| Internet-Draft | MNA for Metadata | June 2025 |
| Liu | Expires 25 December 2025 | [Page] |
This document defines MPLS Network Action(MNA) encoding to carry metadata in SR service programming with SR-MPLS data plane.¶
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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet-Drafts is at https://datatracker.ietf.org/drafts/current/.¶
Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress."¶
This Internet-Draft will expire on 25 December 2025.¶
Copyright (c) 2025 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.¶
[I-D.ietf-spring-sr-service-programming] defines data plane functionality required to implement service segments and achieve service programming in SR-enabled MPLS and IPv6 networks. Metadata[RFC7665] provides contextual information about the data packets which traverse a programmed service path.¶
However, there's yet no standard method to carry service metadata with the SR-MPLS data plane, which make the solution for service programming in SR-MPLS incomplete¶
MPLS Network Action (MNA) [I-D.ietf-mpls-mna-fwk] is used to indicate action for Label Switched Paths (LSPs) and/or MPLS packets, and to transfer data needed for the action. [I-D.ietf-mpls-mna-hdr] defines the MNA sub-stack solution for carrying Network Action Indicators and Ancillary Data in the label stack.¶
This document defines MPLS Network Action(MNA) encoding to carry metadata in SR service programming with SR-MPLS data plane.¶
HBH: Hop-By-Hop¶
I2E: Ingress-To-Egress¶
IHS: Ingress-To-Egress (I2E), Hop-By-Hop (HBH) or Select Scope¶
ISD: In-Stack Data¶
PSD: Post-Stack Data¶
PSH: Post-Stack Header¶
LSE: Label Stack Entry¶
MPLS: Multiprotocol Label Switching¶
MNA: MPLS Network Action¶
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶
The metadata in SR-MPLS Service Programming is placed as part of the ISD block in an MPLS label stack according to the MNA encoding principles defined in [I-D.ietf-mpls-mna-hdr]. Two types of metadata for SR-MPLS service programming are defined: fixed-length service metadata and variable-length service metadata.¶
The format of fixed-length service metadata is shown as follows,¶
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 |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode = TBA1 | Service Metadata |R|IHS|S|U| NASL | NAL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1| Service Metadata |S| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1| Service Metadata |S| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1| Service Metadata |S| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
Where:¶
It should be noticed that although it is called "variable-length", the length of this service metadata MUST NOT be changed on the fly.¶
The format of variable-length service metadata is shown as follows,¶
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 |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode = TBA2 | MD Class | Type |R|IHS|S|U| NASL | NAL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~1| Service Metadata |S| ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
Where:¶
The presence of Post-Stack Header is indicated in an In-Stack Network Action Sub-stack as defined in [I-D.ietf-mpls-mna-ps-hdr] and is shown as below.¶
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 |S| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Opcode | Data |P|IHS|S|U| NASL | NAL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Label | TC |1| TTL | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Post-Stack Service Metadata ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| ~ Optional Payload + Padding ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+¶
The encoding of the post-stack variable-length service metadata is shown as follows,¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Post-Stack MNA Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| |MNA-PS-OP |R|R| PS-NAL | Service Metadata | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | Service Metadata | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|¶
Where:¶
The encoding of the post-stack variable-length service metadata is shown as follows,¶
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Post-Stack MNA Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-| |MNA-PS-OP |R|R| PS-NAL | MD Class | Type | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Service Metadata ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-|¶
Where:¶
IANA is requested to assign codepoints from its Network Action Opcodes registry (creation requested in [I-D.ietf-mpls-mna-hdr]) as specified in Table 1.¶
+------+--------------------------------+-------------+ |Opcode| Name | Reference | | | | | +------+--------------------------------+-------------+ | TBA1 | In-Stack Network Action for | | | | Fixed-Length Service Metadata |This document| | | in ISD | | +------+--------------------------------+-------------+ | TBA2 | In-Stack Network Action for | | | |Variable-Length Service Metadata|This document| | | in ISD | | +------+--------------------------------+-------------+ | TBA3 | In-Stack Network Action for |This document| | | Service Metadata in PSH | | +------+--------------------------------+-------------+¶
IANA is requested to assign codepoints for the Post-Stack Network Action for the post-stack service metadata from the Post-Stack Network Action Opcodes registry (to be created by in [I-D.ietf-mpls-mna-hdr]).¶
+------+--------------------------------+-------------+ |Opcode| Name | Reference | | | | | +------+--------------------------------+-------------+ | TBA4 | Post-Stack Network Action for |This document| | | Fixed-Length Service Metadata | | +------+--------------------------------+-------------+ | TBA5 | Post-Stack Network Action for |This document| | |Variable-Length Service Metadata| | +------+--------------------------------+-------------+¶
Security considerations discussed in [I-D.ietf-mpls-mna-fwk], [I-D.ietf-mpls-mna-hdr], [I-D.ietf-mpls-mna-ps-hdr] and [I-D.ietf-spring-sr-service-programming] apply to this document.¶