IETF 79 Proceedings

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Layer 2 Virtual Private Networks (l2vpn) (WG)

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Additional information is available at tools.ietf.org/wg/l2vpn

Chair(s):

Routing Area Director(s):

Routing Area Advisor:

Technical Advisor(s):

Meeting Slides

Internet-Drafts:

Request for Comments:

Charter (as of 2010-11-29)

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). Layer-2 VPN's comprise the following:

1. Virtual Private LAN Service (VPLS) -- A Layer-2 service that emulates
an Ethernet (V)LAN across an IP or an MPLS-enabled IP Packet Switched
Network (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 an IP or
MPLS-enabled IP PSN.

3. Virtual Private Multicast Service (VPMS) -- A Layer 2 service that
Provides point-to-multipoint connectivity for a variety of link
layers, including Frame Relay, ATM, Ethernet, PPP, etc., across an IP or
MPLS-enabled IP PSN.

4. IP-only L2VPN -- A point-to-point or point-to-multipoint "IP-only"
service over an IP or MPLS-enabled PSN. This service is similar to
VPWS because it supports a variety of link-layer protocols on the
Attachment Circuits, including Frame Relay, ATM, Ethernet, PPP, etc.
IP-only L2VPN's are different from both VPLS and VPWS because unicast
Layer-2 frames containing IP data packets, either IPv4 or IPv6, are de-
encapsulated leaving only the IP data packet to be transmitted over
the PSN. An IP-only L2VPN service also differs from L3VPN service,
since no routing protocol operates between the PE and CE;
furthermore, connectivity from CE to CE is provided via an emulated
Layer-2 service over the PSN, which results in the CE's appearing to be
directly attached to each other at Layer-2. The WG will address two
specific types of IP-only L2VPN:

a) Those with Attachment Circuits (ACs) that use the same Layer 2
framing at all attachment points in the same L2VPN; and,

b) Those with ACs that use different Layer 2 framing at various
attachment points in the same L2VPN. For (b), inter-working between
link-layers is strictly out of scope beyond that which is minimally
necessary to ensure that IP packets are transported from an AC of one
type, across the IP or MPLS-enabled IP PSN, and to an AC of another
type in as transparent a manner as possible to the CEs on both sides
of the service.

VPLS, VPWS and VPMS operate over Pseudowires (PWs) as defined by the
PWE3 WG. As with a single PW, an L2VPN emulates a "native" service
over a PSN that is reasonably faithful to, but may not be entirely
indistinguishable from, the native service itself. Further, following
in the "edge-to-edge" nature of the PWs that it uses, the L2VPN WG
will not define any new 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 PW
endpoints which make up the L2VPN.

L2VPN's 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 PE's participating in a VPLS, VPWS or IP-only L2VPN as
well as the membership of CE devices to a specific instance of a L2VPN.

The L2VPN WG will provide extensions of existing protocols that will be
discussed in protocol-specific WG's. In particular, the L2VPN WG
may define extensions to pseudowire management mechanisms (including
OAM), specifically Pseudowire Virtual Circuit Connectivity Verification
(VCCV), for VPLS. Those VCCV extensions will be reviewed by PWE3 to
ensure they are inline with the overall design/architecture of VCCV
and MPLS.

The L2VPN WG will not define new encapsulations, control (set-up,
configuration, maintenance or tear-down), or resiliency mechanisms
specifically related to pseudowires, because those must be defined by
the PWE3 WG. Furthermore, the L2VPN WG will not define protocol inter-
working between a VPLS or VPWS and native service-layer control, OAM or
or resiliency mechanisms, as those will be defined by the PWE3 WG. On
the other hand, the L2VPN WG may define how to operate native service-
layer control, IEEE 802.1 OAM or resiliency mechanisms on top of a VPLS
or VPWS service.

The L2VPN WG scope includes the following:

1. Discovery of PE's participating in a Layer-2 VPN and the associated
topology required for connectivity of the VPLS or VPWS service.

2. Signaling of information related to the discovery and membership of
PE's 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. Once those requirements are
reviewed by the L2VPN WG, they should be provided to the PWE3 WG to
derive solutions.

3. MIB's for Layer-2 VPN solutions.

4. Specification of requirements and framework that will define
Operations Administration and Management (OAM) procedures for VPLS and
VPWS VPN's, related to the operation of VPLS and VPWS VPN's over IP/MPLS
PSN's. In addition, the L2VPN WG will define OAM solutions for VPLS and
VPWS VPN's.

5. Mechanisms to permit optimization of multicast data traffic within
a VPLS or VPWS VPN over an IP/MPLS PSN.

6. Improved service convergence for multi-homed CE's to VPLS PE's.
Specifically, upon failure of a primary path from a CE to VPLS PE,
initiate a rapid switch-over to an alternate path. If required,
interactions with native service-layer resiliency mechanisms will be
provided via solutions from other IETF WG's such as PWE3.

7. Enhancements to increase the scalability of the Control Plane and
Data Plane (e.g.: number of PW's and MAC Forwarding Database,
respectively) of VPLS PE nodes.

8. Define requirements and solutions for Auto-Discovery and Signaling
of Inter-AS VPLS and VPWS L2VPN's, in addition to Inter-AS solutions
for multicast-optimized VPLS and VPMS Layer-2 VPN's.

The L2VPN WG currently works on the following tasks:

- Define MIB's appropriate for each type of Layer-2 VPN.

- Specification of Operations Administration and Management (OAM)
mechanisms for VPLS, VPWS and IP-only VPN's.

- Specification of procedures to permit optimization of L2VPN multicast
data traffic within the PSN.

- Define enhancements to increase scalability of VPLS PE nodes, to
provide aggregation of learned customer MAC addresses at VPLS PE's.

- Identify requirements for multi-homing of CE's to VPLS PE's.
elements. Based on these requirements, define solutions for achieving
fast convergence after a switchover to an alternate path, for example
through optimized MAC flushing within a VPLS domain.

- Identify requirements for Inter-AS VPLS and VPWS services. Define
Inter-AS enhancements to VPLS and VPWS based on these requirements.

- Include extensions to L2VPN protocols and RFC's necessary to create an
MPLS Transport Profile (MPLS-TP). The work on the MPLS TP needs to be
coordinated between four primary working groups (MPLS, PWE3, L2VPN and
CCAMP) that are chartered to do MPLS TP work.

Where necessary, the WG will coordinate its activities with IEEE 802.1
and ITU.

Goals and Milestones:

Done  Submit an I-D describing MIB for VPLS
Done  Submit an I-D describing MIB for VPWS
Done  Submit an I-D on OAM requirements for VPLS
Done  Submit an I-D on OAM requirements for VPWS
Done  Identify VPLS and VPWS solutions for the WG
Done  Submit L2 framework to IESG for publication as Informational RFC
Done  Submit L2 requirements to IESG for publication as Informational RFC
Done  Submit VPLS solution documents to IESG
Done  Submit VPWS solution documents to IESG
Done  Submit Auto-Discovery and Signaling for Intra-AS and Inter-AS VPLS and VPWS Layer-2 VPN's
Nov 2008  Submit IP-only L2VPN solution documents to IESG
Mar 2009  Submit OAM solutions for VPWS to IESG
Mar 2009  Submit OAM solutions for VPLS to IESG
Mar 2009  Submit signaling solution for multicast-optimized VPLS to IESG
Mar 2009  Submit I-D on Virtual Private Multicast Service (VPMS) requirements to IESG
Mar 2009  Submit PIM snooping solution for VPLS to IESG
Mar 2009  Submit OAM solutions for IP-only L2VPN to IESG
Jul 2009  Submit MIB for VPLS to IESG
Jul 2009  Submit MIB for VPWS to IESG
Jul 2009  Submit MIB for IP-only L2VPN to IESG
Nov 2009  Submit scalability solutions for VPLS Data-Plane to IESG
Nov 2009  Submit scalability solutions for VPLS Control-Plane to IESG
Nov 2009  Submit Auto-Discovery solution for VPMS to IESG
Jul 2010  Submit VPLS service convergence improvement solutions to IESG
Jul 2010  Submit VPLS multi-homing solutions to IESG

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