1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 ) TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%22!4%$G0G03%26)#%3G0G0$)4!,.%47/2+G0G0 )3$.G9/6%2!,G0G0.%47/2+G0G0!30%#43!.$G0G0 amended at Melbourne 1988)1 Introduction1.1 This Recommendation provides the general concepts, principles, and requirements
2、 for addressing referencepoints located at subscriber premises, for addressing other functions, and for allowing communications with terminals.1.2 Recommendation I.331 (E.164) describes the numbering plan for the ISDN era. Closely related information iscontained in Recommendation I.332 on numbering
3、principles for interworking between ISDNs and dedicated networkswith different numbering plans. Recommendation I.333 on terminal selection and Recommendation I.334 on principlesrelating ISDN numbers/subaddresses to the OSI reference model network layer addresses represent additional sources ofinform
4、ation having direct application to Recommendation I.330.1.3 The following understanding of relevant nomenclature is established:a) an ISDN number is one which relates to an ISDN network and ISDN numbering plan;b) an ISDN address comprises the ISDN number and the mandatory and/or optional additional
5、addressinginformation;c) private communications facilities are communication capabilities confined to use by one or more particularsubscribers, as opposed to facilities which are shared by subscribers of public networks. Examples ofprivate communications facilities include local area networks (LANs)
6、, PABXs, and other private networkarrangements.1.4 Depending on the different cases and stages identifiable within an addressing process, an ISDN number maybe (see Figure 10/I.330):a) an international ISDN number;b) a national ISDN number;c) an ISDN subscriber number.An ISDN address comprises:i) the
7、 ISDN number;ii) mandatory and/or optional additional addressing information.1.5 As an objective, all ISDNs should evolve towards a single numbering plan, namely the ISDN numbering plan.Considering the wide penetration of the telephone network in the world and existing telephone network resources, t
8、heISDN numbering plan has been developed by building from Recommendation E.163. Therefore, it is recommended thatthe telephone country code (TCC) be used to identify a particular country.1)1.6 An existing numbering plan may interwork and thus co-exist with the ISDN numbering plan. A framework forint
9、erworking between an ISDN and existing numbering plans is given in Recommendation I.332. RecommendationsE.166 and X.122 provide information describing selected interworking situations which have been considered byappropriate Study Groups. Preference should be given to single stage selection methods
10、whenever possible._1)Country or geographical area.2 Fascicle III.8 - Rec. I.3301.6.1 It is recognized that some of the present data networks, for instance, could retain the X.121 numberingstructure and interwork with ISDNs. A critical element of such interworking is numbering plan identification. Tw
11、oapproaches have been recommended:1) the escape code method, now recognized within the format structures of Recommendations E.164 andX.121;2) the NPI (Numbering Plan Identifier) method which applies distinct protocol provisions to distinguishnumbering plan identity from address content.Method 1) is
12、intended for near-term applications while method 2) may be applied to both near-term and long-term interworking, with a view to general use of method 2) after year-end 1996.1.6.2 It should be understood that call routing at each switching system is guided by reference to a destinationnumbering plan
13、which is identified by either method 1) or method 2), not both. Method 1) interprets numbers in terms ofthe numbering plan incorporated into the basic operation of the switching system, unless incoming circuit class logic oran escape code explicitly overrides that interpretation, substituting a diff
14、erent numbering plan. Under method 2) anexplicit numbering plan identifier is presented on each call.1.6.3 When transmission of the calling partys number is appropriate, the numbering plan of the calling party isestablished in a comparable manner. For a given direction of transmission, either method
15、 1) is used for both called andcalling numbers or method 2) is applied in both cases.1.6.4 After a switching system selects an outgoing route, the logical needs of the next switching system must beconsidered. Interworking between numbering plans may occur. The method used to inform the subsequent sw
16、itch aboutapplicable numbering plans may need to be adjusted, but numbering content should not be altered. Preference should begiven to method 2) when it is practicable to introduce it since method 1) places constraints on maximum number lengthin some circumstances.2 Principles for relating an ISDN
17、number to ISDN user-network reference configurations2.1 An ISDN number shall be able unambiguously to identify (a) particular:a) physical interface at reference point T (see Figure 1/I.330);b) virtual interface at reference point T; i.e., for an NT2 + NT1 configuration (see Figure 2/I.330);c) multip
18、le interfaces (physical or virtual) at reference point T (see Figure 3/I.330);d) for point-to-point configurations, physical interface at reference point S (see Figure 4/I.330);e) for point-to-point configurations, virtual interface at reference point S (see Figure 5/I.330);f) for point-to-point con
19、figurations, multiple interfaces (physical or virtual) at reference point S (seeFigure 6/I.330);g) for multi-point configurations (e.g. passive bus), all of the interfaces at reference point S (seeFigure 7/I.330).As a result, from the viewpoint of the network side of the interface, an ISDN number is
20、 associated with one (ora multiple of) D-channels used to signal to the user.2.2 A particular interface, or multiple of interfaces, may be assigned more than one ISDN number. An example isshown in Figure 8/I.330.2.3 All ISDNs shall be able to assign an ISDN number to an interface at reference point
21、T or S. However, aparticular ISDN number fulfills only one of the functions identified in 2.1.Fascicle III.8 - Rec. I.330 32.4 For mobile services an ISDN number shall be capable of unambiguously identifying an interface in the mobilesubscribers premises, as defined in 2.1 (see Figure 9/I.330).2.5 T
22、he ISDN number is not required to identify a particular connection where, on a particular interface, morethan one connection may be present at a given instant.2.6 The ISDN number is not required to identify directly a particular channel, where, within a particular interface,there may be more than on
23、e channel. Indirect identification of particular channels may occur: e.g. when the ISDNnumber identifies a particular interface and there is a one-to-one correspondence between that interface and particularchannels.3 Relationships between ISDN number, transit network/RPOA selection (when permitted),
24、 serviceindication, and quality of service indicationThe establishment of an ISDN connection will require an ISDN address. In addition separate non-addressrelated information may be necessary for completing a connection.3.1 Routing of ISDN connections shall take into account the following informatio
25、n, when supplied by the user:a) ISDN numbers, including destination network identification and digits for direct dialling-in (DDI) whereapplicable;b) service identification, possibly including requested quality of service parameters such as transit delay,throughput, and security;c) multiple transit
26、RPOA/network selection, when permitted by the originating ISDN.Note - The need for remote transit RPOA/network selection by the user of an ISDN which has no localtransit RPOA/network selection is for further study.In addition, transit RPOA/network selections by the originating ISDN, if provided, sha
27、ll also be evaluated in therouting of a connection.In national networks on a particular connection, the user may choose to specify some or all of this information,at either subscription time or connection-establishment time.The ISDN number does not identify the particular nature of the service, type
28、 of connection, or quality of serviceto be used, nor does it identify a transit RPOA/network.3.2 In the case where an ISDN number identifies a mobile TE or a TE served by several interfaces or networks, anISDN may need to map from the ISDN number on to a specific interface designation.4 Fascicle III
29、.8 - Rec. I.330 Fascicle III.8 - Rec. I.330 5 6 Fascicle III.8 - Rec. I.330 Fascicle III.8 - Rec. I.330 7 8 Fascicle III.8 - Rec. I.3304 ISDN number design considerations4.1 Numbering plan design information is covered by Recommendation I.331 (E.164).4.2 The ISDN number shall include an unambiguous
30、identification of a particular country2).The ISDN number is allowed to include an unambiguous identification of a particular geographic area within acountry 2).4.3 As an objective, all ISDNs should evolve towards a single numbering plan. However, an existing numberingplan may interwork and thus coex
31、ist with the ISDN numbering plan.4.4 When a number of public or private ISDNs exist in a country2), it shall not be mandatory to integrate thenumbering plans of the ISDNs. Methods for interworking are for further study, with the objective that connectionsbetween the TEs on these various networks can
32、 be completed by using only the ISDN address. See alsoRecommendation I.332.4.5 The ISDN number shall be capable of containing an identification of the ISDN to which the called user isattached. For a private network which spans more than one country2), the international ISDN number will causedelivery
33、 of a call to the particular private network in the country specified by the country code.4.6 The ISDN number shall be capable of providing for interworking of TEs on ISDNs with “TEs“ on othernetworks. As an objective, with respect to the ISDN number, the procedure for interworking should be the sam
34、e for allcases. The single-stage method of interworking is the preferred approach.5 Structure of the ISDN address5.1 The structure of the ISDN address is illustrated in Figure 10/I.330. A function marking the end of the ISDNnumber shall always be provided if a subaddress is present. The end of numbe
35、r function may also be provided even if nosubaddress is present. When there is no subaddress present, the end of number and end of address functions arecoincident, when used._2)Country or geographical area.Fascicle III.8 - Rec. I.330 95.2 The ISDN address may be of variable length.5.3 International
36、ISDN number5.3.1 The structure of the international number and the maximum number length are as defined inRecommendation I.331 (E.164).5.3.2 In a particular international ISDN number, the exact number of digits shall be governed by national andinternational requirements.5.3.3 The ISDN numbering plan
37、 shall provide substantial spare capacity to accommodate future requirements.5.3.4 The ISDN number shall be a sequence of decimal digits.5.3.5 The ISDN number shall include the capability for direct dialling inward where this facility is offered.5.4 ISDN subaddress5.4.1 The subaddress is a sequence
38、of digits, the maximum length of which shall be 20 octets (40 digits).5.4.2 All ISDNs shall be capable of conveying the ISDN subaddress transparently and shall not be required toexamine or operate on any of the subaddress information.5.4.3 Special attention is drawn to the fact that subaddressing is
39、 not to be considered as part of the numbering plan,but constitutes an intrinsic part of ISDN addressing capabilities. The subaddress shall be conveyed in a transparent wayas a separate entity from both ISDN number and user-to-user information. See also Recommendation I.334.6 Representation of ISDN
40、address6.1 At the person-machine interface, the objective is to establish one method of distinguishing betweenabbreviated and complete representations of an ISDN number. This method is for further study. Internationallyrecommended methods will be chosen.6.2 The method of distinguishing between an ISDN number and a number from another numbering plan shall beby separate identification of the applicable numbering plan. If such methods are required, internationally recommendedprocedures will be chosen.
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