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- Recommendation I.232 - Packet mode bearer services categories
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- 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.
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- 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.
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- 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.
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- The following set of bearer services categories is currently identified and more may be identified in the future:
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- - virtual call and permanent virtual circuit bearer service category;
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- - connectionless bearer service category;
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- - user signalling bearer service category.
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- I.232.1 - Virtual call and permanent virtual circuit bearer service category
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- 1. Definition
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- 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).
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- 2. Description
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- 2.1 General description
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- 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.
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- 2.2 Specific terminology
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- Not applicable.
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- 2.3 Qualifications
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- Not applicable.
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- 3. Procedures
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- 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.
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- 3.1 Provision/withdrawal
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- For further study.
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- 3.2 Normal procedures
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- 3.2.1 Activation/Deactivation/Registration
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- Not applicable.
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- 3.2.2 Invocation and operation
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- 3.2.2.1Virtual call procedures
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- a) Call establishment
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- 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.
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- b) Data transfer phase
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- 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:
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- - packetized;
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- - flow control;
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- - delivery confirmation (optional);
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- - reset/interrupt.
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- c) Terminating the call
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- 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.
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- 3.2.2.2Permanent virtual circuit procedures
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- 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.
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- 3.2.3 Interrogation/Editing
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- Not applicable.
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- 3.3 Exceptional procedures
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- 3.3.1 Activation/Deactivation/Registration
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- Not applicable.
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- 3.3.2 Invocation and operation
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- 3.3.2.1Virtual call
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- 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.
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- 3.3.2.2Permanent virtual circuit
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- 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.
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- 3.3.3 Interrogation/Editing
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- Not applicable.
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- 3.4 Alternative procedures
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- Not applicable.
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- 3.5 Verification
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- Not applicable.
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- 4. Network capabilities for charging
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- This Recommendation does not cover charging principles. Future Recommendations in the D-Series are expected to
- contain that information.
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- 4.1 Virtual call charging
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- It shall be possible to charge the subscriber accurately for the virtual call service.
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- 4.2 Permanent virtual circuit charging
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- It shall be possible to charge the subscriber accurately for the permanent virtual circuit service.
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- 5. Interworking
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- General interworking arrangements for this bearer service category are defined in Recommendation X.300. Specific
- interworking procedures are in Recommendation I.462.
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- 6. Interaction with supplementary services
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- (Not applicable.)
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- 7. Attributes and values of attributes (including the provision of individual bearer services)
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- 7.1 Attributes/values
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- Information transfer attributes
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- 1) Information transfer mode packet
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- 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
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- 3) Information transfer capability unrestricted
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- 4) Structure service data unit integrity
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- 5) Establishment of communication demand (virtual call)/ permanent (permanent virtual circuit)
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- 6) Symmetry bidirectional symmetric
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- 7) Communication configuration point-to-point
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- Access attributes
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- 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
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- 9) Access protocol as specified in Recommendations I.440, I.450, I.451, I.462 and X.25 (layers 2 and 3)
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- General attributes
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- 10) Supplementary services provided as listed in Recommendation X.2. Oth-
- ers are for further study
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- 11-13) for further study
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- 7.2 Provision of individual bearer services
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- a) overall provision: E
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- b) variations of secondary attributes:
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- +ûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûû+ûûûûûûûûûûûûûû+ûûûûûûûûûûû+
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- |Information | Establishment | Symmetry |Communication | Provision |
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- |transfer rate | of communication | |configuration | |
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- +ûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûû+ûûûûûûûûûûûûûû+ûûûûûûûûûûû+
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- | Note 1 | demand |Bidirectional | pt-pt | E |
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- | | | Symmetric | | |
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- | | | | | |
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- | Note 1 | permanent |Bidirectional | pt-pt | E |
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- | | | Symmetric | | |
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- | | | | | |
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- +ûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûû+ûûûûûûûûûûûûûû+ûûûûûûûûûûû+
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- Note 1 - The exact values of information transfer rates for the virtual call and permanent virtual circuit are for further
- study.
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- c) Access
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- +ûûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûûûûûû+ûûûûûûûûûûûûûûûûûûû+ûûûûûûûûûû+
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- |Access Channel Control |Virtual Call Control | |Provision |
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- | | | | |
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- | Signalling and OAM | Signalling and OAM |User information | |
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- | (Notes 1 and 2) | (Notes 1 and 3) | | |
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- +ûûûûûûûûûû+ûûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûû+ |
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- |Channel | Protocols | Channel | Protocols |Channel |Protocols| |
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- |and rate | | and rate | |and rate | | |
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- +ûûûûûûûûûû+ûûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûû+
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- | D(16) |I.451, | B(64) |X.25 L3,| B(64) |X.25 L3,| A |
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- | |I.441, | |X.25 L2,| |X.25 L2,| |
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- | |I.430 | |I.430 | |I.430 | |
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- +ûûûûûûûûûû+ûûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûû+
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- | D(64) |I.451, | B(64) |X.25 L3,| B(64) |X.25 L3,| A |
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- | |I.441, | |X.25 L2,| |X.25 L2,| |
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- | |I.431 | |I.431 | |I.431 | |
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- +ûûûûûûûûûû+ûûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûû+
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- | D(16) |I.451, | D(16) |X.25 L3,| D(16) |X.25 L3,| A |
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- | |I.441, | |I.441, | |I.441, | |
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- | |I.430 | |I.430 | |I.430 | |
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- +ûûûûûûûûûû+ûûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûû+
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- | D(64) |I.451, | D(64) |X.25 L3,| D(64) |X.25 L3,| A |
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- | |I.441, | |I.441, | |I.441, | |
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- | |I.431 | |I.431 | |I.431 | |
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- +ûûûûûûûûûû+ûûûûûûûûûûûû+ûûûûûûûûûû+ûûûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûû+ûûûûûûûûûû+
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- Note 1 - The definition of other protocols for OAM is for further study.
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- 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).
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- 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.
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- 8. Dynamic description
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- 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.
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- I.232.2 - Connectionless bearer service category
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- 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.
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- Further aspects of this bearer service category are for further study.
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- I.232.3 - User signalling bearer service category
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- 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.
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- Further aspects of this bearer service category are for further study.
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