EVPN Requirements: Requirements for Ethernet VPN (EVPN)

Internet Engineering Task Force (IETF)                        A. Sajassi
Request for Comments: 7209                                         Cisco
Category: Informational                                      R. Aggarwal
ISSN: 2070-1721                                                   Arktan
                                                               J. Uttaro
                                                                    AT&T
                                                                N. Bitar
                                                                 Verizon
                                                           W. Henderickx
                                                          Alcatel-Lucent
                                                                A. Isaac
                                                               Bloomberg
                                                                May 2014


                  Requirements for Ethernet VPN (EVPN)

Abstract

   The widespread adoption of Ethernet L2VPN services and the advent of
   new applications for the technology (e.g., data center interconnect)
   have culminated in a new set of requirements that are not readily
   addressable by the current Virtual Private LAN Service (VPLS)
   solution.  In particular, multihoming with all-active forwarding is
   not supported, and there's no existing solution to leverage
   Multipoint-to-Multipoint (MP2MP) Label Switched Paths (LSPs) for
   optimizing the delivery of multi-destination frames.  Furthermore,
   the provisioning of VPLS, even in the context of BGP-based auto-
   discovery, requires network operators to specify various network
   parameters on top of the access configuration.  This document
   specifies the requirements for an Ethernet VPN (EVPN) solution, which
   addresses the above issues.

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/rfc7209.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Table of Contents

   1. Introduction ....................................................3
   2. Specification of Requirements ...................................4
   3. Terminology .....................................................4
   4. Redundancy Requirements .........................................5
      4.1. Flow-Based Load Balancing ..................................5
      4.2. Flow-Based Multipathing ....................................6
      4.3. Geo-redundant PE Nodes .....................................7
      4.4. Optimal Traffic Forwarding .................................7
      4.5. Support for Flexible Redundancy Grouping ...................8
      4.6. Multihomed Network .........................................8
   5. Multicast Optimization Requirements .............................9
   6. Ease of Provisioning Requirements ...............................9
   7. New Service Interface Requirements .............................10
   8. Fast Convergence ...............................................12
   9. Flood Suppression ..............................................12
   10. Supporting Flexible VPN Topologies and Policies ...............12
   11. Security Considerations .......................................13
   12. Normative References ..........................................13
   13. Informative References ........................................14
   14. Contributors ..................................................15

1.  Introduction

   Virtual Private LAN Service (VPLS), as defined in [RFC4664],
   [RFC4761], and [RFC4762], is a proven and widely deployed technology.
   However, the existing solution has a number of limitations when it
   comes to redundancy, multicast optimization, and provisioning
   simplicity.  Furthermore, new applications are driving several new
   requirements for other L2VPN services such as Ethernet Tree (E-Tree)
   and Virtual Private Wire Service (VPWS).

   In the area of multihoming, current VPLS can only support multihoming
   with the single-active redundancy mode (defined in Section 3), for
   example, as described in [VPLS-BGP-MH].  Flexible multihoming with
   all-active redundancy mode (defined in Section 3) cannot be supported
   by the current VPLS solution.

   In the area of multicast optimization, [RFC7117] describes how
   multicast LSPs can be used in conjunction with VPLS.  However, this
   solution is limited to Point-to-Multipoint (P2MP) LSPs, as there's no
   defined solution for leveraging Multipoint-to-Multipoint (MP2MP) LSPs
   with VPLS.

   In the area of provisioning simplicity, current VPLS does offer a
   mechanism for single-sided provisioning by relying on BGP-based
   service auto-discovery [RFC4761] [RFC6074].  This, however, still
   requires the operator to configure a number of network-side
   parameters on top of the access-side Ethernet configuration.

   In the area of data-center interconnect, applications are driving the
   need for new service interface types that are a hybrid combination of
   VLAN bundling and VLAN-based service interfaces.  These are referred
   to as "VLAN-aware bundling" service interfaces.

   Virtualization applications are also fueling an increase in the
   volume of MAC (Media Access Control) addresses that are to be handled
   by the network; this gives rise to the requirement for having the
   network reconvergence upon failure be independent of the number of
   MAC addresses learned by the Provider Edge (PE).

   There are requirements for minimizing the amount of flooding of
   multi-destination frames and localizing the flooding to the confines
   of a given site.

   There are also requirements for supporting flexible VPN topologies
   and policies beyond those currently covered by VPLS and Hierarchical
   VPLS (H-VPLS).

   The focus of this document is on defining the requirements for a new
   solution, namely, Ethernet VPN (EVPN), which addresses the above
   issues.

   Section 4 discusses the redundancy requirements.  Section 5 describes
   the multicast optimization requirements.  Section 6 articulates the
   ease of provisioning requirements.  Section 7 focuses on the new
   service interface requirements.  Section 8 highlights the fast
   convergence requirements.  Section 9 describes the flood suppression
   requirement, and finally Section 10 discusses the requirements for
   supporting flexible VPN topologies and policies.

2.  Specification of Requirements

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   This document is not a protocol specification and the key words in
   this document are used for clarity and emphasis of requirements
   language.

3.  Terminology

   AS: Autonomous System

   CE: Customer Edge

   E-Tree: Ethernet Tree

   MAC address: Media Access Control address - referred to as MAC

   LSP: Label Switched Path

   PE: Provider Edge

   MP2MP: Multipoint to Multipoint

   VPLS: Virtual Private LAN Service

   Single-Active Redundancy Mode: When a device or a network is
   multihomed to a group of two or more PEs and when only a single PE in
   such a redundancy group can forward traffic to/from the multihomed
   device or network for a given VLAN, such multihoming is referred to
   as "Single-Active".

   All-Active Redundancy Mode: When a device is multihomed to a group of
   two or more PEs and when all PEs in such redundancy group can forward
   traffic to/from the multihomed device or network for a given VLAN,
   such multihoming is referred to as "All-Active".

4.  Redundancy Requirements

4.1.  Flow-Based Load Balancing

   A common mechanism for multihoming a CE node to a set of PE nodes
   involves leveraging multi-chassis Ethernet link aggregation groups
   (LAGs) based on [802.1AX].  [PWE3-ICCP] describes one such scheme.
   In Ethernet link aggregation, the load-balancing algorithms by which
   a CE distributes traffic over the Attachment Circuits connecting to
   the PEs are quite flexible.  The only requirement is for the
   algorithm to ensure in-order frame delivery for a given traffic flow.
   In typical implementations, these algorithms involve selecting an
   outbound link within the bundle based on a hash function that
   identifies a flow based on one or more of the following fields:

   i.   Layer 2: Source MAC Address, Destination MAC Address, VLAN
   ii.  Layer 3: Source IP Address, Destination IP Address
   iii. Layer 4: UDP or TCP Source Port, Destination Port

   A key point to note here is that [802.1AX] does not define a standard
   load-balancing algorithm for Ethernet bundles, and, as such,
   different implementations behave differently.  As a matter of fact, a
   bundle operates correctly even in the presence of asymmetric load
   balancing over the links.  This being the case, the first requirement
   for all-active multihoming is the ability to accommodate flexible
   flow-based load balancing from the CE node based on L2, L3, and/or L4
   header fields.

   (R1a) A solution MUST be capable of supporting flexible flow-based
         load balancing from the CE as described above.

   (R1b) A solution MUST also be able to support flow-based load
         balancing of traffic destined to the CE, even when the CE is
         connected to more than one PE.  Thus, the solution MUST be able
         to exercise multiple links connected to the CE, irrespective of
         the number of PEs that the CE is connected to.

   It should be noted that when a CE is multihomed to several PEs, there
   could be multiple Equal-Cost Multipath (ECMP) paths from each remote
   PE to each multihoming PE.  Furthermore, for an all-active multihomed
   CE, a remote PE can choose any of the multihoming PEs for sending
   traffic destined to the multihomed CE.  Therefore, when a solution
   supports all-active multihoming, it MUST exercise as many of these
   paths as possible for traffic destined to a multihomed CE.

   (R1c) A solution SHOULD support flow-based load balancing among PEs
         that are members of a redundancy group spanning multiple
         Autonomous Systems.

4.2.  Flow-Based Multipathing

   Any solution that meets the all-active redundancy mode (e.g., flow-
   based load balancing) described in Section 4.1, also needs to
   exercise multiple paths between a given pair of PEs.  For instance,
   if there are two or more LSPs between a remote PE and a pair of PEs
   in an all-active redundancy group, then the solution needs to be
   capable of load balancing traffic among those LSPs on a per-flow
   basis for traffic destined to the PEs in the redundancy group.
   Furthermore, if there are two or more ECMP paths between a remote PE
   and one of the PEs in the redundancy group, then the solution needs
   to leverage all the equal-cost LSPs.  For the latter, the solution
   can also leverage the load-balancing capabilities based on entropy
   labels [RFC6790].

   (R2a) A solution MUST be able to exercise all LSPs between a remote
         PE and all the PEs in the redundancy group with all-active
         multihoming.

   (R2b) A solution MUST be able to exercise all ECMP paths between a
         remote PE and any of the PEs in the redundancy group with all-
         active multihoming.

   For example, consider a scenario in which CE1 is multihomed to PE1
   and PE2, and CE2 is multihomed to PE3 and PE4 running in all-active
   redundancy mode.  Furthermore, consider that there exist three ECMP
   paths between any of the CE1's and CE2's multihomed PEs.  Traffic
   from CE1 to CE2 can be forwarded on twelve different paths over the
   MPLS/IP core as follows: CE1 load balances traffic to both PE1 and
   PE2.  Each of PE1 and PE2 have three ECMP paths to PE3 and PE4 for a
   total of twelve paths.  Finally, when traffic arrives at PE3 and PE4,
   it gets forwarded to CE2 over the Ethernet channel (aka link bundle).

   It is worth pointing out that flow-based multipathing complements
   flow-based load balancing described in the previous section.

4.3.  Geo-redundant PE Nodes

   The PE nodes offering multihomed connectivity to a CE or access
   network may be situated in the same physical location (co-located),
   or may be spread geographically (e.g., in different Central Offices
   (COs) or Points of Presence (POPs)).  The latter is needed when
   offering a geo-redundant solution that ensures business continuity
   for critical applications in the case of power outages, natural
   disasters, etc.  An all-active multihoming mechanism needs to support
   both co-located as well as geo-redundant PE placement.  The latter
   scenario often means that requiring a dedicated link between the PEs,
   for the operation of the multihoming mechanism, is not appealing from
   a cost standpoint.  Furthermore, the IGP cost from remote PEs to the
   pair of PEs in the dual-homed setup cannot be assumed to be the same
   when those latter PEs are geo-redundant.

   (R3a) A solution MUST support all-active multihoming without the need
         for a dedicated control/data link among the PEs in the
         multihomed group.

   (R3b) A solution MUST support different IGP costs from a remote PE to
         each of the PEs in a multihomed group.

   (R3c) A solution MUST support multihoming across different IGP
         domains within the same Autonomous System.

   (R3d) A solution SHOULD support multihoming across multiple
         Autonomous Systems.

4.4.  Optimal Traffic Forwarding

   In a typical network, when considering a designated pair of PEs, it
   is common to find both single-homed as well as multihomed CEs being
   connected to those PEs.

   (R4)  An all-active multihoming solution SHOULD support optimal
         forwarding of unicast traffic for all the following scenarios.
         By "optimal forwarding", we mean that traffic will not be
         forwarded between PE devices that are members of a multihomed
         group unless the destination CE is attached to one of the
         multihoming PEs.

         i.   single-homed CE to multihomed CE
         ii.  multihomed CE to single-homed CE
         iii. multihomed CE to multihomed CE

   This is especially important in the case of geo-redundant PEs, where
   having traffic forwarded from one PE to another within the same
   multihomed group introduces additional latency, on top of the
   inefficient use of the PE node's and core nodes' switching capacity.
   A multihomed group (also known as a multi-chassis LAG) is a group of
   PEs supporting a multihomed CE.

4.5.  Support for Flexible Redundancy Grouping

   (R5) In order to support flexible redundancy grouping, the
         multihoming mechanism SHOULD allow arbitrary grouping of PE
         nodes into redundancy groups where each redundancy group
         represents all multihomed devices/networks that share the same
         group of PEs.

   This is best explained with an example: consider three PE nodes --
   PE1, PE2, and PE3.  The multihoming mechanism MUST allow a given PE,
   say, PE1, to be part of multiple redundancy groups concurrently.  For
   example, there can be a group (PE1, PE2), a group (PE1, PE3), and
   another group (PE2, PE3) where CEs could be multihomed to any one of
   these three redundancy groups.

4.6.  Multihomed Network

   There are applications that require an Ethernet network, rather than
   a single device, to be multihomed to a group of PEs.  The Ethernet
   network would typically run a resiliency mechanism such as Multiple
   Spanning Tree Protocol [802.1Q] or Ethernet Ring Protection Switching
   [G.8032].  The PEs may or may not participate in the control protocol
   of the Ethernet network.  For a multihomed network running [802.1Q]
   or [G.8032], these protocols require that each VLAN to be active only
   on one of the multihomed links.

   (R6a) A solution MUST support multihomed network connectivity with
         single-active redundancy mode where all VLANs are active on one
         PE.

   (R6b) A solution MUST also support multihomed networks with single-
         active redundancy mode where disjoint VLAN sets are active on
         disparate PEs.

   (R6c) A solution SHOULD support single-active redundancy mode among
         PEs that are members of a redundancy group spanning multiple
         ASes.

   (R6d) A solution MAY support all-active redundancy mode for a
         multihomed network with MAC-based load balancing (i.e.,
         different MAC addresses on a VLAN are reachable via different
         PEs).

5.  Multicast Optimization Requirements

   There are environments where the use of MP2MP LSPs may be desirable
   for optimizing multicast, broadcast, and unknown unicast traffic in
   order to reduce the amount of multicast states in the core routers.
   [RFC7117] precludes the use of MP2MP LSPs since current VPLS
   solutions require an egress PE to perform learning when it receives
   unknown unicast packets over an LSP.  This is challenging when MP2MP
   LSPs are used, as they do not have inherent mechanisms to identify
   the sender.  The use of MP2MP LSPs for multicast optimization becomes
   tractable if the need to identify the sender for performing learning
   is lifted.

   (R7a) A solution MUST be able to provide a mechanism that does not
         require MAC learning against MPLS LSPs when packets are
         received over a MP2MP LSP.

   (R7b) A solution SHOULD be able to provide procedures to use MP2MP
         LSPs for optimizing delivery of multicast, broadcast, and
         unknown unicast traffic.

6.  Ease of Provisioning Requirements

   As L2VPN technologies expand into enterprise deployments, ease of
   provisioning becomes paramount.  Even though current VPLS has an
   auto-discovery mechanism, which enables automated discovery of member
   PEs belonging to a given VPN instance over the MPLS/IP core network,
   further simplifications are required, as outlined below:

   (R8a) The solution MUST support auto-discovery of VPN member PEs over
         the MPLS/IP core network, similar to the VPLS auto-discovery
         mechanism described in [RFC4761] and [RFC6074].

   (R8b) The solution SHOULD support auto-discovery of PEs belonging to
         a given redundancy or multihomed group.

   (R8c) The solution SHOULD support auto-sensing of the site ID for a
         multihomed device or network and support auto-generation of the
         redundancy group ID based on the site ID.

   (R8d) The solution SHOULD support automated Designated Forwarder (DF)
         election among PEs participating in a redundancy (multihoming)
         group and be able to divide service instances (e.g., VLANs)
         among member PEs of the redundancy group.

   (R8e) For deployments where VLAN identifiers are global across the
         MPLS network (i.e., the network is limited to a maximum of 4K
         services), the PE devices SHOULD derive the MPLS-specific
         attributes (e.g., VPN ID, BGP Route Target, etc.) from the VLAN
         identifier.  This way, it is sufficient for the network
         operator to configure the VLAN identifier(s) for the access
         circuit, and all the MPLS and BGP parameters required for
         setting up the service over the core network would be
         automatically derived without any need for explicit
         configuration.

   (R8f) Implementations SHOULD revert to using default values for
         parameters for which no new values are configured.

7.  New Service Interface Requirements

   [MEF] and [802.1Q] have the following services specified:

   -  Port mode: in this mode, all traffic on the port is mapped to a
      single bridge domain and a single corresponding L2VPN service
      instance.  Customer VLAN transparency is guaranteed end to end.

   -  VLAN mode: in this mode, each VLAN on the port is mapped to a
      unique bridge domain and corresponding L2VPN service instance.
      This mode allows for service multiplexing over the port and
      supports optional VLAN translation.

   -  VLAN bundling: in this mode, a group of VLANs on the port are
      collectively mapped to a unique bridge domain and corresponding
      L2VPN service instance.  Customer MAC addresses must be unique
      across all VLANs mapped to the same service instance.

   For each of the above services, a single bridge domain is assigned
   per service instance on the PE supporting the associated service.
   For example, in case of the port mode, a single bridge domain is
   assigned for all the ports belonging to that service instance,
   regardless of the number of VLANs coming through these ports.

   It is worth noting that the term 'bridge domain' as used above refers
   to a MAC forwarding table as defined in the IEEE bridge model and
   does not denote or imply any specific implementation.

   [RFC4762] defines two types of VPLS services based on "unqualified
   and qualified learning", which in turn maps to port mode and VLAN
   mode, respectively.

   (R9a) A solution MUST support the above three service types (port
         mode, VLAN mode, and VLAN bundling).

   For hosted applications for data-center interconnect, network
   operators require the ability to extend Ethernet VLANs over a WAN
   using a single L2VPN instance while maintaining data-plane separation
   between the various VLANs associated with that instance.  This is
   referred to as 'VLAN-aware bundling service'.

   (R9b) A solution MAY support VLAN-aware bundling service.

   This gives rise to two new service interface types: VLAN-aware
   bundling without translation and VLAN-aware bundling with
   translation.

   The service interface for VLAN-aware bundling without translation has
   the following characteristics:

   -  The service interface provides bundling of customer VLANs into a
      single L2VPN service instance.

   -  The service interface guarantees customer VLAN transparency end to
      end.

   -  The service interface maintains data-plane separation between the
      customer VLANs (i.e., creates a dedicated bridge-domain per VLAN).

   In the special case of all-to-one bundling, the service interface
   must not assume any a priori knowledge of the customer VLANs.  In
   other words, the customer VLANs shall not be configured on the PE;
   rather, the interface is configured just like a port-based service.

   The service interface for VLAN-aware bundling with translation has
   the following characteristics:

   -  The service interface provides bundling of customer VLANs into a
      single L2VPN service instance.

   -  The service interface maintains data-plane separation between the
      customer VLANs (i.e., creates a dedicated bridge-domain per VLAN).

   -  The service interface supports customer VLAN ID translation to
      handle the scenario where different VLAN Identifiers (VIDs) are
      used on different interfaces to designate the same customer VLAN.

   The main difference, in terms of service-provider resource
   allocation, between these new service types and the previously
   defined three types is that the new services require several bridge
   domains to be allocated (one per customer VLAN) per L2VPN service
   instance as opposed to a single bridge domain per L2VPN service
   instance.

8.  Fast Convergence

   (R10a) A solution MUST provide the ability to recover from PE-CE
          attachment circuit failures as well as PE node failure for the
          cases of both multihomed device and multihomed network.

   (R10b) The recovery mechanism(s) MUST provide convergence time that
          is independent of the number of MAC addresses learned by the
          PE.  This is particularly important in the context of
          virtualization applications, which are fueling an increase in
          the number of MAC addresses to be handled by the Layer 2
          network.

   (R10c) Furthermore, the recovery mechanism(s) SHOULD provide
          convergence time that is independent of the number of service
          instances associated with the attachment circuit or the PE.

9.  Flood Suppression

   (R11a) The solution SHOULD allow the network operator to choose
          whether unknown unicast frames are to be dropped or to be
          flooded.  This attribute needs to be configurable on a per-
          service-instance basis.

   (R11b) In addition, for the case where the solution is used for data-
          center interconnect, the solution SHOULD minimize the flooding
          of broadcast frames outside the confines of a given site.  Of
          particular interest is periodic Address Resolution Protocol
          (ARP) traffic.

   (R11c) Furthermore, the solution SHOULD eliminate any unnecessary
          flooding of unicast traffic upon topology changes, especially
          in the case of a multihomed site where the PEs have a priori
          knowledge of the backup paths for a given MAC address.

10.  Supporting Flexible VPN Topologies and Policies

   (R12a) A solution MUST be capable of supporting flexible VPN
          topologies that are not constrained by the underlying
          mechanisms of the solution.

   One example of this is E-Tree topology, where one or more sites in
   the VPN are roots and the others are leaves.  The roots are allowed
   to send traffic to other roots and to leaves, while leaves can
   communicate only with the roots.  The solution MUST provide the
   ability to support E-Tree topology.

   (R12b) The solution MAY provide the ability to apply policies at the
          granularity of the MAC address to control which PEs in the VPN
          learn which MAC address and how a specific MAC address is
          forwarded.  It should be possible to apply policies to allow
          only some of the member PEs in the VPN to send or receive
          traffic for a particular MAC address.

   (R12c) A solution MUST be capable of supporting both inter-AS
          option-C and inter-AS option-B scenarios as described in
          [RFC4364].

11.  Security Considerations

   Any protocol extensions developed for the EVPN solution shall include
   the appropriate security analysis.  Besides the security requirements
   covered in [RFC4761] and [RFC4762] when MAC learning is performed in
   data-plane and in [RFC4364] when MAC learning is performed in control
   plane, the following additional requirements need to be covered.

   (R13) A solution MUST be capable of detecting and properly handling a
         situation where the same MAC address appears behind two
         different Ethernet segments (whether inadvertently or
         maliciously).

   (R14) A solution MUST be capable of associating a MAC address to a
         specific Ethernet segment (aka "sticky MAC") in order to help
         limit malicious traffic into a network for that MAC address.
         This capability can limit the appearance of spoofed MAC
         addresses on a network.  When this feature is enabled, the MAC
         mobility for such sticky MAC addresses are disallowed, and the
         traffic for such MAC addresses from any other Ethernet segment
         MUST be discarded.

12.  Normative References

   [802.1AX]  IEEE, "IEEE Standard for Local and metropolitan area
              networks - Link Aggregation", Std. 802.1AX-2008, IEEE
              Computer Society, November 2008.

   [802.1Q]   IEEE, "IEEE Standard for Local and metropolitan area
              networks - Virtual Bridged Local Area Networks", Std.
              802.1Q-2011, 2011.

   [G.8032]   ITU-T, "Ethernet ring protection switching", ITU-T
              Recommendation G.8032, February 2012.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4364]  Bersani, F. and H. Tschofenig, "The EAP-PSK Protocol: A
              Pre-Shared Key Extensible Authentication Protocol (EAP)
              Method", RFC 4764, January 2007.

   [RFC4761]  Kompella, K., Ed., and Y. Rekhter, Ed., "Virtual Private
              LAN Service (VPLS) Using BGP for Auto-Discovery and
              Signaling", RFC 4761, January 2007.

   [RFC4762]  Lasserre, M., Ed., and V. Kompella, Ed., "Virtual Private
              LAN Service (VPLS) Using Label Distribution Protocol (LDP)
              Signaling", RFC 4762, January 2007.

   [RFC6074]  Rosen, E., Davie, B., Radoaca, V., and W. Luo,
              "Provisioning, Auto-Discovery, and Signaling in Layer 2
              Virtual Private Networks (L2VPNs)", RFC 6074, January
              2011.

13.  Informative References

   [VPLS-BGP-MH]
              Kothari, B., Kompella, K., Henderickx, W., Balue, F.,
              Uttaro, J., Palislamovic, S., and W. Lin, "BGP based
              Multi-homing in Virtual Private LAN Service", Work in
              Progress, July 2013.

   [PWE3-ICCP]
              Martini, L., Salam, S., Sajassi, A., and S. Matsushima,
              "Inter-Chassis Communication Protocol for L2VPN PE
              Redundancy", Work in Progress, March 2014.

   [MEF]      Metro Ethernet Forum, "Ethernet Service Definitions", MEF
              6.1 Technical Specification, April 2008.

   [RFC4664]  Andersson, L., Ed., and E. Rosen, Ed., "Framework for
              Layer 2 Virtual Private Networks (L2VPNs)", RFC 4664,
              September 2006.

   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, November 2012.

   [RFC7117]  Aggarwal, R., Ed., Kamite, Y., Fang, L., Rekhter, Y., and
              C. Kodeboniya, "Multicast in Virtual Private LAN Service
              (VPLS)", RFC 7117, February 2014.

14.  Contributors

   Samer Salam, Cisco, ssalam@cisco.com
   John Drake, Juniper, jdrake@juniper.net
   Clarence Filsfils, Cisco, cfilsfil@cisco.com

Authors' Addresses

   Ali Sajassi
   Cisco
   EMail: sajassi@cisco.com


   Rahul Aggarwal
   Arktan
   EMail: raggarwa_1@yahoo.com


   James Uttaro
   AT&T
   EMail: uttaro@att.com


   Nabil Bitar
   Verizon Communications
   EMail: nabil.n.bitar@verizon.com


   Wim Henderickx
   Alcatel-Lucent
   EMail: wim.henderickx@alcatel-lucent.com


   Aldrin Isaac
   Bloomberg
   EMail: aisaac71@bloomberg.net