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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 L2VPN WG Raymond Key (editor) 2 Internet Draft Lucy Yong, Huawei (editor) 3 Intended status: Informational Simon Delord 4 Expires: January 2015 Telstra 5 Frederic Jounay, Orange CH 6 Lizhong Jin 7 July 20, 2014 9 A Framework for Ethernet Tree (E-Tree) Service over a Multiprotocol 10 Label Switching (MPLS) Network 11 draft-ietf-l2vpn-etree-frwk-07.txt 13 Abstract 15 This document describes an Ethernet-Tree (E-Tree) solution framework 16 for supporting the Metro Ethernet Forum (MEF) E-Tree service over a 17 Multiprotocol Label Switching (MPLS) network. The objective is to 18 provide a simple and effective approach to emulate E-Tree services 19 in addition to Ethernet LAN (E-LAN) services on an existing MPLS 20 network. 22 Status of this Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF), its areas, and its working groups. Note that 29 other groups may also distribute working documents as Internet- 30 Drafts. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 The list of current Internet-Drafts can be accessed at 38 http://www.ietf.org/ietf/1id-abstracts.txt 40 The list of Internet-Draft Shadow Directories can be accessed at 41 http://www.ietf.org/shadow.html 43 This Internet-Draft will expire on January 21, 2015. 45 Copyright Notice 47 Copyright (c) 2014 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (http://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction...................................................3 63 1.1. Terminology...............................................3 64 2. Overview.......................................................4 65 2.1. Ethernet Bridge Network...................................4 66 2.2. MEF Multipoint Ethernet Services: E-LAN and E-Tree........4 67 2.3. IETF L2VPN................................................5 68 2.3.1. Virtual Private LAN Service (VPLS)...................5 69 2.3.2. Ethernet VPN (EVPN)..................................5 70 2.3.3. Virtual Private Multicast Service (VPMS).............6 71 3. E-Tree Architecture Reference Model............................6 72 4. E-Tree Use Cases...............................................8 73 5. L2VPN Gaps for Emulating MEF E-Tree Service...................10 74 5.1. No Differentiation on AC Role............................10 75 5.2. No AC Role Indication or Advertisement...................10 76 5.3. Other Issues.............................................10 77 6. Security Considerations.......................................10 78 7. IANA Considerations...........................................11 79 8. References....................................................11 80 8.1. Normative References.....................................11 81 8.2. Informative References...................................11 82 9. Contributing Authors..........................................12 83 10. Acknowledgments..............................................12 85 1. Introduction 87 This document describes an Ethernet-Tree (E-Tree) solution framework 88 for supporting the Metro Ethernet Forum (MEF) E-Tree service over a 89 Multiprotocol Label Switching (MPLS) network. The objective is to 90 provide a simple and effective approach to emulate E-Tree services in 91 addition to Ethernet LAN (E-LAN) services on an existing MPLS 92 network. 94 This document extends the existing IETF specified Layer 2 Virtual 95 Private Network (L2VPN) framework [RFC4664] to provide the emulation 96 of E-Tree services over an MPLS network. It specifies the E-Tree 97 architecture reference model and describes the corresponding 98 functional components. It also points out the gaps and required 99 extension areas in existing L2VPN solutions such as Virtual Private 100 LAN Service (VPLS)[RFC4761][RFC4762] and Ethernet Virtual Private 101 Network (EVPN)[EVPN] for supporting E-Tree services. 103 1.1. Terminology 105 This document adopts all the terminologies defined in RFC4664 106 [RFC4664], RFC4761 [RFC4761], and RFC4762 [RFC4762]. It also uses the 107 following terminologies: 109 Leaf Attachment Circuit (AC): An AC with Leaf role. An ingress 110 Ethernet frame at a Leaf AC (Ethernet frame arriving over an AC at 111 the provider edge (PE) of an MPLS network) can only be delivered to 112 one or more Root ACs in an E-Tree service instance. An ingress 113 Ethernet frame at a Leaf AC must not be delivered to any Leaf ACs in 114 the E-Tree service instance. 116 Root AC: An AC with Root role. An ingress Ethernet frame at a Root AC 117 can be delivered to one or more of the other ACs in the associated E- 118 Tree service instance. 120 E-Tree: An Ethernet VPN service in which each AC is assigned the role 121 of a Root or Leaf. The forwarding rules in E-Tree are: Root AC can 122 communicate with other Root ACs and Leaf ACs; Leaf ACs can only 123 communicate with Root ACs. 125 2. Overview 127 2.1. Ethernet Bridge Network 129 In this document, Ethernet bridge network refers to the Ethernet 130 bridge/switch network defined in IEEE802.1Q [IEEE802.1Q]. In a bridge 131 network, a data frame is an Ethernet frame; data forwarding is based 132 on destination MAC address; MAC reachability is learned in the data 133 plane based on the source MAC address and the port (or tagged port) 134 on which the frame arrives; and the MAC aging mechanism is used to 135 remove inactive MAC addresses from the MAC forwarding table on an 136 Ethernet switch. 138 Data frames arriving at a switch may be destined to known unicast MAC 139 destinations, unknown, multicast, or broadcast MAC destinations. 140 Unknown, multicast, and broadcast frames are forwarded in a similar 141 way, i.e. to every port except the ingress port on which the frame 142 arrives. Multicast forwarding can be further constrained when using 143 multicast control protocol snooping or multicast MAC registration 144 protocols. [IEEE802.1Q] 146 An Ethernet host receiving an Ethernet frame checks the destination 147 address in the frame to decide whether it is the intended 148 destination. 150 2.2. MEF Multipoint Ethernet Services: E-LAN and E-Tree 152 MEF6.2 [MEF6.2] defines two multipoint Ethernet Service types: 154 o E-LAN (Ethernet LAN), a multipoint-to-multipoint service 156 o E-Tree (Ethernet Tree), a rooted-multipoint service 158 According to MEF's technical specification, a multipoint Ethernet 159 service is always bidirectional, which means that any AC in the 160 service can send and receive Ethernet frames to/from customer 161 equipment (CE). Note that the term AC is equivalent to MEF User- 162 Network Interface (UNI). Furthermore, MEF also defines AC roles. One 163 role is Root and another is Leaf. Besides destination MAC-based 164 forwarding, additional forwarding rules defined by MEF for a 165 multipoint Ethernet Service are below: 167 o A Root AC can receive/transmit a frame from/to any other ACs. 169 o A Leaf AC can receive/transmit a frame from/to any Root ACs. 171 o A Leaf AC cannot receive/transmit a frame from/to any Leaf ACs. 173 For an E-LAN service, all ACs have the Root role, which means that 174 any AC can communicate with other ACs in the service. The E-LAN 175 service defined by MEF may be implemented by IETF L2VPN solutions 176 such as VPLS and EVPN [EVPN]. 178 An E-Tree service has one or more Root ACs and at least two Leaf ACs. 179 An E-Tree service supports the communication among the roots and 180 between a root and a leaf but prohibits the communication among the 181 leaves. Existing IETF L2VPN solutions can't support the E-Tree 182 service. This document specifies the E-Tree architecture reference 183 model that supports the E-Tree service defined by MEF [MEF6.2]. 184 Section 4 will discuss different E-Tree use cases. 186 2.3. IETF L2VPN 188 2.3.1. Virtual Private LAN Service (VPLS) 190 VPLS [RFC4761] [RFC4762] is an L2VPN solution that provides 191 multipoint-to-multipoint Ethernet connectivity across IP/MPLS 192 networks. VPLS emulates traditional Ethernet Virtual LAN Services 193 (VLAN) in MPLS networks, and may support MEF E-LAN services. 195 A data frame in VPLS is an Ethernet frame. Data forwarding in a VPLS 196 instance is based on the destination MAC address and the VLAN on 197 which the frame arrives. MAC reachability learning is performed in 198 the data plane based on the source address and the AC or Pseudowire 199 (PW) on which the frame arrives. MAC aging is also the mechanism used 200 to remove inactive MAC addresses from a VPLS switching instance (VSI) 201 on a Provider Edge (PE). VPLS supports forwarding for known unicast, 202 unknown unicast, broadcast, and multicast Ethernet frames. 204 Many service providers have deployed VPLS in their networks to 205 provide L2VPN services to customers. 207 2.3.2. Ethernet VPN (EVPN) 209 Ethernet VPN [EVPN] is an enhanced L2VPN solution that emulates an 210 Ethernet LAN or virtual LAN(s) across MPLS networks. 212 EVPN supports active-active multi-homing of CEs and uses 213 Multiprotocol Border Gateway Protocol (MP-BGP) control plane to 214 advertise MAC address reachability from an ingress PE to egress PEs. 215 Thus, a PE learns MAC addresses reachable over local ACs in the data 216 plane and other MAC addresses reachable across the MPLS network over 217 remote ACs via the EVPN MP-BGP control plane. As a result, EVPN aims 218 to support large-scale L2VPN with better resiliency compared to VPLS. 220 EVPN is relatively new technique and is still under development in 221 IETF L2VPN WG. 223 2.3.3. Virtual Private Multicast Service (VPMS) 225 VPMS [VPMS] is an L2VPN solution that provides point-to-multipoint 226 connectivity across MPLS networks and supports various attachment 227 circuit (AC) types, including Frame Relay, ATM, Ethernet, PPP, etc. 229 In the case of Ethernet ACs, VPMS provides single coverage of 230 receiver membership, i.e. there is no distinct differentiation among 231 multicast groups in one VPN. Destination address in the Ethernet 232 frame is not used in data forwarding. 234 VPMS supports unidirectional point-to-multipoint transport from a 235 sender to multiple receivers and may support reverse transport in a 236 point-to-point manner. 238 3. E-Tree Architecture Reference Model 240 Figure 1 illustrates E-Tree architecture reference model. Three 241 provider edges (PEs), PE1, PE2, and PE3 are shown in the Figure. Each 242 PE has a Virtual Service Instance (VSI) associated with an E-Tree 243 service instance. A CE attaches to the VSI on a PE via an AC. Each AC 244 must be configured with a root or leaf role. In Figure 1, AC1 AC2, 245 AC5, AC6, AC9, AC10 are Root ACs; AC3, AC4, AC7, AC8, AC11, AC12 are 246 Leaf ACs. This implies that a PE (local or remote) processes the 247 Ethernet frames from CE01, CE02, etc as if they are originated from a 248 Root AC; and processes the Ethernet frames from CE03, CE04, etc as if 249 they are originated from a Leaf AC. 251 Under this architecture model, the forwarding rules among the ACs, 252 regardless whether sending AC and receiving AC are on the same PE or 253 on different PEs, are described as follow: 255 o An egress frame (frame to be transmitted over an AC) at an AC with 256 Root role must be the result of an ingress frame at an AC (frame 257 received at an AC) that has Root or Leaf role attached to the same 258 E-tree service instance. 260 o An egress frame at the AC with Leaf role must be the result of an 261 ingress frame at an AC that has Root role attached to the same E- 262 tree service instance. 264 These rules apply to all frame types, i.e. Known Unicast, Unknown, 265 Broadcast, and Multicast. For Known Unicast frames, forwarding in a 266 VSI context is based on the destination MAC address. 268 A VSI on a PE corresponds to an E-Tree service instance and maintains 269 a MAC forwarding table which is isolated from other VSI tables on the 270 PE. It also keeps the track of local AC roles. The VSI receives a 271 frame from an AC or across the MPLS core; and forwards the frame to 272 another AC over which the destination is reachable according to the 273 VSI forwarding table and forwarding rules described above. When the 274 target AC is on a remote PE, the VSI forwards the frame to the remote 275 PE over the MPLS core. Forwarding over the MPLS core will be 276 dependent on the E-tree solution. For instance, a solution may adopt 277 PWs to mesh VSIs as in VPLS, and forward frames over VSIs subject to 278 the E-tree forwarding rules. Alternatively, a solution may adopt the 279 EVPN forwarding paradigm constrained by the E-tree forwarding rules. 280 Thus, solutions that satisfy the E-tree requirements could be 281 extensions to VPLS and EVPN. 283 <------------E-Tree-----------> 284 PE1+---------+ +---------+PE2 285 +----+ | +---+ | | +---+ | +----+ 286 |CE01+----AC1----+--+ | | | | +--+----AC5----+CE05| 287 +----+ (Root AC) | | V | | | | V | | (Root AC) +----+ 288 +----+ | | | | | | | | +----+ 289 |CE02+----AC2----+--+ | | | | +--+----AC6----+CE06| 290 +----+ (Root AC) | | S +--+---------+--+ S | | (Root AC) +----+ 291 +----+ | | | | | | | | +----+ 292 |CE03+----AC3----+--+ | | | | +--+----AC7----+CE07| 293 +----+ (Leaf AC) | | I | | | | I | | (Leaf AC) +----+ 294 +----+ | | | | | | | | +----+ 295 |CE04+----AC4----+--+ | | | | +--+----AC8----+CE08| 296 +----+ (Leaf AC) | +-+-+ | | +-+-+ | (Leaf AC) +----+ 297 +----+----+ +----+----+ 298 | MPLS Core | 299 | +----+----+ 300 | | +-+-+ | +----+ 301 | | | +--+----AC9----+CE09| 302 | | | V | | (Root AC) +----+ 303 | | | | | +----+ 304 | | | +--+----AC10---+CE10| 305 +--------------+--+ S | | (Root AC) +----+ 306 | | | | +----+ 307 | | +--+----AC11---+CE11| 308 | | I | | (Leaf AC) +----+ 309 | | | | +----+ 310 | | +--+----AC12---+CE12| 311 | +---+ | (Leaf AC) +----+ 312 PE3 +---------+ 313 <-------------E-Tree----------> 315 Figure 1 E-Tree Architecture Reference Model 317 In most use cases, an E-Tree service has only a few Root ACs (root CE 318 sites) but many Leaf ACs (leaf CE sites). Furthermore, a PE may have 319 only Root ACs or only Leaf ACs. Figure 1 provides a general E-Tree 320 architecture model. 322 4. E-Tree Use Cases 324 Table 1 below presents some major use cases for E-Tree. 326 +---------------------------+--------------+------------+ 327 | Use Case | Root AC | Leaf AC | 328 +---+---------------------------+--------------+------------+ 329 | 1 | Hub & Spoke VPN | Hub Site | Spoke Site | 330 +---+---------------------------+--------------+------------+ 331 | 2 | Wholesale Access | Customer's | Customer's | 332 | | | Interconnect | Subscriber | 333 +---+---------------------------+--------------+------------+ 334 | 3 | Mobile Backhaul | RAN NC | RAN BS | 335 +---+---------------------------+--------------+------------+ 336 | 4 | IEEE 1588 PTPv2 [1588] | PTP Server | PTP Client | 337 | | Clock Synchronization | | | 338 +---+---------------------------+--------------+------------+ 339 | 5 | Internet Access | BNG Router | Subscriber | 340 | | Reference: [TR-101] | | | 341 +---+---------------------------+--------------+------------+ 342 | 6 | Broadcast Video | Video Source | Subscriber | 343 | | (unidirectional only) | | | 344 +---+---------------------------+--------------+------------+ 345 | 7 | Broadcast/Multicast Video | Video Source | Subscriber | 346 | | plus Control Channel | | | 347 +---+---------------------------+--------------+------------+ 348 | 8 | Device Management | Management | Managed | 349 | | | System | Device | 350 +---+---------------------------+--------------+------------+ 352 Where: 353 RAN: Radio Access Network 354 NC: Network Controller 355 BS: Base Station 356 PTP: Precision Time Protocol 357 BNG: Broadband Network Gateway 359 Table 1 E-Tree Use Cases 361 Common to all use cases, direct Layer2 Leaf-to-Leaf communication is 362 required to be prohibited. For Mobile backhaul, this may not be valid 363 for LTE X2 interfaces; LTE X2 interface [LTE] between two evolved 364 node B (eNB) enables the communication in between. E-Tree service is 365 appropriate for such use cases. 367 Also common to the use cases mentioned above, there may be single or 368 multiple Root ACs in one E-Tree service. The need of multiple Root- 369 ACs may be driven by redundancy requirement or multiple serving 370 sites. Whether a particular E-Tree service needs to support single or 371 multiple Root ACs depends on an application. 373 5. L2VPN Gaps for Emulating MEF E-Tree Service 375 E-Tree Service defines special forwarding rules that prohibit 376 forwarding Ethernet frames among leaves. This poses some challenges 377 to IETF L2VPN solutions such as VPLS and EVPN in emulating E-Tree 378 service over an MPLS network. There are two major issues described in 379 the following sections. 381 5.1. No Differentiation on AC Role 383 IP/MPLS L2VPN architecture has no distinction role on Attachment 384 Circuit (AC) and supports any-to-any connectivity among all ACs. It 385 does not have any mechanism to support forwarding constraint based on 386 an AC role. However, E-Tree service defines two AC roles, Root and 387 Leaf, and defines the forwarding rules based on the frame originating 388 and receiving AC roles. 390 5.2. No AC Role Indication or Advertisement 392 In an L2VPN, when a PE, say PE2, receives a frame from another PE, 393 say PE1, over the MPLS core, PE2 does not know if the frame from PE1 394 is originated from a root AC or leaf AC. This causes the forwarding 395 issue on PE2 because the E-Tree forwarding rules require that the 396 forwarder must know the role of the frame origin, i.e. from root AC 397 or leaf AC. This is specifically important, when PE2 has both root AC 398 and leaf AC attached to the VSI. E-Tree forwarding rules apply to all 399 types of frames (known unicast destination, unknown unicast 400 destination, multicast and broadcast). 402 5.3. Other Issues 404 Some desirable requirements for IETF E-Tree are specific to an 405 IP/MPLS L2VPN implementation such as Leaf-only PE. Leaf-only PE is 406 the PE that only has Leaf AC(s) in an E-Tree service instance, thus 407 other PEs on the same E-Tree service instance do not necessarily 408 forward the frames originated from a Leaf AC to the Leaf-only PE, 409 which may save some network resources. It is also desirable for E- 410 Tree solution to work with existing PEs that support single-role AC 411 and the role is equivalent to the root in an E-Tree Service. These 412 requirements are described in the E-Tree requirement document. 413 [RFC7152] 415 6. Security Considerations 417 An E-tree service may be deployed for security reasons to prohibit 418 communication among sites (leaves). An E-tree solution must enforce 419 E-Tree forwarding constraints. The solution must also guarantee that 420 Ethernet frames do not leak outside of the E-tree service instance to 421 which they belong. 423 An E-Tree service prohibits communication among leaf sites but does 424 not have knowledge of higher layer security constraint. Therefore, in 425 general, higher layer applications can not rely on E-Tree to provide 426 the security protection unless all security constraints are fully 427 implemented by E-Tree service. 429 Other than that, there are no additional security considerations 430 beyond those already described in [RFC4761], [RFC4762], and [EVPN]. 432 7. IANA Considerations 434 The document requires no IANA action. 436 8. References 438 8.1. Normative References 440 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 441 Requirement Levels", BCP 14, RFC 2119, March 1997. 443 [MEF6.2] MEF, "Metro Ethernet Forum, Ethernet Services Definitions - 444 Phase 2", April 2008 446 [RFC4664] Andersson, L., et al, "Framework for Layer 2 Virtual 447 Private Network (L2VPNs)", RFC4664, Sept. 2006 449 [RFC4761] Kompella & Rekhter, "Virtual Private LAN Service (VPLS) 450 Using BGP for Auto-Discovery and Signaling", RFC4761, 451 January 2007 453 [RFC4762] Lasserre & Kompella, "Virtual Private LAN Service (VPLS) 454 Using Label Distribution Protocol (LDP) Signaling", 455 RFC4762, January 2007 457 [RFC7152] Key, et al., "Requirements for Metro Ethernet Forum (MEF) 458 Ethernet-Tree (E-Tree) Support in L2VPN", RFC7152, April 459 2011997. 461 8.2. Informative References 463 [IEEE802.1Q] IEEE802.1, "Media Access Control (MAC) Bridges and 464 Virtual Bridged Local Area", IEEE802.1Q, 2011 466 [1588] IEEE 1588, "Precision Time Protocol", IEEE 1588, 2013 468 [LTE] 3GPP TS, "Evolved Universal Terrestrial Radio Access (E- 469 UTRA) and Evolved Universal Terrestrial Radio Access 470 Network (E-UTRAN)", V11.2.0, June, 2012 472 [TR-101] Broadband Forum, "Migration to Ethernet-Based Broadband 473 Aggregation Issue 2", July 2011 475 [VPMS] Kamite, et al., "Framework and Requirements for Virtual 476 Private Multicast Service (VPMS)", draft-ietf-l2vpn-vpms- 477 frmwk-requirements-05, work in progress 479 [EVPN] Sajassi, et al., "BGP MPLS Based Ethernet VPN", draft-ietf- 480 l2vpn-evpn-07, work in progress 482 9. Contributing Authors 484 The following people contribute the document as co-authors. 486 Yuji Kamite 487 NTT Communications Corporation 488 Granpark Tower 489 3-4-1 Shibaura, Minato-ku 490 Tokyo 108-8118, Japan 491 Email: y.kamite@ntt.com 493 Wim Henderickx 494 Alcatel-Lucent 495 Copernicuslaan 50 496 2018 Antwerp, Belgium 497 Email: wim.henderickx@alcatel-lucent.com 499 10. Acknowledgments 501 Authors like to thank Nabil Bitar for this detail review and 502 suggestions. 504 Authors' Addresses 506 Raymond Key (editor) 508 Email: raymond.key@ieee.org 509 Lucy Yong (editor) 510 Huawei USA 512 Email: lucy.yong@huawei.com 514 Simon Delord 515 Telstra 517 Email: simon.delord@gmail.com 519 Frederic Jounay 520 Orange CH 521 4 rue caudray 1020 Renens 522 Switzerland 524 Email: frederic.jounay@orange.ch 526 Lizhong Jin 528 Email: lizho.jin@gmail.com