TVR L. M. Contreras Internet-Draft Telefonica Intended status: Informational 5 July 2025 Expires: 6 January 2026 Using off-path mechanisms for exposing Time-Variant Routing information draft-ietf-tvr-alto-exposure-02 Abstract Time-Variant Routing (TVR) involves predictable, scheduled changes to network topology elements such as nodes, links, and adjacencies that impact routing behavior over time. All those changes can alter the connectivity in the network in a predictable manner, which is known as Time-Variant Routing (TVR). This document proposes mechanisms for exposing TVR information to both internal and external applications, focusing on off-path solutions that decouple the advertisement of scheduled changes from the routing control plane signaling. 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 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 6 January 2026. Copyright Notice Copyright (c) 2025 IETF Trust and the persons identified as the document authors. All rights reserved. Contreras Expires 6 January 2026 [Page 1] Internet-Draft ALTO for TVR July 2025 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 Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. On-path vs Off-path Mechanisms for TVR . . . . . . . . . . . 4 2.1. On-path Mechanisms . . . . . . . . . . . . . . . . . . . 4 2.2. Off-path Mechanisms . . . . . . . . . . . . . . . . . . . 4 2.3. Hybrid Approaches . . . . . . . . . . . . . . . . . . . . 5 3. Ways of retrieving scheduled topological changes . . . . . . 5 3.1. Interaction with a network controller . . . . . . . . . . 5 3.2. Interaction with routing protocols augmented to support TVR advertisements . . . . . . . . . . . . . . . . . . . . . 6 3.3. Applicability . . . . . . . . . . . . . . . . . . . . . . 6 4. Mechanisms for Exposing TVR Information . . . . . . . . . . . 7 4.1. ALTO Protocol . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Other Off-path Mechanisms . . . . . . . . . . . . . . . . 9 5. Security and operational considerations . . . . . . . . . . . 9 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 6.1. Normative References . . . . . . . . . . . . . . . . . . 9 6.2. Informative References . . . . . . . . . . . . . . . . . 10 Appendix A. Assessment of ALTO as off-path solution against TVR requirements . . . . . . . . . . . . . . . . . . . . . . 11 Appendix B. Assessment of archietcture proposed in I-D.wqb-tvr-applicability . . . . . . . . . . . . . . . . 13 Appendix C. Implementation status . . . . . . . . . . . . . . . 14 Appendix D. Identified gaps on TVR specifications . . . . . . . 15 Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . 16 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 16 1. Introduction Time-Variant Routing (TVR) refers to operational scenarios where network topology, including nodes, links, and adjacency attributes, changes in a predictable, scheduled manner. There can be operational situations (e.g., maintenance windows, load balancing, energy-saving policies, or network upgrades) where changes in the network, such as modifications in either nodes, links or adjacencies, can introduce variations on the routing of that network. Use cases representative of such operational situations are Contreras Expires 6 January 2026 [Page 2] Internet-Draft ALTO for TVR July 2025 documented in [RFC9657]. Those predictable changes can be scheduled either from a higher-level system (e.g., OSS) or from a Network Controller. Figure 1 sketches a potential architecture facilitating the exposure of changes introduced by TVR operation. There can be multiple variants of such architecture. Network (programming (impact Operator ---------+ of scheduled estimation | TVR changes) of scheduled V TVR changes) +-------------+ +--------------+ | Network | | Network | | Controller |<----->| Digital Twin | +-------------+ +--------------+ A | (feeding impacts | | (activation of scheduled +------+ +------+ of scheduled TVR changes) | | TVR changes) | | V V +-------------+ ,------._ |Off-path Info| ,-' `-. | Component | / \ +-------------+ ( Network ) A \ / | `-. ,-' (exposure | `+------' of scheduled | ^ TVR changes) | : | (awareness : | of scheduled v | TVR changes) +-------------+ +------------->| Application | +-------------+ Figure 1. Potential architecture using a dedicated Off-path Information Component for advertising TVR scheduled changes Since the expected changes can be predicted beforehand, then it is possible to anticipate the impacts of that changes in the routing of the network. , for instance by means of algorithms embedded in the Network Controller allowing to recalculate the resulting routing metrics, or through experimental observations e.g. in network digital twins [I-D.irtf-nmrg-network-digital-twin-arch]. Being feasible then to automatize the changes and to pre-calculate the impacts that those changes can introduce into the routing of the network, it is possible to expose in advance such changes in a way Contreras Expires 6 January 2026 [Page 3] Internet-Draft ALTO for TVR July 2025 that applications (both internal and external) can become aware of those routing variations along time, allowing proactive service management and optimization ahead of the activation of those changes. This document builds on TVR-related foundational work [RFC9657], [I-D.ietf-tvr-requirements] and [I-D.ietf-tvr-schedule-yang], but focussing on off-path exposure of TVR information, describing architectural considerations and mechanisms to present scheduled network changes to applications. 2. On-path vs Off-path Mechanisms for TVR At the time of advertising and consuming TVR scheduled changes, two different mechanisms can be considered, namely on-path and off-path mechanisms. 2.1. On-path Mechanisms On-path mechanisms disseminate scheduled topological changes directly through routing protocols such as OSPF, IS-IS, or BGP, augmented to carry time-scheduled advertisements [I-D.ietf-tvr-schedule-yang]. This approach embeds TVR information on the routing data plane. One of the primary benefits of disseminating scheduled topological changes by routing protocols is the potential for timely, distributed updates. This tight coupling enables rapid propagation of scheduled changes across the network. However, this approach also introduces several challenges: * Cascading Updates: a single scheduled change (e.g., link metric adjustment or path re-optimization) may trigger a series of subsequent updates across the network. These cascading effects can lead to excess of processing in the network elements if not properly managed. * Coordination and Conflict Resolution: in a distributed environment, multiple nodes may attempt to adjust routes or metrics concurrently. This increases the complexity of coordination and requires robust mechanisms to detect and resolve conflicts without introducing inconsistencies or loops. 2.2. Off-path Mechanisms Off-path mechanisms expose TVR information via centralized or logically separate systems outside the routing protocol control plane, using specific protocols, data models or APIs for that purpose. Contreras Expires 6 January 2026 [Page 4] Internet-Draft ALTO for TVR July 2025 It can be advantageous for different reasons: * Simplified conflict detection and resolution due to centralized control. * Controlled and potentially filtered exposure of information to external or internal applications. * Reduced impact on routing protocols and network stability. Off-path solutions can ingest data from multiple sources, including controllers and augmented routing protocols, and provide aggregated, application-friendly views of scheduled network changes. 2.3. Hybrid Approaches Hybrid approaches may combine on-path and off-path methods, e.g., using routing protocol advertisements for internal synchronization and off-path systems for external exposure. 3. Ways of retrieving scheduled topological changes According to the two strategies commented in the Introduction, it can be considered two different ways in which off-path solutions retrieve the information about scheduled topological changes. In one case, the changes can be notified directly by a network controller, while in the second case the changes are collected from advertisements in augmented routing protocols. In both cases, the data model for representing the scheduled changes can be the same, describing the changing topological events in a similar way. A data model for representing TVR information is proposed in [I-D.ietf-tvr-schedule-yang], which can be used in any of the options describe next. 3.1. Interaction with a network controller The architecture in Figure 1 assumes the intervention of a Network Controller in order to schedule and activate the changes in the network in a predictable manner. The network controller can pass the information about the planned changes to a separate component dedicated to advertise the TVR changes off-path, or it could even incorporate such capability as part of the functional capabilities of the controller. Thus, depending on the capabilities of the controller, it may either provide raw scheduled changes or precomputed future topologies reflecting those changes. Contreras Expires 6 January 2026 [Page 5] Internet-Draft ALTO for TVR July 2025 3.2. Interaction with routing protocols augmented to support TVR advertisements As an alternative solution, it could be the case that existing routing protocols become augmented in order to natively support the advertisement of network changes along the time (for instance, an example of schedules for OSPF costs is provided in [I-D.ietf-tvr-schedule-yang]). If that is the case, the off-path solution can participate of the signaling of the network routing information by listening to IGPs and/or peering with BGP speakers, as described in [RFC7971]. This enables the off-path system to build time-aware topological views based on routing advertisements. 3.3. Applicability Uniform representation of scheduled changes facilitates ingestion and processing. The YANG data model draft [I-D.ietf-tvr-schedule-yang] provides a framework to represent schedules for nodes, interfaces, and attributes, including timing, periodicity, and availability. For instance, an engineer in the Network Operation Center (NOC) represented in Figure 1 can program some changes in the network in a planned, anticipated way so that the impacts of such changes can be estimated in advance. For instance, the engineer can enter the following data, according to [I-D.ietf-tvr-schedule-yang]: Contreras Expires 6 January 2026 [Page 6] Internet-Draft ALTO for TVR July 2025 module: ietf-tvr-node +--rw node-schedule +--rw node-id? "192.168.10.17" ... +--rw interface-schedule +--rw interfaces* +--rw name "GigabitEthernet0" ... +--rw attribute-schedule +--rw schedules* +--rw schedule-id "0123456789" +--rw (schedule-type)? +--:(period) ... +--rw period-start "2024-07-08T10:30:00" +--rw time-zone-identifier? "Africa/Dakar" +--rw (period-type)? ... +--:(duration) +--rw duration? "3600" ... +--rw attr-value +--rw available? "false" This order represents the action of tearing down interface GigabitEthernet0 of the node with loopback IP address 192.168.10.17 for one hour, at 10:30 local time of Dakar, due for instance to a maintenance action in the network. With this information, the network systems can analyse the impact of such action (the way in which that impacts are evaluated are out of scope of this document). According to the estimated impacts, the engineer can decide to continue or to replan the action. 4. Mechanisms for Exposing TVR Information Exposing TVR information requires mechanisms able to represent time- varying network states, including topology and associated metrics, with appropriate granularity and temporal precision. 4.1. ALTO Protocol The Application-Layer Traffic Optimization (ALTO) protocol [RFC7285] has been designed to expose network topological and cost information to applications. In consequence, ALTO can an act as an off-path mechanism for the purpose of exposing the impacts due to changes in the routing of a network. In that case, the Off-path Information Component in Figure 1 is realized by means of an ALTO Server. Contreras Expires 6 January 2026 [Page 7] Internet-Draft ALTO for TVR July 2025 ALTO [RFC7285] provides topological-related information in the form of both network and cost maps. The network map basically summarizes the IP address ranges aggregated in each Provider-defined Identifier (PID). Such IP addresses define either customers or service functions attached to each network node. The cost map details the topological relationship among PIDs in terms of a certain metric. The basic metric provided is the routing cost among PIDs, but other metrics can be also provided such as performance-related metrics [RFC9439]. For the purpose of exposing future changes on the reachability between PIDs in the network, ALTO defines in [RFC8896] a calendared cost map (named ALTO cost calendar) which allows to signal future changes on the cost metric. Thus, for a metric related to routing, the cost calendar can expose scheduled modifications in the connectivity between PIDs in a natural manner. The ALTO cost calendar presents the information (i.e., metrics between PIDs) in the form of JSON arrays, where each listed value corresponds to a certain time interval. The ALTO cost calendar also includes attributes to describe the time scope of the calendar. The calendar provided by ALTO has the following attributes defined in [RFC8896]: * "Calendar-start-time", which indicates the date at which the first value of the calendar applies. * "Time-interval-size", that defines the duration of an ALTO Calendar time interval in a unit of seconds. * "Number-of-intervals", that indicates the number of values of the cost calendar array. * "Repeated", which is an optional attribute that indicates how many iterations of the calendar value array have the same values. In order to know about cheduled changes, two possibles strategies can be in placed. One strategy is to relay on centralized network control elements populating scheduled changes to the ALTO server sufficiently in advance as to calculate and expose the intended changes before them are effectively activated in the network by the controllers. That is, the introduction of changes is governed by the network controller configuring dynamically the network elements (i.e., nodes, links) following a planned set of actions. Such planned actions are the ones fed to ALTO so that ALTO can create and expose updated topological views for the scheduled modifications. Contreras Expires 6 January 2026 [Page 8] Internet-Draft ALTO for TVR July 2025 A second strategy is to disseminate the scheduled changes by means of the routing protocols in the network, so that the routing protocols distribute the planned topological changes at link or node level. It is worthy to note that a change distributed in this manner just by a single node can motivate a cascade of some other scheduled changes in different other nodes, thus representing potential stability issues that should be addressed with care. Anyway, in certain environments it can be suitable for signaling scheduled changes so that can serve as basis for deriving from it the topological views to be exposed by ALTO. 4.2. Other Off-path Mechanisms While ALTO is a mature example, other off-path mechanisms may include custom APIs exposing scheduled network data. Such APIs could be supported by; * Network Controllers, in case such controller is able to compute and maintain the changes. * Managing device, in charge of generating and maintaining the schedules, or Schedule Database as defined in [I-D.zdm-tvr-applicability]. 5. Security and operational considerations Same security and operational considerations as described in [RFC8896] apply also in this document. Apart from that, [I-D.ietf-tvr-requirements] describes relevant security considerations for TVR solutions. The off-path approach prevents some of those security issues, as the ones requiring direct access to the source of information in risk, like the time synchronization signals. However, some other threats are of applicability, like the ones referring to the access to the information, activity identification and privacy. In order to mitigate such security risks, the off-path solution should implement the necessary mechanisms for authentication, secure data transfer and privacy preservation. 6. References 6.1. Normative References Contreras Expires 6 January 2026 [Page 9] Internet-Draft ALTO for TVR July 2025 [RFC7285] Alimi, R., Ed., Penno, R., Ed., Yang, Y., Ed., Kiesel, S., Previdi, S., Roome, W., Shalunov, S., and R. Woundy, "Application-Layer Traffic Optimization (ALTO) Protocol", RFC 7285, DOI 10.17487/RFC7285, September 2014, . 6.2. Informative References [I-D.ietf-tvr-requirements] King, D., Contreras, L. M., Sipos, B., and L. Zhang, "TVR (Time-Variant Routing) Requirements", Work in Progress, Internet-Draft, draft-ietf-tvr-requirements-05, 3 March 2025, . [I-D.ietf-tvr-schedule-yang] Qu, Y., Lindem, A., Kinzie, E., Fedyk, D., and M. Blanchet, "YANG Data Model for Scheduled Attributes", Work in Progress, Internet-Draft, draft-ietf-tvr-schedule-yang- 04, 22 April 2025, . [I-D.irtf-nmrg-network-digital-twin-arch] Zhou, C., Yang, H., Duan, X., Lopez, D., Pastor, A., Wu, Q., Boucadair, M., and C. Jacquenet, "Network Digital Twin: Concepts and Reference Architecture", Work in Progress, Internet-Draft, draft-irtf-nmrg-network-digital- twin-arch-10, 28 February 2025, . [I-D.wqb-tvr-applicability] Zhang, L., Ma, Q., Wu, Q., and M. Boucadair, "Applicability of YANG Data Models for Scheduling of Network Resources", Work in Progress, Internet-Draft, draft-wqb-tvr-applicability-00, 10 September 2024, . [I-D.zdm-tvr-applicability] Zhang, L., Dong, J., and M. Boucadair, "Applicability of TVR YANG Data Models", Work in Progress, Internet-Draft, draft-zdm-tvr-applicability-02, 28 February 2025, . [OPTIMAIX_repo] "OPTIMAIX repository (https://github.com/OPTIMAIX)", n.d.. Contreras Expires 6 January 2026 [Page 10] Internet-Draft ALTO for TVR July 2025 [OPTIMAIX_video] "Network Operation Demonstration (https://www.youtube.com/channel/UC4_sduilyier-cA3-Xpir- A)", December 2024. [RFC7971] Stiemerling, M., Kiesel, S., Scharf, M., Seidel, H., and S. Previdi, "Application-Layer Traffic Optimization (ALTO) Deployment Considerations", RFC 7971, DOI 10.17487/RFC7971, October 2016, . [RFC8896] Randriamasy, S., Yang, R., Wu, Q., Deng, L., and N. Schwan, "Application-Layer Traffic Optimization (ALTO) Cost Calendar", RFC 8896, DOI 10.17487/RFC8896, November 2020, . [RFC9439] Wu, Q., Yang, Y., Lee, Y., Dhody, D., Randriamasy, S., and L. Contreras, "Application-Layer Traffic Optimization (ALTO) Performance Cost Metrics", RFC 9439, DOI 10.17487/RFC9439, August 2023, . [RFC9657] Birrane, III, E., Kuhn, N., Qu, Y., Taylor, R., and L. Zhang, "Time-Variant Routing (TVR) Use Cases", RFC 9657, DOI 10.17487/RFC9657, October 2024, . Appendix A. Assessment of ALTO as off-path solution against TVR requirements (Note: to be updated with [I-D.ietf-tvr-requirements] version -05 or higher) The Time Variant Routing requirements are being documented in [I-D.ietf-tvr-requirements]. Despite that is yet a work in progress, it is convenient to start an assessment of the off-path solution provided by ALTO against the requirements expected to be supported by any TVR-capable solution. The following Table summarizes the assessment exercise. The requirements are listed including the section (in brackets) of [I-D.ietf-tvr-requirements] where they are defined. Contreras Expires 6 January 2026 [Page 11] Internet-Draft ALTO for TVR July 2025 +===============================+===============================+ | Requirement | Compliance | +===============================+===============================+ | (3.1) Resource scheduling | Feasible to reflect scheduled | | | changes in a topology by means| | | of a sequence of network and | | | cost maps along the time | +-------------------------------+-------------------------------+ | (3.2.1) Scope of Time- | Combines both time-invariant | | Variability | and time-variant entities. | | | Allows representation of | | | global and individual changes | +-------------------------------+-------------------------------+ | (3.2.2) Time Horizon | Specified by means of | | | "time-interval-size" attribute| | | expressed in seconds | +-------------------------------+-------------------------------+ | (3.2.3) Time Precision | Determined in units of seconds| +-------------------------------+-------------------------------+ | (3.2.4) Validity in a Schedule| Permits to accommodate | | | multiple subsequent schedules | +-------------------------------+-------------------------------+ | (3.2.5) Periodicity in a | Repetitive states specified | | Schedule | by means of the attribute | | | "repeated" | +-------------------------------+-------------------------------+ | (3.2.6) Continuity in a | Governed by the | | Schedule | "time-interval-size" attribute| | | expressed in seconds | +-------------------------------+-------------------------------+ | (3.2.7) Time-Overlap and | Not supported. It would | | Priority | require extension of RFC8896 | +-------------------------------+-------------------------------+ | (3.2.8) Property Value | Zero-order hold mode. Other | | Interpolation | modes could be potentially | | | supported | +-------------------------------+-------------------------------+ | (3.2.9) Changes to Model | Support of fine-grained | | State | changes | +-------------------------------+-------------------------------+ | (3.3) Topologies | Schedules applicable to nodes | | | and links. Support of | | | potential future node or link | | | connectivity | +-------------------------------+-------------------------------+ | (3.4) Routing | Allows computation of | | | TVR-enabled paths. Reported | | | constrains can be considered | Contreras Expires 6 January 2026 [Page 12] Internet-Draft ALTO for TVR July 2025 +-------------------------------+-------------------------------+ Appendix B. Assessment of archietcture proposed in [I-D.wqb-tvr-applicability] (Note: to reconsider this section since [I-D.wqb-tvr-applicability] already expired, and new version of the document in [I-D.zdm-tvr-applicability] does not consider the same architecture) [I-D.wqb-tvr-applicability] introduces an architecture for the control scheduling of network resources, with two functional components, namely the Scheduled Service Requester, in charge of soliciting a resource schedule change, and the Scheduled Service Responder, in charge of handling the scheduling orders. Such architecture assumes the existence of funcitonal interfaces between both comoponents. Comparing such architecture with the one depicted in Figure 1, the following mapping is possible, as represented in Figure 2. Contreras Expires 6 January 2026 [Page 13] Internet-Draft ALTO for TVR July 2025 Network Operator (programming (impact [ScheduleRequester]-----+ of scheduled estimation | TVR changes) of scheduled ....................... V ............... TVR changes) ... : [Schedule +-------------+ +--------------+ : : Service | Network | | Network | : : Responder] | Controller |<----->| Digital Twin | : : +-------------+ +--------------+ : : A ... | .............................: : (feeding impacts | : | (activation : of scheduled +------+ : +------+ of scheduled : TVR changes) | : | TVR changes) : | : | : V : V : +-------------+ : ,------._ : |Off-path Info| : ,-' `-. : | Component | : / \ : +-------------+ : ( Network ) : A : \ / :............. | .......: `-. ,-' (exposure | `+------' of scheduled | ^ TVR changes) | : | (awareness : | of scheduled v | TVR changes) +-------------+ +------------->| Application | +-------------+ [Schedule Consumer] Figure 2. Schedule Requester, Responder and Consumer in the off-path solution From this assessment, it can be concluded that the roles of Schedule Requester and Schedule Responder have its correspondance in the off- path solution here described. However, the intended architecture in [I-D.wqb-tvr-applicability] lacks of the role of Schedule Consumer here described (or at least assumes that the Requester will be also the Consumer, which cannot be necessarily the case). Appendix C. Implementation status The scenario proposed in Figure 1 has been implemented for the validation of the off-path TVR approach using ALTO as off-path mechanism. The use case to exercise the off-path solution considers operational tasks in the network such as hardware and/or software maintenance and upgrades. Such actions imply temporal topological changes that can be anticipated since they are planned interventions Contreras Expires 6 January 2026 [Page 14] Internet-Draft ALTO for TVR July 2025 in teh network. By leveraging on TVR, applications consuming the network can be timnely informed of those changes in advanced, permitting re-configurations and re-optimizations on the application side minimizing negative impacts due to the foreseen changes. A video demonstrating the scenario can be found in [OPTIMAIX_video]. The modules implementing the functionality have been released as open source and are available at [OPTIMAIX_repo]. * Network Operation Center (NOC), developed by E-lighthouse. This component is represented as the "Network Operator" in Figure 1. It is in charge of requesting scheduled changes in the network. * Net2plan_NDT, developed by E-lighthouse. This component is part of the "Network Digital Twin" module in Figure 1. It is in charge of performing advanced network simulations and reporting Key Performance Indicator (KPI) evaluation consequence of the topological changes. * Change_Scheduler, devoloped by Telefónica. This component is part of the "Network Controller" module in Figure 1. It is in charge of receiving the topological changes requests, including the intended execution time for the scheduled changes. It passess / receive topological information and KPIs to / from Net2plan_NDT. It is also in charge of triggering the execution of the network chages at due time. * ALTO_CostCalendar, developed by Telefónica. This component is part of the "ALTO Server" module in Figure 1. It is in charge of processing the predicted KPIs on the topology with the proposed changes, and exposing those changes to external applications as an example of off-path mechanism. Appendix D. Identified gaps on TVR specifications The work carried out for implementing the architecture in Figure 1 reveals some gaps. * [I-D.ietf-tvr-schedule-yang] only provides granularity for schedule changes at node and link level. However, operational scenarios as the one described here can require further granularity, as cards. A current workaround could be to count all the interfaces of the same card, which can be onerous in some cases (e.g., cards of 48 GigaEthernet ports). * Advertisements of scheduled changes in distributed manner (that is, on-path, directly using augmented routing protocols) can raise conflicts. While conflicts are easy to be handled by centralized Contreras Expires 6 January 2026 [Page 15] Internet-Draft ALTO for TVR July 2025 (i.e., off-path) solutions, it can require the definition of arbitration mechanisms for the case of distributed (i.e., on-path) ones. * When distributed advertisements are in place, there are no means defined for reverting planned changes other than reconfiguring and launch new advertisements. Centralized approach simplifies the evaluation of impacts, and then, facilitates the indetification of potential problems that a planned change can cause. Distributed means of distributed scheduled changes can require ways of easily reverting proposed changes. * When using distributed advertisement, the exposure of planned changes to external parties or applications can be a security problem, because the potential accessibility to internal information beyond the topological changes. Secure ways of accessing to that information can be needed to allow such use cases. Acknowledgements This work has been partially funded by the Spanish Ministry of Economic Affairs and Digital Transformation and the European Union - NextGenerationEU under projects OPTIMAIX_OaaS (Ref. TSI- 063000-2021-34) and OPTIMAIX_NDT (Ref. TSI-063000-2021-35). Author's Address Luis M. Contreras Telefonica Ronda de la Comunicacion, s/n 28050 Madrid Spain Email: luismiguel.contrerasmurillo@telefonica.com URI: http://lmcontreras.com Contreras Expires 6 January 2026 [Page 16]