WPCL 2BJ|x ` H   x|@  6'6' Recommendation Q.764 Signalling procedures   1. General........................................................... 7 2. Basic call control and signalling procedures...................... 8 2.1 Successful call setup............................................ 8 2.2 Unsuccessful call setup.......................................... 30 2.3 Normal call release............................................... 31 2.4 Transfer of usertouser information.............................. 33 2.5 Suspend, resume................................................... 33 2.6 Delayed release................................................... 36 2.7 In call modification.............................................. 36 2.8 Echo control procedure............................................ 38 2.9 Network features.................................................. 41 2.10 Abnormal conditions............................................... 49 2.11 ISDN user part signalling congestion control...................... 63 2.12 Automatic congestion control...................................... 64 2.13 Unequipped circuit identification code message (national option)................................................. 65 3. Endtoend signalling............................................. 77 3.1 Introduction...................................................... 77 3.2 Passalong method................................................. 77 3.3 SCCP method....................................................... 78 3.4 Chaining of ISDN user part endtoend signalling connection....... 80 3.5 Use of the Protocol Control Indicator (PCI)....................... 81 3.6 Operation of the passalong method................................ 81 3.7 Operation of the SCCP methodconnectionless services.............. 82 3.8 Operation of the SCCP methodconnectionoriented service.......... 89 3.9 Interface elements between ISDN user part and SCCP (embedded transfer)............................................... 93 Appendix I (to  3): Contents of the interface elements between the ISDN user part and the SCCP.................. 97 Timers in Recommendation Q.764................... 98 Annex A: State transition diagrams (published in Document AP IX115/COM XIR 166)............................. Recommendation Q.762 [1] and their format and content are given in Recommendation Q.763 [2]. Recommendation Q.730 [3] contains the procedures for supplementary services. (These were previously  4 of Recommendation Q.764.) Hd) Transfer of information not included in the Initial Address Message   HH‚As an alternative to the inclusion of call setup user facility information in the Initial Address Message, any call setup user facility information that need not be examined at intermediate exchanges and which can be requested from by the destination exchange (see Recommendation Q.763,  3.22), may be transported between the originating and destination exchange. The method of transportation for this information can be by the linklink method (see section2.1.6) or via the endtoend methods (see section 3).  `   H Hd) Transfer of information not included in the Initial Address Message   HHAs an alternative to the inclusion of call setup user facility information in the Initial Address Message, any call setup user facility information that need not be examined at intermediate exchanges and which can be requested from by the destination exchange (see Recommendation Q.763,  3.22), may be transported between the originating and destination exchange. The method of transportation for this information can be by the linklink method (see section2.1.6) or via the endtoend methods (see section 3).  ` H  `    @  when digit analysis or timer (T10), or receipt of the Address Complete Message indicates that all digits have beenreceived. HHX X    Ha)h  If an indication that the address is complete or no status indication has been received from the ISDN access prior to the destination exchange determining that the complete called party number has been received, the indicators in the Address Complete Message will be set as follows: significant digits in the called party number may be amended or omitted (see section 2.1.1.1 b)). A change of the  X 2.1.4.9 Return of subaddress information in Address Complete Message, Connect HMessage or Call Progress Message     X If subaddress information is received from the called access this information  is passed unchanged to the originating exchange in the access transport parameter of the Address Complete Message, Connect Message or Call Progress Message.  `    Щ if all the information is not available locally or remotely, then an  h  Information Message containing only the available information is sent and the requested but not delivered information is indicated as "not available", using either the indication in the Information Indicator or an appropriate coding in the requested parameter. 2.1.6.3 Sending unsolicited information  ,ԌInformation that is available at an exchange and that does not correspond to information which can be or has been requested by an Information Request Message, can be sent in the Information Message with the solicited information indicator set to signify that the message has been sent unsolicited. The unsolicited Information Message can be used only if the ISDN user part has been used all the way. It can be sent in any direction in any call state (except in the awaiting release complete state). Solicited and unsolicited information must not be sent in the same Information Message; if unsolicited information is to be sent at the same time together with solicited information, this has to be done in a separate message with the Solicited Information Indicator set to "Unsolicited". 2.1.6.4 Receiving an Information Message Upon receipt of an Information Message which does neither contain the requested information or an indication that the requested information is not available, the actions taken will depend on whether the call can be progressed. Address Message is the same as described in section 2.1.1.1 c). The only purpose of the Subsequent Address Message is to carry further digits.  The initiating exchange immediately starts the release of the switched path (if established). The exchange sends a Release Message to the preceding exchange and a timer (T1) is started to ensure that a Release Complete Message is received from the preceding exchange within time T1. (Expiration of Timer (T1) is covered in 2.10.6) (i.e. the exchange controlling the call) (see section 2.2.4); or (as described in section 2.2.4). (ed note word PROCEDURES removed) The Suspend Message indicates a temporary cessation of communication without releasing the call. It can only be accepted during the conversation/data phase. A Suspend Message can be either generated in response to a suspend request from the calling/called party or generated by the network in response to a clearback indication from an interworking node or an onhook condition from an analogue called (telephone) party. (ed note 'called party' removed) A suspend Message can be generated by the network in response to a clearback indication from an interworking node or an on hook condition from an analogue called party. a) Action at the terminating exchange (destination) or an interworking exchange On receipt of the on hook condition or clearback indication or Suspend Message, the controlling exchange starts a timer (T6) to ensure that an off hook condition, a reanswer indication, a Resume (network) Message or a Release Message is received. The value of this timer (T6) is covered in Q.118 [11]. If the timer (T6) expires, the procedures in Section 2.5.3. [1] apply. Having initiated a suspend condition, a calling party may request a reconnection within timer T2. The procedures in Section 2.5.1.1 items a), b) and c) apply except that the Resume Message replaces the Suspend Message. On receipt of the Resume Message, the controlling exchange cancels the timer. (T2) A Resume Message is initiated by the network, if a Suspend Message had previously been sent, in response to a reanswer indication from an interworking node or an off hook condition from an analogue called party. a) Action at the terminating exchange or interworking exchange On receipt of a reanswer indication at the interworking exchange or an off hook condition in the terminating exchange, the exchange may send a Resume (network) Message to the preceding exchange if a Suspend (network) Message had previously been sent. c) Action of the controlling exchange (i.e. that exchange controlling the call) Recommendation Q 118) [11] then the controlling exchange will initiate the release procedure outlined in section 2.3.3. At the start of the call, it is required to know whether the call is an alternate speech/64 kbit or alternate 64 Kbit/speech unrestricted call request. If this is the case then the following procedures apply: On receipt of a Call Modification Completed Message, the intermediate exchange modifies the resource and, when complete, sends a Call Modification Completed Message to the next exchange. Actions required at the local exchange receiving the request call  for incall modification 2.7.2.3 Action required at the remote local exchange  receiving the call modification request from the netowork. If at the remote local exchange the in call modification cannot be performed, the characteristics of the transmission path are kept in the current mode and the Call Modification Reject Message is returned to the netowrk. If resources have been reserved upon reception of the Call modification Request Message, they are released. 2.8 Echo Control Procedure 2.7.2.1 Actions required at the local exchange initiating the call modificationn a) When the nature of connection indicators parameter field in the IAM indicates that an echo control device is already included: no change to the nature of connection indicators parameter field in the IAM is made; an incoming half echo control device is reserved; and any outgoing half echo control device is disabled. b) When the nature of connection indicators parameters in the IAM does not indicate that an echo control device is already included: ,Ԍ an outgoing half echo control device is enabled; and the echo control device indicator in the Nature of connection indicators parameter field is set. a) When the nature of connection indicators parameter field the IAM indicates that echo control device is already included: no change to the nature of connection indicators parameter field in the IAM is made; and an incoming half echo control device is reserved. b) When the nature of connection indicator parameters field in the IAM does not indicate that an echo control device is already included: no additional action is required. Upon the receipt of an IAM with the indication "outgoing half echo control device included" in the nature of connection indicators parameter field, the following action is taken: the echo control device indicator of the backward call indicators parameter field in the first backward message (i.e. ACM or Connect or Call Progress) is set. If the destination exchange is unable to include an incoming half echo control device, the information is conveyed to the preceding exchange by echo a control device indicator in the nature of connection indicators field not being set in the first backward message. Upon receipt of the first backward message (i.e. ACM or Connect or Call Progress) in response to an IAM with echo control indication, then one of the following action can occur: a) When the backward call indicators parameter field indicates that incoming half echo control device is already included: b) When the backward call indicators parameter field indicates that an incoming half echo control device is already included: is made. Automatic repeat attempt, as defined in Recommendation Q.12 [12], is provided in signalling system No 7. An automatic repeat attempt will be made (up to the point when the Initial Address Message information is released. See section 2.3.4. In the event of a Blocking Message being received: after an Initial Address Message has been sent in the opposite direction on that circuit, and before a backward message relating to that call has been received, an automatic repeat attempt will be made on another circuit. The exchange receiving the Blocking Message releases the original call attempt in the normal manner after sending the Blocking Acknowledgement message and will not seize that circuit for subsequent calls. If the Blocking Message is received: A circuit is controlled by the ISDN User Part if it can be used by the ISDN User Part as a circuit switched bearer. Hence, time slots in a digital path that are used for synchronisation (e.g. time slot 0 in a 2048 kbit/s digital path) or as signalling channels are not circuits whose control is allocated to the ISDN User Part. be received from the called party. If a destination exchange [9], section 7. [9], section 9. all parameters in the Initial Address Message. The contents of the Initial Address Message information shall be updated, if the value of parameters change during the call setup. have chosen a suitable route (e.g. 64 kbit/s and ISDN user part signalling used all the way) according to information included in the Initial Address Message. Message, the controlling exchange starts a timer (T2) to ensure that a resume request or Resume Message is received within timer T2). If the timer (T2) expires, the procedures in section 2.5.3 apply. Ha) Action at the terminating exchange or interworking exchange On receipt of a reanswer indication at the interworking exchange or an offhook condition in the terminating exchange, the exchange may send a Resume (network) Message to the preceding exchange if a Suspend (network) Message had previously been sent. Hb) Actions of the intermediate exchange On receipt of a Resume Message the exchange will send a Resume Message to the preceding exchange. Hc) Action of the controlling exchange (i.e. that exchange controlling call) On receipt of the offhook condition, reanswer signal, Release message or Resume Message the controlling exchange stops the timer (T6) (started in paragraph 2.5.1.3. b). 2.5.3 Expiration of timer (T2) or timer T6 If a request for reconnection or a Resume Message is not received within timer (R2) or timer (T6) covered in Recommendation Q 118 [11] then the controlling exchange will initiate the release procedure outlined in section 2.3.3. condition is removed or the timer (T3) *) matures, the network generates the normal release sequence(section 2.3.3). Ha) When the nature of connection indicators parameter field in the IAM indicates that an echo control device is already included H no change to the nature of connection indicators parameter field in the IAM is made; H an incoming half echo control device is reserved; and H any outgoing half echo control device is disabled. Hb) When the nature of connection indicators parameters in the IAM does not indicate that an echo control device is already included: H an outgoing half echo control device is enabled; and H the echo control device indicator in the Nature of connection indicators parameter field is set. If the intermediate exchange has sufficient information to to determine that echo control is not required for the outgoing circuit then one of the following actions can occur: Ha) When the nature of connection indicators parameter field in the IAM indicates that echo control device is already included: H no change to the nature of connection indicators parameter field in the IAM is mad; and H an incoming half echo control device is reserved. Hb) When the nature of connection indicator parameter field in the IAM does not indicate that an echo control device is already included: H no additional action is required. K  `  A ;AP IX114E KJ  `  A ;AP IX114E J  8MREFERENCESă XH[1]XCCITT Recommendation Q.762 General functions of messages and signals. [2]XCCITT Recommendation Q.763 Formats and codes. [3]XCCITT Recommendation Q.730 ISDN supplementary services. [4]XCCITT Recommendation E.163 Numbering plan for the international telephone Qp&Rservice. [5]XCCITT Recommendation E.164 Numbering plan for the ISDN era. [6]XCCITT Recommendation Q.107 Standard sending sequence of forward address information.  `  [7]XCCITT Recommendation E.172 Call routing in the ISDN era.   [8]XCCITT Recommendation Q.33 Protection against the effects of faulty transmission on groups of circuits. [9]XCCITT Recommendation Q.724 Signalling procdedures. [10]HCCITT Recommendation Q.543 Digital exchange performance design objectives. [11]HCCITT Recommendation Q.118 Special release arrangements. [12]HCCITT Recommendation Q.12 Overflowalternative routingrerouting K#Lautomatic repeat attempt. [13]HCCITT Recommendation Q.706 Message Transfer Part signalling performance.   [14]HCCITT Recommendation Q.714 Signalling Connection Control Part @Qp&B procedures.  h [15]HCCITT Recommendation Q.711 Functional description of the Signalling Connection Control Part. xxxxxxxxxx H Annex A (to Recommendation Q.764) 8FSTATE TRANSITION DIAGRAMS Page A.1 General........................................................6 A.2 Drafting convention............................................6 A.3 Abbreviations, timers and primitives...........................7 A.4 State transition diagrams and SDL diagrams.....................7 8OANNEX A 8R 8F(to Recommendation Q.764) 8R 8FState transition diagramsă HShould any conflict arise between the text and the SDL definition, the textual description is taken as definitive. A.1HGeneral HThis Annex contains the description of the signalling procedures described in this Recommendation in the form of state transition diagrams according to the CCITT Specification and Description Language (SDL). In order to facilitate functional description, the ISDN User Part (ISDNUP) signalling procedure is divided into main functional blocks, as shown in Figure A1/Q.764. These blocks are as follows: H1)h  Signalling Procedure Control (SPRC) HSPRC provides procedures for sending ISUP messages to Level 3 (SCCP or MTP) and distributing received ISUP messages to the other ISUP functional blocks. H2)h  Call Processing Control (CPC) HCPC provides call control procedures for realizing basic circuit switched service according to user's request. H3)h  Circuit Supervision Control (CSC) HCSC provides procedures for circuit supervision control for maintenance purpose and for recovery from abnormal situation. A.2HDrafting convention Ha)  External inputs and outputs are used for interactions with a remote exchange and interaction between SPRC and the other functional blocks. Internal inputs and outputs are used for interactions within each functional block, e.g., to indicate control of timeout. For these interactions, input and output symbols are used as shown in Figure A2/Q.764. Hb)  Inputs and outputs symbols contain as part of their name acronyms of their source and destination functional block names with an arrow in between, e.g., Blocking BLS > CPC. Hc)  A simple example of SDL diagram according to the above conventions is shown in Figure A3/Q.764. A.3HAbbreviations, timers and primitives A.3.1HAbbreviations H1)  Signalling Procedure Control: Table A1/Q.764 H2)  Call Processing Control: Table A2/Q.764 H3)  Circuit Supervision Control: Table A3/Q.764 A.3.2HTimers HTimers used in the ISDNUP SDL diagrams are shown in TableA4/Q.764. A.3.3HPrimitives HPrimitives used over the interface between Call Control and ISDNUP are shown in Table A5/Q.764. A.4HState transition diagrams and SDL diagrams HEach ISDNUP main functional block is further subdivided into the functional blocks. Functional diagrams and simple state transition diagrams for each main functional block are shown below: H1)  Signalling Procedure Control (SPRC) H Functional diagrams:Figure A4/Q.764 H State transition diagrams:Figure A5/Q.764 H2)  Call Processing Control (CPC) H Functional diagrams:Figure A6/Q.764 H State transition diagrams:Figure A7 9/Q.764 H3)  Circuit Supervision Control (CSC) H Functional diagrams:Figure A10/Q.764 H State transition diagrams:Figure A11 18/Q.764 HThe ISDNUP SDL diagrams are described based on the threeblocks approach. In this approach Call control, which provides signalling independent functions such as connect through, circuit selection and digits analysis is outside the ISDNUP. These functions are described only in sections 14. The ISDNUP diagrams are provided for the above subdivided functional blocks, as shown below: H1)  Signalling Procedure Control (SPRC) H Message Sending Control:Figure A19/Q.764 H Message Distributing Control:Figure A20/Q.764 H2)  Call Processing Control (CPC) H Call Processing Control Incoming H (CPCI):Figure A21/Q.764 H Call Processing Control Outgoing H (CPCO):Figure A22/Q.764 H Continuity Check Incoming (CCI):Figure A23/Q.764 H Continuity Check Outgoing (CCO):Figure A24/Q.764 H3)  Circuit Supervision Control (CSC) H Blocking/Unblocking Message Sending H (BLS):Figure A25/Q.764 H Blocking/Unblocking Message H Reception (BLR):Figure A26/Q.764 H Maintenance Oriented Circuit Group H Blocking/Unblocking Sending (MGBS):Figure A27/Q.764 H Maintenace Oriented Circuit Group H Blocking/Unblocking Reception H (MGBR):Figure A28/Q.764 H Hardware Failure Oriented Locally H Blocking State (HLB):Figure A29/Q.764 H Hardware Failure Oriented Remotely H Blocking State (HRB):Figure A30/Q.764 H Hardware Failure Oriented Circuit H Group Blocking/Unblocking Sending .,ԌH (HGBS):Figure A31/Q.764 H Hardware Failure Oriented Circuit H Group Blocking/Unblocking Reception H (HGBR):Figure A32/Q.764 H Circuit Reset Sending (CRS):Figure A33/Q.764 H Circuit Reset Reception (CRR):Figure A34/Q.764 H Circuit Group Reset Sending (CGRS):Figure A35/Q.764 H Circuit Group Reset Reception H (CGRR):Figure A36/Q.764 H Continuity Recheck Sending (CRCS):Figure A37/Q.764 H Continuity Recheck Reception H (CRCR):Figure A38/Q.764 H Circuit Group Query Sending (CQS):Figure A39/Q.764 H Circuit Group Query Reception H (CQR):Figure A40/Q.764 8JFIGURE A1/Q.764 8R 8<Overview Functional Block Diagram for ISDNUPă HNote Input which is not shown in SDL diagrams should be discarded. 8JFIGURE A2/Q.764 8R 8DSymbols Used In SDL Diagramsă 8JFIGURE A3/Q.764 8R 8GSDL Convention Exampleă 8KTABLE A1/Q.764 8R 8@Signalling Procedure Control Acronymă 8R 8KTABLE A2/Q.764 8R 8CCall Processing Control Acronymă 8KTABLE A3/Q.764 8R 8ACircuit Supervision Control Acronymă 8R 8KTABLE A4/Q.764 8R 8OTimersă 8KTABLE 15/Q.764 8R 8MPrimitivesă 8R 8JFIGURE A4/Q.764 8R 8BFunctional Block Diagram for SPRCă 8JFIGURE A5/Q.764 8R 8AState Transition Diagrams for SPRCă 8JFIGURE A6/Q.764 8R 8BFunctional Block Diagram for CPCă 8JFIGURE A7/Q.764 8R 8:State Transition Diagrams for CPC Incoming (CPCI)ă 8JFIGURE A8/Q.764 8R 8:State Transition Diagrams for CPC Outgoing (CPCO)ă XH