Internet Engineering Task Force R. Kunze, Ed. Internet-Draft Deutsche Telekom Intended status: Informational G. Grammel, Ed. Expires: December 13, 2018 Juniper D. Beller Nokia G. Galimberti, Ed. Cisco J. Meuric Orange June 11, 2018 A framework for Management and Control of DWDM optical interface parameters draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 Abstract The control and management of DWDM interfaces are a precondition for enhanced multilayer networking. They are needed to ensure an efficient data transport, to meet the requirements requested by today's IP-services and to provide a further automation of network provisioning and operations. This document describes use cases, requirements and solutions for the control and management of optical interface parameters according to different types of single channel DWDM interfaces. The focus is on automating the network provisioning process irrespective on how it is triggered i.e. by Element Manager System (EMS), Network Management System (NMS) or Generalized Multi Protocol Label Switching (GMPLS). This document covers management and control considerations in different scenarios of single channel DWDM interfaces. The purpose is to identify the necessary information and processes to be used by control or management systems to properly and efficiently drive the network. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any Kunze, et al. Expires December 13, 2018 [Page 1] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on December 13, 2018. Copyright Notice Copyright (c) 2018 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 (https://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 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 2. Terminology and Definitions . . . . . . . . . . . . . . . . . 4 3. Solution Space . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Comparison of Approaches for Transverse Compatibility . . 6 3.1.1. Multivendor DWDM Line System with Transponders . . . 6 3.1.2. Integrated Single Channel DWDM Deployments on the Client Site . . . . . . . . . . . . . . . . . . . . . 7 4. Solutions for Managing and Controlling Single Channel Optical Interface . . . . . . . . . . . . . . . . . . . . . . . . . . 9 4.1. Separate Operation and Management Approaches . . . . . . 10 4.1.1. Direct Connection to the Management System . . . . . 10 4.1.2. Indirect Connection to the DWDM Management System (First Optical Node) . . . . . . . . . . . . . . . . 11 4.2. Control Plane Considerations . . . . . . . . . . . . . . 13 4.2.1. Considerations Using GMPLS Signaling . . . . . . . . 14 5. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 15 5.1. Service Setup . . . . . . . . . . . . . . . . . . . . . . 15 5.2. Link Monitoring Use Cases . . . . . . . . . . . . . . . . 16 5.2.1. Pure Access Link (AL) Monitoring Use Case . . . . . . 19 5.2.2. Power Control Loop Use Case . . . . . . . . . . . . . 21 6. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 23 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 25 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 25 9. Security Considerations . . . . . . . . . . . . . . . . . . . 25 10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 25 Kunze, et al. Expires December 13, 2018 [Page 2] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 26 11.1. Normative References . . . . . . . . . . . . . . . . . . 26 11.2. Informative References . . . . . . . . . . . . . . . . . 28 Appendix A. Appendix . . . . . . . . . . . . . . . . . . . . . . 29 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 29 1. Introduction The usage of external single channel Dense Wavelenght Division Multiplexing (DWDM) interfaces (e.g. in routers) connected to a DWDM Network (e.g. router connected to a network of Reconfigurable Optical Add Drop Multiplexers (ROADM) and optical amplifiers) adds a further networking option for operators but requires an harmonised control and management plane interaction between the different network domains. Carriers deploy their networks today based on transport and packet network infrastructures as domains to ensure high availability and a high level of redundancy combining the Packet and Transport restoration. Both network domains were operated and managed separately. This is the status quo in many carrier networks today. In the case of deployments where the optical transport interface moves into the client device (e.g. router) an interaction between those domains becomes necessary (e.g. Lambda reprovisioning due to an optical restoration). This framework specifies different levels of control and management plane interaction to support the usage of single channel optical interfaces in carrier networks in an efficient manner. The interfaces between the two layers can be either gray or coloured. Although Optical routing and wavelength assignment based on Wavelenght Switched Optical Network (WSON) is out of scope, they can benefit from the optical parameters that are exchanged between the Client and the DWDM Network. Also, the wavelength ordering process and determining the demand for a new wavelength path through the network are out of scope. The GMPLS and PCE functions will use the information collected from the Client and the DWDM network, the definition on how PCE and GMPLS can use the information and cooperate to implement RWA and circuit/service provisioning ar aout of scope of this document. Note that the Control and Management Planes are two separate entities that may handle the same information in different ways. Kunze, et al. Expires December 13, 2018 [Page 3] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 1.1. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP_14, RFC 2119 [RFC2119], RFC 8174 [RFC8174] when, and only when, they appear in all capitals, as shown here. While RFC 2119 [RFC2119] RFC 8174 [RFC8174] describe interpretations of these key words in terms of protocol specifications and implementations, they are used in this document to describe design requirements for protocol extensions. 2. Terminology and Definitions The current generation of Wavelenght Division Multiplexing (WDM) networks are single vendor networks where the optical line system and the transponders are tightly integrated. The DWDM interface migration from integrated transponders to third party transponders or colored interfaces change this scenario and introduces a standardized interface at the level of OCh between the DWDM interface and the DWDM network. Black Link: The Black Link [ITU-T.G.698.2] allows supporting an optical transmitter/receiver pair (of a single vendor or from different vendors) to provide a single optical channel interface and transport it over an optical network composed of amplifiers, filters, add-drop multiplexers these being possibly from different vendors. Therefore the standard defines the ingress and egress parameters for the optical interfaces at the reference points Source side (Ss) and Receive side (Rs). Single Channel DWDM Interface: The single channel interfaces to DWDM systems defined in [ITU-T.G.698.2], which currently include the following features: channel frequency spacing: 50 GHz and wider (defined in [ITU-T.G.694.1] ); bit rate of single channel: Up to 10 Gbit/s. Future revisions are expected to include application codes for bit rates up to 40 Gb/s. Forward Error Correction (FEC): FEC is a way of improving the performance of high-capacity optical transmission systems. Employing FEC in optical transmission systems yields system designs that can accept relatively large BER (much more than 10^-12) in the optical transmission line (before decoding). Administrative domain [ITU-T.G.805]: the extent of resources which belong to a single player such as a network operator, a service Kunze, et al. Expires December 13, 2018 [Page 4] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 provider or an end-user. Administrative domains of different players do not overlap amongst themselves. Intra-domain interface (IaDI) [ITU-T.G.872]: A physical interface within an administrative domain. Inter-domain interface (IrDI) [ITU-T.G.872]: A physical interface that represents the boundary between two administrative domains. Management Plane [ITU-T.G.8081],: The management plane performs management functions for the transport plane, the control plane and the system as a whole. It also provides coordination between all the planes. The following management functional areas are performed in the management plane: performance management, fault management, configuration management, accounting management and security management. Control Plane [ITU-T.G.8081]: Through signaling, the control plane sets up and releases connections, may restore a connection in case of a failure, and also performs other functions (e.g., neighbor discovery, topology distribution) in support of those. Transponder: A Transponder is a network element that performs O/E/O (Optical /Electrical/Optical) conversion. In this document it is referred only transponders with 3R (rather than 2R or 1R regeneration) as defined in [ITU-T.G.872]. Line System: A Line System is a portion of the network including Reconfigurable Add Drop Multiplexers (ROADM) Line Amplifiers and the the fibers connecting them. Client DWDM interface: A Transceiver element that performs E/O (Electrical/Optical) conversion. In this document it is referred as the DWDM side of a transponder as defined in [ITU-T.G.872]. 3. Solution Space The solution space of this document is focusing on aspects related to the management and control of single-channel optical interface parameters of physical point-to-point and ring DWDM applications on single-mode optical fibres and allows the direct connection of a wide variety of equipment using a DWDM link, for example 1. A digital cross-connect with multiple optical interfaces, supplied by a different vendor from the line system 2. Devices as routing, switching or compute nodes, each from a different vendor, providing optical line interfaces Kunze, et al. Expires December 13, 2018 [Page 5] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 3. A combination of the above 3.1. Comparison of Approaches for Transverse Compatibility This section describes two ways to achieve transverse compatibility. Section 3.1.1 describes the classic model based on well defined inter-domain interfaces. Section 3.1.2 defines a model ensuring interoperability on the line side of the optical network. 3.1.1. Multivendor DWDM Line System with Transponders As illustrated in Figure 1, for this approach interoperability is achieved via the use of optical transponders providing OEO (allowing conversion to appropriate parameters). The optical interfaces can then be any short reach standardized optical interface that both vendors support, such as those found in [ITU-T.G.957], [ITU-T.G.691], [ITU-T.G.693], etc. IrDI IaDI | | . . | +----------------------------|----+ . | + WDM Domain + . | | | |\ /| | | +------+ . | | \ |\ / | . | +------+ | TX/ |-->--+---+--T/-|OM|----|/-------|OD|--+-\T-+---->--| RX/ | | RX |--<--+---+--T/-| |----- /|-----| |--.-\T-+----<--| TX | +------+ | | | / \| \ | | | +------+ . | |/ \| . | | | + + | | . +----------------------------.----+ | | TX/RX = Single channel non-DWDM interfaces T/ = Transponder OM = Optical Mux OD = Optical Demux Figure 1: Inter and Intra-Domain Interface Identification In the scenario of Figure 1 the administrative domain is defined by the Interdomain Interface (IrDI). This interface terminates the DWDM domain. The line side is characterized by the IaDI. This interface specifies the internal parameter set of the optical administrative Kunze, et al. Expires December 13, 2018 [Page 6] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 domain. In the case of a client DWDM interface deployment this interface moves into the client device and extends the optical and administrative domain towards the client node. [ITU-T.G.698.2] for example specifies a set of parameter set for a certain set of applications. This document elaborates only the IaDI (Intra Domain Interface) as shown in Figure 1 as DWDM transversely compatible and multi-vendor interface within one administrative domain controlled by the network operator. SNMP/Simple Management Interface (SMI), NETCONF/RESTCONF and Link Management Protocol (LMP) TLV to support the direct exchange of information between the client and the network management and control plane will be specified in further documents. The YANG based NETCONF and RESTCONF protocol are better suited for creating and modifying configuration state and thus RECOMMENDED to be used over SNMP MIB. The SNMP MIB creating and modifying configuration state could be used for legacy network. 3.1.2. Integrated Single Channel DWDM Deployments on the Client Site In case of a deployment as shown in Figure 2, through the use of DWDM interfaces, multi-vendor interconnection can also be achieved. Among the possible use cases, it may be used to remove the need for one short reach transmitter and receiver pair per channel (eliminating the transponders). Kunze, et al. Expires December 13, 2018 [Page 7] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 Figure 2 shows a set of reference points, for single-channel connection (Ss and Rs) between transmitters (Tx) and receivers (Rx). Here the DWDM network elements include an optical multiplexer (OM) and an optical demultiplexer (OD) (which are used as a pair with the peer element), one or more optical amplifiers and may also include one or more ROADMs. |==================== Black Link =======================| +-------------------------------------------------+ Ss | | DWDM Network Elements | | Rs +---+ | | | \ / | | | +---+ Tx L1---|->| \ +------+ +------+ / |--|-->Rx L1 +---+ | | | | | +------+ | | | | | +---+ +---+ | | | | | | | | | | | | +---+ Tx L2---|->| OM |-|>|------|->| ROADM|--|------|->| OD |--|-->Rx L2 +---+ | | | | | | | | | | | | +---+ +---+ | | | | | +------+ | | | | | +---+ Tx L3---|->| / | DWDM | | ^ | DWDM | \ |--|-->Rx L3 +---+ | | / | Link +----|--|----+ Link | \ | | +---+ +-----------+ | | +----------+ +--+ +--+ |==== Black Link ====| | | v | +-----+ +-----+ |RxLx | |TxLx | +-----+ +-----+ Ss = Reference point at the DWDM network element tributary output Rs = Reference point at the DWDM network element tributary input Lx = Lambda x OM = Optical Mux OD = Optical Demux ROADM = Reconfigurable Optical Add Drop Mux Linear DWDM network as per ITU-T G.698.2 Figure 2: Linear Black Link The single administrative domain may consist of several vendor domains. Even in that case a common network management and control is required to ensure a consistent operation and provisioning of the entire connection. Kunze, et al. Expires December 13, 2018 [Page 8] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 SNMP/SMI, NETCONF/RESTCONF and LMP TLV to support the direct exchange of information between the client and the network management and control plane will be specified in further documents. 4. Solutions for Managing and Controlling Single Channel Optical Interface Operation and management of WDM systems is traditionally seen as a homogenous group of tasks that could be carried out best when a single management system or a hierarchical management system is used. Currently each WDM vendor provides an Element Management System (EMS) that also provisions the wavelengths. In a multi-vendor line system, such single-vendor EMS requirement is no more effective. New methods of managing and controlling line systems need to be looked at. Therefore from the operational point of view the following approaches will be considered to manage and operate optical interfaces. 1. Separate operation and management of client device and the transport network whereas the interface of the client belongs to the administrative domain of the transport network and will be managed by the transport group. This results in two different approaches to send information to the management system a. Direct connection from the client node to the transport management system, ensuring a management of the DWDM interface of the optical network (e.g. EMS, NMS) b. Indirect connection to the management system of the optical network using a protocol (e.g. LMP) between the client device and the directly connected WDM system node to exchange management information with the optical domain 2. Common operation and management of client device including the single channel DWDM part and the Transport network The first option keeps the status quo in large carrier networks as mentioned above. In that case it must be ensured that the full FCAPS Management (Fault, Configuration, Accounting, Performance and Security) capabilities are supported. This means from the management staff point of view nothing changes. The transceiver/receiver optical interface will be part of the optical management domain and will be managed from the transport management staff. The second solution addresses the case where underlying WDM transport network is mainly used to interconnect a homogeneous set of client nodes (e.g. IP routers or digital crossconnects). Since the service creation and restoration could be done by the higher layers (e.g. Kunze, et al. Expires December 13, 2018 [Page 9] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 IP), this may lead to an efficient network operation and a higher level of integration. 4.1. Separate Operation and Management Approaches 4.1.1. Direct Connection to the Management System As depicted in Figure 3 (case 1a) one possibility to manage the optical interface within the client domain is a direct connection to the management system of the optical domain. This ensures manageability as usual. +-----+ | NMS | |_____| /_____/ | | | +---+---+ +----->+ EMS | / | | / +-------+ / | MI SNMP or NETCONF/RESTCONF SNMP / or NETCONF | DCN Network --------------------+------------------------------- / +------+-----------------------+ / | +| WDM Domain + | / | |\ /| | +---+--+ | | \ |\ / | | +------+ | CL |-/C------+-----|OM|----|/-------|OD|----+-------/C-| CL | | |-/C------+-----| |----- /|-----| |----+-------/C-| | +------+ | | / \| \ | | +------+ | |/ \| | | + + | +------------------------------+ CL = Client Device /C = Single Channel Optical Interface OM = Optical Mux OD = Optical Demux EMS = Element Management System MI = Management Interface DCN = Data Control Network Figure 3: Connecting Single Channel optical interfaces to the Transport Management system Kunze, et al. Expires December 13, 2018 [Page 10] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 The exchange of management information between client device and the management system assumes that some form of a direct management communication link exists between the client device and the DWDM management system (e.g. EMS). This may be an Ethernet Link or a DCN connection (management communication channel MCC). It must be ensured that the optical network interface can be managed in a standardized way to enable interoperable solutions between different optical interface vendors and vendors of the optical network management application. [RFC3591] defines managed objects for the optical interface type but needs further extension to cover the optical parameters required by this framework document. Is to be noted that the CL (client device) and the DWDM network are belonging to the same operator so the DWDM EMS and the Client devices are connected to the same DCN and the communication security considerations are applicable to CL as per DWDM devices. Note that a software update of the optical interface components of the client nodes must not lead obligatory to an update of the software of the EMS and vice versa. 4.1.2. Indirect Connection to the DWDM Management System (First Optical Node) Kunze, et al. Expires December 13, 2018 [Page 11] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 An alternative as shown in Figure 4 should be used in cases where a more integrated relationship between transport node (e.g. OM or OD or ROADM) and client device is aspired. In that case a combination of control plane features and manual management will be used. +-----+ | NMS | |_____| /_____/ | | +---+---+ | EMS | | | +-------+ | MI SNMP or NETCONF/RESTCONF | LMP +------+-----------------------+ +------------+---+ +| + | | | | |\ /| | +---+--+ | +-+ \ |\ / | | +------+ | CL |-/C------+--- -|OM|----|/-------|OD|--- +-------/C-| CL | | |-/C------+--- -| |----- /|-----| |----+-------/C-| | +------+ | | / \| \ | | +------+ | |/ \| | | + + | +------------------------------+ CL = Client Device /C = Single Channel optical Interface OM = Optical Mux OD = Optical Demux EMS= Element Management System MI= Management Interface Figure 4: Direct connection between peer node and first optical network node For information exchange between the client node and the direct connected node of the optical transport network LMP as specified in RFC 4209 [RFC4209] should be used. This extension of LMP may be used between a peer node and an adjacent optical network node as depicted in Figure 4. At the time of writing this document, LMP does not yet support the transmission of configuration data (information). This functionality would need to be added to the protocol. The use of LMP assumes that Kunze, et al. Expires December 13, 2018 [Page 12] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 some form of a control channel exists between the client node and the WDM equipment. This may be a dedicated lambda or an Ethernet Link. 4.2. Control Plane Considerations The concept of integrated single channel DWDM interfaces equally applies to management and control plane mechanisms. GMPLS control plane protocols have been extended for WSON, e.g. RFC 7689 [RFC7689] ) for fixed grid signal and for flexi-grid RFC 7792 [RFC7792] ). One important aspect of the Black Link [ITU-T.G.698.2] is the fact that it includes the wavelength that is supported by the given link. Therefore, the link can logically be considered as a fiber that is transparent only for a single wavelength. In other words, the wavelength becomes a characteristic of the link itself. Nevertheless the procedure to light up the fiber may vary depending on the implementation. Since the implementation is unknown a priori, different sequences to light up a wavelength need to be considered: 1. Interface first, interface tuning: The transmitter is switched on and the link is immediately transparent to its wavelength. This requires the transmitter to carefully tune power and frequency not overload the line system or to create transients. 2. Interface first, Optical Line System (OLS) tuning: The transmitter is switched on first and can immediately go to the max power allowed since the OLS performs the power tuning. This leads to an intermediate state where the receiver does not receive a valid signal while the transmitter is sending out one. Alarm suppression mechanisms shall be employed to overcome that condition. 3. OLS first, interface tuning: At first the OLS is tuned to be transparent for a given wavelength, then transponders need to be tuned up. Since the OLS in general requires the presence of a wavelength to fine-tune its internal facilities there may be a period where a valid signal is transmitted but the receiver is unable to detect it. This equally need to be covered by alarm suppression mechanisms. 4. OLS first, OLS tuning: The OLS is programmed to be transparent for a given wavelength, then the interfaces need to be switched on and further power tuning takes place. The sequencing of enabling the link needs to be covered as well. The preferred way to address these in a Control Plane enabled network is neighbour discovery including exchange of link characteristics and link property correlation. The general mechanisms are covered in RFC Kunze, et al. Expires December 13, 2018 [Page 13] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 4209 [RFC4209] and RFC 4204 [RFC4204] which provides the necessary protocol framework to exchange those characteristics between client and Black Link. LMP-WDM is not intended for exchanging routing or signaling information nor to provision the lambda in the transceiver but covers: 1. Control channel management 2. Link property correlation 3. Link verification 4. Fault management Extensions to LMP covering the parameter sets (e.g. application codes) are needed. Additionally, when client and server side are managed by different operational entities, the link state may be useful to help the management system to do troubleshooting or alarm correlation. 4.2.1. Considerations Using GMPLS Signaling The deployment of single channel optical interfaces is leading to some functional changes related to the control plane models and has therefore some impact on the existing interfaces especially in the case of a model where the edge node requests resources from the core node and the edge node do not participate in the routing protocol instance that runs among the core nodes. RFC 4208 [RFC4208] defines the GMPLS UNI that can be used between edge and core node. In case of integrated interfaces deployment additional functionalities are needed to setup a connection. It is necessary to differentiate between topology/signalling information and configuration parameters that are needed to setup a wavelength path. Using RSVP-TE could be used for the signalling and the reservation of the wavelength path. But there are additional information needed before RSVP-TE can start the signalling process. There are three possibilities to proceed: a. Using RSVP-TE only for the signalling and LMP as described above to exchange information on the configured optical interface within the edge node b. RSVP-TE (typically with loose ERO) to transport additional information Kunze, et al. Expires December 13, 2018 [Page 14] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 c. Leaking IGP information instead of exchanging this information needed from the optical network to the edge node (UNI will be transformed to a border-peer model, see RFC 5146 [RFC5146] ) Furthermore following issues should be addressed: a) The transceivers of peering edge nodes must be compatible. For example, it may be required to know about FEC, modulation scheme, The modulation format, the baudrate and many other parameters described in the drafts reported in the Annex. Depending on where the information is available, compatibility check may either happen before signaling, when the signaling reaches the optical network (e.g. at path computation time), or in the tail end node. An extended version of LMP is needed to exchange this information in case a. above, and to RSVP-TE as well in b. It would be helpful to define some common profiles that will be supported (e.g. the "application identifier") to summarize interface capabilities: if both profiles match, signaling can succeed and provisioning be achieved. b) Due to the bidirectional wavelength path that must be setup, the upstream edge node must include a wavelength value into the RSVP-TE Path message. But in the case of a UNI model the client device may not have full information about which wavelength must/should be selected, whereas this information must be exchanged between the edge and the core node. The special value defined in [Network-Assigned-Upstream-Label] allows the optical network to assign the actual wavelength to be used by the upstream transponder, which is a simple and efficient solution to this issue. 5. Use Cases A comparison with the traditional operation scenarios provides an insight of similarities and distinctions in operation and management of DWDM interfaces. The following use cases provide an overview about operation and maintenance processes. 5.1. Service Setup It is necessary to differentiate between different operational issues for setting up a light path (a DWDM connection is specific in having defined maximum impairments) within an operational network. The first step is to determine if transceivers located at different end-points are interoperable, i.e. support a common set of operational parameters. In this step it is required to determine transceiver capabilities in a way to be able to correlate them for interoperability purposes. Such parameters include modulation Kunze, et al. Expires December 13, 2018 [Page 15] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 scheme, modulation parameters, FEC to name a few. If both transceivers are controlled by the same NMS or CP, such data is readily available. However in cases like Figure 4, a protocol needs to be used to inform the controlling instance (NMS or CP) about transceiver parameters. It is suggested to extend LMP for that purpose. The second step is to determine the feasibility of a lightpath between two transceivers without applying an optical signal. Understanding the limitations of the transceiver pair, a path through the optical network has to be found, whereby each path has an individual set of impairments deteriorating a wavelength traveling along that path. Since a single transceiver can support multiple parameter sets, the selection of a path may limit the permissible parameter sets determined in previous steps. The third step is then to setup the connection itself and to determine the Wavelength. This is done using the NMS of the optical transport network or by means of a control plane interaction such as signaling and includes the path information as well as the parameter set information necessary to enable communication. In a fourth step, optical monitoring is activated in the WDM network in order to monitor the status of the connection. The monitor functions of the optical interfaces at the terminals are also activated in order to monitor the end to end connection. Furthermore it should be possible to automate this step. After connecting the client device to the neighbor control plane-enabled transport node, a control adjacency may be automatically established, e.g. using LMP. 5.2. Link Monitoring Use Cases The use cases described below are assuming that power monitoring functions are available in the ingress and egress network element of the DWDM network, respectively. By performing link property correlation it would be beneficial to include the current transmit power value at reference point Ss and the current received power value at reference point Rs. For example if the Client transmitter power has a value of 0dBm and the ROADM interface measured power is -6dBm the fiber patch cord connecting the two nodes may be pinched or the connectors are dirty. As discussed before, the actual path or selection of a specific wavelength within the allowed set is outside the scope of LMP. The computing entities (e.g. the first optical node originating the circuit) can rely on GMPLS IGP (OSPF) to retrieve all the information related to the network, calculate the Kunze, et al. Expires December 13, 2018 [Page 16] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 path to reach the endpoint and signal the path implementation through the network via RSVP-TE. [ITU-T.G.698.2] defines a single channel optical interface for DWDM systems that allows interconnecting network-external optical transponders across a DWDM network. The optical transponders are external to the DWDM network. This so-called 'Black Link' approach illustrated in Fig. 5-1 of [ITU-T.G.698.2] and a copy of this figure is provided below in Figure 5. The single channel fiber link between the Ss/Rs reference points and the ingress/egress port of the network element on the domain boundary of the DWDM network (DWDM border NE) is called access link. Based on the definition in [ITU-T.G.698.2] it is part of the DWDM network. The access link is typically realized as a passive fiber link that has a specific optical attenuation (insertion loss). As the access link is an integral part of the DWDM network, it is desirable to monitor its attenuation. Therefore, it is useful to detect an increase of the access link attenuation, for example, when the access link fiber has been disconnected and reconnected (maintenance) and a bad patch panel connection (connector) resulted in a significantly higher access link attenuation (loss of signal in the extreme case of an open connector or a fiber cut). In the following section, two use cases are presented and discussed: 1) pure access link monitoring 2) access link monitoring with a power control loop These use cases require a power monitor as described in G.697 (see section 6.1.2), that is capable to measure the optical power of the incoming or outgoing single channel signal. The use case where a power control loop is in place could even be used to compensate an increased attenuation if the optical transmitter can still be operated within its output power range defined by its application code. Kunze, et al. Expires December 13, 2018 [Page 17] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 Use case 1: Access Link monitoring +--------------------------+ | P(in) = P(Tx) - a(Tx) | | ___ | +----------+ | \ / Power Monitor | | | P(Tx) | V P(in) | | +----+ | Ss //\\ | | |\ | | | TX |----|-----\\//------------------->| \ | | +----+ | Access Link (AL-T) | . | | | | | attenuation a(Tx) | . | |==============> | | | . | | | | External | | --->| / | | Optical | | |/ | |Transpond.| | P(out) | | | | ___ | | | | \ / Power Monitor | | | P(Rx) | V P(out) | | +----+ | Rs //\\ | | |\ | | | RX |<---|-----\\//--------------------| \ | | +----+ | Access Link (AL-R) | . | | | | | Attenuation a(Rx) | . | |<============== +----------+ | . | | | | <---| / | P(Rx) = P(out) - a(Rx) | |/ | | | | ROADM | +--------------------------+ - For AL-T monitoring: P(Tx) and a(Tx) must be known - For AL-R monitoring: P(RX) and a(Rx) must be known An alarm shall be raised if P(in) or P(Rx) drops below a configured threshold (t [dB]): - P(in) < P(Tx) - a(Tx) - t (Tx direction) - P(Rx) < P(out) - a(Rx) - t (Rx direction) - a(Tx) =| a(Rx) Alarms and events can be shared between Client and Network via LMP. Figure 5: Access Link Power Monitoring Kunze, et al. Expires December 13, 2018 [Page 18] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 5.2.1. Pure Access Link (AL) Monitoring Use Case Figure 6 illustrates the access link monitoring use case and the different physical properties involved that are defined below: - Ss, Rs: Single Channel reference points - P(Tx): current optical output power of transmitter Tx - a(Tx): access link attenuation in Tx direction (external transponder point of view) - P(in): measured current optical input power at the input port of border DWDM NE - t: user defined threshold (tolerance) - P(out): measured current optical output power at the output port of border DWDM NE - a(Rx): access link attenuation in Rx direction (external transponder point of view) - P(Rx): current optical input power of receiver Rx Description: - The access link attenuation in both directions (a(Tx), a(Rx)) is known or can be determined as part of the commissioning process. Typically, both values are very similar. - A threshold value t has been configured by the operator. This should also be done during commissioning. - A control plane protocol is in place that allows to periodically send the optical power values P(Tx) and P(Rx) to the control plane protocol instance on the DWDM border NE. This is illustrated in Figure 3. - The DWDM border NE is capable to periodically measure the optical power P(in) and P(out) as defined in G.697 by power monitoring points depicted as triangles in the figures below. Access Link monitoring process: - Tx direction: the measured optical input power P(in) is compared with the expected optical input power P(Tx) - a(Tx). If the measured optical input power P(in) drops below the value (P(Tx) - a(Tx) - t) a low power alarm shall be raised indicating that the access link attenuation has exceeded a(Tx) + t. - Rx direction: the measured optical input power P(Rx) is compared with the expected optical input power P(out) - a(Rx). If the measured optical input power P(Rx) drops below the value (P(out) - a(Rx) - t) a low power alarm shall be raised indicating that the access link attenuation has exceeded a(Rx) + t. - to avoid toggling errors, the low power alarm threshold shall be lower than the alarm clear threshold. Kunze, et al. Expires December 13, 2018 [Page 19] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 Use case 2: Access Link monitoring through LMP +----------+ +--------------------------+ | +------+ | P(Tx), P(Rx) | +-------+ | | | | | =================> | | | | | | LMP | | P(in), P(out) | | LMP | | | | Agent| | <================= | | Agent | | | +------+ | | +-------+ | | | | | | | | P(in) - P(Tx) - a(Tx) | | | | ___ | | | | \ / Power Monitor | | | P(Tx) | V | | +----+ | Ss //\\ | | |\ | | | TX |----|-----\\//------------------->| \ | | +----+ | Access Link (AL-T) | . | | | | | attenuation a(Tx) | . | |==============> | | | . | | | | External | | --->| / | | Optical | | |/ | |Transpond.| | P(out) | | | | ___ | | | | \ / Power Monitor | | | P(Rx) | V | | +----+ | Rs //\\ | | |\ | | | RX |<---|-----\\//--------------------| \ | | +----+ | Access Link (AL-R) | . | | | | | Attenuation a(Rx) | . | |<============== +----------+ | . | | | | <---| / | P(Rx) = P(out) - a(Rx) | |/ | | | | ROADM | +--------------------------+ - For AL-T monitoring: P(Tx) and a(Tx) must be known - For AL-R monitoring: P(RX) and a(Rx) must be known An alarm shall be raised if P(in) or P(Rx) drops below a configured threshold (t [dB]): - P(in) < P(Tx) - a(Tx) - t (Tx direction) - P(Rx) < P(out) - a(Rx) - t (Rx direction) - a(Tx) = a(Rx) Alarms and events can be shared between Client and Network via LMP according to [RFC4204] and [RFC4209] Kunze, et al. Expires December 13, 2018 [Page 20] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 Figure 6: Extended LMP Model 5.2.2. Power Control Loop Use Case This use case is based on the access link monitoring as described above. In addition, the border NE is running a power control application that is capable to control the optical output power of the single channel tributary signal at the output port of the border DWDM NE (towards the external receiver Rx) and the optical output power of the single channel tributary signal at the external transmitter Tx within their known operating range. The time scale of this control loop is typically relatively slow (e.g. some 10s or minutes) because the access link attenuation is not expected to vary much over time (the attenuation only changes when re-cabling occurs). From a data plane perspective, this use case does not require additional data plane extensions. It does only require a protocol extension in the control plane (e.g. this LMP draft) that allows the power control application residing in the DWDM border NE to modify the optical output power of the DWDM domain-external transmitter Tx within the range of the currently used application code. Figure 7 below illustrates this use case utilizing LMP with the extensions identified in this document. Kunze, et al. Expires December 13, 2018 [Page 21] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 Use case 3: Power Control Loop +----------+ +--------------------------+ | +------+ |P(Tx),P(Rx),Set(P(out))| +-------+ +--------+ | | | | | ====================> | | | | Power | | | | LMP | | P(in),P(out),Set(PTx) | | LMP | |Control | | | | | | <==================== | | | | Loop | | | +------+ | | +-------+ +--------+ | | | | | | | +------+ | | P(in) = P(Tx) - a(Tx) | | |C.Loop| | | ___ | | +------+ | | \ / Power Monitor | | | | P(Tx) | V | | +------+ | Ss //\\ | | |\ | | | TX |>----|-----\\//---------------------->| \ | | +------+ | Access Link (AL-T) | . | | | | VOA(Tx) | attenuation a(Tx) | . | |==============> | | | . | | | | External | | --->| / | | Optical | | |/ | |Transpond.| | P(out) | | | | ___ | | | | \ / Power Monitor | | | P(Rx) | V | | +----+ | Rs //\\ | | VOA(out) |\ | | | RX |<---|-----\\//---------------------<|-------| \ | | +----+ | Access Link (AL-R) | . | | | | | attenuation a(Rx) | . | |<======= +----------+ | VOA(out) | | | | <--<|-------| / | P(Rx) = P(out) - a(Rx) | |/ | | | | ROADM | +--------------------------+ Figure 7: Power control loop - The power control loop in transponders and ROADMs controls the Variable Optical Attenuators (VOA) to adjust the proper power in base of the ROADM and Receiver characteristics and the Access Link attenuation Kunze, et al. Expires December 13, 2018 [Page 22] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 6. Requirements Even if network architectures becomes more complex, management and operation as well as the provisioning process should have a higher degree of automation or should be fully automated. Simplifying and automating the entire management and provisioning process of the network in combination with a higher link utilization and faster restoration times will be the major requirements that have been addressed in this section. YANG based network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040] are strongly suggested as the base for the communication among EMS, Controller and the Data Plane. Data plane interoperability as defined for example in [ITU-T.G.698.2] is a precondition to take full benefit from standardized interfaces between network and control/management plane. The following requirements are focusing on the usage of DWDM interfaces. Kunze, et al. Expires December 13, 2018 [Page 23] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 1 A procedure to setup an optical connection MUST be defined and implemented in DWDM and client devices (containing the single channel optical interface). The Procedure MAY me defined in a dedicated draft as proposed in Appendix. 2 In order to ensure a lean management and provisioning of single channel interfaces, the management and control plane of both the client and DWDM network MUST be aware of the right set of parameters. Such parameters define the interfaces and the optical network and are needed to properly setup the optical connection. 3 A standard-based northbound API (to network management system) based on NETCONF/RESTCONF SHOULD be supported, alternatively SNMP MAY be supported too. 4 A standard-based data model for single channel interfaces MUST be supported to exchange optical parameters with control/management plane. 5 NETCONF SHOULD be used also for configuration of the single channel interfaces including the power setting 6 LMP SHOULD be extended and used in cases where optical parameters need to be exchanged between two nodes to correlate link characteristics and adopt the working mode of the single channel interface. The LMP extension MAY be defined in a draft as reported in Appendix. 7 LMP MAY be used to adjust the output power of the single channel DWDM interface to ensure that the interface works in the right range. 8 RSVP-TE SHOULD be used to exchange some relevant parameters between the client and the optical node (e.g. the label value), without preventing the network to remain in charge of the optical path computation 9 Power monitoring functions at both ends of the DWDM connection MAY be used to further automate the setup and shutdown process of the optical interfaces. 10 In fault cases, the network SHOULD be able to recover wavelengths, either using pre-defined paths or dynamic re-routing. 11 LMP MAY be used to monitor and observe the access link. Kunze, et al. Expires December 13, 2018 [Page 24] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 7. Acknowledgements The authors would like to thank all who supported the work with fruitful discussions and contributions. 8. IANA Considerations This memo includes no request to IANA. 9. Security Considerations The architecture and solution space in scope of this framework imposes no additional requirements to the security models already defined in RFC5920 for packet/optical networks using GMPLS, covering also Control Plane and Management interfaces. Respective security mechanisms of the components and protocols, e.g. LMP security models, can be applied unchanged. As this framework is focusing on the single operator use case, the security concerns can be relaxed to a subset compared to a setup where information is exchanged between external parties and over external interfaces. Concerning the access control to Management interfaces, security issues can be generally addressed by authentication techniques providing origin verification, integrity and confidentiality. Additionally, access to Management interfaces can be physically or logically isolated, by configuring them to be only accessible out-of- band, through a system that is physically or logically separated from the rest of the network infrastructure. In case where management interfaces are accessible in-band at the client device or within the optical transport network domain, filtering or firewalling techniques can be used to restrict unauthorized in-band traffic. Authentication techniques may be additionally used in all cases. 10. Contributors Kunze, et al. Expires December 13, 2018 [Page 25] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 Arnold Mattheus Deutsche Telekom Darmstadt Germany email arnold.Mattheus@telekom.de Manuel Paul Deutsche Telekom Berlin Germany email Manuel.Paul@telekom.de Josef Roese Deutsche Telekom Darmstadt Germany email j.roese@telekom.de Frank Luennemann Deutsche Telekom Muenster Germany email Frank.Luennemann@telekom.de Dharini Hiremagalur Juniper 1133 Innovation Way Sunnyvale - 94089 California USA dharinih@juniper.net 11. References 11.1. Normative References [ITU-T.G.694.1] International Telecommunications Union, "Spectral grids for WDM applications: DWDM frequency grid", ITU-T Recommendation G.694.1, Febriary 2012. [ITU-T.G.698.2] International Telecommunications Union, "Amplified multichannel dense wavelength division multiplexing applications with single channel optical interfaces", ITU-T Recommendation G.698.2, November 2009. Kunze, et al. Expires December 13, 2018 [Page 26] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 [ITU-T.G.805] International Telecommunications Union, "Spectral grids for WDM applications: DWDM frequency grid", ITU-T Recommendation G.805, March 2000. [ITU-T.G.872] International Telecommunications Union, "Architecture of optical transport networks", ITU-T Recommendation G.872, November 2001. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3591] Lam, H-K., Stewart, M., and A. Huynh, "Definitions of Managed Objects for the Optical Interface Type", RFC 3591, DOI 10.17487/RFC3591, September 2003, . [RFC4204] Lang, J., Ed., "Link Management Protocol (LMP)", RFC 4204, DOI 10.17487/RFC4204, October 2005, . [RFC4208] Swallow, G., Drake, J., Ishimatsu, H., and Y. Rekhter, "Generalized Multiprotocol Label Switching (GMPLS) User- Network Interface (UNI): Resource ReserVation Protocol- Traffic Engineering (RSVP-TE) Support for the Overlay Model", RFC 4208, DOI 10.17487/RFC4208, October 2005, . [RFC4209] Fredette, A., Ed. and J. Lang, Ed., "Link Management Protocol (LMP) for Dense Wavelength Division Multiplexing (DWDM) Optical Line Systems", RFC 4209, DOI 10.17487/RFC4209, October 2005, . [RFC7689] Bernstein, G., Ed., Xu, S., Lee, Y., Ed., Martinelli, G., and H. Harai, "Signaling Extensions for Wavelength Switched Optical Networks", RFC 7689, DOI 10.17487/RFC7689, November 2015, . Kunze, et al. Expires December 13, 2018 [Page 27] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 [RFC7792] Zhang, F., Zhang, X., Farrel, A., Gonzalez de Dios, O., and D. Ceccarelli, "RSVP-TE Signaling Extensions in Support of Flexi-Grid Dense Wavelength Division Multiplexing (DWDM) Networks", RFC 7792, DOI 10.17487/RFC7792, March 2016, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . 11.2. Informative References [ITU-T.G.691] ITU-T, "Optical interfaces for single channel STM-64 and other SDH systems with optical amplifiers", ITU-T Recommendation ITU-T G.691, 2008. [ITU-T.G.693] ITU-T, "Optical interfaces for intra-office systems", ITU-T Recommendation ITU-T G.693, 2009. [ITU-T.G.8081] ITU-T, "Terms and definitions for Automatically Switched Optical Networks (ASON)", ITU-T Recommendation G.8081", ITU-T Recommendation ITU-T G.8081, September 2010. [ITU-T.G.957] ITU-T, "Optical interfaces for equipments and systems relating to the synchronous digital hierarchy", ITU-T Recommendation ITU-T G.957, 2006. [Network-Assigned-Upstream-Label] Internet Engineering Task Force, "Generalized Multi- Protocol Label Switching (GMPLS) Resource reSerVation Protocol with Traffic Engineering (RSVP- TE) mechanism that enables the network to assign an upstream label for a bidirectional LSP", draft-ietf-teas-network-assigned- upstream-label draft-ietf-teas-network-assigned-upstream- label, June 2017. [RFC5146] Kumaki, K., Ed., "Interworking Requirements to Support Operation of MPLS-TE over GMPLS Networks", RFC 5146, DOI 10.17487/RFC5146, March 2008, . Kunze, et al. Expires December 13, 2018 [Page 28] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 Appendix A. Appendix In this section are reported some examples and references on the MIB, Yang and LMP usage. The MIB and TLV defining the parameters described above are reported in the drafts below and are intended as informative data: draft-dharinigert-ccamp-dwdm-if-lmp Extension to the Link Management Protocol (LMP/DWDM -rfc4209) for Dense Wavelength Division Multiplexing (DWDM) Optical Line Systems to manage the application code of optical interface parameters in DWDM application draft-ggalimbe-ccamp-flex-if-lmp Extension to the Link Management Protocol (LMP/DWDM -rfc4209) for Dense Wavelength Division Multiplexing (DWDM) Optical Line Systems to manage the application code of optical interface parameters in DWDM application draft-dharini-ccamp-dwdm-if-param-yang A YANG model to manage the optical interface parameters for an external transponder in a WDM network draft-ietf-ccamp-flexigrid-yang YANG data model for Flexi-Grid Optical Networks draft-galimbe-ccamp-iv-yang A YANG model to manage the optical parameters for in a WDM network NOTE: the above information is defined at the time of publication of this document and thus subject to change. Authors' Addresses Ruediger Kunze (editor) Deutsche Telekom Winterfeldtstr. 21-27 10781 Berlin Germany Phone: +491702275321 Email: RKunze@telekom.de Kunze, et al. Expires December 13, 2018 [Page 29] Internet-Draft draft-ietf-ccamp-dwdm-if-mng-ctrl-fwk-11 June 2018 Gert Grammel (editor) Juniper Oskar-Schlemmer Str. 15 80807 Muenchen Germany Phone: +49 1725186386 Email: ggrammel@juniper.net Dieter Beller Nokia Lorenzstrasse, 10 70435 Stuttgart Germany Phone: +4971182143125 Email: Dieter.Beller@nokia.com Gabriele Galimberti (editor) Cisco Via S. Maria Molgora, 48c 20871 - Vimercate Italy Phone: +390392091462 Email: ggalimbe@cisco.com Julien Meuric Orange 2, Avenue Pierre Marzin 22307 Lannion Cedex France Phone: +33 Email: julien.meuric@orange.com Kunze, et al. Expires December 13, 2018 [Page 30]