Internet DRAFT - draft-jags-mpls-ps-mna-hdr
draft-jags-mpls-ps-mna-hdr
MPLS Working Group J. Rajamanickam, Ed.
Internet-Draft R. Gandhi, Ed.
Intended status: Standards Track Cisco Systems, Inc.
Expires: 22 April 2024 R. Zigler
Broadcom
T. Li
Juniper Networks
J. Dong
Huawei Technologies
20 October 2023
Post-Stack MPLS Network Action (MNA) Solution
draft-jags-mpls-ps-mna-hdr-01
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 draft-
ietf-mpls-mna-hdr. MPLS Network Actions can be used to influence
packet forwarding decisions, carry additional OAM information in the
MPLS packet or perform user-defined operations. This document
addresses the MNA requirements specified in draft-ietf-mpls-mna-
requirements. This document follows the MNA framework specified in
draft-ietf-mpls-mna-fwk.
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
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This Internet-Draft will expire on 22 April 2024.
Copyright Notice
Copyright (c) 2023 IETF Trust and the persons identified as the
document authors. All rights reserved.
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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
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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 . . . . . . . . . . . . . 5
5.1. Post-Stack Network Action Top Header . . . . . . . . . . 6
5.2. Post-Stack Network Action Header . . . . . . . . . . . . 6
6. In-Stack Special Opcode Allocation . . . . . . . . . . . . . 7
6.1. Post-Stack Network Action Offset . . . . . . . . . . . . 7
6.2. PS-IS-NA Ordering . . . . . . . . . . . . . . . . . . . . 7
7. Node Capability Signaling . . . . . . . . . . . . . . . . . . 8
8. Processing the Network Action Sub-Stack . . . . . . . . . . . 8
8.1. Encapsulating Node Responsibilities . . . . . . . . . . . 8
8.2. Transit Node Responsibilities . . . . . . . . . . . . . . 8
8.3. Penultimate Node Responsibilities . . . . . . . . . . . . 9
8.4. Decapsulating Node Responsibilities . . . . . . . . . . . 9
9. Security Considerations . . . . . . . . . . . . . . . . . . . 9
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
10.1. Post-Stack MNA Nibble . . . . . . . . . . . . . . . . . 9
10.2. In-Stack Network Action Opcodes . . . . . . . . . . . . 10
10.3. Top Header Types Registry . . . . . . . . . . . . . . . 10
10.4. Post-Stack Network Action Opcodes . . . . . . . . . . . 11
11. Appendix A: Examples . . . . . . . . . . . . . . . . . . . . 11
11.1. Post-Stack Network Action Encoding . . . . . . . . . . . 11
11.1.1. NAS that only Indicates Post-Stack NAs . . . . . . . 11
11.1.2. NAS with both In-Stack and Post-Stack NAs . . . . . 12
11.1.3. NASes with Multiple Scopes . . . . . . . . . . . . . 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 . . . . . . . . . . . . 17
11.4.1. Post-Stack NA Processing Order . . . . . . . . . . . 17
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
12.1. Normative References . . . . . . . . . . . . . . . . . . 17
12.2. Informative References . . . . . . . . . . . . . . . . . 19
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 19
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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.
+============+=================+==================================+
|Abbreviation|Meaning | Reference |
+============+=================+==================================+
|AD |Ancillary Data | [I-D.ietf-mpls-mna-requirements] |
+------------+-----------------+----------------------------------+
|bSPL |Base Special | [RFC9017] |
| |Purpose Label | |
+------------+-----------------+----------------------------------+
|BOS |Bottom Of Stack | [RFC3032] |
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+------------+-----------------+----------------------------------+
|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 And | [RFC4377] |
| |Management | |
+------------+-----------------+----------------------------------+
|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] |
+------------+-----------------+----------------------------------+
|PSMNA |Post-Stack MPLS | This document |
| |Network Action | |
+------------+-----------------+----------------------------------+
|PS-MNA-OP |Post-Stack MPLS | This document |
| |Network Action | |
| |Opcode | |
+------------+-----------------+----------------------------------+
|TC |Traffic Class | [RFC5462] |
+------------+-----------------+----------------------------------+
|TTL |Time To Live | [RFC3032] |
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+------------+-----------------+----------------------------------+
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) 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| Res |U| NASL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1
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.
* 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.
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This consist of two main parts:
* Post-Stack Network Action Top Header
* Post-Stack Network Action Header
5.1. Post-Stack Network Action Top Header
This header is overall 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-MNA-LEN | TYPE = POST-STACK-MNA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2
* NNNN (4 bits): This first nibble identifies the start of the Post-
Stack Network Actions. A new value can be assigned by IANA (value
TBA1). Generic Associated Channel (0001b) can be used instead.
* Version (4 bits): This is Post-Stack MNA version. The initial
version will be 0.
* PS-MNA-LEN (8 bits): Post-Stack MNA Total Length in words. This
excludes the Post-Stack Top header.
* TYPE (16 bits): Type is set to POST-STACK-MNA. The type value is
an IANA allocated value.
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.
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|R| PS-NAL | PS ANCILLARY DATA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3
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* PS-MNA-OP (7 bits): Post-Stack Network Action Opcode. Opcode "0"
is reserved and other opcodes will be assigned by IANA
accordingly.
* R (2 bits): Reserved bits
* PS-NAL (7 bits): Post-Stack Network Action Length for the
respective Network Action. This value is in the order of words
excluding current word.
* PS ANCILLARY DATA (16 bits): Post-Stack Ancillary Data associated
with the 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 Network Action Offset
Opcode: TBA2
Purpose: This opcode carries the start offset of the Post-Stack
Network Action Top 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 Network
Action is encoded immediately after the MPLS BOS. A data value of 1
indicates that the PAH starts 4 octets after the BOS.
Scope: This opcode can be used with any scope.
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 if this opcode is used.
LSE Format: B, C, D (defined in [I-D.ietf-mpls-mna-hdr])
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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, and if
Format D LSEs 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.
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.
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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.
* 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 MNA Nibble
This document requests that IANA allocate a value (TBA1) for the
Post-Stack MNA Nibble (NNNN) to indicate the start of the Post-Stack
Network Actions. The reference should be this document.
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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- | This |
| | Stack Network Action Header | document |
+--------+-----------------------------+-----------+
| TBA3 | PS-IS-NA Ordering | This |
| | | document |
+--------+-----------------------------+-----------+
Table 2: In-Stack Network Action Flags With
Ancillary Data Registry
10.3. Top Header Types Registry
This document requests that IANA create a new registry with the name
"Top 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 initial assignments for this registry are:
+=============+=====================+===============+
| Type | Description | Reference |
+=============+=====================+===============+
| 0 | Reserved | This document |
+-------------+---------------------+---------------+
| 1 | POST-STACK-MNA-TYPE | This document |
+-------------+---------------------+---------------+
| 2-65520 | IETF Review | This document |
+-------------+---------------------+---------------+
| 65521-65524 | Experimental Use | This document |
+-------------+---------------------+---------------+
| 65525-65535 | Private Use | This document |
+-------------+---------------------+---------------+
Table 3: Top Header Types Registry
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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:
+=========+==================+===============+
| Opcode | Description | Reference |
+=========+==================+===============+
| 0 | Reserved | This document |
+---------+------------------+---------------+
| 1-110 | IETF Review | This document |
+---------+------------------+---------------+
| 111-114 | Experimental Use | This document |
+---------+------------------+---------------+
| 115-126 | Private Use | This document |
+---------+------------------+---------------+
Table 4: 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
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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| 0 |1|IHS|S| Res |U| NASL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |1| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N N N N|Version| PS-MNA-LEN | TYPE = POST-STACK-MNA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PS-MNA-OP |R|R| PS-NAL | 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. In this case, the P-Bit is set. 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
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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 | 0 |1|IHS|0| Res |U| NASL=1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=1 | Flag-Based NAIs |S| NAIs | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |1| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N N N N|Version| PS-MNA-LEN | TYPE = POST-STACK-MNA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PS-MNA-OP |R|R| PS-NAL | PS ANCILLARY 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. In this case, P-Bit is set. 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 Multiple Scopes
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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 | 0 |0| 1 |0| Res |U| NASL=1|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=1 | Flag-Based NAIs |0| NAIs | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label=MNA bSPL | TC |0| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=TBA2 | 0 |1| 0 |1| Res |U| NASL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N N N N|Version| PS-MNA-LEN | TYPE = POST-STACK-MNA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PS-MNA-OP |R|R| PS-NAL | PS ANCILLARY DATA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ~
~ Payload ~
~ ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: NASes with multiple scopes
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
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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 | 0 |1|IHS|1| Res |U| NASL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N N N N|Version|PS-MNA-LEN = 3 | TYPE = POST-STACK-MNA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PS-MNA-OP=2|R|R| PS-NAL=0 | PS ANCILLARY DATA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PS-MNA-OP=3|R|R| PS-NAL=1 | PS ANCILLARY DATA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PS ANCILLARY DATA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Optional Payload + Padding |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: Post-Stack NA Example
This is an example of Post-Stack MNA encoding, that encode two
different Post-Stack Network Actions.
Details:
PS-MNA-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 word to
carry its Ancillary data.
11.3. Post-Stack Network Action with two different scopes
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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 | 0 |1| H |0| Res |U| NASL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Label=MNA bSPL | TC |0| TTL |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=TBA2 | 2 |1| I |1| Res |U| NASL=0|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N N N N|Version|PS-MNA-LEN = 1 | TYPE = POST-STACK-MNA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PS-MNA-OP=2|R|R| PS-NAL=0 | PS ANCILLARY DATA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N N N N|Version|PS-MNA-LEN = 2 | TYPE = POST-STACK-MNA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PS-MNA-OP=3|R|R| PS-NAL=1 | PS ANCILLARY DATA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PS ANCILLARY DATA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Optional Payload + Padding |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Post-Stack NA Example
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:
Opcode:TBA2: This the offset of the Hop-By-Hop scoped PSD data.
This value of this opcode is "0"
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 word after the MPLS Bottom Of Stack
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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.
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 |1|IHS|0| Res |U| NASL=3|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=1 | Flag-Based NAIs |0| NAIs | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=TBA3 | Post-Stack NA=6 |0|PS-NAI | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Opcode=7 | Ancillary Data |1| AD | NAL=0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|N N N N|Version|PS-MNA-LEN = 1 | TYPE = POST-STACK-MNA |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| PS-MNA-OP=6|R|R| PS-NAL=0 | PS ANCILLARY 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 Framework", Work in Progress, Internet-
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Draft, draft-ietf-mpls-mna-fwk-05, 19 October 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
mna-fwk-05>.
[I-D.ietf-mpls-mna-requirements]
Bocci, M., Bryant, S., and J. Drake, "Requirements for
MPLS Network Actions", Work in Progress, Internet-Draft,
draft-ietf-mpls-mna-requirements-07, 18 September 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
mna-requirements-07>.
[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-
03, 6 September 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
mna-hdr-03>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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,
<https://www.rfc-editor.org/info/rfc3032>.
[RFC4377] Nadeau, T., Morrow, M., Swallow, G., Allan, D., and S.
Matsushima, "Operations and Management (OAM) Requirements
for Multi-Protocol Label Switched (MPLS) Networks",
RFC 4377, DOI 10.17487/RFC4377, February 2006,
<https://www.rfc-editor.org/info/rfc4377>.
[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, <https://www.rfc-editor.org/info/rfc4385>.
[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, <https://www.rfc-editor.org/info/rfc5462>.
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[RFC5586] Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed.,
"MPLS Generic Associated Channel", RFC 5586,
DOI 10.17487/RFC5586, June 2009,
<https://www.rfc-editor.org/info/rfc5586>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC9017] Andersson, L., Kompella, K., and A. Farrel, "Special-
Purpose Label Terminology", RFC 9017,
DOI 10.17487/RFC9017, April 2021,
<https://www.rfc-editor.org/info/rfc9017>.
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-03, 15 September 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-mpls-
mna-usecases-03>.
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.
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
Figure 10
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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
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