WPCL 2BJ|x ` H   x|@  6'6' Recommendation I.230 Definition of bearer service categories 1.HGeneral HRecommendation I.210 describes the principles for defining telecommunication services supported by an ISDN, including the concept of bearer services, bearer capabilities and teleservices. It also provides the tools for the definition and description of such services.   HThe purpose of this Recommendation is to define a recommended set of bearer service categories that may be supported by an ISDN together with  their overall provision. These definitions form the basis for detailed descriptions of circuit mode bearer services as given in Recommendation I.231 and packetmode bearer services as given in Recommendation I.232 and their associated bearer capabilities, which are used to define the network capabilities required. HBearer services are fully described by prose definitions and descriptions, by attributes and by dynamic descriptions, which altogether define the service characteristics as they apply at a given reference point where the customer accesses the service. Recommendation I.140 and RecommendationI.210, Annex B describe the use of attributes for this purpose. 2.HDefinition of bearer services HThis section defines several bearer services accessed via the standard network access provided by an ISDN. The identification of possible additional services such as subrate services is left for further study. HThese possible additional services would not lead to any additional requirements to those already identified for physical characteristics of interfaces to be applied at reference points S and/or T (see RecommendationI.411). HThe definition of bearer services is based upon the list of attributes as given in Figure B2/I.210. The information transfer attributes numbers 14 are called "dominant attributes". They are used to identify a particular bearer service category. Information transfer attributes numbers 57 are called "secondary attributes". They are used to identify individual bearer services within one category. "Access attributes" as well as "general attributes" are used to further specify an individual bearer service. They are called "qualifying attributes". The principles of categorizing bearer services is presented in Figure 1/I.230. 2.1HCircuitmode bearer service categories HThese bearer service categories are typically characterized by the provision of user information over one type of channel and signalling over another type of channel. HThe use of the channel which conveys signalling information also to provide usertouser information transfer is described in the usertouser signalling supplementary service as given in Recommendation I.257. HThe following circuitmode bearer services categories have been identified so far: HI.231.164 kbit/s unrestricted, 8 kHz structured HI.231.264 kbit/s, 8 kHz structured, usable for speech information HHX X transfer  `    HI.231.3h64 kbit/s, 8 kHz structured, usable for 3.1 kHz audio information transfer   HI.231.4hAlternate speech / 64 kbit/s unrestricted, 8 kHz structured HI.231.5h2 x 64 kbit/s unrestricted, 8 kHz structured HH  ` HI.231.6h384 kbit/s unrestricted, 8 kHz structured HH HI.231.7h1536 kbit/s unrestricted, 8 kHz structured HH HI.231.8h1920 kbit/s unrestricted, 8 kHz structured HH  X HThe prose descriptions (step 1.1) and static descriptions (step 1.2) of these services are given in Recommendation I.231. A common dynamic description (step 1.3) for I.231.1, I.231.2, and I.231.3 is given in Recommendation I.220 for demand services only. 2.2HPacketmode bearer service categories HThese bearer services involve packet handling functions. HThe following packetmode bearer service categories have been identified so far and are described in Recommendation I.232: HHI.232.1hVirtual call and permanent virtual circuit HH  ` HI.232.2hConnectionless (Note 1) HH HI.232.3hUser signalling (Note 1)   Note 1 These services being identified need to be further studied and the descriptions are not yet included. 3HRecommended provision of bearer services HIn order to facilitate the development of compatible ISDNs and related user equipment, the tables in Recommendations I.231 and I.232 outline the recommended provision of bearer services defined in this Recommendation. The tables consist of three parts: Ha)h  description of the service category by the dominant attributes, i.e., information transfer mode, information transfer rate, type of information transfer capability and structure attributes. The recommended provision of services of this category is described as: H E an essential bearer service category to be made available internationally H A an additional bearer service category which may be available in some ISDNs and which may also be available internationally H FShthe recommended provision of this bearer service category is for further study. Hb)h  Within each bearer service category, a description of the agreed secondary attributes, i.e., establishment of communication, symmetry and information transfer configuration attributes. If an ISDN supports the bearer service category, the recommended provision of these secondary attribute combinations within this category are described as: ,ƌ H E an essential combination of attributes to be made available internationally (when an ISDN supports the particular overall bearer service category). H A an additional combination of attributes which may be available in some ISDNs and which may also be available internationally (when an ISDN supports the particular overall bearer service category). H FShthe recommended provision of this combination of attributes is for further study. Hc)h  Within each bearer service category a description of the agreed qualifying attributes, e.g. channel/rate and protocol access attributes for user information and for signalling OAM information. If an ISDN supports the bearer service category the recommended provision of these qualifying attributes within this category are described as: H E an essential access arrangement to be made available (when an ISDN supports the particular overall bearer service category) H A an additional access arrangement which may be available in some ISDNs (when an ISDN supports the particular overall bearer service category) H FShthe recommended provision of this access arrangement is for further study. Note 1 During an evolutionary period, not all items marked "E" will be provided in all networks. Note 2 Attributes 1013 are for further study. HRecommendations I.231 and I.232 give the recommended provision of bearer service categories and bearer services. The recommended overall provision of bearer service categories is reproduced in Table 1/I.230. GTABLE 1/I.230 M 0Recommended overall provision of bearer service categoriesă HCircuitmode bearer service categories H1)  64 kbit/s unrestricted E H2)  Speech E H3)  3.1 kHz audio E H4)  Alternate speech / 64 kbit/s unrestricted A H5)  2 x 64 kbit/s unrestricted A H6)  384 kbit/s unrestricted A H7)  1536 kbit/s unrestricted A H8)  1920 kbit/s unrestricted A HPacketmode bearer service categories H1)  Virtual Call and Permanent Virtual Circuit E H2)  Connectionless FS H3)  User Signalling FS 4.HProse definitions of bearer service categories HIn order to give an overview of the bearer service categories identified, their definitions as given in Recommendations I.231 and I.232 are reproduced in this section. 4.1HCircuite mode bearer service categories I.231.1 Circuitmode 64 kbit/s unrestricted 8 kHz structured bearer Hservice category)  X HThis bearer service category provides unrestricted information transfer between S/T reference points. It may, therefore, be used to support various user applications. Examples include: H1)h  Speech; H2)h  3.1 kHz audio; H3)h  multiple subrate information streams multiplexed into 64 kbit/s by the user; H4)h  transparent access to an X.25 public network (I.462 case a). HUser information is transferred over a B channel, signalling is provided over a D channel.  I.231.2 Circuitmode 64 kbit/s, 8 kHz structured bearer service category usable HHfor speech information transfer  `   p HThis bearer service category is intended to support speech.   HThe digital signal at the S/T reference point shall conform to Recommendation G.711 (Alaw or law). The network may use processing techniques appropriate for speech such as analogue transmission, echo cancellation and low bit rate voice encoding. Hence, bit integrity is not assured. This bearer service category is not intended to support modem derived voice band data.  X HAll CCITT Recommendations for the transfer of speech information in the network apply to this bearer service category. I.231.3 Circuitmode 64 kbit/s 8 kHz structured bearer service category Husable for 3.1 kHz audio information transfer HThis bearer service category corresponds to the service which is currently offered in the PSTN. This bearer service category provides for the transfer of speech and of 3.1 kHz bandwidth audio information such as voice band data via modems and facsimile group 1, 2 and 3 information. The digital signal at the S/T reference point shall conform to Recommendation G.711 (Alaw or  law). HConnections provided for these services should offer the transfer , capability for the information indicated above. (This means that the network may include speech processing techniques provided they are appropriately modified or functionally removed prior to nonspeech information transfer). The control of echo control devices, speech processing devices etc., is only made by use of disabling tones (see Recommendation V.25). Bit integrity is not assured. The network may use analogue transmission. HAll CCITT Recommendations for the transfer of speech information in the network apply to this bearer service category. I.231.4 Circuitmode alternate speech / 64 kbit/s unrestricted H8 kHz structured bearer service category HThis bearer service category provides the alternate transfer of either speech or 64kbit/s unrestricted digital information with the same call. HThe request for this alternate capability and the initial mode desired by the user must be identified at call setup time. HThis service is provided for the support of multiple capability terminals or single capability terminals. HFor the speech mode of this bearer service the same applies as for the speech bearer service category. For the unrestricted mode of this bearer service category the same applies as for the unrestricted bearer service category. I.231.5 Circuitmode 2 x 64 kbit/s unrestricted H8 kHz structured bearer service category HThis bearer service category provides the unrestricted transfer of two 64 kbit/s user information flows over two B channels at the user network interface. I.231.6 Circuitmode 384 kbit/s unrestricted H8 kHz structured bearer service category HThis bearer service category provides the unrestricted transfer of 384 kbit/s user information over a Ho channel at the S/T reference point. The transfer of OAM information for reserved and permanent services may be provided over a D channel in the same or in another interface structure. I.231.7 Circuitmode 1536 kbit/s unrestricted H8 kHz structured bearer service category HThis bearer service category provides the unrestricted transfer of 1536kbit/s user information over a H11 channel at the S/T reference point. Transfer of OAM information for reserved and permanent services may be provided via a D channel in another interface structure. I.231.8 Circuitmode 1920 kbit/s unrestricted H8 kHz structured bearer service category HThis bearer service category provides the unrestricted transfer of 1920kbit/s user information over a H12 channel at the S/T reference point. The transfer of OAM information for reserved and permanent services may be provided over a D channel. 4.2HPacket mode bearer service categories I.232.1 Virtual call and permanent virtual circuit bearer service category HThis bearer service category provides the unrestricted transfer of user information in a packetized manner over a virtual circuit within a B or D channel at the S/T reference point. Signalling information for virtual call and/or possibly OAM information for permanent virtual circuit services are transferred via a D or B channel as described in Recommendation I.462 (X.31). I.232.2 Connectionless packetbearer service category HThe definition of services in this bearer service category is for further study. I.232.3 User signalling bearer service category