Network Working Group G. Bernstein
Internet Draft Grotto Networking
Intended status: Standards Track Sugang Xu
NICT
Expires: January 2010 Y.Lee
Huawei
Hiroaki Harai
NICT
D. King
July 8, 2009
Signaling Extensions for Wavelength Switched Optical Networks
draft-bernstein-ccamp-wson-signaling-04.txt
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Abstract
This memo provides extensions to Generalized Multi-Protocol Label
Switching (GMPLS) signaling for control of wavelength switched optical
networks (WSON). These extensions build on previous work for the
control of G.709 based networks.
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...................................................2
2. Terminology....................................................3
3. Requirements for WSON Signaling................................4
3.1. WSON Signal Characterization..............................4
3.2. Bi-Directional Distributed Wavelength Assignment..........4
3.3. Distributed Wavelength Assignment Support.................5
3.4. Out of Scope..............................................5
4. WSON Signal Types, Forward Error Correction, and Rates.........6
4.1. Traffic Parameters for Optical Tributary Signals..........6
5. Bidirectional Lightpath using Same Wavelength..................7
5.1. Using LSP_ATTRIBUTES Object...............................7
5.2. Bidirectional Lightpath Signaling Procedure...............8
5.3. Backward Compatibility Considerations.....................9
6. Bidirectional Lightpath using Different Wavelengths............9
7. RWA Related....................................................9
7.1. Wavelength Assignment Method Selection....................9
8. Security Considerations.......................................10
9. IANA Considerations...........................................10
10. Acknowledgments..............................................10
11. References...................................................11
11.1. Normative References....................................11
11.2. Informative References..................................11
Author's Addresses...............................................13
Intellectual Property Statement..................................14
Disclaimer of Validity...........................................14
1. Introduction
This memo provides extensions to Generalized Multi-Protocol Label
Switching (GMPLS) signaling for control of wavelength switched
optical networks (WSON). In particular, extensions are given to
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characterize optical signal types via traffic parameters, permit
simultaneous bi-directional wavelength assignment, and control the
distributed wavelength assignment process. These extensions build on
previous work for the control of G.709 based networks.
2. Terminology
CWDM: Coarse Wavelength Division Multiplexing.
DWDM: Dense Wavelength Division Multiplexing.
FOADM: Fixed Optical Add/Drop Multiplexer.
ROADM: Reconfigurable Optical Add/Drop Multiplexer. A reduced port
count wavelength selective switching element featuring ingress and
egress line side ports as well as add/drop side ports.
RWA: Routing and Wavelength Assignment.
Wavelength Conversion/Converters: The process of converting an
information bearing optical signal centered at a given wavelength to
one with "equivalent" content centered at a different wavelength.
Wavelength conversion can be implemented via an optical-electronic-
optical (OEO) process or via a strictly optical process.
WDM: Wavelength Division Multiplexing.
Wavelength Switched Optical Networks (WSON): WDM based optical
networks in which switching is performed selectively based on the
center wavelength of an optical signal.
AWG: Arrayed Waveguide Grating.
OXC: Optical Cross Connect.
Optical Transmitter: A device that has both a laser tuned on certain
wavelength and electronic components, which converts electronic
signals into optical signals.
Optical Responder: A device that has both optical and electronic
components. It detects optical signals and converts optical signals
into electronic signals.
Optical Transponder: A device that has both an optical transmitter
and an optical responder.
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Optical End Node: The end of a wavelength (optical lambdas) lightpath
in the data plane. It may be equipped with some optical/electronic
devices such as wavelength multiplexers/demultiplexer (e.g. AWG),
optical transponder, etc., which are employed to transmit/terminate
the optical signals for data transmission.
3. Requirements for WSON Signaling
The following requirements for GMPLS based WSON signaling are in
addition to the functionality already provided by existing GMPLS
signaling mechanisms.
3.1. WSON Signal Characterization
WSON signaling MUST convey sufficient information characterizing the
signal to allow systems along the path to determine compatibility and
perform any required local configuration. Examples of such systems
include intermediate nodes (ROADMs, OXCs, Wavelength converters,
Regenerators, OEO Switches, etc...), links (WDM systems) and end
systems (detectors, demodulators, etc...). The details of any local
configuration are out of the scope of this document.
3.2. Bi-Directional Distributed Wavelength Assignment
WSON signaling MAY support distributed wavelength assignment
consistent with the wavelength continuity constraint for bi-
directional connections. The following two cases MAY be separately
supported: (a) Where the same wavelength is used for both upstream
and downstream directions, and (b) Where different wavelengths can be
used for both upstream and downstream directions.
The need for the same wavelength on both directions mainly comes from
the color constraint on some edges' hardware. In fact, the edges can
be classified into two types, i.e. without and with the wavelength-
port mapping re-configurability.
Without the mapping re-configurability at edges, the edge nodes must
use the same wavelength in both directions. For example, (1)
transponders are only connected to AWGs (i.e. multiplexer/de-
multiplexer) ports directly and fixedly, or (2) transponders are
connected to the add/drop ports of ROADM and each port is mapped to a
dedicated wavelength fixedly.
On the other hand, with the mapping re-configurability at edges, the
edge nodes can use different wavelengths in different directions. For
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example, in edge nodes, transponders are connected to add/drop ports
of colorless ROADM. Thus, the wavelength-port remapping problem can
be solved locally by appropriately configuring the colorless ROADM.
If the colorless ROADM consists of OXC and AWGs, the OXC is
configured appropriately.
The edges of data-plane in WSON can be constructed in different types
based on cost and flexibility concerns. Without re-configurability
we should consider the constraint of the same wavelength usage on
both directions, but have lower costs. While, with wavelength-port
mapping re-configurability we can relax the constraint, but have
higher costs.
These two types of edges will co-exist in WSON mesh, till all the
edges are unified by the same type. The existence of the first type
edges presents a requirement of the same wavelength usage on both
directions, which must be supported.
Moreover, if some carriers prefer an easy management lightpath usage,
say use the same wavelength on both directions to reduce the burden
on lightpath management, the same wavelength usage would be
beneficial.
In cases of equipment failure, etc., fast provisioning used in quick
recovery is critical to protect Carriers/Users against system loss.
This requires efficient signaling which supports distributed
wavelength assignment, in particular when the centralized wavelength
assignment capability is not available.
3.3. Distributed Wavelength Assignment Support
WSON signaling MAY support the selection of a specific distributed
wavelength assignment method.
As discussed in the [WSON-Frame] a variety of different wavelength
assignment algorithms have been developed. A number of these are
suitable for use in distributed wavelength assignment. This feature
would allow the specification of a particular approach when more than
one are implemented in the systems along the path.
3.4. Out of Scope
This draft does not address signaling information related to optical
impairments.
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4. WSON Signal Types, Forward Error Correction, and Rates
As discussed in [WSON-Comp] single channel optical signals used in
WSONs are called "optical tributary signals" and come in a number of
classes characterized by modulation format and bit rate. Although
WSONs are fairly transparent to the signals they carry, to ensure
compatibility amongst various networks devices and end systems it can
be important to include key lightpath characteristics as traffic
parameters in signaling [WSON-Comp].
4.1. Traffic Parameters for Optical Tributary Signals
As in [RFC4606] and [RFC4328] the following traffic parameters would
become the contents for the RSVP SENDER_TSPEC and FLOWSPEC objects.
The WSON traffic parameters SHOULD be defined as follows:
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mod Type | Mod Params| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bit Rate |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Modulation (Mod) Types:
Value Type
----- ----
0 Unspecified or Unknown
1 NRZ
2 RZ
Modulation Parameters(Mod Params): Are specific to the modulation
type.
For RZ modulation type we have the following modulation parameters
and meanings.
RZ 0 - 33%, 1 - 50%, 2 - 67% duty cycles
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See [G.959.1] and [Winzer06].
These are specific to the modulation type employed and may or may not
be used. For example NRZ modulation typically doesn't have extra
parameters, while RZ modulation has a duty cycle parameter.
Bitrate:
This is the bit rate given as a 32 bit IEEE floating point number.
5. Bidirectional Lightpath using Same Wavelength
With the wavelength continuity constraint in CI-incapable [RFC3471]
WSONs, where the nodes in the networks cannot support wavelength
conversion, the same wavelength on each link along a unidirectional
lightpath should be reserved. Per the definition in [RFC3471], a
bidirectional lightpath can be seen as a pair of unidirectional
lightpaths, which are provisioned along the same route simultaneously
by the RSVP-TE signaling with Upstream Label and Label Set Objects in
the messages [RFC3473]. This does not necessarily require the same
wavelength in both directions.
In addition to the wavelength continuity constraint, requirement 3.2
gives us another constraint on wavelength usage in data plane, in
particular, it requires the same wavelength to be used in both
directions.
The simplest and efficient way is to only define an extension to the
processing of Label Set [RFC3473], and leave the other processes
untouched. The issues related to this new functionality including an
LSP_ATTRIBUTES object defined in [RFC5420] and the new procedure are
described in the following sections. This approach would have a lower
blocking probability and a shorter provisioning time. In cases of
equipment failure, etc., fast provisioning used in quick recovery is
critical to protect Carriers/Users against system loss.
5.1. Using LSP_ATTRIBUTES Object
To trigger the new functionality at each GMPLS node, it is necessary
to notify the receiver the new type lightpath request. One multi-
purpose flag/attribute parameter container object called
LSP_ATTRIBUTES object and related mechanism defined in [RFC5420] meet
this requirement. One bit in Attributes Flags TLV which indicates the
new type lightpath, say, the bidirectional same wavelength lightpath
will be present in an LSP_ATTRIBUTES object. Please refer to
[RFC5420] for detailed descriptions of the Flag and related issues.
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5.2. Bidirectional Lightpath Signaling Procedure
Considering the system configuration mentioned above, it is needed to
add a new function into RSVP-TE to support bidirectional lightpath
with same wavelength on both directions.
The lightpath setup procedure is described below:
1. Ingress node adds the new type lightpath indication in an
LSP_ATTRIBUTES object. It is propagated in the Path message in
the same way as that of a Label Set object for downstream;
2. On reception of a Path message containing both the new type
lightpath indication in an LSP_ATTRIBUTES object and Label Set
object, the receiver of message along the path checks the local
LSP database to see if the Label Set TLVs are acceptable on both
directions jointly. If there are acceptable wavelengths, then
copy the values of them into new Label Set TLVs, and forward the
Path message to the downstream node. Otherwise the Path message
will be terminated, and a PathErr message with a "Routing
problem/Label Set" indication will be generated;
3. On reception of a Path message containing both such a new type
lightpath indication in an LSP_ATTRIBUTES object and an Upstream
Label object, the receiver MUST terminate the Path message using
a PathErr message with Error Code "Unknown Attributes TLV" and
Error Value set to the value of the new type lightpath TLV type
code;
4. On reception of a Path message containing both the new type
lightpath indication in an LSP_ATTRIBUTES object and Label Set
object, the egress node verifies whether the Label Set TLVs are
acceptable, if one or more wavelengths are available on both
directions, then any one available wavelength could be selected.
A Resv message is generated and propagated to upstream node;
5. When a Resv message is received at an intermediate node, if it is
a new type lightpath, the intermediate node allocates the label
to interfaces on both directions and update internal database for
this bidirectional same wavelength lightpath, then configures the
local ROADM or OXC on both directions.
Except the procedure related to Label Set object, the other processes
will be left untouched.
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5.3. Backward Compatibility Considerations
Due to the introduction of new processing on Label Set object, it is
required that each node in the lightpath is able to recognize the new
type lightpath indication Flag carried by an LSP_ATTRIBUTES object,
and deal with the new Label Set operation correctly. It is noted
that this new extension is not backward compatible.
According to the descriptions in [RFC5420], an LSR that does not
recognize a TLV type code carried in this object MUST reject the Path
message using a PathErr message with Error Code "Unknown Attributes
TLV" and Error Value set to the value of the Attributes Flags TLV
type code.
An LSR that does not recognize a bit set in the Attributes Flags TLV
MUST reject the Path message using a PathErr message with Error Code
"Unknown Attributes Bit" and Error Value set to the bit number of the
new type lightpath Flag in the Attributes Flags.The reader is
referred to the detailed backward compatibility considerations
expressed in [RFC5420].
6. Bidirectional Lightpath using Different Wavelengths
TBD
7. RWA Related
7.1. Wavelength Assignment Method Selection
As discussed in [HZang00] a number of different wavelength assignment
algorithms maybe employed. In addition as discussed in [WSON-Frame]
the wavelength assignment can be either for a unidirectional
lightpath or for a bidirectional lightpath constrained to use the
same lambda in both directions. A simple TLV could be used to
indication wavelength assignment directionality and wavelength
assignment method. This would be placed in an LSP_REQUIRED_ATTRIBUTES
object per [RFC5420]. The use of a TLV in the LSP required attributes
object was pointed out in [Xu].
[TO DO: The directionality stuff needs to be reconciled with the
earlier material]
Directionality: 0 unidirectional, 1 bidirectional
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Wavelength Assignment Method: 0 unspecified (any), 1 First-Fit, 2
Random, 3 Least-Loaded (multi-fiber). Others TBD.
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Direction | WA Method | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
8. Security Considerations
This document has no requirement for a change to the security models
within GMPLS and associated protocols. That is the OSPF-TE, RSVP-TE,
and PCEP security models could be operated unchanged.
However satisfying the requirements for RWA using the existing
protocols may significantly affect the loading of those protocols.
This makes the operation of the network more vulnerable to denial of
service attacks. Therefore additional care maybe required to ensure
that the protocols are secure in the WSON environment.
Furthermore 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.
9. IANA Considerations
TBD. Once finalized in our approach we will need identifiers for such
things and modulation types, modulation parameters, wavelength
assignment methods, etc...
10. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
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11. References
11.1. 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.
[RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
January 2003.
[RFC4328] Papadimitriou, D., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Extensions for G.709 Optical
Transport Networks Control", RFC 4328, January 2006.
[RFC5420] Farrel, A., Ed., Papadimitriou, D., Vasseur, J.-P., and A.
Ayyangar, " Encoding of Attributes for MPLS LSP
Establishment Using Resource Reservation Protocol Traffic
Engineering (RSVP-TE)", RFC 5420, February 2006.
[RFC4606] Mannie, E. and D. Papadimitriou, "Generalized Multi-
Protocol Label Switching (GMPLS) Extensions for Synchronous
Optical Network (SONET) and Synchronous Digital Hierarchy
(SDH) Control", RFC 4606, August 2006.
11.2. Informative References
[WSON-Comp] G. Bernstein, Y. Lee, Ben Mack-Crane, "WSON Signal
Characteristics and Network Element Compatibility
Constraints for GMPLS", work in progress: draft-bernstein-
ccamp-wson-signal.
[WSON-Frame] G. Bernstein, Y. Lee, W. Imajuku, "Framework for GMPLS
and PCE Control of Wavelength Switched Optical Networks",
work in progress: draft-bernstein-ccamp-wavelength-
switched-03.txt, February 2008.
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[HZang00] H. Zang, J. Jue and B. Mukherjeee, "A review of routing and
wavelength assignment approaches for wavelength-routed
optical WDM networks", Optical Networks Magazine, January
2000.
[Xu] S. Xu, H. Harai, and D. King, "Extensions to GMPLS RSVP-TE
for Bidirectional Lightpath the Same Wavelength", work in
progress: draft-xu-rsvpte-bidir-wave-01, November 2007.
[Winzer06] Peter J. Winzer and Rene-Jean Essiambre, "Advanced
Optical Modulation Formats", Proceedings of the IEEE, vol.
94, no. 5, pp. 952-985, May 2006.
[G.959.1] ITU-T Recommendation G.959.1, Optical Transport Network
Physical Layer Interfaces, March 2006.
[G.694.1] ITU-T Recommendation G.694.1, Spectral grids for WDM
applications: DWDM frequency grid, June 2002.
[G.694.2] ITU-T Recommendation G.694.2, Spectral grids for WDM
applications: CWDM wavelength grid, December 2003.
[G.Sup43] ITU-T Series G Supplement 43, Transport of IEEE 10G base-R
in optical transport networks (OTN), November 2006.
[RFC4427] Mannie, E., Ed., and D. Papadimitriou, Ed., "Recovery
(Protection and Restoration) Terminology for Generalized
Multi-Protocol Label Switching (GMPLS)", RFC 4427, March
2006.
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Author's Addresses
Greg M. Bernstein (editor)
Grotto Networking
Fremont California, USA
Phone: (510) 573-2237
Email: gregb@grotto-networking.com
Nicola Andriolli
Scuola Superiore Sant'Anna, Pisa, Italy
Email: a.giorgetti@sssup.it
Aessio Giorgetti
Scuola Superiore Sant'Anna, Pisa, Italy
Email: a.giorgetti@sssup.it
Lin Guo
Key Laboratory of Optical Communication and Lightwave Technologies
Ministry of Education
P.O. Box 128, Beijing University of Posts and Telecommunications,
P.R.China
Email: guolintom@gmail.com
Hiroaki Harai
National Institute of Information and Communications Technology
4-2-1 Nukui-Kitamachi, Koganei,
Tokyo, 184-8795 Japan
Phone: +81 42-327-5418
Email: harai@nict.go.jp
Yuefeng Ji
Key Laboratory of Optical Communication and Lightwave Technologies
Ministry of Education
P.O. Box 128, Beijing University of Posts and Telecommunications,
P.R.China
Email: jyf@bupt.edu.cn
Daniel King (editor)
Old Dog Consulting
Email: daniel@olddog.co.uk
Young Lee (editor)
Huawei Technologies
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1700 Alma Drive, Suite 100
Plano, TX 75075
USA
Phone: (972) 509-5599 (x2240)
Email: ylee@huawei.com
Sugang Xu
National Institute of Information and Communications Technology
4-2-1 Nukui-Kitamachi, Koganei,
Tokyo, 184-8795 Japan
Phone: +81 42-327-6927
Email: xsg@nict.go.jp
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