China-Viet Nam Diplomacy. What’s up?

This summer has seen three rounds of high level talks between Chinese and Vietnamese leadership. Both countries have long- standing issues and interests to be solved diplomatically, for example the islands claimed by both countries (and others) in the South China Sea, and expanding cross border trade. So why the efforts to shore-up their relationship now? What is on the short and long term horizon that has created a sense of urgency? Or is this just normal diplomatic activity? Please post your thoughts below.