Autonomous-System-Wide Unique BGP Identifier for BGP-4

@article{Chen2011AutonomousSystemWideUB,
  title={Autonomous-System-Wide Unique BGP Identifier for BGP-4},
  author={Enke Chen and Jenny Yuan},
  journal={RFC},
  year={2011},
  volume={6286},
  pages={1-4}
}
To accommodate situations where the current requirements for the BGP Identifier are not met, this document relaxes the definition of the BGP Identifier to be a 4-octet, unsigned, non-zero integer and relaxes the "uniqueness" requirement so that only Autonomous-Systemwide (AS-wide) uniqueness of the BGP Identifiers is required. These revisions to the base BGP specification do not introduce any backward compatibility issues. This document updates RFC 4271.