| Internet-Draft | Post-Stack MNA Solution | January 2026 |
| Rajamanickam, et al. | Expires 17 July 2026 | [Page] |
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 the 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 information in the MPLS packet, or perform user-defined operations. This solution document addresses the Post-Stack network action and Post-Stack data-specific requirements found in RFC 9613. 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. 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 Operations, Administration, and Maintenance (OAM) logging, for example. AD can be used to carry additional information, such as data for In Situ OAM (IOAM) as described in [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 MNA.¶
This document defines the Post-Stack MPLS Network Action (MNA) solution for carrying Network Actions and Ancillary Data after the MPLS label stack. The solution is based on the In-Stack MNA solution defined in [I-D.ietf-mpls-mna-hdr]. The solution addresses the Post-Stack network action and Post-Stack data-specific requirements found 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] are used in this document.¶
| Abbreviation | Meaning | Reference |
|---|---|---|
| AD | Ancillary Data | [RFC9613] |
| bSPL | Base Special Purpose Label | [RFC9017] |
| BOS | Bottom Of Stack | [RFC3032] |
| 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 | [RFC3032] |
| 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 |
| PSD | Post-Stack Data | [RFC9613] and [RFC9789] |
| PSMH | Post-Stack MPLS Header | This document |
| TC | Traffic Class | [RFC5462] |
| TTL | Time To Live | [RFC3032] |
The Post-Stack MNA solution contains two main parts:¶
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 Post-Stack MPLS Header 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 flags are carried in In-Stack NAS as defined in [I-D.ietf-mpls-mna-hdr] and shown in Figure 1. These flags are also applicable to Post-Stack MNA:¶
The Post-Stack MPLS Header (PSMH) for MNA is encoded after the Bottom of the Stack (BOS), 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 for MNA carries one or more Post-Stack Network Actions and their Ancillary Data.¶
The PSMH for MNA consists of two main parts:¶
The Post-Stack MPLS Header type is the top-header for all the Post-Stack Network Actions that are encoded in the PSMH for each scope as 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-HDR = 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 | TBA1 |Reserve| PSMH-LEN | TYPE = MNA-POST-STACK-HDR = 1 |PSMHT 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 Post-Stack MPLS header for the MNA Post-Stack Header type is shown in Figure 4. The encoding contains the following fields.¶
Opcode: TBA2¶
Purpose: This opcode carries the start offset of the PSMH for MNA 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 MPLS BOS in 4-octet units.¶
Scope: This opcode can be used with any scope.¶
This opcode allows the existing Post-Stack Headers (PSHs) [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 MPLS BOS. A data value of 1 indicates that the PSMH starts at 4-octets after the BOS.¶
Opcode: TBA3¶
Purpose: This opcode carries the offset of the end of the Post-Stack MPLS Header for MNA 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 MPLS BOS in 4-octet units. A data value of 5 indicates that the Post-Stack MPLS Header ends at 20-octets after the BOS.¶
Scope: This opcode can be used with any scope.¶
The offset of the end of the PSMH for MNA and the offset of the start of the PSMH for MNA 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 Post-Stack MPLS Header checks).¶
The P bit MUST be set to 1 in an In-Stack Network Action Sub-Stack when the corresponding Post-Stack MPLS Header 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 TBA2.¶
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 P bit MUST be set to 1 when the network action with opcode TBA3 is added to the In-Stack Network Action Sub-Stack. The node that recognizes the network action with Opcode TBA3 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 Post-Stack MPLS Header as defined in this document. Conversely, the node that does not support the P bit skips processing the Post-Stack MPLS Header 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 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 ingress node that is adding a Post-Stack MPLS Header MUST ensure that the egress 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. Signaling details are outside the scope of this document.¶
This section defines the specific responsibilities for nodes along an MPLS path for processing a Post-Stack MPLS Header.¶
The encapsulating node MAY add a Post-Stack MPLS Header to the packet in accordance with its policies, the placement restrictions, and the limitations.¶
The encapsulating node MUST NOT add a Post-Stack MPLS Header to the packet if the decapsulating node does not support Post-Stack MPLS Header.¶
If the encapsulating node is also a transit node, then it MUST also respect transit node responsibilities.¶
The encapsulating node MUST add the Post-Stack MPLS Header in the same order as the corresponding In-Stack NAS in the MPLS header.¶
A transit node MAY modify the Ancillary Data in the Post-Stack MPLS Header.¶
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 HBH or 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 Post-Stack MPLS Headers 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.¶
This document requests that IANA allocate a value (TBA1) for the Post-Stack MPLS Header from the "Post-Stack First Nibble" registry created by [RFC9790] to indicate the start of the PSMH after the BOS.¶
| Protocol | Value | Description | Reference |
|---|---|---|---|
| PSMH | TBA1 | 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 procedure for this registry is "IETF Review", "Experimental Use" and "Private Use". The fields are "Type" (integer), "Description" (string), and "Reference" (string).¶
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 |
The initial assignment for this registry is:¶
| Type | Description | Reference |
|---|---|---|
| 1 | Post-Stack MPLS Header Type For MNA | 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] |
| TBA2 | Offset of Start of Post-Stack MPLS Header | In-Stack Only | This document |
| TBA3 | Offset of End of Post-Stack MPLS Header | 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| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TBA1 |Reserve| PSMH-LEN=1 | TYPE = MNA-POST-STACK-HDR = 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP |R|R| PS-NAL=0 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In some cases, the NAS may encode only the presence of Post-Stack MPLS Header. The Post-Stack MPLS Header 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=TBA2 | Post-Stack Offset = 2 |1|IHS|0| NASL=0|U|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ [0| ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | |1| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TBA1 |Reserve| PSMH-LEN=1 | TYPE = MNA-POST-STACK-HDR = 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP |R|R| PS-NAL=0 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The NAS may encode the start offset of the Post-Stack MPLS Header with a non-zero value, for example, when it is after another header such as G-ACh or Control Word header. In this example, the PSMH starts at an offset of 8 bytes 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| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TBA1 |Reserve| PSMH-LEN=3 | TYPE = MNA-POST-STACK-HDR = 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This is an example where the Post-Stack MPLS Header 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=TBA2 | Post-Stack Offset = 2 |1|I2E|1| NASL=0|U|NAL=0| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TBA1 |Reserve| PSMH-LEN=1 | TYPE = MNA-POST-STACK-HDR = 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP=2|R|R| PS-NAL=0 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TBA1 |Reserve| PSMH-LEN=2 | TYPE = MNA-POST-STACK-HDR = 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP=3|R|R| PS-NAL=1 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Optional Payload + Padding | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This is an example of Post-Stack MPLS Header encoding, that encodes two different different scoped Post-Stack Network Actions. The first scope is Hop-By-Hop and the second scope is Ingress-To-Egress.¶
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| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TBA1 |Reserve| PSMH-LEN=1 | TYPE = MNA-POST-STACK-HDR = 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP |R|R| PS-NAL=0 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
In some cases, the NAS may encode In-Stack NAs and indicate the presence of a Post-Stack MPLS Header. The IHS field indicates the scope of both the In-Stack and 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TBA1 |Reserve| PSMH-LEN=1 | TYPE = MNA-POST-STACK-HDR = 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | MNA-PS-OP |R|R| PS-NAL=0 | POST-STACK DATA | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ ~ ~ Payload ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.¶
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.¶
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¶