Subject: [PWE3] Second Draft of Charter

From: Danny McPherson <[email-masked]>
Date: Sun, 24 Jul 2005 15:25:03 -0600

Folks,
Here's another draft of the charter incorporating a good bit
of feedback received to date - thanks to everyone who has
contributed.

If you've got feedback on the functional components please let
me know ASAP and I'll attempt to correct.  I'm very much
trying to avoid this being stalled again..

http://pwe3.tcb.net/pwe3-charter-2005072401.txt

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 based
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
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 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 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.

PWE3 will work closely with the L2VPN and L2TPEXT 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 (in order of priority):

Specify the following PW types and consider specification of
additional PW types contingent on WG consensus:

Ethernet, Frame Relay, PPP, HDLC, ATM, low-rate TDM and SONET.

PWE3 may  also specify a  PW type which  can be used for
carrying a user's MPLS packets from one end of the PW to
the other.

In general, PWE3  will not specify mechanisms by which a PW may
connect two  different access services.  However, PWE3  may specify
such mechanisms for the special case where the access  service
payloads at both ends are known to consist entirely of IP packets.

Specify the control and management functions of chartered PW
types, to include PW setup, configuration, maintenance and
tear-down.

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

Enhance packet-based PW specifications as necessary to allow
the emulated service to be carried transparently over the PSN,
for example by the retention of the FCS across the PW.

Define mechanisms to permit the operation of a PW over
a PSN that employs equal cost multiple path (ECMP) packet
switching mechanism.

A PW operating over a shared PSN does not 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.

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

Define the requirements for and mechanisms needed to allow
the operation of switched virtual circuits over a PSN.

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