Application acknowledgement to an addressed binary message

Introduction/Additional information: 

When requested, IFM 5 should be used by an application to confirm the reception of an addressed binary message. An application should never acknowledge a binary broadcast message. If the interrogating application does not receive an IFM 5, when requested, then the application should assume that addressed AIS unit does not have an application attached to its Presentation Interface (PI). If there is any application at the AIS station, it should not respond if the “Acknowledge Required Flag” is set to 0.

Registrant: 
ITU.R-M.1371-4
Message number: 
6
DAC: 
1
FI: 
5
State: 
deprecated
Number of slots (max): 
1
Permitted as from: 
01/04/2010
Details: 

 Replacing by DAC 1 FI 1 (warning older AIS stations could still use DAC 1 FI 1)

Parameters Number of bits Description
Message ID 6 Identifier for Message 6; always 6
Repeat indicator 2 Used by the repeater to indicate how many times a message
has been repeated. See § 4.6.1, Annex 2; 0-3; 0 = default;
3 = do not repeat any more
Source ID 30 MMSI number of source station
Sequence number 2 0-3; see § 5.3.1, Annex 2
Destination ID 30 MMSI number of destination station
Retransmit flag 1 Retransmit flag should be set upon retransmission:
0 = no retransmission = default; 1 = retransmitted
Spare 1 Not used. Should be zero
DAC 10 International DAC = 110 = 00000000012
FI 6 Function identifier = 510 = 0001012
DAC code of received
FM
10 Recommended to be spare
FI code of received FM 6  
Text sequence number 11 Sequence number in the message being acknowledged as
properly received
0 = default (no sequence number)
1-2 047 = sequence number of received FM
AI available 1 0 = received but AI not available
1 = AI available
AI response 3 0 = unable to respond
1 = reception acknowledged
2 = response to follow
3 = able to respond but currently inhibited
4-7 = spare for future use
Spare bits 49 Not used, should be set to zero, reserved for future use
Total number of bits 168 The resulting Message 6 occupies 1 slot