Network Working Group G. Bernstein Internet Draft Grotto Networking Intended status: Standards Track Sugang Xu NICT Expires: April 2009 Y.Lee Huawei Hiroaki Harai NICT D. King October 31, 2008 Signaling Extensions for Wavelength Switched Optical Networks draft-bernstein-ccamp-wson-signaling-03.txt Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of 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." 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 April 31, 2007. Copyright Notice Copyright (C) The IETF Trust (2008). Abstract This memo provides extensions to Generalized Multi-Protocol Label Switching (GMPLS) signaling for control of wavelength switched optical Expires April 31, 2009 [Page 1] Internet-Draft WSON Signaling Extensions October 2008 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 RFC-2119[RFC2119]. Table of Contents 1. Introduction...................................................3 2. Terminology....................................................3 3. Requirements for WSON Signaling................................4 3.1.1. WSON Signal Characterization.........................4 3.1.2. Bi-Directional Distributed Wavelength Assignment.....4 3.1.3. Distributed Wavelength Assignment Support............5 3.1.4. Out of Scope.........................................6 4. WSON Signal Types, Forward Error Correction, and Rates.........6 4.1. Traffic Parameters for WSON signals.......................7 5. Bidirectional Lightpath using Same Wavelength..................8 5.1. Using LSP_ATTRIBUTES Object...............................9 5.2. Bidirectional Lightpath Signaling Procedure...............9 5.3. Backward Compatibility Considerations....................10 6. Bidirectional Lightpath using Different Wavelengths...........10 7. RWA Method Related............................................11 7.1. Wavelength Assignment Method Selection...................11 7.2. Supplemental Information for Wavelength Assignment.......11 7.3. Backward Blocking Reduction (informational)..............13 7.4. Efficient Wavelength Converter Utilization (informational)14 7.5. Efficient Backup Wavelength Utilization (informational)..14 7.6. Least-Loaded Wavelength Assignment (informational).......14 8. Security Considerations.......................................16 9. IANA Considerations...........................................16 10. Acknowledgments..............................................16 11. References...................................................17 11.1. Normative References....................................17 11.2. Informative References..................................17 Author's Addresses...............................................19 APPENDIX A: Requirement of Bidirectional Lightpath with the Same Wavelength in Both Directions....................................21 A.1. Introduction.............................................21 A.2. Port-remapping Problem...................................21 A.3. Port-remapping with OXC..................................24 A.4. Avoiding Port-remapping Problem: Bidirectional Lightpath using Same Wavelength on Both Directions......................25 Bernstein et al. Expires April 31, 2009 [Page 2] Internet-Draft WSON Signaling Extensions October 2008 Intellectual Property Statement..................................26 Disclaimer of Validity...........................................26 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 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. Bernstein et al. Expires April 31, 2009 [Page 3] Internet-Draft WSON Signaling Extensions October 2008 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. 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. 3.1.1. 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...), links (WDM systems) and end systems (detectors, demodulators, etc...). The details of any local configuration are out of the scope of this document. 3.1.2. 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 Appendix section, two edge relevant scenarios are described, i.e. without and with OXC at edges. In fact, the edges can be classified into two types, i.e. without and with the wavelength-port mapping re-configurability. Bernstein et al. Expires April 31, 2009 [Page 4] Internet-Draft WSON Signaling Extensions October 2008 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 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 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. 3.1.3. 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. Bernstein et al. Expires April 31, 2009 [Page 5] Internet-Draft WSON Signaling Extensions October 2008 WSON signaling SHOULD support mechanisms for the reduction of backwards blocking probabilities. In WSON without wavelength converters, the backward blocking due to resource contentions is the predominant blocking contribution, when traffic load is low or highly-dynamic and when lightpath restoration takes place. As shown in [Giorgetti08] a significant backward blocking reduction can be achieved if the wavelength assignment is performed in a distributed way during the forward signaling phase, with the objective of assigning disjoint wavelengths to reservation attempts that may contend the resources. WSON signaling SHOULD support mechanisms to aid in the efficient use of wavelength converters. To increase network utilization, OXC can be equipped with wavelength converters, allowing the setup of lightpaths even though no wavelength is globally available on the entire path. To limit node cost, the number of converters is usually very limited. As shown in [Andriolli06], still a relevant performance improvement can be achieved if converters are saved, using them only when no wavelength- continuous path is available. Preference can be then assigned to labels which ensure a wavelength continuous path. WSON signaling SHOULD support mechanisms to aid in the efficient use of wavelengths and blocking reduction when mesh restoration with backup paths is used [Ji]. Shared-Mesh Restoration [RFC4427] can be used to reduce recovery resource requirements by having backup lightpaths sharing wavelength resources when the working lightpaths which they protect are physically disjoint. Destination node of backup lightpath perform wavelength selection according to available wavelength. As shown in [Ji], using the wavelength sharing information collected along the backup lightpath, a reduction of backup wavelengths can be achieved by selecting the wavelength that can be shared on most hops of the backup lightpath. 3.1.4. Out of Scope This draft does not address signaling information related to optical impairments. 4. WSON Signal Types, Forward Error Correction, and Rates Although WSONs are fairly transparent to the signals they carry, to ensure compatibility amongst various networks devices and end systems Bernstein et al. Expires April 31, 2009 [Page 6] Internet-Draft WSON Signaling Extensions October 2008 it can be important to include key lightpath characteristics as traffic parameters in signaling [WSON-Frame]. 4.1. Traffic Parameters for WSON 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | BitRate/Analog Bandwidth | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Modulation (Mod) Types: We have potentially the following: Bernstein et al. Expires April 31, 2009 [Page 7] Internet-Draft WSON Signaling Extensions October 2008 Value Type ----- ---- 0 Unspecified or Unknown 1 NRZ 2 RZ Modulation Parameters(Mod Params): RZ 0 - 33%, 1 - 50%, 2 - 67% duty cycles 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/Analog Bandwidth: For digital signals this is the bit rate given as a 32 bit IEEE floating point number. For analog signals or when modulation type is given as 0 (unspecified), this is the bandwidth of the signal around the center frequency (c/lambda) and not the bit/byte rate. This is given as a 32 bit IEEE floating point number that represents the bandwidth in Hertz. The exact definition of bandwidth, e.g., 3dB power bandwidth, etc. is TBD and may be network specific. 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 3.1.2(a) gives us another constraint on wavelength usage in data plane, in particular, it requires the same wavelength to be used in both directions. Bernstein et al. Expires April 31, 2009 [Page 8] Internet-Draft WSON Signaling Extensions October 2008 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 [RFC4420] 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 [RFC4420] 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 [RFC4420] for detailed descriptions of the Flag and related issues. 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 Bernstein et al. Expires April 31, 2009 [Page 9] Internet-Draft WSON Signaling Extensions October 2008 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. 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 [RFC4420], 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 [RFC4420]. 6. Bidirectional Lightpath using Different Wavelengths TBD Bernstein et al. Expires April 31, 2009 [Page 10] Internet-Draft WSON Signaling Extensions October 2008 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 [RFC4420]. 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 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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 7.2. Supplemental Information for Wavelength Assignment Distributed wavelength assignment makes extensive use of the label set object/TLV of [RFC3471]. Some higher performance algorithms such as Least-Loaded assignment for multi-fiber networks, backward blocking avoidance assignment, efficient wavelength converter assignment and efficient backup wavelength assignment require supplemental information concerning the potential lambdas to be used. An ordered set of TLVs in correspondence with the group of one or more label set TLVs can be used to convey this information in the form of a general wavelength "acceptability" metric. Note that the label set syntax of [RFC3471] allows group of wavelengths into ranges. For the purpose of supplementing this information with wavelength count only those wavelengths with the same counts could be grouped. Bernstein et al. Expires April 31, 2009 [Page 11] Internet-Draft WSON Signaling Extensions October 2008 The general format for supplemental wavelength selection information could be as follows: The information carried in a Wavelength Set Metric TLV is: 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 | Strct | MSize | Num Metrics | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Wavelength Metric Info | | From lowest to highest frequency if more that one value | | ... | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Type: 8 bits The type field describes the use for these wavelength metrics. Note that multiple sets of metrics could possibly be used simultaneously. 0 - Backward blocking reduction [Giorgetti08] 1 - Wavelength converter assignment [Andriolli06] 2 - Most Sharable Wavelength per Segment mesh restoration wavelength assignment method [Ji] 3 - Least Loaded Wavelength Assignment Strct (Structure): 4 bits 0 - - Single Value The enclosed single value for the wavelength metric is given to all wavelengths in the corresponding wavelength set. 1 - - List The enclosed list gets applied in a one-to-one fashion to each wavelength in the corresponding wavelength set. An error occurs if the number of metrics in this list and the number of wavelengths in the wavelength set is not equal. Bernstein et al. Expires April 31, 2009 [Page 12] Internet-Draft WSON Signaling Extensions October 2008 Metric Size: Indicates the size of the wavelength metric information as follows 0 - - 8 bits 1 - - 16 bits 2 - - 32 bits Number 0f Metrics: 16 bits Wavelength Metric: (1, 2, or 4 octets) The wavelength metric represents in some fashion the desirability or lack thereof to use this wavelength over another available wavelength. Different wavelength assignment algorithms may use this information differently. 7.3. Backward Blocking Reduction (informational) Label preference schemes detailed in [Giorgetti08] can be implemented in a distributed way by exploiting the several RSVP-TE objects (i.e., Label Set, Suggested Label, Wavelength Assignment Indication TLV, and Wavelength Set Metric TLV.) with the aim of backward blocking reduction. The Wavelength Set Metric TLV is initialized by the source node. During provisioning, all the TLV entries are initialized at the same value. During restoration, a single entry of the TLV is strongly favored for avoiding contentions with other LSPs in restoration phase. The favored label is determined in function of the label that was used before the failure. The used mapping function must be biunique and should favor labels that have a low probability to be already reserved. The Wavelength Set Metric TLV is then updated by each intermediate node by considering the other on going RSVP-TE signaling instances. At destination the Wavelength Set Metric TLV contains a metric for each wavelength contained in the Label Set. The metric represents the risk of backward blocking in case the specific wavelength is selected. Therefore the wavelength assignment can be performed by minimizing the risk of backward blocking. Bernstein et al. Expires April 31, 2009 [Page 13] Internet-Draft WSON Signaling Extensions October 2008 7.4. Efficient Wavelength Converter Utilization (informational) The Wavelength converter saving wavelength assignment algorithm [Andriolli06] is a distributed algorithm which can be implemented via signaling by exploiting the Wavelength Set Metric TLV. For each label present in the label set, the Wavelength Set Metric contains the minimum number of wavelength conversions needed to use that label on the next hop. In other words, the Wavelength Set Metric is reset at source, since all wavelengths can be reached without requiring a wavelength conversion. If a wavelength can traverse an intermediate node without conversion, the relative Wavelength Set Metric value is kept constant. On the contrary, a wavelength busy on the previous hop and available on the next hop can be used only with a wavelength conversion. In this case the relative Wavelength Set Metric value is the minimum Wavelength Set Metric on the previous hop over all labels that can reach the current one with a wavelength conversion, incremented by one. 7.5. Efficient Backup Wavelength Utilization (informational) The Most Sharable Wavelength per Segment (MSWS) method [Ji] can perform efficient wavelength sharing in a distributed fashion. In this case the Wavelength Set Metric contains the number of hops that can be shared on for each available wavelength in Wavelength Set TLV. When limited wavelength converters are used in WSON, each backup lightpath may include one or more wavelength continuous segments. In the forward singling phase, if a wavelength can be shared with the current backup lightpath, the corresponding value in Wavelength Set Metric is incremented by one. The Wavelength Set Metric is reset at each head-end of a wavelength continuous segment, and stored at each tail-end. Notice that the destination node is always the tail-end of the last segment and it is responsible to perform wavelength selection for the last segment according to the wavelength sharing information in Wavelength Set Metric of its segment. On reception of the Resv message, the tail-end of each segment is responsible to perform wavelength selection for its own segment. 7.6. Least-Loaded Wavelength Assignment (informational) The Least-Loaded wavelength assignment algorithm [HZang00] can be implemented in a distributed fashion via signaling with the addition Bernstein et al. Expires April 31, 2009 [Page 14] Internet-Draft WSON Signaling Extensions October 2008 of channel count metric information. Least-loaded assignment applies to multi-fiber links hence the supplemental information pertains to the number of available channels at a particular wavelength. Hence the sub-channel metric of section 7.2. would simple be the channel count of a particular wavelength. The per node processing to implement the least-loaded assignment algorithm consists of receiving the label set and supplementary information TLVs (wavelengths and their channel counts) and taking the minimum of the received channel counts and the egress channel counts on a per wavelength basis. Where wavelengths with zero available channels will be discarded from the label set. The resulting channel counts and wavelength set will then be forwarded on to the next node for processing. For more details on least loaded wavelength assignment see [WSON-Frame] and [HZang00]. Example of Wavelength set and wavelength channel count metric. Suppose that in a 40 channel multi-fiber system and that the wavelengths (frequencies) have the following number of channels (this is a multi-fiber system) available: Frequency(THz) channels available ----------------------------------------- 192.0 3 192.5 2 193.1 1 193.9 2 194.0 2 195.2 1 195.8 1 We can then represent this list of available frequencies using the standard label set inclusive list. The wavelength metric list corresponding to this wavelength set would be given by: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Info Type=1 | M.Size = 0 | Num Metrics = 7 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 3 | 2 | 1 | 2 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 2 | 1 | 1 | Padded to 0 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Bernstein et al. Expires April 31, 2009 [Page 15] Internet-Draft WSON Signaling Extensions October 2008 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. Bernstein et al. Expires April 31, 2009 [Page 16] Internet-Draft WSON Signaling Extensions October 2008 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. [RFC4420] Farrel, A., Ed., Papadimitriou, D., Vasseur, J.-P., and A. Ayyangar, "Encoding of Attributes for Multiprotocol Label Switching (MPLS) Label Switched Path (LSP) Establishment Using Resource ReserVation Protocol-Traffic Engineering (RSVP-TE)", RFC 4420, 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 [Andriolli06] N. Andriolli et al., "Label preference schemes in GMPLS controlled networks," Communications Letters, IEEE, vol. 10, 2006, pp. 849-851. [Giorgetti08] Alessio Giorgetti, Nicola Sambo, Isabella Cerutti, Nicola Andriolli, and Piero Castoldi, "Label Preference Schemes for Lightpath Provisioning and Restoration in Distributed GMPLS Networks", to appear IEEE Journal of Lightwave Technology. Bernstein et al. Expires April 31, 2009 [Page 17] Internet-Draft WSON Signaling Extensions October 2008 [Ji] Yuefeng Ji and Lin Guo, "MSWS Method to Support Shared-Mesh Restoration for Wavelength Switched Optical Networks", work in progress: draft-ji-ccamp-wson-msws-00.txt, July 2008. [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. [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. Bernstein et al. Expires April 31, 2009 [Page 18] Internet-Draft WSON Signaling Extensions October 2008 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) Aria Networks 44/45 Market Place, Chippenham, SN15 3HU, United Kingdom Phone: +44 7790 775187 Email: daniel.king@aria-networks.com Bernstein et al. Expires April 31, 2009 [Page 19] Internet-Draft WSON Signaling Extensions October 2008 Young Lee (editor) Huawei Technologies 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 Bernstein et al. Expires April 31, 2009 [Page 20] Internet-Draft WSON Signaling Extensions October 2008 APPENDIX A: Requirement of Bidirectional Lightpath with the Same Wavelength in Both Directions A.1. Introduction With the Lambda Switch (LSC) support defined in GMPLS [RFC3471] and RSVP-TE signaling [RFC3473], by properly configuring the wavelength selective switching elements such as ROADMs or OXCs at the transit nodes, both unidirectional and bidirectional wavelength (optical lambdas) lightpaths can be established in a wavelength switched optical network (WSON). 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, there is another constraint on wavelength usage, say, require the same wavelength on both directions. This constraint might be introduced by carriers for a simplified management to reduce the OPEX. Moreover, according to some network hardware configurations, users' bidirectional lightpath has to use the same wavelength in both directions. For example, only a specific wavelength among the multiplexed wavelengths could be added/dropped to an optical end node. Some type of ROADMs may add/drop the same wavelength simultaneously. In particular, with some WSONs, if different wavelengths in two inverse directions are used, this brings a port-remapping problem, which is stated as follows. A.2. Port-remapping Problem This problem occurs in the following situations: (1) Fixed wavelength multiplexer/demultiplexer like AWGs may be employed in data plane at each node. Each incoming and outgoing wavelength is with a dedicated fixed port of AWG. For example, Bernstein et al. Expires April 31, 2009 [Page 21] Internet-Draft WSON Signaling Extensions October 2008 wavelength lambda 1 is on port 1, and wavelength lambda 2 is on port 2, and so on. See Fig.2.1. +--+ | |---> lambda 1: port 1 -->| |---> lambda 2: port 2 | |---> lambda 3: port 3 +--+ A. AWG Demultiplexer case. +--+ | |<--- lambda 1: port 1 <--| |<--- lambda 2: port 2 | |<--- lambda 3: port 3 +--+ B. AWG Multiplexer case. Fig.2.1. The fixed wavelength-port mapping of AWG Multiplexer/Demultiplexer. (2) Compared to a wavelength-tunable optical transponder array, low cost fixed-tuned optical transponder array may be employed at the edge node. In an optical transponder, the optical responder is bound with the transmitter. Each of the optical transmitters and responders are physically connected to one port of AWG or OXC according to the hardware configuration. See Fig.2.2. +--+ +----+ | |<---lambda 1---| T1 | <--| |<---lambda 2---| T2 | | |<---lambda 3---| T3 | +--+ +----+ AWG Multiplexer optical transmitter array A. The configuration with the optical transmitters connecting AWG. +--+ +----+ | |---lambda 1--->| R1 | -->| |---lambda 2--->| R2 | | |---lambda 3--->| R3 | +--+ +----+ AWG Demultiplexer optical responder array Bernstein et al. Expires April 31, 2009 [Page 22] Internet-Draft WSON Signaling Extensions October 2008 B. One possible configuration with the optical responders connecting AWG. +--+ +-----+ +----+ | |--->| |--->| R1 | -->| |--->| OXC |--->| R2 | | |--->| |--->| R3 | +--+ +-----+ +----+ AWG Demultiplexer optical responder array C. One possible configuration with the optical responders connecting OXC. Fig.2.2. The fixed optical transmitter/responder- AGW/OXC port mapping at the optical end nodes. Consider a bidirectional lightpath with different wavelengths on two directions. The optical transmitter of which output wavelength is the same as the outgoing-wavelength (say lambda 1) is chosen first for using the lightpath. Then, the optical responder attached to that transmitter should be selected for receiving the incoming wavelength (say lambda 2). The responder generally can receive any of different wavelengths. Therefore, if another bidirectional lightpath is assigned the same outgoing wavelength (lambda 1) but with a different incoming wavelength (say lambda 3), the same transmitter and responder pair is selected. See Fig.2.3. +----+ <-lambda 1---| T1 | +----+ A. Optical transmitter T1 sends optical signals on lambda 1. +----+ -lambda 2--->| R1 | +----+ B. Optical responder R1 receives optical signals on lambda 2 for one bidirectional lightpath. +----+ -lambda 3--->| R1 | +----+ C. Optical responder R1 can receive optical signals on lambda 3 for another bidirectional lightpath. Bernstein et al. Expires April 31, 2009 [Page 23] Internet-Draft WSON Signaling Extensions October 2008 Fig.2.3. Transmitter sends optical signals on the fixed-tuned wavelength; the responder can receive data on different wavelengths. However, the communication using the transponder and the bidirectional lightpath with different wavelengths will not succeed under the situations (1) and (2) mentioned above. Remember the fixed port mapping that each incoming wavelength is fixed on a unique port of AWG due to the situation (1), and the optical responder is also fixedly connected to a unique port of AWG or OXC due to the situation (2). Conversely, the incoming wavelength may change every lightpath (see lambda 2 and lambda 3 in the above case) for the same outgoing wavelength (lambda 1). The current incoming wavelength (lambda 3) is not on the port of AWG to which the optical responder connects originally (lambda 2), see Fig. 2.4. To connect the optical responder to the proper port on which the incoming wavelength is, even in different outgoing wavelengths, a port-remapping process between the optical responder and AWG ports may be required. +--+ +----+ | |<---lambda 1---| T1 | <--| |<---lambda 2---| T2 | | |<---lambda 3---| T3 | +--+ +----+ AWG Multiplexer A. Optical transmitter T1 sends optical signals on lambda 1. +--+ | |-- +----+ -->| |--lambda2---->| R1 | | |--lambda3-X +----+ +--+ AWG Demultiplexer B. Optical responder R1 cannot receive optical signals on lambda 3 due to the fixed port mapping, in case of that R1 is physically connected to the port 2 of lambda 2 on AWG. Fig.2.4. Port-remapping problem occurs due to the fixed port-mapping between the optical responder and AWG port. A.3. Port-remapping with OXC The port-remapping capability depends on the system configurations at users' optical end nodes. For example, an OXC may be employed to switch the incoming wavelength from the port of AWG to the port which the optical responder is connected physically, see Fig. 3.1. Bernstein et al. Expires April 31, 2009 [Page 24] Internet-Draft WSON Signaling Extensions October 2008 However, equipping users' optical end nodes with OXCs introduces extra costs. There exists a trade-off between port-remapping capability and cost/system complexity. +--+ +-------+ +----+ | |-lambda 1-->| /--|--->| R1 | -->| |-lambda 2-->|---/ |--->| R2 | | |-lambda 3-->| OXC |--->| R3 | +--+ +-------+ +----+ AWG Demultiplexer A. The optical responder R1 can receive the optical signals on lambda 2. +--+ +-------+ +----+ | |-lambda 1-->| /---|--->| R1 | -->| |-lambda 2-->| / |--->| R2 | | |-lambda 3-->|-/ OXC |--->| R3 | +--+ +-------+ +----+ AWG Demultiplexer B. The optical responder R1 can receive the optical signals on lambda 3. Fig.3.1. The port-remapping capability provided by OXC. Users have various types of optical end node configurations to choose from. Some configurations such as those equipped with OXCs might provide flexibility but could be costly and potentially complicated. Equally, while other configurations without OXCs might lack the flexibility they may be inexpensive and easy to use and maintain. A.4. Avoiding Port-remapping Problem: Bidirectional Lightpath using Same Wavelength on Both Directions Which solution will be employed depends on the considerations of the flexibility and cost/complexity trade-off. If users do not have port-remapping capability at optical end nodes, then it is necessary to avoid the port-remapping, and find a feasible approach to provide users full-duplex transmission capability with bidirectional lightpath. A feasible approach is to establish a bidirectional lightpath with the same wavelength on both directions. At the optical end node, fixed-tuned transponder array is connected to the proper ports of AWG according to the wavelength. Optical transmitter and responder pair connecting the selected outgoing and incoming wavelength ports of AWG will be assigned to the bidirectional lightpath. In this situation, Bernstein et al. Expires April 31, 2009 [Page 25] Internet-Draft WSON Signaling Extensions October 2008 the bidirectional lightpath with the same wavelength on both directions is required. Intellectual Property Statement The IETF 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 described in this 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. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Bernstein et al. Expires April 31, 2009 [Page 26] Internet-Draft WSON Signaling Extensions October 2008 Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Bernstein et al. Expires April 31, 2009 [Page 27]