Layer 2 Virtual Private Networks

Document Charter Layer 2 Virtual Private Networks WG (l2vpn)
Title Layer 2 Virtual Private Networks
Last updated 2003-07-03
State Approved
WG State Concluded
IESG Responsible AD Adrian Farrel
Charter Edit AD (None)
Send notices to (None)


The L2VPN working group is responsible for defining and specifying a
  limited number of solutions for supporting provider-provisioned Layer-2
  Virtual Private Networks (L2VPNs). It will also address requirements 
  driven by cloud computing services and data centers as they apply to 
  Layer-2 VPN services.
  Layer-2 VPNs defined by L2VPN operate over pseudowires (PWs) as
  defined by the PWE3 WG or over IP or MPLS PSN tunnels. A L2VPN
  emulates a "native" service over a PSN that is adequately faithful
  to, but may not be entirely indistinguishable from the native
  service itself. Further, following in the "edge-to-edge" nature
  of the  service, the L2VPN WG will not define any mechanisms
  which exert control over the underlying PSN. When necessary it
  may, however, recommend or require the use of existing PSN QoS
  and path control mechanisms between the PEs which provide the
  L2VPN connectivity.
  Layer-2 VPNs comprise the following:
  1. Virtual Private LAN Service (VPLS) -- A Layer-2 service
  that emulates a switched Ethernet (V)LAN across a PSN.
  2. Virtual Private Wire Service (VPWS) -- A Layer-2 service that
  provides point-to-point connectivity for a variety of link layers,
  including Frame Relay, ATM, Ethernet, PPP, etc., across a PSN.
  3. Virtual Private Multicast Service (VPMS) -- A Layer-2 service that
  provides point-to-multipoint connectivity for a variety of link
  layers across a PSN.
  4. IP-only L2VPN, an IP-only service over a PSN.  The WG will address
  two specific types of IP-only L2VPN:
  a) Point-to-point Layer-2 VPN.  This service is similar to VPWS, but 
  also supports heterogenous Attachment Circuits at either end
  of a single point-to-point service.
  b) Multipoint-to-multipoint Layer-2 VPN.  This service is similar
  to VPLS, but learns IP and MAC address bindings from ARPs and
  broadcast/multicast IP packets.
  5. Ethernet VPN (E-VPN) - An enhanced Layer-2 service that
  emulates an Ethernet (V)LAN across a PSN. E-VPN supports
  load-sharing across multiple connections from a Layer-2 site
  to an L2VPN service. E-VPN is primarily targeted to support
  large-scale L2VPNs with resiliency requirements not satisfied
  by other L2VPN solutions.
  6. E-Tree, a Layer-2 service defined by the MEF, which provides
  connectivity between one or more root nodes and one or more leaf
  nodes, with the restriction that leaf nodes may only communicate
  with root node(s) (and not with each other).
  L2VPNs will make use of existing IETF specified mechanisms
  unless there are technical reasons why the existing mechanisms
  are insufficient or unnecessary.
  The L2VPN WG is responsible for specification of the
  discovery and membership of PEs participating in a Layer-2
  VPN as well as the membership of CE devices for a specific
  instance of an L2VPN.
  The L2VPN WG will provide extensions of existing protocols
  that will be discussed in protocol-specific WGs. In
  particular, the L2VPN WG may define extensions to pseudowire
  management mechanisms for VPLS. Those extensions will
  be reviewed by the PWE3 WG to ensure they are aligned
  with the overall design/architecture of PWE3.
  The L2VPN WG will not define new encapsulations, control,
  or resiliency mechanisms specifically related to pseudowires. 
  Furthermore, when the L2VPN solution is based on PWs, the
  L2VPN WG will not define protocol inter-working between
  an L2VPN and native service Layer-2 OAM or resiliency
  mechanisms. The L2VPN WG may define how to operate native
  service-layer control, OAM or resiliency mechanisms on
  top of an L2VPN. In addition, it may define native data
  plane and/or control plane interworking between an
  L2VPN and an associated native Layer-2 service.
  The L2VPN WG scope includes the following:
  1. Discovery of PEs participating in a Layer-2 VPN and the
  associated topology required for connectivity of the VPLS,
  VPWS, VPMS or E-VPN service.
  2. Signaling of information related to the discovery and
  membership of PEs within a L2VPN. These procedures must
  use PWE3 control and management procedures, or define
  requirements for extensions of PWE3 protocols to suit
  the needs of an L2VPN, when the L2VPN operates over PWs.
  Once those requirements have been reviewed by the L2VPN WG,
  they should be provided to the PWE3 WG to derive solutions.
  3. MIBs for Layer-2 VPN solutions.
  4. Specification of requirements, framework and solutions
  that facilitate Operations Administration and Management
  (OAM) of any type of L2VPN within the scope of the L2VPN
  Working Group.
  5. Mechanisms to permit optimization of multicast data
  traffic within an L2VPN.
  6. If transport does not involve PWs, mechanisms that
  support load-balancing/multi-pathing between PEs
  interconnecting a Layer-2 service using an L2VPN across
  the PSN.
  7. requirements for the multi-homing of CEs to several
  VPLS or E-VPN PEs, inclusive of active/backup and active/
  active (load-sharing) configurations. Based on these
  requirements define VPLS or E-VPN control plane
  solutions for achieving fast convergence after failure
  of an active path in the PSN or on the AC side.
  8. Enhancements to increase the scalability of the Control
  Plane and Data Plane of L2VPN PE nodes, and of core nodes
  that provide transport services for L2VPN.
  9. Requirements and solutions for Auto-Discovery and
  Signaling of Inter-AS L2VPNs, in addition to Inter-AS
  solutions for multicast-optimized L2VPNs.
  10. Requirements and solutions for supporting "E-Tree"
  services using VPLS.