rfc9791v1.txt   rfc9791.txt 
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1.1. Terminology 1.1. Terminology
The following terminology is used in the document: The following terminology is used in the document:
RFC 9543 Network Slice: RFC 9543 Network Slice:
Interpreted as defined in [RFC9543]. This document uses "network Interpreted as defined in [RFC9543]. This document uses "network
slice" interchangeably as a shorter version of the term "RFC 9543 slice" interchangeably as a shorter version of the term "RFC 9543
Network Slice". Network Slice".
MPLS Ancillary Data: MPLS Ancillary Data (also referred to in this document as
"ancillary data"):
Data that can be classified as: Data that can be classified as:
* residing within the MPLS label stack (referred to as "in-stack * residing within the MPLS label stack (referred to as "in-stack
data"), and data"), and
* residing after the Bottom of Stack (BoS) (referred to as "post- * residing after the Bottom of Stack (BoS) (referred to as "post-
stack data"). stack data").
1.2. Abbreviations 1.2. Abbreviations
MNA: MPLS Network Action AMM: Alternative Marking Method
DEX: Direct Export
I2E: Ingress to Edge BoS: Bottom of Stack
HbH: Hop by Hop DEX: Direct Export
PW: Pseudowire eSPL: extended Special-Purpose Label
BoS: Bottom of Stack FRR: Fast Reroute
ToS: Top of Stack G-ACh: Generic Associated Channel
NSH: Network Service Header HbH: Hop by Hop
FRR: Fast Reroute I2E: Ingress to Egress
IOAM: In situ Operations, Administration, and Maintenance IOAM: In situ Operations, Administration, and Maintenance
G-ACh: Generic Associated Channel
LSP: Label Switched Path LSP: Label Switched Path
LSR: Label Switching Router LSR: Label Switching Router
MNA: MPLS Network Action
NRP: Network Resource Partition NRP: Network Resource Partition
SPL: Special-Purpose Label NSH: Network Service Header
eSPL: extended Special-Purpose Label PW: Pseudowire
AMM: Alternative Marking Method SPL: Special-Purpose Label
ToS: Top of Stack
2. Use Cases 2. Use Cases
2.1. No Further Fast Reroute 2.1. No Further Fast Reroute
MPLS Fast Reroute [RFC4090] [RFC5286] [RFC7490] [SR-TI-LFA] is a MPLS Fast Reroute [RFC4090] [RFC5286] [RFC7490] [SR-TI-LFA] is a
useful and widely deployed tool for minimizing packet loss in the useful and widely deployed tool for minimizing packet loss in the
case of a link or node failure. case of a link or node failure.
Several cases exist where, once a Fast Reroute (FRR) has taken place Several cases exist where, once a Fast Reroute (FRR) has taken place
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the operational state and telemetry information collected on the LSR the operational state and telemetry information collected on the LSR
may be transported using MNA techniques. may be transported using MNA techniques.
2.2.1. In Situ OAM 2.2.1. In Situ OAM
In situ Operations, Administration, and Maintenance (IOAM), defined In situ Operations, Administration, and Maintenance (IOAM), defined
in [RFC9197] and [RFC9326], might be used to collect operational and in [RFC9197] and [RFC9326], might be used to collect operational and
telemetry information while a packet traverses a particular path in a telemetry information while a packet traverses a particular path in a
network domain. network domain.
IOAM can run in two modes: Ingress to Edge (I2E) and Hop by Hop IOAM can run in two modes: Ingress to Egress (I2E) and Hop by Hop
(HbH). In I2E mode, only the encapsulating and decapsulating nodes (HbH). In I2E mode, only the encapsulating and decapsulating nodes
will process IOAM data fields. In HbH mode, the encapsulating and will process IOAM data fields. In HbH mode, the encapsulating and
decapsulating nodes and intermediate IOAM-capable nodes process IOAM decapsulating nodes and intermediate IOAM-capable nodes process IOAM
data fields. The IOAM data fields, defined in [RFC9197], can be used data fields. The IOAM data fields, defined in [RFC9197], can be used
to derive the operational state of the network experienced by the to derive the operational state of the network experienced by the
packet with the IOAM Header that traversed the path through the IOAM packet with the IOAM Header that traversed the path through the IOAM
domain. domain.
Several IOAM Option-Types have been defined: Several IOAM Option-Types have been defined:
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treatments. treatments.
MNA technologies can signal actions for MPLS packets and carry data MNA technologies can signal actions for MPLS packets and carry data
essential for these actions. For example, MNA can carry the NRP essential for these actions. For example, MNA can carry the NRP
Selector [NS-IP-MPLS] in MPLS packets. Selector [NS-IP-MPLS] in MPLS packets.
2.4. NSH-Based Service Function Chaining 2.4. NSH-Based Service Function Chaining
[RFC8595] describes how Service Function Chaining can be realized in [RFC8595] describes how Service Function Chaining can be realized in
an MPLS network by emulating the Network Service Header (NSH) an MPLS network by emulating the Network Service Header (NSH)
[RFC8300] using only MPLS label stack elements. [RFC8300] using only MPLS label stack entries.
The approach in [RFC8595] introduces some limitations, which are The approach in [RFC8595] introduces some limitations, which are
discussed in [SFP-VERIF]. However, the approach can benefit from the discussed in [SFP-VERIF]. However, the approach can benefit from the
MNA framework introduced in [RFC9789]. MNA framework introduced in [RFC9789].
MNA can be used to extend NSH emulation using MPLS labels [RFC8595] MNA can be used to extend NSH emulation using MPLS labels [RFC8595]
to support the functionality of NSH Context Headers, whether fixed or to support the functionality of NSH Context Headers, whether fixed or
variable length. For example, MNA could support Flow ID [RFC9263] variable length. For example, MNA could support Flow ID [RFC9263]
that may be used for load-balancing among Service Function Forwarders that may be used for load-balancing among Service Function Forwarders
and/or the Service Functions within the same Service Function Path. and/or the Service Functions within the same Service Function Path.
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the presence of the PW CW. the presence of the PW CW.
In addition to providing connectivity to user traffic, MPLS may also In addition to providing connectivity to user traffic, MPLS may also
transport OAM data (e.g., over MPLS Generic Associated Channels transport OAM data (e.g., over MPLS Generic Associated Channels
(G-AChs) [RFC5586]). In this case, the first nibble of the data that (G-AChs) [RFC5586]). In this case, the first nibble of the data that
immediately follows the MPLS BoS is set to 0b0001. It indicates the immediately follows the MPLS BoS is set to 0b0001. It indicates the
presence of a control channel associated with a PW, LSP, or section. presence of a control channel associated with a PW, LSP, or section.
Bit Index Explicit Replication (BIER) [RFC8296] traffic can also be Bit Index Explicit Replication (BIER) [RFC8296] traffic can also be
encapsulated over MPLS. In this case, BIER has defined 0b0101 as the encapsulated over MPLS. In this case, BIER has defined 0b0101 as the
value for the first nibble of the data that immediately follows the value for the first nibble of the data that immediately appears after
bottom of the label stack for any BIER-encapsulated packet over MPLS. the BoS for any BIER-encapsulated packet over MPLS.
For PWs, the G-ACh [RFC7212] uses the first four bits of the PW For PWs, the G-ACh [RFC7212] uses the first four bits of the PW
control word to provide the initial discrimination between data control word to provide the initial discrimination between data
packets and packets belonging to the associated channel, as described packets and packets belonging to the associated channel, as described
in [RFC4385]. in [RFC4385].
MPLS can be used as the data plane for Deterministic Networking MPLS can be used as the data plane for Deterministic Networking
(DetNet) [RFC8655]. The DetNet sub-layers, forwarding, and service (DetNet) [RFC8655]. The DetNet sub-layers, forwarding, and service
are realized using the MPLS label stack, the DetNet control word are realized using the MPLS label stack, the DetNet control word
[RFC8964], and the DetNet Associated Channel Header [RFC9546]. [RFC8964], and the DetNet Associated Channel Header [RFC9546].
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Objectives (SLOs) are being met by the network provider. In this Objectives (SLOs) are being met by the network provider. In this
case, IOAM can collect key performance measurement parameters of a case, IOAM can collect key performance measurement parameters of a
network slice traffic flow as it traverses the transport network. network slice traffic flow as it traverses the transport network.
5. IANA Considerations 5. IANA Considerations
This document has no IANA actions. This document has no IANA actions.
6. Security Considerations 6. Security Considerations
Section 7 of the MNA framework [RFC9789] outlines security Section 7 of [RFC9789] outlines security considerations for documents
considerations for documents that do not specify protocols. The that do not specify protocols. The authors have verified that these
authors have verified that these considerations are fully applicable considerations are fully applicable to this document.
to this document.
In-depth security analysis for each specific use case is beyond the In-depth security analysis for each specific use case is beyond the
scope of this document and will be addressed in future solution scope of this document and will be addressed in future solution
documents. It is strongly recommended that these solution documents documents. It is strongly recommended that these solution documents
undergo review by a security expert early in their development, undergo review by a security expert early in their development,
ideally during the Working Group Last Call phase. ideally during the Working Group Last Call phase.
7. References 7. References
7.1. Normative References 7.1. Normative References
[RFC9789] Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS [RFC9789] Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS
Network Action (MNA) Framework", RFC 9789, Network Actions (MNAs) Framework", RFC 9789,
DOI 10.17487/RFC9789, May 2025, DOI 10.17487/RFC9789, May 2025,
<https://www.rfc-editor.org/info/rfc9789>. <https://www.rfc-editor.org/info/rfc9789>.
7.2. Informative References 7.2. Informative References
[GDF] Zhang, Z., Bonica, R., Kompella, K., and G. Mirsky, [GDF] Zhang, Z., Bonica, R., Kompella, K., and G. Mirsky,
"Generic Delivery Functions", Work in Progress, Internet- "Generic Delivery Functions", Work in Progress, Internet-
Draft, draft-zzhang-intarea-generic-delivery-functions-03, Draft, draft-zzhang-intarea-generic-delivery-functions-03,
11 July 2022, <https://datatracker.ietf.org/doc/html/ 11 July 2022, <https://datatracker.ietf.org/doc/html/
draft-zzhang-intarea-generic-delivery-functions-03>. draft-zzhang-intarea-generic-delivery-functions-03>.
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