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Pseudowire And LDP-enabled Services

Document Charter Pseudowire And LDP-enabled Services WG (pals)
Title Pseudowire And LDP-enabled Services
Last updated 2022-03-23
State Approved
WG State Active
IESG Responsible AD Andrew Alston
Charter edit AD Andrew Alston
Send notices to (None)

Many services that run in the Internet are facilitated in MPLS networks
by the Label Distribution Protocol (LDP) and/or are established over
pseudowires that emulate point-to-point or point-to-multipoint links and
provide communication connectivity that is perceived by its users as an
unshared link or circuit of an emulated Layer-1, Layer-2, or Layer-3 
service type.

Layer-2 Virtual Private Networks (L2VPNs) are one such service that 
provides an emulation of a "native" service over a packet switched
network that is adequately faithful to, but may not be entirely 
indistinguishable from, the native service itself. 

The Pseudowire And LDP-enabled Services (PALS) working group is
chartered to define, specify, and extend network services based on
pseudowires and/or signaled using LDP.

In particular, the working group will work on the following services:

- All types of MPLS-based and L2TPv3-based pseudowire services
  including point-to-point and point-to-multipoint pseudowires, single
  segment and multi-segment pseudowires, single and multi-domain
  pseudowires, and signaled and statically provisioned pseudowires.

- All types of dynamic or static provider-provisioned L2VPNs that
  operate over pseudowires or that are enabled over MPLS networks
  using LDP as a control plane mechanism.

- IP-only L2VPN solutions (for IP-only services over a packet switched

The working group may also suggest new services to be supported by LDP
or pseudowires and these may be added to the working group charter
subject to re-chartering. The working group is also responsible for the
maintenance and development of pseudowires formerly carried out by the
PWE3 working group

The PALS working group will not define any mechanisms that exert control
over the underlying packet switched network. When necessary it may, 
however, recommend or require the use of existing QoS and path control
mechanisms between the edge nodes that provide the connectivity to the

The working group may work on:

- New pseudowire encapsulations or types for services emulated over 
  IETF-specified Packet Switched Networks.

- Operations, Administration, and Management (OAM) for pseudowires 
  including interworking of OAM for pseudowires and native services, and
  OAM for other services worked on by PALS (including L2VPNs). But new 
  techniques should be shared with the BFD and MPLS working groups to 
  ensure consistency with existing OAM techniques, and with the LIME 
  working group to provide for consistency of operation.

- Protocol extensions for LDP in support of new pseudowire function
  and new services, but all protocol extensions must be reviewed by the
  MPLS working group which is responsible for the consistency and
  stability of LDP.

- Mechanisms to enhance pseudowire and L2VPN functionality by 
  including security, protection and restoration, congestion avoidance,
  and load balancing across parallel packet switched tunnels.

- Mechanisms to permit optimization of multicast data traffic within an

- Enhancements to increase the scalability of the control plane and data
  plane of L2VPN solutions and application of L2VPN solutions in the 
  data center, the latter in coordination with the NVO3 working group

- L2VPN discovery and membership mechanisms that utilize pseudowire
  control and management procedures.

- Data models for modeling, managing, and operating the services worked
  on by the PALS working group using SMI or YANG.

The PALS working group will not work on L2VPNs enabled using BGP, and
where L2VPNs that are within the scope of the PALS working group use
BGP to add functionality (for example for discovery of membership of a
VPN) this work will be coordinated with the BESS working group. This
also includes work on particular types of L2VPNs that support both LDP
and BGP signaling, such as VPLS. Any contention between these working
groups on the placement of such work will be resolved by the chairs.

The PALS working group will coordinate closely with the MPLS working
group for all work involving LDP and the MPLS data plane. It will also
coordinate with the MPLS working group in developing shared security,
and with the BFD and MPLS working groups on OAM solutions.

Where extensions to pseudowires are needed to support time or frequency
transfer, this work will be done by the PALS working group in 
consultation with the TICTOC working group.

L2TP specifics of L2TPv3-based pseudowires will continue to be the
responsibility of the L2TPEXT working group.