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diff --git a/doc/rfc/rfc7387.txt b/doc/rfc/rfc7387.txt new file mode 100644 index 0000000..1ef8cb7 --- /dev/null +++ b/doc/rfc/rfc7387.txt @@ -0,0 +1,731 @@ + + + + + + +Internet Engineering Task Force (IETF) R. Key, Ed. +Request for Comments: 7387 +Category: Informational L. Yong, Ed. +ISSN: 2070-1721 Huawei + S. Delord + Telstra + F. Jounay + Orange CH + L. Jin + October 2014 + + + A Framework for Ethernet Tree (E-Tree) Service + over a Multiprotocol Label Switching (MPLS) Network + +Abstract + + This document describes an Ethernet-Tree (E-Tree) solution framework + for supporting the Metro Ethernet Forum (MEF) E-Tree service over a + Multiprotocol Label Switching (MPLS) network. The objective is to + provide a simple and effective approach to emulate E-Tree services in + addition to Ethernet LAN (E-LAN) services on an existing MPLS + network. + +Status of This Memo + + This document is not an Internet Standards Track specification; it is + published for informational purposes. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Not all documents + approved by the IESG are a candidate for any level of Internet + Standard; see Section 2 of RFC 5741. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + http://www.rfc-editor.org/info/rfc7387. + + + + + + + + + + + + +Key, et al. Informational [Page 1] + +RFC 7387 E-Tree Framework October 2014 + + +Copyright Notice + + Copyright (c) 2014 IETF Trust and the persons identified as the + document authors. All rights reserved. + + This document is subject to BCP 78 and the IETF Trust's Legal + Provisions Relating to IETF Documents + (http://trustee.ietf.org/license-info) in effect on the date of + publication of this document. Please review these documents + carefully, as they describe your rights and restrictions with respect + to this document. Code Components extracted from this document must + include Simplified BSD License text as described in Section 4.e of + the Trust Legal Provisions and are provided without warranty as + described in the Simplified BSD License. + +Table of Contents + + 1. Introduction ....................................................3 + 1.1. Terminology ................................................3 + 2. Overview ........................................................4 + 2.1. Ethernet Bridge Network ....................................4 + 2.2. MEF Multipoint Ethernet Services: E-LAN and E-Tree .........4 + 2.3. IETF L2VPN .................................................5 + 2.3.1. Virtual Private LAN Service (VPLS) ..................5 + 2.3.2. Ethernet VPN (EVPN) .................................5 + 2.3.3. Virtual Private Multicast Service (VPMS) ............6 + 3. E-Tree Architecture Reference Model .............................6 + 4. E-Tree Use Cases ................................................8 + 5. L2VPN Gaps for Emulating MEF E-Tree Service .....................9 + 5.1. No Differentiation on AC Role ..............................9 + 5.2. No AC Role Indication or Advertisement .....................9 + 5.3. Other Issues ...............................................9 + 6. Security Considerations ........................................10 + 7. References .....................................................11 + 7.1. Normative References ......................................11 + 7.2. Informative References ....................................11 + Acknowledgments ...................................................12 + Contributors ......................................................12 + Authors' Addresses ................................................13 + + + + + + + + + + + + +Key, et al. Informational [Page 2] + +RFC 7387 E-Tree Framework October 2014 + + +1. Introduction + + This document describes an Ethernet-Tree (E-Tree) solution framework + for supporting the Metro Ethernet Forum (MEF) E-Tree service over a + Multiprotocol Label Switching (MPLS) network. The objective is to + provide a simple and effective approach to emulate E-Tree services in + addition to Ethernet LAN (E-LAN) services on an existing MPLS + network. + + This document extends the existing IETF-specified Layer 2 Virtual + Private Network (L2VPN) framework [RFC4664] to provide the emulation + of E-Tree services over an MPLS network. It specifies the E-Tree + architecture reference model and describes the corresponding + functional components. It also points out the gaps and required + extension areas in existing L2VPN solutions such as Virtual Private + LAN Service (VPLS) [RFC4761] [RFC4762] and Ethernet Virtual Private + Network (EVPN) [EVPN] for supporting E-Tree services. + +1.1. Terminology + + This document adopts all the terminologies defined in RFC 4664 + [RFC4664], RFC 4761 [RFC4761], and RFC 4762 [RFC4762]. It also uses + the following terms: + + Leaf Attachment Circuit (AC): An AC with Leaf role. An ingress + Ethernet frame at a Leaf AC (Ethernet frame arriving over an AC at + the Provider Edge (PE) of an MPLS network) can only be delivered + to one or more Root ACs in an E-Tree service instance. An ingress + Ethernet frame at a Leaf AC must not be delivered to any Leaf ACs + in the E-Tree service instance. + + Root AC: An AC with Root role. An ingress Ethernet frame at a Root + AC can be delivered to one or more of the other ACs in the + associated E-Tree service instance. + + E-Tree: An Ethernet VPN service in which each AC is assigned the role + of a Root or Leaf. The forwarding rules in an E-Tree are as + follows: + + o The Root AC can communicate with other Root ACs and Leaf ACs. + + o Leaf ACs can only communicate with Root ACs. + + + + + + + + + +Key, et al. Informational [Page 3] + +RFC 7387 E-Tree Framework October 2014 + + +2. Overview + +2.1. Ethernet Bridge Network + + In this document, "Ethernet bridge network" refers to the Ethernet + bridge/switch network defined in IEEE 802.1Q [IEEE802.1Q]. In a + bridge network, a data frame is an Ethernet frame; data forwarding is + based on destination Media Access Control (MAC) address; MAC + reachability is learned in the data plane based on the source MAC + address and the port (or tagged port) on which the frame arrives; and + the MAC aging mechanism is used to remove inactive MAC addresses from + the MAC forwarding table on an Ethernet switch. + + Data frames arriving at a switch may be destined to known unicast, + unknown unicast, multicast, or broadcast MAC destinations. Unknown + unicast, multicast, and broadcast frames are forwarded in a similar + way, i.e., to every port except the ingress port on which the frame + arrives. Multicast forwarding can be further constrained when using + multicast control protocol snooping or using multicast MAC + registration protocols [IEEE802.1Q]. + + An Ethernet host receiving an Ethernet frame checks the destination + address in the frame to decide whether it is the intended + destination. + +2.2. MEF Multipoint Ethernet Services: E-LAN and E-Tree + + MEF 6.1 [MEF6.1] defines two multipoint Ethernet Service types: + + o E-LAN (Ethernet LAN), a multipoint-to-multipoint service + + o E-Tree (Ethernet Tree), a rooted-multipoint service + + The MEF defines User-Network Interface (UNI) in a multipoint service + as the Ethernet interface between Customer Equipment (CE) and a + Provider Edge (PE), i.e., the PE can send and receive Ethernet frames + to/from the CE. The MEF also defines UNI roles in a multipoint + service. One role is Root, and another is Leaf. + + Note that MEF UNI in a service is equivalent to the Attachment + Circuit (AC) defined in L2VPN [RFC4664]. The Root AC and Leaf AC + defined in this document are the same as the Root UNI and Leaf UNI as + defined in MEF 10.3 [MEF10.3]. The terms "Root AC" and "Leaf AC" are + used in the following MEF service description. + + + + + + + +Key, et al. Informational [Page 4] + +RFC 7387 E-Tree Framework October 2014 + + + For an E-LAN service, all ACs have the Root role, which means that + any AC can communicate with other ACs in the service. The E-LAN + service defined by the MEF may be implemented by IETF L2VPN solutions + such as VPLS and EVPN [EVPN]. + + An E-Tree service has one or more Root ACs and at least two Leaf ACs. + An E-Tree service supports communication among the roots and between + a root and a leaf but prohibits communication among the leaves. + Existing IETF L2VPN solutions can't support the E-Tree service. This + document specifies the E-Tree architecture reference model that + supports the E-Tree service defined by the MEF [MEF6.1]. Section 4 + will discuss different E-Tree use cases. + +2.3. IETF L2VPN + +2.3.1. Virtual Private LAN Service (VPLS) + + VPLS [RFC4761] [RFC4762] is an L2VPN solution that provides + multipoint-to-multipoint Ethernet connectivity across IP/MPLS + networks. VPLS emulates traditional Ethernet Virtual LAN (VLAN) + services in MPLS networks and may support MEF E-LAN services. + + A data frame in VPLS is an Ethernet frame. Data forwarding in a VPLS + instance is based on the destination MAC address and the VLAN on + which the frame arrives. MAC reachability learning is performed in + the data plane based on the source address and the AC or pseudowire + (PW) on which the frame arrives. MAC aging is the mechanism used to + remove inactive MAC addresses from a VPLS switching instance (VSI) on + a PE. VPLS supports forwarding for known unicast frames, as well as + unknown unicast, broadcast, and multicast Ethernet frames. + + Many service providers have deployed VPLS in their networks to + provide L2VPN services to customers. + +2.3.2. Ethernet VPN (EVPN) + + Ethernet VPN [EVPN] is an enhanced L2VPN solution that emulates an + Ethernet LAN or virtual LAN(s) across MPLS networks. + + EVPN supports active-active multihoming of CEs and uses the + Multiprotocol Border Gateway Protocol (MP-BGP) control plane to + advertise MAC address reachability from an ingress PE to egress PEs. + Thus, a PE learns MAC addresses that are reachable over local ACs in + the data plane and other MAC addresses reachable across the MPLS + network over remote ACs via the EVPN MP-BGP control plane. As a + result, EVPN aims to support large-scale L2VPN with better resiliency + compared to VPLS. + + + + +Key, et al. Informational [Page 5] + +RFC 7387 E-Tree Framework October 2014 + + + EVPN is a relatively new technique and is still under development in + the IETF L2VPN WG. + +2.3.3. Virtual Private Multicast Service (VPMS) + + VPMS [VPMS] is an L2VPN solution that provides point-to-multipoint + connectivity across MPLS networks and supports various attachment + circuit (AC) types, including Frame Relay, ATM, Ethernet, PPP, etc. + + In the case of Ethernet ACs, VPMS provides single coverage of + receiver membership, i.e., there is no differentiation among + multicast groups in one VPN. The destination address in the Ethernet + frame is not used in data forwarding. + + VPMS supports unidirectional point-to-multipoint transport from a + sender to multiple receivers and may support reverse transport in a + point-to-point manner. + +3. E-Tree Architecture Reference Model + + Figure 1 illustrates the E-Tree architecture reference model. Three + Provider Edges -- PE1, PE2, and PE3 -- are shown in the figure. Each + PE has a Virtual Service Instance (VSI) associated with an E-Tree + service instance. A CE attaches to the VSI on a PE via an AC. Each + AC must be configured with a Root or Leaf role. In Figure 1, AC1, + AC2, AC5, AC6, AC9, and AC10 are Root ACs; AC3, AC4, AC7, AC8, AC11, + and AC12 are Leaf ACs. This implies that a PE (local or remote) + processes the Ethernet frames from CE01, CE02, etc., as if they + originated from a Root AC, and it processes the Ethernet frames from + CE03, CE04, etc., as if they originated from a Leaf AC. + + Under this architecture model, the forwarding rules among the ACs, + regardless of whether the sending AC and receiving AC are on the same + PE or on different PEs, are described as follows: + + o An egress frame (the frame to be transmitted over an AC) at an AC + with Root role must be the result of an ingress frame at an AC + (the frame received at an AC) that has Root or Leaf role and is + attached to the same E-Tree service instance. + + o An egress frame at the AC with Leaf role must be the result of an + ingress frame at an AC that has Root role and is attached to the + same E-Tree service instance. + + + + + + + + +Key, et al. Informational [Page 6] + +RFC 7387 E-Tree Framework October 2014 + + + <------------E-Tree-----------> + PE1+---------+ +---------+PE2 + +----+ | +---+ | | +---+ | +----+ + |CE01+----AC1----+--+ | | | | +--+----AC5----+CE05| + +----+ (Root AC) | | V | | | | V | | (Root AC) +----+ + +----+ | | | | | | | | +----+ + |CE02+----AC2----+--+ | | | | +--+----AC6----+CE06| + +----+ (Root AC) | | S +--+---------+--+ S | | (Root AC) +----+ + +----+ | | | | | | | | +----+ + |CE03+----AC3----+--+ | | | | +--+----AC7----+CE07| + +----+ (Leaf AC) | | I | | | | I | | (Leaf AC) +----+ + +----+ | | | | | | | | +----+ + |CE04+----AC4----+--+ | | | | +--+----AC8----+CE08| + +----+ (Leaf AC) | +-+-+ | | +-+-+ | (Leaf AC) +----+ + +----+----+ +----+----+ + | MPLS Core | + | +----+----+ + | | +-+-+ | +----+ + | | | +--+----AC9----+CE09| + | | | V | | (Root AC) +----+ + | | | | | +----+ + | | | +--+----AC10---+CE10| + +--------------+--+ S | | (Root AC) +----+ + | | | | +----+ + | | +--+----AC11---+CE11| + | | I | | (Leaf AC) +----+ + | | | | +----+ + | | +--+----AC12---+CE12| + | +---+ | (Leaf AC) +----+ + PE3 +---------+ + <-------------E-Tree----------> + + Figure 1: E-Tree Architecture Reference Model + + These rules apply to all frame types, i.e., known unicast, unknown + unicast, broadcast, and multicast. For known unicast frames, + forwarding in a VSI context is based on the destination MAC address. + + A VSI on a PE corresponds to an E-Tree service instance and maintains + a MAC forwarding table that is isolated from other VSI tables on the + PE. It also keeps track of local AC roles. The VSI receives a frame + from an AC or across the MPLS core, and it forwards the frame to + another AC over which the destination is reachable according to the + VSI forwarding table and forwarding rules described above. When the + target AC is on a remote PE, the VSI forwards the frame to the remote + PE over the MPLS core. Forwarding over the MPLS core will be + dependent on the E-Tree solution. For instance, a solution may adopt + PWs to mesh VSIs as in VPLS and to forward frames over VSIs subject + + + +Key, et al. Informational [Page 7] + +RFC 7387 E-Tree Framework October 2014 + + + to the E-Tree forwarding rules. Alternatively, a solution may adopt + the EVPN forwarding paradigm constrained by the E-Tree forwarding + rules. Thus, solutions that satisfy the E-Tree requirements could be + extensions to VPLS and EVPN. + + In most use cases, an E-Tree service has only a few Root ACs (root CE + sites) but many Leaf ACs (leaf CE sites). Furthermore, a PE may have + only Root ACs or only Leaf ACs. Figure 1 provides a general E-Tree + architecture model. + +4. E-Tree Use Cases + + Table 1 below presents some major use cases for E-Tree. + + +---------------------------+--------------+------------+ + | Use Case | Root AC | Leaf AC | + +---+---------------------------+--------------+------------+ + | 1 | Hub & Spoke VPN | Hub Site | Spoke Site | + +---+---------------------------+--------------+------------+ + | 2 | Wholesale Access | Customer's | Customer's | + | | | Interconnect | Subscriber | + +---+---------------------------+--------------+------------+ + | 3 | Mobile Backhaul | RAN NC | RAN BS | + +---+---------------------------+--------------+------------+ + | 4 | IEEE 1588 PTPv2 [IEEE1588]| PTP Server | PTP Client | + | | Clock Synchronization | | | + +---+---------------------------+--------------+------------+ + | 5 | Internet Access | BNG Router | Subscriber | + | | Reference [TR-101] | | | + +---+---------------------------+--------------+------------+ + | 6 | Broadcast Video | Video Source | Subscriber | + | | (unidirectional only) | | | + +---+---------------------------+--------------+------------+ + | 7 | Broadcast/Multicast Video | Video Source | Subscriber | + | | plus Control Channel | | | + +---+---------------------------+--------------+------------+ + | 8 | Device Management | Management | Managed | + | | | System | Device | + +---+---------------------------+--------------+------------+ + + Where: + + RAN: Radio Access Network NC: Network Controller + BS: Base Station PTP: Precision Time Protocol + BNG: Broadband Network Gateway + + Table 1: E-Tree Use Cases + + + + +Key, et al. Informational [Page 8] + +RFC 7387 E-Tree Framework October 2014 + + + Common to all use cases, direct Layer 2 leaf-to-leaf communication is + required to be prohibited. For mobile backhaul, this may not be + valid for Long Term Evolution (LTE) X2 interfaces; an LTE X2 + interface [LTE] enables communication between two evolved Node Bs + (eNBs). E-Tree service is appropriate for such use cases. + + Also common to the use cases mentioned above, there may be one or + multiple Root ACs in one E-Tree service. The need for multiple Root + ACs may be driven by a redundancy requirement or by having multiple + serving sites. Whether a particular E-Tree service needs to support + one or multiple Root ACs depends on the application. + +5. L2VPN Gaps for Emulating MEF E-Tree Service + + The MEF E-Tree service defines special forwarding rules that prohibit + forwarding Ethernet frames among leaves. This poses some challenges + to IETF L2VPN solutions such as VPLS and EVPN in emulating E-Tree + service over an MPLS network. There are two major issues described + in the following subsections. + +5.1. No Differentiation on AC Role + + IP/MPLS L2VPN architecture has no distinct roles on Attachment + Circuits (ACs) and supports any-to-any connectivity among all ACs. + It does not have any mechanism to support forwarding constraints + based on an AC role. However, the MEF E-Tree service defines two AC + roles -- Root and Leaf -- and defines the forwarding rules based on + the originating and receiving AC roles of a given frame. + +5.2. No AC Role Indication or Advertisement + + In an L2VPN, when a PE, say PE2, receives a frame from another PE, + say PE1, over the MPLS core, PE2 does not know if the frame from PE1 + is originated from a Root AC or Leaf AC. This causes the forwarding + issue on PE2 because the E-Tree forwarding rules require that the + forwarder must know the role of the frame origin, i.e., from Root AC + or Leaf AC. This is specifically important when PE2 has both Root AC + and Leaf AC attached to the VSI. E-Tree forwarding rules apply to + all types of frames (known unicast destination, unknown unicast + destination, multicast, and broadcast). + +5.3. Other Issues + + Some desirable requirements for IETF E-Tree are specific to an + IP/MPLS L2VPN implementation such as Leaf-only PE. A Leaf-only PE is + a PE that only has Leaf AC(s) in an E-Tree service instance; thus, + other PEs on the same E-Tree service instance do not necessarily + forward the frames originated from a Leaf AC to the Leaf-only PE, + + + +Key, et al. Informational [Page 9] + +RFC 7387 E-Tree Framework October 2014 + + + which may save some network resources. It is also desirable for an + E-Tree solution to work with existing PEs that support single-role + ACs, where the role is equivalent to the root in an E-Tree service. + These requirements are described in the E-Tree requirement document + [RFC7152]. + +6. Security Considerations + + An E-Tree service may be deployed for security reasons to prohibit + communication among sites (leaves). An E-Tree solution must enforce + E-Tree forwarding constraints. The solution must also guarantee that + Ethernet frames do not leak outside of the E-Tree service instance to + which they belong. + + An E-Tree service prohibits communication among leaf sites but does + not have knowledge of higher-layer security constraints. Therefore, + in general, higher-layer applications cannot rely on E-Tree to + provide security protection unless all security constraints are fully + implemented by the E-Tree service. + + Enhancing L2VPN for E-Tree services inherits the same security issues + described in the L2VPN framework document [RFC4664]. These relate to + both control-plane and data-plane security issues that may arise in + the following areas: + + o issues fully contained in the provider network + + o issues fully contained in the customer network + + o issues in the customer-provider interface network + + The framework document has substantial discussions on the security + issues and potential solutions to address them. An E-Tree solution + must consider these issues and address them properly. VPLS [RFC4761] + [RFC4762] and/or EVPN [EVPN] will likely be candidate solutions for + an E-Tree service over an MPLS network. The security capabilities + built into those solutions will be naturally adopted when supporting + E-Tree. For details, see the Security Considerations sections in + [RFC4761], [RFC4762], and [EVPN]. + + + + + + + + + + + + +Key, et al. Informational [Page 10] + +RFC 7387 E-Tree Framework October 2014 + + +7. References + +7.1. Normative References + + [MEF6.1] Metro Ethernet Forum, "Ethernet Services Definitions - + Phase 2", MEF 6.1, April 2008. + + [MEF10.3] Metro Ethernet Forum, "Ethernet Service Attributes - + Phase 3", MEF 10.3, October 2013. + + [RFC4664] Andersson, L., Ed., and E. Rosen, Ed., "Framework for + Layer 2 Virtual Private Networks (L2VPNs)", RFC 4664, + September 2006, + <http://www.rfc-editor.org/info/rfc4664>. + + [RFC4761] Kompella, K., Ed., and Y. Rekhter, Ed., "Virtual Private + LAN Service (VPLS) Using BGP for Auto-Discovery and + Signaling", RFC 4761, January 2007, + <http://www.rfc-editor.org/info/rfc4761>. + + [RFC4762] Lasserre, M., Ed., and V. Kompella, Ed., "Virtual + Private LAN Service (VPLS) Using Label Distribution + Protocol (LDP) Signaling", RFC 4762, January 2007, + <http://www.rfc-editor.org/info/rfc4762>. + + [RFC7152] Key, R., Ed., DeLord, S., Jounay, F., Huang, L., Liu, + Z., and M. Paul, "Requirements for Metro Ethernet Forum + (MEF) Ethernet-Tree (E-Tree) Support in Layer 2 Virtual + Private Network (L2VPN)", RFC 7152, March 2014, + <http://www.rfc-editor.org/info/rfc7152>. + +7.2. Informative References + + [IEEE802.1Q] IEEE, "IEEE Standard for Local and metropolitan area + networks -- Media Access Control (MAC) Bridges and + Virtual Bridged Local Area", IEEE Std 802.1Q, 2011. + + [IEEE1588] IEEE, "IEEE Standard for a Precision Clock + Synchronization Protocol for Networked Measurement and + Control Systems", IEEE Std 1588, July 2008. + + [LTE] 3GPP, "Evolved Universal Terrestrial Radio Access + (E-UTRA) and Evolved Universal Terrestrial Radio Access + Network (E-UTRAN)", 3GPP TS 36.300 v11.2.0, July 2012. + + [TR-101] Broadband Forum, "Migration to Ethernet-Based Broadband + Aggregation", TR-101 Issue 2, July 2011. + + + + +Key, et al. Informational [Page 11] + +RFC 7387 E-Tree Framework October 2014 + + + [VPMS] Kamite, Y., Jounay, F., Niven-Jenkins, B., Brungard, D., + and L. Jin, "Framework and Requirements for Virtual + Private Multicast Service (VPMS)", Work in Progress, + draft-ietf-l2vpn-vpms-frmwk-requirements-05, + October 2012. + + [EVPN] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., + and J. Uttaro, "BGP MPLS Based Ethernet VPN", Work in + Progress, draft-ietf-l2vpn-evpn-11, October 2014. + +Acknowledgments + + The authors would like to thank Nabil Bitar and Adrian Farrel for + their detailed review and suggestions. + +Contributors + + The following people contributed significantly to this document. + + Yuji Kamite + NTT Communications Corporation + Granpark Tower + 3-4-1 Shibaura, Minato-ku + Tokyo 108-8118, Japan + + EMail: y.kamite@ntt.com + + + Wim Henderickx + Alcatel-Lucent + Copernicuslaan 50 + 2018 Antwerp, Belgium + + EMail: wim.henderickx@alcatel-lucent.com + + + + + + + + + + + + + + + + + +Key, et al. Informational [Page 12] + +RFC 7387 E-Tree Framework October 2014 + + +Authors' Addresses + + Raymond Key (editor) + + EMail: raymond.key@ieee.org + + + Lucy Yong (editor) + Huawei USA + + EMail: lucy.yong@huawei.com + + + Simon Delord + Telstra + + EMail: simon.delord@gmail.com + + + Frederic Jounay + Orange CH + 4 rue caudray 1020 Renens + Switzerland + + EMail: frederic.jounay@orange.ch + + + Lizhong Jin + + EMail: lizho.jin@gmail.com + + + + + + + + + + + + + + + + + + + + + +Key, et al. Informational [Page 13] + |