PCEP LS Extensions for Fine Granularity Metro Transport Network (fgMTN) Topology Resource Information Reporting
draft-han-pce-ls-fgmtn-reporting-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Liuyan Han , Haibin Huang , Minxue Wang , Li Zhang , Jin Zhou | ||
| Last updated | 2026-03-01 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
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draft-han-pce-ls-fgmtn-reporting-00
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
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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
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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.
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[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.
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[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.
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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.
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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
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(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:
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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
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(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.
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+=======+============================+===============+
| 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,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
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[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[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,
<https://www.rfc-editor.org/info/rfc9543>.
[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, <https://datatracker.ietf.org/doc/html/draft-ietf-
pce-pcep-ls-04>.
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
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Li Zhang
Huawei
Beiqing Road
Beijing
China
Email: zhangli344@huawei.com
Jin Zhou
ZTE Corporation
Shenzhen
China
Email: zhou.jin6@zte.com.cn
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