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Versions: (draft-malis-pwe3-cell-transport) 00 01 02 03 04 05 06 RFC 4816

   PWE3 Working Group
   Internet Draft                                              A. Malis
   draft-ietf-pwe3-cell-transport-06.txt                        Tellabs
   Expires: April 2007                                       L. Martini
                                                          Cisco Systems
                                                             J. Brayley
                                                            ECI Telecom
                                                               T. Walsh
                                                       Juniper Networks
                                                           October 2006


                PWE3 ATM Transparent Cell Transport Service


IPR Statement

    By submitting this Internet-Draft, each author represents that any
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Abstract

   The document describes a transparent cell transport service that
   makes use of the "N-to-one" cell relay mode for PWE3 ATM cell
   encapsulation.

Specification of Requirements

    The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
    "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
    this document are to be interpreted as described in RFC 2119 [1].


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 1. Intellectual Property Statement

    The IETF takes no position regarding the validity or scope of any
    Intellectual Property Rights or other rights that might be claimed
    to pertain to the implementation or use of the technology
    described in this document or the extent to which any license
    under such rights might or might not be available; nor does it
    represent that it has made any independent effort to identify any
    such rights. Information on the procedures with respect to rights
    in RFC documents can be found in BCP 78 and BCP 79.

    Copies of IPR disclosures made to the IETF Secretariat and any
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    The IETF invites any interested party to bring to its attention
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2. Introduction

   This transparent cell transport service allows migration of ATM
   services to a PSN without having to provision the ATM subscriber or
   customer edge (CE) devices.  The ATM CEs will view the ATM
   transparent cell transport service as if they were directly connected
   via a TDM leased line.  This service is most likely to be used as an
   internal function in a ATM service provider's network as a way to
   connect existing ATM switches via a higher speed PSN, or to provide
   ATM "backhaul" services for remote access to existing ATM networks.

3. Transparent Cell Transport Definition

   The transparent port service is a natural application of the "N-to-
   one" VCC cell transport mode for PWE3 ATM encapsulation described in
   [2], and MUST be used with pseudowires of type 0x0003, "ATM
   transparent cell transport" [4].

   The ATM transparent port service emulates connectivity between two
   remote ATM ports. This service is useful when one desires to connect
   two CEs without processing or switching at the VPC or VCC layer.  The
   ingress PE discards any idle/unassigned cells received from the
   ingress ATM port, and maps all other received cells to a single
   pseudowire.

   The egress PE does not change the VPI, VCI, PTI, or CLP bits when it
   sends these cells on the egress ATM port.  Therefore the transparent


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PWE3 ATM Transparent Cell Transport Service               October 2006


   port service appears to emulate an ATM transmission convergence layer
   connection between two ports.  However, since the ingress PE discards
   idle/unassigned cells, this service benefits from statistical
   multiplexing bandwidth savings.

   In accordance with [2], cell concatenation MAY be used for
   transparent cell relay transport in order to save the PSN bandwidth.
   If used, it MUST be agreed between the ingress and egress PEs. In
   particular, if the Pseudo Wire has been set up using the PWE3 control
   protocol [3], the ingress PE MUST NOT exceed the value of the
   "Maximum Number of concatenated ATM cells" Pseudowire Interface
   Parameter Sub-TLV type (Interface Parameter ID = 0x02 [4]) received
   in the Label Mapping message for the Pseudo Wire, and MUST NOT use
   cell concatenation if this parameter has been omitted by the egress
   PE.

   ATM OAM cells MUST be transported transparently, and the PEs do not
   act on them. If the PEs detect a PSN or pseudowire failure between
   them, they do not generate any OAM cells, but rather bring down the
   ATM interfaces to the CEs (e.g. generating LOS on the ATM port),
   just as if it were a transmission layer failure.

   Similarly, ATM ILMI signaling from the CEs, if any, MUST be
   transported transparently, and the PEs do not act on it.  However,
   the PEs must act on physical interface failure by either withdrawing
   the PW labels or by using pseudowire status signaling to indicate the
   interface failure.  The procedures for both alternatives are
   described in [3].

4. Security Considerations

   This draft does not introduce any new security considerations beyond
   those in [2] and [3]. This document defines an application that
   utilizes the encapsulation specified in [2], and does not specify the
   protocols used to carry the encapsulated packets across the PSN. Each
   such protocol may have its own set of security issues, but those
   issues are not affected by the application specified herein. Note
   that the security of the transported ATM service will only be as good
   as the security of the PSN. This level of security might be less
   rigorous then a native ATM service.

5. Congestion Control

   Since this document discusses an application of the "N-to-
   one" VCC cell transport mode for PWE3 ATM encapsulation described in
   [2], the congestion control considerations are identical to those
   discussed in section 15 of [2]. The PWE3 Working Group is also
   undertaking additional work on ATM-related congestion issues, and
   implementers should anticipate that an RFC will be published
   describing additional congestion techniques that should be applied to
   ATM emulation over pseudowires.


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6. IANA Considerations

   This document does not require any IANA actions.

7. Normative References

  [1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
      Levels", BCP 14, RFC 2119, March 1997.

  [2] Martini, L., et al, "Encapsulation Methods for Transport of ATM
      Over MPLS Networks", draft-ietf-pwe3-atm-encap-11.txt, May
      2006, work in progress.

  [3] Martini, L., et al, "Pseudowire Setup and Maintenance using the
      Label Distribution Protocol (LDP)", RFC 4447, April 2006.

  [4] Martini, L. et al, "IANA Allocations for Pseudowire Edge to Edge
      Emulation (PWE3)", RFC 4446, BCP 116, April 2006.

7. Full Copyright Statement

    Copyright (C) The Internet Society (2006).

    This document is subject to the rights, licenses and restrictions
    contained in BCP 78, and except as set forth therein, the authors
    retain all their rights.

    This document and the information contained herein are provided on
    an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE
    REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND
    THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
    EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
    THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR
    ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A
    PARTICULAR PURPOSE.

8. Acknowledgments

   The authors would like to thank the members of the PWE3 working group
   for their assistance on this draft, and Sasha Vainshtein of Axerra in
   particular for his comments and suggestions.

9. Author's Addresses

   Andrew G. Malis
   Tellabs
   90 Rio Robles Drive
   San Jose, CA 95134
   Email: Andy.Malis@tellabs.com




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PWE3 ATM Transparent Cell Transport Service               October 2006


   Luca Martini
   Cisco Systems, Inc.
   9155 East Nichols Avenue, Suite 400
   Englewood, CO, 80112
   e-mail: lmartini@cisco.com

   Jeremy Brayley
   ECI Telecom
   Omega Corporate Center
   1300 Omega Drive
   Pittsburgh, PA 15205
   Email: jeremy.brayley@ecitele.com

   Tom Walsh
   Juniper Networks
   1194 N Mathilda Ave
   Sunnyvale, CA 94089
   Email: twalsh@juniper.net



































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