IS-IS, OSPF and BGP extensions for BIER-TE (Tree Engineering for Bit Index Explicit Replication) with MPLS and non-MPLS Encapsulation

Introduction "Bit Index Explicit Replication Traffic Engineering" (BIER-TE) describes per-packet stateless strict and loose path steered replication and forwarding for "Bit Index Explicit Replication" (BIER, ) packets. It is called BIER Tree Engineering (BIER-TE) and is intended to be used as the path steering mechanism for Traffic Engineering with BIER. RBS introduces a compact data-structure representation of multicast trees called "Recursive Bitstring Structure" (RBS) and its use for (stateless) forwarding of packets that include this structure in their header. BIER-TE and RBS both use a "bit positions" (BP) for the representation of link or adjacency. , , and describe IS-IS, OSPF, OSPFv3 extensions respectively for distributing BitPositions configured on the links in BIER-TE domain. As described in section 2.4 in and section 5 in , BIER-TE/RBS inherits the encapsulation supporting from BIER unchanged. The encapsulation defined in , which specifies a common header format for both MPLS and non-MPLS networks, though the first 20-bits (referred to as BIFT-id) of the header is an "MPLS Label" in case of MPLS networks and is a local 20-bit opaque value in case of non-MPLS networks. As described in section 4.3 of and section 5 in , it is necessary to distinguish the BIER and BIER-TE/RBS packet and forwarding. like , , , and , the MPLS and non-MPLS encapsulation needs to be advertised for BIER-TE/RBS packet encapsulation. The advertisement can follow the existed BIER-TE BP advertisement, but it does not work well if there are many BIER-TE links need to be advertised. Too many octets in the advertisement will be consumed even if the same BIFT-id is used for different links. On the other hand, the BP advertisement does not work in BGP protocol when BIER-TE/RBS is used in across-domain scenario. This document describes the IS-IS, OSPF and BGP protocol extensions that are required for BIER-TE/RBS with MPLS and non-MPLS encapsulation associated with prefix distributing.

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 .

Terminology This document does not introduce more terminologies than , , , , , , and .

Flooding of the BIER-TE/RBS Encapsulation Information in IS-IS The BIER-TE MPLS Encapsulation Sub-sub-TLV and BIER-TE non-MPLS Encapsulation Sub-sub-TLV are advertised with BIER-Info Sub-TLV, which is defined in section 6.1 in . As described in section 4.3 in and section 5 in , the label for MPLS encapsulation or the BIFT-ID for non-MPLS encapsulation is allocatd per SD:BSL. The flooding scope is the same with section 5 in .

BIER-TE MPLS Encapsulation Sub-sub-TLV

Type: TBD (To be assigned by IANA).
Length: 1-octet.
subdomain-id: A 1-octet field encoding the Unique value identifying the BIER subdomain. The values allowed in this field are specified in Section 1 of .
BS Len (BitString Length): A 4-bit field encoding the supported BitString length associated with this BFR-prefix. The values allowed in this field are specified in Section 2 of .
Label: A 20-bit field, first label of the range. The labels are as defined in .

The BIER-TE MPLS encapsulation Sub-sub-TLV may be advertised many times for different subdomain-id or BS Len.

BIER-TE Non-MPLS Encapsulation Sub-sub-TLV

Type: TBD (To be assigned by IANA).
Length: 1-octet.
subdomain-id: A 1-octet field encoding the Unique value identifying the BIER subdomain. The values allowed in this field are specified in Section 1 of .
BS Len (BitString Length): A 4-bit field encoding the supported BitString length associated with this BFR-prefix. The values allowed in this field are specified in Section 2 of .
BIFT-ID: A 20-bit field, first BIFT-ID of the range. The BIFT-ID is as defined in .

The BIER-TE non-MPLS encapsulation sub-sub-TLV may be advertised many times for different subdomain-id or BS Len.

BIER-TE IPv6 Encapsulation sub-sub-sub-tlv As described in section 4 of , which describes how the existing BIER encapsulation specified in works in a non-MPLS IPv6 network, a node that requires IPv6 encapsulation MUST advertise the BIER-TE IPv6 encapsulation sub-sub-sub-TLV, which follows the associated Non-MPLS Encapsulation, according to local configuration or policy in the BIER domain to request other BFRs to always use IPv6 encapsulation.

Type: TBD (To be assigned by IANA).
Length: 0.

Flooding of the BIER-TE/RBS Encapsulation Information in OSPF Same with IS-IS, the BIER-TE MPLS Encapsulation Sub-TLV and BIER-TE non-MPLS Encapsulation Sub-TLV are Sub-TLVs of BIER Sub-TLV, which is defined in section 2.1 in . It is similar for OSPFv3, the BIER-TE MPLS Encapsulation Sub-TLV and BIER-TE non-MPLS Encapsulation Sub-TLV are Sub-TLVs of BIER Sub-TLV, which is defined in section 2.1 in . As described in section 4.3 in and section 5 in , the label for MPLS encapsulation or the BIFT-ID for non-MPLS encapsulation is allocatd per SD:BSL. The format defined below works for both OSPFv2 and OSPFv3. The flooding scope for OSPFv2 is the same with section 2.3 in . The flooding scope for OSPFv3 is the same with section 2.2 in .

BIER-TE MPLS Encapsulation Sub-TLV

Type: TBD (To be assigned by IANA).
Length: 2-octet.
Max SI: A 1-octet field encoding the maximum Set Identifier (SI) (see Section 1 of ) used in the encapsulation for this BIER sub-domain for this BitString length.
Label:A 3-octet field, where the 20 rightmost bits represent the first label in the label range. The 4 leftmost bits MUST be ignored.
BS Len (BitString Length): A 4-bit field encoding the supported BitString length associated with this BFR-prefix. The values allowed in this field are specified in Section 2 of .
Reserved: SHOULD be set to 0 on transmission and MUST be ignored on reception.

The BIER-TE MPLS encapsulation Sub-TLV may be advertised many times for different subdomain-id or BS Len.

BIER-TE Non-MPLS Encapsulation Sub-TLV

Type: TBD (To be assigned by IANA).
Length: 2-octet.
Max SI: A 1-octet field encoding the maximum Set Identifier (SI) (see Section 1 of ) used in the encapsulation for this BIER sub-domain for this BitString length.
BIFT-ID: A 3-octet field, where the 20 rightmost bits represent the first value in the range. The 4 leftmost bits MUST be ignored.
BS Len (BitString Length): A 4-bit field encoding the supported BitString length associated with this BFR-prefix. The values allowed in this field are specified in Section 2 of .
Reserved: SHOULD be set to 0 on transmission and MUST be ignored on reception.

The BIER-TE non-MPLS encapsulation Sub-TLV may be advertised many times for different subdomain-id or BS Len.

BIER-TE IPv6 Encapsulation sub-sub-tlv As described in section 4 of , which describes how the existing BIER encapsulation specified in works in a non-MPLS IPv6 network, a node that requires IPv6 encapsulation MUST advertise the BIER-TE IPv6 encapsulation sub-sub-sub-TLV, which follows the associated Non-MPLS Encapsulation, according to local configuration or policy in the BIER domain to request other BFRs to always use IPv6 encapsulation.

Type: TBD (To be assigned by IANA).
Length: 0.

Advertise the BIER-TE/RBS Encapsulation Information in BGP The BIER-TE MPLS Encapsulation Sub-TLV and BIER-TE non-MPLS Encapsulation Sub-TLV are Sub-TLVs of BIER Attribute, which is defined in section 3 in . As described in section 4.3 in and section 5 in , the label for MPLS encapsulation or the BIFT-ID for non-MPLS encapsulation is allocatd per SD:BSL. The formats of the BIER-TE MPLS Encapsulation Sub-TLV, BIER-TE non-MPLS Encapsulation Sub-TLV and BIER-TE IPv6 Encapsulation sub-sub-tlv are the same with OSPF . The orgination, update and calculation of the Sub-TLVs follow the definition in .

IANA Considerations The document requests new allocations from the IANA registries as follows:

IS-IS Sub-sub-TLVs for BIER Info sub-TLV Registry BIER-TE MPLS Encapsulation Sub-sub-TLV: TBD (suggested value 3) BIER-TE non-MPLS Encapsulation Sub-sub-TLV: TBD (suggested value 4) IANA is requested to create a registry for "IS-IS BIER-TE non-MPLS Encapsulation Sub-sub-TLV". The type field for the registry consists of 1 octet, with possible values from 1 to 255 (the value 0 is reserved). The allocation policy for this field is to be "First Come First Serve". A "BIER-TE IPv6 encapsulation Sub-sub-sub-TLV" type (TBD, suggested value 1) is requested to be assigned in it.

OSPFv2 Extended Prefix TLV Sub-TLVs Registry BIER-TE MPLS Encapsulation Sub-TLV: TBD (suggested value 12) BIER-TE non-MPLS Encapsulation Sub-TLV: TBD (suggested value 13) IANA is requested to create a registry for "OSPFv2 BIER-TE non-MPLS Encapsulation Sub-TLV". The type field for the registry consists of 2 octets, with possible values from 1 to 65535 (the value 0 is reserved). The allocation policy for this field is to be "First Come First Serve". A "BIER-TE IPv6 encapsulation Sub-sub-sub-TLV" type (TBD, suggested value 1) is requested to be assigned in it.

OSPFv3 Extended-LSA Sub-TLVs Registry BIER-TE MPLS Encapsulation Sub-TLV: TBD (suggested value 12) BIER-TE non-MPLS Encapsulation Sub-TLV: TBD (suggested value 13) IANA is requested to create a registry for "OSPFv3 BIER-TE non-MPLS Encapsulation Sub-TLV". The type field for the registry consists of 2 octets, with possible values from 1 to 65535 (the value 0 is reserved). The allocation policy for this field is to be "First Come First Serve". A "BIER-TE IPv6 encapsulation Sub-sub-sub-TLV" type (TBD, suggested value 1) is requested to be assigned in it.

BGP BIER TLV sub-TLV Types Registry BIER-TE MPLS Encapsulation Sub-TLV: TBD (suggested value 4) BIER-TE non-MPLS Encapsulation Sub-TLV: TBD (suggested value 5) IANA is requested to create a registry for "BGP BIER-TE non-MPLS Encapsulation Sub-TLV". The type field for the registry consists of 2 octets, with possible values from 1 to 65535 (the value 0 is reserved). The allocation policy for this field is to be "First Come First Serve". A "BIER-TE IPv6 encapsulation Sub-sub-sub-TLV" type (TBD, suggested value 1) is requested to be assigned in it.

Security Considerations This document does not introduce more security considerations than and , , and .