7.6.4.3	Data transfer phase
	During the data transfer phase expedited data procedures can be applied if the expedited data negotiation parameter, conveyed in the call confirmation phase, had the value expedited data.
	Note – Expedited data procedures in PSPDN and ISDN(ps) can be performed by using interrupt packet procedures.
8	Arrangements for call progress signals
	Table 8–1/X.301 indicates different networks using different sets of call progress signals.
TABLE 8–1/X.301
Use of different sets of call progress signals by different networks

Call Progress Signal	 Applies to Circuit Switched Data Transmission Service			 Applies to Packet Switched Data Transmission Service			
	PSTN	CSPDN	ISDN	ISDN	PSPDN	MSS	
X.96		X		X	X	X	
Q.931			X	X			
Q.699			X				
	In the case of terminals connected to public networks via private networks, call progress signals originated in the private network are distinguished from those originated in the public data network. In CSPDN, the call progress signal “subaddress called” is sent by the destination PDN when it passes a call containing private network address information to the called DTE/DCE interface. Any subsequent call progress signals will have been originated by the private network. In PSPDN, a specific and distinct coding range is allocated for call progress signals originated in a private network.
	The internetwork arrangements described in this paragraph relate to the transfer across networks of the call progress signals. Different categories of interworking are considered:
–	interworking by call control mapping (ICCM),
–	interworking by port access (IPA).
	Table 8–2/X.301 shows the different cases of interworking with regard to call progress signals, referring to the appropriate sections.
TABLE 8–2/X.301
Different cases of interworking with regard to call progress signals
Q.699
(SS No. 7)	ICCM:	§ 8.3.1
IPA:	NA	
Q.931	ICCM:	§ 8.6.1
IPA:	NA	ICCM:	§ 8.2.1
IPA:	NA	
X.96	ICCM:	§ 8.5.1
IPA:	§ 8.5.2	ICCM:	§ 8.4.1
IPA:	§ 8.4.2	ICCM:	§ 8.1.1
IPA:	§ 8.1.2	
Q.699 (SS No. 7)	Q.931	X.96	
8.1	Interworking arrangements involving call progress signals defined in Recommendation X.96 only
8.1.1	Interworking by call control mapping
8.1.1.1	Call progress signals during call establishment
8.1.1.1.1	Call progress signals originated by the calling DTE (call request phase)
	At the time of the call request, the calling DTE is not transmitting any call progress signal.
8.1.1.1.2	Call progress signals generated by the originating PDN (call request phase)
	At the time of the call request, the originating PDN (including the DCE associated with the calling DTE) may have to clear the call, due to constraints related to the DTE/DCE interface of that calling DTE.
8.1.1.1.2.1	Incorrect called DTE address in a call request
8.1.1.1.2.1.1	The originating PDN may receive from the calling DTE a call request with a called DTE address which is not correct. If the originating PDN detects such a difficulty, it should clear the call with NOT OBTAINABLE indication. A possible reason is that the DCC or DNIC is the one assigned to the originating PDN, but the remaining digits of the address are not assigned to any DTE on that PDN.
	Note 1 – The transmission by the calling DTE of an incorrect national prefix (see § 2.5 of Recommenda-tion X.121) should be considered as a local procedure error.
	Note 2 – The reaction of the originating PDN to an incorrect called DTE address received from the calling DTE is for further study.
8.1.1.1.2.2	Invalid facility requested by the calling DTE
	When receiving from the calling DTE a call request that requires an optional user facility which is not offered to that DTE, the originating PDN should CLEAR the call with an INVALID FACILITY REQUEST indication.
	Possible reasons include:
a)	request for a facility which has not been subscribed by the DTE;
b)	request for a facility which is not available in the originating PDN;
c)	facility request which has not been recognized as valid by the originating PDN.
	The exact circumstances for such call clearing by the originating PDN with an indication of invalid facility request, are detailed in the relevant X–Series Recommendations, i.e. DTE/DCE interface Recommendations, interwork signalling Recommendations.
8.1.1.1.2.3	Calling DTE procedure error related to a call request
8.1.1.1.2.3.1	When receiving a call request from the calling DTE, the originating PDN may detect a procedure error caused by the DTE. The originating PDN should then CLEAR the call with LOCAL PROCEDURE ERROR indication. Detailed circumstances of such procedure errors in a call request are indicated in the relevant X–series DTE/DCE interface Recommendations.
	Possible circumstances include:
a)	call request on a logical channel which is not in the ready state (in the case of an X.25 interface);
b)	incorrect reference of a logical channel for the call (in the case of an X.25 interface);
c)	incorrect format during call establishment.
8.1.1.1.3	Call progress signals generated by an IDSE (call request phase)
	At the time of a call request, an International Data Switching Equipment (IDSE) involved in call establishment may have to clear the call.
8.1.1.1.3.1	Incorrect called DTE address
8.1.1.1.3.1.1	In some calls, an IDSE may receive a called DTE address which is not compatible with the numbering plan or not assigned to any DTE at that time. The IDSE should then clear the call with NOT OBTAINABLE indication. Possible reasons include: Unknown called DCC or DNIC.
8.1.1.1.3.1.2	However, it should also be noted that an IDSE should, if possible, not transmit to the next IDSE a call request with a called DTE address which does not correspond to a predetermined route. If an IDSE receives a called DTE address which does not conform to predetermined route, the call may be cleared with ACCESS BARRED indication.
8.1.1.1.3.2	Internal network failure or congestion
8.1.1.1.3.2.1	When an IDSE detects that all possible suitable routes, from the calling DTE to the called DTE via this IDSE, are temporarily unavailable, the IDSE will clear the call with NETWORK CONGESTION indication.
8.1.1.1.3.3	Internal network failure on the transit route(s)
	A temporary network failure may force an IDSE to clear the call request passing through it, with NETWORK CONGESTION indication.
8.1.1.1.3.4	Facility not available on the transit route(s)
	When an IDSE detects a request for a facility intentionally not available on the transit route(s), the IDSE clears the call with INCOMPATIBLE DESTINATION indication or NETWORK CONGESTION indication in the case of CSPDN.
8.1.1.1.3.5	Charging facility not available on the transit route(s)
	When an IDSE detects that requested charging facilities are intentionally not available on the transit route(s) it clears the call with INCOMPATIBLE DESTINATION indication or NETWORK CONGESTION indication in the case of CSPDN.
8.1.1.1.3.6	Access protection facility not available on the transit route(s)
	When an IDSE detects that requested access protection facilities are intentionally not available on the transit route(s), it clears the call with ACCESS BARRED indication.
8.1.1.1.4		Call progress signals generated by the destination PDN (call request phase)
	At the time of a call request, the destination PDN (including the DCE associated with the called DTE) may have to clear the call, due to constraints related to the DTE/DCE interface of that called DTE.
8.1.1.1.4.1	DTE/DCE interface not operational
	The DTE/DCE interface of the called DTE may be out of order. Possible reasons include:
a)	DTE uncontrolled not ready,
b)	DCE power off,
c)	Network fault in the local loop,
d)	Level 1 not functioning (X.25 only),
e)	Level 2 not in operation (X.25 only).
8.1.1.1.4.1.1	If the called DTE interface is not operational, and an incoming call cannot therefore be transmitted to that DTE, the destination PDN should clear the call with OUT OF ORDER indication, or in CSPDN with either UNCONTROLLED NOT READY, DCE POWER OFF or NETWORK FAULT IN THE LOCAL LOOP indication.
	Note – Special conditions may apply, if a call redirection facility is subscribed to the called DTE.
8.1.1.1.4.2	Busy DTE/DCE interface
8.1.1.1.4.2.1	When the called DTE is detected by the destination PDN as engaged on other call(s), and therefore as not being able to accept a new incoming call, the destination PDN should clear the call with NUMBER BUSY indication. The called DTE is not indicating the incoming call.
	Note 1 – In case of an X.25 interface, some logical channel may be reserved (e.g. for outgoing calls) and be unavailable for incoming calls (see also Annex B of Recommendation X.25). The number busy condition described in this section applies if at least one logical channel supports incoming calls.
	Note 2 – Special conditions may apply if a call redirection facility is subscribed to by the called DTE.
	Note 3 – In the case where the called DTE subscribes to the Hunt group facility the busy condition occurs when all available circuits/channels are busy in all DTE/DCE interfaces in the Hunt group.
8.1.1.1.4.2.2	When the called DTE interface is an X.25 interface, a call collision may occur on one of the logical channels. If such a collision occurs, it normally means that the X.25 interface is saturated and cannot therefore accept any additional calls at that time. The called DTE is then given priority for its call establishment, and the destination PDN should clear the incoming call with NUMBER BUSY indication. The incoming call is not transmitted to the called DTE.
8.1.1.1.4.3	Non–acceptance of a facility by the called DTE
8.1.1.1.4.3.1	Except in the cases specified in §§ 8.1.1.1.4.3.2, 8.1.1.1.4.4 and 8.1.1.1.4.5, when the called DTE interface does not support a function or facility requested in the incoming call, the destination PDN should clear the call with INCOMPATIBLE DESTINATION indication (for PSPDN). The incoming call is not transmitted to the called DTE. The call progress signal used in CSPDN is for further study.
	The exact circumstances for such call clearing by the destination PDN are detailed in the relevant X–series DTE/DCE interface Recommendations.
8.1.1.1.4.3.2	When the called DTE in PSPDN has not subscribed to the fast select acceptance facility, the destination PDN should clear a fast select call with FAST SELECT ACCEPTANCE NOT SUBSCRIBED indication. The incoming call is not transmitted to the called DTE.
8.1.1.1.4.4	Specific charging facility requested by the called DTE
8.1.1.1.4.4.1  When the called DTE has not subscribed to the reverse charging acceptance facility, and if an incoming call requests reverse charging, the destination PDN should clear that call with REVERSE CHARGING ACCEPTANCE NOT SUBSCRIBED indication. The incoming call is not transmitted to the called DTE.
8.1.1.1.4.5	Specific access protection conditions required by the called DTE
8.1.1.1.4.5.1	If an incoming call is destined for a DTE which has subscribed to the incoming calls barred facility, the destination PDN should clear the call with ACCESS BARREDindication. The incoming call is not transmitted to the called DTE.
8.1.1.1.4.5.2	If the destination PDN detects that the calling DTE is not permitted to make the connection to the called DTE, it should clear the call with ACCESS BARRED indication. The incoming call is not transmitted to the called DTE. Possible reasons include:
a)	incompatible closed user group;
b)	unauthorized access between the calling DTE and the called DTE. The possible exact circumstances of such restrictions are for further study.
	Note – The fact that the calling DTE is not permitted to make the connection to the called DTE may be previously detected on the international part of the route where the call would then be cleared. In that case, the destination PDN is not aware of the incoming call.
8.1.1.1.5	Call progress signals generated by the called DTE (call request and call confirmation phases)
	The called DTE may decide to refuse the incoming call. It will then clear the call with DTE ORIGINATED indication (in PSPDN). In CSPDN, the destination PDN may signal SUBADDRESS CALLED, following which a call progress signal may be indicated in a clearing signal from the DTE. Call progress signals generated by the called DTE are transferred to the calling DTE.
8.1.1.1.6	Call progress signals generated by the destination PDN (call confirmation phase)
8.1.1.1.6.1	Called DTE procedure error related to a call acceptance
8.1.1.1.6.1.1	When expecting a CALL ACCEPTED indication from the called DTE, the destination PDN may detect a procedure error caused by the DTE. The destination PDN should then clear the call, with LOCAL PROCEDURE ERROR indication to the called DTE, and REMOTE PROCEDURE ERROR to the calling DTE. Detailed circumstances of such procedure errors in a call accepted indication are described in the relevant X–series DTE/DCE interface Recommendations. Possible circumstances include incorrect format of the CALL ACCEPTED indication.
8.1.1.1.7	Call progress signals generated by an IDSE (call confirmation phase)
	For further study.
8.1.1.1.8	Call progress signals generated by the originating PDN (call confirmation phase)
	For further study.
8.1.1.1.9	Call progress signals resulting of call abortion (call request and call confirmation phases)
	For further study.
8.1.1.2	Clearing call progress signals during data transfer phase
8.1.1.2.1	Clearing call progress signals generated by a DTE (data transfer phase)
8.1.1.2.1.1	 When a call clearing comes from an X.25 DTE, the following rules apply:
8.1.1.2.1.1.1	The clearing cause should be DTE ORIGINATED.
8.1.1.2.1.1.2	A diagnostic of one octet may be transmitted by the DTE, is passed unchanged from the clearing DTE to the other DTE.
8.1.1.2.1.2	In CSPDN no call progress signal is generated when initiating clearing during the data transfer phase.
8.1.1.2.2	Clearing call progress signals generated by a terminating PDN (data transfer phase)
	After call establishment, either of the two terminating PDNs may have to clear the call, due to events occurring at the corresponding DTE/DCE interface.
8.1.1.2.2.1	DTE/DCE interface not operational
8.1.1.2.2.1.1	When a DTE/DCE interface on a PSPDN ceases to be operational, and cannot therefore convey any more signals for a call already established through that interface, the terminating PDN may clear that call with OUT OF ORDER indication. Possible reasons include:
a)	Layer 1 not functioning;
b)	Layer 2 not in operation.
	Note 1 – The exact circumstances, in which the terminating PDN would have to clear the virtual call because of the out of order condition of the DTE/DCE interface, are for further study.
	Note 2 – In the case of packet switched services, although the basic out of order indication is transmitted for either condition a) or b) above, the diagnostic may give more detail.
	Note 3 – When the network is ready to resume normal operation after a temporary failure or congestion, the terminating PDN may inform the DTE with a NETWORK OPERATIONAL indication. In the case of an X.25 interface, this information is passed in a restart indication packet.
8.1.1.2.2.2	Procedure error at a DTE/DCE interface
8.1.1.2.2.2.1	When a procedure error caused by the DTE on a PSPDN is detected that necessitates a call clearing, the terminating PDN should clear the call with LOCAL PROCEDURE ERROR indication to the local DTE, and with REMOTE PROCEDURE ERROR indication to the remote DTE. Detailed circumstances of such procedure errors are indicated in the relevant X–series DTE/DCE interface Recommendations (e.g. incorrect format, expiration of a time–out).
8.1.1.2.3	Clearing call progress signals generated by an IDSE (data transfer phase)
	After call establishment, an International Data Switching Equipment (IDSE) may have to clear a call due to some constraints in the international transit part of the route.
8.1.1.2.3.1	Internal network failure or congestion
	A temporary network failure or congestion may force an IDSE to clear call passing through it, with NETWORK CONGESTION indication (PSPDN only).
8.1.1.2.3.2	Facility not available on the transit route(s)
	When an IDSE detects that it is not possible to offer a facility at a certain time, it clears the call passing through it with NETWORK CONGESTION indication (PSPDN only).
8.1.1.2.4	Possible collisions between clearing call progress signals (data transfer phase)
	For further study.

8.1.1.3	Reset call progress signals during data transfer
	This paragraph only applies to packet switched services, in which a virtual call or a permanent virtual circuit may be reset.
8.1.1.3.1	Reset call progress signals generated by a DTE (data transfer phase)
8.1.1.3.1.1	When a reset comes from an X.25 DTE, the following rules apply:
8.1.1.3.1.1.1	The reset cause should be DTE ORIGINATED.
8.1.1.3.1.1.2	A diagnostic of one octet may be transmitted by the DTE, and is passed unchanged from the resetting DTE to the other DTE.
8.1.1.3.2	Reset call progress signals generated by a terminating PDN (data transfer phase)
8.1.1.3.2.1	When a failure occurs at an X.25 DTE/DCE interface, without call clearing being necessary, the terminating PDN may reset the virtual call with OUT OF ORDER indication.
	Note – The exact circumstances, in which the terminating PDN would have to reset the virtual call because of the out of order condition at the DTE/DCE interface, are for further study.
8.1.1.3.2.2	On an X.25 interface, certain procedure errors caused by the DTE may not necessitate a call clearing. The terminating PDN should then reset the virtual call with LOCAL PROCEDURE ERROR indication to the local DTE, and with REMOTE PROCEDURE ERROR indication to the remote DTE. Detailed circumstances of such procedure errors are indicated in Recommendation X.25.
8.1.1.3.2.3	When an X.25 interface is ready to resume normal data transfer on a permanent virtual circuit after a failure or out of order condition (e.g. restart), the terminating PDN should reset the permanent virtual circuit with REMOTE DTE OPERATIONAL indication.
8.1.1.3.3	Reset call progress signals generated by an IDSE (data transfer phase)
8.1.1.3.3.1	Internal network failure or congestion
	In a permanent virtual circuit, a network failure or congestion may force an IDSE to send a reset packet with NETWORK OUT OF ORDER indication toward both DTEs involved.
8.1.1.3.4	Possible collisions between reset call progress signals (data transfer phase)
	For further study.
8.1.2	Interworking by port access
	For further study.
8.2	Internetwork arrangements involving call progress signals defined in Recommendation Q.931 only
8.2.1	Interworking by call control mapping
	For further study.
8.3	Internetwork arrangements involving call progress signals defined in Recommendation Q.699 only
8.3.1	Interworking by call control mapping
	For further study.
8.3.2	Interworking by port access
	For further study.
8.4	Internetwork arrangements involving call progress signals defined in Recommendations X.96 and Q.931
8.4.1	Interworking by call control mapping
	For further study.
8.4.2	Interworking by port access
	For further study.
8.5	Internetwork arrangements involving call progress signals defined in Recommendations X.96 and Q.699
8.5.1	Interworking by call control mapping
	For further study.
8.5.2	Interworking by port access
	For further study.
8.6	Internetwork arrangements involving call progress signals defined in Recommendations Q.931 and Q.699
8.6.1	Interworking by call control mapping
	See Recommendation Q.699.
APPENDIX I
(to Recommendation X.301)
Protocol elements of different networks used for
the facilities and arrangements described in this Recommendation
	This Appendix describes the protocol elements of different networks, used for the facilities and arrangements described in this Recommendation.
	The following access protocols or protocol combinations are considered:
I.1	Circuit switched data transmission services:
CSPDN	X.20, X.20 bis, X.21, X.21 bis, X.22
ISDN	I.420, I.421
I.2	Packet switched data transmission service:
CSPDN						X.25, X.32
ISDN						X.31
Mobile data systems			X.350/X.352
	The following Table I–1/X.301 shows the protocol elements in each of the protocol combinations, used in the call request phase, call confirmation phase, and call clearing phase of the call, and which can be utilized for conveyance of the parameters for the facilities and arrangements described in this Recommendation.
	The following tables summarize how the arrangements and facilities described in this Recommendation apply to the call request phase, call confirmation phase, and call clearing phase of the call.
Conventions used in the Tables I–2/X.301 to I–7/X.301:
*	The arrangement or facility parameter (if requested) will be conveyed (by means of the protocol elements shown in Tables I–1/X.301.
B	The arrangement or facility parameter (if requested) will be conveyed and has a boolean value.
(=)	The conveyed parameter has the identical value as the parameter supplied by the remote DTE initiating this phase of the call.
(³)	The conveyed parameter has a greater or equal value than the parameter supplied by the remote DTE initiating this phase of the call.
(£)	The conveyed parameter has a smaller or equal value than the parameter supplied by the remote DTE initiating this phase of the call. In case of a boolean, the conveyed parameter value may have changed from true to false compared with the value supplied by the remote DTE initiating this phase of the call.
TABLE I–1/X.301
Protocol elements that can be used in the different phases of a call for the
conveyance of facility parameters
Circuit Switched Data Transmission Service 		Call Request Phase		Call Confirmation Phase		Call Clearing Phase		
Network	Protocol(s)	Calling DTE	Called DTE	Called DTE	 Calling DTE	Clearing DTE	Cleared DTE	
CSPDN	 X.20	Call Request	Incoming Call	Call Accepted	Ready for Data	DTE Clear Request	DCE Clear Indication	
	X.20 bis	108.1 ON (Note 3)	125 ON	108 ON	107 ON	108 OFF	107 OFF	
	X.21	Call Request	Incoming Call	Call Accepted	Ready for Data	DTE Clear Request	DCE Clear Indication	
	X.21 bis	108.1 ON (Note 3)	125 ON	108 ON	107 ON	108 OFF	107 OFF	
	X.22	See Recommendation X.21	
ISDN	I.420, I.421	FS	FS	FS	FS	FS	FS	
Packet Switched Data Transmission Service								
Network	Protocol(s)							
PSPDN	 X.25	Call request packet	Incoming call packet	Call accepted packet	Call connected packet	Clear request packet	Clear indication packet	
	X.32	Call request packet	Incoming call packet	Call accepted packet	Call connected packet	Clear request packet	Clear indication packet	
ISDN	 X.31	Call request packet	Incoming call packet	Call accepted packet	Call connected packet	Clear request packet	Clear indication packet	
Mobile Data Systems	 X.350/
X.352	Call request packet	Incoming call packet	Call accepted packet	Call connected packet	Clear request packet	Clear indication packet	
FS   For further study
Note 1 – For conveyance of the facility parameters, utilization of the Incoming Call Packet is mandatory. However, in order to speed up the decision by the called DTE whether or not to accept the call, optionally all facility parameters may be copied in the SETUP message.
Note 2 – The RELease or RELease COMplete messages can only be utilized for facility parameter conveyance if such message is issued in direct response to a SETUP message.
Note 3 – Only for direct call facilities.

TABLE I–2/X.301
Arrangements and facilities related to the transfer of addressing information
		Call Request Phase		Call Confirmation Phase		Call Clearing Phase		
Arrangement/Optional User Facility		Calling DTE	Called DTE	Called DTE	Calling DTE	Clearing DTE	Cleared DTE	
Transfer of X.121 Calling Address	* 
Note 1	*(=) Note 2					
Transfer of E.164 Calling Address	*
Note 1	*(=) Note 2					
Transfer of X.121 Called Address	 *	*(=) Note 2	* Notes 1, 3	 *(=)
Note 2	* Notes 1, 3	 *(=) Note 2	
Transfer of E.164 Called Address	 *	*(=) Note 2	* Notes 1, 3	 *(=)
Note 2	* Notes 1, 3	 *(=) Note 2	
Transfer of Calling NAE/Subaddress	 *	*(=)					
Transfer of Called NAE/Subaddress	 *	*(=)	* Note 3	 *(=)	* Note 3	 *(=)	
Note 1 – The address may be provided by the network.
Note 2 – The value may have been changed, e.g. due to the use of prefixes, country codes.
Note 3 – May only be needed in cases where the responding address is different from the originally called address.
TABLE I–3/X.301
Arrangements and optional user facilities related to the QOS of the call
		Call Request Phase		Call Confirmation Phase		Call Clearing Phase		
Arrangement/Optional User Facility		Calling DTE	Called DTE	Called DTE	Calling DTE	Clearing DTE	Cleared DTE	
Transit Delay Selection Indication	 *	 *(£ ³)		 *(£ ³)			
End–to–End Transit Delay Negotiation							
Cumulative Transit Delay	 *	 *(£)	 *	 *(=)			
Request End–to–End Delay	 *	 *(=)					
Maximum Acceptable Transit Delay	 *	 *(=)					
Throughput Class Negotiation	 *	 *(³)	 *	 *(=)			
Minimum Throughput Class	 *	 *(=)					
Note – Compared with the parameter value supplied in the Call Request Phase.
TABLE I–4/X.301
Arrangements and optional user facilities related to the charging conditions applying to the call
		Call Request Phase		Call Confirmation Phase		Call Clearing Phase		
Arrangement/Optional User Facility		Calling DTE	Called DTE	Called DTE	Calling DTE	Clearing DTE	Cleared DTE	
Reverse Charging	 B	 B(=)					
Charging Information	 B
Note		B
Note		*
Note	*
Note	
Note – Charging Information is an arrangement between DTE and Network only. The Request is made in the first message sent to the network. The response is provided in the first message from the network to the information requesting DTE in the Call Clearing Phase. In case that the information requesting DTE is also the clearing DTE, the requested information can only be conveyed if additional call clearing confirmation arrangement exist (e.g. in packet procedures the Clear Confirmation packet).
TABLE I–5/X.301
Arrangements and optional user facilities related to specific routing conditions requested by the user of the call
		Call Request Phase		Call Confirmation Phase		Call Clearing Phase		
Arrangement/Optional User Facility		Calling DTE	Called DTE	Called DTE	Calling DTE	Clearing DTE	Cleared DTE	
RPOA Selection	*						
Called Line Address			*	*(=)	*	*(=)	
Modified Notification					Note	Note	
Call Redirection or Deflection Notification		*					
Note – Only conveyed when the call clearing phase follows directly after the call request phase.

TABLE I–6/X.301
Arrangements and optional user facilities related to protection mechanisms requested by the user of the call
		Call Request Phase		Call Confirmation Phase		Call Clearing Phase		
Arrangement/Optional User Facility		Calling DTE	Called DTE	Called DTE	Calling DTE	Clearing DTE	Cleared DTE	
CUG Selection	 *	*(=)
Note					
CUG with Outgoing Access Selection	 *	*(=)
Note					
Bilateral CUG Selection	 *	*(=)
Note					
NUI	 *		*				
NUI Override Permission	 *						
Note – The value could have been changed due to international interworking.
TABLE I–7/X.301
Arrangements and optional user facilities to convey user data in addition
to the normal data flow in the data transfer phase
		Call Request Phase		Call Confirmation Phase		Call Clearing Phase		
Arrangement/Optional User Facility		Calling DTE	Called DTE	Called DTE	Calling DTE	Clearing DTE	Cleared DTE	
User Data conveyed in the Call Request Phase	*	*(=)					
User Data conveyed in the Call Confirmation Phase			*	*(=)			
User Data conveyed in the Call Clearing Phase					*	*(=)	
Fast Select							
– Restriction on Response	B	B(=)					
– No Restriction on Response	B	B(=)					

TABLE I–8/X.301
Other arrangements and optional user facilities

		Call Request Phase		Call Confirmation Phase		Call Clearing Phase		
Arrangement/Optional User Facility		Calling DTE	Called DTE	Called DTE	Calling DTE	Clearing DTE	Cleared DTE	
Receipt Confirmation Selection	 B	 B(£)	 B	 B(=)			
Expedited Data Negotiation	 B	 B(£)	 B	 B(=)			
APPENDIX II
(to Recommendation X.301)
Arrangements to support the OSI Network Service
	This appendix lists the arrangements and facilities described in this Recommendation that can be utilized to fully support the OSI Network Service as standardized in Recommendation X.213.
	(This is for further study)