The value of this object identifies the configuration mode of a TTL used by
the BFD session for PW.
Options:
1. config(1) -indicates that the TTL is manually set
2. auto(2) -indicates that the TTL is automatically calculated based on an IP address
3. default(3) -indicates that the TTL is 255 by default
4. nottl(4) -indicates that the TTL is not in PW mode