def __init__(self):
self.fields = {<EOL>self.INITIATOR_ADDTYPE: <NUM_LIT:0>,<EOL>self.INITIATOR_ADDRESS_LENGTH: <NUM_LIT:0>,<EOL>self.ACCEPTOR_ADDRTYPE: <NUM_LIT:0>,<EOL>self.ACCEPTOR_ADDRESS_LENGTH: <NUM_LIT:0>,<EOL>self.APPLICATION_DATA_LENGTH: <NUM_LIT:0>,<EOL>self.INITIATOR_ADDRESS: b"<STR_LIT>",<EOL>self.ACCEPTOR_ADDRESS: b"<STR_LIT>",<EOL>self.APPLICATION_DATA: b"<STR_LIT>"<EOL>}<EOL>
Used to send the out of band channel info as part of the authentication
process. This is used as a way of verifying the target is who it says
it is as this information is provided by the higher layer. In most
cases, the CBT is just the hash of the server's TLS certificate to the
application_data field.

This bytes string of the packed structure is then MD5 hashed and
included in the NTv2 response.