This object indicates the cause that the LSP becomes Down.
Options:
1. routeDelete(1) -indicates that a route has been deleted.
2. lspmNotify(2) -indicates that LSPM notify.
3. canNotRecoveryFromGr(3) -indicates that the recovery from GR was failed.
4. recvReleaseMsg(4) -indicates that the release message was received.
5. recvWithdrawMsg(5) -indicates that the withdraw message was received.
6. upStreamLost(6) -indicates that the upstream route was lost.
7. downStreamLost(7) -indicates that the downstream route was lost.
8. otherReason(8) -indicates that another cause was involved.