BGP - Link State (BGP-LS) Advertisement of IGP Traffic Engineering Performance Metric Extensions
Extracted elements (13)
TLV formats follow the rules defined in RFC 7752 (BGP-LS), ensuring consistency with the existing BGP-LS framework. The semantics and value encoding of all fields are delegated to the IGP source specifications (RFC 8570 and RFC 7471) rather than re-specified in this document.
Section 2.8 documents the mapping between the seven BGP-LS Link Attribute TLVs and their IGP source sub-TLVs: IS-IS sub-TLVs 33–39 (RFC 8570) and OSPFv2/OSPFv3 sub-TLVs 27–33 (RFC 7471), preserving a one-to-one correspondence for each metric type.
RFC 8571 defines seven new BGP-LS Link Attribute TLVs (code points 1114–1120) to carry IGP Traffic Engineering Metric Extensions sourced from IS-IS (RFC 8570) and OSPF (RFC 7471): Unidirectional Link Delay, Min/Max Unidirectional Link Delay, Unidirectional Delay Variation, Unidirectional Link Loss, Unidirectional Residual Bandwidth, Unidirectional Available Bandwidth, and Unidirectional Utilized Bandwidth.
IANA assigned seven new code points (1114–1120) in the 'BGP-LS Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs' registry for the Link Attribute TLVs defined in this document: Unidirectional Link Delay (1114), Min/Max Unidirectional Link Delay (1115), Unidirectional Delay Variation (1116), Unidirectional Link Loss (1117), Unidirectional Residual Bandwidth (1118), Unidirectional Available Bandwidth (1119), and Unidirectional Utilized Bandwidth (1120).
The procedures and protocol extensions defined in this document do not affect the BGP security model. Security analysis for BGP is covered by RFC 4271, RFC 4272, and RFC 6952; security considerations for BGP-LS information distribution are addressed in RFC 7752.
The TLVs propagate IGP link state and resource-availability information. IGP instances originating these TLVs are assumed to support all required security and authentication mechanisms (as described in RFC 8570 and RFC 7471) to prevent security issues when propagating into BGP-LS. No additional risk is introduced beyond existing BGP-LS link attribute information.
Min/Max Unidirectional Link Delay TLV (Type 1115, Length 8): two 32-bit words; first contains a 1-bit A flag, 7 reserved bits, and a 24-bit Min Delay; second contains 8 reserved bits and a 24-bit Max Delay, encoding minimum and maximum delay between directly connected IGP neighbors.
Unidirectional Available Bandwidth TLV (Type 1119, Length 4): a single 32-bit Available Bandwidth field encoding available bandwidth between two directly connected IGP neighbors.
Unidirectional Delay Variation TLV (Type 1116, Length 4): 32-bit value with 8 reserved bits and a 24-bit Delay Variation field encoding average link delay variation between directly connected IGP neighbors. No anomalous flag.
Unidirectional Link Delay TLV (Type 1114, Length 4): 32-bit value with a 1-bit Anomalous (A) flag, 7 reserved bits, and a 24-bit Delay field encoding the average link delay between two directly connected IGP neighbors.
Unidirectional Link Loss TLV (Type 1117, Length 4): 32-bit value with a 1-bit Anomalous (A) flag, 7 reserved bits, and a 24-bit Link Loss field encoding packet loss percentage between directly connected IGP neighbors.
Unidirectional Residual Bandwidth TLV (Type 1118, Length 4): a single 32-bit Residual Bandwidth field (no flags or reserved bits) encoding residual bandwidth between two directly connected IGP neighbors.
Unidirectional Utilized Bandwidth TLV (Type 1120, Length 4): a single 32-bit Utilized Bandwidth field encoding bandwidth utilization between two directly connected IGP neighbors.