A PCE-based Control Plane Framework for Multi-Domain Deterministic Networking (DetNet)
draft-bernardos-detnet-multi-domain-pce-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Carlos J. Bernardos , Luis M. Contreras , Quan Xiong , Alain Mourad | ||
| Last updated | 2025-10-16 | ||
| RFC stream | (None) | ||
| Intended RFC status | (None) | ||
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draft-bernardos-detnet-multi-domain-pce-00
DETNET WG C.J. Bernardos, Ed.
Internet-Draft Universidad Carlos III de Madrid
Intended status: Standards Track L. Contreras
Expires: 19 April 2026 Telefonica
Q. Xiong
ZTE Corporation
A. Mourad
InterDigital
16 October 2025
A PCE-based Control Plane Framework for Multi-Domain Deterministic
Networking (DetNet)
draft-bernardos-detnet-multi-domain-pce-00
Abstract
Deterministic Networking (DetNet) provides the capability to carry
specified unicast or multicast data flows for real-time applications
with extremely low data loss rates and bounded latency over a path or
network. As DetNet deployments expand, they will inevitably need to
span multiple domains that may be under separate administrative or
technological control. This creates a need for a control plane
solution that can establish and maintain end-to-end DetNet services
across these domain boundaries.
This document defines a framework for a Path Computation Element
(PCE)-based control plane for multi-domain DetNet. It first
establishes a working definition of a "DetNet Domain" for the purpose
of path computation and control. It then describes two high-level
architectural approaches for inter-domain path computation and
resource reservation: a Hierarchical PCE model and a peer-to-peer PCE
"stitching" model. This framework provides the foundation for more
specific work on multi-domain DetNet solutions.
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/.
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Internet-Drafts are draft documents valid for a maximum of six months
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This Internet-Draft will expire on 19 April 2026.
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Copyright (c) 2025 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Terminology . . . . . . . . . . . . . . . . . 3
3. Defining a DetNet Domain . . . . . . . . . . . . . . . . . . 4
3.1. Domain Characteristics . . . . . . . . . . . . . . . . . 4
3.2. Scope of a DetNet Domain . . . . . . . . . . . . . . . . 4
4. PCE-based Multi-Domain DetNet Architectures . . . . . . . . . 5
4.1. Exemplary Use Case . . . . . . . . . . . . . . . . . . . 5
4.2. Problem Statement . . . . . . . . . . . . . . . . . . . . 6
4.3. Hierarchical PCE (H-PCE) Approach . . . . . . . . . . . . 6
4.4. Peer-to-Peer (Stitching) PCE Approach . . . . . . . . . . 7
5. Multi-Domain DetNet Flow Considerations . . . . . . . . . . . 7
5.1. End-to-End Path Computation . . . . . . . . . . . . . . . 7
5.2. Resource Management . . . . . . . . . . . . . . . . . . . 8
5.3. End-System awareness . . . . . . . . . . . . . . . . . . 8
5.4. Flow Aggregation . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
9.1. Normative References . . . . . . . . . . . . . . . . . . 9
9.2. Informative References . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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1. Introduction
The Deterministic Networking (DetNet) architecture, as defined in
[RFC8655], provides a service for flows requiring bounded latency,
and/or extremely low packet loss, and/or reliable service. The
initial focus of DetNet has largely been on single-domain networks,
where a single controller or administrative entity has full
visibility and control over all network resources.
However, many use cases, such as industrial automation, professional
audio/video, and smart grids, require deterministic connectivity that
spans multiple networks. These networks may be operated by different
providers (administrative domains), utilize different underlying
link-layer technologies (technological domains), or be structured as
separate control areas for scalability.
To support such scenarios, a control plane framework is needed to
coordinate the establishment of end-to-end DetNet paths across these
domain boundaries. The Path Computation Element (PCE) Communication
Protocol (PCEP) [RFC5440] provides a standard mechanism for a PCE to
compute paths and a Path Computation Client (PCC) to request them.
This makes PCE a suitable candidate for building a multi-domain
DetNet control plane.
This document builds on the DetNet Controller Plane Framework
[I-D.ietf-detnet-controller-plane-framework] by focusing specifically
on multi-domain challenges. It proposes a foundational framework by:
* Defining what constitutes a "domain" in the context of DetNet path
computation.
* Describing high-level PCE-based architectures for managing multi-
domain paths.
* Identifying key considerations for establishing and maintaining
DetNet flows across these domains.
The goal is to establish the necessary foundational concepts before
addressing specific technology implementations, such as multi-domain
RAW (Reliable and Available Wireless)
[I-D.bernardos-detnet-raw-multidomain].
2. Conventions and Terminology
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.
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This document uses the terminology defined in [RFC8655], [RFC4655]
and [RFC5440].
3. Defining a DetNet Domain
For the purpose of multi-domain DetNet control, a clear definition of
a "domain" is essential. A domain represents a collection of network
resources (nodes, links) that are managed and controlled as a single
entity for the purpose of DetNet path computation and resource
allocation.
3.1. Domain Characteristics
A DetNet domain is characterized by a set of network nodes that are
subject to a single, consistent set of DetNet control and management
policies. From a PCE-based control plane perspective, this typically
implies that:
* A single PCE instance (or a coordinated set of redundant PCEs) has
complete topological visibility within the domain.
* This PCE instance is responsible for computing paths and managing
the allocation of DetNet-specific resources (e.g., buffer space,
link schedules, queue reservations) for all nodes within that
domain.
* There is a trusted relationship and a secure communication channel
between the PCE and all the nodes it controls within the domain.
3.2. Scope of a DetNet Domain
The boundaries of a DetNet domain can be defined based on several
factors, which may overlap:
Administrative Domain: A set of network elements under the control
of a single network operator or administrative entity. This is
the most common interpretation. Inter-domain communication occurs
when a path must cross from one operator's network to another's.
PCE Control Domain: A domain is defined as the set of nodes
controlled by a single PCE instance. This is the primary
definition used within this framework. A large administrative
domain might be divided into multiple smaller PCE control domains
for scalability.
Technological Domain: A domain could be defined by the consistent
use of a specific data plane technology (e.g., a TSN domain, an
3GPP 5G domain) or queuing mechanism (e.g. queuing solutions
within the categories as per
[I-D.ietf-detnet-dataplane-taxonomy]). While paths may cross
technological boundaries, this document posits that this does not
inherently define a control plane domain boundary. A single PCE
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SHOULD be capable of managing a domain comprising multiple
technologies. Similarly, the specific queuing mechanisms (e.g.,
[RFC9016]) supported by devices do not define a domain boundary; a
single domain can contain devices supporting multiple queuing
solutions, which can be used concurrently. PCE needs to select a
specific queuing mechanism along the path for a DetNet flow within
each domain.
4. PCE-based Multi-Domain DetNet Architectures
4.1. Exemplary Use Case
Let's consider the scenario depicted in the figure below, where a
DetNet flow is established between a source S and a destination D.
The path for the flow traverses three different domains. Domain 1 is
a wired domain, which could for example be a TSN-based DetNet MPLS
[RFC8964] or DetNet IP [RFC8939] network. Domain 2 is a wireless
(RAW) domain. Domain 3 is again a wired domain. The RAW domain
provides connectivity between the two wired domains. Note that this
is just an example, and other combinations of wired/wireless domains
could exist (e.g., a DetNet flow traversing a wired domain providing
connectivity between two RAW domains).
.------------------------------------.
| Parent PCE |
'------------------------------------'
^ | ^
| | |
v v v
.----------------. .----------------. .----------------.
| Child PCE (d1) | | Child PCE (d2) | | Child PCE (d3) |
'----------------' '----------------' '----------------'
| | | | | |
S ---- R1 ======== R2 -------- R3 ======== R4 -------- R5 ---- D
<-- Domain 1 --> <---- Domain 2 ----> <-- Domain 3 -->
(wired) (RAW) (wired)
S, D: end-systems (source and destination)
Rx: DetNet routers/bridges
==: wired link
--: wireless link
Figure 1: Exemplary multi-domain scenario
Each domain has its own PCE, which is responsible for path
computation and resource management within the domain. These are
referred to as Child PCEs (C-PCEs). Routers R2 and R3 are border
routers of Domain 2 (RAW), and R3 and R4 are border routers of Domain
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2 and 3, respectively. A Parent PCE (P-PCE) is responsible for the
end-to-end path computation and orchestration among the different
C-PCEs.
4.2. Problem Statement
In a multi-domain environment, no single PCE has end-to-end
visibility of the full network topology. The challenge is to compute
an end-to-end path that meets the strict latency, jitter, and loss
requirements of a DetNet flow, while respecting the administrative
and confidentiality boundaries of each participating domain.
Each domain's PCE is responsible for its own internal path
computation and resource allocation. The multi-domain architecture
must define how these individual PCEs cooperate to create a seamless
end-to-end service. Two primary models are considered: Hierarchical
PCE and Peer-to-Peer PCE.
4.3. Hierarchical PCE (H-PCE) Approach
The Hierarchical PCE (H-PCE) architecture [RFC6805] defines a parent-
child relationship between PCEs.
* A Parent PCE (P-PCE) has a partial, abstracted view of the child
domains. It does not see the detailed topology within each child
domain but knows the reachability and characteristics (e.g.,
available latency budget, cost) of paths to and through them.
* A Child PCE (C-PCE) has full visibility of its own domain's
topology and resources. It is responsible for all intra-domain
path computations.
In a multi-domain DetNet context:
1. A request for an end-to-end DetNet path is sent to the P-PCE.
This request includes the source, destination, and required QoS
parameters (e.g., maximum latency).
2. The P-PCE computes a high-level, domain-sequence path. This path
is a sequence of domains that the flow must traverse, along with
the entry and exit boundary nodes for each domain.
3. The P-PCE then sends requests to the C-PCE of each domain in the
path sequence. Each request asks for an intra-domain path
segment between the specified entry and exit nodes that meets a
portion of the end-to-end QoS requirements.
4. Each C-PCE computes its path segment, reserves the necessary
resources locally, and reports success or failure back to the
P-PCE.
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5. If all C-PCEs are successful, the P-PCE confirms the end-to-end
path. If any C-PCE fails, the P-PCE may attempt to find an
alternate domain path.
The Parent PCE (P-PCE) would be responsible for computing the multi-
domain path based on an abstracted topology of the different domains.
The Child PCEs (C-PCEs) are responsible for the path computation in
their own domains. A C-PCE would be aware of the specific
technologies used in its domain (e.g., RAW, DetNet IP, DetNet MPLS,
etc.), being able to compute a path taking into account the specific
constraints of the technology. For instance, in a RAW domain, the
C-PCE would be able to select the path, the schedule and the links to
be used to guarantee a certain level of reliability.
4.4. Peer-to-Peer (Stitching) PCE Approach
In a peer-to-peer approach, also known as "stitching," there is no
parent-child hierarchy. PCEs from adjacent domains cooperate as
peers. The path computation is performed sequentially from one
domain to the next. This model is described in [RFC5441] for inter-
area and inter-AS TE path computation.
In a multi-domain DetNet context:
1. The PCE in the source domain (PCE-1) receives a path request for
a flow destined for another domain.
2. PCE-1 computes a path from the source node to a suitable exit
border node in its domain.
3. PCE-1 then sends a PCEP request to the PCE of the adjacent domain
(PCE-2), specifying the entry border node (which is the exit node
from domain 1) and the final destination. The request includes
the remaining QoS budget.
4. PCE-2 computes a path through its domain to either the final
destination (if it's in domain 2) or to another suitable exit
border node. It then "stitches" this segment to the previous
one.
5. This process repeats until the PCE in the destination domain is
reached. The path is confirmed backward along the chain of PCEs.
5. Multi-Domain DetNet Flow Considerations
5.1. End-to-End Path Computation
The end-to-end path is a concatenation of intra-domain path segments.
The total latency and other QoS metrics are cumulative. The control
plane must be able to allocate the end-to-end budget among the
participating domains.
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In hierarchical PCE, the P-PCE needs to collect the domain-specific
information from C-PCEs and the P-PCE will divide the end-to-end
budget of a DetNet flow into sub-budgets to several domains based on
the capabilities (e.g. latency, jitter) within each domain.
In stitching PCE, the end-to-end budget of a DetNet will be divided
from the source PCE, then to an adjacent domain, till to the
destination PCE. The PCE within each domain needs to compute the
latency bound as per [RFC9320] considering the bounded latency
metric.
5.2. Resource Management
Resources MAY be reserved in each domain for the flow. If any domain
in the path cannot provide the required resources, the end-to-end
path setup fails. A mechanism for transactional, all-or-nothing
resource commitment across domains is highly desirable.
The control plane also needs to advertise inter-domain resource
information, including bandwidth, delay, jitter with related queuing
mechanisms for QoS coordination.
5.3. End-System awareness
A critical aspect is whether the end-systems (source and destination)
are DetNet-aware.
DetNet-aware End-Systems: The end-systems can signal their QoS
requirements and participate in the DetNet control plane.
DetNet-unaware End-Systems: The requirements for these systems must
be configured at the edge of the DetNet domain by a proxy or
network management system. In a multi-domain scenario, the entry
node of the first DetNet domain acts as this ingress point.
5.4. Flow Aggregation
Flow aggregation is recommended in the multi-domain scenario to
achieve the end-to-end QoS guarantees for aggregated flow(s) that
span across multiple domains. Multiple flows may be aggregated in a
domain and disaggregated in another domain. The network parameters
of an aggregated flow should be exchanged among different network
domains. The path computation should consider to identify the end-
to-end budget of the aggregated flow which should cover the
requirements of all member flows.
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6. Security Considerations
Multi-domain operations introduce significant security challenges.
The communication between PCEs in different domains MUST be secured,
ensuring authentication, integrity, and confidentiality. Each domain
must be protected from misbehaving or compromised peer domains.
Topology and resource information exposed by a domain's PCE to an
external entity (a parent PCE or a peer PCE) is a sensitive matter.
The framework must allow for policy-based control over the level of
abstraction and detail that is shared.
Considerations from [RFC8253] also applies.
7. IANA Considerations
This document makes no requests of IANA.
8. Acknowledgments
The work of Carlos J. Bernardos in this document has been partially
supported by the Horizon Europe DESIRE6G (Grant 101096466), and UNICO
I+D 6G-DATADRIVEN-04 project (TSI-063000-2021-132).
9. References
9.1. Normative References
[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>.
[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>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
9.2. Informative References
[I-D.bernardos-detnet-raw-multidomain]
Bernardos, C., et al., "Reliable and Available Wireless
(RAW) based on Multi-link and Multi-domain strategies",
Work in Progress, Internet-Draft, draft-bernardos-detnet-
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raw-multidomain-06,
<https://datatracker.ietf.org/doc/html/draft-bernardos-
detnet-raw-multidomain-06>.
[I-D.ietf-detnet-controller-plane-framework]
Saad, T., et al., "Deterministic Networking (DetNet)
Controller Plane Framework", Work in Progress, Internet-
Draft, draft-ietf-detnet-controller-plane-framework,
<https://datatracker.ietf.org/doc/html/draft-ietf-detnet-
controller-plane-framework>.
[I-D.ietf-detnet-dataplane-taxonomy]
Joung, J., Geng, X., Peng, S., and T. T. Eckert,
"Dataplane Enhancement Taxonomy", Work in Progress,
Internet-Draft, draft-ietf-detnet-dataplane-taxonomy-04, 7
July 2025, <https://datatracker.ietf.org/doc/html/draft-
ietf-detnet-dataplane-taxonomy-04>.
[RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
[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>.
[RFC5441] Vasseur, JP., Ed., "A Backward-Recursive PCE-Based
Computation (BRPC) Procedure to Compute Shortest
Constrained Inter-Domain Traffic Engineering Label
Switched Paths", RFC 5441, DOI 10.17487/RFC5441, April
2009, <https://www.rfc-editor.org/info/rfc5441>.
[RFC6805] King, D., Ed. and A. Farrel, Ed., "The Application of the
Path Computation Element Architecture to the Dark Side of
the Internet", RFC 6805, DOI 10.17487/RFC6805, November
2012, <https://www.rfc-editor.org/info/rfc6805>.
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.
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[RFC8939] Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane:
IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
<https://www.rfc-editor.org/rfc/rfc8939>.
[RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
S., and J. Korhonen, "Deterministic Networking (DetNet)
Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
2021, <https://www.rfc-editor.org/rfc/rfc8964>.
[RFC9016] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
S., and J. Korhonen, "Flow and Service Information Model
for Deterministic Networking (DetNet)", RFC 9016,
DOI 10.17487/RFC9016, May 2021,
<https://www.rfc-editor.org/info/rfc9016>.
[RFC9320] Finn, N., Le Boudec, J.-Y., Mohammadpour, E., Zhang, J.,
and B. Varga, "Deterministic Networking (DetNet) Bounded
Latency", RFC 9320, DOI 10.17487/RFC9320, November 2022,
<https://www.rfc-editor.org/rfc/rfc9320>.
Authors' Addresses
Carlos J. Bernardos (editor)
Universidad Carlos III de Madrid
Av. Universidad 30
28911 Leganes Madrid
Spain
Phone: +34 91624 6235
Email: cjbc@it.uc3m.es
URI: http://www.it.uc3m.es/cjbc
Luis M. Contreras
Telefonica
Spain
Email: luismiguel.contrerasmurillo@telefonica.com
Quan Xiong
ZTE Corporation
China
Email: xiong.quan@zte.com.cn
Alain Mourad
InterDigital Europe
Email: Alain.Mourad@InterDigital.com
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URI: http://www.InterDigital.com/
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