If the LSP Timer (T1) expires, then the LSP enters the
Unavailable state. The start point of the Unavailable state
is deemed to be at the entry into the LSP defect state.
An LSP re-enters the Available state after the LSP Defect State.
first exists.
T1 defines the length of time the LSP is in the Defect state
before declaring an LSP Unavailable or returning to defect
free state
0: available state;
1: unavailable state.