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Versions: (draft-lee-pce-wson-routing-wavelength)
00 01 02 03 04 05 06 07 08 09 10 11
12 13 14 15 RFC 7449
Network Working Group Y. Lee
Internet Draft Huawei
Intended status: Informational
Expires: June 2014 G. Bernstein
Grotto Networking
Jonas Martensson
Acreo
T. Takeda
NTT
T. Tsuritani
KDDI
O. G. de Dios
Telefonica
December 23, 2013
PCEP Requirements for WSON Routing and Wavelength Assignment
draft-ietf-pce-wson-routing-wavelength-10.txt
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This Internet-Draft will expire on April 23, 2009.
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Copyright Notice
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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 for 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 RFC-2119 0.
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..................................6
2.1.1. RWA Computation Type and Wavelength Assignment Option6
2.1.2. Bulk RWA path request/reply..........................7
2.1.3. An RWA path re-optimization request/reply............7
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2.1.4. Wavelength Range Constraint..........................7
2.1.5. Wavelength Policy Constraint.........................8
2.1.6. Signal Processing Capability Restriction.............8
3. Manageability Considerations ...................................8
3.1. Control of Function and Policy............................8
3.2. Information and Data Models, e.g. MIB module..............9
3.3. Liveness Detection and Monitoring.........................9
3.4. Verifying Correct Operation...............................9
3.5. Requirements on Other Protocols and Functional Components.9
3.6. Impact on Network Operation..............................10
4. Security Considerations .......................................10
5. IANA Considerations ...........................................10
6. Acknowledgments ...............................................10
7. References ....................................................10
7.1. Normative References.....................................10
7.2. Informative References...................................11
Authors' Addresses...............................................12
Intellectual Property Statement..................................12
Disclaimer of Validity...........................................13
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.
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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 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. Requirements for Optical impairments will be addressed
in a separate document.
The remainder of this document uses terminology from [RFC4655].
1.1. WSON RWA Processes
In [RFC6163] three alternative process architectures were given for
performing routing and wavelength assignment. These are shown
schematically in Figure 1.
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+-------------------+
| +-------+ +--+ | +-------+ +--+ +-------+ +---+
| |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.
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 various process architectures for
implementing RWA have been reviewed. Figure 2 shows one typical PCE
based implementation, which is referred to as Combined Process
(R&WA). With this architecture, the two processes of routing and
wavelength assignment are accessed via a single PCE. This
architecture is the base architecture from which the requirements
are specified in this document.
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+----------------------------+
+-----+ | +-------+ +--+ |
| | | |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.
2.1.1. RWA Computation Type and Wavelength Assignment Option
1. The PCReq Message MUST include the path computation type. This
can be:
(i) Both Routing and Wavelength Assignment (RWA), or
(ii) Routing only.
This requirement is needed to differentiate between the currently
supported routing with distributed wavelength assignment option and
combined RWA. In case of distributed wavelength assignment option,
wavelength assignment will be performed at each node of the route.
2. When the PCReq Message is RWA path computation type, the PCReq
Message MUST further include the wavelength assignment options.
At the minimum, the following option should be supported:
(i) Explicit Label Control (ELC) [RFC4003]
(ii) Non-Explicit labels in the form of Label Sets (This will
allow Distributed WA at a node level where each node would
select the wavelength from the Label Sets)
3. The PCRep Message MUST include the route, wavelengths assigned to
the route and indication of which wavelength assignment option
has been applied (ELC or Label Sets).
4. 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, optical quality check failed, etc.)
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2.1.2. Bulk RWA path request/reply
1. The PCReq Message MUST be able to specify an option for bulk RWA
path request. Bulk path request is an ability to request a number
of simultaneous RWA path requests.
2. The PCRep Message MUST include the route, wavelength assigned to
the route for each RWA path request specified in the original
bulk PCReq Message.
2.1.3. An RWA path re-optimization request/reply
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.
3. 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.)
2.1.4. 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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2.1.5. Wavelength Policy Constraint
The PCReq Message May include specific operator's policy information
for WA (E.g., random assignment, descending order, ascending order,
etc.)
The PCReq Message SHOULD be able to request, when requesting a 1+1
connection (e.g. link disjoint paths), that both paths use the same
wavelength.
Note that this is extremely useful in the case of protection with
single transponder. Now, there is no way to specify such constraint.
The PCReq Message SHOULD be able to request, when performing 3R,
that wavelength may change or not.
2.1.6. Signal Processing Capability Restriction
The PCReq Message MUST be able to specify restrictions for signal
compatibility either on the endpoint or any given link. The
following signal processing capability should be supported at a
minimum:
o Modulation Type List
o FEC Type List
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
[RFC5440], a PCEP implementation SHOULD allow configuring the
following PCEP session parameters on a PCC:
o The ability to send a WSON RWA request.
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In addition to the parameters already listed in Section 8.1 of
[RFC5440], 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 bulk path requests associated with WSON
RWA per request message.
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
As this document only concerns the requirements to support WSON RWA,
no additional MIB module is defined in this document. However, the
corresponding solution draft will list the information that should
be added to the PCE MIB module defined in [PCEP-MIB].
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 [RFC5440].
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 [RFC5440]
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.
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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 [RFC5440].
4. Security Considerations
This document has no requirement for a change to the security models
within PCEP [RFC5440]. 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
This informational document does not make any requests for IANA
action.
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.
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.
[RFC3471] Berger, L., "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Functional Description", RFC 3471,
January 2003.
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[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
January 2003.
[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.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) communication Protocol", RFC 5440, March
2009.
[PCEP-MIB] Koushik, K, et al., "PCE communication protocol(PCEP)
Management Information Base", draft-ietf-pce-pcep-mib,
work in progress.
7.2. Informative References
[RFC6566] Lee, Y. and Bernstein, G. (Editors), D. Li and G.
Martinelli "A Framework for the Control and Measurement of
Wavelength Switched Optical Networks (WSON) with
Impairments", RFC 6566, March 2012.
[RFC6163] Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS
and PCE Control of Wavelength Switched Optical Networks",
RFC 6163, April 2011.
[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
5340 Legacy Drive, Building 3
Plano, TX 75245, USA
Phone: (469)277-5838
Email: leeyoung@huawei.com
Greg Bernstein (Ed.)
Grotto Networking
Fremont, CA, 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
Takehiro Tsuritani
KDDI R&D Laboratories, Inc.
2-1-15 Ohara Kamifukuoka Saitama, 356-8502. Japan
Phone: +81-49-278-7357
Email: tsuri@kddilabs.jp
Oscar Gonzalez de Dios
Telefonica Investigacion y Desarrollo
C/ Emilio Vargas 6
Madrid, 28043
Spain
Phone: +34 91 3374013
Email: ogondio@tid.es
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