A method performed by a controller configured to implement Border Gateway Protocol (BGP) in a communications system, comprising establishing a controller BGP (cBGP) peer session with a network element (NE), receiving a message for communication through the cBGP session from the NE, determining whether the message is permitted to be communicated through the cBGP session based on whether the message carries routing information; transmitting the message to the NE through the cBGP session when the message is permitted to be communicated through the cBGP session, and receiving a response message of the first type from the NE through the cBGP session.