The local VPWS site ID, or zero if not specified. This is only used if BGP auto-discovery is enabled (vpwsConfigADType = bgp). It can be used with BGP or LDP signaling. If auto-discovery is enabled then the VPWS service establishes a pseudowire (PW) between each pair of VPWS sites within a VPWS. The valid range for VPWS site IDs depends on whether LDP or BGP signaling is used. - For LDP signaling (vpwsConfigSigType = ldp) the valid range is 1-4294967295 (4 bytes). - For BGP signaling (vpwsConfigSigType = bgp) the valid range is 1-65535 (2 bytes). The use of the VPWS site ID in auto-discovery and signaling also depends on whether LDP or BGP signaling is used. - For BGP auto-discovery with LDP signaling the VPWS site ID is advertised in the 4-byte 'PE_addr' field in the BGP NLRI specified in [RFC 6074]. It is also used as the local SAII/TAII value in LDP messages. - For BGP auto-discovery with BGP signaling the VPWS site ID is advertised in the 2-byte 'VE ID' field in the BGP NLRI specified in [RFC 4761]. Changing this value will cause an interruption to data flow for this VPWS.