PCE Working Group L. Han Internet-Draft H. Huang Intended status: Standards Track M. Wang Expires: 2 September 2026 CMCC L. Zhang Huawei J. Zhou ZTE 1 March 2026 PCEP LS Extensions for Fine Granularity Metro Transport Network (fgMTN) Topology Resource Information Reporting draft-han-pce-ls-fgmtn-reporting-00 Abstract This document extends PCEP-LS by defining several new sub-TLVs for the LS object to report the fgMTN topology resource information, which includes timeslot occupation status of links and the relationship between the FGU client and the occupied timeslots. 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 2 September 2026. 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 Han, et al. Expires 2 September 2026 [Page 1] Internet-Draft draft-han-pce-ls-fgmtn-reporting-00 March 2026 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 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. Protocol Extensions . . . . . . . . . . . . . . . . . . . . . 3 2.1. OPEN Object . . . . . . . . . . . . . . . . . . . . . . . 3 2.1.1. LS Capability TLV . . . . . . . . . . . . . . . . . . 3 2.2. LS Object . . . . . . . . . . . . . . . . . . . . . . . . 3 2.2.1. Parent NRP ID Sub-TLV . . . . . . . . . . . . . . . . 4 2.2.2. Sub-Slot BitMap Sub-TLV . . . . . . . . . . . . . . . 4 2.2.3. FGU Client Sub-Slot Bitmap Relationship Sub-TLV . . . 5 2.2.4. FGU Client Sub-Slot Relationship Sub-TLV . . . . . . 7 3. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . 9 4. Security Considerations . . . . . . . . . . . . . . . . . . . 9 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10 7. Normative References . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 1. Introduction MTN(Metro Transport Network) [ITU-T_G.8310] is a new generation of transport network technology system defined by ITU-T. MTN integrates packet and TDM technologies, enabling compatibility with Ethernet protocol stacks while meeting differentiated requirements of the 5G era, such as hard isolation, low latency, and high reliability, thus further enhancing the bearer capability of 5G networks. On this basis, the fgMTN technology [ITU-T_G.8312.20]incorporates fine- grained slicing into the MTN architecture, providing a low-cost, refined, hard-isolated, and fine-grained bearer channels. The fgMTN technology further refines the granularity of hard slicing from 5 Gbit/s to 10 Mbit/s, meeting the differentiated service bearer requirements of vertical industry applications and private line services, such as small bandwidth, high isolation, and high security. The fgMTN technology is one of the means to realize network resource partitions(NRP) [RFC9543]. fgMTN uses the management and control system to perform centralized path computation. However, the current MTN management and control standard [ITU-T_G.8350] only defines the functions of topology and resource collection and does not specify specific protocols. Han, et al. Expires 2 September 2026 [Page 2] Internet-Draft draft-han-pce-ls-fgmtn-reporting-00 March 2026 [RFC5440] describes the Path Computation Element Communication Protocol (PCEP). PCEP defines the communication between a Path Computation Client (PCC) and a Path Computation Element (PCE), or between PCEs. PCEP-LS [I-D.ietf-pce-pcep-ls] extends PCEP to enable the collection of link-state and TE information from networks and sharing with PCE by extending a new LS Report message. Therefore, the PCEP-LS can be extended to support the reporting of fgMTN topology resources. This document extends PCEP-LS by defining several new sub-TLVs for the LS object to report the fgMTN topology resource information, which includes timeslot ccupation status of links and the relationship between the FGU client and the occupied timeslots. 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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2. Protocol Extensions 2.1. OPEN Object 2.1.1. LS Capability TLV [I-D.ietf-pce-pcep-ls] defines LS-CAPABILITY TLV for use in the OPEN Object for link-state (and TE) distribution via PCEP capability advertisement. This document defines a new flag in the flags field of the LS- CAPABILITY TLV to indicate the support of fgMTN resource information reporting. Bit M (fgMTN state collection, 1-bit): if set to 1 by a PCC, the M Flag indicates that the PCC allows the reporting of fgMTN resource information learned via other means like LLDP; if set to 1 by a PCE, the M Flag indicates that the PCE is capable of receiving fgMTN resource information. 2.2. LS Object The LS (link-state) object is defined by [I-D.ietf-pce-pcep-ls], it MUST be carried within LSRpt messages. The LS object contains a set of TLVs used to specify the target node's or link's information. Han, et al. Expires 2 September 2026 [Page 3] Internet-Draft draft-han-pce-ls-fgmtn-reporting-00 March 2026 [I-D.ietf-pce-pcep-ls] also defines the Link Descriptors TLV, it contains Link Descriptors for each link. The value of it contains one or more Link Descriptor Sub-TLVs. This document defines four kind of Link Descriptor Sub-TLVs to describe the fgMTN resource information. 2.2.1. Parent NRP ID Sub-TLV The Parent NRP ID sub-TLV indicates the NRP ID that the link belongs to. This sub-TLV is an optional sub-TLV MAY be included in the Link Descriptors TLV. At most one instance of this sub-TLV can be included in the Link Descriptors TLV. The format of this sub-TLV is shown in Figure 1. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | NRP-ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Parent NRP ID Sub-TLV where: Type: TBD1, needs to be allocated by IANA. Length: the length of NRP-ID, equals to 4. NRP-ID: 4-bit length, the value of NRP-ID is the slice ID of the service-layer interface (MTN client or GE/10GE interface) of a fine- grained interface. If t the information does not exist on the device, the default value 0xFFFFFFFF SHOULD be filled. 2.2.2. Sub-Slot BitMap Sub-TLV The sub-slot bitmap sub-TLV indicates the timeslot's occupation status of all FGU clients in the link. This sub-TLV is an optional sub-TLV MAY be included in the Link Descriptors TLV. At most one instance of this sub-TLV can be included in the Link Descriptors TLV. The format of this sub-TLV is shown in Figure 2. Han, et al. Expires 2 September 2026 [Page 4] Internet-Draft draft-han-pce-ls-fgmtn-reporting-00 March 2026 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | / Sub-slot bitmap (variable) / | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Parent NRP ID Sub-TLV where: Type: TBD2, needs to be allocated by IANA. Length: the length of sub-slot bitmap, variable. Sub-slot bitmap: variable, indicates the occupation state of all the timeslots of the link, each bit represents a timeslot. If the last bits are all zeros, the padding can be omitted. 2.2.3. FGU Client Sub-Slot Bitmap Relationship Sub-TLV The FGU Client Sub-Slot Bitmap Relationship sub-TLV indicates the relationship between the occupied timeslots(expressed by bitmap) and corresponding FGU Client. This sub-TLV is an optional sub-TLV MAY be included in the Link Descriptors TLV. More than one instance of this sub-TLV can be included in the Link Descriptors TLV. The format of this sub-TLV is shown in Figure 3. Han, et al. Expires 2 September 2026 [Page 5] Internet-Draft draft-han-pce-ls-fgmtn-reporting-00 March 2026 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | FGU Client Port index | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | FGU Client number | Reserved | Start Position| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | / Forward fg Channel index (22 Bytes) / | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | / Backward fg Channel index (22 Bytes) / | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | / Sub-slot bitmap (variable) / | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: FGU Client Sub-Slot BitMap RelationShip Sub-TLV where: Type: TBD3, needs to be allocated by IANA. Length: the length of value field, variable. FGU Client Port index: 4-byte length, the local FGU client port identifier allocated by the device itself, which is unique within a network device. The value ranges from 1 to 0xFFFFFFFF. The value 0 indicates an invalid value. FGU Client number: 2-byte length, the FGU client identifier negotiated by the source and destination device, which is unique within a MTN client. The value ranges from 1 to 1022. The value 0 indicates not used, and the value 1023 is reserved. Start Position: 1-byte length, the start position of the timeslots occupied by the current FGU client. It is expressed in bytes. The timeslots are arranged in the order of timeslots 0 to 959. The value of this field ranges from 0 to 119. Forward fg Channel index: 22-byte length, forward fg channel identifier. It is a unique channel ID on the entire network, which is identified by the combination of the source device's MPLS LSR ID Han, et al. Expires 2 September 2026 [Page 6] Internet-Draft draft-han-pce-ls-fgmtn-reporting-00 March 2026 (16 bytes, device IPv4 or IPv6 address), fg Channel ID (4 bytes, allocated by the management and control system, unique within the source node), and LSP ID (2 bytes, allocated by the management and control system, used to distinguish the original path from the rerouting path). Backward fg Channel index: 22-byte length, backward fg channel identifier. It is a unique channel ID on the entire network, which is identified by the combination of the following information: MPLS LSR ID (16 bytes, IPv4 or IPv6 address of the device) of the reverse source, fg Channel ID (4 bytes, allocated by the management and control system, unique within the source node), and LSP ID (2 bytes, allocated by management and control system, used to distinguish the original path from the rerouting path). Sub-slot bitmap: variable, indicates the occupation state of all the sub-slots of the FGU. It starts from the start position. If the last bits are all zeros, the padding can be omitted. 2.2.4. FGU Client Sub-Slot Relationship Sub-TLV The FGU Client Sub-Slot Bitmap Relationship sub-TLV indicates the relationship between the occupied timeslots(expressed by enumeration value) and FGU Client. This sub-TLV is an optional sub-TLV MAY be included in the Link Descriptors TLV. More than one instance of this sub-TLV can be included in the Link Descriptors TLV. The format of this sub-TLV is shown in Figure 4: Han, et al. Expires 2 September 2026 [Page 7] Internet-Draft draft-han-pce-ls-fgmtn-reporting-00 March 2026 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | FGU Client index | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | FGU Client number | Reserved | Start Position| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | / Forward fg Channel index (22 Bytes) / | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | / Backward fg Channel index (22 Bytes) / | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | / Sub-Slot IDs (variable) / | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: FGU Client Sub-Slot Relationship Sub-TLV where: Type: TBD4, needs to be allocated by IANA. Length: the length of value field, variable. FGU Client Port index: 4-byte length, the local FGU client port identifier allocated by the device itself, which is unique within a network device. The value ranges from 1 to 0xFFFFFFFF. The value 0 indicates an invalid value. FGU Client number: 2-byte length, the FGU client identifier negotiated by the source and destination device, which is unique within a MTN client. The value ranges from 1 to 1022. The value 0 indicates not used, and the value 1023 is reserved. Start Position: 1-byte length, the start position of the timeslots occupied by the current FGU client. It is expressed in bytes. The timeslots are arranged in the order of timeslots 0 to 959. The value of this field ranges from 0 to 119. Forward fg Channel index: 22-byte length, forward fg channel identifier. It is a unique channel ID on the entire network, which is identified by the combination of the source device's MPLS LSR ID Han, et al. Expires 2 September 2026 [Page 8] Internet-Draft draft-han-pce-ls-fgmtn-reporting-00 March 2026 (16 bytes, device IPv4 or IPv6 address), fg Channel ID (4 bytes, allocated by the management and control system, unique within the source node), and LSP ID (2 bytes, allocated by the management and control system, used to distinguish the original path from the rerouting path). Backward fg Channel index: 22-byte length, backward fg channel identifier. It is a unique channel ID on the entire network, which is identified by the combination of the following information: MPLS LSR ID (16 bytes, IPv4 or IPv6 address of the device) of the reverse source, fg Channel ID (4 bytes, allocated by the management and control system, unique within the source node), and LSP ID (2 bytes, allocated by management and control system, used to distinguish the original path from the rerouting path). Sub-slot IDs: Variable length, indicates the enumerated value of the sub-slots occupied by the current FGU client. Each sub-slot ID is represented by 2 bytes. The number of sub-slot ID ranges from 0 to 959. 3. Procedures TBD. 4. Security Considerations TBD. 5. IANA Considerations [I-D.ietf-pce-pcep-ls] requests IANA to create a "PCEP-LS Sub-TLV Types" sub-registry for the sub-TLVs carried in the PCEP-LS TLV. This document requests IANA to make the following allocations from this sub-registry. Han, et al. Expires 2 September 2026 [Page 9] Internet-Draft draft-han-pce-ls-fgmtn-reporting-00 March 2026 +=======+============================+===============+ | Value | Description | Reference | +=======+============================+===============+ | TBD1 | Parent NRP ID Sub-TLV | This document | +-------+----------------------------+---------------+ | TBD2 | Sub-Slot Bitmap Sub-TLV | This document | +-------+----------------------------+---------------+ | TBD3 | FGU Client Sub-Slot Bitmap | This document | | | Relationship Sub-TLV | | +-------+----------------------------+---------------+ | TBD4 | FGU Client Sub-Slot | This document | | | Relationship Sub-TLV | | +-------+----------------------------+---------------+ Table 1: IANA Considerations 6. Acknowledgments TBD. 7. Normative References [ITU-T_G.8312.20] ITU-T, "ITU-T G.8312.20:Overview of fine grain MTN; 01/2024", https://www.itu.int/rec/T-REC-G.8312.20, January 2024. [ITU-T_G.8310] ITU-T, "ITU-T G.8310: Architecture of the metro transport network; 01/2024", https://www.itu.int/rec/T-REC-G.8310, March 2025. [ITU-T_G.8350] ITU-T, "ITU-T G.8350: Management and control of metro transport networks; 11/2022", https://www.itu.int/rec/T- REC-G.8350, November 2022. [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, DOI 10.17487/RFC5440, March 2009, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . Han, et al. Expires 2 September 2026 [Page 10] Internet-Draft draft-han-pce-ls-fgmtn-reporting-00 March 2026 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9543] Farrel, A., Ed., Drake, J., Ed., Rokui, R., Homma, S., Makhijani, K., Contreras, L., and J. Tantsura, "A Framework for Network Slices in Networks Built from IETF Technologies", RFC 9543, DOI 10.17487/RFC9543, March 2024, . [I-D.ietf-pce-pcep-ls] Dhody, D., Peng, S., Lee, Y., Ceccarelli, D., Wang, A., and G. S. Mishra, "PCEP extensions for Distribution of Link-State and TE Information", Work in Progress, Internet-Draft, draft-ietf-pce-pcep-ls-04, 14 October 2025, . Authors' Addresses Liuyan Han China Mobile No.32 Xuanwumen west street Beijing 100053 China Email: hanliuyan@chinamobile.com Haibin Huang China Mobile No.32 Xuanwumen west street Beijing 100053 China Email: huanghaibin@chinamobile.com Minxue Wang China Mobile No.32 Xuanwumen west street Beijing 100053 China Email: wangminxue@chinamobile.com Han, et al. Expires 2 September 2026 [Page 11] Internet-Draft draft-han-pce-ls-fgmtn-reporting-00 March 2026 Li Zhang Huawei Beiqing Road Beijing China Email: zhangli344@huawei.com Jin Zhou ZTE Corporation Shenzhen China Email: zhou.jin6@zte.com.cn Han, et al. Expires 2 September 2026 [Page 12]