Recommendation I.232 - Packet mode bearer services categories Recommendation I.210 describes the principles for defining telecommunication services supported by an ISDN includ- ing the concept of bearer services, teleservices and supplementary services. It also provides the means for the definition and description of such services. The purpose of this Recommendation is to define a recommended set of packet mode bearer services categories, to describe individual packet mode bearer services and to recommend their provision in ISDN. The definitions and descrip- tions form the basis to define the network capabilities required for the support of the services in ISDN. Bearer service categories are described by prose definitions and descriptions, by attributes and their values and by dynamic descriptions following the description method given in RecommendationI.130. The application of the attribute technique and the definitions of these attributes and attribute values is given in Recommendation I.140. The following set of bearer services categories is currently identified and more may be identified in the future: - virtual call and permanent virtual circuit bearer service category; - connectionless bearer service category; - user signalling bearer service category. I.232.1 - Virtual call and permanent virtual circuit bearer service category 1. Definition This bearer service category provides the unrestricted transfer (without alteration) of user information in a pack- etized 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 B or D channel as described in Recommendation I.462 (X.31). 2. Description 2.1 General description This packet mode bearer service category allows users (e.g., terminals) in a point-to-point communication configu- ration to communicate via the ISDN using X.25 encoding, by means of Recommendation I.462 (X.31) procedures over either B or D channels, in both directions continuously and simultaneously for the duration of a call. 2.2 Specific terminology Not applicable. 2.3 Qualifications Not applicable. 3. Procedures Detailed procedures for virtual calls appear in RecommendationI.462(X.31) case B. This descrip- tion is a synopsis of those procedures. For actual, complete procedures, refer to RecommendationI.462. 3.1 Provision/withdrawal For further study. 3.2 Normal procedures 3.2.1 Activation/Deactivation/Registration Not applicable. 3.2.2 Invocation and operation 3.2.2.1Virtual call procedures a) Call establishment For virtual calls, X.25 will be used on an active channel (BorD) to the packet handler. In order to establish that channel and/or to negotiate the type of channel to be used, out- of-band signalling procedures may be used. Once connected to the packet handler, remaining call information, including called user address, are signalled in the X.25 call request. b) Data transfer phase Once established, the virtual circuit is then available for unrestricted X.25 data transfer in both directions contin- uously and simultaneously. During the data transfer phase, information exchange occurs with the following char- acteristics, among others: - packetized; - flow control; - delivery confirmation (optional); - reset/interrupt. c) Terminating the call The call may be terminated by either of both of the users by indicating this to the network. In either case, an appropriate indication is sent to the other user. The active channel may be released after the termination of the last virtual call on that channel. 3.2.2.2Permanent virtual circuit procedures For permanent virtual circuits on B or D channels there is no call set up or clearing. For permanent virtual circuits using B channel access, a semi- permanent connection of the channel to the packet handler must be in place. The pro- cedures for the control of packets between user terminal equipment and network are covered by X.25 data transfer phase. 3.2.3 Interrogation/Editing Not applicable. 3.3 Exceptional procedures 3.3.1 Activation/Deactivation/Registration Not applicable. 3.3.2 Invocation and operation 3.3.2.1Virtual call In case of failure situations due to calling/called user error, user state, or network conditions, appropriate failure indications will be signalled from the network and the call set-up or established call may be terminated. For detailed procedures, see Recommendation I.462. 3.3.2.2Permanent virtual circuit In case of failure situations due to user error, user state, or network conditions, appropriate failure indications will be signalled from the network. For detailed procedures, see Recommendation I.462. 3.3.3 Interrogation/Editing Not applicable. 3.4 Alternative procedures Not applicable. 3.5 Verification Not applicable. 4. Network capabilities for charging This Recommendation does not cover charging principles. Future Recommendations in the D-Series are expected to contain that information. 4.1 Virtual call charging It shall be possible to charge the subscriber accurately for the virtual call service. 4.2 Permanent virtual circuit charging It shall be possible to charge the subscriber accurately for the permanent virtual circuit service. 5. Interworking General interworking arrangements for this bearer service category are defined in Recommendation X.300. Specific interworking procedures are in Recommendation I.462. 6. Interaction with supplementary services (Not applicable.) 7. Attributes and values of attributes (including the provision of individual bearer services) 7.1 Attributes/values Information transfer attributes 1) Information transfer mode packet 2) Information transfer rate maximum throughput of a given virtual circuit is less than or equal to the maximum bit rate of the user information access channel and the throughput class of the virtual circuit 3) Information transfer capability unrestricted 4) Structure service data unit integrity 5) Establishment of communication demand (virtual call)/ permanent (permanent virtual circuit) 6) Symmetry bidirectional symmetric 7) Communication configuration point-to-point Access attributes 8) Access channel user information over virtual circuit within B or D channel. When D channelis used, maximum packet size and quality of service may be restricted. Signalling may be provided via D-chan- nel and/or virtual circuit within B-channel 9) Access protocol as specified in Recommendations I.440, I.450, I.451, I.462 and X.25 (layers 2 and 3) General attributes 10) Supplementary services provided as listed in Recommendation X.2. Oth- ers are for further study 11-13) for further study 7.2 Provision of individual bearer services a) overall provision: E b) variations of secondary attributes: +––––––––––––––+––––––––––––––––––+––––––––––––––+––––––––––––––+–––––––––––+ |Information | Establishment | Symmetry |Communication | Provision | |transfer rate | of communication | |configuration | | +––––––––––––––+––––––––––––––––––+––––––––––––––+––––––––––––––+–––––––––––+ | Note 1 | demand |Bidirectional | pt-pt | E | | | | Symmetric | | | | | | | | | | Note 1 | permanent |Bidirectional | pt-pt | E | | | | Symmetric | | | | | | | | | +––––––––––––––+––––––––––––––––––+––––––––––––––+––––––––––––––+–––––––––––+ Note 1 - The exact values of information transfer rates for the virtual call and permanent virtual circuit are for further study. c) Access +–––––––––––––––––––––––+––––––––––––––––––––––+–––––––––––––––––––+––––––––––+ |Access Channel Control |Virtual Call Control | |Provision | | | | | | | Signalling and OAM | Signalling and OAM |User information | | | (Notes 1 and 2) | (Notes 1 and 3) | | | +––––––––––+––––––––––––+––––––––––+–––––––––––+–––––––––+–––––––––+ | |Channel | Protocols | Channel | Protocols |Channel |Protocols| | |and rate | | and rate | |and rate | | | +––––––––––+––––––––––––+––––––––––+–––––––––––+–––––––––+–––––––––+––––––––––+ | D(16) |I.451, | B(64) |X.25 L3,| B(64) |X.25 L3,| A | | |I.441, | |X.25 L2,| |X.25 L2,| | | |I.430 | |I.430 | |I.430 | | +––––––––––+––––––––––––+––––––––––+–––––––––––+–––––––––+–––––––––+––––––––––+ | D(64) |I.451, | B(64) |X.25 L3,| B(64) |X.25 L3,| A | | |I.441, | |X.25 L2,| |X.25 L2,| | | |I.431 | |I.431 | |I.431 | | +––––––––––+––––––––––––+––––––––––+–––––––––––+–––––––––+–––––––––+––––––––––+ | D(16) |I.451, | D(16) |X.25 L3,| D(16) |X.25 L3,| A | | |I.441, | |I.441, | |I.441, | | | |I.430 | |I.430 | |I.430 | | +––––––––––+––––––––––––+––––––––––+–––––––––––+–––––––––+–––––––––+––––––––––+ | D(64) |I.451, | D(64) |X.25 L3,| D(64) |X.25 L3,| A | | |I.441, | |I.441, | |I.441, | | | |I.431 | |I.431 | |I.431 | | +––––––––––+––––––––––––+––––––––––+–––––––––––+–––––––––+–––––––––+––––––––––+ Note 1 - The definition of other protocols for OAM is for further study. Note 2 - The protocols listed in this column are for establishing communications with the packet handling function using out-of-band call control signals. This procedure does not apply in certain cases (for example, semi-permanent D chan- nel connection). Note 3 - The protocols listed in this column are for the establishment of a virtual circuit using X.25 procedures. These procedures do not apply to permanent virtual circuits. 8. Dynamic description Dynamic descriptions for the Recommendation I.462 procedures in the virtual call and permanent virtual circuit bearer service category are for future study. State transition diagrams for layer 3 of Recommendation X.25 (Annex B) apply for virtual call and permanent virtual circuit. I.232.2 - Connectionless bearer service category Note - This connectionless bearer service category is a different concept from, and should not be confused with, the OSI Connectionless Mode Network Service. Thus, the name of this service may change as the service is better defined. Further aspects of this bearer service category are for further study. I.232.3 - User signalling bearer service category Note - This service is different from, and should not be confused with, the user-to-user signalling supplementary service (see I.257). The user-to-user signalling supplementary service is used in conjuction with either a bearer service or a teleservice. The user signalling bearer service stands on its own and is not used in conjunction with a bearer service or a teleservice. Further aspects of this bearer service category are for further study.