Request for Comments: 7689
Category: Standards Track
Y. Lee, Ed.
Signaling Extensions for Wavelength Switched Optical Networks
This document provides extensions to Generalized Multiprotocol Label Switching (GMPLS) signaling for control of Wavelength Switched Optical Networks (WSONs). Such extensions are applicable in WSONs under a number of conditions including: (a) when optional processing, such as regeneration, must be configured to occur at specific nodes along a path, (b) where equipment must be configured to accept an optical signal with specific attributes, or (c) where equipment must be configured to output an optical signal with specific attributes. This document provides mechanisms to support distributed wavelength assignment with a choice of distributed wavelength assignment algorithms.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force (IETF). It represents the consensus of the IETF community. It has received public review and has been approved for publication by the Internet Engineering Steering Group (IESG). Further information on Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata, and how to provide feedback on it may be obtained at http://www.rfc-editor.org/info/rfc7689.
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Table of Contents
1. Introduction ....................................................3 2. Terminology .....................................................3 2.1. Conventions Used in This Document ..........................4 3. Requirements for WSON Signaling .................................4 3.1. WSON Signal Characterization ...............................4 3.2. Per-Node Processing Configuration ..........................5 3.3. Bidirectional WSON LSPs ....................................5 3.4. Distributed Wavelength Assignment Selection Method .........6 3.5. Optical Impairments ........................................6 4. WSON Signal Traffic Parameters, Attributes, and Processing ......6 4.1. Traffic Parameters for Optical Tributary Signals ...........7 4.2. WSON Processing Hop Attribute TLV ..........................7 4.2.1. ResourceBlockInfo Sub-TLV ...........................8 4.2.2. WavelengthSelection Sub-TLV .........................9 5. Security Considerations ........................................11 6. IANA Considerations ............................................11 7. References .....................................................13 7.1. Normative References ......................................13 7.2. Informative References ....................................14 Acknowledgments ...................................................15 Contributors ......................................................15 Author's Addresses ................................................16
This document provides extensions to Generalized Multiprotocol Label Switching (GMPLS) signaling for control of Wavelength Switched Optical Networks (WSONs). Fundamental extensions are given to permit simultaneous bidirectional wavelength assignment, while more advanced extensions are given to support the networks described in [RFC6163], which feature connections requiring configuration of input, output, and general signal processing capabilities at a node along a Label Switched Path (LSP).
These extensions build on previous work for the control of lambda and G.709-based networks.
Coarse Wavelength Division Multiplexing.
Dense Wavelength Division Multiplexing.
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.
Routing and Wavelength Assignment.
Wavelength Conversion/Converters: The process of converting
information bearing optical signal centered at a given frequency (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.
Wavelength Division Multiplexing.
Wavelength Switched Optical Networks (WSONs): WDM-based optical networks in which switching is performed selectively based on the frequency of an optical signal.
Arrayed Waveguide Grating.
Optical Transmitter: A device that has both a laser, tuned on a
certain wavelength, and electronic components that convert electronic signals into optical signals.
Optical Receiver: 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 receiver.
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.
FEC: Forward Error Correction. FEC is a digital signal processing
technique used to enhance data reliability. It does this by introducing redundant data, called error correcting code, prior to data transmission or storage. FEC provides the receiver with the ability to correct errors without a reverse channel to request the retransmission of data.
3R Regeneration: The process of amplifying (correcting loss),
reshaping (correcting noise and dispersion), retiming (synchronizing with the network clock), and retransmitting an optical signal.
2.1. 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].
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 needs to 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 processes are outside the scope of this document.
From [RFC6163], we have the following list of WSON signal characteristics:
1. Optical tributary signal class (modulation format). 2. FEC: whether forward error correction is used in the digital stream and what type of error correcting code is used 3. Center frequency (wavelength) 4. Bit rate 5. G-PID: General Protocol Identifier for the information format
The first three items on this list can change as a WSON signal traverses a network with regenerators, OEO switches, or wavelength converters. These parameters are summarized in the Optical Interface Class as defined in [RFC7446], and the assumption is that a class always includes signal compatibility information. An ability to control wavelength conversion already exists in GMPLS signaling along with the ability to share client signal type information (G-PID). In addition, bit rate is a standard GMPLS signaling traffic parameter. It is referred to as bandwidth encoding in [RFC3471].
3.2. Per-Node Processing Configuration
In addition to configuring a node along an LSP to input or output a signal with specific attributes, we may need to signal the node to perform specific processing, such as 3R regeneration, on the signal at a particular node. [RFC6163] discussed three types of processing:
(A) Regeneration (possibly different types)
(B) Fault and Performance Monitoring
(C) Attribute Conversion
The extensions here provide for the configuration of these types of processing at nodes along an LSP.
3.3. Bidirectional WSON LSPs
WSON signaling can support LSP setup consistent with the wavelength continuity constraint for bidirectional connections. The following cases need to be supported separately:
(a) Where the same wavelength is used for both upstream and
(b) Where different wavelengths are used for both upstream and
This document will review existing GMPLS bidirectional solutions according to WSON case.
3.4. Distributed Wavelength Assignment Selection Method
WSON signaling can support the selection of a specific distributed wavelength assignment method.
This method is beneficial in cases of equipment failure, etc., where fast provisioning used in quick recovery is critical to protect carriers/users against system loss. This requires efficient signaling that supports distributed wavelength assignment, in particular, when the wavelength assignment capability is not available.
As discussed in [RFC6163], different computational approaches for wavelength assignment are available. One method is the use of distributed wavelength assignment. This feature would allow the specification of a particular approach when more than one is implemented in the systems along the path.
3.5. Optical Impairments
This document does not address signaling information related to optical impairments.
4. WSON Signal Traffic Parameters, Attributes, and Processing
As discussed in [RFC6163], 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 [RFC6163].
LSPs signaled through extensions provided in this document MUST apply the following signaling parameters:
[RFC6205] defines the label format as applicable to LSC capable devices.
4.1. Traffic Parameters for Optical Tributary Signals
In [RFC3471] we see that the G-PID (client signal type) and bit rate (byte rate) of the signals are defined as parameters, and in [RFC3473] they are conveyed in the Generalized Label Request object and the RSVP SENDER_TSPEC/FLOWSPEC objects, respectively.
4.2. WSON Processing Hop Attribute TLV
Section 3.1 provides requirements to signal to a node along an LSP what type of processing to perform on an optical signal and how to configure itself to accept or transmit an optical signal with particular attributes.
To target a specific node, this section defines a WSON Processing Hop Attribute TLV. This TLV is encoded as an attributes TLV; see [RFC5420]. The TLV is carried in the ERO and RRO Hop Attributes subobjects and processed according to the procedures defined in [RFC7570]. The type value of the WSON Processing Hop Attribute TLV is 4 as assigned by IANA.
The WSON Processing Hop Attribute TLV carries one or more sub-TLVs with the following format:
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | // Value // | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | ... | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type
The identifier of the sub-TLV.
Indicates the total length of the sub-TLV in octets. That is, the combined length of the Type, Length, and Value fields, i.e., two plus the length of the Value field in octets.
Zero or more octets of data carried in the sub-TLV.
The entire sub-TLV MUST be padded with zeros to ensure four-octet alignment of the sub-TLV.
Sub-TLV ordering is significant and MUST be preserved. Error processing follows [RFC7570].
The following sub-TLV types are defined in this document:
Sub-TLV Name Type Length -------------------------------------------------------------- ResourceBlockInfo 1 variable WavelengthSelection 2 8 octets (2-octet padding)
The TLV can be represented in Reduced Backus-Naur Form (RBNF) [RFC5511] syntax as:
<WSON Processing Hop Attribute> ::= <ResourceBlockInfo> [<ResourceBlockInfo>] [<WavelengthSelection>]
4.2.1. ResourceBlockInfo Sub-TLV
The format of the ResourceBlockInfo sub-TLV value field is defined in Section 4 of [RFC7581]. It is a list of available Optical Interface Classes and processing capabilities.
At least one ResourceBlockInfo sub-TLV MUST be present in the WSON Processing Hop Attribute TLV. No more than two ResourceBlockInfo sub-TLVs SHOULD be present. Any present ResourceBlockInfo sub-TLVs MUST be processed in the order received, and extra (unprocessed) sub- TLVs SHOULD be ignored.
The ResourceBlockInfo field contains several information elements as defined by [RFC7581]. The following rules apply to the sub-TLV:
- RB Set field can carry one or more RB Identifier. Only the first RB Identifier listed in the RB Set field SHALL be processed; any others SHOULD be ignored.
- In the case of unidirectional LSPs, only one ResourceBlockInfo sub-TLV SHALL be processed, and the I and O bits can be safely ignored.
- In the case of a bidirectional LSP, there MUST be either:
(a) only one ResourceBlockInfo sub-TLV present in a WSON
Processing Hop Attribute TLV, and the bits I and O both set to 1, or
(b) two ResourceBlockInfo sub-TLVs present, one with only the I
bit set and the other with only the O bit set.
- The rest of the information carried within the ResourceBlockInfo sub-TLV includes the Optical Interface Class List, Input Bit Rate List, and Processing Capability List. These lists MAY contain one or more elements. These elements apply equally to both bidirectional and unidirectional LSPs.
Any violation of these rules detected by a transit or egress node SHALL be treated as an error and be processed per [RFC7570].
A ResourceBlockInfo sub-TLV can be constructed by a node and added to an ERO Hop Attributes subobject in order to be processed by downstream nodes (transit and egress). As defined in [RFC7570], the R bit reflects the LSP_REQUIRED_ATTRIBUTE and LSP_ATTRIBUTE semantic defined in [RFC5420], and it SHOULD be set accordingly.
Once a node properly parses a ResourceBlockInfo sub-TLV received in an ERO Hop Attributes subobject (according to the rules stated above and in [RFC7570]), the node allocates the indicated resources, e.g., the selected regeneration pool, for the LSP. In addition, the node SHOULD report compliance by adding an RRO Hop Attributes subobject with the WSON Processing Hop Attribute TLV (and its sub-TLVs) indicating the utilized resources. ResourceBlockInfo sub-TLVs carried in an RRO Hop Attributes subobject are subject to [RFC7570] and standard RRO processing; see [RFC3209].
4.2.2. WavelengthSelection Sub-TLV
Routing + Distributed Wavelength Assignment (R+DWA) is one of the options defined by [RFC6163]. The output from the routing function will be a path, but the wavelength will be selected on a hop-by-hop basis.
As discussed in [RFC6163], the wavelength assignment can be either for a unidirectional lightpath or for a bidirectional lightpath constrained to use the same lambda in both directions.
In order to indicate wavelength assignment directionality and wavelength assignment method, the WavelengthSelection sub-TLV is carried in the WSON Processing Hop Attribute TLV defined above.
The WavelengthSelection sub-TLV value field is defined as:
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |W| WA Method | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
W (1 bit): 0 denotes requiring the same wavelength in both
directions; 1 denotes that different wavelengths on both directions are allowed.
Wavelength Assignment (WA) Method (7 bits):
0: unspecified (any); This does not constrain the WA method used
by a specific node. This value is implied when the WavelengthSelection sub-TLV is absent.
1: First-Fit. All the wavelengths are numbered, and this WA
method chooses the available wavelength with the lowest index.
2: Random. This WA method chooses an available wavelength
3: Least-Loaded (multi-fiber). This WA method selects the wavelength that has the largest residual capacity on the most loaded link along the route. This method is used in multi- fiber networks. If used in single-fiber networks, it is equivalent to the First-Fit WA method.
The processing rules for this TLV are as follows:
If a receiving node does not support the attribute(s), its behaviors are specified below:
- W bit not supported: a PathErr MUST be generated with the Error Code "Routing Problem" (24) with error sub-code "Unsupported WavelengthSelection Symmetry value" (107).
- WA method not supported: a PathErr MUST be generated with the Error Code "Routing Problem" (24) with error sub-code "Unsupported Wavelength Assignment value" (108).
A WavelengthSelection sub-TLV can be constructed by a node and added to an ERO Hop Attributes subobject in order to be processed by downstream nodes (transit and egress). As defined in [RFC7570], the R bit reflects the LSP_REQUIRED_ATTRIBUTE and LSP_ATTRIBUTE semantic defined in [RFC5420], and it SHOULD be set accordingly.
Once a node properly parses the WavelengthSelection sub-TLV received in an ERO Hop Attributes subobject, the node use the indicated wavelength assignment method (at that hop) for the LSP. In addition, the node SHOULD report compliance by adding an RRO Hop Attributes subobject with the WSON Processing Hop Attribute TLV (and its sub- TLVs) that indicate the utilized method. WavelengthSelection sub- TLVs carried in an RRO Hop Attributes subobject are subject to [RFC7570] and standard RRO processing; see [RFC3209].
5. Security Considerations
This document is built on the mechanisms defined in [RFC3473], and only differs in the specific information communicated. The specific additional information (optical resource and wavelength selection properties) is not viewed as substantively changing or adding to the security considerations of the existing GMPLS signaling protocol mechanisms. See [RFC3473] for details of the supported security measures. Additionally, [RFC5920] provides an overview of security vulnerabilities and protection mechanisms for the GMPLS control plane.
6. IANA Considerations
IANA has assigned a new value in the existing "Attributes TLV Space" registry located at <http://www.iana.org/assignments/rsvp-te-parameters>, as updated by [RFC7570]: Type Name Allowed on Allowed on Allowed on Reference LSP LSP REQUIRED RO LSP ATTRIBUTES ATTRIBUTES Attribute Subobject 4 WSON No No Yes RFC 7689 Processing Hop Attribute TLV IANA has created a new registry named "Sub-TLV Types for WSON Processing Hop Attribute TLV" located at <http://www.iana.org/assignments/rsvp-te-parameters>.
The following entries have been added:
Value Sub-TLV Type Reference 0 Reserved RFC 7689 1 ResourceBlockInfo RFC 7689 2 WavelengthSelection RFC 7689
All assignments are to be performed via Standards Action or Specification Required policies as defined in [RFC5226].
IANA has created a new registry named "Values for Wavelength Assignment Method field in WavelengthSelection Sub-TLV" located at <http://www.iana.org/assignments/rsvp-te-parameters>.
The following entries have been added:
Value Meaning Reference 0 unspecified RFC 7689 1 First-Fit RFC 7689 2 Random RFC 7689 3 Least-Loaded (multi-fiber) RFC 7689 4-127 Unassigned
All assignments are to be performed via Standards Action or Specification Required policies as defined in [RFC5226]. The assignment policy chosen for any specific code point must be clearly stated in the document that describes the code point so that IANA can apply the correct policy.
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <http://www.rfc-editor.org/info/rfc2119>. [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001, <http://www.rfc-editor.org/info/rfc3209>. [RFC3471] Berger, L., Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Functional Description", RFC 3471, DOI 10.17487/RFC3471, January 2003, <http://www.rfc-editor.org/info/rfc3471>. [RFC3473] Berger, L., Ed., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol- Traffic Engineering (RSVP-TE) Extensions", RFC 3473, DOI 10.17487/RFC3473, January 2003, <http://www.rfc-editor.org/info/rfc3473>. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, DOI 10.17487/RFC5226, May 2008, <http://www.rfc-editor.org/info/rfc5226>. [RFC5420] Farrel, A., Ed., Papadimitriou, D., Vasseur, JP., and A. Ayyangarps, "Encoding of Attributes for MPLS LSP Establishment Using Resource Reservation Protocol Traffic Engineering (RSVP-TE)", RFC 5420, DOI 10.17487/RFC5420, February 2009, <http://www.rfc-editor.org/info/rfc5420>. [RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax Used to Form Encoding Rules in Various Routing Protocol Specifications", RFC 5511, DOI 10.17487/RFC5511, April 2009, <http://www.rfc-editor.org/info/rfc5511>. [RFC6205] Otani, T., Ed., and D. Li, Ed., "Generalized Labels for Lambda-Switch-Capable (LSC) Label Switching Routers", RFC 6205, DOI 10.17487/RFC6205, March 2011, <http://www.rfc-editor.org/info/rfc6205>. [RFC7570] Margaria, C., Ed., Martinelli, G., Balls, S., and B. Wright, "Label Switched Path (LSP) Attribute in the Explicit Route Object (ERO)", RFC 7570, DOI 10.17487/RFC7570, July 2015, <http://www.rfc-editor.org/info/rfc7570>. [RFC7581] Bernstein, G., Ed., Lee, Y., Ed., Li, D., Imajuku, W., and J. Han, "Routing and Wavelength Assignment Information Encoding for Wavelength Switched Optical Networks", RFC 7581, DOI 10.17487/RFC7581, June 2015, <http://www.rfc-editor.org/info/rfc7581>. [RFC7688] Lee, Y., Ed., and G. Bernstein, Ed., "GMPLS OSPF Enhancement for Signal and Network Element Compatibility for Wavelength Switched Optical Networks", RFC 7688, DOI 10.17487/RFC7688, November 2015, <http://www.rfc-editor.org/info/rfc7688>.
7.2. Informative References
[RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010, <http://www.rfc-editor.org/info/rfc5920>. [RFC6163] Lee, Y., Ed., Bernstein, G., Ed., and W. Imajuku, "Framework for GMPLS and Path Computation Element (PCE) Control of Wavelength Switched Optical Networks (WSONs)", RFC 6163, DOI 10.17487/RFC6163, April 2011, <http://www.rfc-editor.org/info/rfc6163>. [RFC7446] Lee, Y., Ed., Bernstein, G., Ed., Li, D., and W. Imajuku, "Routing and Wavelength Assignment Information Model for Wavelength Switched Optical Networks", RFC 7446, DOI 10.17487/RFC7446, February 2015, <http://www.rfc-editor.org/info/rfc7446>.
The authors would like to thanks Lou Berger, Cyril Margaria, and Xian Zhang for their comments and suggestions.
Nicola Andriolli Scuola Superiore Sant'Anna Pisa, Italy Email: email@example.com Alessio Giorgetti Scuola Superiore Sant'Anna Pisa, Italy Email: firstname.lastname@example.org
Key Laboratory of Optical Communication and Lightwave Technologies Ministry of Education
P.O. Box 128, Beijing University of Posts and Telecommunications China
Key Laboratory of Optical Communication and Lightwave Technologies Ministry of Education
P.O. Box 128, Beijing University of Posts and Telecommunications China
Daniel King Old Dog Consulting Email: email@example.com
Greg M. Bernstein (editor) Grotto Networking Fremont, CA United States Phone: (510) 573-2237 Email: firstname.lastname@example.org 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: email@example.com Young Lee (editor) Huawei Technologies 5340 Legacy Dr. Building 3 Plano, TX 75024 United States Phone: (469) 277-5838 Email: firstname.lastname@example.org Giovanni Martinelli Cisco Via Philips 12 20052 Monza Italy Phone: +39 039-209-2044 Email: email@example.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: firstname.lastname@example.org