1、ITU-T RECMN*I*333 (REV*L) 93 4862593 0582654 334 = INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOMMUNICATION STAN DARD I Z AT I ON SECTOR OF ITU INTEGRATED SERVICES DIGITAL NETWORK (ISDN) OVERALL NETWORK ASPECTS AND FUNCTIONS 1.333 (03/93) TERMINAL SELECTION IN ISDN ITU-T Recommendation 1.333 (P
2、reviously “CCIlT Recommendation”) ITU-T RECMN*I-333 (REV831 93 i.1862593 0582655 070 I 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 question
3、s and issuing Recommendations 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 Recommenda
4、tions on these topics. ITU-T Recommendation 1.333 was revised by the ITU-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 ITU Telecommunication Standardization Sector (ITU-T) was created as of 1 March 1993. Similarly, in this reform process, the CCIR and the LFRB have been replaced by the Radiocommunication Sector. In order not to delay publication of this Recommendation, no change has
6、been 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 a
7、nd a recognized operating agency. In this Recommendation, the expression “Administration” is used for conciseness to indicate both a O ITU 1993 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
8、 and microfilm, without permission in writing from the ITU. CONTENTS Introduction scope General principles 3.1 Terminal selection requirements . 3.2 General operations 3.3 Terminal selection responsibilities . Terminal selection functions 4.1 Information elements for the support of terminal selectio
9、n functions 4.2 Procedures for the support of terminal selection functions 4.3 Procedures between terminating local exchange and called terminals . Terminal selection procedures . 5.1 Calls within ISDNS) 5.9- Terminal selection for interworking . 5.3 Terminal functionality for general purpose termin
10、als . 5.4 Terminal functionality for compatibility with the “sub-addressing” supplementary service . Appendix I . Examples of terminal selection in illustrative configurations Limited functionality speech terminal 1.1 1.2 Multiple different terminals on u. passive bus . Page 1 1 2 2 3 7 7 8 8 9 10 1
11、0 19 23 25 25 25 26 TERMINAL SELECTION IN ISDN (Melboiime, 1988; revised Helsinki, 1993) 1 Introduction This Recommendation defines “terminal selection” as the procedures carried out between a terminating ISDN exchange and ISDK terminals situated behind an ISDN interface leading to customer premises
12、 whereby terminal response equivalent to answer or rejection is solicited. The procedures apply to both point-to-point and point-to-multipoint terminal operations. The primary objective of this Recommendation is to provide overall principles on terminal selection in ISDN. This Recommendation therefo
13、re provides a framework within which network providers or users may choose appropriate terminal selection procedures, to suit their own operating environment and applications. Appendix I contains illustrations of terminal selection techniques that are useful in appropriate circumstances. Note that i
14、n the case of an existing terminal TE2) connected via a terminal adaptor TA) to an ISDN access, the combination of TA and TE2 provides the same functionality as a TE1. As there should be no modifications to the existing terminal, the functions described are provided by the terminal adaptor. NOTE - I
15、n the context of this Recommendation “terminal” is a generic term and does not constrain the implementation of physical terminds which may consist of one or more logical terminals. 2 Scope 2.1 It is recognized that call setup is an end-to-end process requiring appropriate switching, signalling and t
16、erminal functionality at both ends. However, the frame of reference used in this Recommendation is mainly the terminating ISDN exchange and the terminal configuration(s) served by that exchange. The originating exchange and the terminal configuration(s) served by that exchange are covered only if a
17、specific request for a terminal function at the calling side, supporting the terminal selection procedure at the called side, is identified. 2.2 It is also recognized that calls originating from existing non-ISDN networks (e.g. PSTN or PSPDN) with limited addressing and signalling capabilities will
18、not be able to use the full range of terminal selection functions. This Recornmendation therefore addresses the terminal selection for the following types of calls: - culls within the ISDN: i) based on non-initialization procedures and end-to-end capability. In this case, the network provides basic
19、capabilities and has no knowledge of service profiles of terminals and related terminal identities (an illustrative example is provided in I. 1. i); ii) based on terminal initialization procedures. In this case, the terminating exchange provides additional capabilities and the network has knowledge
20、of service profiles of terminals and related terminal identities and hence can assist in terminal selection see 4.3); - calls from public non-ISDN networks (e.g. PSTN or PSPDN) to ISDN. NOTE - Calls from private networks to ISDN are not currently addressed in this Recommendation. 2.3 selection takes
21、 place among the terminals belonging to one access. This Recommendation addresses terminal selection in ISDN for both basic and primary rate access, whereby Recommendation 1.333 (03/93) 1 ITU-T RECMN*I.333 (REV*FL) 93 PB 4862593 0582658 88T II 2.4 purposes may be a requirement, this Recommendation d
22、oes not currently address this application. Though selection of a specific terminal in a multipoint configuration in ISDN for maintenance and operation 2.5 This Recommendation is related to andlor is compatible with the following Recommendations: - Recommendations of the 1.200-Series on ISDN service
23、s; - - Recommendation 1.330: ISDN numbering and addressing principles; Recommendation 1.331 (E.164): Numbering plan for the ISDN era; - Recommendations 1.410,1.411,1.412: ISDN user - network interfaces; - - Recommendation 1.441 (4.921): ISDN user - network interfaces layer 2 specifications; Recommen
24、dation 1.45 1 (4.93 1): ISDN user - network interfaces layer 3 specifications; - Recommendations of the 1.500-Series defining interworking between various networks; Recommendation 4.932, Annex A: Generic procedures for the control of ISDN; supplementary services - User service profiles and terminal
25、identification. Recommendation T.90: Characteristics and protocols for terminals for telematic services in ISDN. - - 3 General principles 3.1 Terminal selection requirements An ISDN number identifies any one interface (physical or virtual) or multiple interfaces or all of the interfaces at reference
26、 point S (2.1/I.330), but does not provide the capability to identify services, which - in the ISDN user context - are assigned to individual terminals. Requirements are imposed on terminal selection by the potential multiple terminal arrangements at called subscribers premises and the ISDN support
27、of multiple services, which implies the provision of information for unambiguously identifying the individual service. Information in addition to the ISDN number (unique number assigned to an access) are needed since the ISDN number is insufficient to make needed distinctions among terminals. This R
28、ecommendation addresses the general principles to be applied in selecting 1) specific individual terminals or 2) groups of terminals among which, for the purpose of terminal selection, no further distinction is required by the terminating users terminal configuration. These terminals may slightly di
29、ffer in their functionality but still be compatible and it is the users decision which terminal is member of a particular group. here may exist multiple physical terminals on a point-to-multipoint configuration (e.g. passive bus), whose interfaces are identified by an ISDN number, or the relevant pa
30、rt of it. Within each physical terminal there may exist one or more logical terminals (as shown in Figure 1). A logical terminal is considered to be the exchanges view of the physical terminal(s) on an interface. Eight logical terminals (the inner boxes; labelled LT1 to LT8) are shown in a total of
31、four physical terminals (the outer boxes; labelled PT1 to PT4). Each physical terminal corresponds to at least one individual TE1 (see Note), while each logical terminal corresponds to one individual TEI. The arrangement shown in Figure 1 reflects a customer subscribing to the “multiple subscriber n
32、umber” (MSN) supplementary service, otherwise SN values are equal and thus not relevant to the capability to discriminate between terminals. dation Q.92M.441). NOTE-The terminal endpoint identifier (TEI) is part of the D-channel layer 2 address field (see Recommen- 2 Recommendation 1.333 (03/93) _ I
33、TU-T RECMN*I.333 (REV*L) 93 W Yb259L 0582659 7Lb W I The characteristics of out-band compatibility checking and its relationship to in-band compatibility checking are as follows: PT4 Interfaces at reference points S and T coincident PT3 o SN=a PTl PT2 PT Physical terminai LT Logical terminai SN=a NT
34、 Network termination Subscriber number with value “a NOTE - The values “li”, “d ” and y” are used as group numbers for logical terminals. The numbers do not need to be contiguous numbers. FIGURE 1h.333 Illustration of logical terminal arrangements 3.2 General operations Terminal selection relies hea
35、vily on the call setup protocols according to Recommendation Q.93UI.451 and makes use of complementary elements involved in the call setup process, some of them referring to terminal identity while some others referring to compatibility. The elements referring to terminal identity include any type o
36、f number such as ISDN number and sub-address while the elements referring to compatibility include any type of compatibility information such a5 bearer capability, low layer compatibility and high layer compatibility. Terminal selection is therefore a combination of terminal identitication (based on
37、 a number without any relationship to compatibility) and compatibility checking, whereby these two mechanisms are used in a complementary manner. Since the call setup procedures are making use of out-band signalling, the compatibility check applicable to terminal selection is out-band compatibility
38、checking. ITU-T RECMN*I*333 (REV*L) 93 H 48b2591 0582bb0 438 W 3.2.2 Out-band compatibility checking is related to terminal selection. Out-band compatibility checking may continue after terminal selection to achieve compatibility at the communication level (e.g. user-to-user protocols and their para
39、meters). 3.2.3 In-band compatibility checking starts when a terminal was selected (as seen by the network). It can include notification of compatibility information or negotiation of terminal characteristics. The actions to be taken if in-band compatibility checking fails require further study, howe
40、ver, it might be difficult to accommodate the callingkalled users terminal profile pending elements to identify, or being unable to match characteristics of the other party. 3.2.4 From the networks point of view in-band compatibility checking is not related to terminal selection, while from the user
41、s point of view it may be related to terminal selection e.g. if an intelligent unit at called subscriber premises selects a terminal based on information made available by in-band procedures. 3.2.5 With respect to the networks responsibility for conveyance of compatibility information and delivery t
42、o the called users terminal configuration according to the directory number defined by the calling user, there is in principle no difference between out-band and in-band information transfer. Two distinct compatibilities are defined: 3.2.6 Compatibility between the calling and called terminal coveri
43、ng characteristics such as compatibility of bearer services, teleservices, end-to-end protocol, and parameters which affect transmission quality. This compatibility is dependent upon the particular application e.g. bearer service, teleservice, etc. 3.2.7 Mutual compatibility between terminals served
44、 on the same access. This compatibility is required in a terminal population in order to prevent some terminals from accepting calls which are inappropriate to them. This compatibility is dependent upon the particular access and associated terminals, as well as service issues. This compatibility ens
45、ures that incoming calls properly originated are accepted only by the appropriate tenninal(s). Figure 2 illustrates these two compatibilities. The mutual compatibility between terminals at the same access makes provision that the lower terminal, which is incompatible to the calling terminal, does no
46、t ask the network to connect the call when the SETUP message is received. Figure 3 illustrates the impact of mutual compatibility between terminals at the same access on “ensured” or “not ensured” compatibility. Note that the indication in the Figure 3 “compatibility not ensured” is intended to mean
47、 that compatibility is not ensured though it may exist. Figure 3 depicts three cases which may exist at called subscriber premises: a) All terminals support full ISDN terminal selection functionality (upper case in Figure 3); b) Some terminals support full ISDN terminal selection functionality while
48、 some others support limited ISDN terminal selection functionality (middle case in Figure 3); c) All terminals support limited ISDN terminal selection functionality (lower case in Figure 3). In order to ensure compatibility according to Figure 3, two conditions have to be satisfied concurrently: 1)
49、the information available for out-band compatibility checking has to ensure compatibility, and 2) the terminals at called subscriber premises have to be mutually compatible. 4 Recommendation 1.333 (03193) Called terminals Calling terminal to called terminai compatibility Calling terminal u , TE receiving SETUP Compatible tminals transmitting message receiving Incompatible terminals SETUP message Ti 81 5530-9ZdO2 FIGURE 2ti.333 Calling to called terminai compatibility and mutual compatibility between terminals at the same access In situations where the terminals at calle
