378 is assumed that there is no forwarding among subnets - ie, the 379 service is EVPN L2 and not EVPN IRB. IRB use case is outside the 380 scope of this document. 382 In such scenarios, If a multicast or broadcast packet is originated 383 from a leaf AC, then it only needs to carry Leaf label described in 384 section 3.2.1. This label is sufficient in providing the necessary 385 egress filtering of BUM traffic from getting sent to leaf ACs 386 including the leaf AC on the same Ethernet Segment. 388 3.2.4 BUM traffic originated from a multi-homed site on a root AC 390 In this scenario, both the ingress and egress PE devices follows the 391 procedure defined in [RFC7432] for adding and/or processing an ESI 392 MPLS label. 394 3.3 E-TREE Traffic Flows for EVPN 396 Per [RFC7387], a generic E-Tree service supports all of the following 397 traffic flows: 399 - Ethernet Unicast from Root to Roots & Leaf 400 - Ethernet Unicast from Leaf to Root 401 - Ethernet Broadcast/Multicast from Root to Roots & Leafs 402 - Ethernet Broadcast/Multicast from Leaf to Roots 404 A particular E-Tree service may need to support all of the above 405 types of flows or only a select subset, depending on the target 406 application. In the case where unicast flows need not be supported, 407 the L2VPN PEs can avoid performing any MAC learning function. 409 In the subsections that follow, we will describe the operation of 410 EVPN to support E-Tree service with and without MAC learning. 412 3.3.1 E-Tree with MAC Learning 414 The PEs implementing an E-Tree service must perform MAC learning when 415 unicast traffic flows must be supported among Root and Leaf sites. In 416 this case, the PE(s) with Root sites performs MAC learning in the 417 data-path over the Ethernet Segments, and advertises reachability in 418 EVPN MAC Advertisement routes. These routes will be imported by all 419 PEs for that EVI (i.e., PEs that have Leaf sites as well as PEs that 420 have Root sites). Similarly, the PEs with Leaf sites perform MAC 421 learning in the data-path over their Ethernet Segments, and advertise 422 reachability in EVPN MAC Advertisement routes. For the scenario 423 described in section 2.1 (or possibly section 2.2), these routes are 424 imported only by PEs with at least one Root site in the EVI - i.e., a 425 PE with only Leaf sites will not import these routes. PEs with Root 426 and/or Leaf sites may use the Ethernet A-D routes for aliasing (in 427 the case of multi-homed segments) and for mass MAC withdrawal per 428 [RFC7432]. 430 To support multicast/broadcast from Root to Leaf sites, either a P2MP 431 tree rooted at the PE(s) with the Root site(s) or ingress replication 432 can be used. The multicast tunnels are set up through the exchange of 433 the EVPN Inclusive Multicast route, as defined in [RFC7432]. 435 To support multicast/broadcast from Leaf to Root sites, ingress 436 replication should be sufficient for most scenarios where there are 437 only a few Roots (typically two). Therefore, in a typical scenario, a 438 root PE needs to support both a P2MP tunnel in transmit direction 439 from itself to leaf PEs and at the same time it needs to support 440 ingress-replication tunnels in receive direction from leaf PEs to 441 itself. In order to signal this efficiently from the root PE, a new 442 composite tunnel type is defined per section 5.3. This new composite 443 tunnel type is advertised by the root PE to simultaneously indicate a 444 P2MP tunnel in transmit direction and an ingress-replication tunnel 445 in the receive direction for the BUM traffic. 447 If the number of Roots is large, P2MP tunnels originated at the PEs 448 with Leaf sites may be used and thus there will be no need to use the 449 modified PMSI tunnel attribute in section 5.2 for composite tunnel 450 type. 452 3.3.2 E-Tree without MAC Learning 454 The PEs implementing an E-Tree service need not perform MAC learning 455 when the traffic flows between Root and Leaf sites are only multicast 456 or broadcast. In this case, the PEs do not exchange EVPN MAC 457 Advertisement routes. Instead, the Inclusive Multicast Ethernet Tag 458 route is used to support BUM traffic. 460 The fields of this route are populated per the procedures defined in 461 [RFC7432], and the multicast tunnel setup criteria are as described 462 in the previous section. 464 Just as in the previous section, if the number of PEs with root sites 465 are only a few and thus ingress replication is desired from leaf PEs 466 to these root PEs, then the modified PMSI attribute as defined in 467 section 5.3 should be used. 469 4 Operation for PBB-EVPN 471 In PBB-EVPN, the PE advertises a Root/Leaf indication along with each 472 B-MAC Advertisement route, to indicate whether the associated B-MAC 473 address corresponds to a Root or a Leaf site. Just like the EVPN 474 case, the new E-TREE Extended Community defined in section [5.1] is 475 advertised with each MAC Advertisement route. 477 In the case where a multi-homed Ethernet Segment has both Root and 478 Leaf sites attached, two B-MAC addresses are advertised: one B-MAC 479 address is per ES as specified in [RFC7623] and implicitly denoting 480 Root, and the other B-MAC address is per PE and explicitly denoting 481 Leaf. The former B-MAC address is not advertised with the E-TREE 482 extended community but the latter B-MAC denoting Leaf is advertised 483 with the new E-TREE extended community where "Leaf-indication" flag 484 is set. In such multi-homing scenarios where and Ethernet Segment has 485 both Root and Leaf ACs, it is assumed that While different ACs 486 (VLANs) on the same ES could have different root/leaf designation 487 (some being roots and some being leafs), the same VLAN does have the 488 same root/leaf designation on all PEs on the same ES. Furthermore, it 489 is assumed that there is no forwarding among subnets - ie, the 490 service is L2 and not IRB. IRB use case is outside the scope of this 491 document. 493 The ingress PE uses the right B-MAC source address depending on 494 whether the Ethernet frame originated from the Root or Leaf AC on 495 that Ethernet Segment. The mechanism by which the PE identifies 496 whether a given frame originated from a Root or Leaf site on the 497 segment is based on the Ethernet Tag associated with the frame. Other 498 mechanisms of identification, beyond the Ethernet Tag, are outside 499 the scope of this document. 501 Furthermore, a PE advertises two special global B-MAC addresses: one 502 for Root and another for Leaf, and tags the Leaf one as such in the 503 MAC Advertisement route. These B-MAC addresses are used as source 504 addresses for traffic originating from single-homed segments. The B- 505 MAC address used for indicating Leaf sites can be the same for both 506 single-homed and multi-homed segments. 508 4.1 Known Unicast Traffic 510 For known unicast traffic, the PEs perform ingress filtering: On the 511 ingress PE, the C-MAC destination address lookup yields, in addition 512 to the target B-MAC address and forwarding adjacency, a flag which 513 indicates whether the target B-MAC is associated with a Root or a 514 Leaf site. The ingress PE cross-checks this flag with the status of 515 the originating site, and if both are a Leaf, then the packet is not 516 forwarded. 518 4.2 BUM Traffic 519 For BUM traffic, the PEs must perform egress filtering. When a PE 520 receives a MAC advertisement route (which will be used as a source B- 521 MAC for BUM traffic), it updates its egress filtering (based on the 522 source B-MAC address), as follows: 524 - If the MAC Advertisement route indicates that the advertised B-MAC 525 is a Leaf, and the local Ethernet Segment is a Leaf as well, then the 526 source B-MAC address is added to its B-MAC list used for egress 527 filtering. 529 - Otherwise, the B-MAC filtering list is not updated. 531 When the egress PE receives the packet, it examines the B-MAC source 532 address to check whether it should filter or forward the frame. Note 533 that this uses the same filtering logic as baseline [RFC7623] and 534 does not require any additional flags in the data-plane. 536 Just as in section 3.2, the PE places all Leaf Ethernet Segments of a 537 given bridge domain in a single split-horizon group in order to 538 prevent intra-PE forwarding among Leaf segments. This split-horizon 539 function applies to BUM traffic as well as known-unicast traffic. 541 4.3 E-Tree without MAC Learning 543 In scenarios where the traffic of interest is only Multicast and/or 544 broadcast, the PEs implementing an E-Tree service do not need to do 545 any MAC learning. In such scenarios the filtering must be performed 546 on egress PEs. For PBB-EVPN, the handling of such traffic is per 547 section 4.2 without C-MAC learning part of it at both ingress and 548 egress PEs. 550 5 BGP Encoding 552 This document defines two new BGP Extended Community for EVPN. 554 5.1 E-TREE Extended Community 556 This Extended Community is a new transitive Extended Community having 557 a Type field value of 0x06 (EVPN) and the Sub-Type 0x05. It is used 558 for leaf indication of known unicast and BUM traffic. For BUM 559 traffic, the Leaf Label field is set to a valid MPLS label and this 560 EC is advertised along with Ethernet A-D per ES route with an ESI of 561 zero to enable egress filtering on disposition PEs per section 3.2.1 562 and 3.2.3. There is no need to send ESI Label Extended Community when 563 sending Ethernet A-D per ES route with an ESI of zero. For known 564 unicast traffic, the Leaf flag bit is set to one and this EC is 565 advertised along with MAC/IP Advertisement route per section 3.1. 567 The E-TREE Extended Community is encoded as an 8-octet value as 568 follows: 570 0 1 2 3 571 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 1 572 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 573 | Type=0x06 | Sub-Type=0x05 | Flags(1 Octet)| Reserved=0 | 574 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 575 | Reserved=0 | Leaf Label | 576 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 578 The low-order bit of the Flags octet is defined as the "Leaf- 579 Indication" bit. A value of one indicates a Leaf AC/Site. 581 When this EC is advertised along with MAC/IP Advertisement route (for 582 known unicast traffic), the Leaf-Indication flag MUST be set to one 583 and Leaf Label is set to zero. The received PE should ignore Leaf 584 Label and only processes Leaf-Indication flag. A value of zero for 585 Leaf-Indication flag is invalid when sent along with MAC/IP 586 advertisement route and an error should be logged. 588 When this EC is advertised along with Ethernet A-D per ES route (with 589 ESI of zero) for BUM traffic, the Leaf Label MUST be set to a valid 590 MPLS label and the Leaf-Indication flag should be set to zero. The 591 received PE should ignore the Leaf-Indication flag. A non-valid MPLS 592 label when sent along with the Ethernet A-D per ES route, should be 593 logged as an error. 595 5.2 PMSI Tunnel Attribute 597 [RFC6514] defines PMSI Tunnel attribute which is an optional 598 transitive attribute with the following format: 600 +---------------------------------+ 601 | Flags (1 octet) | 602 +---------------------------------+ 603 | Tunnel Type (1 octets) | 604 +---------------------------------+ 605 | MPLS Label (3 octets) | 606 +---------------------------------+ 607 | Tunnel Identifier (variable) | 608 +---------------------------------+ 610 This draft uses all the fields per existing definition except for the 611 following modifications to the Tunnel Type and Tunnel Identifier: 613 When receiver ingress-replication label is needed, the high-order bit 614 of the tunnel type field (C bit - Composite tunnel bit) is set while 615 the remaining low-order seven bits indicate the tunnel type as 616 before. When this C bit is set, the "tunnel identifier" field would 617 begin with a three-octet label, followed by the actual tunnel 618 identifier for the transmit tunnel. PEs that don't understand the 619 new meaning of the high-order bit would treat the tunnel type as an 620 invalid tunnel type. For the PEs that do understand the new meaning 621 of the high-order, if ingress replication is desired when sending BUM 622 traffic, the PE will use the the label in the Tunnel Identifier field 623 when sending its BUM traffic. 625 Using the Composite flag for Tunnel Types 0x00 'no tunnel information 626 present' and 0x06 'Ingress Replication' is invalid, and should be 627 treated as an invalid tunnel type on reception. 629 6 Acknowledgement 631 We would like to thank Dennis Cai, Antoni Przygienda, and Jeffrey 632 Zhang for their valuable comments. 634 7 Security Considerations 636 Since this draft uses the EVPN constructs of [RFC7432] and [RFC7623], 637 the same security considerations in these drafts are also applicable 638 here. Furthermore, this draft provides additional security check by 639 allowing sites (or ACs) of an EVPN instance to be designated as 640 "Root" or "Leaf" and preventing any traffic exchange among "Leaf" 641 sites of that VPN through ingress filtering for known unicast traffic 642 and egress filtering for BUM traffic. 644 8 IANA Considerations 646 IANA has allocated value 5 in the "EVPN Extended Community Sub-Types" 647 registry defined in [RFC7153] as follow: 649 SUB-TYPE VALUE NAME Reference 651 0x05 E-TREE Extended Community This document 653 8.1 Considerations for PMSI Tunnel Types 654 The "P-Multicast Service Interface Tunnel (PMSI Tunnel) Tunnel Types" 655 registry in the "Border Gateway Protocol (BGP) Parameters" registry 656 needs to be updated to reflect the use of the most significant bit to 657 advertise the use of "composite tunnels" (section 5.2). 659 For this purpose, this document updates RFC7385. 661 The registry is to be updated, by removing the entries for 0xFB-0xFE 662 and 0x0F, and replacing them by: - 0x7B-0x7E Reserved for 663 Experimental Use [this document]- 0x7F Reserved [this document]- 664 0x80-0xFF Not Allocatable, corresponds to Composite tunnel types 665 [this document] 667 The allocation policy for values 0x00 to 0x7A is IETF Review 668 [RFC5226]. The range for experimental use is now 0x7B-0x7E, and value 669 in this range are not to be assigned. The status of 0x7F may only be 670 changed through Standards Action [RFC5226]. 672 9 References 674 9.1 Normative References 676 [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate 677 Requirement Levels", BCP 14, RFC 2119, March 1997. 679 [RFC7432] Sajassi et al., "BGP MPLS Based Ethernet VPN", February, 680 2015. 682 [RFC7623] Sajassi et al., "Provider Backbone Bridging Combined with 683 Ethernet VPN (PBB-EVPN)", September, 2015. 685 [RFC7385] Andersson et al., "IANA Registry for P-Multicast 686 Service Interface (PMSI) Tunnel Type Code Points", 687 October, 2014. 689 [RFC7153] Rosen et al., "IANA Registries for BGP Extended 690 Communities", March, 2014. 692 [RFC6514] Aggarwal et al., "BGP Encodings and Procedures 693 for Multicast in MPLS/BGP IP VPNs", February, 2012. 695 9.2 Informative References 697 [RFC7387] Key et al., "A Framework for E-Tree Service over MPLS 698 Network", October 2014. 700 [RFC4360] S. Sangli et al, "BGP Extended Communities Attribute", 701 February, 2006. 703 Contributors 705 In addition to the authors listed on the front page, the following 706 co-authors have also contributed to this document: 708 Wim Henderickx 709 Nokia 711 Aldrin Isaac 712 Wen Lin 713 Juniper 715 Authors' Addresses 717 Ali Sajassi 718 Cisco 719 Email: sajassi@cisco.com 721 Samer Salam 722 Cisco 723 Email: ssalam@cisco.com 725 John Drake 726 Juniper 727 Email: jdrake@juniper.net 729 Jim Uttaro 730 AT&T 731 Email: ju1738@att.com 733 Sami Boutros 734 VMware 735 Email: sboutros@vmware.com 737 Jorge Rabadan 738 Nokia 739 Email: jorge.rabadan@nokia.com