Since its introduction in RFC1997, the BGP community attribute has been used by many Autonomous Systems to build more scalable routing policies. We describe here the most common utilizations of the BGP community attribute and provide some examples.
Bonaventure, O., & Quoitin, B. (2003). Common utilizations of the BGP community attribute (Internet Engineering Task Force draft-bq-bgp-communities-00.txt). https://hdl.handle.net/2078.5/254897