| Internet-Draft | Post-Stack MNA Specification | June 2026 |
| Rajamanickam, et al. | Expires 25 December 2026 | [Page] |
This document defines the Post-Stack MPLS Network Action (MNA) Header Specification for carrying Network Action encodings and Ancillary Data after the MPLS label stack, based on the In-Stack MNA Specification defined in "MPLS Network Action (MNA) Sub-Stack Specification." MPLS Network Actions can be used to influence packet forwarding decisions, carry additional Operations, Administration, and Maintenance information in the MPLS packet, or perform user-defined operations. This document follows the framework specified in RFC 9789.¶
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[RFC3032] defines the encoding of the MPLS label stack, the basic structure used to define a forwarding path. There are applications that require MPLS packets to perform special network actions and carry optional Ancillary Data (AD) that can affect the packet forwarding decision or trigger Operations, Administration, and Maintenance (OAM) logging, for example as described in [RFC9791]. Ancillary Data can be used to carry additional information, for network slice purpose, as an example [RFC9791].¶
In some cases, more AD may be required than can be carried in the MPLS header, so these kinds of network actions and their AD are encoded after the Bottom of Stack (BOS). This network action with AD is called the Post-Stack (PS) MNA.¶
This document defines the Post-Stack MPLS Network Action (MNA) header specification for carrying Network Action encodings and Ancillary Data after the MPLS label stack. The specification is based on the In-Stack MNA Specification defined in [I-D.ietf-mpls-mna-hdr]. The requirements for Post-Stack network actions and Post-Stack data (PSD) are described in [RFC9613]. This document follows the framework specified in [RFC9789].¶
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.¶
The terminology defined in [RFC9789] and [RFC9613] is used in this document.¶
| Abbreviation | Meaning | Reference |
|---|---|---|
| AD | Ancillary Data | [RFC9613] |
| bSPL | Base Special Purpose Label | [RFC9017] |
| BOS | Bottom Of Stack | [RFC9789] |
| HBH | Hop-By-Hop Scope | [RFC9789] |
| I2E | Ingress-To-Egress Scope | [RFC9789] |
| IHS | I2E, HBH, or Select Scope | [I-D.ietf-mpls-mna-hdr] |
| ISD | In-Stack Data | [RFC9613] |
| LSE | Label Stack Entry | [RFC9789] |
| MNA | MPLS Network Actions | [RFC9789] |
| NAI | Network Action Indicator | [RFC9613] |
| NAL | Network Action Length | [I-D.ietf-mpls-mna-hdr] |
| NAS | Network Action Sub-Stack | [RFC9789] |
| NASL | Network Action Sub-Stack Length | [I-D.ietf-mpls-mna-hdr] |
| OAM | Operations, Administration, and Maintenance | [RFC6291] |
| P bit | Post-Stack MPLS Header Presence Bit | This document |
| PS | Post-Stack | This document |
| PSD | Post-Stack Data | [RFC9613] and [RFC9789] |
| PSMH | Post-Stack MPLS Header | This document |
| TC | Traffic Class | [RFC5462] |
| TTL | Time To Live | [RFC3032] |
Two main parts are specified to support Post-Stack MNA:¶
Note that the PSMH can be encoded for use cases other than the PS MNA. However, this document only describes the procedure related to the Post-Stack MNA.¶
Bit 20 in LSE Format B carried in the In-Stack Network Action Sub-Stack (NAS) described in [I-D.ietf-mpls-mna-hdr] is defined as the P bit in this document to indicate the presence of the PSMH in the packet after the BOS.¶
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 | 13-bit Data (Format B) |P|IHS|S| NASL |U| NAL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The following fields are carried in an NAS as defined in [I-D.ietf-mpls-mna-hdr] and shown in Figure 1.¶
The following fields are carried in an NAS as defined in [I-D.ietf-mpls-mna-hdr] and shown in Figure 1. These fields are also applicable to Post-Stack MNA as defined below:¶
The PSMH is encoded after the LSE for which the BOS bit is set, either immediately after the BOS (i.e., start offset of 0) or after any other Post-Stack headers that follow the BOS (i.e., start offset of non-zero), as described in Section 4.¶
The PSMH consists of two main parts:¶
For PS MNA, the Post-Stack MPLS Base Header is added for each scope. The Post-Stack MPLS Base Header added in a PSMH is shown in Figure 2.¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PFN |Reserve| PSMH-Len | Type = MNA Post-Stack Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format shown in Figure 3 encodes a single Post-Stack Network Action. By repeating this format, multiple Post-Stack Network Actions and their corresponding Ancillary Data can be 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP |R|R| PS-NAL | Post-Stack Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Continued Post-Stack Data ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - M | MNA Label | TC |0| TTL | N P +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ A L |Opcode=2=NoOp| 0 |1|IHS|0| NASL=0|U|NAL=0| S S +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - H ~ |0| ~ D +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ R | |1| | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - P | 0x0 |Reserve| PSMH-Len | Type = MNA Post-Stack Header |Base S +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - M | MNA-PS-OP |R|R| PS-NAL | Post-Stack Data | | H +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+PSNA | ~ Continued Post-Stack Data ~ | - +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - ~ ~ ~ Payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
An example of an MPLS packet encoding that carries an MPLS Header and a PSMH is shown in Figure 4. The example encoding contains an MPLS HDR and a PSMH with the following fields.¶
Opcode: TBA1¶
Purpose: This opcode carries the start offset of the PSMH from the BOS.¶
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 BOS in 4-octet units.¶
Scope: This opcode can be used with any scope.¶
This opcode allows the existing Post-Stack Headers [RFC9790], e.g., the Generic Control Word (0000b) [RFC4385] and G-ACh (0001b) [RFC5586], and any other PSH defined in the future to be placed immediately after the BOS.¶
If in the given NAS, the P bit is set and the PSMH Start Offset opcode is absent, the PSMH is encoded immediately after the BOS. A data value of 1 indicates that the PSMH starts at 4 octets after the BOS.¶
Opcode: TBA2¶
Purpose: This opcode carries the offset of the end of the PSMH from the BOS.¶
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 BOS in 4-octet units. A data value of 5 indicates that the PSMH ends at 20 octets after the BOS.¶
Scope: This opcode can be used with any scope.¶
The offset of the end of the PSMH and the offset of the start of the PSMH allow the NAS parser implementation to know the size of the PSMH without having to parse the PSMH (e.g., for Readable Label Depth with PSMH checks).¶
The P bit MUST be set to 1 in an In-Stack Network Action Sub-Stack when the corresponding PSMH is added in the packet.¶
By default, the PSMH starts immediately after the BOS. The offset of the PSMH that does not start immediately after the BOS is indicated using the PSMH Start Offset Opcode TBA1.¶
The P bit MUST be set to 1 when the network action with opcode TBA1 is added to the In-Stack Network Action Sub-Stack. The node that recognizes the network action with Opcode TBA1 MUST process the packet according to the U flag if the P bit is not set.¶
The P bit MUST be set to 1 when the network action with opcode TBA2 is added to the In-Stack Network Action Sub-Stack. The node that recognizes the network action with Opcode TBA2 MUST process the packet according to the U flag if the P bit is not set.¶
The node that supports the P bit, processes the Post-Stack Network Actions in the PSMH as defined in this document. Conversely, the node that does not support the P bit skips processing the PSMH altogether.¶
The Post-Stack Network Actions are processed in the same order they are encoded after the BOS. By default, they are processed after the In-Stack Network Actions in the Network Action Sub-Stack. However, Post-Stack Network Action Opcodes for applications (such as In Situ OAM (IOAM) as described in [RFC9791]) can be added to the In-Stack Network Action Sub-Stack to process Post-Stack Network Actions in a certain order with respect to the Opcodes in the In-Stack Network Action Sub-Stack.¶
The encapsulating node that is adding a PSMH MUST ensure that the decapsulating node is capable of Post-Stack MNA processing and can remove the PSMH from the packet.¶
The above capability signaling will be added in the appropriate protocols in future. Signaling details are outside the scope of this document.¶
The processing of the Network Action Sub-Stack described in [I-D.ietf-mpls-mna-hdr] are also applicable to the procedures defined in this document. This section defines the specific responsibilities for nodes along an MPLS path for processing a PSMH.¶
The encapsulating node MAY add a PSMH to the packet. The location of the header MAY be in accordance with local policy. The location may also be subject to any placement restrictions inherent in the implementation.¶
The encapsulating node MUST NOT add a PSMH to the packet if the decapsulating node does not support PSMH.¶
The encapsulating node MUST add the PSMH in the same order as the corresponding NAS in the MPLS header.¶
A transit node MAY modify the Ancillary Data in the PSMH.¶
A transit node MUST respect the Unknown Action Handling flag encoded in the corresponding NAS when processing the PSMH.¶
A transit node that removes an NAS with the Select scope, MUST also remove the associated PSMH.¶
In addition to the transit node responsibilities above, the penultimate node MUST NOT remove an Hop-By-Hop (HBH) or Ingress-To-Egress (I2E) NAS [I-D.ietf-mpls-mna-hdr] and the associated PSMH when the NAS is exposed after removing the forwarding (transport) label. This allows the egress node to receive and process the NAS and the associated PSMH.¶
The decapsulating node MUST remove the PSMHs from the packet when it removes the NASes.¶
The security considerations in [RFC3032], [RFC9789], and [I-D.ietf-mpls-mna-hdr] also apply to this document.¶
System designers must be aware that information included in Post-Stack Ancillary Data may be transmitted "in the clear." Network actions that require the exchange of sensitive data, must be defined in such a way that the data is encrypted in transit.¶
The operational considerations in [I-D.ietf-mpls-mna-hdr] also apply to this document.¶
Performance and scale assessments are outside the scope of this document; the authors of any future PS MNA application documents are encouraged to address them.¶
A PS MNA implementation MAY collect the following counters:¶
Additionally, tracking both successful invocations and failures for each specific post-stack network action is RECOMMENDED to provide granular visibility. Nodes MAY generate rate-limited notifications or alarms for significant operational events, such as sustained high rates of PS MNA packet drops or frequent encounters of malformed PSMH, to alert operators to potential issues. Comprehensive logging of PS MNA processing details and outcomes can aid in the network diagnostics and post-mortem analysis.¶
This document requests that IANA update the "Post-Stack First Nibble" registry created by [RFC9790] to include the PFN value 0x0 for the Post-Stack MPLS Header. This should be added as a new entry in the registry.¶
| Protocol | Value | Description | Reference |
|---|---|---|---|
| MPLS | 0x0 | Post-Stack MPLS Header | This document |
This document requests that IANA create a new registry with the name "Post-Stack MPLS Header Types" as follows. The registration procedures for this registry are "IETF Review", "Experimental Use", and "Private Use". The fields are "Type" (integer), "Description" (string), and "Reference" (string).¶
Note: This is a new registry group in parallel with other MPLS registries (e.g., Post-Stack First Nibble); an example location can be:¶
https://www.iana.org/assignments/post-stack-mpls-header-types/post-stack-mpls-header-types.xhtml¶
The Registration Procedure(s) for this registry are:¶
| Type | Description | Reference |
|---|---|---|
| 0 | Reserved | This document |
| 1-65520 | IETF Review | This document |
| 65521-65524 | Experimental Use | This document |
| 65525-65535 | Private Use | This document |
The initial assignments for this registry are:¶
| Type | Description | Reference |
|---|---|---|
| 0 | Reserved | This document |
| 1 | MNA Post-Stack Header Type | This document |
IANA maintains the "Network Action Opcodes" registry that will be created by [I-D.ietf-mpls-mna-hdr]. IANA is requested to perform two actions for this registry:¶
1. Assign two code points for network actions defined in this document.¶
2. Add a new column to indicate whether network action opcodes may be used In-Stack or Post-Stack.¶
The resulting entries in the registry are as follows:¶
| Opcode | Description | In-Stack Only, Post-Stack Only, In-Stack and Post-Stack | Reference |
|---|---|---|---|
| 0 | Reserved | Not Applicable | [I-D.ietf-mpls-mna-hdr] |
| 1 | Flag-Based Network Action Indicators without AD | In-Stack Only | [I-D.ietf-mpls-mna-hdr] |
| 2 | No operation Opcode | In-Stack and Post-Stack | [I-D.ietf-mpls-mna-hdr] |
| TBA1 | Post-Stack MPLS Header Start Offset | In-Stack Only | This document |
| TBA2 | Post-Stack MPLS Header End Offset | In-Stack Only | This document |
| 127 | Opcode Range Extension Beyond 127 | In-Stack and Post-Stack | [I-D.ietf-mpls-mna-hdr] |
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA Label | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Opcode=2=NoOp| 0 |1|IHS|0| NASL=0|U|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ [0| ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |1| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x0 |Reserve| PSMH-Len=1 | Type = MNA Post-Stack Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP |R|R| PS-NAL=0 | Post-Stack Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In this example, as shown in Figure 5, the NAS may encode only the presence of PSMH. The PSMH starts immediately after the BOS.¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA Label | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=TBA1 | Post-Stack Offset = 2 |1|IHS|0| NASL=0|U|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ [0| ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |1| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x0 |Reserve| PSMH-Len=1 | Type = MNA Post-Stack Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP |R|R| PS-NAL=0 | Post-Stack Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The NAS may encode the start offset of the PSMH with a non-zero value, for example, when it is after another header such as G-ACh or Control Word header. In this example, as shown in Figure 6, the PSMH starts at an offset of 8 octets after the BoS.¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA Label | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Opcode=2=NoOp| 0 |1|IHS|1| NASL=0|U|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x0 |Reserve| PSMH-Len=3 | Type = MNA Post-Stack Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP=2|R|R| PS-NAL=0 | Post-Stack Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP=3|R|R| PS-NAL=1 | Post-Stack Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Post-Stack Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Optional Payload + Padding | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In this example, as shown in Figure 7, the PSMH encodes two different Post-Stack Network Actions.¶
Details:¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA Label | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Opcode=2=NoOp| 0 |1|HBH|0| NASL=0|U|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA Label | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=TBA1 | Post-Stack Offset = 2 |1|I2E|1| NASL=0|U|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x0 |Reserve| PSMH-Len=1 | Type = MNA Post-Stack Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP=2|R|R| PS-NAL=0 | Post-Stack Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x0 |Reserve| PSMH-Len=2 | Type = MNA Post-Stack Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP=3|R|R| PS-NAL=1 | Post-Stack Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Post-Stack Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Optional Payload + Padding | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In this example, as shown in Figure 8, the PSMH encodes two differently scoped Post-Stack Network Actions. The first scope is HBH, and the second scope is I2E.¶
Details:¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA Label | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=1 | Flag-Based NAIs |1|IHS|0| NASL=0|U|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ [0| ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |1| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x0 |Reserve| PSMH-Len=1 | Type = MNA Post-Stack Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP |R|R| PS-NAL=0 | Post-Stack Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In this example as shown in Figure 9, the NAS may encode In-Stack Network Actions and indicate the presence of a PSMH. The IHS field indicates the scope of both the In-Stack and Post-Stack Network Actions.¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA Label | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode=1 | Flag-Based NAIs |0|HBH|0| NASL=0|U|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA Label | TC |0| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Opcode=2=NoOp| 0 |1|I2E|1| NASL=0|U|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 0x0 |Reserve| PSMH-Len=1 | Type = MNA Post-Stack Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP |R|R| PS-NAL=0 | Post-Stack Data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In this example as shown in Figure 10, the label stack may carry In-Stack Network Actions with HBH scope and Post-Stack Network Actions 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 Network Action with the HBH scope and the second NAS will encode the presence of I2E-scoped Post-Stack Network Action.¶
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, Haoyu Song, Adrian Farrel, Yao Liu, and Joel Halpern for reviewing this document and providing many useful comments. Thank you to Chongfeng Xie for the Opsdir review that helped improve this document.¶
The following people have substantially contributed to this document:¶
John Drake Juniper Networks United States Email: jdrake@juniper.net¶