Internet-Draft Export of BIER in IPFIX January 2026
Liu & Lin Expires 26 July 2026 [Page]
Workgroup:
OPSAWG
Internet-Draft:
draft-ll-opsawg-ipfix-bier-00
Published:
Intended Status:
Standards Track
Expires:
Authors:
Y. Liu
China Mobile
C. Lin
New H3C Technologies

Export of BIER Information in IP Flow Information Export (IPFIX)

Abstract

This document introduces new IP Flow Information Export (IPFIX) Information Elements (IEs) to identify a set of information related to Bit Index Explicit Replication (BIER) such as data contained in BIER header that traffic is being forwarded with.

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 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 26 July 2026.

▲

Table of Contents

1. Introduction

[RFC8279] introduces a novel multicast data packet forwarding architecture known as "Bit Index Explicit Replication" (BIER). This architecture achieves optimal forwarding within a "multicast domain" without relying on explicit tree-building protocols or requiring intermediate nodes to maintain per-flow state. Currently, BIER technology has been widely adopted in modern data centers and large-scale networks, significantly enhancing the efficiency and scalability of multicast transmission.

[RFC8296] defines the encapsulation of BIER header that provides the information needed to support the BIER forwarding procedures.

This document specifies new IPFIX Information Elements (IEs) within the "IPFIX Information Elements" registry [RFC7012], for BIER purposes. These IEs are used to export the main parameters of BIER flow.

2. 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 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.

This document makes use of the terms defined in [RFC7011].

The following terms are used as defined in [RFC7011]:

The following terms are used as defined in [RFC8296]:

3. New IPFIX BIER Information Elements

This section specifies the new IPFIX BIER IEs.

bierBIFTidSection
The BIFT-id, TC, and S fields defined in the initial three octets of the BIER header (Section 2 of [RFC8296]).
bierTTL
The value of the TTL field in the BIER header (Section 2 of [RFC8296]). This IE indicates the incoming Time to Live (TTL) when a BIER packet is received.
bierFromMPLSNetwork
This IE indicates whether the BIER packet is from an MPLS network.
bierVersion
The version of the BIER header (Section 2 of [RFC8296]).
bierBSL
The value of the BSL field in the BIER header (Section 2 of [RFC8296]). This IE indicates the length in bits of the BitString defined in the BIER header (Section 2 of [RFC8296]).
bierEntropy
The value of the Entropy field in the BIER header (Section 2 of [RFC8296]). It is can be used for load-balancing purposes.
bierOAMSection
The OAM and Rsv field from the BIER header (Section 2 of [RFC8296]).
bierDSCP
The value of the DSCP field in the BIER header (Section 2 of [RFC8296]). In Non-MPLS networks, it is used to hold a Differentiated Services Codepoint [RFC2474].
bierNextProtocol
The next protocol defined in the Proto field of the BIER header (Section 2 of [RFC8296]). It identifies the type of the payload following the BIER header.
bierBFIRid
The value of the BFIR-id field in the BIER header (Section 2 of [RFC8296]). It indicates the BFR-id of the BFIR in the SD to which the packet has been assigned.
bierBitString
The BitString field defined in the BIER header (Section 2 of [RFC8296]). Together with the packet's SI and SD, it identifies the destination BFERs for this packet.

4. Sample Use Cases

The IPFIX IEs defined in the Section 3, and some existing IP packet header information [IANA-IPFIX] provide answers to the following questions (amongst others).

5. Security Considerations

There exists no extra security considerations other than those already discussed in Section 11 of [RFC7011] and Section 8 of [RFC7012].

6. IANA Considerations

6.1. IPFIX Information Elements

This document requests IANA to add new IPFIX BIER IEs to the "IPFIX Information Elements" registry [RFC7012] available at [IANA-IPFIX].

Table 1 lists the new IPFIX BIER IEs:

      +============+=============================+===============+
      | Element ID | Name                        | Reference     |
      +============+=============================+===============+
      | TBD1       | bierBIFTidSection           | This document |
      +------------+-----------------------------+---------------+
      | TBD2       | bierTTL                     | This document |
      +------------+-----------------------------+---------------+
      | TBD3       | bierFromMPLSNetwork         | This document |
      +------------+-----------------------------+---------------+
      | TBD4       | bierVersion                 | This document |
      +------------+-----------------------------+---------------+
      | TBD5       | bierBSL                     | This document |
      +------------+-----------------------------+---------------+
      | TBD6       | bierEntropy                 | This document |
      +------------+-----------------------------+---------------+
      | TBD7       | bierOAMSection              | This document |
      +------------+-----------------------------+---------------+
      | TBD8       | bierDSCP                    | This document |
      +------------+-----------------------------+---------------+
      | TBD9       | bierNextProtocol            | This document |
      +------------+-----------------------------+---------------+
      | TBD10      | bierBFIRid                  | This document |
      +------------+-----------------------------+---------------+
      | TBD11      | bierBitString               | This document |
      +------------+-----------------------------+---------------+

   Table 1: New BIER IEs in the "IPFIX Information Elements" Registry

6.1.1. bierBIFTidSection

ElementID:
TBD1
Name:
bierBIFTidSection
Abstract Data Type:
octetArray
Data Type Semantics:
identifier
Status:
current
Description:

The BIFT-id, TC, and S fields defined in the initial three octets of the BIER header. The size of this information Element is 3 octets.

 0                   1                   2
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|              BIFT-id                  | TC  |S|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

BIFT-id: BIFT id, 20 bits
TC:      Traffic Class, 3 bits
S:       Set to 1, 1 bit
Additional Information:
See Section 2 of [RFC8296] for more details about the BIFT-id, TC, and S fields.
Reference:
[this document]

6.1.2. bierTTL

ElementID:
TBD2
Name:
bierTTL
Abstract Data Type:
unsigned8
Data Type Semantics:
default
Status:
current
Description:

The value of the TTL field in the BIER header. This Information Element indicates the incoming TTL when a BIER packet is received.

Units:
hops
Additional Information:
See Section 2 of [RFC8296] for more details about the TTL fields.
Reference:
[this document]

6.1.3. bierFromMPLSNetwork

ElementID:
TBD3
Name:
bierFromMPLSNetwork
Abstract Data Type:
boolean
Data Type Semantics:
default
Status:
current
Description:

This IE indicates whether the BIER packet is from an MPLS network.

Additional Information:
In MPLS networks, the Nibble field of the BIER header MUST be set to the binary value 0101. In Non-MPLS networks, the Nibble field is set to the binary value 0000. Therefore, the Nibble field can be used to identify whether a BIER packet is from an MPLS network. See Section 2 of [RFC8296] for more details.
Reference:
[this document]

6.1.4. bierVersion

ElementID:
TBD4
Name:
bierVersion
Abstract Data Type:
unsigned8
Data Type Semantics:
identifier
Status:
current
Description:

The version value of the Ver field in the BIER header.

This Information Element encodes only the 4 bits of the Ver field. Therefore, its value may range from 0 to 0xF.

Additional Information:
See Section 2 of [RFC8296] for more details about the Ver field of the BIER header.
Reference:
[this document]

6.1.5. bierBSL

ElementID:
TBD5
Name:
bierBSL
Abstract Data Type:
unsigned8
Data Type Semantics:
default
Status:
current
Description:

The value of the BSL field in the BIER header. This Information Element indicates the length in bits of the BitString defined in the BIER header.

This Information Element encodes only the 4 bits of the BSL field. Therefore, its value may range from 0 to 15.

Additional Information:
See Section 2 of [RFC8296] for more details about the BSL field of the BIER header.
Reference:
[this document]

6.1.6. bierEntropy

ElementID:
TBD6
Name:
bierEntropy
Abstract Data Type:
unsigned32
Data Type Semantics:
default
Status:
current
Description:

The value of the Entropy field in the BIER header. This Information Element indicates the function of load-balancing.

This Information Element encodes only the 20 bits of the Entropy field. Therefore, its value may range from 0 to 0xFFFFF.

Additional Information:
See Section 2 of [RFC8296] for more details about the Entropy field of the BIER header.
Reference:
[this document]

6.1.7. bierOAMSection

ElementID:
TBD7
Name:
bierOAMSection
Abstract Data Type:
unsigned8
Data Type Semantics:
flags
Status:
current
Description:

The OAM and Rsv field from the BIER header.

 0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|OAM|Rsv|no care|
+-+-+-+-+-+-+-+-+

Bits 0-1: OAM field.
Bits 2-3: Rsv field, unused.
Bits 4-7: No care, value is irrelevent.
Additional Information:
See Section 2 of [RFC8296] for more details about the OAM and Rsv field of the BIER header.
Reference:
[this document]

6.1.8. bierDSCP

ElementID:
TBD8
Name:
bierDSCP
Abstract Data Type:
unsigned8
Data Type Semantics:
identifier
Status:
current
Description:

The value of the DSCP field in the BIER header. In Non-MPLS networks, it is used to hold a Differentiated Services Codepoint.

This Information Element encodes only the 6 bits of the DSCP field. Therefore, its value may range from 0 to 63.

Additional Information:
See Section 2 of [RFC8296] for more details about the DSCP field of the BIER header.
Reference:
[this document]

6.1.9. bierNextProtocol

ElementID:
TBD9
Name:
bierNextProtocol
Abstract Data Type:
unsigned8
Data Type Semantics:
identifier
Status:
current
Description:

The next protocol defined in the Proto field of the BIER header. This Information Element identifies the type of the payload following the BIER header.

This Information Element encodes only the 6 bits of the Proto field. Therefore, its value may range from 0 to 63.

Additional Information:
See Section 2 of [RFC8296] for more details about the Proto field of the BIER header.
Reference:
[this document]

6.1.10. bierBFIRid

ElementID:
TBD10
Name:
bierBFIRid
Abstract Data Type:
unsigned16
Data Type Semantics:
identifier
Status:
current
Description:

The value of the BFIR-id field in the BIER header. This Information Element identifies the BFR-id of the BFIR in the SD to which the packet has been assigned.

Additional Information:
See Section 2 of [RFC8296] for more details about the BFIR-id field of the BIER header.
Reference:
[this document]

6.1.11. bierBitString

ElementID:
TBD11
Name:
bierBitString
Abstract Data Type:
octetArray
Data Type Semantics:
identifier
Status:
current
Description:

The BitString field defined in the BIER header. Together with the packet's SI and SD, this information Element identifies the destination BFERs for this packet.

Additional Information:
See Section 2 of [RFC8296] for more details about the BitString field of the BIER header.
Reference:
[this document]

7. References

7.1. Normative References

[RFC2119]
Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, , <https://www.rfc-editor.org/info/rfc2119>.
[RFC2474]
Nichols, K., Blake, S., Baker, F., and D. Black, "Definition of the Differentiated Services Field (DS Field) in the IPv4 and IPv6 Headers", RFC 2474, DOI 10.17487/RFC2474, , <https://www.rfc-editor.org/info/rfc2474>.
[RFC7011]
Claise, B., Ed., Trammell, B., Ed., and P. Aitken, "Specification of the IP Flow Information Export (IPFIX) Protocol for the Exchange of Flow Information", STD 77, RFC 7011, DOI 10.17487/RFC7011, , <https://www.rfc-editor.org/info/rfc7011>.
[RFC7012]
Claise, B., Ed. and B. Trammell, Ed., "Information Model for IP Flow Information Export (IPFIX)", RFC 7012, DOI 10.17487/RFC7012, , <https://www.rfc-editor.org/info/rfc7012>.
[RFC8174]
Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, , <https://www.rfc-editor.org/info/rfc8174>.
[RFC8279]
Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Przygienda, T., and S. Aldrin, "Multicast Using Bit Index Explicit Replication (BIER)", RFC 8279, DOI 10.17487/RFC8279, , <https://www.rfc-editor.org/info/rfc8279>.
[RFC8296]
Wijnands, IJ., Ed., Rosen, E., Ed., Dolganow, A., Tantsura, J., Aldrin, S., and I. Meilik, "Encapsulation for Bit Index Explicit Replication (BIER) in MPLS and Non-MPLS Networks", RFC 8296, DOI 10.17487/RFC8296, , <https://www.rfc-editor.org/info/rfc8296>.

7.2. Informative References

[IANA-IPFIX]
"IP Flow Information Export (IPFIX) Entities", n.d., <https://www.iana.org/assignments/ipfix/ipfix.xhtml>.

Authors' Addresses

Yisong Liu
China Mobile
32 Xuanwumen West Street
Beijing
Xicheng District, 100053
China
Changwang Lin
New H3C Technologies
8 Yongjia North Road
Beijing
Haidian District, 100094
China