This is the path encoded with 4-octet
AS numbers in the optional transitive AS4_PATH attribute.
This value is populated with the received or sent attribute
in Adj-RIB-In or Adj-RIB-Out, respectively. It should not
be populated in Loc-RIB since the Loc-RIB is expected to
store the effective AS-Path in the as-path leaf regardless
of being 4-octet or 2-octet.Reference : RFC 6793 - BGP Support for Four-octet AS Number Space