If China desires to keep their boarder secure they will have to contain North Korea, eventually replace Kim Jong, and stabilize the country with a calm sensible puppet. Kim Jong is a loose cannon which China can least afford. The current relationship is costly, drain on their economy, and blight on their international prestige. The risk China faces is the increase of US military presence, enhanced military technology deployed to Japan and South Korea, and potential of a retaliatory strike against the North.