1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 1 TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU(11/88)SERIES Q: SWITCHING AND SIGNALLINGSpecifications of Signalling System No. 7 Telephone user partthe heading codes and detailedmessage formats are described in 3.1.2 The service information octetThe serv
2、ice information octet comprises the service indicator and the subservice field.The service indicator is used to associate signalling information with a particular User Part and is only usedwith message signal units (see Recommendation Q.704, 12.2).The information in the subservice field permits a di
3、stinction to be made between national and internationalsignalling messages. In national applications when this discrimination is not required possibly for certain national UserParts only, the subservice field can be used independently for different User Parts.The format of the service information oc
4、tet is shown in Figure 1/Q.723.Figure 1/Q.723 - CCITT 35510 = 3 CMThe following codes are used in the fields of the service information octet:a) The service indicator is coded 0100.b) Subservice field.bits B A Spare (see Note)bits D C Network indicator0 0 International network0 1 Spare (for internat
5、ional use only)1 0 National network1 1 Reserved for national useNote The two unused bits in the service information octet are spare for possible future needs that may requirea common solution for all international User Parts and Message Transfer Part level 3. The bits are coded 00.2 Fascicle VI.8 Re
6、c. Q.7231.3 Format principlesThe user generated information in the signalling information field is, in general, divided into a number ofsubfields which may be either of fixed or variable length. For a given message type identified by a unique messageheading, the presence of a given subfield may be e
7、ither mandatory or optional. The various types of subfields are furtherdefined below.1.3.1 Mandatory subfieldsSubfields which have been declared mandatory for a given message type appear in all messages of that type.1.3.2 Optional subfieldsSubfields which have been declared optional for a given mess
8、age type only appear when required in messagesof that type. The presence or absence of each optional field is indicated by the state of a field indicator located in anindicator field, which in this case is a mandatory subfield.1.3.3 Fixed length subfieldsSubfields which have been declared fixed leng
9、th for a given message type, contain the same number of bits inall messages of that type.1.3.4 Variable length subfieldsFor subfields which have been declared variable length for a given message type, the number of bits may varybetween messages of that type. The size of a variable length subfield is
10、 indicated in an immediately preceding fixedlength subfield in terms of a predefined unit such as bits, octets or half-octets.1.3.5 Order of subfield transmissionFor a given type of message the various types of subfields are transmitted in the following order:a) mandatory subfields,b) optional subfi
11、elds.Within each of these two classes, the order of subfield transmission is, in general, as follows:1) fixed length subfields (with the exception of the indicator field and subfields indicating the size of avariable length subfield),2) variable length subfields.1.3.6 Order of bit transmissionWithin
12、 each defined subfield the information is transmitted least significant bit first.1.3.7 Coding of spare bitsSpare bits are coded 0 unless indicated otherwise.2 Label2.1 GeneralThe label is an item of information which forms part of every signalling message and is used by the messagerouting function
13、at Message Transfer Part level 3 to select the appropriate signalling route and by the User Part functionto identify the particular transaction (e.g. the call) to which the message pertains.In general, label information encompasses an explicit or implicit indication of the message source anddestinat
14、ion and, depending on the application, various forms of transaction identification.Fascicle VI.8 Rec. Q.723 3For messages which are related to circuits or calls, the transaction is conveniently identified by including thecorresponding circuit identity in the label. This technique applies to messages
15、 which pass between adjacent nodes, and tomessages which pass between nodes which are not adjacent; in this case the technique is known as the pass-alongmethod. In future, the introduction of new subscriber services may require the transfer of call related messages betweenexchanges at a time when no
16、 circuit is associated with the call. Such messages could be carried using the services of theSignalling Connection Control Part SCCP 6. In this case the standard access to the Signalling Connection Control Partis used.Note The service information octet, the routing label and the circuit identificat
17、ion code are not included inthe information transferred between the Telephone User Part and the Signalling Connection Control Part.One standard label format is specified ( 2.2) for international use. The same standard label is applicable fornational use; admitted deviations from the format of the st
18、andard label are described in 2.3.2.2 Standard telephone label2.2.1 Label formatThe standard label has a length of 40 bits and is placed at the beginning of the signalling information field.The label structure is as shown in Figure 2/Q.723.Figure 2/Q.723 (CCITT 35520) = 3 CMThe destination point cod
19、e (DPC) indicates the signalling point for which the message is intended, while theoriginating point code (OPC) indicates the signalling point which is the source of the message. The circuit identificationcode (CIC) indicates one speech circuit among those directly interconnecting the destination an
20、d the originating points.The portion of the label that consists of the destination point code and originating point code fields and of thefour least significant bits of the circuit identification code field corresponds to the standard routing label specified inRecommendation Q.704, 13.2.2.2.2 Destin
21、ation and originating point codesThe standard label structure requires that each telephone exchange in its role as signalling point is allocated acode from code plans established for the purpose of unambiguous identification of signalling points.Separate code plans will be used for the international
22、 signalling network and for different national signallingnetworks.The principles of code allocation which apply to the international signalling network should be in accordancewith Recommendation Q.708.The destination point code will be the code applicable to the telephone exchange to which the messa
23、ge is sent.The originating point code will be the code applicable to the telephone exchange from which the message is sent.2.2.3 Circuit identification codeThe allocation of circuit identification codes to individual telephone circuits is determined by bilateralagreement and/or in accordance with ap
24、plicable predetermined rules.4 Fascicle VI.8 Rec. Q.723Allocation rules for certain applications are defined below:a) 2048 kbit/s digital pathFor circuits which are derived from a 2048-kbit/s digital path (Recommendations G.732 1and G.734 2) the circuit identification code contains in the 5 least si
25、gnificant bits a binary representationof the actual number of the time slot which is assigned to the speech circuit. The remaining bits in thecircuit identification code are used where necessary, to identify one among several systemsinterconnecting an originating and destination point.b) 8448 kbit/s
26、 digital pathFor circuits which are derived from a 8448-kbit/s digital path (Recommendation G.744 3 and G.746 4)the circuit identification code contains in the 7 least significant bits an identification of the channel whichis assigned to the speech circuit. The codes in Table 1/Q.723 are used.The re
27、maining bits are used, where necessary, to identify one among several systems interconnecting anoriginating and destination point.c) Frequency division multiplex (FDM) systems in networks using the 2048-kbit/s pulse code modulationstandardFor FDM systems existing in networks that also use the 2048-k
28、bit/s pulse code modulation standard, thecircuit identification code contains in the 6 least significant bits the identification of a channel within agroup of 60 channels carried by 5 basic FDM groups which may or may not be part of the samesupergroup.The codes in Table 2/Q.723 are usedTABLE 1/Q.723
29、0000000 channel 10000001 channel 2|0011111 channel 320100000 channel 33|1111110 channel 1271111111 channel 128Fascicle VI.8 Rec. Q.723 5TABLE 2/Q.7232.3 Optional national labelsFor the purpose of satisfying the requirements imposed by specific characteristics of some national signallingnetworks, fie
30、ld sizes different from those specified for the standard label are admitted for the destination point code,originating point code and circuit identification code fields in national labels.3 Telephone signal message formats and codes3.1 GeneralAll telephone signal messages contain a heading consistin
31、g of two parts, heading code H0 and headingcode H1. Code H0 identifies a specific message group (see Recommendation Q.722, 3.2.1) while H1 either contains asignal code or in case of more complex messages, identifies the format of these messages. The allocation of the H0 andH1 code is summarized in T
32、able 3/Q.723.000000 unallocated000001 channel 1| | 1st basic (FDM) group001100 channel 12001101 channel 1001110 channel 2001111 channel 3010000 unallocated 2nd basic (FDM) group010001 channel 4|011001 channel 12011010 channel 1|011111 channel 6100000 unallocated 3rd basic (FDM) group100001 channel 7
33、|100110 channel 12100111 channel 1|101111 channel 9110000 unallocated 4th basic (FDM) group110001 channel 10110010 channel 11110011 channel 12110100 channel 1| | 5th basic (FDM) group111111 channel 126 Fascicle VI.8 Rec. Q.723TABLE 3/Q.723Heading code allocationMessageGroupH1H00000 0001 0010 0011 01
34、00 0101 0110 0111 1000 1001 1010 1011 1100 1101 1110 11110000 Spare, reserved for national useFAM 0001 IAM IAI SAM SAOFSM 0010 GSM COT CCFBSM 0011 GRQSBM 0100 ACM CHGUBM 0101 SEC CGC NNC ADI CFL SSB UNN LOS SST ACB DPN MPR EUMCSM 0110 ANU ANC ANN CBK CLF RAN FOT CCLCCM 0111 RLG BLO BLA UBL UBA CCR R
35、SCGRM 1000 MGB MBA MGU MUA HGB HBA HGU HUA GRS GRA SGBa)SBAa)SGUa)SUAa)1001 RESERVEDCNM 1010 ACC Spare reserved for international1011and basic national use110011011110Spare, reserved for national use1111a)National option.Fascicle VI.8 Rec. Q.723 7Abbreviations used in Table 3/Q.723ACB Access barred
36、signalACC Automatic congestion control information messageACM Address complete message (note)ADI Address incomplete signalANC Answer signal, chargeANN Answer signal, no chargeANU Answer signal, unqualifiedBLA Blocking-acknowledgement signalBLO Blocking signalBSM Backward set-up messageCBK Clear-back
37、 signalCCF Continuity-failure signalCCL Calling party clear signalCCM Circuit supervision messageCCR Continuity-check-request signalCFL Call-failure signalCGC Circuit-group-congestion signalCHG Charging messageCLF Clear-forward signalCNM Circuit network management message groupCOT Continuity signalC
38、SM Call supervision messageDPN Digital path not provided signalEUM Extended unsuccessful backward set-up informationmessageFAM Forward address messageFOT Forward-transfer signalFSM Forward set-up messageGRA Circuit group reset-acknowledgement messageGRM Circuit group supervision messagesGRQ General
39、request messageGRS Circuit group reset messageGSM General forward set-up information messageHBA Hardware failure oriented groupblocking-acknowledgement messageHGB Hardware failure oriented group blocking messageHGU Hardware failure oriented group unblocking messageHUA Hardware failure oriented group
40、 unblocking-acknowledgement messageIAI Initial address message with additional informationIAM Initial address messageLOS Line-out-of-service signalMBA Maintenance oriented group blocking-acknowledgement messageMGB Maintenance oriented group blocking messageMGU Maintenance oriented group unblocking m
41、essageMPR Misdialled trunk prefixMUA Maintenance oriented group unblocking-acknowledgement messageNNC National-network-congestion signalRAN Reanswer signalRLG Release-guard signalRSC Reset-circuit signalSAM Subsequent address messageSAO Subsequent address message with one signalSBA Software generate
42、d group blocking-acknowledgementmessageSBM Successful backward set-up information messageSEC Switching-equipment-congestion signalSGB Software generated group blocking messageSGU Software generated group unblocking messageSSB Subscriber-busy signal (electrical)SST Send-special-information tone signa
43、lSUA Software generated group unblocking-acknowledgementUBA Unblocking-acknowledgement signalUBL Unblocking signalUBM Unsuccessful backward set-up information messageUNN Unallocated-number signalNote Each address complete message contains one of the following signals: ADC Address-complete, charge AD
44、N Address-complete, no charge ADX Address-complete, coin box AFC Address-complete, charge subscriber free AFN Address-complete, no charge, subscriber free AFX Address-complete, coin box, subscriber free8 Fascicle VI.8 Rec. Q.7233.2 Heading code H0The heading code H0 occupies the 4-bit field followin
45、g the label and is coded as follows:0000 spare, reserved for national use0001 forward address messages0010 forward set-up messages0011 backward set-up request messages0100 successful backward set-up information messages0101 unsuccessful backward set-up information messages0110 call supervision messa
46、ges0111 circuit supervision messages1000 circuit group supervision messages1001 reserved1010 circuit network management messages1011 reserved for international and basic national use1100 to1111reserved for national use3.3 Forward address messagesThe following types of forward address messages are sp
47、ecified and are each identified by a different headingcode H1: Initial address message. Initial address message with additional information. Subsequent address message (with one or more address signals). Subsequent address message with one (address) signal.3.3.1 Initial address messageThe basic form
48、at of the initial address message is shown on Figure 3/Q.723.FIGURE 3/Q.723.CCITT-35530 = 3 CMThe following codes are used in the fields of the initial address message.a) Label: see 2b) Heading code H0 is coded 0001c) Heading code H1 is coded 0001d) Calling party categoryFascicle VI.8 Rec. Q.723 9bi
49、ts F E DC B A0 0 0 0 0 0 unknown source (Note 1)0 0 0 0 0 1 operator, language French0 0 0 0 1 0 operator, language English0 0 0 0 1 1 operator, language German0 0 0 1 0 0 operator, language Russian0 0 0 1 0 1 operator, language Spanish000110000111001000available to Administrations for selecting a particular language provided by mutualagreement0 0 1 0 0 1 reserved (see Recommendation Q.104 5) (Note 2)0 0 1 0 1 0 ordinary calling subscriber0 0 1 0 1 1 calling subscriber with priority0 0 1 1 0 0 data call0 0 1 1 0 1 t
