BGP advertisement allows a BGP router to indicate to a peer, using the optional parameter, the features that it supports so that they can coordinate and use only the features that both support. Each capability in the optional parameter is TLV-encoded with a unique type code. SR OS supports the following capability codes:
multi-protocol BGP (code 1)
route refresh (code 2)
outbound route filtering (code 3)
graceful restart (code 64)
4-octet AS number (code 65)
add-path (code 69)