PCEP Requirements for WSON Routing and Wavelength Assignment
draft-ietf-pce-wson-routing-wavelength-13
The information below is for an old version of the document.
| Document | Type | Active Internet-Draft (pce WG) | |
|---|---|---|---|
| Authors | Young Lee , Greg M. Bernstein , Jonas MÃ¥rtensson , Tomonori Takeda , Takehiro Tsuritani , Oscar Gonzalez de Dios | ||
| Last updated | 2014-08-27 (Latest revision 2014-08-01) | ||
| Replaces | draft-lee-pce-wson-routing-wavelength | ||
| Stream | Internet Engineering Task Force (IETF) | ||
| Formats | plain text htmlized pdfized bibtex | ||
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| Stream | WG state | Submitted to IESG for Publication | |
| Document shepherd | Julien Meuric | ||
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draft-ietf-pce-wson-routing-wavelength-13
Network Working Group Y. Lee
Internet Draft Huawei
Intended status: Informational G. Bernstein
Expires: February 2015 Grotto Networking
Jonas Martensson
Acreo
T. Takeda
NTT
T. Tsuritani
KDDI
O. G. de Dios
Telefonica
August 1, 2014
PCEP Requirements for WSON Routing and Wavelength Assignment
draft-ietf-pce-wson-routing-wavelength-13.txt
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.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with
the provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
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Internet-Drafts are draft documents valid for a maximum of six
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at any time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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The list of current Internet-Drafts can be accessed at
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This Internet-Draft will expire on January 1, 2009.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document. Code Components extracted from this
document must include Simplified BSD License text as described in
Section 4.e of the Trust Legal Provisions and are provided without
warranty as described in the Simplified BSD License.
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
2. WSON RWA Processes & Architecture..............................4
3. Requirements...................................................6
3.1. Path Computation Type Option..............................6
3.2. RWA Processing............................................6
3.3. Bulk RWA Path Request/Reply...............................7
3.4. RWA Path Re-optimization Request/Reply....................7
3.5. Wavelength Range Constraint...............................7
3.6. Wavelength Assignment Preference..........................8
3.7. Signal Processing Capability Restriction..................8
4. Manageability Considerations...................................8
4.1. Control of Function and Policy............................9
4.2. Information and Data Models, e.g. MIB module..............9
4.3. Liveness Detection and Monitoring.........................9
4.4. Verifying Correct Operation...............................9
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4.5. Requirements on Other Protocols and Functional Components10
4.6. Impact on Network Operation..............................10
5. Security Considerations.......................................10
6. IANA Considerations...........................................10
7. Acknowledgments...............................................10
8. References....................................................10
8.1. Normative References.....................................10
8.2. 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)-controlled 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 communication 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
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constraint. Two lightpaths that share a common fiber link cannot 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 path from origin to destination. It is, however, to be noted
that wavelength converters may be limited for cost reasons, 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 computations.
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].
2. WSON RWA Processes & Architecture
In [RFC6163] 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) (b')
Figure 1. RWA process alternatives
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These alternatives have the following properties and impact on PCEP
requirements in this document.
(a) 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.
(b) 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.
(b') 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 is a
particular case of R+WA and it should be covered by GMPLS PCEP
extensions and does not present new WSON-specific
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.
+----------------------------+
+-----+ | +-------+ +--+ |
| | | |Routing| |WA| |
| PCC |<----->| +-------+ +--+ |
| | | |
+-----+ | PCE |
+----------------------------+
Figure 2. Combined Process (R&WA) architecture
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3. Requirements
The requirements for the PCC to PCE interface of Figure 2 are
specified in this section.
3.1. Path Computation Type Option
A PCEP request MUST include the path computation type. This can be:
(i) Both Routing and Wavelength Assignment (RWA),
(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.
3.2. RWA Processing
(a) When the request is a RWA path computation type, the request
MUST further include the wavelength assignment options. At the
minimum, the following option should be supported:
(i) Explicit Label Control (ELC) [RFC4003]
(ii) A set of recommended labels. The PCC can select the
label based on local policy.
Note that option (ii) may also be used in R+WA or R+DWA.
(b) In case of a RWA computation type, the response MUST include
the wavelength(s) assigned to the path and an indication of which
label assignment option has been applied (ELC or label set).
(c) In the case where a valid path is not found, the response MUST
include why the path is not found (e.g., no path, wavelength not
found, optical quality check failed, etc.)
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3.3. Bulk RWA Path Request/Reply
Sending simultaneous path requests for "routing only" computation is
supported by PCEP specification [RFC5440]. To remain consistent the
following requirements are added.
(a) A PCEP request 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.
(b) The PCEP response MUST include the path and the assigned
wavelength assigned for each RWA path request specified in the
original bulk request.
3.4. RWA Path Re-optimization Request/Reply
1. For a re-optimization request, the request MUST provide both the
path and current wavelength to be re-optimized and MAY 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 the wavelength and the path to
change
2. The corresponding response to the re-optimized request MUST
provide the re-optimized path and wavelengths.
3. In case that the path is not found, the response MUST include why
the path is not found (e.g., no path, wavelength not found, both
path and wavelength not found, etc.)
3.5. Wavelength Range Constraint
For any RWA computation type request, the requester (PCC) MAY
specify a restriction on the wavelengths to be used. The requester
MAY use this option to restrict the assigned wavelength for explicit
label or label set.
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Note that the requestor (e.g., PCC) is not required to furnish any
range restrictions. This restriction may for example come from the
tuning ability of a laser transmitter, any optical element, or an
policy-based restriction.
3.6. Wavelength Assignment Preference
1. A RWA computation type request MAY include the requestor
preference for, e.g., random assignment, descending order,
ascending order, etc. A response SHOULD follow the requestor
preference unless it conflicts with operator's policy.
2. A request for two or more paths MUST be able to include an option
constraining the paths to have the same wavelength(s) assigned.
This is useful in the case of protection with single transponder
(e.g., 1+1 link disjoint paths).
In a network with wavelength conversion capabilities (e.g. sparse 3R
regenerators), a request SHOULD be able to indicate whether a
single, continuous wavelength should be allocated or not. In other
words, the requesting PCC SHOULD be able to specify the precedence
of wavelength continuity even if wavelength conversion is available.
3.7. Signal Processing Capability Restriction
A request MUST be able to specify restrictions for signal
compatibility either on the endpoints or on any given links. The
following signal processing capabilities should be supported at a
minimum:
o Modulation Type List
o FEC Type List
4. Manageability Considerations
Manageability of WSON Routing and Wavelength Assignment (RWA) with
PCE must address the following considerations:
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4.1. 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.
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.
4.2. 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].
4.3. 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].
4.4. 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]
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4.5. Requirements on Other Protocols and Functional Components
If PCE discovery mechanisms ([RFC5089] and [RFC5088]) were to be
extended for technology-specific capabilities, advertising WSON RWA
path computation capability should be considered.
4.6. 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].
5. 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.
6. IANA Considerations
This informational document does not make any requests for IANA
action.
7. Acknowledgments
The authors would like to thank Adrian Farrel, Cycil Margaria and
Ramon Casellas for many helpful comments that greatly improved the
contents of this draft.
This document was prepared using 2-Word-v2.0.template.dot.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
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[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655, August 2006.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) communication Protocol", RFC 5440, March
2009.
8.2. Informative References
[RFC4003] L. Berger, "GMPLS Signaling Procedure for Egress Control",
RFC 4003, February 2005.
[RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements", RFC 4657,
September 2006.
[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.
[PCEP-MIB] Koushik, K, et al., "PCE communication protocol(PCEP)
Management Information Base", draft-ietf-pce-pcep-mib,
work in progress.
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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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