| Internet-Draft | BGP-LS Extensions for Algorithm Related | July 2024 |
| Chen, et al. | Expires 9 January 2025 | [Page] |
This draft describes a mechanism to distribute SR-MPLS algorithm Related Adjacency SID from controllers to the headend routers using BGP-LS.¶
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[I-D.ietf-lsr-algorithm-related-adjacency-sid] defines the algorithm identifier can be included as part of an Adjacency-SID advertisement for SR-MPLS.¶
[I-D.peng-idr-segment-routing-te-policy-attr] proposes extensions of BGP and defines new Segment Types to provide algorithm information for SR-MPLS Adjacency-SIDs when delivering SR Policy via BGP.¶
[RFC9085]defines extensions to the Border Gateway Protocol-Link State (BGP-LS) address family in order to carry SR information via BGP, and an algorithm identifier is included as part of the Prefix-SID TLV advertisement.¶
This draft describes a mechanism to distribute SR-MPLS algorithm Related Adjacency SID from controllers to the headend routers using BGP-LS.¶
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 RFC 2119 [RFC2119].¶
[I-D.ietf-lsr-algorithm-related-adjacency-sid] defines the algorithm identifier can be included as part of an Adjacency-SID advertisement for SR-MPLS. This section defines the encoding of SR-MPLS algorithm Related Adjacency SID describes in [I-D.ietf-lsr-algorithm-related-adjacency-sid].¶
The following link attribute TLVs are defined:¶
| Type | Description |
|---|---|
| TBD1 | Adjacency SID per Algorithm |
| TBD2 | LAN Adjacency SID per Algorithm |
The Adjacency SID per Algorithm TLV is used in order to advertise information related to an algorithm Related Adjacency SID. This information is derived from the Adjacency Segment Identifier (Adj-SID) per Algorithm Sub-TLV of ISIS/OSPFv2/OSPFv3(Section 4 of [I-D.ietf-lsr-algorithm-related-adjacency-sid]).¶
The Adjacency SID per Algorithm TLV has the following format:¶
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 | Weight | Algorithm | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID/Label/Index (variable) //
+---------------------------------------------------------------+
¶
where:¶
Type: TBD1 (Suggested value to be assigned by IANA)¶
Length: variable.¶
Flags: 1-octet value that should be set as:¶
Weight: 1 octet carrying the weight used for load-balancing purposes. The use of weight is described in Section 3.4 of [RFC8402].¶
Algorithm: Refer to ISIS/OSPFv2/OSPFv3 Adj-SID per Algorithm([I-D.ietf-lsr-algorithm-related-adjacency-sid]).¶
Reserved: 1-octet that MUST be set to 0 and ignored on receipt.¶
SID/Label/Index:Refer to ISIS/OSPFv2/OSPFv3 Adj-SID per Algorithm([I-D.ietf-lsr-algorithm-related-adjacency-sid]).¶
This information is derived from LAN-Adj-SID per Algorithm Sub-TLV of ISIS/OSPFv2/OSPFv3(Section 4 of [I-D.ietf-lsr-algorithm-related-adjacency-sid]).¶
The LAN Adjacency SID per Algorithm TLV has the following format:¶
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 | Weight | Algorithm | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OSPF Neighbor ID / IS-IS System ID |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID/Label/Index (variable) //
+---------------------------------------------------------------+
¶
where:¶
Type: TBD2 (Suggested value to be assigned by IANA)¶
Length: variable.¶
Flags: 1-octet value that should be set as:¶
Weight: 1 octet carrying the weight used for load-balancing purposes. The use of weight is described in Section 3.4 of [RFC8402].¶
Algorithm: Refer to ISIS/OSPFv2/OSPFv3 LAN-Adj-SID per Algorithm([I-D.ietf-lsr-algorithm-related-adjacency-sid]).¶
Reserved: 1-octet that MUST be set to 0 and ignored on receipt.¶
Neighbor ID/IS-IS System ID: Refer to ISIS/OSPFv2/OSPFv3 LAN-Adj-SID per Algorithm([I-D.ietf-lsr-algorithm-related-adjacency-sid]).¶
SID/Label/Index:Refer to ISIS/OSPFv2/OSPFv3 LAN-Adj-SID per Algorithm([I-D.ietf-lsr-algorithm-related-adjacency-sid]).¶
[I-D.peng-idr-segment-routing-te-policy-attr] defines four new Segment types of Segment Sub-TLV to provide algorithm information for SR-MPLS Adjacency-SIDs. This section defines the encoding of the Segment Descriptors for each of those Segment types to be used in the Segment sub-TLV describes in [I-D.ietf-idr-bgp-ls-sr-policy].¶
The following Segment Descriptors are defined and their mapping to the respective segment types defined in [I-D.peng-idr-segment-routing-te-policy-attr]:¶
| Type | Segment Description |
|---|---|
| TBD3 | (Type L)IPv4 Address and Local Interface ID with optional Algorithm |
| TBD4 | (Type M)IPv4 Addresses for link endpoints as Local, Remote pair with optional Algorithm |
| TBD5 | (Type N)IPv6 Prefix and Interface ID for link endpoints as Local, Remote pair, with optional Algorithm for SR-MPLS |
| TBD6 | (Type O)IPv6 Addresses for link endpoints as Local, Remote pair, with optional Algorithm for SR-MPLS |
The Segment is SR-MPLS Adjacency SID with optional Algorithm type and is specified as an IPv4 node address along with the local interface ID on that node. The format of its Segment Descriptor 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
+-+-+-+-+-+-+-+-+
| Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Node Address (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Interface ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
¶
where:¶
Algorithm: 1-octet value that indicates the algorithm used for picking the SID. This is valid only when the A-flag has been set in the Segment TLV as defined in [I-D.ietf-idr-bgp-ls-sr-policy]. When A-Flag is not encoded, this field SHOULD be set to zero on transmission and MUST be ignored on receipt.¶
Other fields have the same meaning as the Type G Segment Sub-TLV Section 5.8.1.5 of [I-D.ietf-idr-bgp-ls-sr-policy], where:¶
IPv4 Node Address: 4-octet value which carries the IPv4 address associated with the node¶
Local Interface ID: 4-octet value which carries the local interface ID of the node identified by the Node Address.¶
The Segment is SR-MPLS Adjacency SID with optional Algorithm type and is specified as a pair of IPv4 local and remote addresses. The format of its Segment Descriptor 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
+-+-+-+-+-+-+-+-+
| Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Local Address (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Remote Address (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
¶
where:¶
Algorithm: 1-octet value that indicates the algorithm used for picking the SID. This is valid only when the A-flag has been set in the Segment TLV as defined in [I-D.ietf-idr-bgp-ls-sr-policy]. When A-Flag is not encoded, this field SHOULD be set to zero on transmission and MUST be ignored on receipt.¶
Other fields have the same meaning as the Type G Segment Sub-TLV Section 5.8.1.6 of [I-D.ietf-idr-bgp-ls-sr-policy], where:¶
IPv4 Local Address: 4-octet value which carries the local IPv4 address associated with the node.¶
IPv4 Remote Address: 4-octet value which carries the remote IPv4 address associated with the node's neighbor. This is optional and MAY be set to 0 when not used (e.g. when identifying point-to-point links).¶
The Segment is SR-MPLS Adjacency SID optional Algorithm type and is specified as a pair of IPv6 global address and interface ID for local and remote nodes. The format of its Segment Descriptor 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
+-+-+-+-+-+-+-+-+
| Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Local Node Global Address (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local Node Interface ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Remote Node Global Address (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Remote Node Interface ID (4 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
¶
where:¶
Algorithm: 1-octet value that indicates the algorithm used for picking the SID. This is valid only when the A-flag has been set in the Segment TLV as defined in [I-D.ietf-idr-bgp-ls-sr-policy]. When A-Flag is not encoded, this field SHOULD be set to zero on transmission and MUST be ignored on receipt.¶
Other fields have the same meaning as the Type G Segment Sub-TLV Section 5.8.1.7 of [I-D.ietf-idr-bgp-ls-sr-policy], where:¶
IPv6 Local Node Global Address: 16-octet value which carries the IPv6 global address associated with the local node.¶
Local Node Interface ID : 4-octet value which carries the interface ID of the local node identified by the Local Node Address.¶
IPv6 Remote Node Global Address: 16-octet value which carries the IPv6 global address associated with the remote node. This is optional and MAY be set to 0 when not used (e.g. when identifying point-to-point links).¶
Remote Node Interface ID: 4-octet value which carries the interface ID of the remote node identified by the Remote Node Address. This is optional and MAY be set to 0 when not used (e.g. when identifying point-to-point links).¶
The Segment is SR-MPLS Adjacency SID optional Algorithm type and is specified as a pair of IPv6 Global addresses for local and remote interface addresses. The format of its Segment Descriptor 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
+-+-+-+-+-+-+-+-+
| Algorithm |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Local Address (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Remote Address (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
¶
where:¶
Algorithm: 1-octet value that indicates the algorithm used for picking the SID. This is valid only when the A-flag has been set in the Segment TLV as defined in [I-D.ietf-idr-bgp-ls-sr-policy]. When A-Flag is not encoded, this field SHOULD be set to zero on transmission and MUST be ignored on receipt.¶
Other fields have the same meaning as the Type G Segment Sub-TLV Section 5.8.1.8 of [I-D.ietf-idr-bgp-ls-sr-policy], where:¶
IPv6 Local Address: 16-octet value which carries the local IPv6 address associated with the node.¶
IPv6 Remote Address: 16-octet value which carries the remote IPv6 address associated with the node's neighbor¶
TBD.¶
This document makes the following Link Attribute TLVs registry under the "Border Gateway Protocol-Link State (BGP-LS) Parameter".¶
Value Description Reference -------------------------------------------------------------- TBD1 Adjacency SID per Algorithm This document TBD2 LAN Adjacency SID per Algorithm This document¶
This document makes the following SR Segment Descriptor Types registry under the "SR Segment Descriptor Types". The registry contains the following codepoints to be assigned by IANA with the reference set to this document:¶
Value Segment Description Reference
--------------------------------------------------------------------------------------
TBD3 IPv4 Address and Local Interface ID with optional Algorithm This document
TBD4 IPv4 Addresses for link endpoints as Local, Remote pair with This document
optional Algorithm
TBD5 IPv6 Prefix and Interface ID for link endpoints as Local, This document
Remote pair, with optional Algorithm for SR-MPLS
TBD6 IPv6 Addresses for link endpoints as Local, Remote pair, This document
with optional Algorithm for SR-MPLS
¶