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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 1 comment (--). 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: November 10, 2016 May 10, 2016 16 E-TREE Support in EVPN & PBB-EVPN 17 draft-ietf-bess-evpn-etree-05 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. 29 Status of this Memo 31 This Internet-Draft is submitted to IETF in full conformance with the 32 provisions of BCP 78 and BCP 79. 34 Internet-Drafts are working documents of the Internet Engineering 35 Task Force (IETF), its areas, and its working groups. Note that 36 other groups may also distribute working documents as 37 Internet-Drafts. 39 Internet-Drafts are draft documents valid for a maximum of six months 40 and may be updated, replaced, or obsoleted by other documents at any 41 time. It is inappropriate to use Internet-Drafts as reference 42 material or to cite them other than as "work in progress." 44 The list of current Internet-Drafts can be accessed at 45 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) 2016 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 4.3 E-Tree without MAC Learning . . . . . . . . . . . . . . . . 13 90 5 BGP Encoding . . . . . . . . . . . . . . . . . . . . . . . . . . 13 91 5.1 E-TREE Extended Community . . . . . . . . . . . . . . . . . 13 92 5.2 PMSI Tunnel Attribute . . . . . . . . . . . . . . . . . . . 14 93 6 Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . . 15 94 7 Security Considerations . . . . . . . . . . . . . . . . . . . . 15 95 8 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 15 96 9 References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 97 9.1 Normative References . . . . . . . . . . . . . . . . . . . 15 98 9.2 Informative References . . . . . . . . . . . . . . . . . . 15 99 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 101 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 [RFC7387] 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 [RFC7432] 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. 118 [RFC7623] 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 64K), then RT type 0 as defined in [RFC4360] SHOULD 176 be used; otherwise, RT type 2 is sufficient [RFC7153]. 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 [RFC7432] 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, [RFC7432] has inherent capability to support 237 E-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 when they originated from a Leaf AC. In other words, leaf 301 indication for BUM traffic is done at the granularity of AC. This can 302 be achieved in EVPN through the use of a MPLS label where it can be 303 used to either identify the Ethernet segment of origin per [RFC7432] 304 (i.e., ESI label) or it can be used to indicate that the packet is 305 originated from a leaf site (Leaf label). 307 BUM traffic sent over a P2MP LSP or ingress replication, may need to 308 carry an upstream assigned or downstream assigned MPLS label 309 (respectively) for the purpose of egress filtering to indicate to the 310 egress PEs whether this packet is originated from a leaf AC. 312 The main difference between downstream and upstream assigned MPLS 313 label is that in case of downstream assigned not all egress PE 314 devices need to receive the label just like ingress replication 315 procedures defined in [RFC7432]. 317 There are four scenarios to consider as follow. In all these 318 scenarios, the imposition PE imposes the right MPLS label associated 319 with the originated Ethernet Segment (ES) depending on whether the 320 Ethernet frame originated from a Root or a Leaf site on that Ethernet 321 Segment (ESI or Leaf label). The mechanism by which the PE identifies 322 whether a given frame originated from a Root or a Leaf site on the 323 segment is based on the Ethernet Tag associated with the frame (e.g., 324 whether the frame received on a leaf or a root AC). Other mechanisms 325 for identifying whether an ingress AC is a root or leaf is beyond the 326 scope of this document. 328 3.2.1 BUM traffic originated from a single-homed site on a leaf AC 330 In this scenario, the ingress PE adds a special MPLS label indicating 331 a Leaf site. This special Leaf MPLS label, used for single-homing 332 scenarios, is not on a per ES basis but rather on a per PE basis - 333 i.e., a single Leaf MPLS label is used for all single-homed ES's on 334 that PE. This Leaf label is advertised to other PE devices, using a 335 new EVPN Extended Community called E-TREE Extended Community (section 336 5.1) along with an Ethernet A-D per ES route with ESI of zero and a 337 set of Route Targets (RTs) corresponding to all EVIs on the PE with 338 at least one leaf site per EVI. The set of Ethernet A-D per ES routes 339 may be needed if the number of Route Targets (RTs) that need to be 340 sent exceed the limit on a single route per [RFC7432]. The ESI for 341 the Ethernet A-D per ES route is set to zero to indicate single-homed 342 sites. 344 When a PE receives this special Leaf label in the data path, it 345 blocks the packet if the destination AC is of type Leaf; otherwise, 346 it forwards the packet. 348 3.2.2 BUM traffic originated from a single-homed site on a root AC 350 In this scenario, the ingress PE does not add any ESI or Leaf label 351 and it operates per [RFC7432] procedures. 353 3.2.3 BUM traffic originated from a multi-homed site on a leaf AC 355 In this scenario, it is assumed that While different ACs (VLANs) on 356 the same ES could have different root/leaf designation (some being 357 roots and some being leaves), the same VLAN does have the same 358 root/leaf designation on all PEs on the same ES. Furthermore, it is 359 assumed that there is no forwarding among subnets - ie, the service 360 is EVPN L2 and not EVPN IRB. IRB use case is outside the scope of 361 this document. 363 In such scenarios, If a multicast packet is originated from a leaf 364 AC, then it only needs to carry Leaf 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 [RFC7432] for adding and/or processing an ESI 373 MPLS label. 375 3.3 E-TREE Traffic Flows for EVPN 377 Per [RFC7387], a generic E-Tree service supports all of the following 378 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 all PEs 400 for that EVI (i.e., PEs that have Leaf sites as well as PEs that have 401 Root sites). Similarly, the PEs with Leaf sites perform MAC learning 402 in the data-path over their Ethernet Segments, and advertise 403 reachability in EVPN MAC Advertisement routes. For the scenario 404 described in section 2.1 (or possibly section 2.2), these routes are 405 imported only by PEs with at least one Root site in the EVI - i.e., a 406 PE with only Leaf sites will not import these routes. PEs with Root 407 and/or Leaf sites may use the Ethernet A-D routes for aliasing (in 408 the case of multi-homed segments) and for mass MAC withdrawal per 409 [RFC7432]. 411 To support multicast/broadcast from Root to Leaf sites, either a P2MP 412 tree rooted at the PE(s) with the Root site(s) or ingress replication 413 can be used. The multicast tunnels are set up through the exchange of 414 the EVPN Inclusive Multicast route, as defined in [RFC7432]. 416 To support multicast/broadcast from Leaf to Root sites, ingress 417 replication should be sufficient for most scenarios where there are 418 only a few Roots (typically two). Therefore, in a typical scenario, a 419 root PE needs to support both a P2MP tunnel in transmit direction 420 from itself to leaf PEs and at the same time it needs to support 421 ingress-replication tunnels in receive direction from leaf PEs to 422 itself. In order to signal this efficiently from the root PE, a new 423 composite tunnel type is defined per section 5.3. This new composite 424 tunnel type is advertised by the root PE to simultaneously indicate a 425 P2MP tunnel in transmit direction and an ingress-replication tunnel 426 in the receive direction for the BUM traffic. 428 If the number of Roots is large, P2MP tunnels originated at the PEs 429 with Leaf sites may be used and thus there will be no need to use the 430 modified PMSI tunnel attribute in section 5.2 for composite tunnel 431 type. 433 3.3.2 E-Tree without MAC Learning 435 The PEs implementing an E-Tree service need not perform MAC learning 436 when the traffic flows between Root and Leaf sites are only multicast 437 or broadcast. In this case, the PEs do not exchange EVPN MAC 438 Advertisement routes. Instead, the Inclusive Multicast Ethernet Tag 439 (IMET) routes are used to support BUM traffic. 441 The fields of the IMET route are populated per the procedures defined 442 in [RFC7432], and the multicast tunnel setup criteria are as 443 described in the previous section. 445 Just as in the previous section, if the number of PEs with root sites 446 are only a few and thus ingress replication is desired from leaf PEs 447 to these root PEs, then the modified PMSI attribute as defined in 448 section 5.3 should be used. 450 4 Operation for PBB-EVPN 452 In PBB-EVPN, the PE advertises a Root/Leaf indication along with each 453 B-MAC Advertisement route, to indicate whether the associated B-MAC 454 address corresponds to a Root or a Leaf site. Just like the EVPN 455 case, the new E-TREE Extended Community defined in section [5.1] is 456 advertised with each MAC Advertisement route. 458 In the case where a multi-homed Ethernet Segment has both Root and 459 Leaf sites attached, two B-MAC addresses are advertised: one B-MAC 460 address is per ES as specified in [RFC7623] and implicitly denoting 461 Root, and the other B-MAC address is per PE and explicitly denoting 462 Leaf. The former B-MAC address is not advertised with the E-TREE 463 extended community but the latter B-MAC denoting Leaf is advertised 464 with the new E-TREE extended community where "Leaf-indication" flag 465 is set. In such multi-homing scenarios where and Ethernet Segment has 466 both Root and Leaf ACs, it is assumed that While different ACs 467 (VLANs) on the same ES could have different root/leaf designation 468 (some being roots and some being leaves), the same VLAN does have the 469 same root/leaf designation on all PEs on the same ES. Furthermore, it 470 is assumed that there is no forwarding among subnets - ie, the 471 service is L2 and not IRB. IRB use case is outside the scope of this 472 document. 474 The ingress PE uses the right B-MAC source address depending on 475 whether the Ethernet frame originated from the Root or Leaf AC on 476 that Ethernet Segment. The mechanism by which the PE identifies 477 whether a given frame originated from a Root or Leaf site on the 478 segment is based on the Ethernet Tag associated with the frame. Other 479 mechanisms of identification, beyond the Ethernet Tag, are outside 480 the scope of this document. 482 Furthermore, a PE advertises two special global B-MAC addresses: one 483 for Root and another for Leaf, and tags the Leaf one as such in the 484 MAC Advertisement route. These B-MAC addresses are used as source 485 addresses for traffic originating from single-homed segments. The B- 486 MAC address used for indicating Leaf sites can be the same for both 487 single-homed and multi-homed segments. 489 4.1 Known Unicast Traffic 491 For known unicast traffic, the PEs perform ingress filtering: On the 492 ingress PE, the C-MAC destination address lookup yields, in addition 493 to the target B-MAC address and forwarding adjacency, a flag which 494 indicates whether the target B-MAC is associated with a Root or a 495 Leaf site. The ingress PE cross-checks this flag with the status of 496 the originating site, and if both are a Leaf, then the packet is not 497 forwarded. 499 4.2 BUM Traffic 501 For BUM traffic, the PEs must perform egress filtering. When a PE 502 receives a MAC advertisement route (which will be used as a source B- 503 MAC), it updates its Ethernet Segment egress filtering function 504 (based on the source B-MAC address), as follows: 506 - If the MAC Advertisement route indicates that the advertised B-MAC 507 is a Leaf, and the local Ethernet Segment is a Leaf as well, then the 508 source B-MAC address is added to the B-MAC filtering list. 510 - Otherwise, the B-MAC filtering list is not updated. 512 When the egress PE receives the packet, it examines the B-MAC source 513 address to check whether it should filter or forward the frame. Note 514 that this uses the same filtering logic as baseline [RFC7623] and 515 does not require any additional flags in the data-plane. 517 The PE places all Leaf Ethernet Segments of a given bridge domain in 518 a single split-horizon group in order to prevent intra-PE forwarding 519 among Leaf segments. This split-horizon function applies to BUM 520 traffic. 522 4.3 E-Tree without MAC Learning 524 In scenarios where the traffic of interest is only Multicast and/or 525 broadcast, the PEs implementing an E-Tree service do not need to do 526 any MAC learning. In such scenarios the filtering must be performed 527 on egress PEs. For PBB-EVPN, the handling of such traffic is per 528 section 4.2 without C-MAC learning part of it at both ingress and 529 egress PEs. 531 5 BGP Encoding 533 This document defines two new BGP Extended Community for EVPN. 535 5.1 E-TREE Extended Community 537 This Extended Community is a new transitive Extended Community having 538 a Type field value of 0x06 (EVPN) and the Sub-Type 0x05. It is used 539 for leaf indication of known unicast and BUM traffic. For BUM 540 traffic, the Leaf Label field is set to a valid MPLS label and this 541 EC is advertised along with Ethernet A-D per ES route with an ESI of 542 zero to enable egress filtering on disposition PEs per section 3.2.1 543 and 3.2.3. There is no need to send ESI Label Extended Community when 544 sending Ethernet A-D per ES route with an ESI of zero. For known 545 unicast traffic, the Leaf flag bit is set to one and this EC is 546 advertised along with MAC/IP Advertisement route per section 3.1. 548 The E-TREE Extended Community is encoded as an 8-octet value as 549 follows: 551 0 1 2 3 552 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 1 553 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 554 | Type=0x06 | Sub-Type=0x05 | Flags(1 Octet)| Reserved=0 | 555 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 556 | Reserved=0 | Leaf Label | 557 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 559 The low-order bit of the Flags octet is defined as the "Leaf- 560 Indication" bit. A value of one indicates a Leaf AC/Site. 562 When this EC is advertised along with MAC/IP Advertisement route (for 563 known unicast traffic), the Leaf-Indication flag MUST be set to one 564 and Leaf Label is set to zero. The received PE should ignore Leaf 565 Label and only processes Leaf-Indication flag. A value of zero for 566 Leaf-Indication flag is invalid when sent along with MAC/IP 567 advertisement route and an error should be logged. 569 When this EC is advertised along with Ethernet A-D per ES route (with 570 ESI of zero) for BUM traffic, the Leaf Label MUST be set to a valid 571 MPLS label and the Leaf-Indication flag should be set to zero. The 572 received PE should ignore the Leaf-Indication flag. A non-valid MPLS 573 label when sent along with the Ethernet A-D per ES route, should be 574 logged as an error. 576 5.2 PMSI Tunnel Attribute 578 [RFC6514] defines PMSI Tunnel attribute which is an optional 579 transitive attribute with the following format: 581 +---------------------------------+ 582 | Flags (1 octet) | 583 +---------------------------------+ 584 | Tunnel Type (1 octets) | 585 +---------------------------------+ 586 | MPLS Label (3 octets) | 587 +---------------------------------+ 588 | Tunnel Identifier (variable) | 589 +---------------------------------+ 591 This draft uses all the fields per existing definition except for the 592 following modifications to the Tunnel Type and Tunnel Identifier: 594 When receiver ingress-replication label is needed, the high-order bit 595 of the tunnel type field (C bit - Composite tunnel bit) is set while 596 the remaining low-order seven bits indicate the tunnel type as 597 before. When this C bit is set, the "tunnel identifier" field would 598 begin with a three-octet label, followed by the actual tunnel 599 identifier for the transmit tunnel. PEs that don't understand the 600 new meaning of the high-order bit would treat the tunnel type as an 601 invalid tunnel type. For the PEs that do understand the new meaning 602 of the high-order, if ingress replication is desired when sending BUM 603 traffic, the PE will use the the label in the Tunnel Identifier field 604 when sending its BUM traffic. 606 6 Acknowledgement 608 We would like to thank Dennis Cai, Antoni Przygienda, and Jeffrey 609 Zhang for their valuable comments. 611 7 Security Considerations 613 Since this draft uses the EVPN constructs of [RFC7432] and [RFC7623], 614 the same security considerations in these drafts are also applicable 615 here. Furthermore, this draft provides additional security check by 616 allowing sites (or ACs) of an EVPN instance to be designated as 617 "Root" or "Leaf" and preventing any traffic exchange among "Leaf" 618 sites of that VPN through ingress filtering for known unicast traffic 619 and egress filtering for BUM traffic. 621 8 IANA Considerations 623 This document requests the allocation of value 5 in the "EVPN 624 Extended Community Sub-Types" registry defined in [RFC7153] and 625 modification of the registry as follow: 627 SUB-TYPE VALUE NAME Reference 629 0x05 E-TREE Extended Community This document 630 6-255 Unassigned 632 9 References 634 9.1 Normative References 636 [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate 637 Requirement Levels", BCP 14, RFC 2119, March 1997. 639 [RFC7432] Sajassi et al., "BGP MPLS Based Ethernet VPN", February, 640 2015. 642 [RFC7623] Sajassi et al., "Provider Backbone Bridging Combined with 643 Ethernet VPN (PBB-EVPN)", September, 2015. 645 9.2 Informative References 647 [RFC7387] Key et al., "A Framework for E-Tree Service over MPLS 648 Network", October 2014. 650 [RFC4360] S. Sangli et al, "BGP Extended Communities Attribute", 651 February, 2006. 653 [RFC7153] Rosen et al., "IANA Registries for BGP Extended 654 Communities", March, 2014. 656 [RFC6514] Aggarwal et al., "BGP Encodings and Procedures for 657 Multicast in MPLS/BGP IP VPNs", February, 2012. 659 Authors' Addresses 661 Ali Sajassi 662 Cisco 663 Email: sajassi@cisco.com 665 Samer Salam 666 Cisco 667 Email: ssalam@cisco.com 669 Wim Henderickx 670 Alcatel-Lucent 671 Email: wim.henderickx@alcatel-lucent.com 673 Jim Uttaro 674 AT&T 675 Email: ju1738@att.com 677 Aldrin 678 Bloomberg Issac 679 Email: aisaac@juniper.net 681 Sami Boutros 682 Cisco 683 Email: boutros.sami@gmail.com 685 John Drake 686 Juniper 687 Email: jdrake@juniper.net 689 Wen Lin 690 Juniper 691 Email: wlin@juniper.net