Appendix A. Aggregate Routing Information

As a practical matter, aggregation as discussed in [BGP-4], Section 9.2.2.2, is not generally employed within confederations. However, in the event that such aggregation is performed within a confederation, the rules of [BGP-4] should be followed, making the necessary substitutions between AS_SET and AS_CONFED_SET and similarly, AS_SEQUENCE and AS_CONFED_SEQUENCE. Confederation-type segments (AS_CONFED_SET and AS_CONFED_SEQUENCE) MUST be kept separate from non-confederation segments (AS_SET and AS_SEQUENCE). An implementation could also choose to provide a form of aggregation wherein non-confederation segments are aggregated as discussed in [BGP-4], Section 9.2.2.2, and confederation-type segments are not aggregated.

Support for aggregation of confederation-type segments is not mandatory.