1、INTERNATIONAL TELECOMMUNICATION UNIONCCITT Q.955THE INTERNATIONALTELEGRAPH AND TELEPHONECONSULTATIVE COMMITTEESTAGE 3 DESCRIPTION FORSUPPLEMENTARY SERVICESUSING DSS 1STAGE 3 DESCRIPTION FORCOMMUNITY OF INTERESTSUPPLEMENTARYSERVICES USING DSS 1SECTION 1 CLOSED USER GROUPRecommendation Q.955Geneva, 19
2、92FOREWORDThe CCITT (the International Telegraph and Telephone Consultative Committee) is a permanent organ of theInternational Telecommunication Union (ITU). CCITT is responsible for studying technical, operating and tariffquestions and issuing Recommendations on them with a view to standardizing t
3、elecommunications on a worldwidebasis.The Plenary Assembly of CCITT which meets every four years, establishes the topics for study and approvesRecommendations prepared by its Study Groups. The approval of Recommendations by the members of CCITT betweenPlenary Assemblies is covered by the procedure l
4、aid down in CCITT Resolution No. 2 (Melbourne, 1988).Recommendation Q.955, 1 was prepared by Study Group XI and was approved under the Resolution No. 2procedure on the 4th of February 1992._CCITT NOTEIn this Recommendation, the expression “Administration” is used for conciseness to indicate both ate
5、lecommunication Administration and a recognized private operating agency. ITU 1992All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic ormechanical, including photocopying and microfilm, without permission in writing from the ITU.Reco
6、mmendation Q.955 1Recommendation Q.955Recommendation Q.955STAGE 3 DESCRIPTION FOR COMMUNITY OF INTERESTSUPPLEMENTARY SERVICES USING DSS 11 Closed User Group (CUG)1.1 DefinitionThe supplementary service Closed User Group (CUG) enables users to form groups, to and from which accessis restricted. A spe
7、cific user may be a member of one or more CUGs. Members of a specific CUG can communicateamong themselves but not, in general, with users outside the group. Specific CUG members can have additionalcapabilities that allow them to originate calls outside the group, and/or to receive calls from outside
8、 the group. SpecificCUG members can have additional restrictions that prevent them from originating calls to other members of the CUG, orfrom receiving calls from other members of the CUG.1.2 Description1.2.1 General descriptionEssentially normal call establishment procedures apply, but additionally
9、, to provide CUG service, the networkanalyses the call request from the calling user in conjunction with the CUG attributes associated with both the callingand called users (as identified by their ISDN numbers). As a result of this analysis the call either fails for CUG reasonsor is allowed to proce
10、ed.Note In the case where a user has subscribed to the DDI supplementary service, attributes are associated withthat part of the ISDN number which the network can recognize or with the default number valid for that access.The network provider may define the maximum number of CUGs of which a user can
11、 be a member.Since the fundamental purpose of the CUG service is to prevent certain connections, it is necessary to strictlycontrol interactions with some other supplementary services to protect CUG integrity.1.2.2 Specific terminology1.2.2.1 CUG managerThe CUG manager is the authority representing
12、the interests of all the members of a CUG. By planning andcontrolling the membership and members options, the manager can provide the overall CUG service expected by themembers as a whole.The CUG manager need not be a CUG member and the concept has no signalling implications.1.2.2.2 CUG indexThe CUG
13、 index is a parameter used by the calling user to select a particular CUG when originating a call. Theindex is also used by the network to indicate to the called user the CUG from which an incoming call has originated.This index has only local significance, i.e. the index used by the calling user wi
14、ll, in general, be different fromthe index used by the called user to identify the same CUG.1.2.2.3 CUG interlock codeThis is a means of identifying CUG membership within the network. At the calling side, if a CUG matchexists, the CUG index identifying a CUG maps to the CUG interlock code for that C
15、UG. If a CUG match exists at thecalled side, the CUG interlock code identifying a CUG maps to the CUG index representing that CUG.2 Recommendation Q.955CUG interlock code is not an access concept, but is used for clarity during the descriptions of signallingprocedures and flows.1.2.2.4 preferential
16、CUGA CUG user subscribing to preferential CUG nominates a CUG index which the network uses to identify therequired CUG in the absence of a CUG index being included in the outgoing call request.A preferential CUG applies to an ISDN number (or to an ISDN number/service see 1.3.1) and not to aspecific
17、CUG.1.2.2.5 CUG only serviceA user with CUG only services is limited to making calls to, and receiving calls from, members of those CUGsof which the user is a member.1.2.2.6 outgoing calls barred within the CUGThis restriction means that a CUG user cannot make CUG calls to members of those CUGs of w
18、hich the useris a member with the “outgoing calls” barring within the CUG option.1.2.2.7 outgoing accessOutgoing access allows a CUG user, in addition to the CUG only service (with or without outgoing callsbarred within the CUG), to make calls to all other non-CUG users and also to those other CUG u
19、sers that allowincoming access.An outgoing access arrangement applies to an ISDN number (or to an ISDN number/service see 1.3.1) andnot to a specific CUG.1.2.2.8 incoming calls barred within the CUGThis restriction means that a CUG user cannot receive CUG calls from members of those CUGs of which th
20、euser is a member with the “incoming calls” barring within the CUG option.1.2.2.9 Incoming accessIncoming access allows a CUG user, in addition to the CUG only service (with or without incoming callsbarred within the CUG), to receive calls from all other non-CUG users and also from those other CUG u
21、sers that allowoutgoing access.An incoming access arrangement applies to an ISDN number (or to an ISDN number/service see 1.3.1) andnot to a specific CUG.1.2.3 Qualification on the applicability to telecommunication servicesIn general CUG service is defined independently of any basic service, i.e. i
22、t applies to an ISDN number.However, the service may be defined in relation to one, or a list of basic services.1.2.4 State definitionsNo specifically defined states are required for the CUG service.1.3 Operational requirements1.3.1 Provision/withdrawalThe provision of the CUG service to a new membe
23、r and also assignment of the various CUG service options(except preferential CUG) individually, require a prior arrangement between the (new) member and the networkprovider with the consent of the CUG manager for the CUG.The assignment of a CUG index value to be associated with the CUG and also the
24、assignment of anypreferential CUG requires prior arrangement between the (new) member and the network provider only.The CUG service is provided on a subscription basis. As a network provider option, CUG service can beoffered with subscription options. The options can be divided into two groups:Recom
25、mendation Q.955 3a) The following options apply per ISDN number. The option values can be assigned individually for eachbasic service, or set of basic services, available at the ISDN number with CUG service:Option Values1) Preferential CUG Default CUG index, or non designated2) Outgoing access Allow
26、ed permanently, allowed per call, or not allowedNote The “allowed per call” outgoing access option is alternatively known as “outgoing access (explicit)”and the “allowed permanently” outgoing access option is alternatively known as “Outgoing access (implicit)”.Option Values3) Incoming access Allowed
27、, or not allowedIf for a user with CUG service, a basic service, or set of basic services, is not included in at least oneCUG, then: preferential CUG must have the “none designated” option value; outgoing access will normally have the “allowed permanently” option value if outgoing calls using abasic
28、 service or set of basic services are required; incoming access will have the “allowed” option value if incoming calls using a basic service or set ofbasic services are required.b) The following option applies per CUG. If the CUG includes more than one basic service, or set of basicservices, the val
29、ue of this option can be assigned individually for each basic service, or set of basic services,including:Option Values1) Barring within the CUG None, incoming calls, or outgoing callsIf for a particular basic service, or set of basic services, available to an ISDN number, a preferential CUGis nomin
30、ated, then it shall not be possible to assign the “outgoing calls” barring within the CUG option tothat basic service, or set of basic services, for the preferential CUG.The options assigned to a CUG member are stored in the network.Note Whether or not the storage of these options for CUG are centra
31、lized or decentralized is beyondthe scope of this Recommendation and is defined in the stage 2 of Recommendation of CUG (seeRecommendation Q.85.1).1.3.2 Requirements on the originating network sideFor correct interactions with other supplementary services, it is necessary for the originating network
32、 side tostore, for the duration of the call, details of whether a non-CUG, CUG (without outgoing access) or CUG (with outgoingaccess) call was requested in the information sent to the destination network side. The CUG identity (if any) requested ofthe destination network side must also be retained.1
33、.3.3 Requirements in the networkThis section is not applicable to DSS 1.4 Recommendation Q.9551.3.4 Requirements on the terminating network sideFor correct interactions with other supplementary services, it is necessary for the destination network side tostore, for the duration of the call, details
34、of whether a non-CUG or CUG (with or without outgoing access) call requestwas passed to the user. The CUG identity (if any) requested must also be retained.1.4 Coding requirements1.4.1 MessagesThe messages that will be used for the invocation and control of the CUG supplementary service follow:a) DI
35、SCONNECT (see Note 1);b) RELEASE (see Note 1);c) RELEASE COMPLETE (see Note 1);d) SETUP (see Note 2).Note 1 The facility information element may be included in the network-to-user direction in the first callclearing message if the calling user explicitly requests CUG service, if the network cannot a
36、llow the call to proceedbefore returning CUG service acceptance to the calling user. In the user-to-network direction the facility informationelement may be included in the first call clearing message if the called user cannot allow the call to proceed beforereturning CUG service acceptance to the n
37、etwork.Note 2 In the user-to-network direction the facility information element will be included if the calling userexplicitly requests CUG service. In the network-to-user direction facility information element will be included if a CUGcall is required.1.4.2 Operations (ASN.1)Closed-User-Group-Servi
38、ce-Operations ccitt recommendation q 955 cug (1)DEFINITIONS :=BEGINEXPORTS CUGCallOperationType ;IMPORTS OPERATION, ERRORMMMRemote-Operation-Notation joint-iso-ccitt remote-operations(4)notations(0)userNotSubscribed, basicServiceNotProvidedMMMFROM General-Error-Listccitt recommendation q 950 general
39、-error-list;CUGCallOperationTypeM:= - invoked from calling user to originating- network side and from destination network- side to user.OPERATIONARGUMENT SEQUENCEMoutgoingAccessRequest 1 IMPLICIT BOOLEAN DEFAULT FALSE,- if outgoing access is requested then TRUE is set, and- if outgoing access is not
40、 requested then FALSE is set.cUGIndex 2 IMPLICIT CUGindex OPTIONAL- in SETUP messageERRORSMuserNotSubscribed,basicServiceNotProvided,invalidOrUnregisteredCUGIndex,requestedBasicServiceViolatesCUGConstraints,outgoingCallsBarredWithinCUG,Recommendation Q.955 5incomingCallsBarredWithinCUG,userNotMember
41、OfCUG,inconsistencyInDesignatedFacilityAndSubscriberClass-Min first clearing message to calling user or networkCUGCallOperationMMMMMMMMCUGCallOperationTypeMM:=M2CUGIndexM:=MINTEGER (032767)-MSome networks may specify a max. value of the CUG index from 0 to 9999.invalidOrUnregisteredCUGIndex ERRORM:=
42、 16requestedBasicServiceViolatesCUGConstraints ERRORM:= 17outgoingCallsBarredWithinCUG ERRORM:= 18incomingCallsBarredWithinCUG ERRORM:= 19userNotMemberOfCUG ERRORM:= 20inconsistencyInDesignatedFacilityAndSubscriberClass ERRORM:= 21ENDM-Mof closed user group service operations1.5 Signalling requireme
43、nts1.5.1 Activation/deactivation/registrationNo signalling procedure is necessary for activation, deactivation and registration.1.5.2 Invocation and operationThe CUG service is invoked by: a call originating from a user that has CUG service. The user can explicitly request CUG service, but inthe abs
44、ence of an explicit request the CUG service default procedures are automatically applied; a call terminating at a user that has CUG service.1.5.2.1 Normal operation1.5.2.1.1 Actions at the originating local exchange1.5.2.1.1.1 Call originating from a user with CUG service1.5.2.1.1.1.1 Explicit reque
45、st of CUG serviceThe calling user can explicitly request the CUG service by including in the outgoing SETUP message a facilityinformation element containing a CUG call invoke component.To indicate outgoing access the user shall set the value of the Outgoing Access Request parameter to TRUE.The netwo
46、rk performs internal checks appropriate to the originating network side based on the contents of theinvoke component and the CUG attributes of the calling user. The outcome of these checks are defined inTable 1-1/Q.955 (including Notes).Note The network might respond to the SETUP message with a SETU
47、P ACKNOWLEDGE or CALLPROCEEDING message or the call might be cleared for some non-CUG service related reasons before the checks arecompleted.If the result of the checks relevant to the originating network side allow the call to proceed, then the networkperforms further internal checks based on the C
48、UG attributes (if any) of the called user. The outcome of these checks aredefined in Table 1-2/Q.955.If the call is successfully offered to the called user, an ALERTING or CONNECT message according to basiccall control, shall be returned to the calling user.6 Recommendation Q.9551.5.2.1.1.1.2 Implic
49、it request of CUG serviceThe calling user with CUG service can request the CUG service without including an invoke component in theoutgoing setup message (e.g. to make use of the preferential CUG facility). In this case the procedures of 1.5.2.1.1.1.1apply with the following exception: the network performs internal checks appropriate to the originating network side only based on the CUGattributes of the calling user.1.5.2.1.1.2 Call originating from a user without CUG serviceIt is possible for a user witho
