1、CCITT RECMNUI-3LO (REV*l) 93 lIb259L 0580555 305 m INTERNATIONAL TELECOMMUNICATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU INTEGRATED SERVICES DIGITAL NETWORK (ISDN) OVERALL NETWORK ASPECTS AND FUNCTIONS 1.31 O (03/93) ISDN - NETWORK FUNCTIONAL PRINCIPLES ITU-T Recommendation 1.
2、31 O (Previously “CCITT Recommendation”) CCITT RECflN*I*3LO (REV*L) 93 48b259L 0580.556 241 FOREWORD The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of the International Telecom- munication Union. The IT-T is responsible for studying technical, operating and tariff ques
3、tions and issuing Recommendations on them with a view to sandardizing 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 tum, produce Recommen
4、dations on these topics. IT-T Recommendation 1.310 was revised by the IT-T Study Group XVIII (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
5、February 1993. In its place, the IT 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 Similarly, in this reform process, the CCIR and the IFRB have been replaced by the adiocommunication Sector. In order not to delay publication of this Recommendation, no change has be
6、en made in the text 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
7、 a recognized operating agency. In this Recommendation, the expression ?Administration? is used for conciseness to indicate both a O ITU 1993 Ail lights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying a
8、nd microfilm, without permission in writing from the ITU. 1 CONTENTS General 1.1 Basic philosophy of the functional description . 1.2 Services supported by an ISDN . 1.3 Generic description of required capabilities . Objectives of the functional description of the ISDN 2 3 Generic description model
9、. 3.1 General concepts . 3.2 Static description model 3.3 Dynamic description model . Use of generic description model 4.1 Identification of ISDN global functions . 4.2 Identifi amended at Melbourne, 1988 and at Helsinki, 1993) 1 General 1.1 The objective of this Recommendation is to provide a commo
10、n understanding of the ISDN capabilities, including terminal, network and speciaiized service centre aspects. Basic philosophy of the functional description A functional description of ISDN capabilities must allow a clear distinction between definitiordspecification aspects of services provided by t
11、he ISDN and the actual specification of the equipment utilized to support those services. Therefore, an implementation-independent approach should be adopted. Moreover in the context of this Recommendation the adjective “functional” is used in the sense of an implementation- independent approach. Th
12、e noun “function” itself has a specific meaning which is explained below. The description of network capabilities is consistent with the protocol reference model, e.g.: - the layering structure of all systems involved in a communication process, i.e. partitioning the required functions between diffe
13、rent layers; the clear discrimination between layer service concept, layer function concept and layer protocol concept. - Furthermore, the three following distinctions apply: - - distinction between basic services and supplementary services; distinction between ISDN capabilities and services offered
14、 to the customer; - distinction between static and dynamic aspects of the description. NOTE - The inclusion in this Recommendation of aspects of intelligent network architecture, as described in Recommendations 1.31UQ.1201, 1.328/Q.1202, 1.329/Q.1203, and further Recommendations of the Q.1200-Series
15、 is subject to further study. 1.2 The concepts and the principles of an ISDN are describe in Recommendation 1,120. The services supported by an ISDN are given in the 1.200-Series Recommendations. A classification and the tools for the description of telecommunication services are specified in Recomm
16、endation 1.210 according to the description method as given in Recommendation 1.130. The network capabilities to support these services are defined in the 1.300-Series Recommendations. The relationship between these Recommendations and some other relevant I-Series Recommen- dations is shown in Figur
17、e 1. Services supported by an ISDN It should be noted that the service concept defined in Recommendation 1.210 is different from the layer service concept of the OS1 model. The telecommunication service concept in Recommendation 1.210 corresponds to the services offered to users by the network. Besi
18、des operational and commercial aspects, the provision of these telecommunication services (bearer and teleservices) and associated supplementary services requires the availability of appropriate capabilities: - - terminal capabilities; - network capabilities, in various network equipments (exchanges
19、 etc.); specialized service centre capabilities, when required. 1.3 ISDN capabilities are the total sum of the functions required to support all basic and supplementary services offered by the ISDN. Generic description of required capabilities Recommendation 1.310 (0303) 1 CCITT RECMN*I.3LO (REV*L)
20、93 E q862593 0580559 T50 E Network (l.70 b) the standardization of user-network interfaces, so as to enable terminal equipment to be portable and to assist in a); c) the standardization of ISDN capabilities to the degree necesary to allow user-network and network-network interworking, and thus achie
21、ve a) and b) above. 2 Recommendation 1.310 (03D3) CCITT RL determine the type of user-network access (basic, primary), the state of the resources (channels availability) and to reserve the channel(s) needed for establishing the access connection element. 103 Transit resources reservation Function of
22、 a functional entity to reserve the transit connection element, based on the state of resources. 1 O4 Communication references handling Function of a functional entity to assign a local reference (at the access interface) to the call and an internal reference (at the internal interface) to the conne
23、ction, and to clear these references when the call/connection is cleardreleased. 104 E 104 C Establish call reference (for furtber study) Clear call reference (for further study) 105 Establishment control Function of a functional entity to set up a connection through the functional entity. 105 R 105
24、 F 105 B Establish connection-return path only (for further study) Establish connection-forward path (for further study) Establish connection-both direction (for further study) 106 Release control Function of a functional entity to release a connection through the functional entity. 107 Service rela
25、ted authorization examination Function of a functional entity to determine the authorization (calling or called user) relating to basic and supplementary services that have been subscribed to. 1 O8 User-network signalling handling (layer 3) Function of a functional entity to support the layer 3 prot
26、ocol of the user-network signalling system. NOTE - For layers 1 and 2, see A.2.1.3, Resources handling. Inter-exchange signalling handling (user part) 109 Function of a functional entity to support the user part of the inter-exchange signalling system. 12 Recommendation 1.310 (03/93) CCITT RECMN*I-3
27、LO (REV*L) 93 Ip 4Bb259L 0580570 bLL 1 10 Supplementary services compatibility checking Function of the network to check the compatibility of requested supplementary services, e.g.: - - with requested bearer service to teleservice; with other requested supplementary services; and to verify coherence
28、 between parameters that may be associated. 11 1 Building-up of and maintaining dynamic information related to the callkonnection Function of a functional entity to compile information related to the calconnection, e.g.: - - resources needed (connection type, connection elements, channels, circuits)
29、; details of call in progress; - supplementary services effected and associated parameters. 112 Signalling interworking Function of a functional entity to support interworking functions between signalling systems. 113 Priority Function of a functional entity to handle specific calls with priority (e
30、.g. in the case of overload or degraded mode of operation). 114 Queue handling Function of a functional entity to store requests in a queue, in order to handle this information later in a predefined order. A.2.1.2 Routing 200 ISDN number idenfijkation Function of a functional entity to identify the
31、ISDN number of the user-network interface. This information is limited to that included within the ISDN numbering plan. 201 Called number analysis Function of a functional entity to analyse died ISDN number sent by the calling terminal in the call Set-up phase. 202 Routing information examination Fu
32、nction of a functional entity to analyse routing information that may be sent by the calling terminal and that has an effect on path selection. 203 Predetermined specific routing Function of an exchange to select a specific routing according to the information received from the calling terminal (for
33、 example routing towards operators, access points, an interworking unit, an operational or maintenance unit, etc.). 204 Connection path selection Function of a functional entity to select the transit outgoing part relating to connection types to be used, and the overail path through the network. 205
34、 Rerouting Function of a functional entity to select a new connection path through the network depending on changed conditions during call Set-up or information transfer phases. Recommendation 1.310 (03/93) 13 CCITT RECflN*I.3LO (REV*L) 93 .S 48b259L 0580573 558 M A.2.1.3 Resources handling 300 Func
35、tion of a functional entity to hold the access channel(s) reserved to support the communication, and to release it at the end of this communication. Hold and release of user-network access resources (channels) 300 H 300 R Hold and release of transit resources (circuits) Hold user-network access reso
36、urce (for further study) Release user-network access resource (for further study) 301 Function of a functional entity to hold the circuit(s) reserved to support the communication at the transit connection element and to release it at the end of this communication. 301 H 301 R Insertion and suppreswn
37、 of specijc equipment Hold transit resources (for further study) Release transit resources (for further study) 302 Function of a functional entity to insert or remove specific equipments particularly to satisfy the service request invoked by the user. Examples of such equipment include - echo suppre
38、ssers; - - interworking unit; - storageunit. Tones, announcements and display information A-p law conversion units (change of A/D conversion); 303 Function of a functional entity to provide call progress information in one or more of the following ways: - a tone is an audible (call progress) indicat
39、ion comprising one or more discrete frequencies but excluding speech; a recorded announcement is an audible indication in the form of speech or music; display information is (call progress) information set to the user which is displayed visually. - - Definitions of the other topics are not yet avail
40、able. 304 Functions of a functional entity to support layers 1 and 2 of the user-network signalling system. 305 Function of a functional entity to support the messages transfer part of the inter-exchange signalling systems. 306 Function of a functional entity to select an internal connection inside
41、the switching unit. 307 Synchronization handling Function of a functional entity to provide synchronization between different functional entities and function of a functional entity to provide its own internal synchronization functional entity. 308 Timing handling Function of a functional entity to
42、provide timing between time instances involved in calls. User-network signalling handling (layers 1 and 2) Inter-exchange signalling handling (message transfer) Path search inside switching unit 14 Recommendation I310 (03/93) CCITT RECMN*I=3LO (REV*L) 93 48b259L 0580572 494 M 309 Line service markin
43、g Functions of a functional entity to store for each customer the data on the parameters of the bearer and teleservices that are subscribed to. The store also contains the data on the parameters of the basic bearer and teleservices that are subscribed to by the customer. In addition, it contains the
44、 binary information (i.e. subscribed to or not) for a range of supplementary services which the subscriber can use. In general this data does not contain information on the type of Subscriber terminal, but it may contain information on the type of access (basic, primary rate, etc.), the type of NT2
45、(simple, intelligent, etc.) and the attributes of the services subscribed to. 310 Real time clock Function of a functional entity to provide real time information. A.2.1.4 Supervision 400 User-network access resources monitoring Function of a functional entity to check the correct operation of subsc
46、riber access resources. 401 Transit resources monitoring Function of a functional entity to check the correct operation of the transit resources. 402 Continuity checking Function of a functional entity to control the checking operations relating to the continuity of a connection. 403 Detection of co
47、ngestion Function of a functional entity to detect congestion during the selection of a connection path. 404 Semi-permanent connection checking Function of a functional entity to check the availability of a given semi-permanent connection (e.g. passive continuity checking). A.2.1.5 Operation and mai
48、ntenance 500 Management of subscriber data Function of a functional entity to manage subscriber data related to services. Examples include - dout of service; - number translation; 501 Fault report Function of a functional entity to register the cause if an attempt to set up a call fails. A.2.1.6 Cha
49、rging (the groupings below require further study) Function of the network to determine, collect and store the charging information. The following features are involved in this process. Recommendation 1.310 (03/93) 15 CCITT RECMN*I.3LO (REV*L) 93 48b259L 0580573 320 m 600 Charging management Function of a functional entity to determine by means of certain parameters the charging mode (Cee of charge, ordinary, peak, reduced rate charge, etc.). These parameters include service type, class of customer, time information, distance, etc. 600 I 600 C Initiate charging (for further study) C
