Export of MPLS Network Action (MNA) Information in IPFIX

Introduction MPLS Network Actions (MNAs), as introduced in , are used to indicate actions that impact the forwarding or other processing (such as monitoring) of the packet along the Label Switched Path (LSP) of the packet and to transfer any additional data needed for these actions. Two types of MNAs solutions are defined:

MNA Sub-Stack Solution/In-stack Solution: as in , it is used to carry Network Actions and Ancillary Data in the MPLS label stack. In-stack actions and ancillary data are contained in a Network Action Sub-Stack (NAS), which is recognized by a new base Special Purpose Label (bSPL).
Post-Stack MNA Solution: as in , it is for carrying Network Actions and Ancillary Data after the MPLS label stack. The Post-Stack MPLS Header (PSMH) consists of two main parts: Post-Stack MPLS Header (PSMH) Type and Post-Stack Network Action Encoding.

When monitoring a traffic flow with MPLS MNA encoding, the following information may be required by the network operator.

What's the content of the MNAs carried in the MPLS label stack ?
What's the content of the MNAs carried after the MPLS label stack ?

In the existing IPFIX mechanism, mplsLabelStackSection(IE 316) can be used to carry a series of n octets from the MPLS label stack of a sampled packet, starting sectionOffset(IE 409) octets into the MPLS label stack, and mplsPayloadPacketSection(IE 317) carries a series of n octets from the MPLS payload of a sampled packet, starting sectionOffset(IE 409) octets into the MPLS payload. If mplsLabelStackSection(IE 316) and mplsPayloadPacketSection(IE 317) are used to carry the MNA information, additional procedures are required at the network analyzer to parse the mplsLabelStackSection or the mplsPayloadPacketSection information to see if there's any MNA information carried in it and what's the detailed MNA information. And this would bring extra complexity in the network analyzer. This document introduces new IPFIX IEs for exporting MNA information in IPFIX, covering both in-stack and post-stack MNAs.

Terminology 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 when, and only when, they appear in all capitals, as shown here. This document makes use of the terms defined in and . The following terms are used as defined in :

IPFIX
IPFIX Information Elements
Metering Process
Template
Collector
IPFIX Device

The following terms are used as defined in :

MPLS Network Action (MNA)
Label Stack Entry (LSE)
Ancillary Data (AD)
Network Action Sub-Stack (NAS)
Post-Stack Data

IPFIX IEs for MNA This section defines several Encapsulation Layer IEs for MPLS MNAs. Section 3.1 defines IEs for MNAs carried in the MPLS label stack (in-Stack MNA) and section 3.2 defines IEs for MNAs carried after the bottom of the MPLS label stack (post-Stack MNA).

IPFIX IEs for In-Stack MNAs

mplsMnaSubStack

Name:: mplsMnaSubStack
ElementID:: TBD1
Description:: The MNA Sub-Stack in the MPLS label stack with the MNA Sub-Stack Indicator excluded. This Information Element has a variable length. Multiple mplsMnaSubStack IEs can be specified within a single Template since multiple MPLS Network Action Sub-Stacks (NASes) may appear in a label stack as described in section 3 of .
Abstract Data Type:: octetArray
Data Type Semantics:: default
Additional Information:: See .
Reference:

mplsMnaLseFormatB

Name:: mplsMnaLseFormatB
ElementID:: TBD2
Description:: The LSE Format B carried in the MPLS Network Action Sub-Stack(NAS). As defined in section 5 of , the second LSE in a NAS MUST be a Format B LSE. This LSE contains an initial opcode plus additional fields that describe the NAS. The size of this Information Element is 3 octets. If multiple mplsMnaLseFormatB Information Elements are specified within a single Template, then they apply to the mplsMnaSubStack Information Elements in order: the first mplsMnaLseFormatB applies to the first mplsMnaSubStack, the second to the second, and so on. Note that the "closest" mplsMnaLseFormatB and mplsMnaSubStack Information Elements within a given Template are not necessarily related. If there are fewer mplsMnaLseFormatB Information Elements than mplsMnaSubStack Information Elements, then subsequent mplsMnaSubStack Information Elements have no LSE Format B information in this template. If there are more mplsMnaLseFormatB Information Elements than the number of mplsMnaSubStack Information Elements, then the additional mplsMnaLseFormatB Information Elements are meaningless.
Abstract Data Type:: octetArray
Data Type Semantics:: default
Additional Information:: See section 4.2 in for the definition of LSE Format B.
Reference:: This document.

IPFIX IEs for Post-Stack MNAs

mnaPostStackMplsHeaderSection

Name:: mnaPostStackMplsHeaderSection
ElementID:: TBD3
Description:: The Post-Stack MPLS Header encoded after the Bottom of the MPLS label stack. This Information Element has a variable length.
Abstract Data Type:: octetArray
Data Type Semantics:: default
Additional Information:: See section 3 of .
Reference:: This document.

mnaPostStackMplsHeaderType

Name:: mnaPostStackMplsHeaderType
ElementID:: TBD4
Description:: This IE carries the Post-Stack MPLS Header Type defined in section 3.2.1 of . 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. The size of this Information Element is 4 octets.
Abstract Data Type:: octetArray
Data Type Semantics:: default
Additional Information:: See section 3.2.1 of .
Reference:: This document.

Operational Considerations For the in-stack MNAs, as specified in , the presence of the MNA Sub-Stack Indicator is indicated by the MNA Sub-Stack Indicator which is a Base Special-Purpose MPLS Label with value TBA. To generate Flow Records with the in-Stack MNA IEs included, the metering process MUST understand the MNA Sub-Stack Indicator. If the Base Special-Purpose MPLS Label with value TBA is absent in the label stack, when the in-Stack MNA IEs appear in the template record, the corresponding field in the data record is RECOMMENDED to set to all zeros. For the post-stack MNAs, since the presence of the Post-Stack MPLS Header is indicated by the P-bit in the LSE Format B which is carried in the label stack following the MNA Sub-Stack Indicator, the metering process MUST understand the MNA Sub-Stack Indicator and the P-bit in the LSE Format B. Only when the P-bit is set SHOULD the metering process capture the post-stack MNA information after the bottom of the stack.

Security Considerations There are no additional security considerations regarding allocation of these new IPFIX IEs compared to .

IANA Considerations This document requests IANA to create new IEs under the "IPFIX Information Elements" registry available at . IPFIX Information Elements Registry

Element ID	Name	Reference
TBD1	mplsMnaSubStack	This document
TBD2	mplsMnaLseFormatB	This document
TBD3	mnaPostStackMplsHeaderSection	This document
TBD4	mnaPostStackMplsHeaderType	This document