1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-1000603.2014 Integrated Services Digital Network (ISDN) Minimal Set of Bearer Services for the Primary Rate Interface As a leading technology and solutions development organization, ATIS brings together the top global ICT companies to advance t
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11、otice of Disclaimer for example, a voice- only terminal equipment (TE) could implement only the procedures for circuit-mode speech (bearer capability information element, and the like) and not implement those for circuit-mode digital. (4) Devices that support the bearer services de- fined in this st
12、andard by implementing associated procedures described in other American National Standards and using the default parameters and other specified mandatory parameters are expected to inter- operate successfully. (“Successfully“ means that they work together to obtain/provide the appropriate bearer se
13、rvice.) 1The designation numbers for the CCIIT Recommendations that appear in this standard refer to the 1993 CCITT Red Book. Contact the secretariat for more recent information. ATIS-1000603.2014 2 1.2 Relationship to Capabilities beyond the Minimal Set of Bearer Services. It is likely that ISDN im
14、plementations will provide capabilities beyond those defined in this standard. Some of these capabilities will eventually be standardized while others will be specific to an implementation. The following guidelines define the relationship of these additional capabilities to this standard. (1) The ne
15、twork, when viewed from the user-network interface, may also provide other additional services, capabilities, protocols, functions, and procedures not described in this standard or any American National Standard. These may or may not be evoked by a particular user at a particular user-public-network
16、 interface. (2) Customer premises equipment may implement additional services, capabilities, protocols, functions, and procedures not described in this standard or the American National Standard on signaling (ATIS-1000607). These may or may not be supported by a particular network at a particular us
17、er-network interface. (3) The implementation of the additional aspects mentioned in the previous two points does not, there- fore, make the user or network noncompliant with this standard or with ATIS-1000602 and ATIS-1000607(4) Some or all of the additional aspects mentioned in 1.2(1) and 1.2(2) ma
18、y be described in other standards; for example, standard signaling for a standard supplementary service. 2 Referenced however, for the support of the minimal set of bearer services, only the first three layers are required. Layers I through 3 provide the following functions: (1) Layer 1 (The Physica
19、l Layer). Layer 1provides the mechanical, electrical, functional, and procedural characteristics to activate, maintain, and deactivate a physical circuit. Layer 1 allows for the transparent transmission of bits to the connecting medium. (2) Layer 2 (The Data Link Layer). Layer 2 provides relatively
20、error-free transmission of data be- tween the ends of a physical link. Layer 2 defines the procedures required to establish, maintain, and disconnect the data link. (3) Layer 3 (The Network Layer). Layer 3 provides the means to establish, maintain, and release network connections between application
21、 entities. Layer 3 provides the procedures for the exchange of messages between the user and its serving network equipment over the D-channel. 3.6 Information Transfer Mode. This attribute describes the operational mode for transferring (transportation and switching) user information through the ISD
22、N. ATIS-1000603.2014 4 It can be used to characterize a telecommunication service or a connection in the network. Values associated with this attribute are circuit mode and packet mode. 3.7 Information Transfer Rate. This attribute describes either the bit rate (circuit mode) or the throughput (pack
23、et mode). It refers to the transfer of digital information between two access points or reference points. Values associated with this attribute are appropriate bit rate and throughput rate. 3.8 Information Transfer Capability. This attribute describes the capability associated with the transfer of d
24、ifferent types of information through the ISDN. It can be used to characterize a telecommunication service or connection. Values associated with this attribute are unrestricted digital, speech, 3.1-kHz audio, 7-kHz audio, 15-kHz audio, and video. 3.9 Communication Configuration. This attribute descr
25、ibes the special arrangement for transferring information between two or more access points. It completes the structure associated with a telecommunication service as it associates the relationship between the access points involved and the flow of information between these access points. Values ass
26、ociated with this attribute are point-to- point, multipoint, and broadcast. 3.10 Structure. This attribute refers to the capability of the ISDN to deliver the information to the destination access point or reference point in a structure (for example, time interval for the circuit mode, service data
27、unit for the packet mode) that was presented in a corresponding signal structured at the origin (access point or reference point). Values associated with this attribute are 8-kHz-integrity, service data unit integrity, and unstructured. 3.11 Establishment of Communication. This attribute associated
28、with a telecommunication service describes the mode of establishment used to establish and release a given communication. Values associated with this attribute are demand, reserved, and permanent. 3.12 Symmetry. This attribute describes the relationship of information flow between two (or more) acce
29、ss points or reference points involved in a communication. It characterizes the structure associated with a telecommunication service or a connection. Values associated with this attribute are unidirectional, bidirectional symmetric, and bidirectional asymmetric. 4 Background ITU-T Recommendation I.
30、211 defines bearer services in terms of three categories of attributes: in- formation transfer attributes, access attributes, and general attributes. Each attribute has a defined set of possible attribute values. The information transfer attributes define the transmission characteristics of connecti
31、ons between ISDN users at S/T reference points or between an ISDN user at an S/T reference point and an interworking point to another network. The information transfer attributes and values related to the minimal set of bearer services in this document are summarized in Table I. The access attribute
32、s describe the means for accessing network functions or facilities as seen at one S/T reference point. The access attributes and values related to the minimal set of bearer services in this document are summarized in Table 2. The general attributes deal with the service in general. The general attri
33、butes and values related to the minimal set of bearer services in this document are summarized in Table 3. ATIS-1000603.2014 5 5 Minimal Set of Bearer Services Appropriate to the United States The following bearer services should be provided by a public ISDN in the United States. In addition to the
34、attribute values, explanatory statements are given for fuller understanding of each bearer service. 5.1 Circuit-Mode Digital (CMD). Tables 4 through 6 summarize the information transfer attributes, ac-cess attributes, and general attributes associated with this bearer service. For this circuit-mode
35、digital bearer service with capability attribute value “unrestricted,“ the essential characteristic is that the received bit stream is identical (within performance limitations) to the transmitted stream including network-provided octet framing at the user-network interface. -Iaw to A-law conversion
36、 would not be provided at the internetwork points between -law and A-law countries. The actual application is controlled by user equipment at each end and could thus, in principle, transport voice, rate- adapted and non-rate-adapted circuit-mode data, packet-mode data, and the like. In the United St
37、ates, the need for a minimum “ones“ density to maintain repeater synchronization may prohibit the offering of this bearer service on other than an intra-switching- system basis by some networks for migration period. The introduction of new transmission techniques will remove this limitation. Request
38、s for this bearer service that result in interworking with other ISDNs, a CSPDN, a PSPDN, a CSPDN access line, or a PSPDN access line will be accepted. The interworking function includes signaling protocol interfacing. To interwork with digital networks having a maxi- mum of 56-kbit/s transport capa
39、bility, ISDNs may require selection of a 56-kbit/s rate adaptation by the user in the call request. During an interim period when domestic networks may have a restriction against transmission of the all- zero octet, the capability attribute value “restricted“ identifies that service constraint. Circ
40、uit-mode rate adaptation by user equipment from a lower rate (e.g., 4.8, 56 kbit/s) to 64 kbit/s is defined in ITU-T Recommendation I.460 and ensures that the all-zero octet is not transmitted by requiring at least one bit of each octet to be a binary one. To guard against inadvertent transmission o
41、f the all-zero octet by user equipment, the network may continuously monitor for this condition. When the all-zero octet is detected, it may be altered. Eventually, the universal availability of new transmission methods will eliminate this restriction and these restricted bearer capabilities could b
42、e eliminated. 5.2 Circuit-Mode Speech (CV). Tables 7 through 9 summarize the information transfer attributes, access attributes, and general attributes associated with this bearer service. For the speech-bearer service, the network assumes that -law-encoded speech, as described in ITU-T Recommendati
43、on G.711, is present at the user-network interface. The network provides octet- framing at the user-network interface. The essential characteristic here is that the ISDN may employ processing techniques appropriate for speech that do not assure bit integrity. -law to A-law conversion would be provid
44、ed, as appropriate, between net- works. Performance of voiceband modems is not guaranteed. When connections involving ISDN trunks are required, means for guarding against inadvertent transmission of the all-zero octet by user equipment may be provided by the network. Requests for this bearer service
45、 will be accepted both between ISDN users and for interworking with another ISDN, a PSTN, or a PSTN access line. The interworking function includes signaling protocol interfacing. ATIS-1000603.2014 6 5.3 Circuit-Mode Voiceband Data (CVBD). Information transfer attribute values are identical to circu
46、it-mode speech except that the capability attribute value is “3.1-kHz audio information.“ Access attribute values are identical to circuit- mode speech. General attribute values are identical to circuit-mode speech. For the 3.1-kHz audio bearer service, the network assumes that -law-encoded, band-li
47、mited, audio information is present at the user-network interface. The use of voiceband modems, including those specified in the V Series, and group I, II, and III facsimile is intended. The network provides octet framing at the user-network interface. In the ISDN, some transmission processes specif
48、ic to speech, may be prohibited; however, analog transmission may be permitted. -law to A-law conversion may be provided as appropriate between networks. Thus, bit integrity is not assured. When connections involving ISDN trunks are required, means for guarding against inadvertent transmission of th
49、e all-zero octet by user equipment may be provided by the network. Requests for this bearer service will be accepted both between ISDN users and for interworking with another ISDN, a PSTN, or a PSTN access line. The interworking function includes signaling protocol interfacing. Table 1 - Information Transfer Attributes and Values Table 2 - Access Attributes and Values ATIS-1000603.2014 7 Table 3 General Attributes Table 4 - Information Transfer Attributes Circuit Mode Digital Table 5 - Access Attributes- Circuit-Mode Digital ATIS-1000603.2014 8 Table 6 - General Attributes- Circ
