BGP Keep a life

BGP open message有以下幾個訊息

1.BGP version number

2. AS number of the local router

3. Holdtime

4. BGP router identifier

5. Optional parameters

Hold time是雙方在建立BGP session時議定的參數，

若有所以彼此的hold time雙方會知道，但不會交換keep a live timer

1 If the locally configured value of holdtime is selected (being the lower of two), the

peers use the locally used keepalive interval.

若holdtime是自己的holdtime，對方使用自己設定的keepalive interval

2 If the holdtime interval of the neighbor is selected, and the locally configured

keepalive interval is less than a third of the holdtime interval, the peers use the

locally configured keepalive.

若holdtime使用對方的設定，而且自己設定的keepalive interval比holdtime/3還小，對方使用自己設定的keepalive

3 If the holdtime interval of the neighbor is selected, and the locally configured

keepalive interval is more than a third of the holdtime interval, the peers use the

smaller integer value in relation to (holdtime / 3).

若holdtime使用對方的設定，而且自己設定的keepalive interval比holdtime/3還大則對方使用比較holdtime/3小的整數當keepalive