Hi Julien,
All your comments have been reflected in the revision except:
Section 3.4.
---
- The phrase "b. Re-optimize wavelength(s)" reads odd, what about rephrasing
into "b. Re-consider wavelength(s) allocation"?
I think Re-optimize is meant to include wavelength(s) re-allocation as well as
path changes. I would leave the phrase as is.
Attached are the idnits report and the working version (v.13). Let me know if
this version satisfies you and if I should publish this.
Thanks,
Young
-----Original Message-----
From: Julien Meuric [mailto:[email protected]]
Sent: Thursday, July 31, 2014 7:10 AM
To: [email protected]
Cc: [email protected]
Subject: Re: FW: [Pce] I-D Action: draft-ietf-pce-wson-routing-wavelength-12.txt
Hi Young and WSON co-authors.
As part of the shepherding of the WSON requirement draft, please find below
some comments to address before sending to the IESG.
Regards,
Julien
----------
Globally, the way the top-level section titles are indented creates troubles to
IETF tools, including idnits. Please remove spacing before these section
header, from 1. to 8.
---
Along the document, unnecessary double spacing happens multiple times,
especially after periods. Please clean them up.
---------
In the header, could you compact the author list by removing blank lines?
---------
s/described in RFC-2119 0./described in [RFC2119]./
---------
Abstract
---
It is better when the abstract appears on the 1st page: please move it before
"Status of this Memo".
---
s/for Optical impairments/for optical impairments/
---------
Section 1.
---
- s/PCE based Architecture/PCE-based architecture/
- s/Generalized MPLS (GMPLS) networks/Generalized MPLS (GMPLS)-controlled
networks/
- s/Optical Switching Element/optical switching element/
- s/communications Protocol/communication Protocol/
- s/WDM based optical networks/WDM-based optical networks/
- A paragraph break right before "A transparent optical network" would be
appreciated.
- s/its route from/its path from/
- s/due to their relatively high cost/for cost reasons/
- s/all lightpath computation/all lightpath computations/
- s/for Optical impairments/for optical impairments/
---------
Section 2.
---
- s/in 0./in Figure 1./
- At the end of Figure 1's title, I would remove the period, to be consistent
with Figure 2.
- The DWA case is actually a sub-case of "separate processes", replacing
(c) by (b') would to the trick.
- To glue the text to the figure, 1./2./3. before paragraphs should be replaced
by (a)/(b)/(b').
- NEW last sentence in (b'): "This alternative is a particular case of
R+WA, it should be covered by GMPLS PCEP extensions and does not present
new WSON-specific requirements" [beware of the hyphen]
- s/PCE based implementation/PCE-based implementation/
---------
Section 3.1.
---
- Starting with "1." leads to look for "2.", which does not exist: it would
ease reading to drop "1." and start directly with "A PCEP request..."
- I would remove the "or" at the end of the line (i).
- Trailing text of (i) and (ii) should be aligned.
---------
Section 3.2.
---
- Trailing text of (i) and (ii) should be aligned.
- s/in R+WA or DWA/in R+WA or R+DWA/
- s/assigned to the route/assigned to the path/
- s/Label Sets/label set/
- s/no route/no path/
---------
Section 3.3.
---
- Before the 2 listed requirements, I suggest to add this NEW text:
"Sending simultaneous path requests for "routing only" computation is supported
by PCEP specification [RFC 5440]. To remain consistent, the following
requirements are added."
- s/the route and wavelength assigned to the route for each/the path and the
assigned wavelength for each/
---------
Section 3.4.
---
- The phrase "b. Re-optimize wavelength(s)" reads odd, what about rephrasing
into "b. Re-consider wavelength(s) allocation"?
- s/both wavelength and the path/both the wavelength and the path/
- s/no route/no path/
- s/both route and wavelength/both path and wavelength/
---------
Section 3.5.
---
- s/assigned wavelenght/assigned wavelength/
- s/Explicit Label or Label Sets/explicit label or label set/
- s/is NOT required/is not required/
- The "3.6." string and paragraph break has scrambled the last lines of the
section
- s/or an policy based/or a policy-based/
---------
Section 3.6.
---
- Fix the section header (as mentioned above)
- s/for (E.g., random assignment, descending order, ascending order, etc.)/for,
e.g., random assignment, descending order, ascending order, etc./
---
OLD:
" 2. A request for 2 or more paths (e.g., 1+1 link disjoint paths) MUST
be able to specify an option constraining the path to have the
same wavelength(s) assigned.
Note that this is extremely useful in the case of protection with
single transponder."
NEW:
"2. A request for two or more paths MUST be able to include an option
constraining the path 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)."
---
- s/contiguous wavelength/continuous wavelength/
- s/to constrain the wavelength continuity/to specify the precedence of
wavelength continuity/
---------
Section 3.7.
---
- s/or any given links/or on any given links/
---------
Section 4.5.
---
Not clear if it is a misplaced requirement or a nice-to-have idea. I suggest
replacing the sentence by the following NEW text:
"If PCE discovery mechanisms ([RFC5089] and [RFC5088]) were to be extended for
technology-specific capabilities, advertising WSON RWA path computation
capability should be considered."
---------
Section 8.
---
- RFCs 3471, 3473 and 6566 are note mentioned in the body of the I-D and should
be dropped.
- RFC 4003 is missing and should be added to informative documents.
- RFC 4657 and PCEP-MIB should be moved from normative to informative (no need
to read them to understand your I-D).
----THE END-----
Apr. 28, 2014 - Leeyoung:
> Hi Julien,
>
> This update reflects all the comments received from Cyril and Ramon as part
> of the WG LC.
>
> Cyril, please let the WG know if this update satisfies your comment.
>
> Best Regards,
> Young
>
> -----Original Message-----
> From: Pce [mailto:[email protected]] On Behalf Of
> [email protected]
> Sent: Monday, April 28, 2014 11:29 AM
>
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
> This draft is a work item of the Path Computation Element Working Group of
> the IETF.
>
> Title : PCEP Requirements for WSON Routing and Wavelength
> Assignment
> Authors : Young Lee
> Greg Bernstein
> Jonas Martensson
> Tomonori Takeda
> Takehiro Tsuritani
> Oscar Gonzalez de Dios
> Filename : draft-ietf-pce-wson-routing-wavelength-12.txt
> Pages : 14
> Date : 2014-04-28
>
> 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.
>
>
>
>
>
> The IETF datatracker status page for this draft is:
> https://datatracker.ietf.org/doc/draft-ietf-pce-wson-routing-wavelengt
> h/
>
> There's also a htmlized version available at:
> http://tools.ietf.org/html/draft-ietf-pce-wson-routing-wavelength-12
>
> A diff from the previous version is available at:
> http://www.ietf.org/rfcdiff?url2=draft-ietf-pce-wson-routing-wavelengt
> h-12
>
>
> Please note that it may take a couple of minutes from the time of submission
> until the htmlized version and diff are available at tools.ietf.org.
>
> Internet-Drafts are also available by anonymous FTP at:
> ftp://ftp.ietf.org/internet-drafts/
>
> _______________________________________________
> Pce mailing list
> [email protected]
> https://www.ietf.org/mailman/listinfo/pce
>
Network Working Group Y. Lee
Internet Draft Huawei
Intended status: Informational G. Bernstein
Expires: January 2015 Grotto Networking
Jonas Martensson
Acreo
T. Takeda
NTT
T. Tsuritani
KDDI
O. G. de Dios
Telefonica
July 31, 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-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six
months and may be updated, replaced, or obsoleted by other documents
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
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on October 31, 2014.
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.
Optical impairmentsOptical impairments
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
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4.3. Liveness Detection and Monitoring.........................9
4.4. Verifying Correct Operation...............................9
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
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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 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 path 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: [email protected]
Greg Bernstein (Ed.)
Grotto Networking
Fremont, CA, USA
Phone: (510) 573-2237
Email: [email protected]
Jonas Martensson
Acreo
Email:[email protected]
Tomonori Takeda
NTT Corporation
3-9-11, Midori-Cho
Musashino-Shi, Tokyo 180-8585, Japan
Email: [email protected]
Takehiro Tsuritani
KDDI R&D Laboratories, Inc.
2-1-15 Ohara Kamifukuoka Saitama, 356-8502. Japan
Phone: +81-49-278-7357
Email: [email protected]
Oscar Gonzalez de Dios
Telefonica Investigacion y Desarrollo
C/ Emilio Vargas 6
Madrid, 28043
Spain
Phone: +34 91 3374013
Email: [email protected]
Intellectual Property Statement
The IETF Trust takes no position regarding the validity or scope of
any Intellectual Property Rights or other rights that might be
claimed to pertain to the implementation or use of the technology
Lee & Bernstein Expires January 31, 2015 [Page 12]
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described in any IETF Document or the extent to which any license
under such rights might or might not be available; nor does it
represent that it has made any independent effort to identify any
such rights.
Copies of Intellectual Property disclosures made to the IETF
Secretariat and any assurances of licenses to be made available, or
the result of an attempt made to obtain a general license or
permission for the use of such proprietary rights by implementers or
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1 Network Working Group Y. Lee
2 Internet Draft Huawei
3 Intended status: Informational G. Bernstein
4 Expires: January 2015 Grotto Networking
5 Jonas Martensson
6 Acreo
7 T. Takeda
8 NTT
9 T. Tsuritani
10 KDDI
11 O. G. de Dios
12 Telefonica
14 July 31, 2014
16 PCEP Requirements for WSON Routing and Wavelength Assignment
18 draft-ietf-pce-wson-routing-wavelength-13.txt
20 Abstract
22 This memo provides application-specific requirements for the Path
23 Computation Element communication Protocol (PCEP) for the support of
24 Wavelength Switched Optical Networks (WSON). Lightpath provisioning
25 in WSONs requires a routing and wavelength assignment (RWA) process.
26 From a path computation perspective, wavelength assignment is the
27 process of determining which wavelength can be used on each hop of a
28 path and forms an additional routing constraint to optical light
29 path computation. Requirements for optical impairments will be
30 addressed in a separate document.
32 Status of this Memo
34 This Internet-Draft is submitted to IETF in full conformance with
35 the provisions of BCP 78 and BCP 79.
37 Internet-Drafts are working documents of the Internet Engineering
38 Task Force (IETF), its areas, and its working groups. Note that
39 other groups may also distribute working documents as Internet-
40 Drafts.
42 Internet-Drafts are draft documents valid for a maximum of six
43 months and may be updated, replaced, or obsoleted by other documents
44 at any time. It is inappropriate to use Internet-Drafts as
45 reference material or to cite them other than as "work in progress."
46 The list of current Internet-Drafts can be accessed at
47 http://www.ietf.org/ietf/1id-abstracts.txt
49 The list of Internet-Draft Shadow Directories can be accessed at
50 http://www.ietf.org/shadow.html.
52 This Internet-Draft will expire on October 31, 2014.
54 Copyright Notice
56 Copyright (c) 2014 IETF Trust and the persons identified as the
57 document authors. All rights reserved.
59 This document is subject to BCP 78 and the IETF Trust's Legal
60 Provisions Relating to IETF Documents
61 (http://trustee.ietf.org/license-info) in effect on the date of
62 publication of this document. Please review these documents
63 carefully, as they describe your rights and restrictions with
64 respect to this document. Code Components extracted from this
65 document must include Simplified BSD License text as described in
66 Section 4.e of the Trust Legal Provisions and are provided without
67 warranty as described in the Simplified BSD License.
69 Optical impairmentsOptical impairments
71 Conventions used in this document
73 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
74 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
75 document are to be interpreted as described in [RFC2119].
77 Table of Contents
79 1. Introduction...................................................3
80 2. WSON RWA Processes & Architecture..............................4
81 3. Requirements...................................................6
82 3.1. Path Computation Type Option..............................6
83 3.2. RWA Processing............................................6
84 3.3. Bulk RWA Path Request/Reply...............................7
85 3.4. RWA Path Re-optimization Request/Reply....................7
86 3.5. Wavelength Range Constraint...............................7
87 3.6. Wavelength Assignment Preference..........................8
88 3.7. Signal Processing Capability Restriction..................8
89 4. Manageability Considerations...................................8
90 4.1. Control of Function and Policy............................9
91 4.2. Information and Data Models, e.g. MIB module..............9
92 4.3. Liveness Detection and Monitoring.........................9
93 4.4. Verifying Correct Operation...............................9
94 4.5. Requirements on Other Protocols and Functional Components10
95 4.6. Impact on Network Operation..............................10
96 5. Security Considerations.......................................10
97 6. IANA Considerations...........................................10
98 7. Acknowledgments...............................................10
99 8. References....................................................10
100 8.1. Normative References.....................................10
101 8.2. Informative References...................................11
102 Authors' Addresses...............................................12
103 Intellectual Property Statement..................................12
104 Disclaimer of Validity...........................................13
106 1. Introduction
108 [RFC4655] defines the PCE-based Architecture and explains how a Path
109 Computation Element (PCE) may compute Label Switched Paths (LSP) in
110 Multiprotocol Label Switching Traffic Engineering (MPLS-TE) and
111 Generalized MPLS (GMPLS)-controlled networks at the request of Path
112 Computation Clients (PCCs). A PCC is shown to be any network
113 component that makes such a request and may be for instance an
114 optical switching element within a Wavelength Division Multiplexing
115 (WDM) network.The PCE, itself, can be located anywhere within the
116 network, and may be within an optical switching element, a Network
117 Management System (NMS) or Operational Support System (OSS), or may
118 be an independent network server.
120 The PCE communication Protocol (PCEP) is the communication protocol
121 used between PCC and PCE, and may also be used between cooperating
122 PCEs. [RFC4657] sets out the common protocol requirements for PCEP.
123 Additional application-specific requirements for PCEP are deferred
124 to separate documents.
126 This document provides a set of application-specific PCEP
127 requirements for support of path computation in Wavelength Switched
128 Optical Networks (WSON). WSON refers to WDM-based optical networks
129 in which switching is performed selectively based on the wavelength
130 of an optical signal.
132 The path in WSON is referred to as a lightpath. A lightpath may
133 span multiple fiber links and the path should be assigned a
134 wavelength for each link.
136 A transparent optical network is made up of optical devices that can
137 switch but not convert from one wavelength to another. In a
138 transparent optical network, a lightpath operates on the same
139 wavelength across all fiber links that it traverses. In such case,
140 the lightpath is said to satisfy the wavelength-continuity
141 constraint. Two lightpaths that share a common fiber link cannot be
142 assigned the same wavelength. To do otherwise would result in both
143 signals interfering with each other. Note that advanced additional
144 multiplexing techniques such as polarization based multiplexing are
145 not addressed in this document since the physical layer aspects are
146 not currently standardized. Therefore, assigning the proper
147 wavelength on a lightpath is an essential requirement in the optical
148 path computation process.
150 When a switching node has the ability to perform wavelength
151 conversion the wavelength-continuity constraint can be relaxed, and
152 a lightpath may use different wavelengths on different links along
153 its path from origin to destination. It is, however, to be noted
154 that wavelength converters may be limited for cost reasons, while
155 the number of WDM channels that can be supported in a fiber is also
156 limited. As a WSON can be composed of network nodes that cannot
157 perform wavelength conversion, nodes with limited wavelength
158 conversion, and nodes with full wavelength conversion abilities,
159 wavelength assignment is an additional routing constraint to be
160 considered in all lightpath computations.
162 In this document we first review the processes for routing and
163 wavelength assignment (RWA) used when wavelength continuity
164 constraints are present and then specify requirements for PCEP to
165 support RWA. Requirements for optical impairments will be addressed
166 in a separate document.
168 The remainder of this document uses terminology from [RFC4655].
170 2. WSON RWA Processes & Architecture
172 In [RFC6163] three alternative process architectures were given for
173 performing routing and wavelength assignment. These are shown
174 schematically in Figure 1.
176 +-------------------+
177 | +-------+ +--+ | +-------+ +--+ +-------+ +---+
178 | |Routing| |WA| | |Routing|--->|WA| |Routing|--->|DWA|
179 | +-------+ +--+ | +-------+ +--+ +-------+ +---+
180 | Combined | Separate Processes Separate Processes
181 | Processes | WA performed in a
182 +-------------------+ Distributed manner
183 (a) (b) (b')
185 Figure 1. RWA process alternatives
187 These alternatives have the following properties and impact on PCEP
188 requirements in this document.
190 (a) Combined Processes (R&WA)
192 Here path selection and wavelength assignment are performed as
193 a single process. The requirements for PCC-PCE interaction
194 with such a combined RWA process PCE is addressed in this
195 document.
197 (b) Routing separate from Wavelength Assignment (R+WA)
199 Here the routing process furnishes one or more potential paths
200 to the wavelength assignment process that then performs final
201 path selection and wavelength assignment. The requirements
202 for PCE-PCE interaction with one PCE implementing the routing
203 process and another implementing the wavelength assignment
204 process are not addressed in this document.
206 (b') Routing and distributed Wavelength Assignment (R+DWA)
208 Here a standard path computation (unaware of detailed
209 wavelength availability) takes place, then wavelength
210 assignment is performed along this path in a distributed
211 manner via signaling (RSVP-TE). This alternative is a
212 particular case of R+WA and it should be covered by GMPLS PCEP
213 extensions and does not present new WSON-specific
214 requirements.
216 In the previous section various process architectures for
217 implementing RWA have been reviewed. Figure 2 shows one typical PCE-
218 based implementation, which is referred to as Combined Process
219 (R&WA). With this architecture, the two processes of routing and
220 wavelength assignment are accessed via a single PCE. This
221 architecture is the base architecture from which the requirements
222 are specified in this document.
224 +----------------------------+
225 +-----+ | +-------+ +--+ |
226 | | | |Routing| |WA| |
227 | PCC |<----->| +-------+ +--+ |
228 | | | |
229 +-----+ | PCE |
230 +----------------------------+
232 Figure 2. Combined Process (R&WA) architecture
234 3. Requirements
236 The requirements for the PCC to PCE interface of Figure 2 are
237 specified in this section.
239 3.1. Path Computation Type Option
241 A PCEP request MUST include the path computation type. This can be:
243 (i) Both Routing and Wavelength Assignment (RWA),
245 (ii) Routing only.
247 This requirement is needed to differentiate between the currently
248 supported routing with distributed wavelength assignment option and
249 combined RWA. In case of distributed wavelength assignment option,
250 wavelength assignment will be performed at each node of the route.
252 3.2. RWA Processing
254 (a) When the request is a RWA path computation type, the request
255 MUST further include the wavelength assignment options. At the
256 minimum, the following option should be supported:
258 (i) Explicit Label Control (ELC) [RFC4003]
260 (ii) A set of recommended labels. The PCC can select the
261 label based on local policy.
263 Note that option (ii) may also be used in R+WA or R+DWA.
265 (b) In case of a RWA computation type, the response MUST include
266 the wavelength(s) assigned to the path and an indication of which
267 label assignment option has been applied (ELC or label set).
269 (c) In the case where a valid path is not found, the response MUST
270 include why the path is not found (e.g., no path, wavelength not
271 found, optical quality check failed, etc.)
273 3.3. Bulk RWA Path Request/Reply
275 Sending simultaneous path requests for "routing only" computation is
276 supported by PCEP specification [RFC5440]. To remain consistent the
277 following requirements are added.
279 (a) A PCEP request MUST be able to specify an option for bulk RWA
280 path request. Bulk path request is an ability to request a number
281 of simultaneous RWA path requests.
283 (b) The PCEP response MUST include the path and the assigned
284 wavelength assigned for each RWA path request specified in the
285 original bulk request.
287 3.4. RWA Path Re-optimization Request/Reply
289 1. For a re-optimization request, the request MUST provide both the
290 path and current wavelength to be re-optimized and MAY include
291 the following options:
293 a. Re-optimize the path keeping the same wavelength(s)
295 b. Re-optimize wavelength(s) keeping the same path
297 c. Re-optimize allowing both the wavelength and the path to
298 change
300 2. The corresponding response to the re-optimized request MUST
301 provide the re-optimized path and wavelengths.
303 3. In case that the path is not found, the response MUST include why
304 the path is not found (e.g., no path, wavelength not found, both
305 path and wavelength not found, etc.)
307 3.5. Wavelength Range Constraint
309 For any RWA computation type request, the requester (PCC) MAY
310 specify a restriction on the wavelengths to be used. The requester
311 MAY use this option to restrict the assigned wavelength for explicit
312 label or label set.
314 Note that the requestor (e.g., PCC) is not required to furnish any
315 range restrictions. This restriction may for example come from the
316 tuning ability of a laser transmitter, any optical element, or an
317 policy-based restriction.
319 3.6. Wavelength Assignment Preference
321 1. A RWA computation type request MAY include the requestor
322 preference for, e.g., random assignment, descending order,
323 ascending order, etc. A response SHOULD follow the requestor
324 preference unless it conflicts with operator's policy.
326 2. A request for two or more paths MUST be able to include an option
327 constraining the path to have the same wavelength(s) assigned.
328 This is useful in the case of protection with single transponder
329 (e.g., 1+1 link disjoint paths).
331 In a network with wavelength conversion capabilities (e.g. sparse 3R
332 regenerators), a request SHOULD be able to indicate whether a
333 single, continuous wavelength should be allocated or not. In other
334 words, the requesting PCC SHOULD be able to specify the precedence
335 of wavelength continuity even if wavelength conversion is available.
337 3.7. Signal Processing Capability Restriction
339 A request MUST be able to specify restrictions for signal
340 compatibility either on the endpoints or on any given links. The
341 following signal processing capabilities should be supported at a
342 minimum:
344 o Modulation Type List
346 o FEC Type List
348 4. Manageability Considerations
350 Manageability of WSON Routing and Wavelength Assignment (RWA) with
351 PCE must address the following considerations:
353 4.1. Control of Function and Policy
355 In addition to the parameters already listed in Section 8.1 of
356 [RFC5440], a PCEP implementation SHOULD allow configuring the
357 following PCEP session parameters on a PCC:
359 o The ability to send a WSON RWA request.
361 In addition to the parameters already listed in Section 8.1 of
362 [RFC5440], a PCEP implementation SHOULD allow configuring the
363 following PCEP session parameters on a PCE:
365 o The support for WSON RWA.
367 o The maximum number of bulk path requests associated with WSON
368 RWA per request message.
370 These parameters may be configured as default parameters for any
371 PCEP session the PCEP speaker participates in, or may apply to a
372 specific session with a given PCEP peer or a specific group of
373 sessions with a specific group of PCEP peers.
375 4.2. Information and Data Models, e.g. MIB module
377 As this document only concerns the requirements to support WSON RWA,
378 no additional MIB module is defined in this document. However, the
379 corresponding solution draft will list the information that should
380 be added to the PCE MIB module defined in [PCEP-MIB].
382 4.3. Liveness Detection and Monitoring
384 Mechanisms defined in this document do not imply any new liveness
385 detection and monitoring requirements in addition to those already
386 listed in section 8.3 of [RFC5440].
388 4.4. Verifying Correct Operation
390 Mechanisms defined in this document do not imply any new
391 verification requirements in addition to those already listed in
392 section 8.4 of [RFC5440]
393 4.5. Requirements on Other Protocols and Functional Components
395 If PCE discovery mechanisms ([RFC5089] and [RFC5088]) were to be
396 extended for technology-specific capabilities, advertising WSON RWA
397 path computation capability should be considered.
399 4.6. Impact on Network Operation
401 Mechanisms defined in this document do not imply any new network
402 operation requirements in addition to those already listed in
403 section 8.6 of [RFC5440].
405 5. Security Considerations
407 This document has no requirement for a change to the security models
408 within PCEP [RFC5440]. However the additional information
409 distributed in order to address the RWA problem represents a
410 disclosure of network capabilities that an operator may wish to keep
411 private. Consideration should be given to securing this information.
413 6. IANA Considerations
415 This informational document does not make any requests for IANA
416 action.
418 7. Acknowledgments
420 The authors would like to thank Adrian Farrel, Cycil Margaria and
421 Ramon Casellas for many helpful comments that greatly improved the
422 contents of this draft.
424 This document was prepared using 2-Word-v2.0.template.dot.
426 8. References
428 8.1. Normative References
430 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
431 Requirement Levels", BCP 14, RFC 2119, March 1997.
433 [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
434 Element (PCE)-Based Architecture", RFC 4655, August 2006.
436 [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
437 Element (PCE) communication Protocol", RFC 5440, March
438 2009.
440 8.2. Informative References
442 [RFC4003] L. Berger, "GMPLS Signaling Procedure for Egress Control",
443 RFC 4003, February 2005.
445 [RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE)
446 Communication Protocol Generic Requirements", RFC 4657,
447 September 2006.
449 [RFC6163] Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS
450 and PCE Control of Wavelength Switched Optical Networks",
451 RFC 6163, April 2011.
453 [RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
454 Zhang, "OSPF Protocol Extensions for Path Computation
455 Element (PCE) Discovery", RFC 5088, January 2008.
457 [RFC5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
458 Zhang, "IS-IS Protocol Extensions for Path Computation
459 Element (PCE) Discovery", RFC 5089, January 2008.
461 [PCEP-MIB] Koushik, K, et al., "PCE communication protocol(PCEP)
462 Management Information Base", draft-ietf-pce-pcep-mib,
463 work in progress.
465 Authors' Addresses
467 Young Lee (Ed.)
468 Huawei Technologies
469 5340 Legacy Drive, Building 3
470 Plano, TX 75245, USA
471 Phone: (469)277-5838
472 Email: [email protected]
474 Greg Bernstein (Ed.)
475 Grotto Networking
476 Fremont, CA, USA
477 Phone: (510) 573-2237
478 Email: [email protected]
480 Jonas Martensson
481 Acreo
482 Email:[email protected]
484 Tomonori Takeda
485 NTT Corporation
486 3-9-11, Midori-Cho
487 Musashino-Shi, Tokyo 180-8585, Japan
488 Email: [email protected]
490 Takehiro Tsuritani
491 KDDI R&D Laboratories, Inc.
492 2-1-15 Ohara Kamifukuoka Saitama, 356-8502. Japan
493 Phone: +81-49-278-7357
494 Email: [email protected]
496 Oscar Gonzalez de Dios
497 Telefonica Investigacion y Desarrollo
498 C/ Emilio Vargas 6
499 Madrid, 28043
500 Spain
501 Phone: +34 91 3374013
502 Email: [email protected]
504 Intellectual Property Statement
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523 rights that may cover technology that may be required to implement
524 any standard or specification contained in an IETF Document. Please
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