ÿWPCL ûÿ2BJ|xÐ ÐÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿXP x¸)ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÐ °°°è ÐÑ Âx„|ü@Ž ÑÐ ÅH&Ø'H&Ø'Å ÐÀ ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ À Ð ÐÀ À Case À À Called User's À À Requested Service À À Called User À À Calling User Network À À Ð ÐÀ À À À Capability À À (Note 2) À À Action À À Interface Action À À ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ À À 1 À À Can analyze the À À Services 1, 2, 3 À À Return appropriate À À Pass ACK to the calling À À Ð ÐÀ À À À service and À À Preferred or Required À À ACK indication by the À À user in normal call À À Ð ÐÀ À À À accepts the À À À À response message À À control messages. À À Ð ÐÀ À À À service À À À À À À À À ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Ð ÐÀ À 2 À À Can analyze the À À Services 1, 2, 3 À À Clears the call with À À Pass same cause to the À À Ð ÐÀ À À À service but does À À Required À À appropriate message À À calling user in the normalÀ À Ð ÐÀ À À À not accept the À À À À and cause À À call control clearing À À Ð ÐÀ À À À service À À À À À À message. À À Ð ÐÀ À À À ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Ð ÐÀ À À À À À Services 1 (explicit À À Ignore the request or À À Pass NACK to the calling À À Ð ÐÀ À À À À À invocation), 2, 3 À À return appropriate À À user À À Ð ÐÀ À À À À À Preferred À À NACK indication by À À À À Ð ÐÀ À À À À À À À the response message, À À À À Ð ÐÀ À À À À À À À the call is not À À À À Ð ÐÀ À À À À À À À cleared À À À À Ð ÐÀ À À À ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Ð ÐÀ À À À À À Service 1 (implicit À À Return appropriate À À Pass NACK to the calling À À Ð ÐÀ À À À À À invocation) Preferred. À À NACK indication in À À user in normal call À À Ð ÐÀ À À À À À À À the response message. À À control messages. The callÀ À Ð ÐÀ À À À À À À À The call is not À À is not cleared. À À Ð ÐÀ À À À À À À À cleared À À À À ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ À Ð ÐÀ À 3 À À Cannot analyze À À Services 1, 2, 3 À À Treats as an À À Clears the call with À À Ð ÐÀ À À À the service À À Required À À unrecognized optional À À appropriate message and À À Ð ÐÀ À À À request. À À À À information element À À cause. À À Ð ÐÀ À À À ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ Ð ÐÀ À À À À À Services 1, 2, 3 À À Treats as an À À Passes back the implicit À À Ð ÐÀ À À À À À Preferred À À unrecognized optional À À user responses to the À À Ð ÐÀ À À À À À À À information element À À calling node (Note 3) À À À ÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀÀ À Ð Ð Ð ` ÐÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿXH øP ÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÐ Å°6Ø'°6Ø'Å Ð Ð ( ÐÁXÁÁHÁWhen interworking with a non©ISDN network occurs a PROGRESS or an ALERTING message with the Progress indicator information element indicating # 1 "call is not end©to©end ISDN; further call progress information may be available in©band" is sent to the calling user to indicate that the service cannot be guaranteed. Ð H ÐÁXÁÁHÁIf any one or all of the services requested is indicated as required, then the network or called user that cannot support or provide the request Ð à Ðwill send a RELEASE COMPLETE with cause # 50 "requested facility not subscribed" or cause # 69 "requested facility not implemented" and the service rejection associated with that service. 7.1.7.4Á  ÁÓÓÃÃTransfer of USER INFORMATION messagesÄÄ ÁXÁÁHÁThe transfer of USER INFORMATION messages is defined in ÀÀÀÀ 7.1.4.4 and 7.1.5.6. 7.1.8ÁHÁÁ  ÁÃÃSummary of actions to be taken by the called side and subsequentÄÄ ÁXÁÁHÁÃÃnetwork actionÄÄ ÁXÁÁHÁActions to be taken by the called side and the subsequent network actions are summarized in the following table. ÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿH øÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÁHÁiii)Á øÁService 3: user©to©user signalling exchanged while a call is in the Active state, within USER INFORMATION messages. ÁHÁAll three services may be used separately or in any combination in association with a single call. As an option, at call setup, users may be able to specify that the requested user©to©user signalling services(s) is (are) required for the call, i.e. the call should not be completed if user©to©user information cannot be passed. 7.1.2ÁHÁÃÃExplicit invocation procedures for services 1, 2 and 3ÄÄ ÁHÁServices 1, 2 and 3 listed above may be provided on a per call basis following an explicit request from a user. The standard explicit invocation procedure makes use of the Facility information element defined in ÀÀ 4. ÁHÁIn addition, or alternatively, some networks may support explicit invocation procedures making use of: ÁHÁ©Á  ÁKeypad facility information element; or ÁHÁ©Á  ÁFeature activation information element. ÁHÁThe exact operation of stimulus invocation procedures are network dependent but must follow the rules defined in ÀÀ 8 of this Recommendation. More detailed protocol aspects can also be found in ÀÀ 4 (for the keypad protocol invocation) and in ÀÀ 5 (for the feature management protocol invocation) of Recommendation Q.932. ÁHÁWhen a network supports more than one invocation procedure, the following principles shall be followed: ÁHÁ©Á  Áfor invocations using the Keypad facility information element, ÁHÁÁ  Áthe network will convey the remote user's response using a ÁGÀ!HÁÁH8"IÁSignal, a Display, or a Feature indication information element; ÁHÁ©Á  Áfor invocations using the Feature activation information element, the ÂHHÂÂX  Ânetwork will convey the remote user's response using a Feature indication information element;ÆÆ Ð ` Ð Ð   ÐÂHH©Âà  Âfor invocations using the Facility information element, the ÆÆ Ð 8 ÐÂHHÂÂX  Ânetwork will convey the remote user's response using a FacilityÆÆ ÂHHÂÂX  Âinformation element.ÆÆ Ð ` Ð Ð ° ÐÁHÁIn the network©to©user direction, explicit service 1 and service 2 requests may be indicated using the Facility information element. Ð À ÐÂHHÂIn the network to user direction, service 3 requests may be indicatedÆÆ Ð ` Ðusing: ÂHHÂi) Signal information element (see note);ÆÆ ÂHHÂii) Display information element (see note);ÆÆ ÂHHÂiii) Feature indication information element (see note); orÆÆ ÂHHÂiv) Facility information element.ÆÆ Ð H ÐÁHÁFor indications using the Facility information element, the user will respond with a Facility information element. No response is needed when any of the first three information elements are used. ÃÃNoteÄÄ © These may be used only when the network has knowledge that the user receiving the notification has subscribed to the service. In this case, the network will generate the service confirmation to the originating user (i.e., the user requesting the service) on behalf of the user who did not originate the service request. For service 3, invoked during the active state of a call, the message use is symmetric across the user©network interface; i.e., the FACILITY message is returned in response to a FACILITY message. 7.1.3ÁHÁÃÃUser©to©user signalling service 1ÄÄ 7.1.3.1Á  ÁÃÃGeneral characteristicsÄÄ ÁHÁService 1 allows the users to communicate by means of user©to©user signalling by transferring user©to©user information within Recommendation Q.931 call control messages during call establishment and clearing phases. 7.1.3.2Á  ÁÃÃUser©to©user signalling © implicit service requestÄÄ ÃÃ(preferred, i.e. © not required)ÄÄ ÁHÁService 1 may be implicitly requested by including a User©user information element of variable length as specified in ÀÀ 4.5.29 in the SETUP message transferred across the user©network interface at the calling side as described in ÀÀ 5.1.1. This information element is transported by the network and delivered unchanged in the User©user information element included in the SETUP message transferred across the user©network interface at the called side as described in ÀÀ 5.2.1. For invocation purposes, this information element must be at least three octets long as defined in ÀÀ 4.5.29. ÁHÁIn the case where contention by users for the incoming call is not allowed (e.g., when the SETUP message containing an implicit service invocation is delivered using a point©to©point link at the data link layer or when the network, despite using broadcast capability at layer 2, knows based on the first response received from the user that no contention takes place), a User©user information element may be included in the ALERTING and/or CONNECT messages transferred across the user©network interface at the called side as described in ÀÀ 5.2.5. The content of this information element is transported by the network and delivered in the User©user information element included in the corresponding message(s) transferred across the user©network interface at the calling side as described in ÀÀÀÀ 5.1.7 and 5.1.8. ÁHÁOn call request, the SETUP message sent by the calling user will contain a service 2 request. The SETUP message sent by the network at the called side, will also contain an explicit service 2 request. ÁHÁIf the called user can support USER INFORMATION messages during call establishment, a service 2 acceptance shall be included in the ALERTING message sent to the network. This explicit acceptance indication shall be forwarded in the ALERTING message sent by the network to the calling user. 7.1.4.3Á  ÁÃÃService rejectionÄÄ ÁHÁIf the called user or network does not understand the service 2 request, then the ALERTING message returned to the calling user will not include either a service 2 acceptance or rejection. This type of response shall be taken as an implicit rejection of service 2. Alternatively, if the network or called user cannot support USER INFORMATION messages during call establishment, and the request is indicated as preferred, a service 2 rejection is included in the ALERTING message. ÁHÁIf the service 2 request indicated required, and the called user or network cannot support or provide the service, a RELEASE COMPLETE is sent with cause # 50 "requested facility not subscribed" or cause # 69 "requested facility not implemented" and a service 2 rejection. ÁHÁIf the called user does not include a service 2 acceptance or rejection in the ALERTING message, the network shall return an explicit rejection in the ALERTING message sent to the calling user. ÁHÁIn the case of interworking with a non©ISDN network, a PROGRESS or ALERTING message with the progress indicator information element indicating # 1 "call is not end©to©end ISDN; further call progress information may be available in©band" is sent to the calling user to indicate that the full service cannot be guaranteed. 7.1.4.4Á  ÁÃÃTransfer of USER INFORMATION messagesÄÄ ÁHÁOnce an ALERTING message has been received, both the involved users can transfer information between themselves by transferring USER INFORMATION messages across the user©network interface. The network provides for the transfer of such messages from the calling to the called side and vice versa. ÁHÁThe USER INFORMATION message includes the Call reference, the Protocol discriminator, and the User©user information elements as defined in ÀÀ 3.1.26. The More data information element may also be included by the source user to indicate to the remote user that another USER INFORMATION message will follow, containing information belonging to the same block. The use of More data information element is not supervised by the network. ÁHÁIf the user©to©user signalling facility is provided, no more than two USER INFORMATION messages may be transferred in each direction after the ALERTING message and before the CONNECT message. ÁHÁSending or receiving of USER INFORMATION messages does not change the state of the call. 7.1.5ÁHÁÃÃUser©to©user signalling service 3ÄÄ 7.1.5.1Á  ÁÃÃGeneralÄÄ ÁHÁService 3 allows the users to communicate by means of transferring USER INFORMATION messages during the Active state of a call. This service allows either an implicit or explicit rejection (see ÀÀ 7.1.5.3.). This service may be requested during call establishment or during the Active state of the call. 7.1.5.2Á  ÁÃÃService request during call establishmentÄÄ ÁHÁProcedures for call establishment are as described in ÀÀÀÀ 5.1 and 5.2 with the following modifications. ÁHÁOn call request, the SETUP message sent by the calling user will contain a service 3 request. The SETUP sent by the network at the called side will also contain a service 3 request. ÁHÁIf the called user can support USER INFORMATION message transfer during the Active state, a service 3 acceptance shall be included in the CONNECT message. 7.1.5.3Á  ÁÃÃRejection of service requested during call establishmentÄÄ ÁHÁIf the called user or network does not understand the service 3 request, then the CONNECT message returned to the calling user shall not include either a service 3 acceptance or rejection. This type of response will be taken as an implicit rejection of service 3. Alternatively, if the network or called user cannot support USER INFORMATION messages during the Active state, and the request is indicated as preferred, a service 3 rejection is included in the CONNECT message. If the service 3 request indicated required, and the called user or network cannot support or provide the service, a RELEASE COMPLETE is sent with cause # 50 "requested facility not subscribed" or cause # 69 "requested facility not implemented" and a service 3 rejection. ÁHÁIf the called user does not include a service 3 acceptance or rejection in the CONNECT message, the network shall return a service 3 rejection in the CONNECT message sent to the calling user. ÁHÁWhen interworking with a non©ISDN network occurs a PROGRESS or an ALERTING message with the Progress indicator information element indicating # 1 "call is not end©to©end ISDN; further call progress information may be available in©band" is sent to the calling user to indicate that the service cannot be guaranteed. 7.1.5.4Á  ÁÃÃService request after call establishmentÄÄ ÁHÁDuring the Active state of a call, a user may request service 3 preferred only. A FACILITY message indicating a service 3 request is sent from the requesting user to the network. The network shall indicate the service 3 request to the user that did not request service 3 in the FACILITY message. ÁHÁIf the user that did not request service 3 can support the transfer of USER INFORMATION messages during the Active state, a service 3 acceptance is returned in the FACILITY message. This explicit acceptance indication shall be conveyed back to the requesting user in a FACILITY message. 7.1.6ÁHÁÃÃUnexpected USER INFORMATION messagesÄÄ 7.1.6.1Á  ÁÃÃReceipt of USER INFORMATION messages in incompatible call statesÄÄ ÁHÁWhenever a USER INFORMATION message is received from the user and it is not allowed by an invoked service (e.g., in any other state than Active where only service 3 is invoked), the message will be discarded by the network. The network will respond with a STATUS message with a cause # 43 "access information discarded". 7.1.6.2Á  ÁÃÃReceipt of unexpected USER INFORMATION messagesÄÄ ÁHÁWhenever a USER INFORMATION message is received by the network from the calling or called user after the network has indicated that user©to©user cannot be supported, that message shall be discarded without further action. 7.1.7ÁHÁÃÃRequesting user©to©user signalling services 1, 2 and 3ÄÄ 7.1.7.1Á  ÁÃÃGeneralÄÄ ÁHÁThis section describes procedures for requesting services 1, 2 and 3 in the same SETUP message. These services are described in ÀÀÀÀ 7.1.3, 7.1.4 and 7.1.5, respectively. ÃÃNoteÄÄ © User©to©user service 1 implicit request/acceptance follows ÀÀ 7.1.3.2 procedures. Only explicit service 1 requests may follow the procedure in this section. 7.1.7.2Á  ÁÃÃCall establishmentÄÄ ÁHÁProcedures for call establishment are described in ÀÀÀÀ 7.1.3.3, 7.1.4.2, and 7.1.5.2 with the following modifications. On call request, the SETUP message sent by the calling user will contain independent service 1, 2, 3 requests. ÁHÁThe SETUP sent by the network at the called sides will also contain the same independent service requests. If the called user can support the indicated services, then specific services acceptances may all be indicated in the ALERTING message. Alternatively, the user may accept services 1 and 2 in the ALERTING message, as defined in ÀÀÀÀ 7.1.3.3 and 7.1.4.2, and service 3 in the CONNECT message, as defined in ÀÀ 7.1.5.2. 7.1.7.3Á  ÁÃÃService rejectionÄÄ ÁHÁIf the called user or network does not understand any of the services requested, then the ALERTING and CONNECT messages returned to the calling user will not include either a service acceptance or rejection. This type of response will be taken as an implicit rejection of all services. If the called user or network does not understand a specific service request, that specific service is implicitly rejected following the procedures defined in ÀÀÀÀ 7.1.3.6, 7.1.4.3 or 7.1.5.3. Alternatively, if the network or called user cannot support one or more services requested, and the service requests were indicated as preferred, the specific service rejection may be included in the ALERTING message. The services may also be rejected following the procedures in ÀÀÀÀ 7.1.3.6, 7.1.4.3 or 7.1.5.3. ÁHÁIf the called user does not include a service 1, 2 or 3 acceptance or rejection in the ALERTING and/or CONNECT message, the network shall return a service 1, 2 or 3 rejection in the ALERTING and/or CONNECT message sent to the calling user. 7.2ÁHÁÃÃProcedures for user©to©user signalling not associated with ÄÄ ÁHÁÃÃcircuit©switched callsÄÄ 7.2.1ÁHÁÃÃGeneral characteristicsÄÄ ÁHÁThis feature allows the users to communicate by means of user©to©user signalling without setting up a circuit©switched connection. A temporary signalling connection is established and cleared in a manner similar to the control of a circuit©switched connection. 7.2.2ÁHÁÃÃCall establishmentÄÄ ÁHÁProcedures for call establishment are as described in ÀÀÀÀ 5.1 and 5.2 with the following modifications. ÁHÁOn call request, the calling user sends a SETUP message identifying, within the Bearer capability and Channel identification information elements, a temporary signalling connection to be established on SAPI=O. The SETUP message is encoded to indicate: ÁHÁBearer capability information element Ð ( ÐÂHH©Âà  ÂUnrestricted digital information in the information transfer capability field;ÆÆ Ð ` Ð ÂHH©Âà  ÂPacket mode in the transfer mode field;ÆÆ Ð ° ÐÂHH©Âà  ÂUser information layer 2 protocol is Recommendation Q.931 and user information layer 3 protocol is Recommendation Q.931 in the layer and protocol identification field.ÆÆ Ð ` Ð ÁHÁChannel identification information element ÂHH©Âà  ÂExclusive in the preferred/exclusive field;ÆÆ ÂHH©Âà  ÂD Channel in the D©Channel indicator field;ÆÆ ÂHH©Âà  ÂNo channel in the channel selection field.ÆÆ Ð ( ÐÁHÁIf the network determines that the requested temporary signalling connection service is not authorized or is not available, the network Ð à Ðshall initiate call clearing in accordance with ÀÀ 5.3.2(a) or ÀÀ 5.3.2(c) with one of the following causes: ÂHHÂa)Âh   Â#57 "bearer capability not authorized"ÆÆ Ð ` Ð ÂHHÂb)Âh   Â#58 "bearer capability not presently available"ÆÆ ÂHHÂc)Âh   Â#63 "service or option not available, unspecified"ÆÆ ÂHHÂd)Âh   Â#65 "bearer service not implemented"ÆÆ Ð Ð ÐÁHÁThe called user accepts the temporary signalling connection request by sending a CONNECT message towards the calling user. After the called user has received a CONNECT ACKNOWLEDGE message, it may begin sending USER INFORMATION messages. Once the calling user receives a CONNECT message, it can begin sending USER INFORMATION messages. 7.2.3ÁHÁÃÃTransfer of USER INFORMATION messagesÄÄ ÁHÁOnce a temporary signalling connection is established both users can transfer information between themselves by transferring USER INFORMATION messages across the user©network interface. The network provides for the transfer of such messages from the called to the calling side and vice versa. ÁHÁThe USER INFORMATION message includes the Call reference, the Protocol discriminator, and the User©to©user information elements as defined in ÀÀ 3.3.13. The More data information element may also be sent by the source user to indicate to the remote user that another USER INFORMATION message will follow, containing information belonging to the same block. The use of the More data information element is not supervised by the network. 7.2.4ÁHÁÃÃCongestion control of USER INFORMATION messagesÄÄ ÁHÁCongestion control procedures are the same as those described in ÀÀ 7.1.5.7. 7.2.5ÁHÁÃÃCall clearingÄÄ ÁHÁThe clearing of an established temporary signalling connection can be initiated by the user or network by sending a RELEASE message towards the far end user. The clearing procedure followed and the timers involved are the same as those for clearing a circuit©switched connection as described in ÀÀÀÀ 5.3.3 and 5.3.4. Ô ñ,ÔŒ