https://blog.gongquiz.com/2021/04/21/%eb%a7%81%ed%81%ac-%ec%83%81%ed%83%9c-%eb%9d%bc%ec%9a%b0%ed%8c%85link-state-routing%ec%9d%98-%ec%84%a4%eb%aa%85%ec%9c%bc%eb%a1%9c-%ec%98%b3%ec%a7%80-%ec%95%8a%ec%9d%80-%ea%b2%83%ec%9d%80/