Subject: [PWE3] PWE3 Charter - updated

From: Danny McPherson <[email-masked]>
Date: Mon, 10 Oct 2005 15:52:18 -0600

Folks,
Another cut of the charter incorporating all feedback to date.  Note
that the one item I've not updated as of yet is the objective that is
encompassed in the last sentence of the charter:

"Define requirements for and mechanisms to provide
interconnection of PWs (to include inter-domain PWs)."

This text was meant to include both multi-segment PWs, as
well as inter-domain PWs, without being overly constraining
(or overly verbose).  I'm inclined not to change this much, if
at all, unless provided a compelling reason why it's insufficient
- and some recommended alternative text.

Thanks!

-danny

-----------------------
Pseudo Wire Emulation Edge to Edge (PWE3) WG

Description of Working Group:

Network transport service providers and their users are
seeking to rationalize their networks by migrating their
existing services and platforms onto IP or MPLS enabled
IP packet switched networks (PSN).  This migration requires
communications services that can emulate the essential
properties of traditional communications links over a PSN.

Pseudowire Emulation Edge to Edge (PWE3) will specify the
encapsulation, transport, control, management, interworking and
security of services emulated over IETF specified PSNs.

A pseudowire emulates a point-to-point link, and provides a
single service which is perceived by its user as an unshared
link or circuit of the chosen service.  It is not intended that
an emulated service will be indistinguishable from the service
that is being emulated.  The emulation need only be sufficient
for the satisfactory operation of the service.  Emulation
necessarily involves a degree of cost-performance trade-off.
In some cases it may be necessary to design more than one
emulation mechanism in order to resolve these design
conflicts.  All emulated service definitions must include an
applicability statement describing the faithfulness of the
emulation.  Switching, multiplexing, modification or other
operation on the traditional service, unless required as
part of the emulation, is out of the scope of the PWE3 WG.

PWE3 will make use of existing IETF specified mechanisms
unless there are technical reasons why the existing mechanisms
are insufficient or unnecessary.

PWE3 operates "edge to edge" and will not exert control on
the underlying PSN, other than to use any existing QoS or
path control mechanism to provide the required connectivity
between the two endpoints of the PW.

PWE3 will investigate mechanisms necessary to perform clock
recovery and other real-time signaling functions.  This work will
be coordinated with the AVT WG and RTP will be used where
appropriate.

A PW operating over a shared PSN does not necessarily have
the same intrinsic security as a dedicated, purpose built,
network.  In some cases this is satisfactory, while in other
cases it will be necessary to enhance the security of the PW
to emulate the intrinsic security of the emulated service.
PW specifications MUST include a description of how they
are to be operated over a shared PSN with adequate security.

Whilst a service provider may traffic engineer their network
in such a way that PW traffic will not cause significant
congestion, a PW deployed by an end-user may cause
congestion of the underlying PSN.  Suitable congestion
avoidance mechanisms are therefore needed to protect the
Internet from the unconstrained deployment of PWs.

PWE3 will work closely with the L2VPN WG to ensure a clear
demarcation is defined for where PWE3 stops and L2VPN starts.
PWE3 will coordinate very closely with any WG that is
responsible for protocols which PWE3 intends to extend (e.g.,
the MPLS WG for LDP), as well as foster interaction with WGs
that intend to extend PWE3 protocols.

WG Objectives:

Specify the following PW types:

Ethernet, Frame Relay, PPP, HDLC, ATM, low-rate TDM,
SONET/SDH and Fibre Channel.

PWE3 will specify a PW type for the special case where the
access service payloads at both ends are known to consist
entirely of IP packets.  PWE3 will not specify mechanisms
by which a PW connects two different access services.

Specify the control and management functions of chartered PW
types, to include PW setup, configuration, maintenance and
tear-down.  The PWE3 WG will do this in its entirety for
MPLS PSNs, and the L2TPEXT WG will develop the L2TP specifics
for L2TPv3-based PWs.

Specify Operations and Management (OAM) mechanisms for all
PW types, suitable for operation over both IP/L2TPv3 and
MPLS PSNs, and capable of providing the necessary
interworking with the OAM mechanisms of the emulated
service.

Further enhance PW specifications to enable more transparent
emulation when necessary, for example the retention of FCS
across a PW.

Define a mechanism for MPLS PWs that provides interoperability
with currently deployed equal cost multiple path (ECMP)
algorithms such that packets for a given PW follow the same
path through an MPLS PSN.

Define requirements for and mechanisms to provide
interconnection of PWs (to include inter-domain PWs).

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