Network Working Group Y. Lee
Internet Draft Huawei
Intended status: Standard Track
Expires: December 2009 G. Bernstein
Grotto Networking
Jonas Martensson
Acreo
T. Takeda
NTT
T. Otani
KDDI
June 29, 2009
PCEP Requirements for WSON Routing and Wavelength Assignment
draft-lee-pce-wson-routing-wavelength-05.txt
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Abstract
This memo provides application-specific requirements for the Path
Computation Element communication Protocol (PCEP) for the support of
Wavelength Switched Optical Networks (WSON). Lightpath provisioning
in WSONs requires a routing and wavelength assignment (RWA) process.
From a path computation perspective, wavelength assignment is the
process of determining which wavelength can be used on each hop of a
path and forms an additional routing constraint to optical light path
computation. Requirements related to optical impairments will be
addressed in a separate document.
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].
Table of Contents
1. Introduction...................................................3
1.1. WSON RWA Processes........................................4
2. WSON PCE Architectures and Requirements........................5
2.1. RWA PCC to PCE Interface..................................5
2.1.1. A new RWA path request...............................6
2.1.2. An RWA path re-optimization request..................6
2.1.3. Wavelength Range Constraint..........................6
3. Manageability Considerations...................................7
3.1. Control of Function and Policy............................7
3.2. Information and Data Models, e.g. MIB module..............7
3.3. Liveness Detection and Monitoring.........................7
3.4. Verifying Correct Operation...............................8
3.5. Requirements on Other Protocols and Functional Components.8
3.6. Impact on Network Operation...............................8
4. Security Considerations........................................8
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5. IANA Considerations............................................8
6. Acknowledgments................................................8
7. References.....................................................9
7.1. Normative References......................................9
7.2. Informative References....................................9
Authors' Addresses...............................................10
Intellectual Property Statement..................................10
Disclaimer of Validity...........................................11
1. Introduction
[RFC4655] defines the PCE based Architecture and explains how a Path
Computation Element (PCE) may compute Label Switched Paths (LSP) in
Multiprotocol Label Switching Traffic Engineering (MPLS-TE) and
Generalized MPLS (GMPLS) networks at the request of Path Computation
Clients (PCCs). A PCC is shown to be any network component that
makes such a request and may be for instance an Optical Switching
Element within a Wavelength Division Multiplexing (WDM) network. The
PCE, itself, can be located anywhere within the network, and may be
within an optical switching element, a Network Management System
(NMS) or Operational Support System (OSS), or may be an independent
network server.
The PCE communications Protocol (PCEP) is the communication protocol
used between PCC and PCE, and may also be used between cooperating
PCEs. [RFC4657] sets out the common protocol requirements for PCEP.
Additional application-specific requirements for PCEP are deferred to
separate documents.
This document provides a set of application-specific PCEP
requirements for support of path computation in Wavelength Switched
Optical Networks (WSON). WSON refers to WDM based optical networks
in which switching is performed selectively based on the wavelength
of an optical signal.
The path in WSON is referred to as a lightpath. A lightpath may span
multiple fiber links and the path should be assigned a wavelength for
each link. A transparent optical network is made up of optical
devices that can switch but not convert from one wavelength to
another. In a transparent optical network, a lightpath operates on
the same wavelength across all fiber links that it traverses. In such
case, the lightpath is said to satisfy the wavelength-continuity
constraint. Two lightpaths that share a common fiber link can not be
assigned the same wavelength. To do otherwise would result in both
signals interfering with each other. Note that advanced additional
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multiplexing techniques such as polarization based multiplexing are
not addressed in this document since the physical layer aspects are
not currently standardized. Therefore, assigning the proper
wavelength on a lightpath is an essential requirement in the optical
path computation process.
When a switching node has the ability to perform wavelength
conversion the wavelength-continuity constraint can be relaxed, and a
lightpath may use different wavelengths on different links along its
route from origin to destination. It is, however, to be noted that
wavelength converters may be limited due to their relatively high
cost, while the number of WDM channels that can be supported in a
fiber is also limited. As a WSON can be composed of network nodes
that cannot perform wavelength conversion, nodes with limited
wavelength conversion, and nodes with full wavelength conversion
abilities, wavelength assignment is an additional routing constraint
to be considered in all lightpath computation.
In this document we first review the processes for routing and
wavelength assignment (RWA) used when wavelength continuity
constraints are present and then specify requirements for PCEP to
support RWA.
The remainder of this document uses terminology from [RFC4655].
1.1. WSON RWA Processes
In [WSON-Frame] three alternative process architectures were given
for performing routing and wavelength assignment. These are shown
schematically in Figure 1.
+-------------------+
| +-------+ +--+ | +-------+ +--+ +-------+ +---+
| |Routing| |WA| | |Routing|--->|WA| |Routing|--->|DWA|
| +-------+ +--+ | +-------+ +--+ +-------+ +---+
| Combined | Separate Processes Separate Processes
| Processes | WA performed in a
+-------------------+ Distributed manner
(a) (b) (c)
Figure 1 RWA process alternatives.
These alternatives have the following properties and impact on PCEP
requirements in this document.
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1. Combined Processes (R&WA) - Here path selection and wavelength
assignment are performed as a single process. The requirements for
PCC-PCE interaction with such a combined RWA process PCE is
addressed in this document.
2. Routing separate from Wavelength Assignment (R+WA) - Here the
routing process furnishes one or more potential paths to the
wavelength assignment process that then performs final path
selection and wavelength assignment. The requirements for PCE-PCE
interaction with one PCE implementing the routing process and
another implementing the wavelength assignment process are not
addressed in this document.
3. Routing and distributed Wavelength Assignment (R+DWA) - Here a
standard path computation (unaware of detailed wavelength
availability) takes place, then wavelength assignment is performed
along this path in a distributed manner via signaling (RSVP-TE).
This alternative should be covered by existing or emerging GMPLS
PCEP extensions and does not present new WSON specific
requirements.
2. WSON PCE Architectures and Requirements
In the previous section we reviewed various process architectures for
implementing RWA. In Figure 2 we reduce these alternatives to one
typical PCE based implementation, which is referred to as Combined
Process (R&WA). In Figure 2 we show the two processes of routing and
wavelength assignment accessed via a single PCE.
+----------------------------+
+-----+ | +-------+ +--+ |
| | | |Routing| |WA| |
| PCC |<----->| +-------+ +--+ |
| | | |
+-----+ | PCE |
+----------------------------+
Figure 2 Combined Process (R&WA) architecture
2.1. RWA PCC to PCE Interface
The requirements for the PCC to PCE interface of Figure 2 are
specified in this section.
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2.1.1. A new RWA path request
1. The PCReq Message MUST include the path computation type. This can
be: RWA, or only routing. This requirement is needed to
differentiate between the currently supported routing with
distribute wavelength assignment option and combined RWA.
2. The PCRep Message MUST include the route, and wavelengths assigned
to the route. In the case where a valid path is not found, the
PCRep Message MUST include why the path is not found (e.g., no
route, wavelength not found, etc.)
2.1.2. An RWA path re-optimization request
1. For a re-optimization request, the PCReq Message MUST provide the
path to be re-optimized and include the following options:
a. Re-optimize the path keeping the same wavelength(s)
b. Re-optimize wavelength(s) keeping the same path
c. Re-optimize allowing both wavelength and the path to change
2. The corresponding PCRep Message for the re-optimized request MUST
provide the Re-optimized path and wavelengths. In case that the
path is not found, the PCRep Message MUST include why the path is
not found (e.g., no route, wavelength not found, both route and
wavelength not found, etc.)
2.1.3. Wavelength Range Constraint
For any PCReq Message that is associated with a request for
wavelength assignment the requester (PCC) MUST be able to specify a
restriction on the wavelengths to be used.
Note that the requestor (PCC) is NOT required to furnish any range
restrictions. This restriction is to be interpreted by the PCE as a
constraint on the tuning ability of the origination laser
transmitter.
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3. Manageability Considerations
Manageability of WSON Routing and Wavelength Assignment (RWA) with
PCE must address the following considerations:
3.1. Control of Function and Policy
In addition to the parameters already listed in Section 8.1 of
[PCEP], a PCEP implementation SHOULD allow configuring the following
PCEP session parameters on a PCC:
o The ability to send a WSON RWA request.
In addition to the parameters already listed in Section 8.1 of
[PCEP], a PCEP implementation SHOULD allow configuring the following
PCEP session parameters on a PCE:
o The support for WSON RWA.
o The maximum number of synchronized path requests associated with
WSON RWA per request message.
o A set of WSON RWA specific policies (authorized sender, request
rate limiter, etc).
These parameters may be configured as default parameters for any PCEP
session the PCEP speaker participates in, or may apply to a specific
session with a given PCEP peer or a specific group of sessions with a
specific group of PCEP peers.
3.2. Information and Data Models, e.g. MIB module
Extensions to the PCEP MIB module defined in [PCEP-MIB] should be
defined, so as to cover the WSON RWA information introduced in this
document. A future revision of this document will list the
information that should be added to the MIB module.
3.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in section 8.3 of [PCEP].
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3.4. Verifying Correct Operation
Mechanisms defined in this document do not imply any new verification
requirements in addition to those already listed in section 8.4 of
[PCEP]
3.5. Requirements on Other Protocols and Functional Components
The PCE Discovery mechanisms ([RFC5089] and [RFC5088]) may be used to
advertise WSON RWA path computation capabilities to PCCs.
3.6. Impact on Network Operation
Mechanisms defined in this document do not imply any new network
operation requirements in addition to those already listed in section
8.6 of [PCEP].
4. Security Considerations
This document has no requirement for a change to the security models
within PCEP [PCEP]. However the additional information distributed in
order to address the RWA problem represents a disclosure of network
capabilities that an operator may wish to keep private. Consideration
should be given to securing this information.
5. IANA Considerations
A future revision of this document will present requests to IANA for
codepoint allocation.
6. Acknowledgments
The authors would like to thank Adrian Farrel for many helpful
comments that greatly improved the contents of this draft.
This document was prepared using 2-Word-v2.0.template.dot.
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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.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements", RFC 4657,
September 2006.
[PCEP] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) communication Protocol (PCEP) - Version 1",
RFC 5440, March 2009.
[PCEP-MIB] "PCE communication protocol(PCEP) Management Information
Base", draft-ietf-pce-pcep-mib, work in progress.
7.2. Informative References
[WSON-Frame] Bernstein, G. and Lee, Y. (Editors), and W. Imajuku, "A
Framework for the Control and Measurement of Wavelength
Switched Optical Networks (WSON) with Impairments
draft-bernstein-ccamp-wson-impairments, work in progress.
[WSON-IMP] Bernstein, G. and Lee, Y. (Editors), and D. Li, "Framework
for GMPLS and PCE Control of Wavelength Switched Optical
Networks", draft-bernstein-ccamp-wavelength-switched, work
in progress.
[RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "OSPF Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5088, January 2008.
[RFC5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
Zhang, "IS-IS Protocol Extensions for Path Computation
Element (PCE) Discovery", RFC 5089, January 2008.
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Authors' Addresses
Young Lee (Ed.)
Huawei Technologies
1700 Alma Drive, Suite 100
Plano, TX 75075, USA
Phone: (972) 509-5599 (x2240)
Email: ylee@huawei.com
Greg M. Bernstein (ed.)
Grotto Networking
Fremont California, USA
Phone: (510) 573-2237
Email: gregb@grotto-networking.com
Jonas Martensson
Acreo
Email:Jonas.Martensson@acreo.se
Tomonori Takeda
NTT Corporation
3-9-11, Midori-Cho
Musashino-Shi, Tokyo 180-8585, Japan
Email: takeda.tomonori@lab.ntt.co.jp
Tomohiro Otani
KDDI R&D Laboratories, Inc.
2-1-15 Ohara Kamifukuoka Saitama, 356-8502. Japan
Phone: +81-49-278-7357
Email: otani@kddilabs.jp
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