Network Working Group Yuanlin Bao
Internet-Draft Xihua Fu
Intended status: Informational Fei Zhang
Expires: September 1, 2010 ZTE Corporation
February 28, 2010
LDP Signaling Extension For Management Plane To Control Plane PW
Ownership Transfer In A MPLS-TP Network
draft-bao-pwe3-pw-transfer-ldp-ext-00.txt
Abstract
This memo describes an extension to LDP signaling that enables the PW
ownership transfer between the Management Plane and the Control
Plane. This document defines all PW transfer related procedures.
This includes the handling of failure conditions and subsequent
reversion to original state. A basic premise of the extension is
that the transfer procedures must never impact an already established
Data plane connection.
Status of this Memo
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Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . . 3
2. LDP Extension . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.1. PW Ownership Transfer TLV . . . . . . . . . . . . . . . . . 4
3. PW Transfer Procedure . . . . . . . . . . . . . . . . . . . . . 4
3.1. PW Ownership Transfer from MP to CP . . . . . . . . . . . . 4
3.1.1. MS-PW specification . . . . . . . . . . . . . . . . . . 5
3.1.2. Failure Handling . . . . . . . . . . . . . . . . . . . 5
3.2. PW Ownership Transfer from CP to MP . . . . . . . . . . . . 5
3.2.1. Failure Handling . . . . . . . . . . . . . . . . . . . 5
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 6
7.1. Normative References . . . . . . . . . . . . . . . . . . . 6
7.2. Informative References . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
As defined in [RFC3985] PWE3 is a mechanism that emulates the
essential attributes of a telecommunications service (such as a T1
leased line or Frame Relay) over a PSN. Traditionally, pseudowir
(PW) are controlled by means of a Network Management System (NMS)
operating within the Management Plane (MP). NMS/MP is the owner of
PW, being responsible of it's set up, tear down and maintenance.
The adoption of a PW Control Plane ([RFC4447] and [DYNAMIC-MS-PW]) in
a network that is already in service - controlled by NMS at MP level
- introduces the need for a procedure able to coordinate a control
transfer of PW from MP to CP.
In addition, the control transfer in the opposite direction, from CP
to MP should be possible as well. The procedures described in this
memo can be applied to a PW in any DP switching technology and any
network architecture.
This memo describes an extension to LDP Protocol [RFC4447], [RFC5036]
signaling that enables the transfer of PW ownership between the
Management and the Control Planes. All transfer related procedures
are defined below. This includes the handling of failure conditions
and subsequent reversion to original state. A basic premise of the
extension is that the transfer procedures must never impact the
exchange of user data on PWs that are already established in the data
plane.
1.1. Conventions used in this document
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 [RFC2119].
2. LDP Extension
To ensure the PW ownership transfer between MP and CP automatically,
T-PE/S-PE SHOULD has the knowledge that it is the PW transfer
signaling message. Furthermore, for MS-PW transfer T-PE/S-PE SHOULD
know the next hop, so, the PW path MUST be carried in the LDP Label
Mapping message. Since [SEG-PW] has defined PW switching point TLV
(S-PE TLV) and Sub-TLV to the switching points that the PW traverses,
so S-PE TLV and Sub-TLV can be used to carry the PW path. Therefore,
this section only defines a new LDP TLV - Transfer TLV - which can be
used to indicate a PW transfer signaling procedure.
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2.1. PW Ownership Transfer TLV
The PW Ownership Transfer TLV (PW-OH TLV) is defined as following:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0|0| PW Transfer (0x0xxxx) | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|POT|
+-+-+
Figure 1: PW Ownership Transfer TLV
POT (2 bits): PW Ownership Transfer. This TLV is optional and
carried in Optional Parameters of LDP Label Mapping and Label
Withdraw message defined in [RFC5036].
01 - PW ownership transfer from management plane to control plane
11 - PW ownership transfer from control plane to management plane
3. PW Transfer Procedure
3.1. PW Ownership Transfer from MP to CP
The MP to CP PW transfer procedure MUST create a LDP session along
the path of the PW to be transfer from MP to CP, associat the LDP
session to the existing FEC-Label mapping owned by the MP and at the
same time transfer PW ownership to the CP.
The operator instructs the source/destinational T-PE to transfer
control of the PW from the MP to the CP. For MS-PW operator MUST
also supply the exact path of the MS-PW and FEC-Label mapping
information.
The source/destinational T-PE MUST check that no corresponding LDP
state exists and that corresponding Data Plane state does exist. If
there is an error, this MUST be reported to the operator and further
protocol action MUST NOT be taken.
The source/destination T-PE completes the LDP initialization as the
procedure described in [RFC5036] and [RFC4447]. After the LDP
initialization, the source T-PE SHOULD sends a Label Mapping message
with PW Ownership Transfer TLV in Optional Parameters to it's LDP
peer the destination T-PE, and vis versa. When destination/source
T-PE receives this PW transfer Label Mapping message, it only creates
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the LDP signaling state on the control plane, and any action for data
plane MUST not be triggered.
3.1.1. MS-PW specification
o The behaviour of T-PE
The source/destination T-PE of PW transfering from MP to CP,
SHOULD encond the PW path into S-PE TLV and Sub-TLV and set the Ho
of PW-OH TLV to 01, then encond these TLVs into Label Mapping
message. After source/destination T-PE completes the Label
Message enconding, it sends the message to the downstream node,
i.e. S-PE.
o The behaviour of S-PE
When S-PE receives the PW transfer Label Mapping message, it
SHOULD create the PW signaling state in the control plane, and get
the next hop from the S-PE TLV and Sub-TLV. After S-PE creates
the PW signaling state in the control plane, it sends the PW
transfer LDP Label Mapping message to the next hop.
3.1.2. Failure Handling
This section is to be studied in the next version.
3.2. PW Ownership Transfer from CP to MP
The CP to MP transfer procedure MUST delete the existing LDP session
information and MUST NOT affect the cross-connected resources, but
just move their ownership to the MP. That is, after PW ownership
transfer from CP to MP, the PW is no longer under control of LDP.
The source/destination T-PE node MUST send a Label Withdraw message
in the downstream direction with the Ho of PW-OH TLV set to 11
carried in Optional Parameters. No action is taken over the DP. For
MS-PW, S-PE must forward such message towards the source or
destination node for forward and reverse direction respectively.
Downstream nodes processing a Label Withdraw message MUST NOT remove
any associated data plane state.
3.2.1. Failure Handling
This section is to be studied in the next version.
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4. Security Considerations
TBD.
5. IANA Considerations
TBD.
6. Acknowledgements
The RFC text was produced using Marshall Rose's xml2rfc tool.
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3985] Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-
Edge (PWE3) Architecture", RFC 3985, March 2005.
[RFC4447] Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
Heron, "Pseudowire Setup and Maintenance Using the Label
Distribution Protocol (LDP)", RFC 4447, April 2006.
[RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP
Specification", RFC 5036, October 2007.
[RFC5659] Bocci, M. and S. Bryant, "An Architecture for Multi-
Segment Pseudowire Emulation Edge-to-Edge", RFC 5659,
October 2009.
7.2. Informative References
[DYNAMIC-MS-PW]
Luca Martini, Matthew Bocci, and Florin Balus, "Dynamic
Placement of Multi Segment Pseudo Wires",
draft-ietf-pwe3-dynamic-ms-pw-10.txt Working in progress.
[MPLS-TP-CP]
Loa Andersson, Lou Berger, and Luyuan Fang, "MPLS-TP
Control Plane Framework",
draft-abfb-mpls-tp-control-plane-framework-01.txt Working
in progress.
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[SEG-PW] Luca Martini and Chris Metz, "Segmented Pseudowire",
draft-ietf-pwe3-segmented-pw-13.txt Working in progress.
Authors' Addresses
Yuanlin Bao
ZTE Corporation
5F, R&D Building 3, ZTE Industrial Park, XiLi LiuXian Road
Nanshan District, Shenzhen 518055
P.R.China
Phone: +86 755 26773731
Email: bao.yuanlin@zte.com.cn
URI: http://www.zte.com.cn/
Xihua Fu
ZTE Corporation
West District,ZTE Plaza,No.10,Tangyan South Road,Gaoxin District
Xi An 710065
P.R.China
Phone: +86 13798412242
Email: fu.xihua@zte.com.cn
URI: http://www.zte.com.cn/
Fei Zhang
ZTE Corporation
NO.68, Zijinhua Road, Yuhuatai District
Nanjing 210000
P.R.China
Phone: +86 25 52877612
Email: zhang.fei3@zte.com.cn
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