question: protected void sendDiscoveryMessage ( DatapathId sw , OFPort port , boolean isStandard , boolean isReverse ) { if ( ! isOutgoingDiscoveryAllowed ( sw , port , isStandard , isReverse ) ) return ; IOFSwitch iofSwitch = switchService . getSwitch ( sw ) ; if ( iofSwitch == null ) return ; OFPortDesc ofpPort = iofSwitch . getPort ( port ) ; OFPacketOut po = generateLLDPMessage ( iofSwitch , port , isStandard , isReverse ) ; OFPacketOut . Builder pob = po . createBuilder ( ) ; List < OFAction > actions = getDiscoveryActions ( iofSwitch , ofpPort . getPortNo ( ) ) ; pob . setActions ( actions ) ; iofSwitch . write ( pob . build ( ) ) ; }
target:  Send link discovery message out of a given switch port. The discovery message may be a standard LLDP or a modified LLDP, where the dst mac address is set to :ff. TODO: The modified LLDP will updated in the future and may use a different eth-type.