1、INTERNATIONAL TELECOMMUNICATION UNION)45G134 ) TELECOMMUNICATIONSTANDARDIZATION SECTOROF ITU).4%2!4%$G0G03%26)#%3G0G0$)4!,.%47/2+G0G0 )3$.G9)3$.G0G053%2G13.%47/2+G0G0).4%22) access of a multiple ISDN terminal installation;3) access of multiservice PBXs, or local area networks, or, more generally, of
2、 private networks;4) access of specialized storage and information processing centres.In addition, depending on the particular national regulatory arrangements, either ISDN user-network interfacesor internetwork interfaces may be used for access of:5) dedicated service networks;6) other multiple ser
3、vices networks, including ISDNs.3 Interface Recommendation objectivesUser-network interface Recommendations should allow:1) different types of terminals and applications to use the same interface;2) portability of terminals from one location to another (office, home, public access points) within one
4、country and from one country to another country;3) separate evolution of both terminal and network equipment, technologies and configurations;4) efficient connection with specialized storage and information processing centres and other networks.2 Fascicle III.8 - Rec. I.410User-network interfaces sh
5、ould be designed to provide an appropriate balance between service capabilities andcost/tariffs, in order to meet service demand easily.4 Interface characteristicsUser-network interfaces are specified by a comprehensive set of characteristics, including:1) physical and electromagnetic (including opt
6、ical) characteristics;2) channel structures and access capabilities;3) user-network protocols;4) maintenance and operation characteristics;5) performance characteristics;6) service characteristics.A layered approach has been adopted for the definition of ISDN user-network interfaces according to the
7、ISDN protocol reference model, Recommendation I.320.Fascicle III.8 - Rec. I.410 35 Interface capabilitiesIn addition to the multiservice capability, an ISDN user-network interface may allow for capabilities such asthe following:1) multidrop and other multiple terminal arrangements;2) choice of infor
8、mation bit rate, switching mode, coding method, etc., on a call-by-call or other (e.g. semi-permanent or subscription time option) basis, over the same interface according to the users need,3) capability for compatibility checking in order to check whether calling and called terminals cancommunicate
9、 with each other.6 Other I-Series Recommendations6.1 The reference configurations for ISDN user-network interfaces define the terminology for various referencepoints and the types of functions that can be provided between reference points. Recommendation I.411 contains thereference configurations an
10、d shows significant applications.6.2 The number of different interfaces is kept to a minimum. Recommendation I.412 defines a limited set ofinterface structures, and possible access capabilities for the ISDN user-network interfaces. A distinction is necessarybetween the interface structure and the access capability supported by the particular network access arrangement.6.3 The user-network interfaces, as defined in Recommendations I.420 and I.421, are applicable to a wide rangeof situations without modification (e.g. to both reference points S and T, as defined in Recommendation I.411).
