BGP PIC and its Relationship with BGP Attributes

BGP PIC (Prefix Independent Convergence) provides fast convergence by pre-installing these paths in the forwarding table. Its primary function is to precompute and pre-install alternate valid paths in the forwarding table for faster convergence during failures.

While BGP attributes determine the best path selection and influence which paths become primary and backup routes, they don't directly affect the BGP PIC mechanism itself. When the primary path fails, BGP PIC enables immediate switchover to the backup path without requiring attribute re-evaluation.

Key points about BGP PIC:

  • Precomputes alternate valid paths.
  • Pre-installs backup paths in forwarding table.
  • Enables fast convergence by allowing forwarding to continue using pre-installed backup paths while control plane recomputation occur.
  • Uses paths determined by normal BGP path selection process.
  • Works with any valid paths regardless of their attribute values.

The backup paths used by BGP PIC can have either matching or different attributes compared to the primary path - this is not mandatory for PIC operation. However, BGP attributes remain important for overall traffic engineering and path selection in the network.

https://networklessons.com/bgp/bgp-pic-prefix-independent-convergence-core-edge

https://networklessons.com/bgp/bgp-attributes-and-path-selection