GREEN X. Chen Internet-Draft CMCC Intended status: Standards Track J. Zhou Expires: 7 January 2027 ZTE 6 July 2026 Coordinated Energy Saving between RAN and Transport Network draft-chen-green-ran-transport-coord-energy-saving-00 Abstract This document provides an coordinated energy saving mechanism between RAN and transport 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 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 7 January 2027. Copyright Notice Copyright (c) 2026 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 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. Chen & Zhou Expires 7 January 2027 [Page 1] Internet-Draft coordinated-energy-saving-between-ran-an July 2026 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Coordination . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Extension . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Informative References . . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction This document addresses the usecases of RAN and transport network identified in [I-D.ietf-green-use-cases] through an coordinated energy saving mechanism. As described in Section 2.7 of [I-D.ietf-green-use-cases], radio base stations are typically connected to the backbone network by means of fiber technologies. The capability of radio link can be adjusted accordingly to the traffic observed. Some of the power-related parameters are dynamically configured to adjust the power to the observed traffic levels with some coarse granularity to avoid the underutilized of energy. In addition, as described in [I-D.chen-green-transport-energy-saving] describes the energy saving in transport network. However, under current energy-saving methods, energy saving of RAN and TN are done separately and without coordination. This leads to RAN adjusting its wireless link according to its own traffic conditions, but the transport network is unaware of this and still reserves resources based on the maximum traffic, especially the internal forwarding resources, optical module resources, and TDM slot resources, resulting in resource waste. Therefore, it is necessary to study an energy-saving coordination mechanism between the RAN and the transport network. 2. Coordination This section describes the detailed coordination mechanisms that may exist between the Radio Access Network (RAN) and the Transport Network (TN). Chen & Zhou Expires 7 January 2027 [Page 2] Internet-Draft coordinated-energy-saving-between-ran-an July 2026 +--------------------------------------------------------------------------------+ | | | +------------------+ | | | RAN Controller <----------------------------------------------------+ | +--------+---------+ | | | | | | | +------------+------------+------------+------------+------------+ | | | | | | | | | | | | +---+---+ +---+---+ +---+---+ +---+---+ +---+---+ +---+---+ | | | | RAN1 | | RAN2 | | RAN3 | | RAN4 | | RAN5 | | RAN6 | | | | +---^---+ +---^---+ +---^---+ +---^---+ +---^---+ +---^---+ | | | | | | | | | | | | | | | | | | | | +------+------------+------------+------------+------------+------------+--------+ | | | | | | | | +--------------------------------------------------------------------------------+ | | | | | | | | | | | | +----v----+ | | +----v----+ | | | | +-------> Access <-------+ +-------> Access <-------+ | | | | Node 1 | | Node 2 | | | | +----+----+ +----+----+ | | | | | | | | | | | | | +-----------------+--------------------+ | | | | | | | | | | +--------+-------+ | | | | | | Aggregation | | | | | | | Node | | | | | | +--------+-------+ | | | | | | | | | | +-----------------+--------------------+ | | | | | | | +----------+-------+ | | | | TN Controller <-------------------------------------------------+ | +------------------+ | | | +--------------------------------------------------------------------------------+ Figure 1: Energy Saving Coordination between RAN and Transport Network As show in Figure 1, the upper part represents the Radio Access Network(RAN), which consists of six RAN access nodes, labeled RAN1 through RAN6. These nodes provide radio coverage and user-plane termination for mobile terminals. All six RAN nodes are under the control of a single RAN controller, which is responsible for radio resource management, traffic scheduling, and RAN-side energy-saving decisions. Chen & Zhou Expires 7 January 2027 [Page 3] Internet-Draft coordinated-energy-saving-between-ran-an July 2026 The lower part represents the Transport Network (TN), which provides the connectivity between the RAN nodes and the core network. This part comprises three transport nodes arranged into a two-tier hierarchy, two access nodes, referred to as Access Node 1 and Access Node 2, and one aggregation node. Access Node 1 and Access Node 2 are directly interact with the RAN nodes, while the Aggregation Node provides aggregated streams toward the core network. All transport nodes in the TN are under the control of TN controller (e.g. for path computation and resource allocation), which is responsible for TN side energy-saving decisions such as port sleep, switching board sleep, and TDM timeslot deactivation, etc. The energy-saving coordination between the RAN and the TN may include: * Energy-related information advertisement: energy consumption prediction, link power status; * Energy-saving intent decomposition or policy: translating an operator-level energy-saving goal into concrete actions for both the RAN and the TN; * Action alignment: aligning wake-up latencies and co-sleep windows to avoid one domain sleeping while the other related resources remains active; * Traffic/load coordination: jointly migrating services and rerouting backhaul paths before shutting down a transport link; This coordination can be realized through four approaches: * Controller-to-Controller (C2C) coordination is best suited for policy-level and long-horizon tasks such as intent decomposition, global state aggregation, and joint energy-budget management, where minutes-to-hours decision cycles are acceptable. This approach may exist between peer controllers or orchestrators across RAN and TN for unified energy saving. * Node-to-Node (N2N) coordination is best suited for data-plane and short-horizon tasks such as real-time action synchronization, link adaptation, and rapid wake-up upon unexpected traffic bursts, where controller involvement would introduce latency. * Hybrid coordination combining both C2C and N2N is also possible. Chen & Zhou Expires 7 January 2027 [Page 4] Internet-Draft coordinated-energy-saving-between-ran-an July 2026 3. Extension Depending on the specific coordination approach, different extensions may be required. For C2C coordination, the interaction typically relies on CPIs and may necessitate extensions to existing YANG data models and intent objects within the IETF GREEN framework or network management agent coordinations. For N2N coordination, nodes may leverage existing protocols, such as LLDP, IPv6, or some OAM protocol, without introducing new protocols. This part requires further study within the GREEN framework and its YANG modules. 4. Informative References [I-D.belmq-green-framework] Claise, B., Contreras, L. M., Lindblad, J., Palmero, M. P., Stephan, E., and Q. Wu, "Framework for Energy Efficiency Management", Work in Progress, Internet-Draft, draft-belmq-green-framework-10, 8 February 2026, . [I-D.chen-green-transport-energy-saving] Chen, X., Zhou, J., and J. Yan, "Hybrid Energy Saving Mechanism for Transport Network", Work in Progress, Internet-Draft, draft-chen-green-transport-energy-saving- 01, 6 July 2026, . [I-D.ietf-green-terminology] Chen, G., Boucadair, M., Wu, Q., Contreras, L. M., and M. P. Palmero, "Terminology for Energy Efficiency Network Management", Work in Progress, Internet-Draft, draft-ietf- green-terminology-02, 30 June 2026, . [I-D.ietf-green-use-cases] Stephan, E., Palmero, M. P., Claise, B., Wu, Q., Contreras, L. M., Bernardos, C. J., and X. Chen, "Use Cases for Energy Efficiency Management", Work in Progress, Internet-Draft, draft-ietf-green-use-cases-01, 22 January 2026, . Authors' Addresses Chen & Zhou Expires 7 January 2027 [Page 5] Internet-Draft coordinated-energy-saving-between-ran-an July 2026 Xinyu Chen China Mobile No.32 Xuanwumen west street Beijing 100053 China Email: chenxinyuyjy@chinamobile.com Jin Zhou ZTE Corporation Email: zhou.jin6@zte.com.cn Chen & Zhou Expires 7 January 2027 [Page 6]