1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 ) TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%2!4%$G0G03%26)#%3G0G0$)4!,G0G0.%47/2+G0 )3$.G93%26)#%G0G0#!0!“),)4)%3G0 G0“%!2%2G0G03%26)#%33500/24%$G0G0“9G0G0!.G0G0)3$.#)2#5)4G13-/$%G0G0“%!2%2G0G03%26)#%#!4%/2)%3G0G0 G0G0#)2#5)4G13-/$%G0G0 G0KBIT S5.2
2、%342)#4%$ G0G0 G0K(ZG0G03425#452%$“%!2%2G0G03%26)#%)45G134G0G0RecommendationG0G0) (Extract from the “LUEG0“OOK)NOTES1 ITU-T Recommendation I.231.1 was published in Fascicle III.7 of the Blue Book. This file is an extract fromthe Blue Book. While the presentation and layout of the text might be sligh
3、tly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyright conditions remain unchanged (see below).2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a re
4、cognized operating agency. ITU 1988, 1993All 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.Fascicle III.7 - Rec. I.231.1 1Recommendation
5、 I.231.1Fascicle III.7 - Rec. I.231.1CIRCUIT-MODE BEARER SERVICE CATEGORIES CIRCUIT-MODE 64 kbit/s UNRESTRICTED,8 kHz STRUCTURED BEARER SERVICE(Melbourne, 1988)1 I.231.1 - Circuit-mode 64 kbit/s unrestricted, 8 kHz structured bearer service category (Note 1)1.1 DefinitionThis bearer service category
6、 provides unrestricted information transfer between S/T reference points, it may,therefore, be used to support various user applications. Examples include:- speech (Note 2);- 3.1 kHz audio (Note 2);- multiple subrate information streams multiplexed into 64 kbit/s by the user;- transparent access to
7、an X.25 public network Recommendation I.462 case a).User information is transferred over a B-channel, signalling is provided over a D-channel.Note 1 - During an interim period some networks may only support restricted 64 kbit/s digital informationtransfer capability, i.e. information transfer capabi
8、lity solely restricted by the requirement that the all-zero octet is notallowed. For interworking the rules given in Appendix I of Recommendation I.520 should apply. The interworkingfunctions have to be provided in the network with restricted 64 kbit/s capability. The ISDN with 64 kbit/s transfercap
9、abilities will not be affected by this interworking other than by conveying the appropriate signalling message to andfrom the ISDN terminal.Note 2 - Whilst speech and 3.1 kHz audio have been given as applications for this bearer service category, it isrecognized that it is the responsibility of the
10、customers to ensure that a compatible encoding scheme is in operation.Customers should also recognize that no network provision can be made for the control of such items as echo and loss,as the network is unaware of the application in use. Furthermore, the Quality of Service attribute value for info
11、rmationtransfer delay will indicate the suitability of a particular version of this bearer service for speech.1.2 Description1.2.1 General descriptionThis circuit-mode bearer service category allows:- two users (e.g. terminals, PABXs) in a point-to-point configuration to communicate via the ISDN usi
12、ng64 kbit/s digital signals over the B-channel, in both directions continuously and simultaneously for theduration of call;- three or more users in a multipoint configuration (refer to Recommendation I.254 for the supplementaryservice description on Three-Party Service and Conference Calling).1.2.2
13、Specific terminologyRetention timer: this timer specifies the amount of time that the network retains the call information of theoriginal call upon encountering busy or being released. It is a network provider option. The value for this timer isgreater than 15 seconds.1.3 Procedures1.3.1 Provision/w
14、ithdrawal1.3.1.1 Provision of this service will be by pre-arrangement with the Administration.2 Fascicle III.7 - Rec. I.231.11.3.1.2 This bearer service is offered with several subscription options which apply separately to each ISDN numberor group of ISDN numbers on the interface. For each subscrip
15、tion option, only one value can be selected. Subscriptionoptions for the interface are summarized below:Subscription option ValueMaximum number of informationchannels available at user BMaximum number of total callspresent at user B- m, where m is not greater than thenumber of information channels o
16、nthe interfacethe interface-n, where n is not greater than thenumber of information channels onthe interfacethe interfaceUser B can be an ISDN number or group of ISDN numbers on the interface.Note - More than one ISDN number can be associated with the service/interface only as a part of asupplementa
17、ry service such as multiple subscriber number. In the case of one ISDN number, the option given above forthe number of calls can only exceed the number of information channels in association with a supplementary service(e.g. call waiting). As a network provider option, separate values may be specifi
18、ed for incoming and for outgoing callsfor either or both of the limits.1.3.2 Normal proceduresAll user-network signalling is done on the D-channel.a) Originating the service (call set-up)The call is originated by the user requesting from the network the required bearer service; the requestincludes a
19、 number identifying the called user. Other information, as required, for the bearer service andfor use by the network in supplementary services provided to the called user (e.g. calling line identity)may also be included. This request may be given to the network either en bloc, containing all thereq
20、uired information, or not en bloc.b) Indications during call set-upAfter initiating a call the calling user will receive an acknowledgement that the network is able to processthe call. The called user will receive an indication of the arrival of an incoming call of this bearer service.The calling us
21、er shall also be given an indication that the incoming call is being offered to the calleduser, when an indication is received by the network that the called user is being informed of this call.When the call reaches the called user and the connection is established, an indication of this is sent to
22、thecalling user.The called user may also provide other information for use by the network in supplementary servicesprovided to other users (e.g. connected line identity). The relationship of a connected user with the calleduser requires further study.Once established, the B-channel is then available
23、 for the transmission of 64 kbit/s digital signals in bothdirections continuously and simultaneously, without alteration by the network. No restriction is placed bythe network on the content of the digital signals (see Note 1 of 1.1).c) Terminating the callThe call may be terminated by either or bot
24、h of the users by indicating this to the network. If one userterminates the call, an appropriate indication is sent to the other user.Fascicle III.7 - Rec. I.231.1 31.3.3 Exceptional proceduresa) Failure situations due to user errori) A user inputting a network-identifiable, improper service request
25、 will be given an appropriatefailure indication by the network and the call set-up will be ceased.ii) A user inputting a non-valid network number will be given an appropriate failure indication by thenetwork and the call set-up will be ceased.b) Failure situations due to called user statei) A callin
26、g user attempting to establish a call to a user who is identified by the network to be busy(either network-determined user busy or user-determined user busy) will be given an appropriatefailure indication by the network.ii) A user attempting to establish a call to a user whose terminal equipment fai
27、ls to respond will begiven an appropriate failure indication by the network and the call set-up will be ceased.iii) On a call to a user whose terminal equipment has responded that the called user is being informedof the call but has failed to answer within a defined period of time, the calling user
28、attempting toestablish the call will be given an appropriate failure indication by the network and the call set-upwill be ceased.c) Failure situations due to network conditionsA user attempting to establish a call but meeting call failure situations due to network conditions (e.g.congestion) will be
29、 given an appropriate failure indication by the network.d) Failure situations due to called user state and/or network conditionsA user attempting to establish a call but meeting call failure situations due to network conditions (e.g.congestion) or called user state (e.g. busy) can have service data
30、retained for a specified period of time,i.e. retention timer.1.3.4 Alternative procedures1.3.4.1 Reserved service proceduresFor further study.1.3.4.2 Permanent service proceduresFor further study.1.4 Network capabilities for chargingThis Recommendation does not cover charging principles. Future Reco
31、mmendations in the D-Series areexpected to contain that information.1.4.1 Demand service chargingIt shall be possible to charge the subscriber accurately for the demand service.1.4.2 Reserved service chargingIt shall be possible to charge the subscriber accurately for the reserved service.1.4.3 Perm
32、anent service chargingIt shall be possible to charge the subscriber accurately for the permanent service.4 Fascicle III.7 - Rec. I.231.11.5 Interworking requirementsInterworking between the ISDN and networks referred to as “digital PSTNs“, pre-ISDNs, pilot ISDNs orextended IDNs as well as between th
33、e ISDN and PSTNs may be required for this bearer service category.In advance of the provision of the ISDN, similar services supported by 64 kbit/s connectivity will be availableto customers by RPOAs/network operators on what may be described as “digital PSTNS“, pre ISDNs, pilot ISDNs orextended IDNs
34、. Interworking with ISDN customers will therefore be required. To effect this, as a broad guideline,RPOAs/network operators need to ensure these networks have the necessary functionality at the interworking point toprovide service connectivity with the ISDN.A V-Series terminal connected to the ISDN
35、via a terminal adaptor and using the 64 kbit/s unrestricted bearerservice requires the use of an IWF (including a modem) in the network for calls to PSTN users. To effect theconnection, a 64 kbit/s connection would need to be used to the IWF (interworking function) and a 3.1 kHz audio orequivalent c
36、onnection would then need to be used to the PSTN user.1.6 Interaction with supplementary servicesNot applicable. Each supplementary service description identifies the applicability to this bearer servicecategory.1.7 Attributes and values of attributes of the circuit-mode 64 kbit/s unrestricted, 8 kH
37、z structured bearer servicecategoryInformation transfer attributes1. Information transfer mode: circuit2. Information transfer rate: 64 kbit/s3. Information transfer capability: unrestricted4. Structure: 8 kHz integrity5. Establishment of communication: demand/reserved/permanent6. Symmetry: bidirect
38、ional symmetric/unidirectional7. Communication configuration: point-to-point/multipointAccess attributes8. Access channel: B for user information,D for signalling (Note)9. Access protocol: I-Series for D-channelGeneral attributes10. Supplementary services provided - Refer to Recommendation I.25011.
39、Quality of Service 12. Interworking possibilities for further study13. Operational and commercial aspects Note - For reserved/permanent service the operational administrative and maintenance (OAM) messagesrelated to these services may be conveyed over the D-channel.Fascicle III.7 - Rec. I.231.1 51.8
40、 Provision of individual circuit-mode 64 kbit/s unrestricted, 8 kHz structured bearer servicesa) Overall provision1): Eb) Variations of secondary attributes:Establishment Symmetry Communication Provision1)of communication configurationI.231.1/1 demand pt-pt EI.231.1/2 reserved bidirectional pt-pt AI
41、.231.1/3 permanent pt-pt EI.231.1/4 demand pt-pt AI.231.1/5 reserved unidirectional pt-pt AI.231.1/6 permanent pt-pt AI.231.1/7 demand multipt AI.231.1/8 reserved bidirectional multipt AI.231.1/9 permanent multipt AI.231.1/10 demand multipt AI.231.1/11 reserved unidirectional multipt AI.231.1/12 per
42、manent multipt Ac) AccessSignalling and OAM (Note 1) User information ProvisionChannel and rate Protocols Channel and rate ProtocolsD(16)D(64)I.451 (Note 2)I.451 (Note 2)B(64)B(64)User-definedUser-definedEENote 1 - Definition of protocols for OAM is for further study.Note 2 - Demand services only. F
43、urther study for reserved and permanent services.1.9 Dynamic descriptionThe dynamic description for this service on a demand basis is identical for a number of circuit-mode servicesand is therefore collectively given in Recommendation I.220._1)The definition of E (essential) and A (additional) can be found in Recommendation I.230.
