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IETF RFC 9730
Last modified on Tuesday, March 4th, 2025
 Permanent link to RFC 9730
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Internet Engineering Task Force (IETF) H. Zheng
Request for Comments: 9730 Y. Lin
Category: Informational Huawei Technologies
ISSN: 2070-1721 Y. Zhao
China Mobile
Y. Xu
CAICT
D. Beller
Nokia
March 2025
Interworking of GMPLS Control and Centralized Controller Systems
 Abstract
Generalized Multiprotocol Label Switching (GMPLS) control allows each
network element (NE) to perform local resource discovery, routing,
and signaling in a distributed manner.
The advancement of software-defined transport networking technology
enables a group of NEs to be managed through centralized controller
hierarchies. This helps to tackle challenges arising from multiple
domains, vendors, and technologies. An example of such a centralized
architecture is the Abstraction and Control of Traffic-Engineered
Networks (ACTN) controller hierarchy, as described in RFC 8453.
Both the distributed and centralized control planes have their
respective advantages and should complement each other in the system,
rather than compete. This document outlines how the GMPLS
distributed control plane can work together with a centralized
controller system in a transport network.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are candidates for any level of Internet
Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/RFC 9730.
Copyright Notice
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
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. Abbreviations
3. Overview
3.1. Overview of GMPLS Control Plane
3.2. Overview of Centralized Controller System
3.3. GMPLS Control Interworking with a Centralized Controller
System
4. Discovery Options
4.1. LMP
5. Routing Options
5.1. OSPF-TE
5.2. IS-IS-TE
5.3. NETCONF/RESTCONF
6. Path Computation
6.1. Controller-Based Path Computation
6.2. Constraint-Based Path Computing in GMPLS Control
6.3. Path Computation Element (PCE)
7. Signaling Options
7.1. RSVP-TE
8. Interworking Scenarios
8.1. Topology Collection and Synchronization
8.2. Multi-Domain Service Provisioning
8.3. Multi-Layer Service Provisioning
8.3.1. Multi-Layer Path Computation
8.3.2. Cross-Layer Path Creation
8.3.3. Link Discovery
8.4. Recovery
8.4.1. Span Protection
8.4.2. LSP Protection
8.4.3. Single-Domain LSP Restoration
8.4.4. Multi-Domain LSP Restoration
8.4.5. Fast Reroute
8.5. Controller Reliability
9. Manageability Considerations
10. Security Considerations
11. IANA Considerations
12. References
12.1. Normative References
12.2. Informative References
Acknowledgements
Contributors
Authors' Addresses
1. Introduction
Generalized Multiprotocol Label Switching (GMPLS) [RFC 3945] extends
MPLS to support different classes of interfaces and switching
capabilities such as Time-Division Multiplex Capable (TDM), Lambda
Switch Capable (LSC), and Fiber-Switch Capable (FSC). Each network
element (NE) running a GMPLS control plane collects network
information from other NEs and supports service provisioning through
signaling in a distributed manner. A more generic description of
traffic-engineering networking information exchange can be found in
[RFC 7926].
On the other hand, Software-Defined Networking (SDN) technologies
have been introduced to control the transport network centrally.
Centralized controllers can collect network information from each
node and provision services on corresponding nodes. One example is
the Abstraction and Control of Traffic-Engineered Networks (ACTN)
[RFC 8453], which defines a hierarchical architecture with the
Provisioning Network Controller (PNC), Multi-Domain Service
Coordinator (MDSC), and Customer Network Controller (CNC) as
centralized controllers for different network abstraction levels. A
PCE-based approach has been proposed in [RFC 7491]: Application-Based
Network Operations (ABNO).
GMPLS can be used to control network elements (NEs) in such
centralized controller architectures. A centralized controller may
support GMPLS-enabled domains and communicate with a GMPLS-enabled
domain where the GMPLS control plane handles service provisioning
from ingress to egress. In this scenario, the centralized controller
sends a request to the entry node and does not need to configure all
NEs along the path within the domain from ingress to egress, thus
leveraging the GMPLS control plane. This document describes how the
GMPLS control plane interworks with a centralized controller system
in a transport network.
2. Abbreviations
The following abbreviations are used in this document.
ACTN: Abstraction and Control of Traffic-Engineered Networks
[RFC 8453]
APS: Automatic Protection Switching [G.808.1]
BRPC: Backward Recursive PCE-Based Computation [RFC 5441]
CSPF: Constrained Shortest Path First
DoS: Denial of Service
E2E: end to end
ERO: Explicit Route Object
FA: Forwarding Adjacency
FRR: Fast Reroute
GMPLS: Generalized Multiprotocol Label Switching [RFC 3945]
H-PCE: Hierarchical PCE [RFC 8685]
IDS: Intrusion Detection System
IGP: Interior Gateway Protocol
IoCs: Indicators of Compromise [RFC 9424]
IPS: Intrusion Prevention System
IS-IS: Intermediate System to Intermediate System
LMP: Link Management Protocol [RFC 4204]
LSP: Label Switched Path
LSP-DB: LSP Database
MD: multi-domain
MDSC: Multi-Domain Service Coordinator [RFC 8453]
MITM: Man in the Middle
ML: multi-layer
MPI: MDSC to PNC Interface [RFC 8453]
NE: network element
NETCONF: Network Configuration Protocol [RFC 6241]
NMS: Network Management System
OSPF: Open Shortest Path First
PCC: Path Computation Client [RFC 4655]
PCE: Path Computation Element [RFC 4655]
PCEP: PCE Communication Protocol [RFC 5440]
PCEP-LS: Link State PCEP [PCEP-LS]
PLR: Point of Local Repair
PNC: Provisioning Network Controller [RFC 8453]
RSVP: Resource Reservation Protocol
SBI: Southbound Interface
SDN: Software-Defined Networking
TE: Traffic Engineering
TED: Traffic Engineering Database
TLS: Transport Layer Security [RFC 8446]
VNTM: Virtual Network Topology Manager [RFC 5623]
3. Overview
This section provides an overview of the GMPLS control plane,
centralized controller systems, and their interactions in transport
networks.
A transport network [RFC 5654] is a server-layer network designed to
provide connectivity services for client-layer connectivity. This
setup allows client traffic to be carried seamlessly across the
server-layer network resources.
3.1. Overview of GMPLS Control Plane
GMPLS separates the control plane and the data plane to support time-
division, wavelength, and spatial switching, which are significant in
transport networks. For the NE level control in GMPLS, each node
runs a GMPLS control plane instance. Functionalities such as service
provisioning, protection, and restoration can be performed via GMPLS
communication among multiple NEs. At the same time, the GMPLS
control plane instance can also collect information about node and
link resources in the network to construct the network topology and
compute routing paths for serving service requests.
Several protocols have been designed for the GMPLS control plane
[RFC 3945], including link management [RFC 4204], signaling [RFC 3471],
and routing [RFC 4202] protocols. The GMPLS control plane instances
applying these protocols communicate with each other to exchange
resource information and establish LSPs. In this way, GMPLS control
plane instances in different nodes in the network have the same view
of the network topology and provision services based on local
policies.
3.2. Overview of Centralized Controller System
With the development of SDN technologies, a centralized controller
architecture has been introduced to transport networks. One example
architecture can be found in ACTN [RFC 8453]. In such systems, a
controller is aware of the network topology and is responsible for
provisioning incoming service requests.
Multiple hierarchies of controllers are designed at different levels
to implement different functions. This kind of architecture enables
multi-vendor, multi-domain, and multi-technology control. For
example, a higher-level controller coordinates several lower-level
controllers controlling different domains for topology collection and
service provisioning. Vendor-specific features can be abstracted
between controllers, and a standard API (e.g., generated from
RESTCONF [RFC 8040] / YANG [RFC 7950]) may be used.
3.3. GMPLS Control Interworking with a Centralized Controller System
Besides GMPLS and the interactions among the controller hierarchies,
it is also necessary for the controllers to communicate with the
network elements. Within each domain, GMPLS control can be applied
to each NE. The bottom-level centralized controller can act as an NE
to collect network information and initiate LSPs. Figure 1 shows an
example of GMPLS interworking with centralized controllers (ACTN
terminologies are used in the figure).
+-------------------+
| Orchestrator |
| (MDSC) |
+-------------------+
^ ^ ^
| | |
+-------------+ | +--------------+
| |RESTCONF/YANG modules |
V V V
+-------------+ +-------------+ +-------------+
|Controller(N)| |Controller(G)| |Controller(G)|
| (PNC) | | (PNC) | | (PNC) |
+-------------+ +-------------+ +-------------+
^ ^ ^ ^ ^ ^
| | | | | |
NETCONF| |PCEP NETCONF| |PCEP NETCONF| |PCEP
/YANG | | /YANG | | /YANG | |
V V V V V V
.----------. Inter- .----------. Inter- .----------.
/ \ domain / \ domain / \
| | link | LMP | link | LMP |
| |======| OSPF-TE |======| OSPF-TE |
| | | RSVP-TE | | RSVP-TE |
\ / \ / \ /
`----------` `----------` `----------`
Non-GMPLS domain 1 GMPLS domain 2 GMPLS domain 3
Figure 1: Example of GMPLS/non-GMPLS Interworking with Controllers
Controller(N): A domain controller controlling a non-GMPLS domain
Controller(G): A domain controller controlling a GMPLS domain
Figure 1 shows the scenario with two GMPLS domains and one non-GMPLS
domain. This system supports the interworking among non-GMPLS
domains, GMPLS domains, and the controller hierarchies.
For domain 1, the network elements were not enabled with GMPLS, so
the control is purely from the controller, via Network Configuration
Protocol (NETCONF) [RFC 6241] with a YANG data model [RFC 7950] and/or
PCE Communication Protocol (PCEP) [RFC 5440].
For domains 2 and 3:
* Each domain has the GMPLS control plane enabled at the physical
network level. The Provisioning Network Controller (PNC) can
exploit GMPLS capabilities implemented in the domain to listen to
the IGP routing protocol messages (for example, OSPF Link State
Advertisements (LSAs)) that the GMPLS control plane instances are
disseminating into the network and thus learn the network
topology. For path computation in the domain with the PNC
implementing a PCE, Path Computation Clients (PCCs) (e.g., NEs,
other controllers/PCEs) use PCEP to ask the PNC for a path and get
replies. The Multi-Domain Service Coordinator (MDSC) communicates
with PNCs using, for example, Representational State Transfer
(REST) / RESTCONF based on YANG data models. As a PNC has learned
its domain topology, it can report the topology to the MDSC. When
a service arrives, the MDSC computes the path and coordinates PNCs
to establish the corresponding LSP segment.
* Alternatively, the NETCONF protocol can be used to retrieve
topology information utilizing the YANG module in [RFC 8795] and
the technology-specific YANG module augmentations required for the
specific network technology. The PNC can retrieve topology
information from any NE (the GMPLS control plane instance of each
NE in the domain has the same topological view), construct the
topology of the domain, and export an abstract view to the MDSC.
Based on the topology retrieved from multiple PNCs, the MDSC can
create a topology graph of the multi-domain network and can use it
for path computation. To set up a service, the MDSC can exploit
the YANG module in [YANG-TE] together with the technology-specific
YANG module augmentations.
This document focuses on the interworking between GMPLS and the
centralized controller system, including:
* the interworking between the GMPLS domains and the centralized
controllers (including the orchestrator, if it exists) controlling
the GMPLS domains and
* the interworking between a non-GMPLS domain (which is controlled
by a centralized controller system) and a GMPLS domain, through
the controller hierarchy architecture.
For convenience, this document uses the following terminologies for
the controller and the orchestrator:
Controller(G): A domain controller controlling a GMPLS domain (the
Controller(G) of the GMPLS domains 2 and 3 in Figure 1)
Controller(N): A domain controller controlling a non-GMPLS domain
(the Controller(N) of the non-GMPLS domain 1 in Figure 1)
H-Controller(G): A domain controller controlling the higher-layer
GMPLS domain, in the context of multi-layer networks
L-Controller(G): A domain controller controlling the lower-layer
GMPLS domain, in the context of multi-layer networks
H-Controller(N): A domain controller controlling the higher-layer
non-GMPLS domain, in the context of multi-layer networks
L-Controller(N): A domain controller controlling the lower-layer
non-GMPLS domain, in the context of multi-layer networks
Orchestrator(MD): An orchestrator used to orchestrate the multi-
domain networks
Orchestrator(ML): An orchestrator used to orchestrate the multi-
layer networks
4. Discovery Options
In GMPLS control, the link connectivity must be verified between each
pair of nodes. In this way, link resources, which are fundamental
resources in the network, are discovered by both ends of the link.
4.1. LMP
The Link Management Protocol (LMP) [RFC 4204] runs between nodes and
manages TE links. In addition to the setup and maintenance of
control channels, LMP can be used to verify the data link
connectivity and correlate the link properties.
5. Routing Options
In GMPLS control, link state information is flooded within the
network as defined in [RFC 4202]. Each node in the network can build
the network topology according to the flooded link state information.
Routing protocols such as OSPF-TE [RFC 4203] and IS-IS-TE [RFC 5307]
have been extended to support different interfaces in GMPLS.
In a centralized controller system, the centralized controller can be
placed in the GMPLS network and passively receives the IGP
information flooded in the network. In this way, the centralized
controller can construct and update the network topology.
5.1. OSPF-TE
OSPF-TE is introduced for TE networks in [RFC 3630]. OSPF extensions
have been defined in [RFC 4203] to enable the capability of link state
information for the GMPLS network. Based on this work, OSPF has been
extended to support technology-specific routing. The routing
protocols for the Optical Transport Network (OTN), Wavelength
Switched Optical Network (WSON), and optical flexi-grid networks are
defined in [RFC 7138], [RFC 7688], and [RFC 8363], respectively.
5.2. IS-IS-TE
IS-IS-TE is introduced for TE networks in [RFC 5305], is extended to
support GMPLS routing functions [RFC 5307], and has been updated
[RFC 7074] to support the latest GMPLS switching capability and Types
fields.
5.3. NETCONF/RESTCONF
NETCONF [RFC 6241] and RESTCONF [RFC 8040] protocols are originally
used for network configuration. These protocols can also utilize
topology-related YANG modules, such as those in [RFC 8345] and
[RFC 8795]. These protocols provide a powerful mechanism for the
notification (in addition to the provisioning and monitoring) of
topology changes to the client.
6. Path Computation
6.1. Controller-Based Path Computation
Once a controller learns the network topology, it can utilize the
available resources to serve service requests by performing path
computation. Due to abstraction, the controllers may not have
sufficient information to compute the optimal path. In this case,
the controller can interact with other controllers by sending, for
example, YANG-based path computation requests [PATH-COMP] or PCEP to
compute a set of potential optimal paths; and then, based on its
constraints, policy, and specific knowledge (e.g., cost of access
link), the controller can choose the more feasible path for end-to-
end (E2E) service path setup.
Path computation is one of the key objectives in various types of
controllers. In the given architecture, it is possible for different
components that have the capability to compute the path.
6.2. Constraint-Based Path Computing in GMPLS Control
In GMPLS control, a routing path may be computed by the ingress node
[RFC 3473] based on the ingress node Traffic Engineering Database
(TED). In this case, constraint-based path computation is performed
according to the local policy of the ingress node.
6.3. Path Computation Element (PCE)
The PCE was first introduced in [RFC 4655] as a functional component
that offers services for computing paths within a network. In
[RFC 5440], path computation is achieved using the TED, which
maintains a view of the link resources in the network. The
introduction of the PCE has significantly improved the quality of
network planning and offline computation. However, there is a
potential risk that the computed path may be infeasible when there is
a diversity requirement, as a stateless PCE lacks knowledge about
previously computed paths.
To address this issue, a stateful PCE has been proposed in [RFC 8231].
Besides the TED, an additional LSP Database (LSP-DB) is introduced to
archive each LSP computed by the PCE. This way, the PCE can easily
determine the relationship between the computing path and former
computed paths. In this approach, the PCE provides computed paths to
the PCC, and then the PCC decides which path is deployed and when it
is to be established.
With PCE-initiated LSPs [RFC 8281], the PCE can trigger the PCC to
perform setup, maintenance, and teardown of the PCE-initiated LSP
under the stateful PCE model. This would allow a dynamic network
that is centrally controlled and deployed.
In a centralized controller system, the PCE can be implemented within
the centralized controller. The centralized controller then
calculates paths based on its local policies. Alternatively, the PCE
can be located outside of the centralized controller. In this
scenario, the centralized controller functions as a PCC and sends a
path computation request to the PCE using the PCEP. A reference
architecture for this can be found in [RFC 7491].
7. Signaling Options
Signaling mechanisms are used to set up LSPs in GMPLS control.
Messages are sent hop by hop between the ingress node and the egress
node of the LSP to allocate labels. Once the labels are allocated
along the path, the LSP setup is accomplished. Signaling protocols
such as Resource Reservation Protocol - Traffic Engineering (RSVP-TE)
[RFC 3473] have been extended to support different interfaces in
GMPLS.
7.1. RSVP-TE
RSVP-TE is introduced in [RFC 3209] and extended to support GMPLS
signaling in [RFC 3473]. Several label formats are defined for a
generalized label request, a generalized label, a suggested label,
and label sets. Based on [RFC 3473], RSVP-TE has been extended to
support technology-specific signaling. The RSVP-TE extensions for
the OTN, WSON, and optical flexi-grid network are defined in
[RFC 7139], [RFC 7689], and [RFC 7792], respectively.
8. Interworking Scenarios
8.1. Topology Collection and Synchronization
Topology information is necessary on both network elements and
controllers. The topology on a network element is usually raw
information, while the topology used by the controller can be either
raw, reduced, or abstracted. Three different abstraction methods
have been described in [RFC 8453], and different controllers can
select the corresponding method depending on the application.
When there are changes in the network topology, the impacted network
elements need to report changes to all the other network elements,
together with the controller, to sync up the topology information.
The inter-NE synchronization can be achieved via protocols mentioned
in Sections 4 and 5. The topology synchronization between NEs and
controllers can either be achieved by routing protocols OSPF-TE/PCEP-
LS in [PCEP-LS] or NETCONF protocol notifications with a YANG module.
8.2. Multi-Domain Service Provisioning
Service provisioning can be deployed based on the topology
information on controllers and network elements. Many methods have
been specified for single-domain service provisioning, such as the
PCEP and RSVP-TE methods.
Multi-domain service provisioning would require coordination among
the controller hierarchies. Given the service request, the end-to-
end delivery procedure may include interactions at any level (i.e.,
interface) in the hierarchy of the controllers (e.g., MPI and SBI for
ACTN). The computation for a cross-domain path is usually completed
by controllers who have a global view of the topologies. Then the
configuration is decomposed into lower-level controllers to configure
the network elements to set up the path.
A combination of centralized and distributed protocols may be
necessary to interact between network elements and controllers.
Several methods can be used to create the inter-domain path:
1) With an end-to-end RSVP-TE session:
In this method, all the domains need to support the RSVP-TE
protocol and thus need to be GMPLS domains. The Controller(G) of
the source domain triggers the source node to create the end-to-
end RSVP-TE session; and the assignment and distribution of the
labels on the inter-domain links are done by the border nodes of
each domain, using RSVP-TE protocol. Therefore, this method
requires the interworking of RSVP-TE protocols between different
domains.
There are two possible methods:
1.1) One single end-to-end RSVP-TE session:
In this method, an end-to-end RSVP-TE session from the
source node to the destination node will be used to create
the inter-domain path. A typical example would be the PCE
initiation scenario, in which a PCE message (PCInitiate) is
sent from the Controller(G) to the source node, triggering
an RSVP procedure along the path. Similarly, the
interaction between the controller and the source node of
the source domain can be achieved by using the NETCONF
protocol with corresponding YANG modules, and then it can
be completed by running RSVP among the network elements.
1.2) LSP Stitching:
The LSP stitching method defined in [RFC 5150] can also
create the E2E LSP. That is, when the source node receives
an end-to-end path creation request (e.g., using PCEP or
NETCONF protocol), the source node starts an end-to-end
RSVP-TE session along the endpoints of each LSP segment
(S-LSP) (refers to S-LSP in [RFC 5150]) of each domain, to
assign the labels on the inter-domain links between each
pair of neighbor S-LSPs and to stitch the end-to-end LSP to
each S-LSP. See Figure 2 as an example.
Note that the S-LSP in each domain can be either created by
its Controller(G) in advance or created dynamically
triggered by the end-to-end RSVP-TE session.
+------------------------+
| Orchestrator(MD) |
+-----------+------------+
|
+---------------+ +------V-------+ +---------------+
| Controller(G) | | Controller(G)| | Controller(G) |
+-------+-------+ +------+-------+ +-------+-------+
| | |
+--------V--------+ +-------V--------+ +--------V--------+
|Client | | | | Client|
|Signal Domain 1| | Domain 2 | |Domain 3 Signal|
| | | | | | | |
|+-+-+ | | | | +-+-+|
|| | | +--+ +--+| |+--+ +--+ +--+| |+--+ +--+ | | ||
|| | | | | | || || | | | | || || | | | | | ||
|| ******************************************************** ||
|| | | | | || || | | | | || || | | | | ||
|+---+ +--+ +--+| |+--+ +--+ +--+| |+--+ +--+ +---+|
+-----------------+ +----------------+ +-----------------+
| . . . . . . |
| .<-S-LSP 1->. .<- S-LSP 2 -->. .<-S-LSP 3->. |
| . . . . |
|-------------->.---->.------------->.---->.-------------->|
|<--------------.<----.<-------------.<----.<--------------|
| End-to-end RSVP-TE session for LSP stitching |
Figure 2: LSP Stitching
2) Without an end-to-end RSVP-TE session:
In this method, each domain can be a GMPLS domain or a non-GMPLS
domain. Each controller (which may be a Controller(G) or a
Controller(N)) is responsible for creating the path segment
within its domain. The border node does not need to communicate
with other border nodes in other domains for the distribution of
labels on inter-domain links, so an end-to-end RSVP-TE session
through multiple domains is not required, and the interworking of
the RSVP-TE protocol between different domains is not needed.
Note that path segments in the source domain and the destination
domain are "asymmetrical" segments, because the configuration of
client signal mapping into the server-layer tunnel is needed at
only one end of the segment, while configuration of the server-
layer cross-connect is needed at the other end of the segment.
See the example in Figure 3.
+------------------------+
| Orchestrator(MD) |
+-----------+------------+
|
+---------------+ +------V-------+ +---------------+
| Controller | | Controller | | Controller |
+-------+-------+ +------+-------+ +-------+-------+
| | |
+--------V--------+ +-------V--------+ +--------V--------+
|Client Domain 1| | Domain 2 | | Domain 3 Client|
|Signal | | | | Signal|
| | Server layer| | | | | |
| | tunnel | | | | | |
|+-+-+ ^ | | | | +-+-+|
|| | | +--+ |+--+| |+--+ +--+ +--+| |+--+ +--+ | | ||
|| | | | | || || || | | | | || || | | | | | ||
|| ******************************************************** ||
|| | | | | || . || | | | | || . || | | | | ||
|+---+ +--+ +--+| . |+--+ +--+ +--+| . |+--+ +--+ +---+|
+-----------------+ . +----------------+ . +-----------------+
. . . .
.<-Path Segment 1->.<--Path Segment 2-->.<-Path Segment 3->.
Figure 3: Example of an Asymmetrical Path Segment
The PCEP / GMPLS protocols should support the creation of such
asymmetrical segments.
Note also that mechanisms to assign the labels in the inter-
domain links also need to be considered. There are two possible
methods:
2.1) Inter-domain labels assigned by NEs:
The concept of a stitching label that allows stitching
local path segments was introduced in [RFC 5150] and
[SPCE-ID], in order to form the inter-domain path crossing
several different domains. It also describes the Backward
Recursive PCE-Based Computation (BRPC) [RFC 5441] and
Hierarchical PCE (H-PCE) [RFC 8685] PCInitiate procedure,
i.e., the ingress node of each downstream domain assigns
the stitching label for the inter-domain link between the
downstream domain and its upstream neighbor domain; and
this stitching label will be passed to the upstream
neighbor domain by PCE protocol, which will be used for the
path segment creation in the upstream neighbor domain.
2.2) Inter-domain labels assigned by the controller:
If the resources of inter-domain links are managed by the
Orchestrator(MD), each domain controller can provide to the
Orchestrator(MD) the list of available labels (e.g., time
slots if the OTN is the scenario) using topology-related
YANG modules and specific technology-related extensions.
Once the orchestrator(MD) has computed the E2E path, RSVP-
TE or PCEP can be used in the different domains to set up
the related segment tunnel consisting of information about
inter-domain labels; for example, for PCEP, the label
Explicit Route Object (ERO) can be included in the
PCInitiate message to indicate the inter-domain labels so
that each border node of each domain can configure the
correct cross-connect within itself.
8.3. Multi-Layer Service Provisioning
GMPLS can interwork with centralized controller systems in multi-
layer networks.
+----------------+
|Orchestrator(ML)|
+------+--+------+
| | Higher-layer Network
| | .--------------------.
| | / \
| | +--------------+ | +--+ Link +--+ |
| +-->| H-Controller +----->| | |**********| | |
| +--------------+ | +--+ +--+ |
| \ . . /
| `--.------------.---`
| . .
| .---.------------.---.
| / . . \
| +--------------+ | +--+ +--+ +--+ |
+----->| L-Controller +----->| | ============== | |
+--------------+ | +--+ +--+ +--+ |
\ H-LSP /
`-------------------`
Lower-layer Network
Figure 4: GMPLS-controller Interworking in Multi-Layer Networks
An example with two layers of network is shown in Figure 4. In this
example, the GMPLS control plane is enabled in at least one layer
network (otherwise, it is out of the scope of this document) and
interworks with the controller of its domain (H-Controller and
L-Controller, respectively). The Orchestrator(ML) is used to
coordinate the control of the multi-layer network.
8.3.1. Multi-Layer Path Computation
[RFC 5623] describes three inter-layer path computation models and
four inter-layer path control models:
* 3 path computation models:
- Single PCE path computation model
- Multiple PCE path computation with inter-PCE communication
model
- Multiple PCE path computation without inter-PCE communication
model
* 4 path control models:
- PCE Virtual Network Topology Manager (PCE-VNTM) cooperation
model
- Higher-layer signaling trigger model
- Network Management System VNTM (NMS-VNTM) cooperation model
(integrated flavor)
- NMS-VNTM cooperation model (separate flavor)
Section 4.2.4 of [RFC 5623] also provides all the possible
combinations of inter-layer path computation and inter-layer path
control models.
To apply [RFC 5623] in a multi-layer network with GMPLS-controller
interworking, the H-Controller and the L-Controller can act as the
PCE Hi and PCE Lo, respectively; and typically, the Orchestrator(ML)
can act as a VNTM because it has the abstracted view of both the
higher-layer and lower-layer networks.
Table 1 shows all possible combinations of path computation and path
control models in multi-layer network with GMPLS-controller
interworking:
+======================+========+================+===============+
| Path computation / | Single | Multiple PCE | Multiple PCE |
| Path control | PCE | with inter-PCE | w/o inter-PCE |
+======================+========+================+===============+
| PCE-VNTM cooperation | N/A | Yes | Yes |
+----------------------+--------+----------------+---------------+
| Higher-layer | N/A | Yes | Yes |
| signaling trigger | | | |
+----------------------+--------+----------------+---------------+
| NMS-VNTM cooperation | N/A | Yes (1) | No (1) |
| (integrated flavor) | | | |
+----------------------+--------+----------------+---------------+
| NMS-VNTM cooperation | N/A | No (1) | Yes (1) |
| (separate flavor) | | | |
+----------------------+--------+----------------+---------------+
Table 1: Combinations of Path Computation and Path Control Models
Note that:
* Since there is one PCE in each layer network, the path computation
model "Single PCE path computation" is not applicable (N/A).
* For the other two path computation models "Multiple PCE with
inter-PCE" and "Multiple PCE w/o inter-PCE", the possible
combinations are the same as defined in [RFC 5623]. More
specifically:
- (1) The path control models "NMS-VNTM cooperation (integrated
flavor)" and "NMS-VNTM cooperation (separate flavor)" are the
typical models to be used in a multi-layer network with GMPLS-
controller interworking. This is because, in these two models,
the path computation is triggered by the NMS or VNTM. And in
the centralized controller system, the path computation
requests are typically from the Orchestrator(ML) (acts as
VNTM).
- For the other two path control models "PCE-VNTM cooperation"
and "Higher-layer signaling trigger", the path computation is
triggered by the NEs, i.e., the NE performs PCC functions. It
is still possible to use these two models, although they are
not the main methods.
8.3.2. Cross-Layer Path Creation
In a multi-layer network, a lower-layer LSP in the lower-layer
network can be created, which will construct a new link in the
higher-layer network. Such a lower-layer LSP is called Hierarchical
LSP, or H-LSP for short; see [RFC 6107].
The new link constructed by the H-LSP can then be used by the higher-
layer network to create new LSPs.
As described in [RFC 5212], two methods are introduced to create the
H-LSP: the static (pre-provisioned) method and the dynamic
(triggered) method.
1) Static (pre-provisioned) method:
In this method, the H-LSP in the lower-layer network is created
in advance. After that, the higher-layer network can create LSPs
using the resource of the link constructed by the H-LSP.
The Orchestrator(ML) is responsible to decide the creation of
H-LSP in the lower-layer network if it acts as a VNTM. Then it
requests the L-Controller to create the H-LSP via, for example,
an MPI under the ACTN architecture.
If the lower-layer network is a GMPLS domain, the L-Controller(G)
can trigger the GMPLS control plane to create the H-LSP. As a
typical example, the PCInitiate message can be used for the
communication between the L-Controller and the source node of the
H-LSP. And the source node of the H-LSP can trigger the RSVP-TE
signaling procedure to create the H-LSP, as described in
[RFC 6107].
If the lower-layer network is a non-GMPLS domain, other methods
may be used by the L-Controller(N) to create the H-LSP, which is
out of scope of this document.
2) Dynamic (triggered) method:
In this method, the signaling of LSP creation in the higher-layer
network will trigger the creation of H-LSP in the lower-layer
network dynamically, if it is necessary. Therefore, both the
higher-layer and lower-layer networks need to support the RSVP-TE
protocol and thus need to be GMPLS domains.
In this case, after the cross-layer path is computed, the
Orchestrator(ML) requests the H-Controller(G) for the cross-layer
LSP creation. As a typical example, the MPI under the ACTN
architecture could be used.
The H-Controller(G) can trigger the GMPLS control plane to create
the LSP in the higher-layer network. As a typical example, the
PCInitiate message can be used for the communication between the
H-Controller(G) and the source node of the higher-layer LSP, as
described in Section 4.3 of [RFC 8282]. At least two sets of ERO
information should be included to indicate the routes of higher-
layer LSP and lower-layer H-LSP.
The source node of the higher-layer LSP follows the procedure
defined in Section 4 of [RFC 6001] to trigger the GMPLS control
plane in both the higher-layer network and the lower-layer
network to create the higher-layer LSP and the lower-layer H-LSP.
On success, the source node of the H-LSP should report the
information of the H-LSP to the L-Controller(G) via, for example,
the PCRpt message.
8.3.3. Link Discovery
If the higher-layer network and the lower-layer network are under the
same GMPLS control plane instance, the H-LSP can be a Forwarding
Adjacency LSP (FA-LSP). Then the information of the link constructed
by this FA-LSP can be advertised in the routing instance, so that the
H-Controller can be aware of this new FA. [RFC 4206] and the
following updates to it (including [RFC 6001] and [RFC 6107]) describe
the detailed extensions to support advertisement of an FA.
If the higher-layer network and the lower-layer network are under
separate GMPLS control plane instances or if one of the layer
networks is a non-GMPLS domain, after an H-LSP is created in the
lower-layer network, the link discovery procedure will be triggered
in the higher-layer network to discover the information of the link
constructed by the H-LSP. The LMP defined in [RFC 4204] can be used
if the higher-layer network supports GMPLS. The information of this
new link will be advertised to the H-Controller.
8.4. Recovery
The GMPLS recovery functions are described in [RFC 4426]. Span
protection and end-to-end protection and restoration are discussed
with different protection schemes and message exchange requirements.
Related RSVP-TE extensions to support end-to-end recovery are
described in [RFC 4872]. The extensions in [RFC 4872] include
protection, restoration, preemption, and rerouting mechanisms for an
end-to-end LSP. Besides end-to-end recovery, a GMPLS segment
recovery mechanism is defined in [RFC 4873], which also intends to be
compatible with Fast Reroute (FRR) (see [RFC 4090], which defines
RSVP-TE extensions for the FRR mechanism, and [RFC 8271], which
describes the updates of the GMPLS RSVP-TE protocol for FRR of GMPLS
TE-LSPs).
8.4.1. Span Protection
Span protection refers to the protection of the link between two
neighboring switches. The main protocol requirements include:
* Link management: Link property correlation on the link protection
type
* Routing: Announcement of the link protection type
* Signaling: Indication of link protection requirement for that LSP
GMPLS already supports the above requirements, and there are no new
requirements in the scenario of interworking between GMPLS and a
centralized controller system.
8.4.2. LSP Protection
The LSP protection includes end-to-end and segment LSP protection.
For both cases:
* In the provisioning phase:
In both single-domain and multi-domain scenarios, the disjoint
path computation can be done by the centralized controller system,
as it has the global topology and resource view. And the path
creation can be done by the procedure described in Section 8.2.
* In the protection switchover phase:
In both single-domain and multi-domain scenarios, the existing
standards provide the distributed way to trigger the protection
switchover, for example, the data plane Automatic Protection
Switching (APS) mechanism described in [G.808.1], [RFC 7271], and
[RFC 8234] or the GMPLS Notify mechanism described in [RFC 4872] and
[RFC 4873]. In the scenario of interworking between GMPLS and a
centralized controller system, using these distributed mechanisms
rather than a centralized mechanism (i.e., the controller triggers
the protection switchover) can significantly shorten the
protection switching time.
8.4.3. Single-Domain LSP Restoration
* Pre-planned LSP protection (including shared-mesh restoration):
In pre-planned protection, the protecting LSP is established only
in the control plane in the provisioning phase and will be
activated in the data plane once failure occurs.
In the scenario of interworking between GMPLS and a centralized
controller system, the route of protecting LSP can be computed by
the centralized controller system. This takes the advantage of
making better use of network resources, especially for the
resource-sharing in shared-mesh restoration.
* Full LSP rerouting:
In full LSP rerouting, the normal traffic will be switched to an
alternate LSP that is fully established only after a failure
occurrence.
As described in [RFC 4872] and [RFC 4873], the alternate route can
be computed on demand when there is a failure occurrence or can be
pre-computed and stored before a failure occurrence.
In a fully distributed scenario, the pre-computation method offers
a faster restoration time but has the risk that the pre-computed
alternate route may become out-of-date due to the changes of the
network.
In the scenario of interworking between GMPLS and a centralized
controller system, the pre-computation of the alternate route
could take place in the centralized controller (and may be stored
in the controller or the head-end node of the LSP). In this way,
any changes in the network can trigger the refreshment of the
alternate route by the centralized controller. This makes sure
that the alternate route will not become out-of-date.
8.4.4. Multi-Domain LSP Restoration
A working LSP may traverse multiple domains, each of which may or may
not support a GMPLS distributed control plane.
If all the domains support GMPLS, both the end-to-end rerouting
method and the domain segment rerouting method could be used.
If only some domains support GMPLS, the domain segment rerouting
method could be used in those GMPLS domains. For other domains that
do not support GMPLS, other mechanisms may be used to protect the LSP
segments, which are out of scope of this document.
1) End-to-end rerouting:
In this scenario, a failure on the working LSP inside any domain
or on the inter-domain links will trigger the end-to-end
restoration.
In both pre-planned and full LSP rerouting, the end-to-end
protecting LSP could be computed by the centralized controller
system and could be created by the procedure described in
Section 8.2. Note that the end-to-end protecting LSP may
traverse different domains from the working LSP, depending on the
result of multi-domain path computation for the protecting LSP.
+----------------+
|Orchestrator(MD)|
+-------.--------+
............................................
. . . .
+----V-----+ +----V-----+ +----V-----+ +----V-----+
|Controller| |Controller| |Controller| |Controller|
| (G) 1 | | (G) 2 | | (G) 3 | | (G) 4 |
+----.-----+ +-------.--+ +-------.--+ +----.-----+
. . . .
+----V--------+ +-V-----------+ . +-------V-----+
| Domain 1 | | Domain 2 | . | Domain 4 |
|+---+ +---+| |+---+ +---+| . |+---+ +---+|
|| ===/~/======/~~~/================================ ||
|+-*-+ +---+| |+---+ +---+| . |+---+ +-*-+|
| * | +-------------+ . | * |
| * | . | * |
| * | +-------------+ . | * |
| * | | Domain 3 <... | * |
|+-*-+ +---+| |+---+ +---+| |+---+ +-*-+|
|| ************************************************* ||
|+---+ +---+| |+---+ +---+| |+---+ +---+|
+-------------+ +-------------+ +-------------+
====: Working LSP ****: Protecting LSP /~/: Failure
Figure 5: End-to-End Restoration
2) Domain segment rerouting:
2.1) Intra-domain rerouting:
If failure occurs on the working LSP segment in a GMPLS
domain, the segment rerouting [RFC 4873] could be used for
the working LSP segment in that GMPLS domain. Figure 6
shows an example of intra-domain rerouting.
The intra-domain rerouting of a non-GMPLS domain is out of
scope of this document.
+----------------+
|Orchestrator(MD)|
+-------.--------+
............................................
. . . .
+----V-----+ +----V-----+ +----V-----+ +----V-----+
|Controller| |Controller| |Controller| |Controller|
| (G) 1 | |(G)/(N) 2 | |(G)/(N) 3 | |(G)/(N) 4 |
+----.-----+ +-------.--+ +-------.--+ +----.-----+
. . . .
+----V--------+ +-V-----------+ . +-------V-----+
| Domain 1 | | Domain 2 | . | Domain 4 |
|+---+ +---+| |+---+ +---+| . |+---+ +---+|
|| ===/~/=========================================== ||
|+-*-+ +-*-+| |+---+ +---+| . |+---+ +---+|
| * * | +-------------+ . | |
| * * | . | |
| * * | +-------------+ . | |
| * * | | Domain 3 <... | |
|+-*-+ +-*-+| |+---+ +---+| |+---+ +---+|
|| ********* || || | | || || | | ||
|+---+ +---+| |+---+ +---+| |+---+ +---+|
+-------------+ +-------------+ +-------------+
====: Working LSP ****: Rerouting LSP segment /~/: Failure
Figure 6: Intra-Domain Segment Rerouting
2.2) Inter-domain rerouting:
If intra-domain segment rerouting failed (e.g., due to lack
of resource in that domain), or if failure occurs on the
working LSP on an inter-domain link, the centralized
controller system may coordinate with other domain(s) to
find an alternative path or path segment to bypass the
failure and then trigger the inter-domain rerouting
procedure. Note that the rerouting path or path segment
may traverse different domains from the working LSP.
The domains involved in the inter-domain rerouting
procedure need to be GMPLS domains, which support the RSVP-
TE signaling for the creation of a rerouting LSP segment.
For inter-domain rerouting, the interaction between GMPLS
and a centralized controller system is needed:
* A report of the result of intra-domain segment rerouting
to its Controller(G) and then to the Orchestrator(MD).
The former could be supported by the PCRpt message in
[RFC 8231], while the latter could be supported by the
MPI of ACTN.
* A report of inter-domain link failure to the two
Controllers (e.g., Controller(G) 1 and Controller(G) 2
in Figure 7) by which the two ends of the inter-domain
link are controlled, respectively, and then to the
Orchestrator(MD). The former could be done as described
in Section 8.1, while the latter could be supported by
the MPI of ACTN.
* The computation of a rerouting path or path segment
crossing multi-domains by the centralized controller
system (see [PATH-COMP]);
* The creation of a rerouting LSP segment in each related
domain. The Orchestrator(MD) can send the LSP segment
rerouting request to the source Controller(G) (e.g.,
Controller(G) 1 in Figure 7) via MPI interface, and then
the Controller(G) can trigger the creation of a
rerouting LSP segment through multiple GMPLS domains
using GMPLS rerouting signaling. Note that the
rerouting LSP segment may traverse a new domain that the
working LSP does not traverse (e.g., Domain 3 in
Figure 7).
+----------------+
|Orchestrator(MD)|
+-------.--------+
..................................................
. . . .
+-----V------+ +-----V------+ +-----V------+ +-----V------+
| Controller | | Controller | | Controller | | Controller |
| (G) 1 | | (G) 2 | | (G) 3 | | (G)/(N) 4 |
+-----.------+ +------.-----+ +-----.------+ +-----.------+
. . . .
+-----V-------+ +----V--------+ . +------V------+
| Domain 1 | | Domain 2 | . | Domain 4 |
|+---+ +---+| |+---+ +---+| . |+---+ +---+|
|| | | || || | | || . || | | ||
|| ============/~/========================================== ||
|| * | | || || | | * || . || | | ||
|+-*-+ +---+| |+---+ +-*-+| . |+---+ +---+|
| * | +----------*--+ . | |
| * | ***** . | |
| * | +----------*-----V----+ | |
| * | | *Domain 3 | | |
|+-*-+ +---+| |+---+ +-*-+ +---+| |+---+ +---+|
|| * | | || || | | * | | || || | | ||
|| ******************************* | | || || | | ||
|| | | || || | | | | || || | | ||
|+---+ +---+| |+---+ +---+ +---+| |+---+ +---+|
+-------------+ +---------------------+ +-------------+
====: Working LSP ****: Rerouting LSP segment /~/: Failure
Figure 7: Inter-Domain Segment Rerouting
8.4.5. Fast Reroute
[RFC 4090] defines two methods of fast reroute: the one-to-one backup
method and the facility backup method. For both methods:
1) Path computation of protecting LSP:
In Section 6.2 of [RFC 4090], the protecting LSP (detour LSP in
one-to-one backup or bypass tunnel in facility backup) could be
computed by the Point of Local Repair (PLR) using, for example, a
Constrained Shortest Path First (CSPF) computation. In the
scenario of interworking between GMPLS and a centralized
controller system, the protecting LSP could also be computed by
the centralized controller system, as it has the global view of
the network topology, resources, and information of LSPs.
2) Protecting LSP creation:
In the scenario of interworking between GMPLS and a centralized
controller system, the protecting LSP could still be created by
the RSVP-TE signaling protocol as described in [RFC 4090] and
[RFC 8271].
In addition, if the protecting LSP is computed by the centralized
controller system, the Secondary Explicit Route Object defined in
[RFC 4873] could be used to explicitly indicate the route of the
protecting LSP.
3) Failure detection and traffic switchover:
If a PLR detects that failure occurs, it may significantly
shorten the protection switching time by using the distributed
mechanisms described in [RFC 4090] to switch the traffic to the
related detour LSP or bypass tunnel rather than doing so in a
centralized way.
8.5. Controller Reliability
The reliability of the controller is crucial due to its important
role in the network. It is essential that if the controller is shut
down or disconnected from the network, all currently provisioned
services in the network continue to function and carry traffic. In
addition, protection switching to pre-established paths should also
work. It is desirable to have protection mechanisms, such as
redundancy, to maintain full operational control even if one instance
of the controller fails. This can be achieved through controller
backup or functionality backup. There are several controller backup
or federation mechanisms in the literature. It is also more reliable
to have function backup in the network element to guarantee
performance in the network.
9. Manageability Considerations
Each network entity, including controllers and network elements,
should be managed properly and with the relevant trust and security
policies applied (see Section 10), as they will interact with other
entities. The manageability considerations in controller hierarchies
and network elements still apply, respectively. The overall
manageability of the protocols applied in the network should also be
a key consideration.
The responsibility of each entity should be clarified. The control
of function and policy among different controllers should be
consistent via a proper negotiation process.
10. Security Considerations
This document outlines the interworking between GMPLS and controller
hierarchies. The security requirements specific to both systems
remain applicable. Protocols referenced herein possess security
considerations, which must be adhered to, with their core
specifications and identified risks detailed earlier in this
document.
Security is a critical aspect in both GMPLS and controller-based
networks. Ensuring robust security mechanisms in these environments
is paramount to safeguard against potential threats and
vulnerabilities. Below are expanded security considerations and some
relevant IETF RFC references.
* Authentication and Authorization: It is essential to implement
strong authentication and authorization mechanisms to control
access to the controller from multiple network elements. This
ensures that only authorized devices and users can interact with
the controller, preventing unauthorized access that could lead to
network disruptions or data breaches. "The Transport Layer
Security (TLS) Protocol Version 1.3" [RFC 8446] and "Enrollment
over Secure Transport" [RFC 7030] provide guidelines on secure
communication and certificate-based authentication that can be
leveraged for these purposes.
* Controller Security: The controller's security is crucial as it
serves as the central control point for the network elements. The
controller must be protected against various attacks, such as
Denial of Service (DoS), Man in the Middle (MITM), and
unauthorized access. Security mechanisms should include regular
security audits, application of security patches, firewalls, and
Intrusion Detection Systems (IDSs) / Intrusion Prevention Systems
(IPSs).
* Data Transport Security: Security mechanisms on the controller
should also safeguard the underlying network elements against
unauthorized usage of data transport resources. This includes
encryption of data in transit to prevent eavesdropping and
tampering as well as ensuring data integrity and confidentiality.
* Secure Protocol Implementation: Protocols used within the GMPLS
and controller frameworks must be implemented with security in
mind. Known vulnerabilities should be addressed, and secure
versions of protocols should be used wherever possible.
Finally, robust network security often depends on Indicators of
Compromise (IoCs) to detect, trace, and prevent malicious activities
in networks or endpoints. These are described in [RFC 9424] along
with the fundamentals, opportunities, operational limitations, and
recommendations for IoC use.
11. IANA Considerations
This document has no IANA actions.
12. References
12.1. Normative References
[RFC 3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC 3209, December 2001,
<https://www.rfc-editor.org/info/RFC 3209>.
[RFC 3473] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Resource ReserVation Protocol-
Traffic Engineering (RSVP-TE) Extensions", RFC 3473,
DOI 10.17487/RFC 3473, January 2003,
<https://www.rfc-editor.org/info/RFC 3473>.
[RFC 3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
DOI 10.17487/RFC 3630, September 2003,
<https://www.rfc-editor.org/info/RFC 3630>.
[RFC 3945] Mannie, E., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Architecture", RFC 3945,
DOI 10.17487/RFC 3945, October 2004,
<https://www.rfc-editor.org/info/RFC 3945>.
[RFC 4090] Pan, P., Ed., Swallow, G., Ed., and A. Atlas, Ed., "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
DOI 10.17487/RFC 4090, May 2005,
<https://www.rfc-editor.org/info/RFC 4090>.
[RFC 4203] Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions in
Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4203, DOI 10.17487/RFC 4203, October 2005,
<https://www.rfc-editor.org/info/RFC 4203>.
[RFC 4206] Kompella, K. and Y. Rekhter, "Label Switched Paths (LSP)
Hierarchy with Generalized Multi-Protocol Label Switching
(GMPLS) Traffic Engineering (TE)", RFC 4206,
DOI 10.17487/RFC 4206, October 2005,
<https://www.rfc-editor.org/info/RFC 4206>.
[RFC 4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
Computation Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC 4655, August 2006,
<https://www.rfc-editor.org/info/RFC 4655>.
[RFC 4872] Lang, J.P., Ed., Rekhter, Y., Ed., and D. Papadimitriou,
Ed., "RSVP-TE Extensions in Support of End-to-End
Generalized Multi-Protocol Label Switching (GMPLS)
Recovery", RFC 4872, DOI 10.17487/RFC 4872, May 2007,
<https://www.rfc-editor.org/info/RFC 4872>.
[RFC 4873] Berger, L., Bryskin, I., Papadimitriou, D., and A. Farrel,
"GMPLS Segment Recovery", RFC 4873, DOI 10.17487/RFC 4873,
May 2007, <https://www.rfc-editor.org/info/RFC 4873>.
[RFC 5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, DOI 10.17487/RFC 5305, October
2008, <https://www.rfc-editor.org/info/RFC 5305>.
[RFC 5307] Kompella, K., Ed. and Y. Rekhter, Ed., "IS-IS Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 5307, DOI 10.17487/RFC 5307, October 2008,
<https://www.rfc-editor.org/info/RFC 5307>.
[RFC 5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC 5440, March 2009,
<https://www.rfc-editor.org/info/RFC 5440>.
[RFC 6001] Papadimitriou, D., Vigoureux, M., Shiomoto, K., Brungard,
D., and JL. Le Roux, "Generalized MPLS (GMPLS) Protocol
Extensions for Multi-Layer and Multi-Region Networks (MLN/
MRN)", RFC 6001, DOI 10.17487/RFC 6001, October 2010,
<https://www.rfc-editor.org/info/RFC 6001>.
[RFC 6107] Shiomoto, K., Ed. and A. Farrel, Ed., "Procedures for
Dynamically Signaled Hierarchical Label Switched Paths",
RFC 6107, DOI 10.17487/RFC 6107, February 2011,
<https://www.rfc-editor.org/info/RFC 6107>.
[RFC 6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC 6241, June 2011,
<https://www.rfc-editor.org/info/RFC 6241>.
[RFC 7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed.,
"Enrollment over Secure Transport", RFC 7030,
DOI 10.17487/RFC 7030, October 2013,
<https://www.rfc-editor.org/info/RFC 7030>.
[RFC 7074] Berger, L. and J. Meuric, "Revised Definition of the GMPLS
Switching Capability and Type Fields", RFC 7074,
DOI 10.17487/RFC 7074, November 2013,
<https://www.rfc-editor.org/info/RFC 7074>.
[RFC 7491] King, D. and A. Farrel, "A PCE-Based Architecture for
Application-Based Network Operations", RFC 7491,
DOI 10.17487/RFC 7491, March 2015,
<https://www.rfc-editor.org/info/RFC 7491>.
[RFC 7926] Farrel, A., Ed., Drake, J., Bitar, N., Swallow, G.,
Ceccarelli, D., and X. Zhang, "Problem Statement and
Architecture for Information Exchange between
Interconnected Traffic-Engineered Networks", BCP 206,
RFC 7926, DOI 10.17487/RFC 7926, July 2016,
<https://www.rfc-editor.org/info/RFC 7926>.
[RFC 7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC 7950, August 2016,
<https://www.rfc-editor.org/info/RFC 7950>.
[RFC 8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC 8040, January 2017,
<https://www.rfc-editor.org/info/RFC 8040>.
[RFC 8271] Taillon, M., Saad, T., Ed., Gandhi, R., Ed., Ali, Z., and
M. Bhatia, "Updates to the Resource Reservation Protocol
for Fast Reroute of Traffic Engineering GMPLS Label
Switched Paths (LSPs)", RFC 8271, DOI 10.17487/RFC 8271,
October 2017, <https://www.rfc-editor.org/info/RFC 8271>.
[RFC 8282] Oki, E., Takeda, T., Farrel, A., and F. Zhang, "Extensions
to the Path Computation Element Communication Protocol
(PCEP) for Inter-Layer MPLS and GMPLS Traffic
Engineering", RFC 8282, DOI 10.17487/RFC 8282, December
2017, <https://www.rfc-editor.org/info/RFC 8282>.
[RFC 8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol
Version 1.3", RFC 8446, DOI 10.17487/RFC 8446, August 2018,
<https://www.rfc-editor.org/info/RFC 8446>.
[RFC 8453] Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
Abstraction and Control of TE Networks (ACTN)", RFC 8453,
DOI 10.17487/RFC 8453, August 2018,
<https://www.rfc-editor.org/info/RFC 8453>.
[RFC 8685] Zhang, F., Zhao, Q., Gonzalez de Dios, O., Casellas, R.,
and D. King, "Path Computation Element Communication
Protocol (PCEP) Extensions for the Hierarchical Path
Computation Element (H-PCE) Architecture", RFC 8685,
DOI 10.17487/RFC 8685, December 2019,
<https://www.rfc-editor.org/info/RFC 8685>.
[RFC 8795] Liu, X., Bryskin, I., Beeram, V., Saad, T., Shah, H., and
O. Gonzalez de Dios, "YANG Data Model for Traffic
Engineering (TE) Topologies", RFC 8795,
DOI 10.17487/RFC 8795, August 2020,
<https://www.rfc-editor.org/info/RFC 8795>.
[RFC 9424] Paine, K., Whitehouse, O., Sellwood, J., and A. Shaw,
"Indicators of Compromise (IoCs) and Their Role in Attack
Defence", RFC 9424, DOI 10.17487/RFC 9424, August 2023,
<https://www.rfc-editor.org/info/RFC 9424>.
12.2. Informative References
[G.808.1] ITU-T, "Generic protection switching - Linear trail and
subnetwork protection", ITU-T Recommendation G.808.1, May
2014, <https://www.itu.int/rec/T-REC-G.808.1-201405-I/en>.
[PATH-COMP]
Busi, I., Belotti, S., de Dios, O. G., Sharma, A., and Y.
Shi, "A YANG Data Model for requesting path computation",
Work in Progress, Internet-Draft, draft-ietf-teas-yang-
path-computation-24, 13 February 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
yang-path-computation-24>.
[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-02, 20 October
2024, <https://datatracker.ietf.org/doc/html/draft-ietf-
pce-pcep-ls-02>.
[RFC 3471] Berger, L., Ed., "Generalized Multi-Protocol Label
Switching (GMPLS) Signaling Functional Description",
RFC 3471, DOI 10.17487/RFC 3471, January 2003,
<https://www.rfc-editor.org/info/RFC 3471>.
[RFC 4202] Kompella, K., Ed. and Y. Rekhter, Ed., "Routing Extensions
in Support of Generalized Multi-Protocol Label Switching
(GMPLS)", RFC 4202, DOI 10.17487/RFC 4202, October 2005,
<https://www.rfc-editor.org/info/RFC 4202>.
[RFC 4204] Lang, J., Ed., "Link Management Protocol (LMP)", RFC 4204,
DOI 10.17487/RFC 4204, October 2005,
<https://www.rfc-editor.org/info/RFC 4204>.
[RFC 4426] Lang, J., Ed., Rajagopalan, B., Ed., and D. Papadimitriou,
Ed., "Generalized Multi-Protocol Label Switching (GMPLS)
Recovery Functional Specification", RFC 4426,
DOI 10.17487/RFC 4426, March 2006,
<https://www.rfc-editor.org/info/RFC 4426>.
[RFC 5150] Ayyangar, A., Kompella, K., Vasseur, JP., and A. Farrel,
"Label Switched Path Stitching with Generalized
Multiprotocol Label Switching Traffic Engineering (GMPLS
TE)", RFC 5150, DOI 10.17487/RFC 5150, February 2008,
<https://www.rfc-editor.org/info/RFC 5150>.
[RFC 5212] Shiomoto, K., Papadimitriou, D., Le Roux, JL., Vigoureux,
M., and D. Brungard, "Requirements for GMPLS-Based Multi-
Region and Multi-Layer Networks (MRN/MLN)", RFC 5212,
DOI 10.17487/RFC 5212, July 2008,
<https://www.rfc-editor.org/info/RFC 5212>.
[RFC 5441] Vasseur, JP., Ed., Zhang, R., Bitar, N., and JL. Le Roux,
"A Backward-Recursive PCE-Based Computation (BRPC)
Procedure to Compute Shortest Constrained Inter-Domain
Traffic Engineering Label Switched Paths", RFC 5441,
DOI 10.17487/RFC 5441, April 2009,
<https://www.rfc-editor.org/info/RFC 5441>.
[RFC 5623] Oki, E., Takeda, T., Le Roux, JL., and A. Farrel,
"Framework for PCE-Based Inter-Layer MPLS and GMPLS
Traffic Engineering", RFC 5623, DOI 10.17487/RFC 5623,
September 2009, <https://www.rfc-editor.org/info/RFC 5623>.
[RFC 5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
Sprecher, N., and S. Ueno, "Requirements of an MPLS
Transport Profile", RFC 5654, DOI 10.17487/RFC 5654,
September 2009, <https://www.rfc-editor.org/info/RFC 5654>.
[RFC 7138] Ceccarelli, D., Ed., Zhang, F., Belotti, S., Rao, R., and
J. Drake, "Traffic Engineering Extensions to OSPF for
GMPLS Control of Evolving G.709 Optical Transport
Networks", RFC 7138, DOI 10.17487/RFC 7138, March 2014,
<https://www.rfc-editor.org/info/RFC 7138>.
[RFC 7139] Zhang, F., Ed., Zhang, G., Belotti, S., Ceccarelli, D.,
and K. Pithewan, "GMPLS Signaling Extensions for Control
of Evolving G.709 Optical Transport Networks", RFC 7139,
DOI 10.17487/RFC 7139, March 2014,
<https://www.rfc-editor.org/info/RFC 7139>.
[RFC 7271] Ryoo, J., Ed., Gray, E., Ed., van Helvoort, H.,
D'Alessandro, A., Cheung, T., and E. Osborne, "MPLS
Transport Profile (MPLS-TP) Linear Protection to Match the
Operational Expectations of Synchronous Digital Hierarchy,
Optical Transport Network, and Ethernet Transport Network
Operators", RFC 7271, DOI 10.17487/RFC 7271, June 2014,
<https://www.rfc-editor.org/info/RFC 7271>.
[RFC 7688] Lee, Y., Ed. and G. Bernstein, Ed., "GMPLS OSPF
Enhancement for Signal and Network Element Compatibility
for Wavelength Switched Optical Networks", RFC 7688,
DOI 10.17487/RFC 7688, November 2015,
<https://www.rfc-editor.org/info/RFC 7688>.
[RFC 7689] Bernstein, G., Ed., Xu, S., Lee, Y., Ed., Martinelli, G.,
and H. Harai, "Signaling Extensions for Wavelength
Switched Optical Networks", RFC 7689,
DOI 10.17487/RFC 7689, November 2015,
<https://www.rfc-editor.org/info/RFC 7689>.
[RFC 7792] Zhang, F., Zhang, X., Farrel, A., Gonzalez de Dios, O.,
and D. Ceccarelli, "RSVP-TE Signaling Extensions in
Support of Flexi-Grid Dense Wavelength Division
Multiplexing (DWDM) Networks", RFC 7792,
DOI 10.17487/RFC 7792, March 2016,
<https://www.rfc-editor.org/info/RFC 7792>.
[RFC 8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC 8231, September 2017,
<https://www.rfc-editor.org/info/RFC 8231>.
[RFC 8234] Ryoo, J., Cheung, T., van Helvoort, H., Busi, I., and G.
Wen, "Updates to MPLS Transport Profile (MPLS-TP) Linear
Protection in Automatic Protection Switching (APS) Mode",
RFC 8234, DOI 10.17487/RFC 8234, August 2017,
<https://www.rfc-editor.org/info/RFC 8234>.
[RFC 8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for PCE-Initiated LSP Setup in a Stateful PCE
Model", RFC 8281, DOI 10.17487/RFC 8281, December 2017,
<https://www.rfc-editor.org/info/RFC 8281>.
[RFC 8345] Clemm, A., Medved, J., Varga, R., Bahadur, N.,
Ananthakrishnan, H., and X. Liu, "A YANG Data Model for
Network Topologies", RFC 8345, DOI 10.17487/RFC 8345, March
2018, <https://www.rfc-editor.org/info/RFC 8345>.
[RFC 8363] Zhang, X., Zheng, H., Casellas, R., Gonzalez de Dios, O.,
and D. Ceccarelli, "GMPLS OSPF-TE Extensions in Support of
Flexi-Grid Dense Wavelength Division Multiplexing (DWDM)
Networks", RFC 8363, DOI 10.17487/RFC 8363, May 2018,
<https://www.rfc-editor.org/info/RFC 8363>.
[SPCE-ID] Dugeon, O., Meuric, J., Lee, Y., and D. Ceccarelli, "PCEP
Extension for Stateful Inter-Domain Tunnels", Work in
Progress, Internet-Draft, draft-ietf-pce-stateful-
interdomain-07, 3 March 2025,
<https://datatracker.ietf.org/doc/html/draft-ietf-pce-
stateful-interdomain-07>.
[YANG-TE] Saad, T., Gandhi, R., Liu, X., Beeram, V. P., and I.
Bryskin, "A YANG Data Model for Traffic Engineering
Tunnels, Label Switched Paths and Interfaces", Work in
Progress, Internet-Draft, draft-ietf-teas-yang-te-37, 9
October 2024, <https://datatracker.ietf.org/doc/html/
draft-ietf-teas-yang-te-37>.
Acknowledgements
The authors would like to thank Jim Guichard, Area Director of IETF
Routing Area; Vishnu Pavan Beeram, Chair of TEAS WG; Jia He and
Stewart Bryant, RTGDIR reviewers; Thomas Fossati, Gen-ART reviewer;
Yingzhen Qu, OPSDIR reviewer; David Mandelberg, SECDIR reviewer;
David Dong, IANA Services Sr. Specialist; and Éric Vyncke and Murray
Kucherawy, IESG reviewers for their reviews and comments on this
document.
Contributors
Xianlong Luo
Huawei Technologies
G1, Huawei Xiliu Beipo Village, Songshan Lake
Dongguan
Guangdong, 523808
China
Email: luoxianlong@huawei.com
Sergio Belotti
Nokia
Email: sergio.belotti@nokia.com
Authors' Addresses
Haomian Zheng
Huawei Technologies
H1, Huawei Xiliu Beipo Village, Songshan Lake
Dongguan
Guangdong, 523808
China
Email: zhenghaomian@huawei.com
Yi Lin
Huawei Technologies
H1, Huawei Xiliu Beipo Village, Songshan Lake
Dongguan
Guangdong, 523808
China
Email: yi.lin@huawei.com
Yang Zhao
China Mobile
Email: zhaoyangyjy@chinamobile.com
Yunbin Xu
CAICT
Email: xuyunbin@caict.ac.cn
Dieter Beller
Nokia
Email: Dieter.Beller@nokia.com
RFC TOTAL SIZE: 79946 bytes
PUBLICATION DATE: Tuesday, March 4th, 2025
LEGAL RIGHTS: The IETF Trust (see BCP 78)
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