MPLS Working Group J. Rajamanickam, Ed. Internet-Draft R. Gandhi, Ed. Intended status: Standards Track Cisco Systems, Inc. Expires: 22 June 2025 R. Zigler Broadcom T. Li Juniper Networks J. Dong Huawei Technologies 19 December 2024 Post-Stack MPLS Network Action (MNA) Solution draft-jags-mpls-ps-mna-hdr-04 Abstract This document defines the Post-Stack MPLS Network Action (MNA) solution for carrying Network Actions and Ancillary Data after the MPLS label stack based on In-Stack MNA solution defined in "MPLS Network Action (MNA) Sub-Stack Solution". MPLS Network Actions can be used to influence packet forwarding decisions, carry additional Operations, Administration, and Maintenance (OAM) information in the MPLS packet or perform user-defined operations. This solution document addresses the Post-stack network action and Post-stack data (PSD) specific requirements found in "Requirements for MPLS Network Actions". This document follows the architectural framework for the MPLS Network Actions (MNA) technologies specified in "MPLS Network Actions (MNA) Framework". Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 22 June 2025. Rajamanickam, et al. Expires 22 June 2025 [Page 1] Internet-Draft Post-Stack MNA Solution December 2024 Copyright Notice Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (https://trustee.ietf.org/ license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Revised BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Revised BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 2.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2.2. Abbreviations . . . . . . . . . . . . . . . . . . . . . . 3 3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Post-Stack Network Action Indicator . . . . . . . . . . . . . 5 5. Post-Stack Network Action Encoding . . . . . . . . . . . . . 6 5.1. Post-Stack Header . . . . . . . . . . . . . . . . . . . . 6 5.2. Post-Stack Network Action Header . . . . . . . . . . . . 6 6. In-Stack Special Opcode Allocation . . . . . . . . . . . . . 7 6.1. Post-Stack Header Offset . . . . . . . . . . . . . . . . 7 6.2. PS-IS-NA Ordering . . . . . . . . . . . . . . . . . . . . 8 7. Node Capability Signaling . . . . . . . . . . . . . . . . . . 8 8. Processing the Network Action Sub-Stack . . . . . . . . . . . 8 8.1. Encapsulating Node Responsibilities . . . . . . . . . . . 9 8.2. Transit Node Responsibilities . . . . . . . . . . . . . . 9 8.3. Penultimate Node Responsibilities . . . . . . . . . . . . 9 8.4. Decapsulating Node Responsibilities . . . . . . . . . . . 9 9. Security Considerations . . . . . . . . . . . . . . . . . . . 9 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 10.1. Post-Stack Header First Nibble . . . . . . . . . . . . . 10 10.2. In-Stack Network Action Opcodes . . . . . . . . . . . . 10 10.3. Post-Stack Header Types Registry . . . . . . . . . . . . 11 10.4. Post-Stack Network Action Opcodes . . . . . . . . . . . 11 11. Appendix A: Examples . . . . . . . . . . . . . . . . . . . . 12 11.1. Post-Stack Network Action Encoding . . . . . . . . . . . 12 11.1.1. NAS that only Indicates Post-Stack NAs . . . . . . . 12 11.1.2. NAS with both In-Stack and Post-Stack NAs . . . . . 12 11.1.3. NASes with Different ISD and PSD Scope . . . . . . . 13 11.2. Post-Stack Network Action with two Opcodes . . . . . . . 14 11.3. Post-Stack Network Action with two different scopes . . 15 11.4. Network Action Processing Order . . . . . . . . . . . . 16 Rajamanickam, et al. Expires 22 June 2025 [Page 2] Internet-Draft Post-Stack MNA Solution December 2024 11.4.1. Post-Stack NA Processing Order . . . . . . . . . . . 17 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 12.1. Normative References . . . . . . . . . . . . . . . . . . 17 12.2. Informative References . . . . . . . . . . . . . . . . . 19 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 19 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 19 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20 1. Introduction [RFC3032] defines the encoding of the MPLS label stack, the basic structure used to define a forwarding path. Forthcoming applications require MPLS packets to perform special network actions and carry optional Ancillary Data (AD) that can affect the packet forwarding decision or trigger OAM logging, for example. Ancillary Data can be used to carry additional information, such as a IOAM, Path tracing etc. Several MNA applications are described in [I-D.ietf-mpls-mna-usecases]. User-defined network actions allow new, local actions to be defined. In some cases, more Ancillary Data may required to be carried in the MPLS header, so these kind of Network Actions and its Ancillary data are encoded after the MPLS Stack. These are called as Post-Stack Data. This document defines the syntax and semantics of Post-Stack Network Actions and their corresponding Ancillary Data based on the In-Stack MNA solution defined in [I-D.ietf-mpls-mna-hdr]. This document addresses the requirements specified in [I-D.ietf-mpls-mna-requirements]. This document follows the framework specified in [I-D.ietf-mpls-mna-fwk]. 2. Conventions Used in This Document 2.1. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. 2.2. Abbreviations The terminology defined in [I-D.ietf-mpls-mna-fwk] and [I-D.ietf-mpls-mna-requirements] are used in this document. Rajamanickam, et al. Expires 22 June 2025 [Page 3] Internet-Draft Post-Stack MNA Solution December 2024 +============+=================+==================================+ |Abbreviation|Meaning | Reference | +============+=================+==================================+ |AD |Ancillary Data | [I-D.ietf-mpls-mna-requirements] | +------------+-----------------+----------------------------------+ |bSPL |Base Special | [RFC9017] | | |Purpose Label | | +------------+-----------------+----------------------------------+ |BOS |Bottom Of Stack | [RFC3032] | +------------+-----------------+----------------------------------+ |HBH |Hop-By-Hop Scope | [I-D.ietf-mpls-mna-fwk] | +------------+-----------------+----------------------------------+ |I2E |Ingress-To-Egress| [I-D.ietf-mpls-mna-fwk] | | |Scope | | +------------+-----------------+----------------------------------+ |IHS |I2E, HBH, or | [I-D.ietf-mpls-mna-hdr] | | |Select Scope | | +------------+-----------------+----------------------------------+ |ISD |In-Stack Data | [I-D.ietf-mpls-mna-requirements] | +------------+-----------------+----------------------------------+ |LSE |Label Stack Entry| [RFC3032] | +------------+-----------------+----------------------------------+ |MNA |MPLS Network | [I-D.ietf-mpls-mna-fwk] | | |Actions | | +------------+-----------------+----------------------------------+ |NAI |Network Action | [I-D.ietf-mpls-mna-requirements] | | |Indicator | | +------------+-----------------+----------------------------------+ |NAL |Network Action | [I-D.ietf-mpls-mna-hdr] | | |Length | | +------------+-----------------+----------------------------------+ |NAS |Network Action | [I-D.ietf-mpls-mna-fwk] | | |Sub-Stack | | +------------+-----------------+----------------------------------+ |NASL |Network Action | [I-D.ietf-mpls-mna-hdr] | | |Sub-Stack Length | | +------------+-----------------+----------------------------------+ |OAM |Operations, | [RFC6291] | | |Administration, | | | |and Maintenance | | +------------+-----------------+----------------------------------+ |P |Post-Stack | This document | | |Network Action | | | |Indicator Bit | | +------------+-----------------+----------------------------------+ |PSD |Post-Stack Data | [I-D.ietf-mpls-mna-requirements] | | | | and [I-D.ietf-mpls-mna-fwk] | +------------+-----------------+----------------------------------+ Rajamanickam, et al. Expires 22 June 2025 [Page 4] Internet-Draft Post-Stack MNA Solution December 2024 |PS-MNA-OP |Post-Stack MPLS | This document | | |Network Action | | | |Opcode | | +------------+-----------------+----------------------------------+ |TC |Traffic Class | [RFC5462] | +------------+-----------------+----------------------------------+ |TTL |Time To Live | [RFC3032] | +------------+-----------------+----------------------------------+ Table 1: Abbreviations 3. Overview A Flag in the In-Stack NAS header [I-D.ietf-mpls-mna-hdr] indicates the presence of the Post-Stack MNA. The Post-Stack MNA's are encoded after the MPLS Label Stack (BoS). The Post-Stack MNA encoding contains two main parts: * Post-Stack Network Action Indicator * Post-Stack Network Action Encoding 4. Post-Stack Network Action Indicator A reserved bit (21st bit from left in LSE Format B [I-D.ietf-mpls-mna-hdr]) in the In-Stack MNA header described in [I-D.ietf-mpls-mna-hdr] is used to indicate the presence of the Post- Stack Network Action. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode | Data |P|IHS|S|U| NASL | NAL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Post-Stack Network Action Indicator The below are the flags applicable to Post-Stack MNA encoding purposes defined in [I-D.ietf-mpls-mna-hdr]. * P (1 Bit) : Indicates the presence of the Post-Stack MNA * IHS (2 Bit) : Indicates the combined scope of the In-Stack and the Post-Stack Network Actions. Each scope with P bit set will have its corresponding Post-Stack MNA sub-stack. Rajamanickam, et al. Expires 22 June 2025 [Page 5] Internet-Draft Post-Stack MNA Solution December 2024 * U (1 Bit) : Indicates the combined Unknown Action Handling of the In-Stack and the Post-Stack Network Actions 5. Post-Stack Network Action Encoding The Post-Stack Network Action and its Ancillary Data are encoded after the MPLS Label Stack (BoS). The Post-Stack Network Action may carry multiple Post-Stack Network Actions and its corresponding Ancillary Data. This consist of two main parts: * Post-Stack Header * Post-Stack Network Action Header 5.1. Post-Stack Header This header is the top-level header for all the Post-Stack Network Actions that are encoded. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |N N N N|Version| PS-HDR-LEN | TYPE = POST-STACK-HDR-MNA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Post-Stack Header * NNNN (4 bits): This first nibble identifies the start of the Post- Stack Header. A new value can be assigned by IANA (value TBA1). Generic Associated Channel (0001b) or CW (0000b) can be used instead. * Version (4 bits): This is Post-Stack Header version. The initial version will be 0. * PS-HDR-LEN (8 bits): Post-Stack Header Total Length in 4-octet units. This excludes the Post-Stack Header. * TYPE (16 bits): Type is set to POST-STACK-HDR-MNA. The type value is an IANA allocated value of 1. 5.2. Post-Stack Network Action Header This header encodes a single Post-Stack Network Action. Using this scheme, multiple Post-Stack Network Action and its corresponding Ancillary data can be encoded. Rajamanickam, et al. Expires 22 June 2025 [Page 6] Internet-Draft Post-Stack MNA Solution December 2024 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PS-MNA-OP |R|U| PS-NAL | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: Post-Stack Network Action Header * PS-MNA-OP (7 bits): Post-Stack Network Action Opcode. Opcode "0" is reserved and other opcodes will be assigned by IANA accordingly. * R (1 bit): Reserved bit. * U (1 bit): Unknown Post-Stack Network Action Handling bit. * PS-NAL (7 bits): Post-Stack Network Action Length in 4-octet units. This excludes the first 4-octets starting PS-MNA-OP. * POST-STACK DATA (16 bits): Post-Stack Data associated with the Post-Stack Network Action. 6. In-Stack Special Opcode Allocation Some of the In-Stack MNA Opcodes are allocated to support Post-Stack Network Action. They are as follows. 6.1. Post-Stack Header Offset Opcode: TBA2 Purpose: This opcode carries the start offset of the Post-Stack Header. LSE Format: B or C (defined in [I-D.ietf-mpls-mna-hdr]) Data: The data value of the LSE contains the offset from the MPLS BOS in units of 4 octets. This allows the Generic Control Word (0000b) [RFC4385] and G-ACh (0001b) [RFC5586] fields to be placed immediately after the BOS. In the absence of this opcode, the Post-Stack Header is encoded immediately after the MPLS BOS. A data value of 1 indicates that the Post-Stack Header starts 4 octets after the BOS. Scope: This opcode can be used with any scope. Rajamanickam, et al. Expires 22 June 2025 [Page 7] Internet-Draft Post-Stack MNA Solution December 2024 6.2. PS-IS-NA Ordering Opcode: TBA3 Purpose: In cases where the ordering of network action is significant and where some of the network actions reside in Post-Stack Network Action, this opcode can be used to insert Post-Stack network actions into the order of execution. The 'P' bit and 'O' bit MUST be set in the NAS's Format B LSE [I-D.ietf-mpls-mna-hdr]) if this opcode is used. LSE Format: B, C, D (defined in [I-D.ietf-mpls-mna-hdr]) Data: The data field contains one or more 7-bit Post-Stack MNA Opcode. When used with LSE Format B, only one PS MNA Opcode is carried. Two PS MNA opcodes can be carried in a Format C LSE. If Format D LSEs [I-D.ietf-mpls-mna-hdr]) are used, each may carry up to three PS MNA opcodes. The PS MNA opcodes are the stored concatenated in the most significant bits of the data field. If multiple indicators are carried, the most significant PS MNA opcode is evaluated to the least significant. PS MNA opcodes do not span LSEs. If some PS MNA opcode positions are not to be used, then the opcode should be set to value 0. Scope: This opcode can be used with any scope. 7. Node Capability Signaling The ingress node which is adding a Post-Stack MNA MUST make sure that the egress node is capable of MNA and removes the Post-Stack MNA. * Each participating node MUST signal the network actions that it supports. * Each participating node MUST signal its Maximum Post-Stack MNA Length that could encoded. The above capability signaling will be added in appropriate protocols. Signaling details are outside the scope of this document. 8. Processing the Network Action Sub-Stack This section defines the specific responsibilities for nodes along a MPLS path. Rajamanickam, et al. Expires 22 June 2025 [Page 8] Internet-Draft Post-Stack MNA Solution December 2024 8.1. Encapsulating Node Responsibilities The encapsulating node MAY add Post-Stack MNA to the packet in accordance with its policies, the placement restrictions, and the limitations. The encapsulating node MUST NOT add a Post-Stack MNA to the packet if the decapsulation node does not support Post-Stack MNA. If the encapsulating node is also a transit node, then it MUST also respect transit node responsibilities. 8.2. Transit Node Responsibilities A transit node MAY change the Ancillary Data in the Post-Stack MNA. A transit node MUST respect the Unknown Action Handling value encoded in the NAS. A node that removes the last copy of a NAS that has the P bit set MUST remove all Post-Stack Network Actions. 8.3. Penultimate Node Responsibilities In addition to the transit node responsibilities above, the penultimate node MUST NOT remove the last copy of a HBH or I2E NAS when it is exposed after removing the forwarding (transport) label. This allows the egress node to process the NAS. 8.4. Decapsulating Node Responsibilities The decapsulating node MUST remove any Post-Stack MNA it receives. 9. Security Considerations The security considerations in [RFC3032] also apply to this document. In addition, MNA creates a new dimension in security concerns: * The actions of an encapsulating node can affect any or all of the nodes along the path. In the most common and benign situations, such as a syntactically incorrect packet, this could result in packet loss or corruption. Rajamanickam, et al. Expires 22 June 2025 [Page 9] Internet-Draft Post-Stack MNA Solution December 2024 * The semantics of a network action are unbounded and may be insecure. A network action could be defined that made arbitrary changes to the memory of the forwarding router, which could then be used by the encapsulating node to compromise every MNA capable router in the network. The IETF needs to ensure that only secure network actions are defined. * The MNA architecture supports locally defined network actions. For such actions, there will be limited oversight to ensure that the semantics do not create security issues. Implementors and network operators will need to ensure that locally defined network actions do not compromise the security of the network. 10. IANA Considerations 10.1. Post-Stack Header First Nibble This document requests that IANA allocate a value (TBA1) for the Post-Stack Header Nibble (NNNN) from the registry "Post-Stack First Nibble" created by [I-D.ietf-mpls-1stnibble] to indicate the start of the Post-Stack Header. +=======+================================+===============+ | Value | Description | Reference | +=======+================================+===============+ | TBA1 | Post-Stack Header First Nibble | This document | +-------+--------------------------------+---------------+ Table 2: Post-Stack First Nibble Registry 10.2. In-Stack Network Action Opcodes The In-Stack Network Action Opcodes for In-Stack Network Action Opcode registry (to be created by in [[I-D.ietf-mpls-mna-hdr]])are defined in the document as follows. +========+======================================+===============+ | Opcode | Description | Reference | +========+======================================+===============+ | TBA2 | Offset of start of Post-Stack Header | This document | +--------+--------------------------------------+---------------+ | TBA3 | PS-IS-NA Ordering | This document | +--------+--------------------------------------+---------------+ Table 3: In-Stack Network Action Flags With Ancillary Data Registry Rajamanickam, et al. Expires 22 June 2025 [Page 10] Internet-Draft Post-Stack MNA Solution December 2024 10.3. Post-Stack Header Types Registry This document requests that IANA create a new registry with the name "Post-Stack Header Types". The registration procedure for this registry is "IETF Review". The fields are "Type" (integer), "Description" (string), and "Reference" (string). Type is an integer 0-65535. The assignments for this registry are: +=============+==============================+===============+ | Type | Description | Reference | +=============+==============================+===============+ | 0 | Reserved, not to be assigned | This document | +-------------+------------------------------+---------------+ | 1-65520 | IETF Review | This document | +-------------+------------------------------+---------------+ | 65521-65524 | Experimental Use | This document | +-------------+------------------------------+---------------+ | 65525-65535 | Private Use | This document | +-------------+------------------------------+---------------+ Table 4: Post-Stack Header Types Registry The initial assignments for this registry are: +======+====================+===============+ | Type | Description | Reference | +======+====================+===============+ | 1 | POST-STACK-HDR-MNA | This document | +------+--------------------+---------------+ Table 5: Post-Stack Header Types 10.4. Post-Stack Network Action Opcodes This document requests that IANA create a new registry with the name "Post-Stack Network Action Opcodes". The registration procedure for this registry is "IETF Review". The fields are "Opcode" (integer), "Description" (string), and "Reference" (string). Opcode is an integer 0-127. The initial assignments for this registry are: Rajamanickam, et al. Expires 22 June 2025 [Page 11] Internet-Draft Post-Stack MNA Solution December 2024 +=========+==============================+===============+ | Opcode | Description | Reference | +=========+==============================+===============+ | 0 | Reserved, not to be assigned | This document | +---------+------------------------------+---------------+ | 1-110 | IETF Review | This document | +---------+------------------------------+---------------+ | 111-114 | Experimental Use | This document | +---------+------------------------------+---------------+ | 115-126 | Private Use | This document | +---------+------------------------------+---------------+ Table 6: Post-Stack Network Action Opcodes Registry 11. Appendix A: Examples 11.1. Post-Stack Network Action Encoding 11.1.1. NAS that only Indicates Post-Stack NAs 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label=MNA bSPL | TC |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=TBA2| Offset = 0 |P|IHS|S|U| NASL=0|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |1| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |N N N N|Version| PS-HDR-LEN=1 | TYPE = POST-STACK-HDR-MNA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PS-MNA-OP |R|U| PS-NAL=0 | PS ANCILLARY DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: NAS encoding only Post-Stack NAs In some cases, the NAS may encode only the presence of Post-Stack NAs. The IHS field indicates the scope of the Post-Stack NAs (I2E, HBH, Select). 11.1.2. NAS with both In-Stack and Post-Stack NAs Rajamanickam, et al. Expires 22 June 2025 [Page 12] Internet-Draft Post-Stack MNA Solution December 2024 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label=MNA bSPL | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=TBA2 | Offset = 0 |P|IHS|0|U| NASL=1|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=1 | Flag-Based NAIs |S|U| NAIs |NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |1| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |N N N N|Version| PS-HDR-LEN=1 | TYPE = POST-STACK-HDR-MNA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PS-MNA-OP |R|U| PS-NAL=0 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: NAS with In-Stack and Post-Stack NAs In some cases, the NAS may encode In-Stack NAs and indicate the presence of Post-Stack NAs. The NASL is set to "1", indicating the presence of one additional LSE. The IHS field indicates the scope of both the In-Stack and Post-Stack NAs. 11.1.3. NASes with Different ISD and PSD Scope Rajamanickam, et al. Expires 22 June 2025 [Page 13] Internet-Draft Post-Stack MNA Solution December 2024 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label=MNA bSPL | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=1 | Flag-Baed NAIs |P|HBH|0|U| NASL=0|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label=MNA bSPL | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=TBA2 | Offset = 0 |P|I2E|1|U| NASL=0|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |N N N N|Version| PS-HDR-LEN=1 | TYPE = POST-STACK-HDR-MNA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PS-MNA-OP |R|U| PS-NAL=0 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: NASes with Different ISD and PSD Scope In some cases the label stack may need to carry In-Stack NAs with Hop-By-Hop scope and Post-Stack NAs with I2E scope. In this case, there will be two NASes in the label stack. In this case, the first NAS will encode the In-Stack NA with the Hop-By-Hop scope and the second NAS will encode the presence of I2E scoped Post-Stack NAs. 11.2. Post-Stack Network Action with two Opcodes Rajamanickam, et al. Expires 22 June 2025 [Page 14] Internet-Draft Post-Stack MNA Solution December 2024 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label=MNA bSPL | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=TBA2 | Offset = 0 |P|IHS|1|U| NASL=0|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |N N N N|Version| PS-HDR-LEN=3 | TYPE = POST-STACK-HDR-MNA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PS-MNA-OP=2|R|U| PS-NAL=0 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PS-MNA-OP=3|R|U| PS-NAL=1 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Optional Payload + Padding | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7: Post-Stack NA Example with two Opcodes This is an example of Post-Stack MNA encoding, that encode two different Post-Stack Network Actions. Details: PS-HDR-LEN=3: This is the Total Length of Post-Stack MNAs. PS-MNA-OP=2: Post-Stack MNA Opcode "2". PS-NAL=0: Post-Stack Network Action does not contain any additional data. PS-MNA-OP=3: Post-Stack MNA Opcode "3". PS-NAL=1: Post-Stack Network Action contains 1 additional 4-octet Ancillary data. 11.3. Post-Stack Network Action with two different scopes Rajamanickam, et al. Expires 22 June 2025 [Page 15] Internet-Draft Post-Stack MNA Solution December 2024 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label=MNA bSPL | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=TBA2 | Offset = 0 |P|HBH|0|U| NASL=0|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label=MNA bSPL | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=TBA2 | Offset = 2 |P|I2E|1|U| NASL=0|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |N N N N|Version| PS-HDR-LEN=1 | TYPE = POST-STACK-HDR-MNA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PS-MNA-OP=2|R|U| PS-NAL=0 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |N N N N|Version| PS-HDR-LEN=2 | TYPE = POST-STACK-HDR-MNA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PS-MNA-OP=3|R|U| PS-NAL=1 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Optional Payload + Padding | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8: Post-Stack NA Example with two Different Scopes This is an example of Post-Stack MNA encoding, that encode two different different scoped Post-Stack Network Actions. The first scope is Hop-By-Hop and the second scope is Ingress-To-Egress scoped PSD data. Details: First Opcode:TBA2: This the offset of the Hop-By-Hop scoped PSD data. This value of this opcode is "0" Second Opcode:TBA2: This the offset of the Ingress-To-Egress scoped PSD data. This value of this opcode is "2" (i.e) the PSD stack starts from second 4-octet unit after the MPLS Bottom Of Stack 11.4. Network Action Processing Order The semantics of a network action can vary widely and the results of processing one network action may affect the processing of a subsequent network action. Rajamanickam, et al. Expires 22 June 2025 [Page 16] Internet-Draft Post-Stack MNA Solution December 2024 11.4.1. Post-Stack NA Processing Order By default, Post-Stack NAs follow the ordering of the encoding. However, the PS-IS-NA ordering opcode can be used to override the default ordering and interleave Post-Stack network actions with In- Stack network actions. In some cases, Post-Stack NAs needs to be processed before In-Stack NAs. This section shows how to prioritize the Post-Stack NAs over In-Stack NAs. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label=MNA bSPL | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=8 | Ancillary Data |P|IHS|0|U| NASL=3|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=1 | Flag-Based NAIs |0|U| NAIs |NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=TBA3 | Post-Stack NA=6 |0|U|PS-NAI |NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=7 | Ancillary Data |1|U| AD |NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |N N N N|Version| PS-HDR-LEN=1 | TYPE = POST-STACK-HDR-MNA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PS-MNA-OP=6 |R|U| PS-NAL=0 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 9: Post-Stack and In-Stack NA processing order In the above example, opcode 8 is processed first, then the Flag- Based NAIs, followed by Post-Stack NA Opcode 6, and finally opcode 7. 12. References 12.1. Normative References [I-D.ietf-mpls-mna-fwk] Andersson, L., Bryant, S., Bocci, M., and T. Li, "MPLS Network Actions (MNA) Framework", Work in Progress, Internet-Draft, draft-ietf-mpls-mna-fwk-14, 2 December 2024, . [I-D.ietf-mpls-mna-requirements] Bocci, M., Bryant, S., and J. Drake, "Requirements for Solutions that Support MPLS Network Actions (MNA)", Work Rajamanickam, et al. Expires 22 June 2025 [Page 17] Internet-Draft Post-Stack MNA Solution December 2024 in Progress, Internet-Draft, draft-ietf-mpls-mna- requirements-16, 30 May 2024, . [I-D.ietf-mpls-mna-hdr] Rajamanickam, J., Gandhi, R., Zigler, R., Song, H., and K. Kompella, "MPLS Network Action (MNA) Sub-Stack Solution", Work in Progress, Internet-Draft, draft-ietf-mpls-mna-hdr- 10, 5 December 2024, . [I-D.ietf-mpls-1stnibble] Kompella, K., Bryant, S., Bocci, M., Mirsky, G., Andersson, L., and J. Dong, "IANA Registry and Processing Recommendations for the First Nibble Following a Label Stack", Work in Progress, Internet-Draft, draft-ietf-mpls- 1stnibble-13, 5 December 2024, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y., Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001, . [RFC4385] Bryant, S., Swallow, G., Martini, L., and D. McPherson, "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for Use over an MPLS PSN", RFC 4385, DOI 10.17487/RFC4385, February 2006, . [RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching (MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic Class" Field", RFC 5462, DOI 10.17487/RFC5462, February 2009, . [RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., "MPLS Generic Associated Channel", RFC 5586, DOI 10.17487/RFC5586, June 2009, . Rajamanickam, et al. Expires 22 June 2025 [Page 18] Internet-Draft Post-Stack MNA Solution December 2024 [RFC6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu, D., and S. Mansfield, "Guidelines for the Use of the "OAM" Acronym in the IETF", BCP 161, RFC 6291, DOI 10.17487/RFC6291, June 2011, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC9017] Andersson, L., Kompella, K., and A. Farrel, "Special- Purpose Label Terminology", RFC 9017, DOI 10.17487/RFC9017, April 2021, . 12.2. Informative References [I-D.ietf-mpls-mna-usecases] Saad, T., Makhijani, K., Song, H., and G. Mirsky, "Use Cases for MPLS Network Action Indicators and MPLS Ancillary Data", Work in Progress, Internet-Draft, draft- ietf-mpls-mna-usecases-15, 23 September 2024, . Acknowledgments The authors would like to thank the authors and contributors of the draft-ietf-mpls-mna-hdr as this document borrows some text from the earlier version of that document. The authors would like to thank Greg Mirsky, Loa Andersson for reviewing this document and providing many useful comments. Contributors The following people have substantially contributed to this document: Jisu Bhattacharya Cisco Systems, Inc. Email: jisu@cisco.com John Drake Juniper Networks United States Email: jdrake@juniper.net Rajamanickam, et al. Expires 22 June 2025 [Page 19] Internet-Draft Post-Stack MNA Solution December 2024 Authors' Addresses Jaganbabu Rajamanickam (editor) Cisco Systems, Inc. Canada Email: jrajaman@cisco.com Rakesh Gandhi (editor) Cisco Systems, Inc. Canada Email: rgandhi@cisco.com Royi Zigler Broadcom Email: royi.zigler@broadcom.com Tony Li Juniper Networks Email: tony.li@tony.li Jie Dong Huawei Technologies Beijing China Email: jie.dong@huawei.com Rajamanickam, et al. 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