1、ITU-T RECMN*Q=7L 93 4862593 0589602 377 INTERNATIONAL TELECOMMUN CATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU Q.71 (03/93) GENERAL RECOMMENDATIONS ON TELEPHONE SWITCHING AND SIGNALLING FUNCTIONS AND INFORMATION FLOWS FOR SERVICES IN THEISDN , ISDN CIRCUIT MODE SWITCHED BEARER
2、SERVICES ITU-T Recommendation Q.71 (Previously “CCITT Recommendation”) FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The ITU-T is responsible for studying technical, operating and tariff questions and issuing Re
3、commendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Conference (WTSC), which meets every four years, established the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these t
4、opics. ITU-T Recommendation 4.71 was revised by the ITU-T Study Group XI (1988-1993) and was approved by the WTSC (Helsinki, March 1-12, 1993). NOTES 1 As a consequence of a reform process within the International Telecommunication Union (ITU), the CCITT ceased to exist as of 28 February 1993. In it
5、s place, the ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the IFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has been made in the tex
6、t to references containing the acronyms “CCITT, CCIR or IFRB or their associated entities such as Plenary Assembly, Secretariat, etc. Future editions of this Recommendation will contain the proper terminology related to the new ITU structure. 2 telecommunication administration and a recognized opera
7、ting agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O ITU 1994 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, witho
8、ut permission in writing from the ITU. CONTENTS Page 1 1 Introduction 1.1 General 1 1.2 Definitions 1 1.3 Symbols and abbreviations . 1 1 1.4 Services supported by this Recommendation . 1.5 Service invocation 3 2 Call set-up and release 2.1 Functional model 2.2 2.3 SDLs . 2.4 Interworking between pu
9、blic and private ISDNs . 2.5 Functional entity actions . 2.6 Additional FEAS required for digit-by-digit call setup cases . 2.7 Information flows required for en-bloc and digit-by-digit sending call set-up and call release . Allocation of functions to physical entities 3 3 5 19 58 59 64 67 Annex A -
10、 Interaction with Supplementary Services 69 Recommendation Q.71 (03/93) 1 ITU-T RECMNxQ.71 93 4862591 O589605 98b SUMMARY Recommendation Q.7 1 is the Stage 2 definition for point-to-point circuit mode switched bearer services. These cervices include speech, 3. i kHz audio, multi-use 7 kHz, unrestric
11、ted and n x 64 kbit/s information transfers as well as broadband connection-oriented bearer services. Stage 2 identifies the functional capabilities and information flows needed to support the service description. It provides information on the functions in ISDN entities and the information flows be
12、tween the entities which are required to provide call Set-up and call release procedures. This includes the description of the interfaces to the various I supplementary services and the interface to private networks. II Recommendation Q.71 (03/93) ITU-T RECMN*Q=7L 93 4862591 0589bOb 812 Recommendati
13、on Q.71 ISDN CIRCUIT MODE SWITCHED BEARER SERVICES (Melbourne 1988, modified at Helsinki 1993) 1 Introduction 1.1 General This Recommendation provides information on the functions in ISDN entities and the information tlows between the entities which are required to provide call Set-up and call relea
14、se procedures for point-to-point services. Such services include: - speech information transfer; - - - unrestricted information transfer; - n x 64 kbit/s information transfer; - broadband connection oriented bearer services. 3.1 kHz audio information transfer; multi-use 7 kHz information transfer; 1
15、.2 Definitions For the purposes of this Recommendation, the following definitions apply: call control functional entity (CC): CCs are functional entities which cooperate with each other to provide the services requested by the CCAs. call control agent functional entity (CCA): A functional entity tha
16、t serves the user and is responsible for initiating functional requests and interacting with CCs. through connect: information. To establish a connection within a functional entity making it available for transport of user private network (PN): private ISDN network consisting of ISDN PBX and/or ISDN
17、 Centrex. 1.3 Symbols and abbreviations For the purposes of this Recommendation, the following abbreviations apply: FEA Functional Entity Action , LE Local Exchange PNX private network exchange SDL Specification and Description Language Recommendation Z. i 00 1.4 Services supported by this Recommend
18、ation 1.4.1 64 kbifs information transfer An unrestricted bearer service (see Note i) provides information transfer without alteration between S/T reference points. It may, therefore, be used to support various user applications. Examples include: 1) Speech information transfer (see Note 2). This be
19、arer service category is intended to support speech. Recommendation Q.71 (03/93) 1 1TU-T REC“*Q-71 93 48b259L 0589607 759 The digital signal at the S/T reference point is assumed to conform to the internationally agreed encoding laws for speech (i.e. Recommendation G.711 A-law, p-law) and that the n
20、etwork may use processing techniques appropriate for speech such as analogue transmission, echo cancellation and low bit rate encoding. Hence, bit integrity is not assured. This bearer service is not intended to support modem derived voice-band data. All CCITT Recommendations for the transfer of spe
21、ech information in the network apply to this service. 2) 3.1 kHz audio information transfer (see Note 2). This bearer service corresponds to the service which is currently offered in the PSTN. This bearer service provides the transfer of speech and the transfer of 3.1 kHz bandwidth audio information
22、 such as voice-band data via modems, Groups I, II and III facsimile information (see Note 3). The digital signal at the S/T reference point is assumed to conform to the internationally agreed encoding laws for speech A-law and p-law, Le. Recommendation G.7 1 1. Connections provided for this service
23、should provide for the transfer of the information indicated above. (This means that the network may include speech processing techniques provided that they are appropriately modified, or functionally removed prior to non-speech information transfer.) The control of echo control devices, speech proc
24、essing devices etc., is only made by use of a 2100 Hz (disabling) in-band tone. 3) 7 kHz. 4) Multiple subrate information streams multiplexed into 64 kbit/s by the user. 5) Transparent access to an X.25 public network (Recommendation 1.462, case a). User information is transferred over a B-channel:
25、signalling is provided over a D-channel. NOTES 1 During an interim period some networks may only support restricted 64 kbit/s digital information transfer capability, i.e. information transfer capability solely restricted by the requirement that the all-zero octet is not allowed. For interworking th
26、e rules given in Appendix IlI.520 should apply. The interworking functions have to be provided in the network with restricted 64 kbit/s capability. The ISDN with 64 kbit/s transfer capabilities will not be affected by this interworking. other than conveying the appropriate signalling message to and
27、from the ISDN terminal. 2 it is recognized that it is the responsibility of the 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 th
28、e application in use. Furthermore, the Quality of Service attribute for information transfer delay will indicate the suitability of a particular version of this bearer service for speech. 3 The maximum modem bit rate that can be used by users in applications of this bearer service depends on the mod
29、ulation standard employed by the user and on the transmission performance within, or between, different Administrations. The extent of support is a network, or bilaterally agreed matter. 1.4.2 n x 64 kbis information transfer The information flows etc., contained in this Recommendation apply to unre
30、stricted information transfer at rates of n x 64 kbit/s where n is any positive integer. Time slot sequence integrity is maintained. 1.4.3 Broadband connection oriented bearer services This bearer service category provides unrestricted transfer of user information over a B-ISDN virtual connection be
31、tween the calling and called SB/TB reference points. The service allows for the establishment of multiple virtual connection each in a point-to-point configuration over the same physical interface. The service provides cell based communication in a bidirectional symmetric or bidirectional asymmetric
32、 fashion. The user specifies several parameters at call Set-up to characterize the communication. The symmetry and bit rate characterization will be provided. The bit rate may be characterized by a group of parameters such as peak bit rate, average bit rate, etc. 2 Recommendation Q.71 (03/93) ITU-T
33、RECNNxQ-71 93 = 4862571 0587608 b95 = 1.5 Service invocation Users indicate their required bearer service capabilities at the time of call set-up by including appropria? information in the service request sent to the network via the usednetwork signalling channel. Subsequent interactions involving s
34、tatus and control information also occur using the signalling channel. However, tones and announcements associated with speech and 3.1 kHz and multi-use 7 kHz information services are sent to the user over the user access channel used for the call. 2 Call set-up and release 2.1 Functional model See
35、Figure 2- 1 FIGURE 2- 1/Q.71 Functional model CCAs are functional entities that serve the users and are responsible for initiating functional requests and interacting with CCs. CCs are functional entities that cooperate with each other to provide the services requested by the CCAs. r1. r2 and r3 are
36、 relationships between functional entities wherein information flows occur in order to process call attempts or service requests. 2.1.1 Description of the call control agent (CCA) functional entity FE1 represents the originating CCA function which will a) access the service-providing capabilities of
37、 the CC entities, using service requests for the establishment, manipulation and release of a single call; receive indications relating to the call from the CC entity and relay them to the user; b) c) maintain call state information as perceived from this functional end-point of the service (Le. a s
38、ingle- ended view of the call). FE5 represents the terminating CCA function which will: a) access the service-providing capabilities of the CC entities using service requests for the establishment, manipulation and release of a single call; b) receive indications relating to the call from the CC ent
39、ity and relay them to the user; c) maintain call status information as perceived from this functional end-point of the service (i.e. a single- ended view of the call). In a single service example, one CCA originates the call and the other CCA terminates the call. The functions and relationships invo
40、lved are not symmetric. This asymmetry is retlected in the different FE designations, FEI and FE5, assigned to the two CCAs and in the different relationships designations between CCAs and CCs (rl and rj). Recommendation Q.71 (03/93) 3 ITU-T RECMN*:Q.71 93 m 4862591 0589609 521 m 2.1.2 Description o
41、f the call control (CC) functional entity Il 0 PN PN FE2 represents an originating CC function serving the calling partys CCA which will r3 0 FE5 T1139110-91/dZ a) b) establish, manipulation and release a single call (upon request of the CCA entity): associate and relate the CCA entities that are in
42、volved in a particular call and/or service; c) manage the relationship between the CCA entities involved in a call (i.e. reconcile and maintain the overall perspective of the call and/or service). FE3 represents a transit CC function. There can be more than one FE3 functional entity involved in a ca
43、ll depending on depth of network hierarchy. FE4 represents a terminating CC function serving the called partys CCA. 1-2 is a relationship between a CC-functional entity and another CC-functional entity. r2 can be of different types, depending on the functionality the related CC-functional entity rep
44、resents in a specific network scenario, e.g. a CC may be a gateway exchange or a PNX or a local exchange. r2* is the relationship between a private network and a public gateway CC at the originating side and r2* is the relationship between a private network and a public gateway CC at the terminating
45、 side (see Figure 2-2). FIGURE 2-2/Q.71 Logical relationships at public ISDN accesses Figure 2-2 illustrates that when an ISPBX is involved at the public ISDN access, the public ISDN provides gateway CCs which connect to the CCs of the PN via relationships r2* and r2*. Note that the public ISDN may
46、offer the basic service and the associated supplementary services at the customer network interface in two different versions as a subscription option. FE6 represents an originating gateway CC function designed to interface a private network to a public network. FE7 represents a terminating gateway
47、CC function designed to interface a private network to a public network. 2.1.3 Interfaces to Intelligent Networks The decision points are analogous to hooks for Supplementary Services. They use the capabilities of Intelligent Networks Capability Set 1. These decision points can be located on the Q.7
48、1 SDL diagrams. The inclusion of the IN decision points in this Recommendation remains to be done and will be included in the next update. 4 Recommendation Q.71 (03/93) ITU-T RECMN*Q-73 93 m 4862593 O589630 2q3 m 2.2 Information flows required for en-bloc and digit-by-digit sending call set-up and c
49、all release 2.2.1 Information flow diagrams Information flow diagrams for circuit mode switched bearer service call Set-up and call release are shown in Figures 2-3 through 2- 12: - Figure 2-3 shows a successful call Set-up using en-bloc sending; - Figures 2-4 through 2-6 show call set-up procedures for digit-by-digit sending cases; a) case I Address Information with Address End Signal; b) case 2 Address Information without explicit Address End Signal distinguished between Figure 2-S, fixed number length, known at FE2 and Figure 2-6, number length determined
