PWE3 Working Group
Internet Draft A. Malis
draft-ietf-pwe3-cell-transport-05.txt Tellabs
Expires: October 2006 L. Martini
Cisco Systems
J. Brayley
Laurel Networks, Inc.
T. Walsh
Lucent Technologies
April 2006
PWE3 ATM Transparent Cell Transport Service
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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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PWE3 ATM Transparent Cell Transport Service April 2006
1. Intellectual Property Statement
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Intellectual Property Rights or other rights that might be claimed
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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 April 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. IANA Considerations
This document does not require any IANA actions.
6. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
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PWE3 ATM Transparent Cell Transport Service April 2006
[2] Martini, L., et al, "Encapsulation Methods for Transport of ATM
Over MPLS Networks", draft-ietf-pwe3-atm-encap-10.txt, September
2005, work in progress.
[3] Martini, L., et al, "Pseudowire Setup and Maintenance using the
Label Distribution Protocol", work in progress, draft-ietf-pwe3-
control-protocol-17.txt, June 2005, work in progress.
[4] Martini, L. et al, "IANA Allocations for Pseudo Wire Edge to Edge
Emulation (PWE3)", draft-ietf-pwe3-iana-allocation-15.txt,
November 2005, work in progress.
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
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EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR
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PARTICULAR PURPOSE.
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.
Author's Addresses
Andrew G. Malis
Tellabs
90 Rio Robles Drive
San Jose, CA 95134
Email: Andy.Malis@tellabs.com
Luca Martini
Cisco Systems, Inc.
9155 East Nichols Avenue, Suite 400
Englewood, CO, 80112
e-mail: lmartini@cisco.com
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PWE3 ATM Transparent Cell Transport Service April 2006
Jeremy Brayley
ECI Telecom
Omega Corporate Center
1300 Omega Drive
Pittsburgh, PA 15205
Email: jeremy.brayley@ecitele.com
Tom Walsh
Lucent Technologies
1 Robbins Road
Westford, MA 01886 USA
Email: tdwalsh@lucent.com
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