2. BGP CAR SAFI (Continued)
2.9.2.1. Label TLV
The Label TLV is used to advertise CAR routes with MPLS labels. Label information is conveyed in multiples of 3-octet fields for encoding a single label or label stack.
2.9.2.2. Label-Index TLV
The Label-Index TLV is used to advertise SR-MPLS segment identifier information associated with labeled CAR routes. This TLV provides functionality equivalent to the Label-Index TLV of the BGP Prefix-SID attribute for transport CAR routes in SR-MPLS deployments, but by carrying the Label Index in the NLRI rather than in the Prefix-SID attribute, it provides better packing efficiency.
2.9.2.3. SRv6 SID TLV
The SRv6 SID TLV is used to advertise CAR routes with SRv6 SIDs. It supports a single 128-bit SRv6 SID, a SID list, or the transposition portion of a SID, providing an efficient encoding scheme for SRv6 encapsulation.
2.9.3. Color-Aware Route (E, C) NLRI Type
The Color-Aware Route NLRI type is used to advertise BGP CAR color-aware routes (E, C). The NLRI key contains an IP prefix and color value, with optional non-key TLVs used to carry encapsulation information.
2.9.4. IP Prefix (E) NLRI Type
The IP Prefix NLRI type is used to advertise BGP CAR IP prefix routes (E). It is applicable to scenarios where unique IP prefixes are allocated for specific intents.
2.9.5. Local Color Mapping (LCM) Extended Community
The LCM Extended Community is used to convey local color mapping when CAR routes cross color domain boundaries. When routes are propagated between different color domains, the LCM-EC carries the corresponding color value in the target domain.
2.10. LCM-EC and BGP Color-EC Usage
LCM-EC and BGP Color-EC work together to support route signaling across different color domains and flexible color mapping scenarios.
2.11. Error Handling
Error handling for BGP CAR NLRI follows the treat-as-withdraw approach. The presence of the Key Length field makes error handling more resilient.