ITU-Q931

The following table provides a summary of the MTP2 message structure included in this page:

Message format ITU-Q931 arrow_2_forward.gif (1040 octets)
List of  Messages types ITU-Q931 arrow_2_forward.gif (1040 octets)
List of IE types ITU-Q931 arrow_2_forward.gif (1040 octets)
List of Time-limits ITU-Q931 arrow_2_forward.gif (1040 octets)
List of Primitives of Service ITU-Q930 arrow_2_forward.gif (1040 octets)

Q931: Message format

- Octet 1: mandatory
bits 8-1 Protocol discriminator (08 H)
- Octet 2: mandatory
bits 8-5 0000
bits 4-1 Length of call reference value (1 or 2 octets)
- Octet 3: mandatory
bit 8 Call reference flag
set to 0 if the message is sent from the side that originates the call reference
set to 1 if the message is sent to the side that originates the call reference.
bits 7-1 Call reference value, assigned by the originating side of the interface for a call.
- Octet 4: exists only if octet 2 = 00000010
bits 8-1 Call reference value (Low order octet)
- Octet: mandatory
bit 8 0
bits 7-1 Message type
- Octets: optional
bits 8-1 One or several information element(s)

They are 2 possible structures:

bits 8 _ _ _ _ _ _ 1 len Information element
0 0 0 0 1 0 0 0 1 Protocol discriminator (08 H)
octets 2-3 2 Call reference (one octet value)
octet 4 1 Message type
octets 5-n Optional information element
bits 8 _ _ _ _ _ _ 1 len Information element
0 0 0 0 1 0 0 0 1 Protocol discriminator (08 H)
octets 2-4 3 Call reference (two octets value)
octet 5 1 Message type
octets 6-n Optional information element

Q931: List of message types

bits 8 _ _ _ _ _ _ 1 hex Message type
0 0 0 _ _ _ _ _ Call establishment messages
0 0 0 0 1 01 ALERTING
0 0 0 1 0 02 CALL PROCEEDING
0 0 1 1 1 07 CONNECT
0 1 1 1 1 0F CONNECT ACKNOWLEDGE
0 0 0 1 1 03 PROGRESS
0 0 1 0 1 05 SETUP
0 1 1 0 1 0B SETUP ACKNOWLEDGE
0 0 1 _ _ _ _ _ Call information phase messages
0 0 1 0 0 24 HOLD *
0 1 0 0 0 28 HOLD ACKNOWLEDGE *
1 0 0 0 0 30 HOLD REJECT *
0 0 1 1 0 26 RESUME
0 1 1 1 0 2E RESUME ACKNOWLEDGE
0 0 0 1 0 22 RESUME REJECT
1 0 0 0 1 31 RETRIEVE *
1 0 0 1 1 33 RETRIEVE ACKNOWLEDGE *
1 0 1 1 1 37 RETRIEVE REJECT *
0 0 1 0 1 25 SUSPEND
0 1 1 0 1 2D SUSPEND ACKNOWLEDGE
0 0 0 0 1 21 SUSPEND REJECT
0 0 0 0 0 20 USER INFORMATION
0 1 0 _ _ _ _ _ Call clearing messages
0 0 1 0 1 45 DISCONNECT
0 1 1 0 1 4D RELEASE
1 1 0 1 0 5A RELEASE COMPLETE
0 0 1 1 0 46 RESTART
0 1 1 1 0 4E RESTART ACKNOWLEDGE
0 1 1 _ _ _ _ _ Miscellaneous messages
1 1 0 0 1 79 CONGESTION CONTROL
0 0 0 1 0 62 FACILITY
1 1 0 1 1 7B INFORMATION
0 1 1 1 0 6E NOTIFY
0 0 1 0 0 64 REGISTER *
0 0 0 0 0 60 SEGMENT
1 1 1 0 1 7D STATUS
1 0 1 0 1 75 STATUS ENQUIRY

(*): Q932 recommendation.

Q931: List of IE types (see details)

The code values of the information element identifier (first octet of the IE) for the variable length formats are assigned in ascending numerical order, according to the actual order of appearance of each IE in a message. Single octet IE may appear at any point in the message.

Codeset 0

bits 8 _ _ _ _ _ _ 1 hex Single octet IE
1 0 0 1 _ _ _ _ 9_ Shift
0 1 0 0 0 0 0 A0 More Data
0 1 0 0 0 0 1 A1 Sending Complete
0 1 1 _ _ _ _ B_ Congestion Level
1 0 1 _ _ _ _ D_ Repeat Indicator
bits 8 _ _ _ _ _ _ 1 hex Variable length IE
0 0 0 0 0 0 0 0 00 Segmented Message
0 0 0 0 1 0 0 04 Bearer Capability
0 0 0 1 0 0 0 08 Cause
0 0 1 0 0 0 0 10 Call Identity
0 0 1 0 1 0 0 14 Call State
0 0 1 1 0 0 0 18 Channel Identification
0 0 1 1 1 0 0 1C Facility
0 0 1 1 1 1 0 1E Progress Indicator
0 1 0 0 0 0 0 20 Network Specific Facilities
0 1 0 0 1 1 1 27 Notification Indicator
0 1 0 1 0 0 0 28 Display
0 1 0 1 0 0 1 29 Date/Time
0 1 0 1 1 0 0 2C Keypad Facility
0 1 1 0 0 1 0 32 Information Request *
0 1 1 0 1 0 0 34 Signal
0 1 1 0 1 1 0 36 Switchhook
0 1 1 1 0 0 0 38 Feature Activation
0 1 1 1 0 0 1 39 Feature Indication
0 1 1 1 0 1 1 3B Endpoint Identifier *
0 1 1 1 0 1 0 3A Service Profile Identification *
1 0 0 0 0 0 0 40 Information Rate
1 0 0 0 0 1 0 42 End-to-end Transit Delay
1 0 0 0 0 1 1 43 Transit Delay Selection and Indication
1 0 0 0 1 0 0 44 Packet layer binary Parameters
1 0 0 0 1 0 1 45 Packet layer Window Size
1 0 0 0 1 1 0 46 Packet layer Size
1 1 0 1 1 0 0 6C Calling Party Number
1 1 0 1 1 0 1 6D Calling Party Subaddress
1 1 1 0 0 0 0 70 Called Party Number
1 1 1 0 0 0 1 71 Called Party Subaddress
1 1 1 0 1 0 0 74 Redirecting Number
1 1 1 0 1 1 0 76 Redirection Number
1 1 1 1 0 0 0 78 Transit Network Selection
1 1 1 1 0 0 1 79 RestarT indicator
1 1 1 1 1 0 0 7C Low-Layer Compatility
1 1 1 1 1 0 1 7D High Layer Compatibility
1 1 1 1 1 1 0 7E User-User
1 1 1 1 1 1 1 7F Escape for extension

(*): Q932 recommendation.

Codeset 0 ETSI

bits 8 _ _ _ _ _ _ 1 hex Variable length IE
1 0 0 0 1 1 0 0 8C Connected Number
1 0 0 0 1 1 0 1 8D Connected Subaddress

Codeset 5 (National-specific) Belgium

bits 8 _ _ _ _ _ _ 1 hex Variable length IE
0 0 0 1 1 0 1 0 1A Charging Advice

Codeset 5 (National-specific) Bellcore National ISDN

bits 8 _ _ _ _ _ _ 1 hex Variable length IE
0 0 0 1 1 1 0 1 1D Operator System Access

Codeset 6 (Network-specific) Belgium

bits 8 _ _ _ _ _ _ 1 hex Variable length IE
0 0 0 1 1 0 1 0 1A Charging Advice
0 1 1 1 0 1 0 0 74 Redirecting Number

Codeset 6 (Network-specific) FT-Numeris

bits 8 _ _ _ _ _ _ 1 hex Variable length IE
0 0 1 0 0 1 0 0 1D User Capability

Codeset 6 (Network-specific) Bellcore National ISDN

bits 8 _ _ _ _ _ _ 1 hex Variable length IE
0 1 1 1 0 1 0 1 75 Redirecting Subaddress
0 1 1 1 0 1 1 0 76 Redirection Number
0 1 1 1 1 0 1 1 7B Call appearance

Second octet

The second octet of a variable length IE indicates the total length of the contents of that IE, starting with octet 3.

Extension of octet N

bits 8 _ _ _ _ _ _ 1 Information element
1 _ _ _ _ _ _ _ octet N without extension
0 _ _ _ _ _ _ _ octet (N+1) extended with three octets
0 _ _ _ _ _ _ _ octet (N+1)a (first of extension domain)
0 _ _ _ _ _ _ _ octet (N+1)b (second of extension domain)
1 _ _ _ _ _ _ _ octet (N+1)c (end of extension domain)

Q931: List of time-limits

Time-limit of ETSI 300-102-1

Network side User side
Q931 300-102 Q931 300-102
T301 180s. 180s. 180s. 180s.
T302 10-15s 10-15s 15s 15s
T303 4s 4s 4s 4s
T304 20s 20s 15s 30s
T305 30s 30s 30s 30s
T306 30s
T307 3mn 3mn
T308 4s 4s 4s 4s
T309 90s 90s 90s 90s
T310 10s 10s 10s >40s
T312 T303+2s
T313 4s 4s
T314 4s 4s 4s 4s
T316 2mn 2mn 2mn 2mn
T317 < T316 < T316 < T316 < T316
T318 4s
T319 4s
T320 30s 4s 30s
T321 30s 30s 30s 30s
T322 4s 4s 4s 4s

Time-limit T301

T301 Network side User side
State Call received Call delivered
Start ALERT received. ALERT received.
Stop CONNECT received CONNECT received

Time-limit T302

T302 Network side User side
State Overlap sending Overlap receiving
Start SETUP-ACK sent, receipt of INFO, restarts T302 SETUP-ACK sent. Restart when INFO received
Stop With sending complete indication, or network alert, or connect request received INFO received with sending complete indication; or internal alerting; or internal connection; or a detemination that sufficient call information has been received

Time-limit T303

T303 Network side User side
State Call present Call initialized
Start SETUP sent SETUP sent
Stop ALERT, CONN, CALL PROC or SETUP-ACK received; REL-COMP received if SETUP sent on point-to-point data link ALERT, CONN, SETUP-ACK , CALL PROC, or REL-COMP received

Time-limit T304

T304 Network side User side
State Overlap receiving Overlap sending
Start SETUP-ACK received. Sending of INFO restarts T304 INFO transmitted.
Restart when INFO re-transmitted
Stop Send INFO; receive CALL PROC, ALERT or CONN CALL PROC, ALERT, CONN or DISC received

Time-limit T305

T305 Network side User side
State Disconnect indication Disconnect request
Start DISCONNECT without progress indicator N8 sent DISCONNECT sent
Stop REL or DISC received REL or DISC received

Time-limit T306
(ETS300-102-1 addendum)

T306 Network side User side
State Disconnect indication
Start DISCONNECT with progress indicator #8 sent
Stop RELEASE with DISCONNECT received

Time-limit T307

T307 Network side User side
State Null
Start SUSP-ACK sent
Stop RESUME received

Time-limit T308

T308 Network side User side
State Release request Release request
Start RELEASE sent RELEASE sent
Stop RELEASE or REL-COMP received RELEASE or REL-COMP received

Time-limit T309

T309 Network side User side
State Any stable state Any stable state
Start Data link disconnection . Calls in stable states are not lost Data link disconnection . Calls in stable states are not lost
Stop Data link reconnected Data link reconnected

Time-limit T310

T310 Network side User side
State Incoming call proceeding Outgoing call proceeding
Start CALL PROC received CALL PROC received
Stop ALERT, CONN or DISCONNECT received.
If DISC, retain cause and continue timing
ALERT, CONN, DISC or PROGRESS received

Time-limit T312

T312 Network side User side
State Call present, call abort, etc.
Start SETUP sent or resent on broadcast data link
Stop Timeout

Time-limit T313

T313 Network side User side
State Connect request
Start CONN sent
Stop CONN-ACK received

Time-limit T314

T314 Network side User side
State Receiving segmented message Receiving segmented message
Start Message segment received Message segment received
Stop Last message segment received Last message segment received

Time-limit T316

T316 Network side User side
State Restart request Restart request
Start RESTART sent RESTART sent
Stop RESTART-ACK received RESTART-ACK received

Time-limit T317

T317 Network side User side
State Restart Restart
Start RESTART received RESTART received
Stop Internal clearing of call references Internal clearing of call references

Time-limit T318

T318 Network side User side
State Resume request
Start RESUME sent
Stop RESUME-ACK or RESUME REJECT received

Time-limit T319

T319 Network side User side
State Suspend request
Start SUSPEND sent
Stop SUSPEND-ACK or SUSPEND-REJECT received

Time-limit T320
(ETS300-102-1 addendum)

T320 Network side User side
State B channel access active
D channel access null
Start B channel access: CONNECT sent or received
D channel access: DL-ESTABLISH-CONFIRM or DL-ESTABLISH-INDIC received
Stop Call request packet received; or Incoming call packet delivered; or DISC received
for D-channel access DL-REL-IND received

Time-limit T321

T321 Network side User side
State Any call state Any call state
Start D-channel failure D-channel failure
Stop Response to layer 3 message received Response to layer 3 message received

Time-limit T322

T322 Network side User side
State Any call state Any call state
Start STAT ENQUIRY sent STATUS ENQUIRY sent
Stop STATUS, DISC, REL or REL-COMP received STATUS, DISC, REL or REL-COMP received

Q931: List of primitives

  Primitives
   

 


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updated:  27-Feb-04