MPLS Network Action (MNA) Header Encodings

Status of This Memo

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Copyright Notice

Copyright (c) 2022 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

[RFC3032] defines MPLS Header for carrying a stack of MPLS labels which are used to forward packets in an MPLS network. Today's new applications require the MPLS packets to carry network action indicators and optional Ancillary Data (AD) that can be used for example, in MPLS packet forwarding decision or for OAM purpose. Ancillary Data can be used to carry additional information, for example, a network slice identifier, In-Situ OAM (IOAM) data, etc. Several MNA applications are described in [I-D.ietf-mpls-mna-usecases].¶

This document defines a solution to encode MPLS Network Actions (MNA) in an MPLS Label Stack those are efficient to process in hardware. The MPLS Network Actions are encoded in the form of flags and opcodes. These MPLS Network Actions can be encoded without Ancillary Data (AD) or with In-Stack Ancillary Data (ISD) or with Post-Stack Ancillary Data (PSD) (i.e., after the Bottom of the Stack (BOS)). A new base Special Purpose Label (bSPL) (value TBA) is to be assigned to indicate the presence of MPLS Network Action Sub-Stack (MNAS) in the MPLS packet. This document addresses the MNA requirements specified in [I-D.ietf-mpls-mna-requirements]. This document follows the MNA framework specified in [I-D.ietf-mpls-mna-fwk].¶

2. Conventions Used in This Document

3. Overview

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|      TTL      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  | Flag-Based NAIs or AD   |P|IHS|S| NASL  |R|R|R|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  |         Ancillary Data        |S|4bit AD|UOH|NAL|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

MPLS Network Action (MNA) Header Encoding contains two main parts:¶

1. Network Action Sub-Stack Header:¶

• a. MNA Label to indicate the presence of Network Action Sub-Stack (NASS).¶
• b. NASS Encoding parameters indicating the NASS scope, length, ordering, etc. parameters of the NASS.¶

2. In-Stack Network Action Encoding:¶

In-Stack Network Action is encoded in the TLV format as following:¶

• a. Type - Network Action Indicator Opcode¶
• b. Length - Network Action Length (NAL)¶
• c. Value - Ancillary Data (Optional)¶

The detailed description of the MNA encoding solution is described below sections.¶

4. Network Action Sub-Stack Header

Network Action Sub-Stack Header contains MNA Label and NASS encoding parameters as described below.¶

MNA Label:¶

A new bSPL value (value TBA) is assigned to indicate the presence of the MPLS Network Action Sub-Stack (NASS).¶

Note: The TC and TTL fields of the new bSPL are not re-purposed for NASS encoding parameters, as the penultimate node on the MPLS packet path may propagate TTL and TC fields from the transport (or forwarding) LSE to the next LSE on the label stack, overwriting the TTL and TC fields of the next LSE, as specified in Section 3.5 of [RFC3443]. When the penultimate node is not aware of the MNA bSPL (value TBA) e.g., in case of non-MNA capable network, this can cause NASS parameters in the TTL of the MNA label to be corrupted.¶

NASS Encoding Parameters:¶

The TTL and TC field of the second LSE is used to encode NASS encoding parameters. The NASS encoding parameters contain the following.¶

• P-Bit (Post-Stack Network Action Presence Bit) - This bit indicates the presence of Post-Stack Network Actions.¶
• IHS (I2E, HBH and Select Scope): This 2-bit value indicates the scope of the In-Stack and Post-Stack NAIs encoded in that specific NASS.¶

• This indicates the scope (HBH / Select / I2E) of NASS for different nodes (e.g., midpoint nodes and egress node) where it needs to be processed.¶
• HBH (Hop-By-Hop) - This scope indicates that the NASS should be processed by the midpoint nodes as well.¶
• Select - This scope indicates that the NASS should be processed only on selected set of nodes.¶
• I2E (Ingress To Egress) - This scope indicates that the NASS Should be processed by the Egress node.¶
• Separate NASS Per Scope:¶
• Single NASS carries only one of the three scopes (HBH/SEL/I2E). MNA packet could carry more than one NASS scope, in those cases each scope is encoded as part of a single NASS. While encoding multiple NASS with the different scope, the I2E scope MUST be encoded after the HBH/SEL scope. This will make sure that the I2E scoped NASS is added closer to the BOS whereas HBH/SEL scoped NASS are added closer to the top of the label stack. This makes it easier for the midpoint nodes to process only the NASS with HBH scope in hardware.¶

• NASL (Network Action Sub-Stack Length):¶

• This is a 4-bit value in the TTL field. This indicates the total length number of additional LSEs (not including the MNA Label and the second LSE) used to encoding the In-Stack NAIs for that specific NASS. This value is used by the node to pop the NASS or skip the processing NASS from the label stack.¶

• R-Bits:¶

• R bits in the TTL field is Reserved for future use.¶

• O-Bit (Ordering Bit):¶

• When O-Bit is set then it indicates that the NAIs MUST be processed in the order that is encoded in the NASS. If the Node is not capable of Processing the NAIs in the order then that specific packet MUST be dropped. Processing the NAIs in order is a complex process, some of the ASICs May not be capable of processing the NAIs in order, so this option gives the flexibility for the nodes to drop these packet, just by inspecting the O-Bit.¶

The second LSEs First 20-Bit field could be used to encode In-Stack NA that requires maximum of 13 bits of Ancillary data.¶

5. In-Stack MPLS Network Action Encoding

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              Label                    | TC  |S|      TTL      |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~                                                               ~
~                                                               ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  |      Ancillary Data     |P|IHS|S| NASL  |R|R|R|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  |      Ancillary Data           |S|4bit AD|UOH|NAL|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

The In-Stack MPLS Network Action are encoded in the TLV format.¶

• a. Type - Network Action Indicator Opcode: This is the 7-Bit value used for indicating the Network Actions. This is also called as NAI-Opcode.¶
• b. Length - Network Action Length (NAL): This is the 2-Bit valued used of indicating additional number of LSEs used to encode additional Ancillary Data.¶
• c. Value - Ancillary Data (Optional): This is the optional Data that will be used while processing the NAIs.¶

The encoding format defined is flexible (e.g., stackable opcodes in desired order), extensible (by defining new NAI-Opcodes) and ASIC friendly (by using Sub-Stack Length, Opcode and Data in the same LSE). This encoding format also allows to carry the Flag-Based NAIs that do not require AD and the Flag-Based NAIs that require AD in the same packet.¶

The opcode method of identifying a specific Network Actions are common in today's hardware ASICs (Similar to any IPv4/IPv6/VxLAN header processing), so this method is easy to be adopted by the existing hardware. This will allow the hardware ASICs to serially or in-parallel process the Network Actions.¶

The Base In-Stack Network Action Encoding formats are described in detail below:¶

NAI-Opcode:¶

• This is the first 7-Bit value in the Label Field. This indicates the Network Action that needs to be executed. The Opcode value ranges from 1 to 127.¶

Ancillary Data:¶

This is the additional Ancillary Data carried to process the Network Action specified by the NAI-Opcode.¶

• The 16 bits of the Label field is used to carry the Ancillary Data¶
• Apart from the Label field, part of AD is also carried in the 4-Bit TTL field.¶
• Some applications need to change the Ancillary Data for the same flow, in those cases the data is encoded in the the TTL field of the LSE.¶

UOH (Unknown Opcode Handling):¶

• This is a 2-Bit value that defines the action that needs to be taken by a node that does not understands this corresponding opcode value. In a brown field there are possibilities that some of the midpoint nodes may not understand a specific NA opcode, this 2-Bit value will indicate the actions that needs to taken. This action could be different for different NA opcodes. When the Network Action is defined by the application, the application MUST specify the "Unknown Opcode Handling". The different type of Unknown Opcode Handling Actions are defined below.¶

NOTE: ECMP Hash Using Label Stack:¶

• If the intermediate node changes any label field value for the same flow then it may affect the ECMP Flow. So the intermediate node MUST node change the Label field value for the same flow.¶

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=1|      PSD Offset         |1|IHS|S| NASL  |R|R|R|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  |      Ancillary Data     |P|IHS|S| NASL  |R|R|R|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=2|      Flag-Based NAIs          |S| NAIs  |UOH|NAL|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|     MNA-Label=bSPL (TBA)              | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  |      Ancillary Data     |P|IHS|S| NASL=2|R|R|R|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=3|      Flag-Based NAIs          |S| NAIs  |UOH| 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|             Ancillary Data                |S|Ancillary Data |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  |      Ancillary Data     |1|IHS|S| NASL=2|R|R|R|1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=4|      Post-Stack-NAI           |S|PS-NAI |UOH| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=2|      Flag-Based NAIs          |S|4bit AD|UOH|NAL|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-OP=126  |            0x0          |P|IHS|S| NASL=0|R|R|R|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  |      Ancillary Data     |P|IHS|S| NASL=1|R|R|R|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Op=127  |Ext-NAI-Op=9 |Ancillary Data   |S|4bit AD|UOH|NAL|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

6. Post-Stack MPLS Network Action Encoding

The details of the Post-Stack Network Action Extension Header encodings are specified in [I-D.song-mpls-extension-header].¶

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                 Label                 | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  NAI-OP=126 |            0            |1|IHS|1| NASL=0|R|R|R|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~              Post-Stack Network Actions Encoding              ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~                                                               ~
~                           Data                                ~
~                                                               ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                 Label                 | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  NAI-OP=126 |            0            |1|IHS|S| NASL=1|R|R|R|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=2|        Flag-Based NAIs        |1| NAIs  |UOH|NAL|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~              Post-Stack Network Actions Encoding              ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~                                                               ~
~                           Data                                ~
~                                                               ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                 Label                 | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  NAI-OP=126 |            0            |0| 1 |S| NASL=1|R|R|R|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=2|        Flag-Based NAIs        |S| NAIs  |UOH|NAL|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  NAI-OP=126 |            0            |1| 0 |1| NASL=0|R|R|R|O|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~              Post-Stack Network Actions Encoding              ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~                                                               ~
~                           Data                                ~
~                                                               ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

7. Network Action Processing Order

Depending on the application, each NA will be processed at different stages of the ASICs pipeline. But in some cases, there may be contention between processing two NAs at the same stage of ASICs, in those cases the processing order should be maintained, so that the result of the packet forwarding and OAM data collection will be predictable.¶

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  |      Ancillary Data     |P|IHS|S| NASL=2|R|R|R|1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=7|      Ancillary Data7          |S|  AD7  |UOH| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=2|      Flag-Based NAIs          |S|  NAI  |UOH| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  |      Ancillary Data     |P|IHS|S| NASL=3|R|R|R|1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=2|        0x01                   |S|  NAI  |UOH| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=7|      Ancillary Data7          |S|  AD7  |UOH| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=2|        0x02                   |S|  NAI  |UOH| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  |      Ancillary Data     |P|IHS|S| NASL=3|R|R|R|1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=2|      Flag-Based NAIs          |S| NAIs  |UOH|NAL|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=4|      Post-Stack-NAI6          |S|PS-NAI |UOH|NAL|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=7|      Ancillary Data7          |S|  AD7  |UOH| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

8. Multiple MNA Copies in Label Stack

When adding a large size MPLS label stack, a copy of NASS with HBH and Select scope may be placed at regular stack depth throughout the MPLS label stack, with the understanding that the current copy of the NASS will eventually rise to the top of the label stack.¶

For HBH scope, every node processes the current copy of the NASS and the node that pops the forwarding label that exposes the NASS will also remove the NASS after processing the NASS assuming it supports the MNA label, and it will not forward the NASS at the top to the next node.¶

For HBH scope, the node that receives the NASS at the top of the label stack MUST remove the NASS, assuming that it supports the MNA label.¶

For I2E scope, only one copy of NASS needs to be added and it is added just before the bottom of the stack.¶

9. Node Capability Signaling

The headend Node which is encapsulating the MNA header MUST make sure that the egress Nodes removes the MNA header. The headend Node May make sure that the MNA encoded in the packet could be able to process my midpoint and egress nodes.¶

The following are the Node capabilities that are required for the headend Node to decide the encoding patten:¶

• Each participating Node MUST signal their capabilities of NASS processing like ordering, maximum NASL, etc.¶
• Each Participating Node MUST signal their capabilities of supporting each In-Stack and Post-Stack NAs and its parameters.¶
• Each Participating Node MUST signal their Maximum MPLS Stack Inspection Depth (MMSID). This will indicate the headend node to encode the MNA at a specific stack depth.¶

The above capability signaling will be added in LDP, RSVP-TE, BGP, IS-IS, OSPF, BGP-LS, etc. This is outside the scope of this document.¶

10. Security Considerations

The security considerations in [RFC3032] also apply to the procedures defined in this document.¶

The following are the security considerations that May inherit from this MNA architecture¶

• If the untrusted source encode the MNA's NASL/NAL with incorrect length, then this may affect the MNA processing and the packet could be router in an illegitimate manner.¶

11. Backward Compatibility

• For the non-MNA capable node that does not advertise the MPLS Network Action capability, the Encapsulating node MUST make sure that the MPLS Network Action Sub-Stack indicator is not at the top of the MPLS Label Stack to avoid dropping the packets. Based on the signalling, if the MPLS egress node is not capable of the processing MPLS Network Actions then it should not add MNA in the packet. In the worst case, if the non-MNA capable nodes that does not understand the new bSPL allocated then those routers will drop the packets.¶
• The MPLS Network Action Encoding format is designed to make sure that it does not alias with any Special Purpose Label.¶
• The MPLS Network Actions can co-exist with the existing GAL / G-ACh based encoding of data.¶
• The TC and TTL fields of the MNA bSPL are not re-purposed for encoding, as the penultimate node on the MPLS packet path may propagate TTL from the transport (or forwarding) label to the next label on the label stack, overwriting the TTL on the next label. When the penultimate node is not aware of the MNA bSPL (value TBA), this can cause encoding format flags in the TTL of the NASI (label TBA) label to be corrupted.¶

12. Processing In-Stack MPLS Network Actions

Encapsulating Node:¶

• MUST NOT add In-Stack MPLS Network Action Sub-Stack if the decapsulation node is not capable of In-Stack MPLS Network Action.¶
• SHOULD NOT change the IS-NAI-Opcode and the first 12 bits of the In-Stack Ancillary Data for the same packet flow to avoid ECMP path change.¶
• MAY change In-Stack Ancillary Data part present only in the TTL field for the same packet flow.¶
• MUST ensure that the penultimate node does not remove the NASS.¶

Transit Node:¶

• MUST ignore the IS-NAI-Opcode that are not supported.¶
• MUST NOT add In-Stack NASS if the decapsulation node is not capable of In-Stack MPLS Network Actions.¶
• SHOULD NOT change the IS-NAI-Opcode and the first 12 bits of the In-Stack Ancillary Data for the same packet flow.¶
• MAY change In-Stack Ancillary Data part present only in the TTL field for the same packet flow.¶
• MAY remove the IS-NAI-Opcode and its Ancillary Data for all matching packet flow.¶

Penultimate Node:¶

• MUST remove the NASS when it is exposed after removing the forwarding (transport) label.¶

Decapsulating Node:¶

• MUST remove the MPLS Network Action Sub-Stack.¶

13. IANA Considerations

Below are the IANA actions which this document is requesting.¶

The registries created by this document will be collected in a new registry grouping called "MPLS Network Action," which will be located at https://www.iana.org/assignments/mpls-network-action.¶

14. Appendix

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  |      Ancillary Data     |P|IHS|S| NASL=1|R|R|R|0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=2|      Flag-Based NAIs          |S| NAIs  |UOH| 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode  |      Ancillary Data     |P|IHS|S| NASL=2|R|R|R|0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=2|      Flag-Based NAIs          |S| NAIs  |UOH| 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1| Additional Flag-Based NAIs                |S|Flag-Based-NAIs|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=8|      Ancillary Data     |P|IHS|S| NASL=0|R|R|R|0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|      MNA-Label=bSPL (TBA)             | TC  |S|    TTL        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=1|            0            |P|IHS|S| NASL=2|R|R|R|0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NAI-Opcode=9|        Ancillary Data9        |S|  AD9  |UOH| 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|1|            Ancillary Data9                |S|Ancillary Data9|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Acknowledgments

The authors of this document would like to thank the MPLS Working Group Open Design Team for the discussions and comments on this document. The authors would also like to thank Amanda Baber for reviewing the IANA Considerations and providing many useful suggestions. The authors would like to thank Darren Dukes, Loa Andersson, Stewart Bryant and Greg Mirsky for reviewing our draft and providing many useful suggestions.¶

Contributors

The following people have substantially contributed to this document:¶

Jisu Bhattacharya
Cisco Systems, Inc.
Email: jisu@cisco.com


Bruno Decraene
Orange
Email: bruno.decraene@orange.com


Weiqiang Cheng
China Mobile
Email: chengweiqiang@chinamobile.com


Xiao Min
ZTE Corp.
Email: xiao.min2@zte.com.cn


Luay Jalil
Verizon
Email: luay.jalil@verizon.com


Jie Dong
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing  100095
China
Email: jie.dong@huawei.com


Tianran Zhou
Huawei Technologies
China
Email: zhoutianran@huawei.com


Bin Wen
Comcast
Email: Bin_Wen@cable.comcast.com


Sami Boutros
Ciena
Email: sboutros@ciena.com


Tony Li
Juniper Networks
United States
Email: tony.li@tony.li


John Drake
Juniper Networks
United States
Email: jdrake@juniper.net

Authors' Addresses