| Internet-Draft | Post-Stack MNA Solution | December 2024 |
| Rajamanickam, et al. | Expires 22 June 2025 | [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 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".¶
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Copyright (c) 2024 IETF Trust and the persons identified as the document authors. All rights reserved.¶
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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 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].¶
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 [I-D.ietf-mpls-mna-fwk] and [I-D.ietf-mpls-mna-requirements] are used in this document.¶
| Abbreviation | Meaning | Reference |
|---|---|---|
| AD | Ancillary Data | [I-D.ietf-mpls-mna-requirements] |
| bSPL | Base Special Purpose Label | [RFC9017] |
| BOS | Bottom Of Stack | [RFC3032] |
| HBH | Hop-By-Hop Scope | [I-D.ietf-mpls-mna-fwk] |
| I2E | Ingress-To-Egress Scope | [I-D.ietf-mpls-mna-fwk] |
| IHS | I2E, HBH, or Select Scope | [I-D.ietf-mpls-mna-hdr] |
| ISD | In-Stack Data | [I-D.ietf-mpls-mna-requirements] |
| LSE | Label Stack Entry | [RFC3032] |
| MNA | MPLS Network Actions | [I-D.ietf-mpls-mna-fwk] |
| NAI | Network Action Indicator | [I-D.ietf-mpls-mna-requirements] |
| NAL | Network Action Length | [I-D.ietf-mpls-mna-hdr] |
| NAS | Network Action Sub-Stack | [I-D.ietf-mpls-mna-fwk] |
| NASL | Network Action Sub-Stack Length | [I-D.ietf-mpls-mna-hdr] |
| OAM | Operations, Administration, and Maintenance | [RFC6291] |
| P | Post-Stack Network Action Indicator Bit | This document |
| PSD | Post-Stack Data | [I-D.ietf-mpls-mna-requirements] and [I-D.ietf-mpls-mna-fwk] |
| PS-MNA-OP | Post-Stack MPLS Network Action Opcode | This document |
| TC | Traffic Class | [RFC5462] |
| TTL | Time To Live | [RFC3032] |
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:¶
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The below are the flags applicable to Post-Stack MNA encoding purposes defined in [I-D.ietf-mpls-mna-hdr].¶
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:¶
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.¶
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Some of the In-Stack MNA Opcodes are allocated to support Post-Stack Network Action. They are as follows.¶
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.¶
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.¶
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.¶
The above capability signaling will be added in appropriate protocols. Signaling details are outside the scope of this document.¶
This section defines the specific responsibilities for nodes along a MPLS path.¶
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.¶
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.¶
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.¶
The decapsulating node MUST remove any Post-Stack MNA it receives.¶
The security considerations in [RFC3032] also apply to this document.¶
In addition, MNA creates a new dimension in security concerns:¶
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 |
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 |
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 |
The initial assignments for this registry are:¶
| Type | Description | Reference |
|---|---|---|
| 1 | POST-STACK-HDR-MNA | This document |
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:¶
| 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 |
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 ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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).¶
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 ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.¶
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 ~ ~ ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.¶
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 | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
This is an example of Post-Stack MNA encoding, that encode 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | 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 | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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:¶
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.¶
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.¶
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.¶
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¶