This Appendix discusses the transitions between states in the BGP FSM in response to BGP events. The following is the list of these states and events when the negotiated Hold Time value is non-zero.
BGP States: 1 - Idle 2 - Connect 3 - Active 4 - OpenSent 5 - OpenConfirm 6 - Established BGP Events: 1 - BGP Start 2 - BGP Stop 3 - BGP Transport connection open 4 - BGP Transport connection closed 5 - BGP Transport connection open failed 6 - BGP Transport fatal error 7 - ConnectRetry timer expired 8 - Hold Timer expired 9 - KeepAlive timer expired 10 - Receive OPEN message 11 - Receive KEEPALIVE message 12 - Receive UPDATE messages 13 - Receive NOTIFICATION message
The following table describes the state transitions of the BGP FSM and the actions triggered by these transitions.
Event Actions Message Sent Next State -------------------------------------------------------------------- Idle (1) 1 Initialize resources none 2 Start ConnectRetry timer Initiate a transport connection others none none 1 Connect(2) 1 none none 2 3 Complete initialization OPEN 4 Clear ConnectRetry timer 5 Restart ConnectRetry timer none 3 7 Restart ConnectRetry timer none 2 Initiate a transport connection others Release resources none 1 Active (3) 1 none none 3 3 Complete initialization OPEN 4 Clear ConnectRetry timer 5 Close connection 3 Restart ConnectRetry timer 7 Restart ConnectRetry timer none 2 Initiate a transport connection others Release resources none 1 OpenSent(4) 1 none none 4 4 Close transport connection none 3 Restart ConnectRetry timer 6 Release resources none 1 10 Process OPEN is OK KEEPALIVE 5 Process OPEN failed NOTIFICATION 1 others Close transport connection NOTIFICATION 1 Release resources OpenConfirm (5) 1 none none 5 4 Release resources none 1 6 Release resources none 1 9 Restart KeepAlive timer KEEPALIVE 5 11 Complete initialization none 6 Restart Hold Timer 13 Close transport connection 1 Release resources others Close transport connection NOTIFICATION 1 Release resources Established (6) 1 none none 6 4 Release resources none 1 6 Release resources none 1 9 Restart KeepAlive timer KEEPALIVE 6 11 Restart Hold Timer KEEPALIVE 6 12 Process UPDATE is OK UPDATE 6 Process UPDATE failed NOTIFICATION 1 13 Close transport connection 1 Release resources others Close transport connection NOTIFICATION 1 Release resources ---------------------------------------------------------------------
The following is a condensed version of the above state transition table.
Events| Idle | Connect | Active | OpenSent | OpenConfirm | Estab | (1) | (2) | (3) | (4) | (5) | (6) |-------------------------------------------------------------- 1 | 2 | 2 | 3 | 4 | 5 | 6 | | | | | | 2 | 1 | 1 | 1 | 1 | 1 | 1 | | | | | | 3 | 1 | 4 | 4 | 1 | 1 | 1 | | | | | | 4 | 1 | 1 | 1 | 3 | 1 | 1 | | | | | | 5 | 1 | 3 | 3 | 1 | 1 | 1 | | | | | | 6 | 1 | 1 | 1 | 1 | 1 | 1 | | | | | | 7 | 1 | 2 | 2 | 1 | 1 | 1 | | | | | | 8 | 1 | 1 | 1 | 1 | 1 | 1 | | | | | | 9 | 1 | 1 | 1 | 1 | 5 | 6 | | | | | | 10 | 1 | 1 | 1 | 1 or 5 | 1 | 1 | | | | | | 11 | 1 | 1 | 1 | 1 | 6 | 6 | | | | | | 12 | 1 | 1 | 1 | 1 | 1 | 1 or 6 | | | | | | 13 | 1 | 1 | 1 | 1 | 1 | 1 | | | | | | ---------------------------------------------------------------