| Internet-Draft | SR Segment Type Ext for BGP SR Policy | November 2024 |
| Talaulikar, et al. | Expires 11 May 2025 | [Page] |
This document specifies the signaling of additional Segment Routing Segment Types for signaling of Segment Routing (SR) Policies in BGP using SR Policy Subsequent Address Family Identifier.¶
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This Internet-Draft will expire on 11 May 2025.¶
Copyright (c) 2024 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.¶
BGP Segment Routing (SR) Policy Subsequent Address Family Identifier (SAFI) was introduced by [I-D.ietf-idr-sr-policy-safi] for the advertisement of SR Policy [RFC8402]. [I-D.ietf-idr-sr-policy-safi] introduced the base SR Segment Types A and B as specified by the SR Policy Architecture [RFC9256].¶
This document specifies the extensions for the advertisement of the remaining SR Segment Types defined in [RFC9256] in the SR Policy SAFI for both SR-MPLS [RFC8660] and SRv6 [RFC8754] [RFC8986].¶
The extensions in this document do not impact the SR Policy operations or fault management as specified in [I-D.ietf-idr-sr-policy-safi].¶
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 Segment List sub-TLV [I-D.ietf-idr-sr-policy-safi] encodes a single explicit path towards the endpoint as described in section 5.1 of [RFC9256]. The Segment List sub-TLV includes the elements of the paths (i.e., segments).¶
A Segment sub-TLV describes a single segment in a segment list (i.e., a single element of the explicit path).¶
Section 4 of [RFC9256] defines several Segment Types for SR-MPLS and SRv6 that are listed below as a reminder:¶
Type A: SR-MPLS Label
Type B: SRv6 SID
Type C: IPv4 Prefix with optional SR Algorithm
Type D: IPv6 Global Prefix with optional SR Algorithm for SR-MPLS
Type E: IPv4 Prefix with Local Interface ID
Type F: IPv4 Addresses for link endpoints as Local, Remote pair
Type G: IPv6 Prefix and Interface ID for link endpoints as Local,
Remote pair for SR-MPLS
Type H: IPv6 Addresses for link endpoints as Local, Remote pair
for SR-MPLS
Type I: IPv6 Global Prefix with optional SR Algorithm for SRv6
Type J: IPv6 Prefix and Interface ID for link endpoints as Local,
Remote pair for SRv6
Type K: IPv6 Addresses for link endpoints as Local, Remote pair
for SRv6
Figure 1: SR Segment Types
¶
[I-D.ietf-idr-sr-policy-safi] specifies Segment Type Sub-TLVs for the segment types A and B. The following sub-sections specify the sub-TLVs used for encoding each of the other Segment Types above.¶
As specified in sections 2.4.4 and 2.4.4.2 of [I-D.ietf-idr-sr-policy-safi], validation of an explicit path encoded by the Segment List sub-TLV is beyond the scope of BGP and performed by the Segment Routing Policy Module (SRPM) as described in section 5 of [RFC9256]. As specified in section 5.1 of [RFC9256], a mix of SR-MPLS and SRv6 segments make the segment-list invalid.¶
The Type C Segment Sub-TLV encodes an IPv4 node address, SR Algorithm, and an optional SR-MPLS SID. The format is 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Flags | SR Algorithm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 Node Address (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SR-MPLS SID (optional, 4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Type C Segment sub-TLV where:¶
Type: 3.¶
Length: Specifies the length of the value field (i.e., not including Type and Length fields) in terms of octets. The value MUST be 10 when the SR-MPLS SID is present, else it MUST be 6.¶
Flags: 1 octet of flags as defined in Section 2.10.¶
SR Algorithm: 1 octet specifying SR Algorithm as described in section 3.1.1 in [RFC8402] when A-Flag as defined in Section 2.10 is present. SR Algorithm is used by SRPM [I-D.ietf-idr-sr-policy-safi] as described in section 4 in [RFC9256]. When A-Flag is not encoded, this field MUST be set to zero on transmission and MUST be ignored on receipt.¶
IPv4 Node Address: a 4-octet IPv4 address representing a node.¶
SR-MPLS SID: optional, 4-octet field containing label, TC, S and TTL as defined for Segment Type A [I-D.ietf-idr-sr-policy-safi].¶
The Type D Segment Sub-TLV encodes an IPv6 node address, SR Algorithm, and an optional SR-MPLS SID. The format is 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Flags | SR Algorithm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // IPv6 Node Address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SR-MPLS SID (optional, 4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: Type D Segment sub-TLV where:¶
Type: 4¶
Length: Specifies the length of the value field (i.e., not including Type and Length fields) in terms of octets. The value MUST be 22 when the SR-MPLS SID is present, else it MUST be 18.¶
Flags: 1 octet of flags as defined in Section 2.10.¶
SR Algorithm: 1 octet specifying SR Algorithm as described in section 3.1.1 in [RFC8402] when A-Flag as defined in Section 2.10 is present. SR Algorithm is used by SRPM [I-D.ietf-idr-sr-policy-safi] as described in section 4 in [RFC9256]. When A-Flag is not encoded, this field MUST be set to zero on transmission and MUST be ignored on receipt.¶
IPv6 Node Address: a 16-octet IPv6 address representing a node.¶
SR-MPLS SID: optional, 4-octet field containing label, TC, S and TTL as defined for Segment Type A [I-D.ietf-idr-sr-policy-safi].¶
The Type E Segment Sub-TLV encodes an IPv4 node address, a local interface Identifier (Local Interface ID), and an optional SR-MPLS SID. The format is 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Flags | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local Interface ID (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 Node Address (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SR-MPLS SID (optional, 4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Type E Segment sub-TLV where:¶
Type: 5.¶
Length: Specifies the length of the value field (i.e., not including Type and Length fields) in terms of octets. The value MUST be 14 when the SR-MPLS SID is present, else it MUST be 10.¶
Flags: 1 octet of flags as defined in Section 2.10.¶
RESERVED: 1 octet of reserved bits. This field MUST be set to zero on transmission and MUST be ignored on receipt.¶
Local Interface ID: 4 octets of interface index of local interface (refer TLV 258 of [RFC9552]).¶
IPv4 Node Address: a 4-octet IPv4 address representing a node.¶
SR-MPLS SID: optional, 4-octet field containing label, TC, S and TTL as defined for Segment Type A [I-D.ietf-idr-sr-policy-safi].¶
The Type F Segment Sub-TLV encodes an adjacency local address, an adjacency remote address, and an optional SR-MPLS SID. The format is 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Flags | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local IPv4 Address (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote IPv4 Address (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SR-MPLS SID (optional, 4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: Type F Segment sub-TLV where:¶
Type: 6.¶
Length: Specifies the length of the value field (i.e., not including Type and Length fields) in terms of octets. The value MUST be 14 when the SR-MPLS SID is present, else it MUST be 10.¶
Flags: 1 octet of flags as defined in Section 2.10.¶
RESERVED: 1 octet of reserved bits. This field MUST be set to zero on transmission and MUST be ignored on receipt.¶
Local IPv4 Address: a 4-octet IPv4 address representing the local link address of the node.¶
Remote IPv4 Address: a 4-octet IPv4 address representing the link address of the neighbor node.¶
SR-MPLS SID: optional, 4-octet field containing label, TC, S and TTL as defined for Segment Type A [I-D.ietf-idr-sr-policy-safi].¶
The Type G Segment Sub-TLV encodes an IPv6 link-local adjacency with IPv6 local node address, a local interface identifier (Local Interface ID), IPv6 remote node address, a remote interface identifier (Remote Interface ID), and an optional SR-MPLS SID. The format is 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Flags | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local Interface ID (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // IPv6 Local Node Address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote Interface ID (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // IPv6 Remote Node Address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SR-MPLS SID (optional, 4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 6: Type G Segment sub-TLV where:¶
Type: 7¶
Length: Specifies the length of the value field (i.e., not including Type and Length fields) in terms of octets. The value MUST be 46 when the SR-MPLS SID is present, else it MUST be 42.¶
Flags: 1 octet of flags as defined in Section 2.10.¶
RESERVED: 1 octet of reserved bits. This field MUST be set to zero on transmission and MUST be ignored on receipt.¶
Local Interface ID: 4 octets of interface index of local interface (refer TLV 258 of [RFC9552]).¶
IPv6 Local Node Address: a 16-octet IPv6 address representing the node.¶
Remote Interface ID: 4 octets of interface index of remote interface (refer TLV 258 of [RFC9552]). The value MAY be set to zero when the local node address and interface identifiers are sufficient to describe the link.¶
IPv6 Remote Node Address: a 16-octet IPv6 address. The value MAY be set to zero when the local node address and interface identifiers are sufficient to describe the link.¶
SR-MPLS SID: optional, 4-octet field containing label, TC, S and TTL as defined for Segment Type A [I-D.ietf-idr-sr-policy-safi].¶
The Type H Segment Sub-TLV encodes an adjacency local address, an adjacency remote address, and an optional SR-MPLS SID. The format is 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Flags | RESERVED | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Local IPv6 Address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Remote IPv6 Address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SR-MPLS SID (optional, 4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 7: Type H Segment sub-TLV where:¶
Type: 8¶
Length: Specifies the length of the value field (i.e., not including Type and Length fields) in terms of octets. The value MUST be 38 when the SR-MPLS SID is present, else it MUST be 34.¶
Flags: 1 octet of flags as defined in Section 2.10.¶
RESERVED: 1 octet of reserved bits. This field MUST be set to zero on transmission and MUST be ignored on receipt.¶
Local IPv6 Address: a 16-octet IPv6 address representing the local link address of the node.¶
Remote IPv6 Address: a 16-octet IPv6 address representing the link address of the neighbor node.¶
SR-MPLS SID: optional, 4-octet field containing label, TC, S and TTL as defined for Segment Type A [I-D.ietf-idr-sr-policy-safi].¶
The Type I Segment Sub-TLV encodes an IPv6 node address, SR Algorithm, and an optional SRv6 SID. The format is 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Flags | SR Algorithm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // IPv6 Node Address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // SRv6 SID (optional, 16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // SRv6 Endpoint Behavior and SID Structure // // (optional, 8 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8: Type I Segment sub-TLV where:¶
Type: 14¶
Length: Specifies the length of the value field (i.e., not including Type and Length fields) in terms of octets. The value MUST be one of: 42 when both SRv6 SID and SRv6 Endpoint Behavior & SID Structure are present, 34 when only SRv6 SID is present, or 18 when the SRv6 SID is not present.¶
Flags: 1 octet of flags as defined in Section 2.10.¶
SR Algorithm: 1 octet specifying SR Algorithm as described in section 3.1.1 in [RFC8402] when A-Flag as defined in Section 2.10 is present. SR Algorithm is used by SRPM [I-D.ietf-idr-sr-policy-safi] as described in section 4 in [RFC9256]. When A-Flag is not encoded, this field MUST be set to zero on transmission and MUST be ignored on receipt.¶
IPv6 Node Address: a 16-octet IPv6 address representing the node.¶
SRv6 SID: optional, a 16-octet IPv6 address. The value 0 MAY be used when the controller wants to indicate the desired SRv6 Endpoint Behavior or SID Structure without specifying the SID.¶
SRv6 Endpoint Behavior and SID Structure: Optional, as defined in section 2.4.4.2.4 of [I-D.ietf-idr-sr-policy-safi]. The SRv6 Endpoint Behavior and SID Structure MUST NOT be included when the SRv6 SID has not been included.¶
The TLV 10 defined for the advertisement of Segment Type I in the early draft versions of [I-D.ietf-idr-sr-policy-safi] has been deprecated to avoid backward compatibility issues.¶
The Type J Segment Sub-TLV encodes an IPv6 link-local adjacency with local node address, a local interface identifier (Local Interface ID), remote IPv6 node address, a remote interface identifier (Remote Interface ID), and an optional SRv6 SID. The format is 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Flags | SR Algorithm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Local Interface ID (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // IPv6 Local Node Address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Remote Interface ID (4 octets) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // IPv6 Remote Node Address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // SRv6 SID (optional, 16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // SRv6 Endpoint Behavior and SID Structure // // (optional, 8 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 9: Type J Segment sub-TLV where:¶
Type: 15¶
Length: Specifies the length of the value field (i.e., not including Type and Length fields) in terms of octets. The value MUST be one of: 66 when both SRv6 SID and SRv6 Endpoint Behavior & SID Structure are present, 58 when only SRv6 SID is present, or 42 when the SRv6 SID is not present.¶
Flags: 1 octet of flags as defined in Section 2.10.¶
SR Algorithm: 1 octet specifying SR Algorithm as described in section 3.1.1 in [RFC8402] when A-Flag as defined in Section 2.10 is present. SR Algorithm is used by SRPM [I-D.ietf-idr-sr-policy-safi] as described in section 4 in [RFC9256]. When A-Flag is not encoded, this field MUST be set to zero on transmission and MUST be ignored on receipt.¶
Local Interface ID: 4 octets of interface index of local interface (refer TLV 258 of [RFC9552]).¶
IPv6 Local Node Address: a 16-octet IPv6 address representing the node.¶
Remote Interface ID: 4 octets of interface index of remote interface (refer TLV 258 of [RFC9552]). The value MAY be set to zero when the local node address and interface identifiers are sufficient to describe the link.¶
IPv6 Remote Node Address: a 16-octet IPv6 address. The value MAY be set to zero when the local node address and interface identifiers are sufficient to describe the link.¶
SRv6 SID: optional, a 16-octet IPv6 address. The value 0 MAY be used when the controller wants to indicate the desired SRv6 Endpoint Behavior or SID Structure without specifying the SID.¶
SRv6 Endpoint Behavior and SID Structure: Optional, as defined in section 2.4.4.2.4 of [I-D.ietf-idr-sr-policy-safi]. The SRv6 Endpoint Behavior and SID Structure MUST NOT be included when the SRv6 SID has not been included.¶
The TLV 11 defined for the advertisement of Segment Type J in the early draft versions of [I-D.ietf-idr-sr-policy-safi] has been deprecated to avoid backward compatibility issues.¶
The Type K Segment Sub-TLV encodes an adjacency local address, an adjacency remote address, and an optional SRv6 SID. The format is 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length | Flags | SR Algorithm | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Local IPv6 Address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // Remote IPv6 Address (16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // SRv6 SID (optional, 16 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // SRv6 Endpoint Behavior and SID Structure // // (optional, 8 octets) // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 10: Type K Segment sub-TLV where:¶
Type: 16¶
Length: Specifies the length of the value field (i.e., not including Type and Length fields) in terms of octets. The value MUST be one of: 58 when both SRv6 SID and SRv6 Endpoint Behavior & SID Structure are present, 50 when only SRv6 SID is present, or 34 when the SRv6 SID is not present.¶
Flags: 1 octet of flags as defined in Section 2.10.¶
SR Algorithm: 1 octet specifying SR Algorithm as described in section 3.1.1 in [RFC8402] when A-Flag as defined in Section 2.10 is present. SR Algorithm is used by SRPM [I-D.ietf-idr-sr-policy-safi] as described in section 4 in [RFC9256]. When A-Flag is not encoded, this field MUST be set to zero on transmission and MUST be ignored on receipt.¶
Local IPv6 Address: a 16-octet IPv6 address representing the local link address of the node.¶
Remote IPv6 Address: a 16-octet IPv6 address representing the link address of the neighbor node.¶
SRv6 SID: optional, a 16-octet IPv6 address. The value 0 MAY be used when the controller wants to indicate the desired SRv6 Endpoint Behavior or SID Structure without specifying the SID.¶
SRv6 Endpoint Behavior and SID Structure: Optional, as defined in section 2.4.4.2.4 of [I-D.ietf-idr-sr-policy-safi]. The SRv6 Endpoint Behavior and SID Structure MUST NOT be included when the SRv6 SID has not been included.¶
The TLV 12 defined for the advertisement of Segment Type K in the early draft versions of [I-D.ietf-idr-sr-policy-safi] has been deprecated to avoid backward compatibility issues.¶
The Segment Types sub-TLVs described above may contain the following SR Policy Segment Flags [I-D.ietf-idr-sr-policy-safi] in their "Flags" field. Also refer to Section 3.2. This document introduces additional flags as below:¶
0 1 2 3 4 5 6 7 +-+-+-+-+-+-+-+-+ |V|A|S|B| | +-+-+-+-+-+-+-+-+ Figure 11: SR Policy Segment Flags¶
where:¶
V-Flag: existing flag as defined in [I-D.ietf-idr-sr-policy-safi].¶
A-Flag: This flag, when set, indicates the presence of SR Algorithm id in the "SR Algorithm" field applicable to various Segment Types. SR Algorithm is used by SRPM [I-D.ietf-idr-sr-policy-safi] as described in section 4 of [RFC9256].¶
S-Flag: This flag, when set, indicates the presence of the SR-MPLS or SRv6 SID depending on the segment type.¶
B-Flag: existing flag as defined in [I-D.ietf-idr-sr-policy-safi].¶
The following applies to the Segment Flags:¶
V-Flag applies to all Segment Types including the ones introduced by this document.¶
A-Flag applies to Segment Types C, D, I, J, and K. If A-Flag appears with Segment Types A, B, E, F, G, and H, it MUST be ignored.¶
S-Flag applies to Segment Types C, D, E, F, G, H, I, J, and K. If S-Flag appears with Segment Types A or B, it MUST be ignored.¶
B-Flag applies to Segment Types B, I, J, and K. If B-Flag appears with Segment Types A, C, D, E, F, G, and H, it MUST be ignored.¶
This section covers the IANA considerations for this document.¶
This document requests the allocation of the following code points from the "SR Policy Segment List Sub-TLVs" registry under the "BGP Tunnel Encapsulation" registry group.¶
Value Description Reference
-----------------------------------------------------
3 Segment Type C sub-TLV This document
4 Segment Type D sub-TLV This document
5 Segment Type E sub-TLV This document
6 Segment Type F sub-TLV This document
7 Segment Type G sub-TLV This document
8 Segment Type H sub-TLV This document
14 Segment Type I sub-TLV This document
15 Segment Type J sub-TLV This document
16 Segment Type K sub-TLV This document
Table 1: SR Policy Segment List Code Points
¶
This document requests the allocation of code points from the "SR Policy Segment Flags" registry under the "BGP Tunnel Encapsulation" registry group.¶
Bit Description Reference
------------------------------------------------------------------
1 SR Algorithm Flag (A-Flag) This document
2 SID Specified Flag (S-Flag) This document
Table 2: SR Policy Segment Flags
¶
The security considerations in [I-D.ietf-idr-sr-policy-safi] apply to the segment types defined in this document. No additional security considerations are introduced in this document.¶
The operations and manageability considerations in [I-D.ietf-idr-sr-policy-safi] apply to the segment types defined in this document. No additional operations and manageability considerations are introduced in this document.¶
The authors of this document would like to Dan Romascanu, Stig Venaas, and Russ Housley for their comments and review of this document. The authors would like to thank Susan Hares for her detailed shepherd review that helped in improving the document.¶