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

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. 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 , for BIER purposes. These IEs are used to export the main parameters of BIER flow. This function can be used to collect statistics on the BIER flow receiving at a current node; and obtain node statistics information of the BIER flow.

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 . The following terms are used as defined in : IPFIX IPFIX Information Elements The following terms are used as defined in : TC TTL BFR BIFT BFIR BFER BSL SD SI

This section specifies the new IPFIX BIER IEs. The value of the TTL field in the BIER header (Section 2 of ). This IE indicates the incoming Time to Live (TTL) when a BIER packet is received. This IE indicates what type of BIER packet encapsulation is used. There are currently three encapsulation methods for BIER packets: Ethernet encapsulation, defined in ; MPLS encapsulation, also defined in ; and IPv6-based encapsulation, defined in . The version of the BIER header (Section 2 of ). The value of the BSL field in the BIER header (Section 2 of ). This IE indicates the length in bits of the BitString defined in the BIER header (Section 2 of ). The value of the Entropy field in the BIER header (Section 2 of ). It is can be used for load-balancing purposes. The OAM and Rsv field from the BIER header (Section 2 of ). The value of the DSCP field in the BIER header (Section 2 of ). In Non-MPLS networks, it is used to hold a Differentiated Services Codepoint . The next protocol defined in the Proto field of the BIER header (Section 2 of ). It identifies the type of the payload following the BIER header. The value of the BFIR-id field in the BIER header (Section 2 of ). It indicates the BFR-id of the BFIR in the SD to which the packet has been assigned. The BitString field defined in the BIER header (Section 2 of ). Together with the packet's SI and SD, it identifies the destination BFERs for this packet.

The `bierEncapType` cannot be directly obtained from the BIER Header; it must be derived from the corresponding encapsulation method. Different encapsulation types guide BIER packets through different forwarding table entries. For the Collector, knowing the encapsulation type of the BIER packet is helpful for statistical analysis or statistical purposes regarding the corresponding forwarding patterns. BIER packets can be directly encapsulated using the Ethernet type. In this case, the BIER header is directly encapsulated with Ethernet type 0xAB37. BIER packets can also be encapsulated using an MPLS label stack. The label at the bottom of the stack guides the BIER packet to find the corresponding MPLS forwarding table entry. The definitions of Ethernet type and MPLS encapsulation are both in . BIER packets can also be encapsulated in IPv6 format. In this mode, the BIER header is encapsulated after the IPv6 header. This method is defined in . The node, based on the specific encapsulation information of the received BIER message and other IEs in the message header, sends it to the Collector so that the Collector can perform further statistics and analysis.

The IPFIX IEs defined in the Section 3, and some existing IP packet header information provide answers to the following questions (amongst others). Whether the IP packet is a BIER packet? Whether the BIER packet is from an MPLS network? What is the incoming TTL of the BIER packet? What is BIER version used by the BIER packet? What is the type of the payload following the BIER header in the BIER packet? What is the destination BFERs for the BIER packet?

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

This document requests IANA to add new IPFIX BIER IEs to the "IPFIX Information Elements" registry available at . Table 1 lists the new IPFIX BIER IEs:

ElementID:: TBD1

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 for more details about the TTL fields.

Reference:: [this document]

ElementID:: TBD2

Name:: bierEncapType

Abstract Data Type:: unsigned8

Data Type Semantics:: default

Status:: current

Description:: This IE indicates the encapsulation type of BIER packet. When the value is set to 0, it indicates Ethernet encapsulation; when the value is set to 1, it indicates MPLS encapsulation; when the value is set to 2, it indicates IPv6 encapsulation.

Reference:: [this document]

ElementID:: TBD3

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 for more details about the Ver field of the BIER header.

Reference:: [this document]

ElementID:: TBD4

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 for more details about the BSL field of the BIER header.

Reference:: [this document]

ElementID:: TBD5

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 for more details about the Entropy field of the BIER header.

Reference:: [this document]

ElementID:: TBD6

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 for more details about the OAM and Rsv field of the BIER header.

Reference:: [this document]

ElementID:: TBD7

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 for more details about the DSCP field of the BIER header.

Reference:: [this document]

ElementID:: TBD8

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 for more details about the Proto field of the BIER header.

Reference:: [this document]

ElementID:: TBD9

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 for more details about the BFIR-id field of the BIER header.

Reference:: [this document]

ElementID:: TBD10

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 for more details about the BitString field of the BIER header.

Reference:: [this document]