Internet DRAFT - draft-ietf-pce-wson-routing-wavelength
draft-ietf-pce-wson-routing-wavelength
Network Working Group Y. Lee
Internet Draft Huawei
Intended status: Informational G. Bernstein
Expires: April 2015 Grotto Networking
Jonas Martensson
Acreo
T. Takeda
NTT
T. Tsuritani
KDDI
O. G. de Dios
Telefonica
October 28, 2014
PCEP Requirements for WSON Routing and Wavelength Assignment
draft-ietf-pce-wson-routing-wavelength-15.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 PCEP extensions in support of
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.
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Copyright Notice
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This document is subject to BCP 78 and the IETF Trust's Legal
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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...............................8
3.6. Wavelength Assignment Preference..........................8
3.7. Signal Processing Capability Restriction..................8
4. Manageability Considerations...................................9
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........................10
4.4. Verifying Correct Operation..............................10
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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...........................................11
7. Acknowledgments...............................................11
8. References....................................................11
8.1. Normative References.....................................11
8.2. Informative References...................................11
Authors' Addresses...............................................12
Intellectual Property Statement..................................13
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. R stands for Routing, WA for Wavelength
Assignment, and DWA for Distributed Wavelength Assignment.
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+-------------------+
| +-------+ +--+ | +-------+ +--+ +-------+ +---+
| | R | |WA| | | R |--->|WA| | R |--->|DWA|
| +-------+ +--+ | +-------+ +--+ +-------+ +---+
| Combined | Separate Processes Separate Processes
| Processes | WA performed in a
+-------------------+ distributed manner
(a) (b) (b')
Figure 1. RWA process alternatives
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.
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+----------------------------+
+-----+ | +-------+ +--+ |
| | | |Routing| |WA| |
| PCC |<----->| +-------+ +--+ |
| | | |
+-----+ | PCE |
+----------------------------+
Figure 2. Combined Process (R&WA) architecture
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 MAY 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) [RFC3473]
(ii) A set of recommended labels for each hop. 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).
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(c) In the case where a valid path is not found, the response MUST
include why the path is not found (e.g., network disconnected,
wavelength not found, or both, etc.). Note that 'wavelength not
found' may include several sub-cases such as wavelength
continuity not met, unsupported FEC/Modulation type, etc.
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 even when the
request asked for the path or the wavelength to remain unchanged.
3. In case that the new path is not found, the response MUST include
why the path is not found (e.g., network disconnected, wavelength
not found, or both, etc.). Note that 'wavelength not found' may
include several sub-cases such as wavelength continuity not met,
unsupported FEC/Modulation type, etc.
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3.5. Wavelength Range Constraint
For any RWA computation type request, the requester (PCC) MUST be
allowed to 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. This restriction may for example
come from the tuning ability of a laser transmitter, any optical
element, or a policy-based restriction.
Note that the requester (e.g., PCC) is not required to furnish any
range restrictions.
3.6. Wavelength Assignment Preference
1. A RWA computation type request MAY include the requester
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 allow the requester 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
Signal processing compatibility is an important constraint for
optical path computation. The signal type for an end-to-end optical
path must match at source and at destination.
The PCC MUST be allowed to specify the signal type at the endpoints
(i.e., at source and at destination). The following signal
processing capabilities should be supported at a minimum:
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o Modulation Type List
o FEC Type List
The PCC MUST also be allowed to state whether transit modification
is acceptable for the above signal processing capabilities.
4. Manageability Considerations
Manageability of WSON Routing and Wavelength Assignment (RWA) with
PCE must address the following considerations:
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].
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4.3. Liveness Detection and Monitoring
No new mechanism is defined in this document that implies any new
liveness detection and monitoring requirements in addition to those
already listed in section 8.3 of [RFC5440].
4.4. Verifying Correct Operation
No new mechanism is defined in this document that implies any new
verification requirements in addition to those already listed in
section 8.4 of [RFC5440]
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
No new mechanism is defined in this document that implies 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.
Solutions that address the requirements in this document need to
verify that existing PCEP security mechanisms adequately protect the
additional network capabilities and must include new mechanisms as
necessary.
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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.
[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
[RFC3473] L. Berger, "Generalized Multi-Protocol Label Switching
(GMPLS) Signaling Resource ReserVation Protocol-Traffic
Engineering (RSVP-TE) Extensions", RFC 3473, January 2003.
[RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
Communication Protocol Generic Requirements", RFC 4657,
September 2006.
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[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.
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
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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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