SS7 ISUP Message Format, Messages, Parameters and Timers









SS7 ISUP Message Format :


ISDN User Part Messages are carried on the signaling link by means of signal units. The service indicator for ISUP signaling is coded 0101.

The signaling information field of each signaling system 7 ISUP message consists of the following parts.

a) Routing label :

For each individual circuit connection, the same routing label must be used for each message that is transmistted for that connection.

b) CIC - Circuit Identification Code :

Network use CIC to identify which call circuit refers which signal.


c)Message Type Code :

Consists of one octet field and it's mandatory for all messages. It uniquely defines the function and format of each ISUP message. Such as IAM, ACM, ANM etc.

d) The mandatory fixed part :

These are fixed length mandatory parameters that every message should have. The position, length and order of parameters is uniquely defined by the message type. For this reason, the names of the parameters and the length of the indicators are not included in the message.

e) The mandatory variable part :

Variable length mandatory parameters will be included in the mandatory variable part. Pointers are used to indicate the beginning of each parameter. Each pointer is encoded as a single octet. The name of the parameter and the order in which the parameters are sent is implicit in the message type. The parameters names are not included in the message. A pointer is also included to indicate the beginning of the optional part. Each parameter contains the parameter length indicator followed by the contents of the parameter.

f) The optional part

The optional part consists of parameters that may or may not occur in particular message type. Both fixed and variable length parameters may be included. Optional parameters can be transmitted in any order. Each optional parameter will include a parameter name (one octet) and the length indicator (one octet) followed by the parameter contents. After all parameters have been sent, an "end of optional parameters" octet which contains all zeros will be transmitted.


SS7 ISUP Messages, Parameters and Timers:




Isup Messages
ISUP Messages Binary Values Hex Values
Address complete 00000110 06
Answer 00001001 09
Blocking 00010011 13
Blocking acknowledgement 00010101 15
Call progress 00101100 2C
Circuit group blocking 00011000 18
Circuit group blocking acknowledgement 00011010 1A
Circuit group query 00101010 2A
Circuit group query response 00101011 2B
Circuit group reset 00010111 17
Circuit group reset acknowledgement 00101001 29
Circuit group unblocking 00011001 19
Circuit group unblocking acknowledgement 00011011 1B
Charge information 00110001 31
Confusion 00101111 2F
Connect 00000111 07
Continuity 00000101 05
Continuity check request 00010001 11
Facility 00110011 33
Facility accepted 00100000 20
Facility reject 00100001 21
Facility request 00011111 1F
Forward transfer 00001000 08
Identification request 00110110 36
Identification response 00110111 37
Information 00000100 04
Information request 00000011 03
Initial address 00000001 01
Loop back acknowledgement 00100100 24
Network resource management 00110010 32
Overload 00110000 30
Pass-along 00101000 28
Release 00001100 0C
Release complete 00010000 10
Reset circuit 00010010 12
Resume 00001110 0E
Segmentation 00111000 38
Subsequent address 00000010 02
Suspend 00001101 0D
Unblocking 00010100 14
Unblocking acknowledgement 00010110 16
Unequipped CIC 00101110 2E
User Part available 00110101 35
User Part test 00110100 34
User-to-User information 00101101 2D








Isup Parameters
ISUP Parameters Binary Values Hex Values
Access delivery information 00101110 2E
Access transport 00000011 03
Automatic congestion level 00100111 27
Backward call indicators 00010001 11
Call diversion information 00110110 36
Call history information 00101101 2D
Call reference 00000001 01
Called party number 00000100 04
Calling party number 00001010 0A
Calling party's category 00001001 09
Circuit state indicator 00100110 26
Cause indicators 00010010 12
Circuit group supervision message type indicator 00010101 15
Closed user group interlock code 00011010 1A
Connected number 00100001 21
Connection request 00001101 0D
Continuity indicators 00010000 10
Echo control information 00110111 37
End of optional parameters 00000000 00
Event information 00100100 24
Facility indicator 00011000 18
Forward call indicators 00000111 07
Free phone indicators 01000001 41
Generic digits 11000001 C1
Generic notification 00101100 2C
Generic number 11000000 C0
Generic reference 01000010 42
Hop counter 00111101 3D
Information indicators 00001111 0F
Information request indicators 00001110 0E
Location number 00111111 3F
MCID request indicator 00111011 3B
MCID response indicator 00111100 3C
Message compatibility information 00111000 38
MLPP precedence 00111000 38
Nature of connection indicators 00000110 06
Network specific facilities 00101111 2F
Optional backward call indicators 00101001 29
Optional forward call indicators 00001000 08
Original called number 00101000 28
Origination ISC point code 00101011 2B
Parameter compatibility information 00111001 39
Propagation delay counter 00110001 31
Range and status 00010110 16
Redirecting number 00001011 0B
Redirection information 00010011 13
Redirection number 00001100 0C
Redirection number restriction 01000000 40
Remote operations 00110010 32
Service activation 00110011 33
Signaling point code 00011110 1E
Subsequent number 00000101 05
Suspend/resume indicators 00100010 22
Transit network selection 00100011 23
Transmission medium requirement 00000010 02
Transmission medium requirement prime 00111110 3E
Transmission medium used 00110101 35
User service information 00011101 1D
User service information prime 00110000 30
User teleservice information 00110100 34
User-to-User indicators 00101010 2A
User-to-User information 00100000 20




Isup Timers
Symbol Default Value Acceptable Range Signal/Event
T1 15 sec. 15-60 sec. Release/Release Complete
T2 3 min. 3 min. Suspend/Resume
T5 5 min. 5-15 min. Release/Release Complete
T6 1 min. 1-2 min. On-hook, Reanswer
T7 20 sec. 20-30 sec. Initial Address, Address Complete, Subsequent Address, Connect
T8 10 sec. 10-15 sec.
T9 3 min. 1.5 - 3 min. Address Complete, Answer
T10 4 sec. 4-6 sec. Last Digit Timer
T11 20 sec. 15-20 sec. Initial Address, Address Complete, Subsequent Address
T12 15 sec. 15-60 sec. User Part Available, UA
T13 5 min. 5-15 min. Blocking, Blocking Ack.
T14 15 sec. 15-60 sec. Unblocking, Unblocking Ack.
T15 5 min. 5-15 min. Unblocking, Unblocking Ack.
T16 15 sec. 15-60 sec. Reset Circuit, Release Complete
T17 5 min. 5-15 min. Reset Circuit, Release Complete
T18 15 sec. 15-60 sec. Circuit Group Blocking, Circuit Group Blocking Ack.
T19 5 min. 5-15 min. Circuit Group Blocking, Circuit Group Blocking Ack.
T20 15 sec. 15-60 sec.
T21 5 min. 5-15 min. Circuit Group Unblocking, Circuit Group Unblocking Ack.
T22 15 sec. 15-60 sec.
T23 5 min. 5-15 min.
T24 1.9 sec. 2 sec.
T25 5 sec. 1-10 sec.
T26 2 min. 1-3 min.
T27 4 min. 4 min.
T28 10 sec. 10 sec. SQM, SQR
T29 300 ms. 300-600 ms.
T30 5 sec. 5-10 sec.
T33 12 sec. 12-15 sec.
T34 2 sec. 2-4 sec.
T35 15 sec. 15-20 sec. Digit Collection
T36 10 sec. 10-15 sec.
T38 3 min. 2-3 min. On-hook, Reanswer
T39 12 sec. 12-15 sec. Information Request, Information


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