This application provides a message processing method, an access controller, and a network node. In some aspects, an access controller receives a first message used to obtain Internet Protocol (IP) address information for a user-side device and a first access loop identifier of a first network node, where the first message and the first access loop identifier are sent by the first network node, the first access loop identifier is not carried in the first message. The access controller obtains an authentication, authorization and accounting (AAA) message according to the first access loop identifier, wherein the AAA message comprises the first access loop identifier. The access controller sends the AAA message to an AAA server.