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.\"                 Not Copyright ( c) 1991 
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.EN
.nr LL 40.5P
.nr ll 40.5P
.nr HM 3P
.nr FM 6P
.nr PO 4P
.nr PD 9p
.po 4P

.rs
\v | 5i'
.LP
.rs
.sp 47P
.ad r
\fBFigure 1/Q.764, (N), \*`a l'italienne, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 2/Q.764, (N), \*`a l'italienne, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 3/Q.764, (N), \*`a l'italienne, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
\fINotes referring to Figures 1/Q.764 to 3/Q.764\fR 
.LP
.sp 2
\fINote 1\fR \ \(em\ The alerting message may not be given by a called
terminal having automatic answer. Under these circumstances the Connect 
Message will be sent as soon as the Connect Message is received and through\(hyconnection 
of the speech path has been completed. 
.LP
\fINote 2\fR \ \(em\ For telephone calls within the ISDN, ringing tone will
be applied by the terminating exchange as soon as it is known that the
subscriber is free. In the case of a PABX connected to the access interface
there is the option of an early through\(hyconnection of the switchpath so that
the in\(hyband call arrival indication generated in the PABX is returned to the
calling user. For data calls, ringing tone is not applied.
.LP
\fINote 3\fR \ \(em\ The continuity check may be applicable on an
intermediate circuit if analogue circuits are used.
.LP
\fINote 4\fR \ \(em\ This example assumes that the number length is known at
the second transit exchange in order to illustrate the addition of SAMs 
to the IAM received. This function does not have to be performed in this 
way. 
.LP
\fINote 5\fR \ \(em\ The call may be rejected by the user at this point
following interchanges of user\(hyuser data, e.g.\ as a result of a failed
compatibility check.
.LP
\fINote 6\fR \ \(em\ Charging for the transfer of user\(hyuser data requires
further study.
.LP
\fINote 7\fR \ \(em\ Flow control of user\(hyuser data is achieved by the
originating and destination exchanges by the use of \*Qreceive ready\*U and
\*Qreceive not ready\*U messages throughout the conversation/data phase.
.LP
\fINote 8\fR \ \(em\ Access protocol example is for point\(hyto\(hypoint 
operation 
only.
.LP
.rs
.sp 29P
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 4/Q.764, (N), \*`a l'italienne, p. 4\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 5/Q.764, (N), \*`a l'italienne, p. 5\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 6/Q.764, (N), \*`a l'italienne, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 7/Q.764, (N), \*`a l'italienne, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 8/Q.764, (N), \*`a l'italienne, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 9/Q.764, (N), \*`a l'italienne, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 10/Q.764, (N), \*`a l'italienne, p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB3\fR 	\fBEnd\(hyto\(hyend signalling\fR 
.sp 1P
.RT
.sp 1P
.LP
3.1
	\fIIntroduction\fR 
.sp 9p
.RT
.PP
End\(hyto\(hyend messages contain only information which is relevant for 
the \*Qendpoints\*U of a circuit\(hyswitched connection. Endpoints are 
signalling 
points such as local exchanges and possibly exchanges at network boundaries,
e.g.\ international gateway exchanges within the Signalling System No.\ 7
network.
.PP
Two methods are available for ISDN end\(hyto\(hyend signalling:
.RT
.LP
	\(em
	the pass\(hyalong method; and
.LP
	\(em
	the signalling connection control part (SCCP) method.
.PP
The choice of method is, to some extent, dependent on the size and architecture 
of the signalling network. Both methods may coexist in a given 
network.
.PP
The pass\(hyalong method and the SCCP method are specified for
circuit\(hyswitched connections.
.PP
An end\(hyto\(hyend signalling connection established for end\(hyto\(hyend
signalling is called an \*QISDN user part end\(hyto\(hyend signalling connection\*U 
in 
this section.
.PP
\(sc\ 1.5 discusses the use of the end\(hyto\(hyend and link\(hyby\(hylink
methods.
.RT
.sp 1P
.LP
3.2
	\fIPass\(hyalong method\fR 
.sp 9p
.RT
.PP
In the pass\(hyalong method, use is made of an ISDN user part
end\(hyto\(hyend signalling connection which in fact is being set up whenever a
physical connection between two endpoints is established.
.PP
The ISDN user part end\(hyto\(hyend signalling connection in this case
consists of a number of connection sections in tandem which run in parallel
with and use the same identification code as the circuits in the physical
connection.
.PP
The association of incoming and outgoing circuits in a transit
exchange also establishes the coupling of the connection sections related to
these circuits.
.PP
The pass\(hyalong method defines, section by section, the appropriate
routing label for the message to be passed along via ISDN user part connection; 
but the content of pass\(hyalong messages is only evaluated and possibly 
changed at the endpoints. The pass\(hyalong message group is characterised 
by a special 
message type code as specified in Recommendation\ Q.763. One ISDN user part
message to be passed along may be embedded in one pass\(hyalong message.
.PP
In a signalling connection for which pass\(hyalong method is available
pass\(hyalong messages may be sent in either the forward or backward direction.
.PP
A forward pass\(hyalong message may not be sent until either a backward 
pass\(hyalong or the first backward set\(hyup message has been received 
or after the physical connection is released. 
.PP
Call control path information (see \(sc\ 3.5) included in the initial
address and backward set\(hyup messages is used to indicate to the connection
endpoints whether or not the call control path can support pass\(hyalong 
message transfer. 
.PP
A pass\(hyalong message that has been received at a transit exchange and 
cannot be transferred to the subsequent exchange is discarded without affecting 
call states and timers in that exchange. 
.RT
.sp 1P
.LP
3.3
	\fISCCP method\fR 
.sp 9p
.RT
.PP
In the SCCP method the ISDN user part employs the services of the signalling 
connection control part (SCCP) for the transfer of end\(hyto\(hyend 
signalling information.
.RT
.sp 1P
.LP
3.3.1
	\fICall reference\fR 
.sp 9p
.RT
.PP
The call reference is a circuit independent information identifying a particular 
call. It is needed when end\(hyto\(hyend signalling information 
associated with the call is to be transferred by a connectionless SCCP 
service. If, in turn, an SCCP connection request for connection\(hyoriented 
SCCP service is carried embedded in an ISDN\(hyUP message, the call reference 
is 
omitted.
.bp
.PP
References for a given call are allocated independently in the two
concerned signalling points and are subsequently exchanged. The allocation 
of call references may be initiated by either side. The call reference 
consists of a call identity and the point code where the call identity 
is established. If, e.g.\ signalling point\ A initiates the exchange of 
call references, it selects a call identity CIA and transfers it together 
with the point code of A, PCA, to signalling point\ B. Signalling point\ 
B then allocates its own identity CIB to the call and returns it together 
with the signalling point code of\ B, PCB, to signalling point\ A. Subsequent 
call related end\(hyto\(hyend message transferred from signalling point\ 
A to signalling point\ B contain call identity CIB and are 
routed directly using destination point code PCB. Conversely, end\(hyto\(hyend
messages transferred from signalling point\ B to signalling point\ A contain 
call identity CIA and are routed using destination point code PCA. 
.PP
A linkage of call references at network boundaries has to be
provided.
.RT
.sp 1P
.LP
3.3.2
	\fICoupling of connection sections\fR 
.sp 9p
.RT
.PP
An ISDN user part end\(hyto\(hyend signalling connection may consist of 
a number of connection sections in tandem. In order to couple two connection 
sections at the SCCP relay point, linkage of call references\ 3 (Ref\ 3) is
performed by ISDN user part for connectionless SCCP service and linkage of
local references is performed by SCCP for connection\(hyoriented SCCP service.
.PP
An SCCP relay point where linkage of call references is performed by the 
ISDN user part is called an \*Qintermediate relay node\*U in this 
section.
.RT
.sp 1P
.LP
3.3.3
	\fIConnectionless service\fR 
.sp 9p
.RT
.PP
For connectionless service, the ISDN user part transfers the data to be 
transmitted to the SCCP together with a request for the appropriate 
protocol class of service. The Ref\ 3 signalling information, transfer and
delivery of this data to the distant ISDN user part is controlled entirely 
by the SCCP. The association between the transferred information and a 
call is 
made by the ISDN user part, which transfers the call reference as part of
signalling information for this purpose.
.PP
The protocol class of service is assumed to be\ 0. Individual networks 
may choose class\ 1 based on the predetermined arrangement. 
.RT
.sp 2P
.LP
3.3.4
	\fIConnection\(hyoriented service\fR 
.sp 1P
.RT
.sp 1P
.LP
3.3.4.1
	\fIConnection request embedded in an ISDN user part message\fR 
.sp 9p
.RT
.PP
At the exchange initiating the establishment of an ISDN user part end\(hyto\(hyend 
signalling connection based on connection\(hyoriented SCCP service, the 
ISDN user part requests the SCCP to provide the necessary information for 
a 
connection request for an SCCP end\(hyto\(hyend connection. This connection 
request is then carried embedded in an ISDN user part message. At the destination 
exchange the connection request is passed to the SCCP by the ISDN user part.
The SCCP at the destination exchange then behaves as if the connection 
request had been sent directly by the SCCP from the originating exchange: 
it indicates the connection request to the ISDN user part and upon response 
from the ISDN 
user part it returns a connection confirm message to the SCCP at the
originating exchange. The SCCP at the originating exchange confirms the 
set\(hyup of the end\(hyto\(hyend connection to the ISDN user part. The 
contents in the 
embedded connection request is not evaluated by the ISDN user part at any
exchange.
.RT
.sp 1P
.LP
3.3.4.2
	\fIProtocol class of service\fR 
.sp 9p
.RT
.PP
The protocol class of service is assumed to be\ 2. If the connection request 
is of protocol class\ 3, the ISDN user part connection request parameter 
must include explicit protocol class and credit indications in addition 
to the SCCP source local reference. 
.RT
.sp 1P
.LP
3.3.4.3
	\fIMechanism of coupling\fR 
.sp 9p
.RT
.PP
Although coupling of connection sections may not be appropriate in combination 
with the embedded method, coupling is necessary at network 
boundaries. In this case the ISDN user part at the intermediate point has
knowledge that a coupling of end\(hyto\(hyend connections sections has to be
performed, and therefore connection requests received embedded in an ISDN 
user part message are passed to the SCCP. The SCCP, in turn, furnishes 
the ISDN user part with a connection request for the new connection section 
in order to have it included in the outgoing ISDN user part message. 
.bp
.PP
After the coupling of the connection sections has been successfully
initiated by the ISDN user part, end\(hyto\(hyend signalling information 
passing 
through an intermediate point is not passed to the ISDN user part.
.RT
.sp 1P
.LP
3.3.4.4
	\fIRelease of ISDN user part end\(hyto\(hyend signalling connection\fR 
.sp 9p
.RT
.PP
The SCCP end\(hyto\(hyend connection is released according to the
procedures described in the Recommendation\ Q.714.
.PP
The physical connection and the ISDN user part end\(hyto\(hyend signalling 
connection can be released independently of each other. 
.PP
Generally, both the ISDN user part end\(hyto\(hyend signalling connection
and the physical connection are released simultaneously. However, for certain 
applications it is possible to maintain the SCCP end\(hyto\(hyend connection 
although the physical connection has already been released. 
.RT
.sp 1P
.LP
3.4
	\fIChaining of ISDN user part end\(hyto\(hyend signalling connections\fR 
.sp 9p
.RT
.PP
At an exchange where the contents of end\(hyto\(hyend signalling
information may need to be evaluated by the ISDN user part, ISDN user part
end\(hyto\(hyend signalling connections are chained. Chaining of two ISDN 
user part end\(hyto\(hyend signalling connections means that one ISUP signalling 
connection 
terminates and another ISUP signalling connection associated with it originates 
with all end\(hyto\(hyend signalling information passing through the ISDN 
user part. The new ISUP signalling connection may have different characteristics 
from the previous one. See Figure\ 22/Q.764. 
.PP
If chaining is not appropriate for the associated call when the
service requirements cannot be satisfied because of it, the call may be
released. In addition, if any of the ISDN user part end\(hyto\(hyend signalling
connections under chaining cannot be established or is abnormally disconnected 
the associated call may be released if the required service cannot be completed 
without it. 
.RT
.sp 1P
.LP
3.5
	\fIUse of the Protocol Control Indicator (PCI)\fR 
.sp 9p
.RT
.PP
The protocol control indicator is control information concerning
the end\(hyto\(hyend signalling procedures. It is contained in the forward call
indicator and the backward call indicator, respectively, and has to be 
examined to determine which end\(hyto\(hyend signalling method should be 
used if any (when an embedded connection request is not included in the 
appropriate message) for the end\(hyto\(hyend transfer of messages. 
.PP
The following indications are provided:
.RT
.LP
	a)
	 available information that could be transmitted (end\(hyto\(hyend) to 
the other endpoint; 
.LP
	b)
	 Signalling System No.\ 7 path between the two endpoints, no interworking 
along the route; 
.LP
	c)
	pass\(hyalong method available;
.LP
	d)
	SCCP connection\(hyoriented class available;
.LP
	e)
	SCCP connectionless class available;
.LP
	f
)
	ISDN user part used all the way.
.sp 1P
.LP
3.6
	\fIOperation of the pass\(hyalong method\fR 
.sp 9p
.RT
.PP
Figure 11/Q.764 illustrates the operation of the pass\(hyalong
protocol. In this Figure the PCI is the protocol control indicator in the 
IAM. \*QInterworking\*U in the IAM or ACM indicates that the control path 
is not wholly Signalling System\ No.\ 7. 
.bp
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure 11/Q.764, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
3.7
	\fIOperation of the SCCP method \(hy connectionless services\fR 
.sp 1P
.RT
.sp 2P
.LP
3.7.1
	 \fISuccessful set\(hyup of the ISDN user part end\(hyto\(hyend signalling\fR 
\fIconnection\fR 
.sp 1P
.RT
.sp 1P
.LP
3.7.1.1
	\fISimultaneous establishment of an ISDN user part end\(hyto\(hyend\fR 
\fIsignalling connection and a physical connection\fR 
.sp 9p
.RT
.PP
In the case of simultaneous establishment of a signalling
connection with a physical connection, the initial address message from the
originating exchange of a call contains the call reference consisting of the
point code of the originating exchange and the call identity. The inclusion 
of the call reference implicitly indicates that the establishment of a 
signalling connection is requested. When the terminating exchange receives 
an IAM with a call reference in it and a signalling connection can be established, 
it 
responds to that with its own call reference included in the first backward
message (e.g.\ an address complete message).
.PP
At an intermediate relay node where SCCP is terminated, its own call reference 
is allocated to the signalling connection and the coupling of call 
references is made. When the first backward message contains a call reference, 
an intermediate relay node replaces that with its own call reference and 
relays this message towards the originating exchange. 
.PP
When the originating exchange receives the destination call reference from 
the exchange at the other end of the connection section the signalling 
connection is regarded as in a ready state and end\(hyto\(hyend signalling
information can be transferred over this connection.
.PP
Figure 12/Q.764 shows the procedure for this case.
.RT
.LP
.rs
.sp 20P
.ad r
\fBFigure 12/Q.764, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.7.1.2
	\fIEstablishment of a signalling connection when the\fR 
\fIcircuit\(hyassociated signalling path has been established\fR 
.sp 9p
.RT
.PP
When the circuit\(hyassociated signalling path has already been
established, the establishment of a signalling connection can be initiated
either by the originating or the terminating exchange of a call. In this 
case, an Information Request message (INR) is transferred from the initiating 
exchange to the other end. This INR message contains a call reference as 
in the case of an IAM as described in \(sc\ 3.6.1.1 above. 
.bp
.PP
An information message (INF) containing a call reference as in the case 
of the first backward message in \(sc\ 3.6.1.2 is returned to the initiating 
exchange and a signalling connection is successfully established. 
.PP
Figure 13/Q.764 shows the procedure for this case.
.RT
.LP
.rs
.sp 20P
.ad r
\fBFigure 13/Q.764, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.7.2
	\fIUnsuccessful set\(hyup of a signalling connection\fR 
.sp 9p
.RT
.PP
In a case where a signalling connection cannot be established,
e.g.\ due to interworking with a PSTN, the first backward message in response 
to the initial address message containing the originating call reference 
includes no call reference. 
.PP
The procedure for this case is shown in Figure\ 14/Q.764.
.RT
.LP
.rs
.sp 19P
.ad r
\fBFigure 14/Q.764, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
In a case where the establishment for a signalling connection is requested 
by an INR message as shown in Figure\ 13/Q.764 the initiating exchange 
usually knows the end\(hyto\(hyend signalling capability for the call concerned 
and a signalling connection can successfully be established. However, if 
a signalling connection cannot be established for some reason, an INF message 
containing no call reference is returned to the initiating exchange. 
.PP
In these situations, the call may be released if the ISDN user part
end\(hyto\(hyend signalling connection is essential to satisfy the service
requirements of the call.
.PP
In these cases, the call reference(s) is frozen for the time
(T\d3\\d1\u) as described in \(sc\ 3.7.4.
.RT
.sp 1P
.LP
3.7.3
	\fIAbnormal situations\fR 
.sp 9p
.RT
.PP
If no response to the INR message containing the originating call reference 
is received for the time T\d3\\d3\uat the initiating exchange and if necessary 
(e.g.\ in the case of an interworking exchange of different end\(hyto\(hyend 
signalling schemes) at an intermediate relay node, the call is released 
(see 
\(sc\ 2.9.7).
.PP
In this case, the call reference(s) is frozen for the time T\d3\\d1\uas 
described in \(sc\ 3.7.4. 
.PP
The procedure for this case is shown in Figure\ 15/Q.764.
.RT
.LP
.rs
.sp 21P
.ad r
\fBFigure 15/Q.764, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
3.7.4
	\fIRelease of a signalling connection\fR 
.sp 1P
.RT
.sp 1P
.LP
3.7.4.1
	 \fISimultaneous release of a physical connection and a signalling\fR 
\fIconnection\fR 
.sp 9p
.RT
.PP
When the call is released, the ISDN user part end\(hyto\(hyend signalling 
connection is considered to be released simultaneously. Call references 
allocated at local exchanges and intermediate relay node(s) are frozen 
for time T\d3\\d1\uas described in \(sc\ 3.7.4.2 below. 
.PP
The procedure for this case is shown in Figure\ 16/Q.764.
.bp
.RT
.LP
.rs
.sp 18P
.ad r
\fBFigure 16/Q.764, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.7.4.2
	\fIFrozen call reference\fR 
.sp 9p
.RT
.PP
When an ISDN user part end\(hyto\(hyend signalling connection is
released, call references allocated for this signalling connection are 
frozen for time T\d3\\d1\u. These references will not be used for another 
signalling 
connection during the frozen period. T\d3\\d1\uis chosen to sufficiently 
reduce the probability of erroneously associating a message with the previously 
used call reference. Optionally call identities may be allocated to individual 
signalling connections in a cyclic manner so that a previously used call
identity is not to be used again for sufficient amount of time.
.PP
If an end\(hyto\(hyend message containing a frozen call reference is
received, it is discarded.
.RT
.sp 1P
.LP
3.7.5
	\fIEnd\(hyto\(hyend message transfer\fR 
.sp 9p
.RT
.PP
An end\(hyto\(hyend message is transferred in an SCCP unitdata (UDT)
message according to the procedures defined in Recommendation\ Q.714. ISDN 
user part interfaces with SCCP via the primitives are defined in 
Recommendation\ Q.711
for this transfer. The unit\(hydata request/indication primitive includes 
in its user data parameter an ISDN user part message beginning with the 
message type and ending with the parameters. 
.PP
At the local exchange which has responded to the request of
establishment of an ISDN user part end\(hyto\(hyend signalling connection 
from the 
other local exchange,
an end\(hyto\(hyend message cannot be transferred for time T\d3\\d2\uor
until the first end\(hyto\(hyend message has been received from the other end.
T\d3\\d2\uis chosen to sufficiently reduce the probability that an end\(hyto\(hyend 
message from the responding local exchange is received at the initiating 
local exchange or the intermediate relay node, before the ISDN user part 
message 
which contains the response to the signalling connection establishment
request.
.PP
If a relay exchange receives an end\(hyto\(hyend message in a UDT, in any
case the UDT will be forwarded to the succeeding exchange if possible.
.PP
The procedure for this case is shown in Figure\ 17/Q.764.
.bp
.RT
.LP
.rs
.sp 19P
.ad r
\fBFigure 17/Q.764, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.8
	\fIOperation of the\fR 
\fISCCP method\fR \fI\(em connection\(hyoriented\fR 
\fIservice\fR 
.sp 9p
.RT
.PP
The initial address message, the facility request message and the information 
message may be used for the embedded transfer of the connection 
request. The procedures described and the figures refer to the case where 
the connection request is sent in the forward direction. In principle, 
they also 
apply when the connection request is sent in the backward direction in the
facility request or the information message.
.PP
For the connection request embedded in an ISDN user part message an
additional interface is used. This functional interface is described in
Recommendations\ Q.711 and\ Q.714 (signalling connection control part of
Signalling System No.\ 7). The interface elements are listed in
\(sc\ 3.9.
.PP
Procedures concerning the SCCP are in accordance with those described in 
Recommendation\ Q.714 (signalling connection control part of Signalling 
System No.\ 7) and are described here only for illustrative
purposes.
.RT
.sp 1P
.LP
3.8.1
	\fISuccessful set\(hyup of the ISDN user part end\(hyto\(hyend signalling\fR 
\fIconnection\fR 
.sp 9p
.RT
.PP
The following actions are performed at the originating exchange and at 
the destination exchange for the set up of an SCCP end\(hyto\(hyend connection 
using embedded transfer of the connection request in an ISDN user part 
message (the numbers in the text correspond to the numbers in 
Figure\ 18/Q.764):
.RT
.LP
	1)
	The ISDN user part (ISUP) at the originating exchange
requests the SCCP to provide the necessary information for a connection 
request to the called address using the REQUEST type\ 1 interface element. 
.LP
	2)
	 The SCCP at the originating exchange generates a connection request and 
transfers it to the ISDN user part using the REPLY interface 
element.
.LP
	3)
	 The ISDN user part at the originating exchange transmits the connection 
request embedded in an ISDN user part message to the ISDN user part at 
the destination exchange. 
.LP
	7)
	Upon receiving an embedded connection request in an ISDN
user part message, the ISDN user part at the destination exchange transfers 
the received connection request to the SCCP using the REQUEST type\ 2 interface 
element.
.LP
	8)
	 The SCCP at the destination exchange informs the ISDN user part of a 
request to establish an end\(hyto\(hyend connection using the N\(hyCONNECT 
indication primitive.
.bp
.LP
	9)
	The ISDN user part responds to the request using the
N\(hyCONNECT response primitive.
.LP
	10)
	Upon receiving the N\(hyCONNECT response primitive from the
ISDN user part, the SCCP at the destination exchange sends a connection 
confirm message into the backward direction. 
.LP
	12)
	 Upon receiving a connection confirm message the SCCP at the originating 
exchange informs the ISDN user part using the N\(hyCONNECT 
confirmation primitive.
.PP
At those transit exchanges which are not SCCP relay\(hypoints, the
connection request embedded in an ISDN user part message is left unchanged 
by the ISDN user part and transferred into the forward direction. 
.PP
An SCCP relay\(hypoint is an exchange where two connection sections
belonging to the same end\(hyto\(hyend connection are coupled.
.PP
The following actions are performed at an SCCP relay\(hypoint for the
coupling of two connection sections (the numbers in the text correspond 
to the numbers in Figure\ 18/Q.764): 
.RT
.LP
	4)
	Upon receiving an embedded connection request in an ISDN
user part (ISUP) message, the ISDN user part at the SCCP relay\(hypoint 
transfers the received connection request to the SCCP using the REQUEST 
type\ 2 interface element with the reply request set. 
.LP
	5)
	The reply request in the REQUEST type 2 interface element
causes the SCCP at the SCCP relay\(hypoint to provide a connection request 
for a new connection section. The new connection request is provided to 
the ISDN user part using the REPLY interface element. 
.LP
	\fINote\fR \ \(em\ The SCCP allocates an outgoing local reference
and associates the incoming and outgoing local references and their
corresponding point codes.
.LP
	6)
	The ISDN user part at the SCCP relay\(hypoint transmits the
connection request embedded in an ISDN user part message.
.LP
	11)
	Upon receiving a connection confirm message, the SCCP at
the SCCP relay\(hypoint sends a connection confirm message into the backward
direction.
.LP
.rs
.sp 30P
.ad r
\fBFigure 18/Q.764, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.8.2
	\fIUnsuccessful set\(hyup of the SCCP end\(hyto\(hyend connection\fR 
.sp 9p
.RT
.PP
If the ISDN user part end\(hyto\(hyend signalling connection cannot be
extended beyond a transit exchange because (for instance) interworking 
occurs, the ISDN user part at this transit exchange initiates the refusal 
of the 
connection request which is then performed by the SCCP. The set\(hyup of the
physical connection may be continued.
.PP
If the ISDN user part initiates the refusal of a connection request
received embedded in the initial address message, in general the following
actions are performed. The numbers in the text correspond to the numbers in
Figure\ 19/Q.764:
.RT
.LP
	1)
	Upon receiving an embedded connection request, the ISDN user
part transfers the received connection request to the SCCP
using the REQUEST type\ 2 interface element with the refusal
indicator set.
.LP
	2)
	Upon receiving the REQUEST type\ 2 interface element with the
refusal indicator set, the SCCP sends a connection refused
message (CREF) into the backward direction.
.LP
	3)
	Upon receiving a connection refused message, the SCCP at the
originating exchange informs the ISDN user part using the
N\(hyDISCONNECT indication primitive.
.PP
If the SCCP at an SCCP relay\(hypoint receives a connection refused message 
instead of a connection confirm message, the incoming connection 
section is also released by sending a connection refused message into the
backward direction.
.PP
If the SCCP at the destination exchange fails to set up the requested end\(hyto\(hyend 
connection, the following actions are performed to refuse the 
connection request received in a REQUEST type\ 2 interface element (the 
numbers in the text correspond to the numbers in Figure\ 20/Q.764): 
.RT
.LP
	1)
	 The SCCP at the destination exchange sends an N\(hyDISCONNECT indication 
primitive to the ISDN user part. 
.LP
	2)
	 At the same time the SCCP sends a connection refused message into the 
backward direction. 
.PP
In these situations, the call may be released if the ISDN user
part end\(hyto\(hyend signalling connection is essential to satisfy the service
requirements of the call.
.LP
.rs
.sp 22P
.ad r
\fBFigure 19/Q.764, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 21P
.ad r
\fBFigure 20/Q.764, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.8.3
	\fIUnsuccessful set\(hyup of the physical connection\fR 
.sp 9p
.RT
.PP
If the physical connection cannot be set up at a transit exchange, in addition 
to releasing the physical connection so far established the ISDN 
user part initiates the refusal of the connection request. The same actions 
are performed as at a transit exchange beyond which a logical connection 
cannot be extended. 
.PP
If the physical connection cannot be set up at the destination
exchange, the ISDN user part can initiate either the refusal or the
confirmation of the connection request depending on supplementary services. 
It may be preferred to always confirm the connection request to allow for 
the 
initiation of supplementary services by the calling subscriber.
.RT
.sp 2P
.LP
3.8.4
	\fIRelease of the ISDN user part (ISUP) end\(hyto\(hyend signalling\fR 
\fIconnection\fR 
.sp 1P
.RT
.sp 1P
.LP
3.8.4.1
	\fISimultaneous release of the physical and ISUP signalling\fR 
\fIconnections\fR 
.sp 9p
.RT
.PP
The release of the ISDN user part end\(hyto\(hyend signalling connection 
is initiated from the exchange which initiates the release of the call 
concerned. At the initiating exchange of call release, when the ISDN user 
part release message (REL) is transmitted, ISDN user part requests SCCP 
to transmit a released message (RLSD). This RLSD message contains a cause 
value of \*Qend 
user originated\*U in its cause parameter, if a normal call release initiated 
by a user is taking place. 
.PP
Figure 21/Q.764 shows the procedure for this case.
.PP
In the case where no application requires the ISDN user part
end\(hyto\(hyend signalling connection to be maintained, the ISDN user 
part at a 
local exchange, or an exchange performing chaining, requests the SCCP to
release the SCCP end\(hyto\(hyend connection if it receives a release message 
(REL) and the SCCP has not yet received a released (RLSD) message at that 
time (see Figure\ 22/Q.764). 
.bp
.RT
.LP
.rs
.sp 19P
.ad r
\fBFigure 21/Q.764, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 32P
.ad r
\fBFigure 22/Q.764, (N), p.\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.8.4.2
	\fINon\(hysimultaneous release of the physical and the ISDN user\fR 
\fIpart end\(hyto\(hyend signalling connections\fR 
.sp 9p
.RT
.PP
Procedures for non\(hysimultaneous release of the physical and the
ISDN user part end\(hyto\(hyend signalling connections are to be defined in
appropriate supplementary services procedures.
.RT
.sp 1P
.LP
3.8.5
	\fIEnd\(hyto\(hyend message transfer\fR 
.sp 9p
.RT
.PP
An end\(hyto\(hyend message is transferred in an SCCP data (DT1/DT2)
message according to the procedures defined in Recommendation\ Q.714. ISDN 
user part interfaces with SCCP via the primitives as defined in Recommendation\ 
Q.711 for this transfer. The data request/indication primitive includes 
in its user data parameter an ISDN user part message beginning with the 
message type code and ending with the parameters. 
.RT
.sp 1P
.LP
3.9
	\fIInterface elements between ISDN user part and SCCP\fR 
\fI(embedded transfer)\fR 
.sp 9p
.RT
.PP
The ISDN user part may use the functional interface as defined in Recommendation\ 
Q.711. 
.PP
Three interface elements are defined for this functional
interface:
.RT
.LP
	a)
	the REQUEST type 1
.LP
	b)
	the REQUEST type 2
.LP
	c)
	the REPLY
.PP
The contents of these three interface elements are shown in
Appendix\ I.
.PP
Figures 18/Q.764, 19/Q.764 and 21/Q.764 indicate the usage of the
interface elements during set up of a circuit\(hyswitched connection together 
with an SCCP connection. 
.RT
.LP
.rs
.sp 25P
.LP
.bp
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation Q.764)
.sp 9p
.RT
.ce 0
.ce
\fBH.T. [1T3.764]\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(300p) .
 {
\fBTimers used in Recommendation Q.764\fR
(Sheet 1 of 6)
 }
.TE
.TS
center box ;
cw(24p) | cw(36p) | cw(36p) | cw(54p) | cw(48p) | cw(54p) | cw(48p) .
Symbol	Time\(hyout value	Significance	Cause for initiation	Normal termination	At the first expiry	At the following expiry
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 1	4\(hy15 s	Local	When release message is sent	 {
At the receipt of release complete message
 }	 {
Retransmit release message and reinitialize timer T
1
 }	Same as the first expiry
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 2	3 min	Dual	 {
When controlling exchange receives suspend (user) message
 }	 {
At the receipt of resume (user) message at controlling exchange
 }	Initiate release procedure	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 3	3 min	Dual	 {
When local exchange sends delayed release message
 }	 {
When hold condition is removed
 }	Initiate release procedure	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 4	4\(hy15 s	Dual	 {
When local exchange sends call modification request message
 }	 {
At the reception call modification complete message
 }		\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 5\fB\fR\(da\fB0\fR	1 min	Local	 {
When initial release message is sent
 }	 {
At receipt of release complete message
 }	 {
Send reset circuit message, alert maintenance personnel, and remove
the circuit from service
 }	 {
The sending of the de reset circuit message should continue at 1\(hymin
intervals until maintenance intervention occurs
 }
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 6\fB\fR\(da\fB0\fR	Covered in Q.118	Dual	 {
When controlling exchange receives suspend (network)
 }	 {
At the receipt of resume (network) message
 }	Initiate release procedure	\(em
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau [1T3.764],\ \ \ A L'ITALIENNE, p. 23\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [2T3.764]\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(300p) .
 {
\fBTimers used in Recommendation Q.764\fR
(Sheet 2 of 6)
 }
.TE
.TS
center box ;
cw(24p) | cw(36p) | cw(36p) | cw(54p) | cw(48p) | cw(54p) | cw(48p) .
Symbol	Time\(hyout value	Significance	Cause for initiation	Normal termination	At the first expiry	At the following expiry
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 7\fB\fR\(da\fB0\fR	20\(hy30 s	Dual	 {
When the latest address message is sent
 }	 {
When the condition for normal release of address and routing informations
is met (receipt of ACM, CON, messages)
 }	 {
Release all equipment and connection (Send release message)
 }	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 8\fB\fR\(da\fB0\fR	10\(hy15 s	Local	 {
When transit of incoming international exchange receives initial
adress message
 }	 {
At receipt of continuity message
 }	 {
Release all equipment and connection into national network
(Send release message)
 }	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 9\fB\fR\(da\fB0\fR	Interval specified in Q.118	Dual	 {
When national controlling or outgoing international exchange sends latest
address message after the receipt of ACM
 }	At the receipt of answer	 {
Release connection send back release message
 }	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 1 0	4\(hy6 s	Dual	 {
When last digit is received in interworking situations
 }	 {
At the receipt of fresh information
 }	Send address complete message	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 1 1	15\(hy20 s	Dual	 {
When latest address message is received in interworking situations
 }	Send ACM	Send address complete message	\(em
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau [2T3.764],\ \ \ A L'ITALIENNE, p. 24\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [3T3.764]\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(300p) .
 {
\fBTimers used in Recommendation Q.764\fR
(Sheet 3 of 6)
 }
.TE
.TS
center box ;
cw(24p) | cw(36p) | cw(36p) | cw(54p) | cw(48p) | cw(54p) | cw(48p) .
Symbol	Time\(hyout value	Significance	Cause for initiation	Normal termination	At the first expiry	At the following expiry
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 1 2	4\(hy15 s	Local	When blocking message is sent	 {
At receipt of blocking acknowledgement
 }	 {
Retransmit blocking message and initiate T
1
2
 }	 {
Same as the left until T
1
3 expires
 }
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 1 3	1 min	Local	 {
When initial blocking message is sent
 }	 {
At receipt of blocking acknowledgement
 }	 {
Retransmit blocking message and alert maintenance personnel and start
T
1
3. Stop T
1
2
 }	 {
The reception of message should be continued until maintenance
intervention occurs and circuit taken out of service as
appropriate
 }
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 1 4	4\(hy15 s	Local	 {
When unblocking message is sent
 }	 {
At receipt of unblocking acknowledgement
 }	 {
Retransmit unblocking message and initiate T
1
4 timer
 }	 {
Same as the left until T
1
5 expires
 }
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 1 5	1 min	Local	 {
When initial unblocking message is sent
 }	 {
At receipt of unblocking acknowledgement
 }	 {
Retransmit unblocking message alert maintenance personnel, start
T
1
5 timer and stop T
1
4
 }	 {
The repetition of message should be continued until maintenance
intervention occurs and circuit taken out of service as
appropriate
 }
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 1 6	4\(hy15 s	Local	 {
When reset circuit message is sent
 }	 {
At the receipt of the acknowledgement (RLC message)
 }	 {
Retransmit reset circuit message and restart T
1
6
 }	 {
Same as the left until T
1
7 expires
 }
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 1 7	1 min	Local	 {
When initial reset circuit message is sent
 }	 {
At receipt of the acknowledgement
 }	 {
Alert maintenance personnel retransmit reset circuit message,
restart T
1
7 and stop T
1
6
 }	 {
The repetition of message should be continued until maintenance
intervention occurs
 }
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau [3T3.764],\ \ \ A L'ITALIENNE, p. 25\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [4T3.764]\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(342p) .
 {
\fBTimers used in Recommendation Q.764\fR
(Sheet 4 of 6)
 }
.TE
.TS
center box ;
cw(24p) | cw(36p) | cw(36p) | cw(54p) | cw(48p) | cw(54p) | cw(48p) .
Symbol	Time\(hyout value	Significance	Cause for initiation	Normal termination	At the first expiry	At the following expiry
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 1 8	4\(hy15 s	Local	 {
When group blocking message is sent
 }	 {
At receipt of group blocking acknowledgement
 }	 {
Retransmit group blocking message and initiate T
1
8
 }	 {
Same as the left until T
1
8 expires
 }
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 1 9	1 min	Local	 {
When initial group blocking message is sent
 }	 {
At receipt of group blocking acknowledgement
 }	 {
Retransmit group blocking message, alert maintenance personnel,
initiate T
1
9 and stop T
1
8
 }	 {
The repetition of message should be continued until maintenance
intervention occurs and circuits taken out of service as
appropriate
 }
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 2 0	4\(hy15 s	Local	 {
When group unblocking message is sent
 }	 {
At receipt of group unblocking acknowledgement
 }	 {
Retransmit group unblocking message and initiate T
2
0
 }	 {
Same as the left until T
2
0 expires
 }
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 2 1	1 min	Local	 {
When initial group unblocking message is sent
 }	 {
At receipt of group unblocking acknowledgement
 }	 {
Retransmit group unblocking message, alert maintenance personnel,
initiate T
2
1 and stop T
2
0
 }	 {
The repetition of message should be continued until maintenance
intervention occurs and circuits taken out of service as
appropriate
 }
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 2 2	4\(hy15 s	Local	 {
When circuit group reset message is sent
 }	 {
At the receipt of the acknowledgement
 }	 {
Retransmit circuit group reset message and restart T
2
2
 }	 {
Same as the first expiry until T
2
3 expires
 }
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau [4T3.764],\ \ \ A L'ITALIENNE, p. 26\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [5T3.764]\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(300p) .
 {
\fBTimers used in Recommendation Q.764\fR
(Sheet 5 of 6)
 }
.TE
.TS
center box ;
cw(24p) | cw(36p) | cw(36p) | cw(54p) | cw(48p) | cw(54p) | cw(48p) .
Symbol	Time\(hyout value	Significance	Cause for initiation	Normal termination	At the first expiry	At the following expiry
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | lw(48p) .
T 2 3	1 min	Local	 {
When initial circuit group reset message is sent
 }	 {
At the receipt of the acknowledgement
 }	 {
Alert maintenance personnel and restart Timer T
2
3.
Retransmit circuit group reset message. Stop timer T
2
2
 }	 {
The reception of message should be continued until maintenance
intervention occurs
 }
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 2 4	< 2 s	Local	When check tone is sent	 {
At the receipt of backward check tone
 }	Report failure	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | cw(48p) | lw(54p) | cw(48p) .
T 2 5	1\(hy10 s	Local	 {
When continuity check failure is detected (on receipt of
continuity recheck request)
 }	\(em	Send CCR message	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | cw(48p) | lw(54p) | cw(48p) .
T 2 6	1\(hy3 min	Local	 {
When second continuity check failure is detected
 }	\(em	Send CCR message	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 2 7	4 min	Local	 {
When continuity recheck request is requested
 }	 {
At receipt of continuity check request message
 }	Return to idle	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 2 8	10 s	Local	When send CQM	At receipt of CQR	Alert maintenance	\(em
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau [5T3.764],\ \ \ A L'ITALIENNE, p. 27\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [6T3.764]\fR 
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(300p) .
 {
\fBTimers used in Recommendation Q.764\fR
(Sheet 6 of 6)
 }
.TE
.TS
center box ;
cw(24p) | cw(36p) | cw(36p) | cw(54p) | cw(48p) | cw(54p) | cw(48p) .
Symbol	Time\(hyout value	Significance	Cause for initiation	Normal termination	At the first expiry	At the following expiry
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | cw(48p) | cw(54p) | cw(48p) .
T 2 9	300\(hy600 ms	Local	 {
First congestion/first congestion indication after T
3
0 expires
 }	\(em	\(em	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | cw(48p) | cw(54p) | cw(48p) .
T 3 0	5\(hy10 s	Local	First congestion indication	\(em	\(em	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | cw(54p) | lw(48p) .
T 3 1	> 6 min	Local	 {
Release of ISDN User part signalling connection based on CO\ SCCP
 }	On expiry	\(em	Call reference reusable
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | cw(54p) | lw(48p) .
T 3 2	3\(hy5 s	Local	 {
On receipt of end\(hyto\(hyend message
 }	On expiry	\(em	 {
End\(hyto\(hyend message to be sent
 }
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 3 3	12\(hy15 s	Local	When send INR	On receipt of INF	Release call	\(em
_
.T&
cw(24p) | lw(36p) | lw(36p) | lw(54p) | lw(48p) | lw(54p) | cw(48p) .
T 3 4	12\(hy15 s	Local	 {
When send circuits group query
 }	 {
On receipt of circuits group query response
 }	Maintenance action	\(em
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau [6T3.764],\ \ \ A L'ITALIENNE, p. 28\fR 
.sp 1P
.RT
.ad b
.RT
.LP
.bp