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)%3#/-/.G0G0$9.!-)#G0G0$%3#2)04)/.G0G0/&G0G0“!3)#4%,%#/-5.)#!4)/.G0G03%26)#%3)45G134G0G0RecommendationG0G0) (Extract from the “LUEG0“OOK)N
2、OTES1 ITU-T Recommendation I.220 was published in Fascicle III.7 of the Blue Book. This file is an extract from theBlue Book. While the presentation and layout of the text might be slightly different from the Blue Book version, thecontents of the file are identical to the Blue Book version and copyr
3、ight conditions remain unchanged (see below).2 In this Recommendation, the expression “Administration” is used for conciseness to indicate both atelecommunication administration and a recognized operating agency. ITU 1988, 1993All rights reserved. No part of this publication may be reproduced or uti
4、lized 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.220 1Recommendation I.220Fascicle III.7 - Rec. I.220COMMON DYNAMIC DESCRIPTION OF BASICTELECOMMUNICATION SERVICES(Melbourne, 1988)1 Int
5、roductionThis Recommendation provides the dynamic description of basic telecommunication services. The dynamicdescription for basic telecommunication services using the circuit-mode means of service establishment/disestablishmentis provided in 2. The packet-mode description is for further study.The
6、dynamic description shows the flow of events, and states within the service, in a time-sequenced formatand identifies all possible actions relevant to the service as perceived by end-users.Although the service is described from the end-user perspective it does not concern details of the human-to-mac
7、hine interface itself. In addition, the service description considers the network as a single entity. For example,information flows between nodes within the network are not shown.End-user perceptions of the service are shown in terms of “user/network“ interactions. Internal network actionsare includ
8、ed whenever they are or can be perceived by an end-user during the operation of the service, and as requiredby SDL drawing rules.The terminology and the meaning of the “user/network“ interactions are provided in Annex A. The means fordeveloping dynamic descriptions, e.g. the SDL symbols and their us
9、age, is further elaborated in Recommendation I.210.Note - In the development of the circuit-mode dynamic description, the bearer services (speech, 3.1 kHz audio,unrestricted) and the teleservices (telephony, Teletex, Telefax 4, mixed-mode and Videotex) were considered. Others arefor further study.2
10、Circuit-mode dynamic description of basic bearer services and teleservicesSee Annex A for terminology used in Figures 1/I.220 to 6/I.220.In Figures 1/I.220 to 6/I.220, the following notes are common:Note 1 - This is an event which may occur at the S/T reference point and can be reflected at the user
11、 interface.Note 2 - This is an event which may occur at the S/T reference point but is not reflected at the user interface.Note 3 - In some networks this decision is optional, that is, multipoint operation is assumed.2 Fascicle III.7 - Rec. I.220 Fascicle III.7 - Rec. I.220 3 4 Fascicle III.7 - Rec.
12、 I.220 Fascicle III.7 - Rec. I.22056Fascicle III.7 - Rec. I.220Fascicle III.7 - Rec. I.220 7 8 Fascicle III.7 - Rec. I.220 Fascicle III.7 - Rec. I.220 9ANNEX A(to Recommendation I.220)Terminology for “user/network“ interactionsSETUP Interaction across the “user/network“ interface regarding a service
13、 request.REPORT Interaction across the “user/network“ interface regarding alerting of the users terminal function,interworking with a non-ISDN network, or routing progress.CONNECT Interaction across the “user/network“ interface regarding completion of circuit cut-through.DISCONNECT Interaction acros
14、s the “user/network“ interface regarding a user who has disconnected, or regarding auser A who cannot be connected (e.g. busy) to a user B.RELEASE Interaction across the “user/network“ interface regarding freeing of resources associated with thecall/connection, such as call references and channels.NDUB Network determined user busy.UDUB User determined user busy.
