Internet Engineering Task Force (IETF) Y. Lee, Ed. Request for Comments: 7446 Huawei Category: Informational G. Bernstein, Ed. ISSN: 2070-1721 Grotto Networking D. Li Huawei W. Imajuku NTT February 2015 Routing and Wavelength Assignment Information Model for Wavelength Switched Optical Networks Abstract This document provides a model of information needed by the Routing and Wavelength Assignment (RWA) process in Wavelength Switched Optical Networks (WSONs). The purpose of the information described in this model is to facilitate constrained optical path computation in WSONs. This model takes into account compatibility constraints between WSON signal attributes and network elements but does not include constraints due to optical impairments. Aspects of this information that may be of use to other technologies utilizing a GMPLS control plane are discussed. Status of This Memo This document is not an Internet Standards Track specification; it is published for informational purposes. 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). Not all documents approved by the IESG are a candidate for any level of Internet Standard; see 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/rfc7446. Lee, et al. Informational [Page 1] RFC 7446 WSON Information Model February 2015 Copyright Notice Copyright (c) 2015 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction ....................................................3 2. Terminology .....................................................3 3. Routing and Wavelength Assignment Information Model .............3 3.1. Dynamic and Relatively Static Information ..................4 4. Node Information (General) ......................................4 4.1. Connectivity Matrix ........................................5 5. Node Information (WSON Specific) ................................5 5.1. Resource Accessibility/Availability ........................7 5.2. Resource Signal Constraints and Processing Capabilities ...11 5.3. Compatibility and Capability Details ......................12 5.3.1. Shared Input or Output Indication ..................12 5.3.2. Optical Interface Class List .......................12 5.3.3. Acceptable Client Signal List ......................13 5.3.4. Processing Capability List .........................13 6. Link Information (General) .....................................13 6.1. Administrative Group ......................................14 6.2. Interface Switching Capability Descriptor .................14 6.6.1. Port-Wavelength Exclusivity Example ................17 7. Dynamic Components of the Information Model ....................18 7.1. Dynamic Link Information (General) ........................19 7.2. Dynamic Node Information (WSON Specific) ..................19 8. Security Considerations ........................................19 9. References .....................................................20 9.1. Normative References ......................................20 9.2. Informative References ....................................21 Contributors ......................................................22 Authors' Addresses ................................................23 Lee, et al. Informational [Page 2] RFC 7446 WSON Information Model February 2015 1. Introduction The purpose of the WSON information model described in this document is to facilitate constrained optical path computation, and as such it is not a general-purpose network management information model. This constraint is frequently referred to as the "wavelength continuity" constraint, and the corresponding constrained optical path computation is known as the Routing and Wavelength Assignment (RWA) problem. Hence, the information model must provide sufficient topology and wavelength restriction and availability information to support this computation. More details on the RWA process and WSON subsystems and their properties can be found in [RFC6163]. The model defined here includes constraints between WSON signal attributes and network elements but does not include optical impairments. In addition to presenting an information model suitable for path computation in WSON, this document also highlights model aspects that may have general applicability to other technologies utilizing a GMPLS control plane. The portion of the information model applicable to technologies beyond WSON is referred to as "general" to distinguish it from the "WSON-specific" portion that is applicable only to WSON technology. 2. Terminology Refer to [RFC6163] for definitions of Reconfigurable Optical Add/Drop Multiplexer (ROADM), RWA, Wavelength Conversion, Wavelength Division Multiplexing (WDM), WSON, and other related terminology used in this document. 3. Routing and Wavelength Assignment Information Model The WSON RWA information model in this document comprises four categories of information. The categories are independent of whether the information comes from a switching subsystem or from a line subsystem -- a switching subsystem refers to WSON nodes such as a ROADM or an Optical Add/Drop Multiplexer (OADM), and a line subsystem refers to devices such as WDM or Optical Amplifier. The categories are these: o Node Information o Link Information o Dynamic Node Information o Dynamic Link Information Lee, et al. Informational [Page 3] RFC 7446 WSON Information Model February 2015 Note that this is roughly the categorization used in Section 7 of [G.7715]. In the following, where applicable, the Reduced Backus-Naur Form (RBNF) syntax of [RBNF] is used to aid in defining the RWA information model. 3.1. Dynamic and Relatively Static Information All the RWA information of concern in a WSON network is subject to change over time. Equipment can be upgraded; links may be placed in or out of service and the like. However, from the point of view of RWA computations, there is a difference between information that can change with each successive connection establishment in the network and information that is relatively static and independent of connection establishment. A key example of the former is link wavelength usage since this can change with connection setup/teardown and this information is a key input to the RWA process. Examples of relatively static information are the potential port connectivity of a WDM ROADM, and the channel spacing on a WDM link. This document separates, where possible, dynamic and static information so that these can be kept separate in possible encodings. This allows for separate updates of these two types of information, thereby reducing processing and traffic load caused by the timely distribution of the more dynamic RWA WSON information. 4. Node Information (General) The node information described here contains the relatively static information related to a WSON node. This includes connectivity constraints amongst ports and wavelengths since WSON switches can exhibit asymmetric switching properties. Additional information could include properties of wavelength converters in the node, if any are present. In [Switch] it was shown that the wavelength connectivity constraints for a large class of practical WSON devices can be modeled via switched and fixed connectivity matrices along with corresponding switched and fixed port constraints. These connectivity matrices are included with the node information, while the switched and fixed port wavelength constraints are included with the link information. Formally, ::= [...] Where the Node_ID would be an appropriate identifier for the node within the WSON RWA context. Lee, et al. Informational [Page 4] RFC 7446 WSON Information Model February 2015 Note that multiple connectivity matrices are allowed and hence can fully support the most-general cases enumerated in [Switch]. 4.1. Connectivity Matrix The connectivity matrix (ConnectivityMatrix) represents either the potential connectivity matrix for asymmetric switches (e.g., ROADMs and such) or fixed connectivity for an asymmetric device such as a multiplexer. Note that this matrix does not represent any particular internal blocking behavior but indicates which input ports and wavelengths could possibly be connected to a particular output port. For a switch or ROADM, representing blocking that is dependent on the internal state is beyond the scope of this document. Due to its highly implementation-dependent nature, it would most likely not be subject to standardization in the future. The connectivity matrix is a conceptual M by N matrix representing the potential switched or fixed connectivity, where M represents the number of input ports and N the number of output ports. This is a "conceptual" matrix since the matrix tends to exhibit structure that allows for very compact representations that are useful for both transmission and path computation. Note that the connectivity matrix information element can be useful in any technology context where asymmetric switches are utilized. ::= Where is a unique identifier for the matrix. can be either 0 or 1 depending upon whether the connectivity is either fixed or switched. represents the fixed or switched connectivity in that Matrix(i, j) = 0 or 1 depending on whether input port i can connect to output port j for one or more wavelengths. 5. Node Information (WSON Specific) As discussed in [RFC6163], a WSON node may contain electro-optical subsystems such as regenerators, wavelength converters or entire switching subsystems. The model present here can be used in characterizing the accessibility and availability of limited Lee, et al. Informational [Page 5] RFC 7446 WSON Information Model February 2015 resources such as regenerators or wavelength converters as well as WSON signal attribute constraints of electro-optical subsystems. As such, this information element is fairly specific to WSON technologies. In this document, the term "resource" is used to refer to a physical component of a WSON node such as a regenerator or a wavelength converter. Multiple instances of such components are often present within a single WSON node. This term is not to be confused with the concept of forwarding or switching resources such as bandwidth or lambdas. A WSON node may include regenerators or wavelength converters arranged in a shared pool. As discussed in [RFC6163], a WSON node can also include WDM switches that use optical-electronic-optical (OEO) processing. There are a number of different approaches used in the design of WDM switches containing regenerator or converter pools. However, from the point of view of path computation, the following need to be known: 1. The nodes that support regeneration or wavelength conversion. 2. The accessibility and availability of a wavelength converter to convert from a given input wavelength on a particular input port to a desired output wavelength on a particular output port. 3. Limitations on the types of signals that can be converted and the conversions that can be performed. Since resources tend to be packaged together in blocks of similar devices, e.g., on line cards or other types of modules, the fundamental unit of identifiable resource in this document is the "resource block". A resource block is a collection of resources from the same WSON node that are grouped together for administrative reasons and for ease of encoding in the protocols. All resources in the same resource block behave in the same way and have similar characteristics relevant to the optical system, e.g., processing properties, accessibility, etc. A resource pool is a collection of resource blocks for the purpose of representing throughput or cross-connect capabilities in a WSON node. A resource pool associates input ports or links on the node with output ports or links and is used to indicate how signals may be passed from an input port or link to an output port or link by way of a resource block (in other words, by way of a resource). A resource pool may, therefore, be modeled as a matrix. Lee, et al. Informational [Page 6] RFC 7446 WSON Information Model February 2015 A resource block may be present in multiple resource pools. This leads to the following formal high-level model: ::= [...] [] Where ::= ... [...] [...] [] First, the accessibility of resource blocks is addressed; then, their properties are discussed. 5.1. Resource Accessibility/Availability A similar technique as used to model ROADMs, and optical switches can be used to model regenerator/converter accessibility. This technique was generally discussed in [RFC6163] and consisted of a matrix to indicate possible connectivity along with wavelength constraints for links/ports. Since regenerators or wavelength converters may be considered a scarce resource, it is desirable that the model include, if desired, the usage state (availability) of individual regenerators or converters in the pool. Models that incorporate more state to further reveal blocking conditions on input or output to particular converters are for further study and not included here. The three-stage model is shown schematically in Figures 1 and 2. The difference between the two figures is that in Figure 1 it's assumed that each signal that can get to a resource block may do so, while in Figure 2 the access to sets of resource blocks is via a shared fiber that imposes its own wavelength collision constraint. Figure 1 shows that there can be more than one input to each resource block since each input represents a single wavelength signal, while Figure 2 shows a single WDM input or output, e.g., a fiber, to/from each set of blocks. Lee, et al. Informational [Page 7] RFC 7446 WSON Information Model February 2015 This model assumes N input ports (fibers), P resource blocks containing one or more identical resources (e.g., wavelength converters), and M output ports (fibers). Since not all input ports can necessarily reach each resource block, the model starts with a resource pool input matrix RI(i,p) = {0,1} depending on whether input port i can potentially reach resource block p. Since not all wavelengths can necessarily reach all the resources or the resources may have limited input wavelength range, the model has a set of relatively static input port constraints for each resource. In addition, if the access to a set of resource blocks is via a shared fiber (Figure 2), this would impose a dynamic wavelength availability constraint on that shared fiber. The resource block input port constraint is modeled via a static wavelength set mechanism, and the case of shared access to a set of blocks is modeled via a dynamic wavelength set mechanism. Next, a state vector RA(j) = {0,...,k} is used to track the number of resources in resource block j in use. This is the only state kept in the resource pool model. This state is not necessary for modeling "fixed" transponder system or full OEO switches with WDM interfaces, i.e., systems where there is no sharing. After that, a set of static resource output wavelength constraints and possibly dynamic shared output fiber constraints maybe used. The static constraints indicate what wavelengths a particular resource block can generate or is restricted to generating, e.g., a fixed regenerator would be limited to a single lambda. The dynamic constraints would be used in the case where a single shared fiber is used to output the resource block (Figure 2). Finally, to complete the model, a resource pool output matrix RE(p,k) = {0,1} depending on whether the output from resource block p can reach output port k, may be used. Lee, et al. Informational [Page 8] RFC 7446 WSON Information Model February 2015 I1 +-------------+ +-------------+ O1 ----->| | +--------+ | |-----> I2 | +------+ Rb #1 +-------+ | O2 ----->| | +--------+ | |-----> | | | | | Resource | +--------+ | Resource | | Pool +------+ +-------+ Pool | | | + Rb #2 + | | | Input +------+ +-------| Output | | Connection | +--------+ | Connection | | Matrix | . | Matrix | | | . | | | | . | | IN | | +--------+ | | OM ----->| +------+ Rb #P +-------+ |-----> | | +--------+ | | +-------------+ ^ ^ +-------------+ | | | | | | | | Input wavelength Output wavelength constraints for constraints for each resource each resource Note: Rb is a resource block. Figure 1: Schematic Diagram of the Resource Pool Model Lee, et al. Informational [Page 9] RFC 7446 WSON Information Model February 2015 I1 +-------------+ +-------------+ O1 ----->| | +--------+ | |-----> I2 | +======+ Rb #1 +-+ | | O2 ----->| | +--------+ | | |-----> | | |=====| | | Resource | +--------+ | | Resource | | Pool | +-+ Rb #2 +-+ | Pool | | | | +--------+ | | | Input |====| | Output | | Connection | | +--------+ | Connection | | Matrix | +-| Rb #3 |=======| Matrix | | | +--------+ | | | | . | | | | . | | | | . | | IN | | +--------+ | | OM ----->| +======+ Rb #P +=======+ |-----> | | +--------+ | | +-------------+ ^ ^ +-------------+ | | | | | | Single (shared) fibers for block input and output Input wavelength Output wavelength availability for availability for each block input fiber each block output fiber Note: Rb is a resource block. Figure 2: Schematic Diagram of the Resource Pool Model with Shared Block Accessibility Formally, the model can be specified as: ::= ::= ::= [] [] Lee, et al. Informational [Page 10] RFC 7446 WSON Information Model February 2015 ::= [] [] Note that, except for , all the components of are relatively static. Also, the and are only used in the cases of shared input or output access to the particular block. See the resource block information in the next section for how this is specified. 5.2. Resource Signal Constraints and Processing Capabilities The wavelength conversion abilities of a resource (e.g., regenerator, wavelength converter) were modeled in the previously discussed. As discussed in [RFC6163], the constraints on an electro-optical resource can be modeled in terms of input constraints, processing capabilities, and output constraints: ::= [] [] [] Where is a list of resource block identifiers with the same characteristics. If this set is missing, the constraints are applied to the entire network element. The are constraints are based on signal compatibility and/or shared access constraint indication. The details of these constraints are defined in Section 5.3. ::= [] [] The are important operations that the resource (or network element) can perform on the signal. The details of these capabilities are defined in Section 5.3. Lee, et al. Informational [Page 11] RFC 7446 WSON Information Model February 2015 ::= [] [] [] [] The are either restrictions on the properties of the signal leaving the block, options concerning the signal properties when leaving the resource, or shared fiber output constraint indication. := [] [] 5.3. Compatibility and Capability Details 5.3.1. Shared Input or Output Indication As discussed in Section 5.2 and shown in Figure 2, the input or output access to a resource block may be via a shared fiber. The and elements are indicators for this condition with respect to the block being described. 5.3.2. Optical Interface Class List ::= ... The Optical Interface Class is a unique number that identifies all information related to optical characteristics of a physical interface. The class may include other optical parameters related to other interface properties. A class always includes signal compatibility information. The content of each class is out of the scope of this document and can be defined by other entities (e.g., the ITU, optical equipment vendors, etc.). Since even current implementation of physical interfaces may support different optical characteristics, a single interface may support multiple interface classes. Which optical interface class is used among all the ones available for an interface is out of the scope of this document but is an output of the RWA process. Lee, et al. Informational [Page 12] RFC 7446 WSON Information Model February 2015 5.3.3. Acceptable Client Signal List The list is simply: ::=[]... Where the Generalized Protocol Identifiers (G-PID) object represents one of the IETF-standardized G-PID values as defined in [RFC3471] and [RFC4328]. 5.3.4. Processing Capability List The ProcessingCapabilities are defined in Section 5.2. The processing capability list sub-TLV is a list of processing functions that the WSON network element (NE) can perform on the signal including: 1. number of resources within the block 2. regeneration capability 3. fault and performance monitoring 4. vendor-specific capability Note that the code points for fault and performance monitoring and vendor-specific capability are subject to further study. 6. Link Information (General) MPLS-TE routing protocol extensions for OSPF [RFC3630] and IS-IS [RFC5305], along with GMPLS routing protocol extensions for OSPF [RFC4203] and IS-IS [RFC5307] provide the bulk of the relatively static link information needed by the RWA process. However, WSONs bring in additional link-related constraints. These stem from characterizing WDM line systems, restricting laser transmitter tuning, and switching subsystem port wavelength constraints, e.g., "colored" ROADM drop ports. The following syntax summarizes both information from existing GMPLS routing protocols and new information that may be needed by the RWA process. Lee, et al. Informational [Page 13] RFC 7446 WSON Information Model February 2015 ::= [] [] [] [...] [] [...] Note that these additional link characteristics only apply to line- side ports of a WDM system or add/drop ports pertaining to the resource pool (e.g., regenerator or wavelength converter pool). The advertisement of input/output tributary ports is not intended here. 6.1. Administrative Group Administrative Group: Defined in [RFC3630] and extended for MPLS-TE [RFC7308]. Each set bit corresponds to one administrative group assigned to the interface. A link may belong to multiple groups. This is a configured quantity and can be used to influence routing decisions. 6.2. Interface Switching Capability Descriptor InterfaceSwCapDesc: Defined in [RFC4202]; lets us know the different switching capabilities on this GMPLS interface. In both [RFC4203] and [RFC5307], this information gets combined with the maximum Link State Protocol Data Unit (LSP) bandwidth that can be used on this link at eight different priority levels. 6.3. Link Protection Type (for This Link) Protection: Defined in [RFC4202] and implemented in [RFC4203] and [RFC5307]. Used to indicate what protection, if any, is guarding this link. 6.4. Shared Risk Link Group Information SRLG: Defined in [RFC4202] and implemented in [RFC4203] and [RFC5307]. This allows for the grouping of links into shared risk groups, i.e., those links that are likely, for some reason, to fail at the same time. Lee, et al. Informational [Page 14] RFC 7446 WSON Information Model February 2015 6.5. Traffic Engineering Metric TrafficEngineeringMetric: Defined in [RFC3630] and [RFC5305]. This allows for the identification of a data-channel link metric value for traffic engineering that is separate from the metric used for path cost computation of the control plane. Note that multiple "link metric values" could find use in optical networks; however, it would be more useful to the RWA process to assign these specific meanings such as "link mile" metric, "probability of failure" metric, etc. 6.6. Port Label Restrictions Port label restrictions could be applied generally to any label types in GMPLS by adding new kinds of restrictions. Wavelength is a type of label. Port label (wavelength) restrictions (PortLabelRestriction) model the label (wavelength) restrictions that the link and various optical devices, such as Optical Cross-Connects (OXCs), ROADMs, and waveband multiplexers, may impose on a port. These restrictions tell us what wavelength may or may not be used on a link and are relatively static. This plays an important role in fully characterizing a WSON switching device [Switch]. Port wavelength restrictions are specified relative to the port in general or to a specific connectivity matrix (Section 4.1). [Switch] gives an example where both switch and fixed connectivity matrices are used and both types of constraints occur on the same port. ::= ::= | |