rfc9994.original   rfc9994.txt 
MPLS Working Group J. Rajamanickam, Ed. Internet Engineering Task Force (IETF) J. Rajamanickam, Ed.
Internet-Draft R. Gandhi, Ed. Request for Comments: 9994 R. Gandhi, Ed.
Intended status: Standards Track Cisco Systems, Inc. Category: Standards Track Cisco Systems, Inc.
Expires: 28 August 2026 R. Zigler ISSN: 2070-1721 R. Zigler
Broadcom Broadcom
H. Song H. Song
Futurewei Technologies Futurewei Technologies
K. Kompella K. Kompella
Juniper Networks Juniper Networks
24 February 2026 May 2026
MPLS Network Action (MNA) Sub-Stack Specification including In-Stack MPLS Network Action (MNA) Sub-Stack Specification Including In-Stack
Network Actions and Data Network Actions and Data
draft-ietf-mpls-mna-hdr-21
Abstract Abstract
This document specifies the MPLS Network Actions (MNA) sub-stack for This document specifies the MPLS Network Action (MNA) sub-stack for
carrying Network Actions and Ancillary Data in the MPLS label stack. carrying Network Actions and Ancillary Data (AD) in the MPLS label
MNA can be used to influence packet forwarding decisions, carry stack. MNA can be used to influence packet-forwarding decisions,
additional Operations, Administration, and Maintenance information in carry additional Operations, Administration, and Maintenance (OAM)
the MPLS packet or perform user-defined operations. information in the MPLS packet, or perform user-defined operations.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This is an Internet Standards Track document.
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months This document is a product of the Internet Engineering Task Force
and may be updated, replaced, or obsoleted by other documents at any (IETF). It represents the consensus of the IETF community. It has
time. It is inappropriate to use Internet-Drafts as reference received public review and has been approved for publication by the
material or to cite them other than as "work in progress." Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
This Internet-Draft will expire on 28 August 2026. 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/rfc9994.
Copyright Notice Copyright Notice
Copyright (c) 2026 IETF Trust and the persons identified as the Copyright (c) 2026 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction
2. Conventions Used in This Document . . . . . . . . . . . . . . 3 2. Conventions Used in This Document
2.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 2.1. Requirements Language
2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 4 2.2. Abbreviations
2.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 2.3. Terminology
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Overview
4. Label Stack Entry Formats . . . . . . . . . . . . . . . . . . 7 4. Label Stack Entry Formats
4.1. LSE Format A: The MNA Sub-Stack Indicator . . . . . . . . 7 4.1. LSE Format A: The MNA Sub-Stack Indicator
4.2. LSE Format B: The initial opcode . . . . . . . . . . . . 7 4.2. LSE Format B: The Initial Opcode
4.3. LSE Format C: Subsequent opcodes . . . . . . . . . . . . 8 4.3. LSE Format C: Subsequent Opcodes
4.4. LSE Format D: Additional Data . . . . . . . . . . . . . . 9 4.4. LSE Format D: Additional Data
5. The MNA Sub-Stack . . . . . . . . . . . . . . . . . . . . . . 9 5. The MNA Sub-Stack
5.1. Opcodes . . . . . . . . . . . . . . . . . . . . . . . . . 10 5.1. Opcodes
5.2. Ancillary Data . . . . . . . . . . . . . . . . . . . . . 10 5.2. Ancillary Data
5.3. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5.3. Scope
5.4. Unknown Network Action Handling . . . . . . . . . . . . . 12 5.4. Unknown Network Action Handling
5.5. Ordering . . . . . . . . . . . . . . . . . . . . . . . . 13 5.5. Ordering
6. Special Opcodes . . . . . . . . . . . . . . . . . . . . . . . 13 6. Special Opcodes
6.1. bSPL Protection . . . . . . . . . . . . . . . . . . . . . 13 6.1. bSPL Protection
6.2. Flag-Based NAIs without AD . . . . . . . . . . . . . . . 13 6.2. Flag-Based NAIs Without AD
6.3. No-Operation Opcode . . . . . . . . . . . . . . . . . . . 14 6.3. No-Operation Opcode
6.4. Extension Opcode . . . . . . . . . . . . . . . . . . . . 14 6.4. Extension Opcode
7. NAS placement in the Label Stack . . . . . . . . . . . . . . 14 7. NAS Placement in the Label Stack
7.1. Actions when Pushing Labels . . . . . . . . . . . . . . . 15 7.1. Actions When Pushing Labels
8. Node Capability Signaling . . . . . . . . . . . . . . . . . . 16 8. Node Capability Signaling
9. Processing the Network Action Sub-Stack . . . . . . . . . . . 16 9. Processing the Network Action Sub-Stack
9.1. Encapsulating Node Responsibilities . . . . . . . . . . . 16 9.1. Encapsulating Node Responsibilities
9.2. Transit Node Responsibilities . . . . . . . . . . . . . . 17 9.2. Transit Node Responsibilities
9.3. Penultimate Node Responsibilities . . . . . . . . . . . . 17 9.3. Penultimate Node Responsibilities
9.4. Egress Node Responsibilities . . . . . . . . . . . . . . 17 9.4. Egress Node Responsibilities
10. Network Action Indicator Opcode Definition . . . . . . . . . 17 10. Network Action Indicator Opcode Definition
11. Implementation Status . . . . . . . . . . . . . . . . . . . . 18 11. Security Considerations
11.1. University of Tuebingen Implementation . . . . . . . . . 18 12. Operational Considerations
12. Security Considerations . . . . . . . . . . . . . . . . . . . 19 12.1. Manageability Considerations
13. Operational Considerations . . . . . . . . . . . . . . . . . 20 12.2. Performance and Scale Considerations
13.1. Manageability Considerations . . . . . . . . . . . . . . 20 12.3. Backward Compatibility
13.2. Performance and Scale Considerations . . . . . . . . . . 20 13. IANA Considerations
13.3. Backward Compatibility . . . . . . . . . . . . . . . . . 20 13.1. MNA bSPL Label
14. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 22 13.2. MPLS Network Actions Parameters
14.1. MNA bSPL Label . . . . . . . . . . . . . . . . . . . . . 22 13.2.1. Network Action Flags Without Ancillary Data
14.2. MPLS Network Actions Parameters . . . . . . . . . . . . 22 13.2.2. Network Action Opcodes
14.3. Network Action Flags Without Ancillary Data . . . . . . 22 14. References
14.4. Network Action Opcodes . . . . . . . . . . . . . . . . . 23 14.1. Normative References
15. References . . . . . . . . . . . . . . . . . . . . . . . . . 24 14.2. Informative References
15.1. Normative References . . . . . . . . . . . . . . . . . . 24 Appendix A. Examples
15.2. Informative References . . . . . . . . . . . . . . . . . 25 A.1. Network Action Encoding Examples
Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 26 A.1.1. Network Action Flags Without AD
A.1. Network Action Encoding Examples . . . . . . . . . . . . 26 A.1.2. Network Action Opcode with AD
A.1.1. Network Action Flags without AD . . . . . . . . . . . 26 A.1.3. Network Action Opcode with More AD with Format-B
A.1.2. Network Action Opcode with AD . . . . . . . . . . . . 27 A.1.4. Network Action Opcode with More AD with Format C
A.1.3. Network Action Opcode with more AD with Format-B . . 28 A.2. Network Action Processing Order
A.1.4. Network Action Opcode with more AD with Format C . . 29 A.2.1. Network Action Processing Order
A.2. Network Action Processing Order . . . . . . . . . . . . . 29 Acknowledgments
A.2.1. Network Action Processing Order . . . . . . . . . . . 29 Contributors
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 31 Authors' Addresses
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 31
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
1. Introduction 1. Introduction
[RFC3032] defines the encoding of the MPLS label stack, the basic [RFC3032] defines the encoding of the MPLS label stack, the basic
structure used to define a forwarding path. There are applications structure used to define a forwarding path. There are applications
that require MPLS packets to perform special network actions and that require MPLS packets to perform special network actions and
carry optional Ancillary Data (AD) that can affect the packet carry optional Ancillary Data (AD) that can affect the packet-
forwarding decision or trigger Operations, Administration, and forwarding decision or trigger Operations, Administration, and
Maintenance (OAM) logging, for example as described in [RFC9791]. Maintenance (OAM) logging, for example, as described in [RFC9791].
Ancillary Data can be used to carry additional information, for AD can be used to carry additional information, for example, for
network slice purpose, as an example [RFC9791]. network slice purposes (see [RFC9791]).
The requirements for In-stack network action and In-stack data (ISD) The requirements for In-stack network action and In-Stack Data (ISD)
are described in [RFC9613]. are described in [RFC9613].
This document defines the syntax and semantics of network actions and This document defines the syntax and semantics of network actions and
ancillary data encoded in an MPLS label stack. In-stack actions and AD encoded in an MPLS label stack. In-stack actions and AD are
ancillary data are contained in a Network Action Sub-Stack (NAS), contained in a Network Action Sub-Stack (NAS), which is recognized by
which is recognized by a new base Special Purpose Label (bSPL). This a new base Special-Purpose Label (bSPL). This document follows the
document follows the framework specified in [RFC9789]. framework specified in [RFC9789].
2. Conventions Used in This Document 2. Conventions Used in This Document
2.1. Requirements Language 2.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in BCP 14, [RFC2119] "OPTIONAL" in this document are to be interpreted as described in
[RFC8174] when, and only when, they appear in all capitals, as shown BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
here. capitals, as shown here.
2.2. Abbreviations 2.2. Abbreviations
The abbrevations defined in [RFC9789] and [RFC9613] are used in this The abbreviations defined in [RFC9789] and [RFC9613] are used in this
document. document.
+==============+=============================+===============+ +==============+=============================+===============+
| Abbreviation | Meaning | Reference | | Abbreviation | Meaning | Reference |
+==============+=============================+===============+ +==============+=============================+===============+
| AD | Ancillary Data | [RFC9613] | | AD | Ancillary Data | [RFC9613] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| bSPL | Base Special Purpose Label | [RFC9017] | | bSPL | base Special Purpose Label | [RFC9017] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| BOS | Bottom Of Stack | [RFC9789] | | BoS | Bottom of Stack | [RFC9789] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| ECMP | Equal Cost Multi-Path | [RFC6790] | | ECMP | Equal-Cost Multipath | [RFC6790] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| HBH | Hop-By-Hop Scope | [RFC9789] | | HbH | Hop-by-Hop | [RFC9789] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| I2E | Ingress-To-Egress Scope | [RFC9789] | | I2E | Ingress to Egress | [RFC9789] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| IHS | I2E, HBH, or Select Scope | [RFC9789], | | IHS | I2E, HbH, or Select | [RFC9789], |
| | | This document | | | | This document |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| ISD | In-stack Data | [RFC9613] | | ISD | In-Stack Data | [RFC9613] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| LSE | Label Stack Entry | [RFC9789] | | LSE | Label Stack Entry | [RFC9789] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| LSP | Label Switched Path | [RFC3031] | | LSP | Label Switched Path | [RFC3031] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| MNA | MPLS Network Actions | [RFC9789] | | MNA | MPLS Network Action | [RFC9789] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| NAI | Network Action Indicator | [RFC9613] | | NAI | Network Action Indicator | [RFC9613] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| NAL | Network Action Length | This document | | NAL | Network Action Length | This document |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| NAS | Network Action Sub-Stack | [RFC9789] | | NAS | Network Action Sub-Stack | [RFC9789] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| NASI | Network Action Sub-Stack | This document | | NASI | Network Action Sub-Stack | This document |
| | Indicator | | | | Indicator | |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| NASL | Network Action Sub-Stack | This document | | NASL | Network Action Sub-Stack | This document |
| | Length | | | | Length | |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| OAM | Operations, Administration, | [RFC6291] | | OAM | Operations, Administration, | [RFC6291] |
| | and Maintenance | | | | and Maintenance | |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| RLD | Readable Label Depth | [RFC9789] | | RLD | Readable Label Depth | [RFC9789] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| TC | Traffic Class | [RFC5462] | | TC | Traffic Class | [RFC5462] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
| TTL | Time To Live | [RFC3032] | | TTL | Time to Live | [RFC3032] |
+--------------+-----------------------------+---------------+ +--------------+-----------------------------+---------------+
Table 1: Abbreviations Table 1: Abbreviations
2.3. Terminology 2.3. Terminology
The following terms are used in this document. The following terms are used in this document.
MPLS egress node: MPLS Egress Node:
An MPLS edge node in its role in handling traffic as it leaves an An MPLS edge node in its role in handling traffic as it leaves an
MPLS domain [RFC3031]. MPLS domain [RFC3031].
MPLS ingress node: MPLS Ingress Node:
An MPLS edge node in its role in handling traffic as it enters an An MPLS edge node in its role in handling traffic as it enters an
MPLS domain [RFC3031]. MPLS domain [RFC3031].
MPLS domain: MPLS Domain:
A contiguous set of nodes which operate MPLS routing and A contiguous set of nodes that operate MPLS routing and forwarding
forwarding and which are also in one Routing or Administrative and that are also in one Routing or Administrative Domain
Domain [RFC3031]. [RFC3031].
Encapsulating Node: Encapsulating Node:
An encapsulating node is a node that adds an NAS to the label A node that adds a NAS to the label stack.
stack.
3. Overview 3. Overview
The MPLS Network Action Sub-Stack is a set of Label Stack Entries The MPLS NAS is a set of Label Stack Entries (LSEs) that appear as
(LSEs) that appear as part of an MPLS label stack and serve to encode part of an MPLS label stack and serve to encode information about the
information about the network actions that should be invoked for the network actions that should be invoked for the packet. Multiple
packet. Multiple NASes may appear in a label stack and be placed as NASes may appear in a label stack and be placed as described in
described in Section 5. Section 5.
This document specifies how network actions and their optional This document specifies how network actions and their optional AD are
ancillary data are encoded as part of a NAS as a stack of LSEs. encoded as part of a NAS as a stack of LSEs. Mechanisms that allow
Mechanisms that allow sharing of ancillary data (AD) between multiple sharing of AD between multiple network actions encoded in the same
network actions encoded in the same NAS can be described in other NAS can be described in other documents and do not rely on any
documents and do not rely on any explicit provision in the encodings explicit provision in the encodings described in this document.
described in this document.
This document defines new LSE formats beyond [RFC3032] that define This document defines new LSE formats beyond those in [RFC3032] that
behaviors or are processed in different ways to MPLS labels as define behaviors or are processed in different ways than MPLS labels
defined in [RFC3031]. Three new LSE formats are defined to carry 7 as defined in [RFC3031]. Three new LSE formats are defined to carry
bits of network action opcodes and varying amounts of opcode-specific 7 bits of network action opcodes and varying amounts of opcode-
ancillary data. Specifically, Format-B LSE carries up to 13 bits of specific AD. Specifically, Format-B LSE carries up to 13 bits of AD
ancillary data in an LSE and Format-C LSE carries up to 20 bits of in an LSE. Format-C LSE carries up to 20 bits of AD in an LSE.
ancillary data in an LSE. Format-D LSE is used when additional Format-D LSE is used when additional AD is needed by the opcodes in
ancillary data is needed by the opcodes in Format-B or Format-C LSEs. Format-B or Format-C LSEs.
As shown in an example in the Figure 1, the first LSE in an MNA Sub- As shown in Figure 1, the first LSE in an MNA Sub-Stack uses Format-
Stack uses Format-A. The second LSE uses Format-B and is followed by A. The second LSE uses Format-B and is followed by a Format-D LSE to
a Format-D LSE to carry additional data. Next, there may be a carry additional data. Next, there may be a Format-C LSE for an
Format-C LSE for an additional network action followed by another additional network action followed by another Format-D LSE for
Format-D LSE for additional data. You can add more Format-C and additional data. Additional Format-C and Format-D LSEs may be added
Format-D LSEs as needed for additional network actions and data. as needed for additional network actions and data.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--
| MNA-Label=bSPL | TC |S| TTL |A | MNA-Label=bSPL | TC |S| TTL |A
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--
| Opcode | 13-bit Data |R|IHS|S| NASL |U| NAL |B | Opcode | 13-bit Data |R|IHS|S| NASL |U| NAL |B
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--
|1| 22-bit Data |S| 8-bit Data |D* |1| 22-bit Data |S| 8-bit Data |D*
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--
| Opcode | 16-bit Data |S|4b Data|U| NAL |C | Opcode | 16-bit Data |S|4b Data|U| NAL |C
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--
|1| 22-bit Data |S| 8-bit Data |D* |1| 22-bit Data |S| 8-bit Data |D*
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--
| Opcode | 16-bit Data |S|4b Data|U| NAL |C | Opcode | 16-bit Data |S|4b Data|U| NAL |C
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--
~ ~ ~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-- +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+--
Legend: * Format-D LSE presence indicated by NAL greater than one * Format-D LSE presence indicated by NAL greater than one
Figure 1: An MNA Sub-Stack Encoding Example Figure 1: An MNA Sub-Stack Encoding Example
4. Label Stack Entry Formats 4. Label Stack Entry Formats
The NAS uses a variety of different formats of LSEs for different The NAS uses a variety of different formats of LSEs for different
purposes. This section describes the syntax of the various formats purposes. This section describes the syntax of the various formats
while the overall structure of the NAS and the semantics of the while the overall structure of the NAS and the semantics of the
various LSEs are described in the sections below. various LSEs are described in the sections below.
4.1. LSE Format A: The MNA Sub-Stack Indicator 4.1. LSE Format A: The MNA Sub-Stack Indicator
LSE Format A is an LSE as described in [RFC3032] and [RFC5462]. The LSE Format A is an LSE as described in [RFC3032] and [RFC5462]. The
label value is an IANA-assigned value (TBA) for the MNA bSPL label label value is 4 for the MNA bSPL label from the "Base Special-
from the "Base Special-Purpose MPLS Label Values" registry to Purpose MPLS Label Values" IANA registry (see Section 13.1) to
indicate the presence of MNA in the packet and the beginning of an indicate the presence of an MNA in the packet and the beginning of an
MNA Sub-Stack in the label stack. MNA Sub-Stack in the label stack.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MNA-Label=bSPL | TC |S| TTL | | MNA-Label=bSPL | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: LSE Format A: The MNA Sub-Stack Indicator Figure 2: LSE Format A: The MNA Sub-Stack Indicator
* S (1 bit): The Bottom of Stack [RFC3032]. MUST be set to 0 on S (1 bit): The BoS [RFC3032]. MUST be set to 0 on transmitted
transmitted packets. If a packet is received with an LSE packets. If a packet is received with an LSE containing the bSPL
containing the bSPL (value TBA) and with S bit set to 1, then the (4) and with S bit set to 1, then the packet MUST be dropped.
packet MUST be dropped.
4.2. LSE Format B: The initial opcode 4.2. LSE Format B: The Initial Opcode
LSE Format B is used to encode the first opcode in the NAS, plus a LSE Format B is used to encode the first opcode in the NAS, plus a
number of other fields about the NAS. This LSE can carry up to 13 number of other fields about the NAS. This LSE can carry up to 13
bits of ancillary data. bits of AD.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode | 13-bit Data |R|IHS|S| NASL |U| NAL | | Opcode | 13-bit Data |R|IHS|S| NASL |U| NAL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: LSE Format B: The initial opcode Figure 3: LSE Format B: The Initial Opcode
* Opcode (7 bits): The operation code for this LSE. See Opcode (7 bits): The operation code for this LSE. See Section 5.1.
Section 5.1.
* Data (13 bits): Opcode-specific ancillary data. Data (13 bits): Opcode-specific AD.
* R (1 bit): Reserved. This bit MUST be set to zero on transmission R (1 bit): Reserved. This bit MUST be set to zero on transmission
and ignored upon receipt. and ignored upon receipt.
* IHS (2 bits): The scope of all the network actions in this NAS. IHS (2 bits): The scope of all the network actions in this NAS. See
See Section 5.3. Section 5.3.
* S (1 bit): The Bottom of Stack [RFC3032]. If NASL value is non- S (1 bit): The BoS [RFC3032]. If the NASL value is non-zero, then
zero, then S bit MUST be 0. If a packet is received with S bit the S bit MUST be 0. If a packet is received with the S bit set
set to 1 and a non-zero NASL value, then the packet MUST be to 1 and a non-zero NASL value, then the packet MUST be dropped.
dropped. The encapsulating node MUST ensure that the S bit is set The encapsulating node MUST ensure that the S bit is set to 1 only
to 1 only in the Last LSE in the MPLS header. in the Last LSE in the MPLS header.
* NASL (4 bits): The Network Action Sub-Stack Length (NASL). The NASL (4 bits): The Network Action Sub-Stack Length. The number of
number of Format C and Format D LSEs in the NAS, i.e., not Format C and Format D LSEs in the NAS, i.e., not including the
including the leading Format A LSE and the Format B LSE. leading Format A LSE and the Format B LSE.
* U (1 bit): Unknown Network Action Handling. See Section 5.4. U (1 bit): Unknown Network Action Handling. See Section 5.4.
* NAL (3 bits): Network Action Length. The number of LSEs of NAL (3 bits): Network Action Length. The number of LSEs of
additional data, encoded in Format D LSEs (Section 4.4) following additional data, encoded in Format D LSEs (Section 4.4), following
this Format B LSE. The NAL value MUST be less than or equal to this Format B LSE. The NAL value MUST be less than or equal to
the NASL value in the Format B LSE, if not the packet MUST be the NASL value in the Format B LSE. If not, the packet MUST be
dropped. A Format C LSE would be following when the NAL value is dropped. A Format C LSE would be following when the NAL value is
less than the NASL value. less than the NASL value.
4.3. LSE Format C: Subsequent opcodes 4.3. LSE Format C: Subsequent Opcodes
LSE Format C is used to encode the subsequent opcodes in the NAS. LSE Format C is used to encode the subsequent opcodes in the NAS.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode | 16-bit Data |S|4b Data|U| NAL | | Opcode | 16-bit Data |S|4b Data|U| NAL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: LSE Format C: Subsequent opcodes Figure 4: LSE Format C: Subsequent Opcodes
* Opcode (7 bits): The operation code for this LSE. See Opcode (7 bits): The operation code for this LSE. See Section 5.1.
Section 5.1.
* Data (16 bits + 4 bits): Opcode-specific ancillary data. Data (16 bits + 4 bits): Opcode-specific AD.
* S (1 bit): The Bottom of Stack [RFC3032]. If NAL value is non- S (1 bit): The BoS [RFC3032]. If the NAL value is non-zero and if
zero and if S bit is set to 1, then the packet MUST be dropped. the S bit is set to 1, then the packet MUST be dropped. If this
If this is not the last LSE in the NAS and if S bit is set to 1 is not the last LSE in the NAS and if the S bit is set to 1, then
then the packet MUST be dropped. The encapsulating node MUST the packet MUST be dropped. The encapsulating node MUST ensure
ensure that the S bit is set to 1 only in the Last LSE. that the S bit is set to 1 only in the Last LSE.
* U (1 bit): Unknown Network Action Handling. See Section 5.4. U (1 bit): Unknown Network Action Handling. See Section 5.4.
* NAL (3 bits): Network Action Length. The number of LSEs of NAL (3 bits): Network Action Length. The number of LSEs of
additional data, encoded in Format D LSEs (Section 4.4) following additional data, encoded in Format D LSEs (Section 4.4) following
this Format C LSE. The NAL value MUST be less than or equal to this Format C LSE. The NAL value MUST be less than or equal to
the NASL value in the Format B LSE, if not the packet MUST be the NASL value in the Format B LSE. If not, the packet MUST be
dropped. dropped.
A Format A and a Format B LSE MUST be present when a Format C LSE is A Format A and a Format B LSE MUST be present when a Format C LSE is
carried in the NAS. carried in the NAS.
4.4. LSE Format D: Additional Data 4.4. LSE Format D: Additional Data
LSE Format D is used to encode additional data that did not fit in LSE Format D is used to encode additional data that did not fit in
the LSE with the preceding opcode. the LSE with the preceding opcode.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| 22-bit Data |S| 8-bit Data | |1| 22-bit Data |S| 8-bit Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: LSE Format D: Additional Data Figure 5: LSE Format D: Additional Data
* 1 (1 bit): The most significant bit MUST be set. This prevents 1 (1 bit): The most significant bit MUST be set. This prevents
legacy implementations from misinterpreting this LSE as containing legacy implementations from misinterpreting this LSE as containing
a special purpose label if the data begins with zeros. a special purpose label if the data begins with zeros.
* S (1 bit): The Bottom of Stack [RFC3032]. If this is not the last S (1 bit): The BoS [RFC3032]. If this is not the last LSE for the
LSE for the Network Action based on the NAL value and if S bit is Network Action based on the NAL value and if the S bit is set to
set to 1 then the packet MUST be dropped. If this is not the last 1, then the packet MUST be dropped. If this is not the last LSE
LSE in the NAS and if S bit is set to 1 then the packet MUST be in the NAS and if the S bit is set to 1, then the packet MUST be
dropped. The encapsulating node MUST ensure that the S bit is set dropped. The encapsulating node MUST ensure that the S bit is set
to 1 only in the Last LSE. to 1 only in the Last LSE.
* Data (22 bits + 8 bits): Opcode-specific ancillary data. Data (22 bits + 8 bits): Opcode-specific AD.
A Format A and a Format B LSE MUST be present when a Format D LSE is A Format A and a Format B LSE MUST be present when a Format D LSE is
carried in the NAS. carried in the NAS.
5. The MNA Sub-Stack 5. The MNA Sub-Stack
The MNA Sub-Stack MUST begin with a Format A LSE (Section 4.1). The The MNA Sub-Stack MUST begin with a Format A LSE (Section 4.1). The
label value of the LSE contains the MNA bSPL (value TBA) to indicate label value of the LSE contains the MNA bSPL (4) to indicate the
the presence of the MNA Sub-Stack. presence of the MNA Sub-Stack.
The TC and TTL values of the Format A LSE retain their semantics as The TC and TTL values of the Format A LSE retain their semantics as
defined in [RFC3032] and [RFC5462]. The TTL and TC values in the defined in [RFC3032] and [RFC5462]. The TTL and TC values in the
Format A LSE are copied from the forwarding label at the top of the Format A LSE are copied from the forwarding label at the top of the
label stack. The penultimate node on the path copies the TTL and TC label stack. The penultimate node on the path copies the TTL and TC
values from the preceding LSE to the next LSE on the label stack, values from the preceding LSE to the next LSE on the label stack,
overwriting the TTL and TC values of the next LSE, as specified in overwriting the TTL and TC values of the next LSE, as specified in
Section 3.5 of [RFC3443] and Section 2.6.3 of [RFC3270] in the Section 3.5 of [RFC3443] and Section 2.6.3 of [RFC3270] in the
Uniform Mode LSPs. If the node performing this copy is not aware of Uniform Mode LSPs. If the node performing this copy is not aware of
MNA, this could overwrite the values in the Format-A LSE of the NAS. MNA, this could overwrite the values in the Format-A LSE of the NAS.
skipping to change at page 10, line 25 skipping to change at line 426
The second LSE in a NAS MUST be a Format B LSE (Section 4.2). This The second LSE in a NAS MUST be a Format B LSE (Section 4.2). This
LSE contains an initial opcode plus additional fields that describe LSE contains an initial opcode plus additional fields that describe
the NAS. the NAS.
The Format B LSE (Section 4.2) could optionally carry additional data The Format B LSE (Section 4.2) could optionally carry additional data
in Format D (Section 4.4) LSEs, up to the length encoded in the LSE's in Format D (Section 4.4) LSEs, up to the length encoded in the LSE's
NAL value. NAL value.
A NAS MAY contain more Format C (Section 4.3) and Format D A NAS MAY contain more Format C (Section 4.3) and Format D
(Section 4.4) LSEs, up to the length encoded in the NASL value. All (Section 4.4) LSEs, up to the length encoded in the NASL value. All
Format D LSEs MUST follow a Format C or B LSE and be included in that Format D LSEs MUST follow a Format C or Format B LSE and be included
LSE's NAL value. in that LSE's NAL value.
5.1. Opcodes 5.1. Opcodes
The opcode is a 7-bit field that indicates the semantics of its LSE. The opcode is a 7-bit field that indicates the semantics of its LSE.
Several opcodes are assigned special semantics (Section 6), others Several opcodes are assigned special semantics (Section 6). Other
act as Network Action Indicators and are assigned through IANA opcodes act as NAIs and are assigned through IANA (see Sections 10
(Section 10 and Section 14.4). and 13.2.2).
5.2. Ancillary Data 5.2. Ancillary Data
The data field carries opcode-specific data that is ancillary data The data field carries opcode-specific data that is AD for a network
for a network action. In the case of opcode 1, the data field action. In the case of opcode 1, the data field carries Flag-Based
carries Flag-Based Network Action Indicators without ancillary data. Network Action Indicators without AD.
The label value (most significant 20 bits) in one or more consecutive The label value (most significant 20 bits) in one or more consecutive
LSEs is commonly used for load balancing data flows in an ECMP LSEs is commonly used for load-balancing data flows in an ECMP
environment. Modifying the first 20 bits in an LSE might alter a environment. Modifying the first 20 bits in an LSE might alter a
packet's path and result in out-of-order delivery of packets packet's path and result in out-of-order delivery of packets
belonging to a given flow. To maintain the stability of deployed belonging to a given flow. To maintain the stability of deployed
services in ECMP environments that rely on label value information services in ECMP environments that rely on label value information
for load-balancing, care must be taken when encoding network action for load-balancing, care must be taken when encoding network action
data in the given LSE. If the network action data may differ among data in the given LSE. If the network action data may differ among
packets in the same flow or change during forwarding across the MPLS packets in the same flow or change during forwarding across the MPLS
network, it MUST NOT be placed in the most significant 20 bits of a network, it MUST NOT be placed in the most significant 20 bits of a
Format B LSE (Section 4.2), a Format C LSE (Section 4.3), or a Format Format B LSE (Section 4.2), a Format C LSE (Section 4.3), or a Format
D LSE (Section 4.4). Thus, the available bits for data that can D LSE (Section 4.4). Thus, the available bits for data that can
change by a transit node or differ among packets of the same flow in change by a transit node or differ among packets of the same flow in
Format A and Format B LSEs are 0, Format C LSE is 7 (bits 20-22 and Format A and Format B LSEs is 0, in a Format C LSE 7 (bits 20-22 and
25-28) and Format D LSE is 11 (bits 20-22 and 24-31). 25-28), and in a Format D LSE 11 (bits 20-22 and 24-31).
Similarly, to preserve service stability, such data also MUST NOT be Similarly, to preserve service stability, such data also MUST NOT be
carried in the most significant 23 bits of these LSEs when the legacy carried in the most significant 23 bits of these LSEs when the legacy
implementation also uses the TC value, in addition to the label implementation also uses the TC value, in addition to the label
value, in all LSEs when computing ECMP decisions. value, in all LSEs when computing ECMP decisions.
The available mitigations for these problems are to use additional The available mitigations for these problems are to use additional
Format D LSEs to carry the data, or to place the data in Post-Stack Format D LSEs to carry the data or to place the data in Post-Stack
Data as described in [RFC9789]. Data as described in [RFC9789].
In network deployments where it is known that a load-balancing of In network deployments where it is known that a load-balancing of
data flows is not used, or, otherwise, if only the explicitly data flows is not used, or if only the explicitly signaled entropy
signaled entropy value is used, and it is certain that the load- value is used, and it is certain that the load-balancing path
balancing path selection will not be based on the label value of the selection will not be based on the label value of the LSEs, then the
LSEs, then the data in the label value of the LSEs in ISD MAY be data in the label value of the LSEs in the ISD MAY be mutable within
mutable within the data flow without causing the out-of-order the data flow without causing the out-of-order delivery of packets.
delivery of packets.
5.3. Scope 5.3. Scope
The IHS field in the Format B LSE indicates the scope of all the NAIs The IHS field in the Format B LSE indicates the scope of all the NAIs
encoded in the NAS. Scope defines which nodes along the MPLS path encoded in the NAS. Scope defines which nodes along the MPLS path
should perform the network actions found within the NAS. The should perform the network actions found within the NAS. The
specific values of the IHS field are as follows: specific values of the IHS field are as follows:
+======+=========================+ +======+=========================+
| Bits | Scope | | Bits | Scope |
+======+=========================+ +======+=========================+
| 00 | I2E | | 00 | I2E |
+------+-------------------------+ +------+-------------------------+
| 01 | HBH | | 01 | HbH |
+------+-------------------------+ +------+-------------------------+
| 10 | Select | | 10 | Select |
+------+-------------------------+ +------+-------------------------+
| 11 | Reserved for future use | | 11 | Reserved for future use |
+------+-------------------------+ +------+-------------------------+
Table 2: IHS Scope Values Table 2: IHS Scope Values
Ingress To Egress (I2E) - The Network Actions in this NAS MUST NOT Ingress to Egress (I2E): The Network Actions in this NAS MUST NOT be
be processed by any node except the egress node. processed by any node except the egress node.
Hop-By-Hop (HBH) - All nodes along the path MUST process the NAS. Hop-by-Hop (HbH): All nodes along the path MUST process the NAS.
Select - Only specific nodes along the path that brings NAS to top Select: Only specific nodes along the path that bring NAS to the top
of the stack will perform the action. of the stack will perform the action.
A given NAS can only carry NAIs with the same scope (I2E/HBH/Select). A given NAS can only carry NAIs with the same scope (I2E/HbH/Select).
To support multiple scopes for a single packet, multiple NASes MAY be To support multiple scopes for a single packet, multiple NASes MAY be
included in a single label stack. included in a single label stack.
The egress node is included in the HBH scope. This implies that the The egress node is included in the HbH scope. This implies that the
penultimate node MUST NOT remove a HBH NAS. The egress node may penultimate node MUST NOT remove an HbH NAS. The egress node may
receive a NAS at the top of the label stack as discussed in receive a NAS at the top of the label stack as discussed in
Section 9. Section 9.
An I2E scope NAS, if present, MUST be encoded after any HBH or An I2E scope NAS, if present, MUST be encoded after any HbH or
Select-scope NASes. This makes it easier for the transit nodes to Select-scope NASes. This makes it easier for the transit nodes to
process a NAS with HBH or Select scope. process a NAS with HbH or Select scope.
If a packet is received with the IHS scope set to "Reserved for If a packet is received with the IHS scope set to "Reserved for
future use", the packet is processed based on the U bit in the Format future use", the packet is processed based on the U bit in the Format
B LSE in the NAS. B LSE in the NAS.
5.4. Unknown Network Action Handling 5.4. Unknown Network Action Handling
The Unknown Network Action Handling (U) field in a Format B LSE The Unknown Network Action Handling (U) field in a Format B LSE
(Section 4.2) and Format C LSE (Section 4.3) is a 1-bit value that (Section 4.2) and Format C LSE (Section 4.3) is a 1-bit value that
defines the action to be taken by a node that does not understand an defines the action to be taken by a node that does not understand an
skipping to change at page 12, line 44 skipping to change at line 539
| Bit | Action | | Bit | Action |
+=====+=====================+ +=====+=====================+
| 0 | Skip to the next NA | | 0 | Skip to the next NA |
+-----+---------------------+ +-----+---------------------+
| 1 | Drop the packet | | 1 | Drop the packet |
+-----+---------------------+ +-----+---------------------+
Table 3: Unknown Network Table 3: Unknown Network
Action Handling Action Handling
When a packet with an unknown Network Action is dropped, the node When a packet with an Unknown Network Action Handling is dropped, the
should maintain a local counter for this event, and may send a rate- node should maintain a local counter for this event and may send a
limited notification to the operator. rate-limited notification to the operator.
5.5. Ordering 5.5. Ordering
The network actions encoded in the NAS MUST be processed in the order The network actions encoded in the NAS MUST be processed in the order
that they appear in the NAS, from the top of the NAS to the bottom. that they appear in the NAS, from the top of the NAS to the bottom.
NAIs encoded as flags (see Section 6.2) MUST be processed from the NAIs encoded as flags (see Section 6.2) MUST be processed from the
most significant bit to the least significant bit. If a label stack most significant bit to the least significant bit. If a label stack
contains multiple NASes, they MUST be processed in the order that contains multiple NASes, they MUST be processed in the order that
they appear in the label stack, subject to the restrictions in they appear in the label stack, subject to the restrictions in
Section 7. Section 7.
6. Special Opcodes 6. Special Opcodes
Below are the special opcodes defined to build a basic In-stack MNA Below are the special opcodes defined to build a basic In-stack MNA
solution and has been assigned through IANA registry (Section 14.4). solution and assigned in the "Network Action Opcodes" IANA registry
In the future, additional special opcodes can be defined and their (see Section 13.2.2). In the future, additional special opcodes may
code-points assigned from the "Network Action Opcodes" IANA registry be defined and their code points assigned from this registry.
(Section 14.4).
6.1. bSPL Protection 6.1. bSPL Protection
Opcode: 0 Opcode: 0
Purpose: Legacy implementations may scan the label stack looking for Purpose: Legacy implementations may scan the label stack looking for
bSPL values. As long as the opcode field is non-zero, an LSE cannot bSPL values. As long as the opcode field is non-zero, an LSE
be misinterpreted as containing a bSPL. Opcode 0 is therefore cannot be misinterpreted as containing a bSPL. Therefore, opcode
reserved and not to be used. 0 is reserved and not to be used.
6.2. Flag-Based NAIs without AD 6.2. Flag-Based NAIs Without AD
Opcode: 1 Opcode: 1
Purpose: This opcode is used for Network actions that do not require Purpose: This opcode is used for Network actions that do not require
Ancillary Data. A single flag can be used to indicate each of these AD. A single flag can be used to indicate each of these network
network actions. actions.
LSE Formats: B, C, D LSE Formats: B, C, D
Data: The data field carries Network Action Indicators, which should Data: The data field carries NAIs, which should be evaluated from
be evaluated from the most significant bit to the least significant the most significant bit to the least significant bit. If this
bit. If this opcode is used with LSE Format B only, then up to 13 opcode is used with LSE Format B only, then up to 13 flags may be
flags may be carried. If this opcode is used with LSE Format C only, carried. If this opcode is used with LSE Format C only, then up
then up to 20 flags may be carried. Format D LSEs can be used with to 20 flags may be carried. Format D LSEs can be used with format
format C LSEs to encode more than 20 flags. Flags are assigned from C LSEs to encode more than 20 flags. Flags are assigned from the
the "Network Action Flags Without Ancillary Data" registry "Network Action Flags Without Ancillary Data" registry
(Section 14.3). If flags need to be evaluated in a different order, (Section 13.2.1). If flags need to be evaluated in a different
multiple LSEs using this opcode may be used to specify the requested order, multiple LSEs using this opcode may be used to specify the
order. The Flag-Based Network Action Indicators MUST follow the requested order. The Flag-Based NAIs MUST follow the procedure
procedure for data specified in Section 5.2. for data specified in Section 5.2.
Scope: This opcode can be used with any scope. Scope: This opcode can be used with any scope.
6.3. No-Operation Opcode 6.3. No-Operation Opcode
Opcode: 2 Opcode: 2
Purpose: This opcode is used to indicate that this opcode does not Purpose: This opcode is used to indicate that it does not perform
perform any Network Action and MUST be skipped. any Network Action and MUST be skipped.
LSE Format: B LSE Format: B
Scope: Any scope value may be set and MUST be ignored. Scope: Any scope value may be set and MUST be ignored.
6.4. Extension Opcode 6.4. Extension Opcode
Opcode: 127 Opcode: 127
Purpose: This opcode is used to extend the current opcode range Purpose: This opcode is used to extend the current opcode range
beyond 127 in the future. If this opcode is not supported, then the beyond 127 in the future. If this opcode is not supported, then
packet with the opcode 127 MUST be dropped regardless of the setting the packet with opcode 127 MUST be dropped regardless of the
of the U bit. Use of this opcode is outside the scope of this setting of the U bit. Use of this opcode is outside the scope of
document. this document.
7. NAS placement in the Label Stack 7. NAS Placement in the Label Stack
The node adding a NAS to the label stack places a copy of the NAS The node adding a NAS to the label stack places a copy of the NAS
where the relevant nodes can read it. Each downstream node along the where the relevant nodes can read it. Each downstream node along the
path has a Readable Label Depth (RLD). If the NAS is to be processed path has a Readable Label Depth (RLD). If the NAS is to be processed
by a downstream MNA-capable node, then the entire NAS MUST be placed by a downstream MNA-capable node, then the entire NAS MUST be placed
so that it is within RLD by the time the packet reaches the so that it is within RLD by the time the packet reaches the
downstream MNA-capable node. The RLD of the downstream MNA-capable downstream MNA-capable node. The RLD of the downstream MNA-capable
node MUST be learned as described in Section 2.3.1 of [RFC9789]. node MUST be learned as described in Section 2.3.1 of [RFC9789].
If the label stack is deep, several copies of the NAS may need to be If the label stack is deep, several copies of the NAS may need to be
encoded in the label stack. encoded in the label stack.
For a NAS with HBH scope, every node will process the top copy of the For a NAS with HbH scope, every node will process the top copy of the
NAS, but the NAS MUST NOT appear at the top of the stack at any MNA- NAS. However, the NAS MUST NOT appear at the top of the stack at any
incapable node on the path, that is ensured by the encapsulating node MNA-incapable node on the path that is ensured by the encapsulating
using the node capability, as described in Section 8. node using the node capability, as described in Section 8.
A NAS MUST NOT appear at the top of the stack after popping the A NAS MUST NOT appear at the top of the stack after popping the
forwarding label on an MNA-incapable node on the path. forwarding label on an MNA-incapable node on the path.
The node behaviour, where a NAS with I2E and HBH scopes is also The behavior of a node where a NAS with I2E and HbH scopes is also
removed along with popping the forwarding label on a PHP node, is removed along with popping the forwarding label on a PHP node is
outside the scope of this document. outside the scope of this document.
For a NAS with Select scope, it is processed by the node that brings For a NAS with Select scope, it is processed by the node that brings
it to the top of stack (for example, in the case of using MPLS label it to the top of the stack (for example, in the case of using MPLS
pop operation in Segment Routing) and then the NAS is removed from label pop operation in Segment Routing); then, the NAS is removed
the stack. The select-scoped NAS needs to be inserted after the from the stack. The select-scoped NAS needs to be inserted after the
forwarding label and before the next forwarding label. It could be forwarding label and before the next forwarding label. It could be
inserted before or after a HBH NAS. Note that the case of a NAS with inserted before or after an HbH NAS. Note that the case of a NAS
Select scope with MPLS label swap operation (for example, with RSVP with Select scope with an MPLS label swap operation (for example,
Traffic Engineering LSPs) is for future study. with RSVP-TE LSPs) is for future study.
For I2E scope, only one copy of the NAS needs to be added at the For I2E scope, only one copy of the NAS needs to be added at the
bottom of the stack. bottom of the stack.
Transit, non-penultimate nodes that pop a forwarding label and expose A transit node that is not the penultimate node that pops a
a copy of a NAS MUST remove it. forwarding label and exposes a copy of a NAS MUST remove that NAS.
An MNA-capable node performing Penultimate Hop Popping (PHP) that An MNA-capable node performing Penultimate Hop Popping (PHP) that
pops the forwarding label with only the NAS(es) remaining on the pops the forwarding label with only the NAS(es) remaining on the
stack MUST NOT remove the NAS(es). Instead, it forwards the packet stack MUST NOT remove the NAS(es). Instead, it forwards the packet
with the NAS(es) at the top of stack to the next node. Note that the with the NAS(es) at the top of the stack to the next node. Note that
behavior of the PHP node, as defined in [RFC3270] for TC processing, the behavior of the PHP node, as defined in [RFC3270] for TC
and as defined in [RFC3443] for TTL processing, is not modified processing and as defined in [RFC3443] for TTL processing, is not
regardless of whether the PHP node supports MNA. modified regardless of whether the PHP node supports MNA.
The node that receives the NAS at the top of the label stack MUST The node that receives the NAS at the top of the label stack MUST
process and remove it. process and remove it.
7.1. Actions when Pushing Labels 7.1. Actions When Pushing Labels
An MNA-capable node may need to push additional labels as well as An MNA-capable node may need to push additional labels as well as
push new network actions onto a received packet. push new network actions onto a received packet.
While pushing additional labels on to the label stack of the received While pushing additional labels onto the label stack of the received
packet, the MNA-capable node MUST verify that the entire top-most NAS packet, the MNA-capable node MUST verify that the entire topmost NAS
with HBH scope is still within the RLD of the downstream MNA-capable with HbH scope is still within the RLD of the downstream MNA-capable
nodes. If required, the MNA-capable node MAY create a copy of the nodes. If required, the MNA-capable node MAY create a copy of the
top-most NAS with HBH scope and insert it within the RLD of the topmost NAS with HbH scope and insert it within the RLD of the
downstream MNA-capable nodes on the label stack. downstream MNA-capable nodes on the label stack.
When an MNA-capable node needs to push a new NAS with HBH scope on to When an MNA-capable node needs to push a new NAS with HbH scope on to
a received packet that already has a NAS with HBH scope, it SHOULD a received packet that already has a NAS with HbH scope, it SHOULD
copy (and merge) the network actions (including their Ancillary Data) copy (and merge) the network actions (including their AD) from the
from the received top-most NAS with HBH scope in the new NAS with HBH received topmost NAS with HbH scope in the new NAS with HbH scope.
scope. The new NAS MUST be placed within the RLD of the downstream The new NAS MUST be placed within the RLD of the downstream MNA-
MNA-capable nodes. This behavior can be based on local policy. capable nodes. This behavior can be based on local policy.
The new network actions added MUST NOT conflict with the network The new network actions added MUST NOT conflict with the network
actions in the received NAS with HBH scope. The mechanism to resolve actions in the received NAS with HbH scope. The mechanism to resolve
such conflicts depend on the network actions and can be based on such conflicts depends on the network actions and can be based on
local policy. The MNA-capable node that pushes entries MUST local policy. The MNA-capable node that pushes entries MUST
understand any network actions which it is pushing which may result understand any network actions that it is pushing that may result in
in a conflict, and MUST resolve any conflicts between new and a conflict and MUST resolve any conflicts between new and received
received network actions. In the usual case of a conflict of network actions. In the usual case of a conflict of duplicating a
duplicating a network action, the definition of a network action MUST network action, the definition of a network action MUST give guidance
give guidance on conflict resolution. on conflict resolution.
8. Node Capability Signaling 8. Node Capability Signaling
The encapsulating node MUST make sure that the NAS can be processed The encapsulating node MUST make sure that the NAS can be processed
by the transit and egress nodes. In addition, the encapsulated by the transit and egress nodes. In addition, the encapsulated
packet MUST NOT exceed the path MTU as described in [RFC3032]. packet MUST NOT exceed the path MTU as described in [RFC3032].
* The node responsible for selecting a path through the MPLS network * The node responsible for selecting a path through the MPLS network
needs to know and consider the MNA-capabilities and RLD of the needs to know and consider the MNA-capabilities and RLD of the
transit nodes, and the MNA-capabilities of the egress node as transit nodes as well as the MNA-capabilities of the egress node
described in Section 2.3 of [RFC9789]. as described in Section 2.3 of [RFC9789].
* Information about the capabilities of the nodes may be configured, * Information about the capabilities of the nodes may be configured,
collected through management protocols, or distributed by control collected through management protocols, or distributed by control
protocols (such as advertising by routing protocols). protocols (such as advertising by routing protocols).
* The mechanisms by which the capabilities of the nodes are known by * The mechanisms by which the capabilities of the nodes are known by
the node responsible for selecting a path through the MPLS network the node responsible for selecting a path through the MPLS network
are out of scope for this document. are out of scope for this document.
* In the case of MPLS Segment Routing (SR-MPLS), as well as the RLD, * In the case of Segment Routing over MPLS (SR-MPLS), as well as the
the path computation system needs to know the MSD [RFC8664] that RLD, the path computation system needs to know the Maximum SID
can be imposed at the ingress node of a given SR path. This Depth (MSD) [RFC8664] that can be imposed at the ingress node of a
ensures that the label stack depth of a computed path does not given SR path. This ensures that the label stack depth of a
exceed the maximum number of labels (i.e., MSD) the node is computed path does not exceed the maximum number of labels (i.e.,
capable of imposing and the maximum number of labels that can be MSD) the node is capable of imposing and the maximum number of
read by the MNA-processing nodes in the path. The MSD MUST labels that can be read by the MNA-processing nodes in the path.
include the MNA Sub-Stacks that will be added. The MSD MUST include the MNA Sub-Stacks that will be added.
* The encapsulating node MUST learn about the RLD of the nodes in * The encapsulating node MUST learn about the RLD of the nodes in
the path as described in Section 2.3.1 of [RFC9789]. the path as described in Section 2.3.1 of [RFC9789].
9. Processing the Network Action Sub-Stack 9. Processing the Network Action Sub-Stack
This section defines the specific responsibilities for nodes along an This section defines the specific responsibilities for nodes along an
LSP [RFC3031]. LSP [RFC3031].
9.1. Encapsulating Node Responsibilities 9.1. Encapsulating Node Responsibilities
The encapsulating node MAY add NASes to the label stack in accordance The encapsulating node MAY add NASes to the label stack in accordance
with its policies, the placement restrictions in Section 7, and the with its policies, the placement restrictions in Section 7, and the
capabilities learned from Section 8. capabilities learned from Section 8.
If there is an existing label stack, the encapsulating node MUST NOT If there is an existing label stack, the encapsulating node MUST NOT
modify the first 20 bits of any LSE in the label stack when the ECMP modify the first 20 bits of any LSE in the label stack when the ECMP
technique in the network is using the hashing of the labels on the technique in the network uses hashing of the labels on the label
label stack. stack.
9.2. Transit Node Responsibilities 9.2. Transit Node Responsibilities
The transit node is the node that processes a NAS in the Label stack The transit node is the node that processes a NAS in the Label stack
but does not push any new NAS. but does not push any new NAS.
The transit node MUST follow the procedure for data specified in The transit node MUST follow the procedure for data specified in
Section 5.2. Section 5.2.
Transit nodes MUST process the NASes in the label stack, according to Transit nodes MUST process the NASes in the label stack according to
the rules set out in Section 5.5. the rules set out in Section 5.5.
A transit node that processes a NAS and does not recognize the value A transit node that processes a NAS and does not recognize the value
of an opcode MUST follow the rules according to the setting of the of an opcode MUST follow the rules according to the setting of the
Unknown Action Handling value in the NAS as described in Unknown Network Action Handling value in the NAS as described in
(Section 5.4). Section 5.4.
9.3. Penultimate Node Responsibilities 9.3. Penultimate Node Responsibilities
In addition to the transit node responsibilities, the penultimate In addition to the transit node responsibilities, the penultimate
node and penultimate SR-MPLS segment node MUST NOT remove the last node and penultimate SR-MPLS segment node MUST NOT remove the last
copy of an HBH or I2E NAS when it is exposed after removing the copy of an HbH or I2E NAS when it is exposed after removing the
forwarding (transport) label. This allows the egress node to process forwarding (transport) label. This allows the egress node to process
the NAS. the NAS.
9.4. Egress Node Responsibilities 9.4. Egress Node Responsibilities
The egress node MUST remove any NAS it receives. The egress node MUST remove any NAS it receives.
10. Network Action Indicator Opcode Definition 10. Network Action Indicator Opcode Definition
The following information MUST be defined for a new Network Action The following information MUST be defined for a new NAI opcode
Indicator opcode request in the document that specifies the Network request in the document that specifies the Network Action.
Action.
A request for a new NAI opcode MUST include the following
information:
* Format: The definition of the new Network Action MUST specify the Format: The definition of the new Network Action MUST specify the
LSE Formats. The opcode can define Network Action in Format B or LSE formats. The opcode can define Network Action in Format B or
C or both Format B and C. Both Format B and C LSEs MAY optionally C or both Formats B and C. Both Format B and C LSEs MAY
carry Format D LSEs. optionally carry Format D LSEs.
* Scope: The definition of the new Network Action MUST specify at Scope: The definition of the new Network Action MUST specify at
least one scope (I2E, HBH, Select) for the Network Action, and MAY least one scope (I2E, HbH, Select) for the Network Action and MAY
specify more than one scope. specify more than one scope.
* Ancillary Data: The definition of the new Network Action MUST Ancillary Data: The definition of the new Network Action MUST
specify the quantity, syntax, and semantics of any associated specify the quantity, syntax, and semantics of any associated AD.
Ancillary Data. The Ancillary Data MAY be variable length, but The AD MAY be variable length, but the NAL MUST be computable
the NAL MUST be computable based on the data added in the NAS. based on the data added in the NAS.
* Processing: The definition of the new Network Action MUST specify Processing: The definition of the new Network Action MUST specify
the detailed procedure for processing the network action. the detailed procedure for processing the network action.
* Interactions: The definition of the new Network Action MUST Interactions: The definition of the new Network Action MUST specify
specify its interaction including merging with other currently its interaction including merging with other currently defined
defined Network Action if there is any. Network Action if there is any.
An assignment for a NAI MAY make requests from any combination of the An assignment for a NAI MAY make requests from any combination of the
"Network Action Opcodes" or "Network Action Flags Without Ancillary "Network Action Opcodes" or "Network Action Flags Without Ancillary
Data" assignments. This decision should optimize for eventual Data" assignments (see Section 13). This decision should optimize
encoding efficiency. If the NAI does not require any ancillary data, for eventual encoding efficiency. If the NAI does not require any
then a flag is preferred as only one bit is used in the encoding. AD, then a flag is preferred as only one bit is used in the encoding.
11. Implementation Status
[Note to the RFC Editor - remove this section before publication, as
well as remove the reference to [RFC7942]]
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.
11.1. University of Tuebingen Implementation
The solution defined in the document draft-ietf-mpls-mna-hdr-08 has
been implemented using P4 pipeline. The implementation code can be
found at https://github.com/uni-tue-kn/P4-MNA. This implementation
uses bSPL value 4 as an MNA label.
12. Security Considerations 11. Security Considerations
The security considerations in [RFC3032] and [RFC9789] also apply to The security considerations in [RFC3032] and [RFC9789] also apply to
this document. this document.
In addition, MNA creates a new dimension in security concerns: In addition, MNA creates a new dimension in security concerns:
* The actions of an encapsulating node can affect any or all of the * The actions of an encapsulating node can affect any or all of the
nodes along the path. In the most common and benign situations, nodes along the path. In the most common and benign situations, a
such as a syntactically incorrect packet could result in packet syntactically incorrect packet could result in packet loss or
loss or corruption. corruption, for example.
* The semantics of a network action are unbounded and may be * The semantics of a network action are unbounded and may be
insecure. A network action could be defined that made arbitrary insecure. A network action could be defined that makes arbitrary
changes to the memory of the forwarding router, which could then changes to the memory of the forwarding router, which could then
be used by the encapsulating node to compromise every MNA-capable be used by the encapsulating node to compromise every MNA-capable
router in the network. router in the network.
* The MNA architecture supports locally-defined network actions. * The MNA architecture supports locally defined network actions.
For such actions, there will be limited oversight to ensure that For such actions, there will be limited oversight to ensure that
the semantics do not create security issues. Implementors and the semantics do not create security issues. Implementors and
network operators will need to ensure that even the locally- network operators will need to ensure that even the locally
defined network actions do not compromise the security of the defined network actions do not compromise the security of the
network by following the security considerations specified in this network by following the security considerations specified in this
document. document.
* The MPLS domain border nodes MUST ensure that the MPLS packets * The MPLS domain border nodes MUST ensure that the MPLS packets
with MNA from any domain with a different administrative control with MNA from any domain with a different administrative control
can be filtered to prevent entering the provider MPLS domain. The can be filtered to prevent entering the provider MPLS domain. The
filtering capability MAY be enabled on a per network action basis filtering capability MAY be enabled on a per-network-action basis,
and it can be based on a local policy. The filtering capability and it can be based on a local policy. The filtering capability
MUST be implemented on those nodes before deploying MNA in the MUST be implemented on those nodes before deploying MNA in the
provider MPLS domain. The RLD on the filtering node MUST be provider MPLS domain. The RLD on the filtering node MUST be
higher than the RLD on all other nodes in the provider MPLS higher than the RLD on all other nodes in the provider MPLS
domain. domain.
* The MNA architecture supports modifying the AD on the intermediate * The MNA architecture supports modifying the AD on the intermediate
nodes, so the critical network functions should either not rely on nodes so the critical network functions either should not rely on
the data or should be aware of the risks and use other means to the data or should be aware of the risks and use other means to
verify the security of the whole network. verify the security of the whole network.
* The "private Use" opcodes in "Network Action Opcodes" Section 14.4 * The "Private Use" opcodes in the "Network Action Opcodes" registry
and "Network Action Flags Without Ancillary Data" Section 14.3 (see Section 13.2.2) and the "Network Action Flags Without
Registry are subject to the considerations described in [RFC8126]. Ancillary Data" registry (see Section 13.2.1) are subject to the
considerations described in [RFC8126].
* System designers must be aware that information included in * System designers must be aware that information included in AD may
Ancillary Data may be transmitted "in the clear." Network actions be transmitted "in the clear". Network actions that require the
that require the exchange of sensitive data, must be defined in exchange of sensitive data must be defined in such a way that the
such a way that the data is encrypted in transit. Otherwise, data is encrypted in transit. Otherwise, sensitive data MUST NOT
sensitive data MUST NOT be transmitted using these mechanisms. be transmitted using these mechanisms.
* Mis-delivery of a packet due to malformed forwarding action data * Mis-delivery of a packet due to malformed forwarding action data
could be considered a security risk. could be considered a security risk.
13. Operational Considerations 12. Operational Considerations
13.1. Manageability Considerations 12.1. Manageability Considerations
An MNA implementation MAY collect the following counters: An MNA implementation MAY collect the following counters:
* Packets with MNA received * Packets with MNA received
* MNA sub-stacks processed * MNA sub-stacks processed
* MNA per-network-action counters * MNA per-network-action counters
* Packets with MNA dropped due to unknown actions * Packets with MNA dropped due to unknown actions
* Packets with MNA skipped due to unknown actions * Packets with MNA skipped due to unknown actions
* Packets with MNA dropped due to malformed NAS * Packets with MNA dropped due to malformed NAS
Additionally, tracking both successful invocations and failures for Additionally, tracking both successful invocations and failures for
each specific Network Action, are RECOMMENDED to provide granular each specific Network Action is RECOMMENDED to provide granular
visibility. Nodes MAY generate rate-limited notifications or alarms visibility. Nodes MAY generate rate-limited notifications or alarms
for significant operational events, such as sustained high rates of for significant operational events, such as sustained high rates of
MNA packet drops, frequent encounters of malformed MNA sub-stacks, to MNA packet drops or frequent encounters of malformed MNA sub-stacks,
alert operators to potential issues. Comprehensive logging of MNA to alert operators to potential issues. Comprehensive logging of MNA
processing details and outcomes can aid in the network diagnostics processing details and outcomes can aid in the network diagnostics
and post-mortem analysis. and post-mortem analysis.
13.2. Performance and Scale Considerations 12.2. Performance and Scale Considerations
The considerations for performance and scale assessments are outside The considerations for performance and scale assessments are outside
the scope of this document but are encouraged to be addressed in the the scope of this document but are encouraged to be addressed in the
MNA application documents. MNA application documents.
13.3. Backward Compatibility 12.3. Backward Compatibility
This section discusses interactions between MNA-capable and MNA- This section discusses interactions between MNA-capable and MNA-
incapable nodes. incapable nodes.
An MNA-encapsulating node MUST ensure that the MPLS Network Action An MNA encapsulating node MUST ensure that the MPLS Network Action
Sub-Stack indicator is not at the top of the MPLS label stack when Sub-Stack indicator is not at the top of the MPLS label stack when
the packet arrives at an MNA-incapable node. If such a packet did the packet arrives at an MNA-incapable node. If such a packet did
arrive at an MNA-incapable node, it will most likely be dropped as arrive at an MNA-incapable node, it will most likely be dropped as
described in Section 2.1.1 of [RFC7325]. described in Section 2.1.1 of [RFC7325].
Any node could scan the label stack, potentially looking for a label Any node could scan the label stack, potentially looking for a label
value containing a bSPL. To ensure that the LSE formats described value containing a bSPL. To ensure that the LSE formats described
herein do not appear to contain a bSPL value, the opcode value of 0 herein do not appear to contain a bSPL value, the opcode value of 0
has been reserved. By ensuring that there is a non-zero value in the has been reserved. By ensuring that there is a non-zero value in the
high order 7 bits, we are assured that the high order 20 bits cannot high-order 7 bits, we are assured that the high-order 20 bits cannot
be misinterpreted as containing a bSPL value (0-15). be misinterpreted as containing a bSPL value (0-15).
The TC and TTL values of the Format A LSE are not re-purposed for The TC and TTL values of the Format A LSE are not repurposed for
encoding, as the penultimate node on the MPLS packet path may encoding, as the penultimate node on the MPLS packet path may
propagate TTL from the transport (or forwarding) label to the next propagate TTL from the transport (or forwarding) label to the next
label on the label stack, overwriting the TTL on the next label. If label on the label stack, overwriting the TTL on the next label. If
the penultimate node is a legacy node, it might perform this action, the penultimate node is a legacy node, it might perform this action,
potentially corrupting other values stored in the TC and TTL values. potentially corrupting other values stored in the TC and TTL values.
To protect against this, we retain the TC and TTL values in the To protect against this, we retain the TC and TTL values in the
Format A LSE. Format A LSE.
When adding the Entropy Label Indicator (ELI) (bSPL 7) and Entropy When adding the Entropy Label Indicator (ELI) (bSPL 7) and Entropy
Label (EL) as defined in [RFC6790], along with an MNA NAS, the RLD Label (EL) as defined in [RFC6790], along with an MNA NAS, the RLD
MUST be considered for the placement of both, and they both can be MUST be considered for the placement of both, and they both can be
placed in any order. If a transit LSR chooses to use as much of the placed in any order. If a transit LSR chooses to use as much of the
whole label stack as feasible as keys for the load-balancing whole label stack as feasible as a key for the load-balancing
function, the MNA reserved label MUST NOT be used as a key for the function, the MNA-reserved label MUST NOT be used as a key for the
load-balancing function, as specified in Section 4.3 of [RFC6790]. load-balancing function, as specified in Section 4.3 of [RFC6790].
Note that the behavior of an MNA-incapable transit LSR that scans the Note that the behavior of an MNA-incapable transit LSR that scans the
label stack for ELI and EL but encounters a different, unrecognized label stack for ELI and EL but encounters a different, unrecognized
reserved label first, is not modified by this document. reserved label first, is not modified by this document.
Similarly, when adding the Flow-ID Label Indicator (FLI) (including Similarly, when adding the Flow-ID Label Indicator (FLI) (including
the extension label 15) and Flow-ID Label (FL) as defined in the extension label 15) and Flow-ID Label (FL) as defined in
[RFC9714], along with an MNA NAS, the RLD MUST be considered for the [RFC9714], along with an MNA NAS, the RLD MUST be considered for the
placement of both, and they both can be placed in any order. Note placement of both, and they both can be placed in any order. Note
that the behavior of an MNA-incapable transit LSR that scans the that the behavior of an MNA-incapable transit LSR that scans the
label stack for FLI (including the extension label 15) and FL, but label stack for FLI (including the extension label 15) and FL, but
encounters a different, unrecognized reserved label first, is not encounters a different, unrecognized reserved label first, is not
modified by this document. modified by this document.
However, as the existing behavior is not specified for transit LSRs, However, as the existing behavior is not specified for transit LSRs,
upon encountering any unrecognized bSPLs or eSPLs below the top of upon encountering any unrecognized bSPLs or extended SPLs (eSPLs)
the label stack, some existing implementations may have chosen to below the top of the label stack, some existing implementations may
implement non-standardized actions, such as discarding packets. Any have chosen to implement non-standardized actions, such as discarding
uses of a new bSPL or eSPL would cause issues with such existing packets. Any uses of a new bSPL or eSPL would cause issues with such
implementations using the non-standardized actions upon encountering existing implementations using the non-standardized actions upon
unrecognized bSPLs or eSPLs below the top of the label stack. Since encountering unrecognized bSPLs or eSPLs below the top of the label
this is a generic problem, any clarifications for the treatment of stack. Since this is a generic problem, any clarifications for the
unrecognized bSPL or eSPL are outside the scope of this document. treatment of unrecognized bSPL or eSPL are outside the scope of this
document.
14. IANA Considerations 13. IANA Considerations
14.1. MNA bSPL Label 13.1. MNA bSPL Label
This document requests that IANA allocate a value (TBA) for the MNA IANA has allocated the value 4 for the MNA bSPL label from the "Base
bSPL label from the "Base Special-Purpose MPLS Label Values" registry Special-Purpose MPLS Label Values" registry to indicate the presence
to indicate the presence of an MNA Sub-Stack in the label stack. The of an MNA Sub-Stack in the label stack. The description of the value
description of the value should be "MPLS Network Actions". The is "MPLS Network Actions".
reference should be this document.
14.2. MPLS Network Actions Parameters 13.2. MPLS Network Actions Parameters
This document requests that IANA create a new registry group called IANA has created a registry group called "MPLS Network Actions"
"MPLS Network Actions Parameters" within the "Multiprotocol Label within the "Multiprotocol Label Switching Architecture (MPLS)"
Switching Architecture (MPLS)" category. The registries described category. This registry group contains the "Network Action Flags
below should belong to this new registry group. Without Ancillary Data" registry (see Section 13.2.1) and the
"Network Action Opcodes" registry (see Section 13.2.2).
14.3. Network Action Flags Without Ancillary Data 13.2.1. Network Action Flags Without Ancillary Data
This document requests that IANA create a new registry with the name For the "Network Action Flags Without Ancillary Data" registry,
"Network Action Flags Without Ancillary Data". Registration requests registration requests should comply with Section 10. Depending on
should comply with Section 10. The registration procedure for this the range, the registration procedure for this registry is "IETF
registry is "IETF Review", "Experimental Use" and "Private Use" as Review", "Experimental Use", or "Private Use" (as defined in
defined in [RFC8126]. The fields in this registry are "Bit Position" [RFC8126]). The fields in this registry are "Bit Position"
(integer), "Description" (string), and "Reference" (string). (integer), "Description" (string), and "Reference" (string).
Bit Position refers to the position relative to the most significant Bit Position refers to the position relative to the most significant
bit in LSE Format B or C Data fields and any subsequent Format D bit in LSE Format B or C Data fields and any subsequent Format D
LSEs. Bit Position 0 is the most significant bit in an LSE Format B LSEs. Bit Position 0 is the most significant bit in an LSE Format B
or C Data field. Bit Position 20 is the most significant bit in the or C Data field. Bit Position 20 is the most significant bit in the
first LSE Format D Data field. There are 20 bits available in LSE first LSE Format D Data field. There are 20 bits available in LSE
Format C and 30 bits available in LSE Format D. There are at most 14 Format C and 30 bits available in LSE Format D. There are, at most,
Format D LSEs per opcode (due to NASL limit of 15 and Format D 14 Format D LSEs per opcode (due to the NASL limit of 15 and Format D
requires Format C LSE), so there are at most 20 + 14 * 30 = 440 bit requires Format C LSE), so there are at most 20 + 14 * 30 = 440 bit
positions. The Bit Position is an integer with value 0-439. positions. The value listed in the Bit Position column is an integer
with value between 0-439.
The registration procedures for the code points allocation for this The registration procedures for code point allocation for this
registry are defined in Table 4: registry are defined in Table 4:
+==============+==================+===============+ +========+========================+
| Bit Position | Description | Reference | | Range | Registration Procedure |
+==============+==================+===============+ +========+========================+
| 0-14 | IETF Review | This document | | 0-14 | IETF Review |
+--------------+------------------+---------------+ +--------+------------------------+
| 15-16 | Experimental Use | This document | | 15-16 | Experimental Use |
+--------------+------------------+---------------+ +--------+------------------------+
| 17-19 | Private Use | This document | | 17-19 | Private Use |
+--------------+------------------+---------------+ +--------+------------------------+
| 20-439 | IETF Review | This document | | 20-439 | IETF Review |
+--------------+------------------+---------------+ +--------+------------------------+
Table 4: Network Action Flags Without Ancillary Table 4: Registration
Data Registry Procedures for the "Network
Action Flags Without Ancillary
Data" Registry
14.4. Network Action Opcodes 13.2.2. Network Action Opcodes
This document requests that IANA create a new registry with the name For the "Network Action Opcodes" registry, registration requests
"Network Action Opcodes". Registration requests should comply with should comply with Section 10 as well as security review. Depending
Section 10 as well as security review. The registration procedure on the range, the registration procedure for this registry is "IETF
for this registry is "IETF Review", "Experimental Use" and "Private Review", "Experimental Use", or "Private Use" (as defined in
Use" as defined in [RFC8126]. The fields are "Opcode" (integer), [RFC8126]). The fields are "Opcode" (integer), "Description"
"Description" (string), and "Reference" (string). Opcode is an (string), and "Reference" (string). Opcode is an integer with value
integer with value 1-126. 1-126.
+=========+==================+===============+ +=========+========================+
| Opcode | Description | Reference | | Range | Registration Procedure |
+=========+==================+===============+ +=========+========================+
| 1-110 | IETF Review | This document | | 1-110 | IETF Review |
+---------+------------------+---------------+ +---------+------------------------+
| 111-114 | Experimental Use | This document | | 111-114 | Experimental Use |
+---------+------------------+---------------+ +---------+------------------------+
| 115-126 | Private Use | This document | | 115-126 | Private Use |
+---------+------------------+---------------+ +---------+------------------------+
| 127 | IETF Review | This document | | 127 | IETF Review |
+---------+------------------+---------------+ +---------+------------------------+
Table 5: Network Action Opcodes Registry Table 5: Registration Procedures
for the "Network Action Opcodes"
Registry
IANA has allocated values for the following Network Action Opcodes IANA has allocated values for the following Network Action Opcodes
from the "Network Action Opcodes" registry. from the "Network Action Opcodes" registry.
+========+===========================+===============+ +========+===========================+===========+
| Opcode | Description | Reference | | Opcode | Description | Reference |
+========+===========================+===============+ +========+===========================+===========+
| 0 | Reserved | This document | | 0 | Reserved | RFC 9994 |
+--------+---------------------------+---------------+ +--------+---------------------------+-----------+
| 1 | Flag-Based Network Action | This document | | 1 | Flag-Based Network Action | RFC 9994 |
| | Indicators without AD | | | | Indicators without AD | |
+--------+---------------------------+---------------+ +--------+---------------------------+-----------+
| 2 | No operation Opcode | This document | | 2 | No operation Opcode | RFC 9994 |
+--------+---------------------------+---------------+ +--------+---------------------------+-----------+
| 127 | Opcode Range Extension | This document | | 127 | Opcode Range Extension | RFC 9994 |
| | Beyond 127 | | | | Beyond 127 | |
+--------+---------------------------+---------------+ +--------+---------------------------+-----------+
Table 6: Network Action Opcodes Table 6: Initial Contents of the "Network
Action Opcodes" Registry
15. References 14. References
15.1. Normative References 14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001, Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>. <https://www.rfc-editor.org/info/rfc3032>.
skipping to change at page 25, line 29 skipping to change at line 1104
[RFC9017] Andersson, L., Kompella, K., and A. Farrel, "Special- [RFC9017] Andersson, L., Kompella, K., and A. Farrel, "Special-
Purpose Label Terminology", RFC 9017, Purpose Label Terminology", RFC 9017,
DOI 10.17487/RFC9017, April 2021, DOI 10.17487/RFC9017, April 2021,
<https://www.rfc-editor.org/info/rfc9017>. <https://www.rfc-editor.org/info/rfc9017>.
[RFC9789] Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS [RFC9789] Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS
Network Actions (MNAs) Framework", RFC 9789, Network Actions (MNAs) Framework", RFC 9789,
DOI 10.17487/RFC9789, July 2025, DOI 10.17487/RFC9789, July 2025,
<https://www.rfc-editor.org/info/rfc9789>. <https://www.rfc-editor.org/info/rfc9789>.
15.2. Informative References 14.2. Informative References
[RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
Label Switching Architecture", RFC 3031, Label Switching Architecture", RFC 3031,
DOI 10.17487/RFC3031, January 2001, DOI 10.17487/RFC3031, January 2001,
<https://www.rfc-editor.org/info/rfc3031>. <https://www.rfc-editor.org/info/rfc3031>.
[RFC6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu, [RFC6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu,
D., and S. Mansfield, "Guidelines for the Use of the "OAM" D., and S. Mansfield, "Guidelines for the Use of the "OAM"
Acronym in the IETF", BCP 161, RFC 6291, Acronym in the IETF", BCP 161, RFC 6291,
DOI 10.17487/RFC6291, June 2011, DOI 10.17487/RFC6291, June 2011,
<https://www.rfc-editor.org/info/rfc6291>. <https://www.rfc-editor.org/info/rfc6291>.
[RFC7325] Villamizar, C., Ed., Kompella, K., Amante, S., Malis, A., [RFC7325] Villamizar, C., Ed., Kompella, K., Amante, S., Malis, A.,
and C. Pignataro, "MPLS Forwarding Compliance and and C. Pignataro, "MPLS Forwarding Compliance and
Performance Requirements", RFC 7325, DOI 10.17487/RFC7325, Performance Requirements", RFC 7325, DOI 10.17487/RFC7325,
August 2014, <https://www.rfc-editor.org/info/rfc7325>. August 2014, <https://www.rfc-editor.org/info/rfc7325>.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W., [RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664, Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019, DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>. <https://www.rfc-editor.org/info/rfc8664>.
[RFC9613] Bocci, M., Ed., Bryant, S., and J. Drake, "Requirements [RFC9613] Bocci, M., Ed., Bryant, S., and J. Drake, "Requirements
for Solutions that Support MPLS Network Actions (MNAs)", for Solutions that Support MPLS Network Actions (MNAs)",
RFC 9613, DOI 10.17487/RFC9613, August 2024, RFC 9613, DOI 10.17487/RFC9613, August 2024,
<https://www.rfc-editor.org/info/rfc9613>. <https://www.rfc-editor.org/info/rfc9613>.
skipping to change at page 26, line 31 skipping to change at line 1148
[RFC9791] Saad, T., Makhijani, K., Song, H., and G. Mirsky, "Use [RFC9791] Saad, T., Makhijani, K., Song, H., and G. Mirsky, "Use
Cases for MPLS Network Action Indicators and Ancillary Cases for MPLS Network Action Indicators and Ancillary
Data", RFC 9791, DOI 10.17487/RFC9791, July 2025, Data", RFC 9791, DOI 10.17487/RFC9791, July 2025,
<https://www.rfc-editor.org/info/rfc9791>. <https://www.rfc-editor.org/info/rfc9791>.
Appendix A. Examples Appendix A. Examples
A.1. Network Action Encoding Examples A.1. Network Action Encoding Examples
A.1.1. Network Action Flags without AD A.1.1. Network Action Flags Without AD
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MNA-Label=bSPL | TC |S| TTL | | MNA-Label=bSPL | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=1 | 13-bit Flags |R|IHS|S|NASL=0 |U|NAL=0| | Opcode=1 | 13-bit Flags |R|IHS|S|NASL=0 |U|NAL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: NAS with Network Action Flags Figure 6: NAS with Network Action Flags
This is an example of a NAS with Flag-Based NAIs without Ancillary This is an example of a NAS with Flag-Based NAIs without AD.
Data.
Details: Details:
Opcode=1: This opcode to indicates that the LSE carries Flag-Based Opcode=1: This opcode indicates that the LSE carries Flag-Based NAIs
NAIs without AD. without AD.
Data: The data field carries the Flag-Based NAIs. Data: The data field carries the Flag-Based NAIs.
S: This is the bottom of stack bit. Set if and only if this LSE S: This is the bottom of the stack bit. Set if and only if this LSE
is the bottom of the stack. is the bottom of the stack.
U: Action to be taken if one of the NAIs are not recognized by the U: Action to be taken if one of the NAIs is not recognized by the
processing node. processing node.
NASL: The NASL value is set to 0, as there are no additional LSEs. NASL: The NASL value is set to 0, as there are no additional LSEs.
NAL: The NAL value is set to 0, as there are no additional AD NAL: The NAL value is set to 0, as there are no additional AD
encoded using Format D. encoded using Format D.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MNA-Label=bSPL | TC |S| TTL | | MNA-Label=bSPL | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=2 | Data=0 |R|IHS|S|NASL=2 |U|NAL=0| | Opcode=2 | Data=0 |R|IHS|S|NASL=2 |U|NAL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=1 | Flag-Based NAIs |S| NAIs |U|NAL=1| | Opcode=1 | Flag-Based NAIs |S| NAIs |U|NAL=1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| Additional Flag-Based NAIs |S|Flag-Based-NAIs| |1| Additional Flag-Based NAIs |S|Flag-Based-NAIs|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Network Action Flags without AD using LSE Format D Figure 7: Network Action Flags Without AD Using LSE Format D
In this example, the NAS contains a Format B LSE with No-Operation In this example, the NAS contains a Format B LSE with a No-Operation
Opcode value 2. The next LSE uses Format C, but the Network Action Opcode value 2. The next LSE uses Format C, but the Network Action
Flag is not in a bit position contained within the Format C LSE, so a Flag is not in a bit position contained within the Format C LSE, so a
single Format D LSE has been added to the NAS to carry the flag. single Format D LSE has been added to the NAS to carry the flag.
NAL is set to 1 to indicate that Flag-Based NAIs are also encoded in NAL is set to 1 to indicate that Flag-Based NAIs are also encoded in
the next LSE. the next LSE.
NASL is set to 2 to indicate that 2 additional LSEs are used. NASL is set to 2 to indicate that two additional LSEs are used.
A.1.2. Network Action Opcode with AD A.1.2. Network Action Opcode with AD
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MNA-Label=bSPL | TC |S| TTL | | MNA-Label=bSPL | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=8 | Ancillary Data |R|IHS|S|NASL=0 |U|NAL=0| | Opcode=8 | Ancillary Data |R|IHS|S|NASL=0 |U|NAL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Network action opcode with Ancillary Data Figure 8: Network Action Opcode with Ancillary Data
In this example, the NAS is carrying only one Network Action that In this example, the NAS is carrying only one Network Action that
requires 13 bits of Ancillary Data. requires 13 bits of AD.
Details on the Second LSE Details on the Second LSE:
Opcode=8: A network action allocation is outside of this document. Opcode=8: A network action allocation is outside of this document.
Data: The data field contains 13 bits of ancillary data. Data: The data field contains 13 bits of AD.
A.1.3. Network Action Opcode with more AD with Format-B A.1.3. Network Action Opcode with More AD with Format-B
A network action may require more Ancillary Data than can fit in a A network action may require more AD than can fit in a single LSE.
single LSE. In this example, a Format D LSE is added to carry In this example, a Format D LSE is added to carry additional AD.
additional Ancillary Data.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MNA-Label=bSPL | TC |S| TTL | | MNA-Label=bSPL | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=10 | Ancillary Data |R|IHS|S|NASL=1 |U|NAL=1| | Opcode=10 | Ancillary Data |R|IHS|S|NASL=1 |U|NAL=1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| Ancillary Data |S|Ancillary Data | |1| Ancillary Data |S|Ancillary Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Network Action With Additional Ancillary Data Figure 9: Network Action with Additional Ancillary Data
In this example, opcode 10 is encoded in Format B and it requires In this example, opcode 10 is encoded in Format B, and it requires
more than one LSE's worth of Ancillary Data, so a Format D LSE is more than one LSE's worth of AD, so a Format D LSE is added.
added.
Details on the second LSE: Details on the second LSE:
Opcode=10: An opcode allocation is outside of this document. Opcode=10: An opcode allocation is outside of this document.
Ancillary Data: Ancillary data required to process the Network Ancillary Data: AD required to process the Network Action opcode 10.
Action opcode 10.
NAL: Length of additional LSEs used to encode its Ancillary data. NAL: Length of additional LSEs used to encode its AD.
Details on the third LSE: Details on the third LSE:
Ancillary Data: 22 bits of additional Ancillary data. Ancillary Data: 22 bits of additional AD.
Ancillary Data: 8 bits of additional Ancillary Data. Ancillary Data: 8 bits of additional AD.
A.1.4. Network Action Opcode with more AD with Format C A.1.4. Network Action Opcode with More AD with Format C
A network action may require more Ancillary Data than can fit in a A network action may require more AD than can fit in a single LSE.
single LSE. In this example, a Format D LSE is added to carry In this example, a Format D LSE is added to carry additional AD.
additional Ancillary Data.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MNA-Label=bSPL | TC |S| TTL | | MNA-Label=bSPL | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=2 | Data=0 |R|IHS|S|NASL=2 |U|NAL=0| | Opcode=2 | Data=0 |R|IHS|S|NASL=2 |U|NAL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=9 | Ancillary Data |S| AD |U|NAL=1| | Opcode=9 | Ancillary Data |S| AD |U|NAL=1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| Ancillary Data |S|Ancillary Data | |1| Ancillary Data |S|Ancillary Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: Network Action With Additional Ancillary Data Figure 10: Network Action with Additional Ancillary Data
In this example, opcode 9 requires more than one LSE's worth of In this example, opcode 9 requires more than one LSE's worth of AD,
Ancillary Data, so a Format D LSE is added. so a Format D LSE is added.
Details on the third LSE: Details on the third LSE:
Opcode=9: An opcode allocation is outside of this document Opcode=9: An opcode allocation is outside of this document
Ancillary Data: Most significant bits of Ancillary data Ancillary Data: Most significant bits of AD
AD: 4 bits of additional Ancillary Data AD: 4 bits of additional AD
Details on the fourth LSE: Details on the fourth LSE:
Ancillary Data: 22 bits of additional Ancillary data. Ancillary Data: 22 bits of additional AD.
Ancillary Data: 8 bits of additional Ancillary Data. Ancillary Data: 8 bits of additional AD.
A.2. Network Action Processing Order A.2. Network Action Processing Order
The semantics of a network action can vary widely and the results of The semantics of a network action can vary widely and the results of
processing one network action may affect the processing of a processing one network action may affect the processing of a
subsequent network action. See Section 5.5. subsequent network action. See Section 5.5.
A.2.1. Network Action Processing Order A.2.1. Network Action Processing Order
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MNA-Label=bSPL | TC |S| TTL | | MNA-Label=bSPL | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=8 | Ancillary Data |R|IHS|S|NASL=2 |U|NAL=0| | Opcode=8 | Ancillary Data |R|IHS|S|NASL=2 |U|NAL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=7 | Ancillary Data7 |S| AD7 |U|NAL=0| | Opcode=7 | Ancillary Data7 |S| AD7 |U|NAL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=1 | Flag-Based NAIs |S| NAI |U|NAL=0| | Opcode=1 | Flag-Based NAIs |S| NAI |U|NAL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: In-stack NA processing order Figure 11: In-Stack NA Processing Order
In this example, opcode 8 is processed first, then opcode 7, and then In this example, opcode 8 is processed first, then opcode 7, and then
the network action flags are processed from most significant to least the network action flags are processed from most significant to least
significant. significant.
In a different case, some Flag-Based NAIs may need to be processed In a different case, some Flag-Based NAIs may need to be processed
before opcode 7 and some Flag-Based NAIs may need to be processed before opcode 7, and some Flag-Based NAIs may need to be processed
after Opcode 7. This can be done by causing some NAIs to appear after opcode 7. This can be done by causing some NAIs to appear
earlier in the NAS. earlier in the NAS.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MNA-Label=bSPL | TC |S| TTL | | MNA-Label=bSPL | TC |S| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=8 | Ancillary Data |R|IHS|S|NASL=3 |U|NAL=0| | Opcode=8 | Ancillary Data |R|IHS|S|NASL=3 |U|NAL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=1 | 0x01 |S| NAI |U|NAL=0| | Opcode=1 | 0x01 |S| NAI |U|NAL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=7 | Ancillary Data7 |S| AD7 |U|NAL=0| | Opcode=7 | Ancillary Data7 |S| AD7 |U|NAL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=1 | 0x02 |S| NAI |U|NAL=0| | Opcode=1 | 0x02 |S| NAI |U|NAL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: Interleaving network actions Figure 12: Interleaving Network Actions
In the above example, opcode 8 is processed first, then Flag-Based In the above example, opcode 8 is processed first, then Flag-Based
NAI 0x01 is processed, then opcode 7 is processed, and finally NAI NAI 0x01 is processed, then opcode 7 is processed, and finally NAI
0x02 is processed. 0x02 is processed.
Acknowledgments Acknowledgments
The authors of this document would like to thank the MPLS Working The authors of this document would like to thank the MPLS Working
Group Open Design Team for the discussions and comments on this Group Open Design Team for the discussions and comments on this
document. The authors would also like to thank Amanda Baber for document. The authors would also like to thank Amanda Baber for
reviewing the IANA Considerations and providing many useful reviewing the IANA Considerations and providing many useful
suggestions. The authors would like to thank Loa Andersson, Stewart suggestions. The authors would like to thank Loa Andersson, Stewart
Bryant, Greg Mirsky, Joel M. Halpern and Adrian Farrel for reviewing Bryant, Greg Mirsky, Joel M. Halpern, and Adrian Farrel for reviewing
this document and providing many useful suggestions. The authors this document and providing many useful suggestions. The authors
would like to thank Fabian Ihle and Michael Menth, both from would like to thank Fabian Ihle and Michael Menth, both from the
University of Tuebingen, for reviewing and implementing the solution University of Tuebingen, for reviewing and implementing the solution
defined in this document in P4 pipeline. Also, thank you, Tarek Saad defined in this document in P4 pipeline. Also, thank you to Tarek
for the Shepherd's review, Joe Clarke for OpsDir review, Matthew Saad for the Shepherd's review, Joe Clarke for the OpsDir review,
Bocci for Rtgdir review, Derrell Piper for Secdir review, and James Matthew Bocci for the Rtgdir review, Derrell Piper for the Secdir
Guichard for the AD review, Mohamed Boucadair, Eric Vyncke, Deb review, and James Guichard for the AD review, Mohamed Boucadair, Éric
Cooley, Ketan Talaulikar, Mahesh Jethanandani for IESG review, which Vyncke, Deb Cooley, Ketan Talaulikar, and Mahesh Jethanandani for the
helped improve this document. IESG review, which helped improve this document.
Contributors Contributors
The following people have substantially contributed to this document: The following people have substantially contributed to this document:
Jisu Bhattacharya Jisu Bhattacharya
Cisco Systems, Inc. Cisco Systems, Inc.
Email: jisu@cisco.com Email: jisu@cisco.com
Bruno Decraene Bruno Decraene
skipping to change at page 32, line 6 skipping to change at line 1391
ZTE Corp. ZTE Corp.
Email: xiao.min2@zte.com.cn Email: xiao.min2@zte.com.cn
Luay Jalil Luay Jalil
Verizon Verizon
Email: luay.jalil@verizon.com Email: luay.jalil@verizon.com
Jie Dong Jie Dong
Huawei Technologies Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd. Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095 Beijing
100095
China China
Email: jie.dong@huawei.com Email: jie.dong@huawei.com
Tianran Zhou Tianran Zhou
Huawei Technologies Huawei Technologies
China China
Email: zhoutianran@huawei.com Email: zhoutianran@huawei.com
Bin Wen Bin Wen
Comcast Comcast
Email: Bin_Wen@cable.comcast.com Email: Bin_Wen@cable.comcast.com
Sami Boutros Sami Boutros
Ciena Ciena
Email: sboutros@ciena.com Email: sboutros@ciena.com
Tony Li Tony Li
Juniper Networks Juniper Networks
United States United States of America
Email: tony.li@tony.li Email: tony.li@tony.li
John Drake John Drake
Juniper Networks Juniper Networks
United States United States of America
Email: jdrake@juniper.net Email: jdrake@juniper.net
Figure 13
Authors' Addresses Authors' Addresses
Jaganbabu Rajamanickam (editor) Jaganbabu Rajamanickam (editor)
Cisco Systems, Inc. Cisco Systems, Inc.
Canada Canada
Email: jrajaman@cisco.com Email: jrajaman@cisco.com
Rakesh Gandhi (editor) Rakesh Gandhi (editor)
Cisco Systems, Inc. Cisco Systems, Inc.
Canada Canada
Email: rgandhi@cisco.com Email: rgandhi@cisco.com
Royi Zigler Royi Zigler
Broadcom Broadcom
Email: royi.zigler@broadcom.com Email: royi.zigler@broadcom.com
Haoyu Song Haoyu Song
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