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InfoMagic Standards 1994 January
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1988
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1991-12-12
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.rs
.\" Troff code generated by TPS Convert from ITU Original Files
.\" Not Copyright ( c) 1991
.\"
.\" Assumes tbl, eqn, MS macros, and lots of luck.
.TA 1c 2c 3c 4c 5c 6c 7c 8c
.ds CH
.ds CF
.EQ
delim @@
.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
\fBMONTAGE : FIN DE LA RECOMMANDATION I.251 EN\(hyT\* | TE DE CETTE PAGE\fR
.sp 2P
.LP
\v'18P'
\fBRecommendation\ I.252\fR
.RT
.sp 2P
.RT
.sp 2P
.sp 1P
.ce 1000
\fBCALL\ OFFERING\ SUPPLEMENTARY\ SERVICES\fR
.EF '% Fascicle\ III.7\ \(em\ Rec.\ I.252''
.OF '''Fascicle\ III.7\ \(em\ Rec.\ I.252 %'
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.PP
The purpose of this Recommendation is to provide the stage 1
description of the method defined in Recommendation\ I.130 using the means
given in Recommendation\ I.210.
.sp 1P
.RT
.PP
Supplementary services are described by a prose definition and
description (step\ 1.1) and by a dynamic description (step\ 1.3). The application
of the attribute technique (step\ 1.2), as defined in Recommendation\ I.140,
for supplementary services is for further study.
.PP
This Recommendation describes the following Call Offering
supplementary services:
.RT
.LP
I.252.1
Call Transfer (CT)
.LP
I.252.2
Call Forwarding Busy (CFB)
.LP
I.252.3
Call Forwarding No Reply (CFNR)
.LP
I.252.4
Call Forwarding Unconditional (CFU)
.LP
I.252.5
Call Deflection (CD) (Note)
.LP
I.252.6
Line Hunting (LH)
.PP
\fINote\fR \ \(em\ This service having been identified now requires further
study; its description is not yet included.
.sp 2P
.LP
\fB1\fR I.252.1\ \(em
\fBCall Transfer\fR
.sp 1P
.RT
.sp 1P
.LP
1.1
\fIDefinition\fR
.sp 9p
.RT
.PP
The Call Transfer supplementary service enables a user to transfer an established
(i.e. active) call to a third party. For the original call, the \*Qserved
user\*U (see \(sc\ 1.2.2) may have been either the calling or called party
(i.e. the call may have been either incoming or outgoing). This service
differs from the Call Diversion (i.e.\ Call Forwarding) supplementary services
in that the latter deal only with incoming calls that have not yet reached
the
\*Qfully\(hyestablished\*U state, whereas in the case of Call Transfer
an established end\(hyto\(hyend connection exists.
.bp
.RT
.sp 2P
.LP
1.2
\fIDescription\fR
.sp 1P
.RT
.sp 1P
.LP
1.2.1
\fIGeneral description\fR
.sp 9p
.RT
.PP
Three methods of Call Transfer are identified. One, called \*QNormal\*U
Call Transfer, is described in \(sc\ 1.3.2 below. The two others are described
in \(sc\ 1.3.4. Although the invocation of these various methods differ,
the
essential operation of Call Transfer is to transform the served user's
established call into a new call between the other party on the established
call and a third party. It should be noted that, in a Three\(hyParty Service
call, there are several stages at which the served user can effectively
transfer the call. These are described in the Three\(hyParty Service description.
.RT
.sp 2P
.LP
1.2.2
\fISpecific terminology\fR
.sp 1P
.RT
.sp 1P
.LP
1.2.2.1
\fIServed user, other parties\fR
.sp 9p
.RT
.PP
During the invocation and active phases, the service is under the control
of the \*Qserved user\*U, i.e. the one for whom the service was subscribed.
This user is also referred to as \*Quser A\*U. Other parties associated
with this service are defined as follows:
.RT
.LP
\(em
user B is the other party in the original call
(A\(<-
\(raB);
.LP
\(em
user C is the \*Qthird party\*U \(hy the other party in the
subsequent call (A | (raC).
.sp 1P
.LP
1.2.3
\fIQualifications on the applicability to telecommunication\fR
\fIservices\fR
.sp 9p
.RT
.PP
This supplementary service is considered meaningful when applied to the
Telephony teleservice and the speech and 3.1\ kHz audio bearer service.
Furthermore, it may also be meaningful when applied to other services.
.RT
.sp 2P
.LP
1.3
\fIProcedures\fR
.sp 1P
.RT
.sp 1P
.LP
1.3.1
\fIProvision/withdrawal\fR
.sp 9p
.RT
.PP
The Call Transfer supplementary service is subscribed to by prior arrangements
with the service provider. Subscription can be made for
\*QNormal Call Transfer\*U and/or for either of the alternate procedures
(i.e. \*QSingle\(hyStep Call Transfer\*U or \*QExplicit Call Transfer\*U)
offered by
the service provider.
.PP
Withdrawal of the service is made by the service provider upon
request by the subscriber or for service provider reasons.
.RT
.sp 2P
.LP
1.3.2
\fINormal procedures\fR
.sp 1P
.RT
.sp 1P
.LP
1.3.2.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
None identified.
.RT
.sp 1P
.LP
1.3.2.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
The served user, user A, can transform an established call with
user\ B into (effectively) a call from user\ B to a third party, user C.
When the served user (user\ A) asks the service provider to begin the \*QNormal\*U
Call
Transfer, the service provider puts the already established call (with
user\ B) on hold. User\ A then proceeds to establish the second call (to
user\ C). Upon
request from user\ A to complete the Call Transfer, the service provider
would connect users\ B and\ C together while removing the connections between
user A
and the other two users. (The extent to which the service provider re\(hyuses
the resources from the A\(<-
\(raB and A | (raC calls to form the B | (raC call is a
service provider option.)
.PP
\fINote\fR \ \(em\ In the resulting call B | (raC, user C will have all
the relevant characteristics of the called party, but user B will not necessarily
have all the characteristics of the calling party, depending on whether
user B
called user A and also depending on which service or supplementary service
is under consideration.
.PP
In some networks, user A can request completion of the Call Transfer either
during or after the establishment of the connection to user\ C.
.PP
The service provider will optionally notify users B and C of the
transfer and, depending on interworking conditions and the supplementary
services subscribed to by users\ B and\ C, will indicate to user\ B the
number of user\ C and will indicate to user\ C the number of user\ B.
.bp
.RT
.sp 2P
.LP
1.3.3
\fIExceptional procedures\fR
.sp 1P
.RT
.sp 1P
.LP
1.3.3.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
None identified.
.RT
.sp 1P
.LP
1.3.3.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
The service request would be rejected if the user invoking the
service has not subscribed to the Call Transfer service (or the requested
service option). The user would be notified of the cause for rejection
and the original call A\(<-
\(raB would remain in the state it was in before the
transfer request was received.
.PP
If user A's attempt to establish a connection to user\ C is
unsuccessful, (e.g. user\ C is busy), user A will be so informed and will be
able either to retrieve the original call A\(<-
\(raB or to attempt a new
connection (e.g. to C or to another party) (see Figure\ 2/I.252).
.PP
The transfer request would be rejected if the network is
unsuccessful in connecting users B and C (e.g. when user\ C is busy, when
there is network congestion, or when transfer restrictions are violated).
The user
would be notified of the cause for rejection and the two calls would remain
in the states they were in before the request was received.
.RT
.sp 2P
.LP
1.3.4
\fIAlternative procedures\fR
.sp 1P
.RT
.sp 1P
.LP
1.3.4.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
None identified.
.RT
.sp 2P
.LP
1.3.4.2
\fIInvocation and operation\fR
.sp 1P
.RT
.sp 1P
.LP
1.3.4.2.1
\fISingle\(hyStep Call Transfer\fR
.sp 9p
.RT
.PP
In this procedure, the served user can transfer an established call (with
user\ B) to another user (user\ C) without first establishing a call to
user\ C. When invoking a Single\(hyStep Call Transfer, the served user would
indicate to the service provider the address of user\ C. The service provider
would then establish a connection between users\ B and\ C, and disconnect the
served user, user\ A, from the original call with user\ B. It should be noted
that the service provider is not required to reinstate the call A\(<-
\(raB if a Single\(hyStep Call Transfer to user\ C fails. It is also necessary
to notify
user\ B of the progress of the establishment of the call to user C, particularly
if the call A\(<-
\(raB cannot be reinstated.
.RT
.sp 1P
.LP
1.3.4.2.2
\fIExplicit Call Transfer\fR
.sp 9p
.RT
.PP
In this procedure, the served user A puts the already established call
(with user\ B) on hold and then proceeds to establish another call (to
user\ C) or to accept an incoming call (from user\ C). If user A's attempt to
establish a connection to user\ C is unsuccessful (e.g. user\ C is busy),
user\ A will be so informed and will be able either to retrieve the original
call A\(<-
\(raB or to attempt a new connection (e.g. to user\ C or to another
party) (see Figure\ 4/I.252).
.PP
User A then explicitly requests that the call with user B be
transferred to user C. (By contrast, in the Normal Call Transfer procedure,
the service provider \*Qknows\*U that the two calls [A\(<-
\(raB and A | (raC] are related; requesting completion of Normal Call Transfer
for call A | (raC implicitly means
\*Uconnect user C with user\ B\*U.) The remainder of the procedures are
identical to Normal Call Transfer (with the possible exception of the failure
procedures.)
.RT
.sp 1P
.LP
1.4
\fINetwork capabilities for charging\fR
.sp 9p
.RT
.PP
This Recommendation does not cover charging principles. Future
Recommendations in the D\(hySeries are expected to contain that information.
.PP
It shall be possible to charge the subscriber accurately for the
service.
.RT
.sp 1P
.LP
1.5
\fIInterworking requirements\fR
.sp 9p
.RT
.PP
User B and user C may not be able to receive each other's address if one
(or both) of the calls exits from the ISDN network. The different
scenarios are shown in the following tables. The tables assume that B is the
originator of the call to A. The network may not be able to recognize user
identification if one or both of the calls requires interworking with non\(hyISDN
network(s).
.bp
.PP
For illustrative purposes, assume that user B originates a call to
user\ A, and user\ A initiates the call transfer service to connect user\ B to
user\ C. The different scenarios are shown in the following tables:
.RT
.LP
.sp 2
.ce
\fBH.T. [T1.252]\fR
.LP
.ce
i) Users A, B and C are in ISDN
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
{
Address information available to
} Address of A Address of B Address of C
_
.T&
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
User A \(em YES YES
_
.T&
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
User B YES \(em YES
_
.T&
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
User C YES YES \(em
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau i) [T1.252], p. 1\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 2
.ce
\fBH.T. [T2.252]\fR
.ce
ii) Users A and B are in ISDN. User C is in another network
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
{
Address information available to
} Address of A Address of B Address of C
_
.T&
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
User A \(em YES YES
_
.T&
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
User B YES \(em YES
_
.T&
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
User C NO NO \(em
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau ii) [T2.252], p. 2\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 2
.ce
\fBH.T. [T3.252]\fR
.ce
iii) Users A and C are in ISDN. User B is in another network
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
{
Address information available to
} Address of A Address of B Address of C
_
.T&
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
User A \(em NO YES
_
.T&
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
User B YES \(em NO
_
.T&
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
User C YES NO \(em
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau iii) [T3.252], p. 3\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T4.252]\fR
.ce
iv) User A is in ISDN. Users B and C are in another network
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
{
Address information available to
} Address of A Address of B Address of C
_
.T&
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
User A \(em NO YES
_
.T&
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
User B YES \(em NO
_
.T&
cw(66p) | cw(30p) | cw(30p) | cw(30p) .
User C NO NO \(em
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau iv) [T4.252], p. 4\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
1.6
\fIInteraction with other supplementary services\fR
.sp 1P
.RT
.sp 1P
.LP
1.6.1
\fICall Waiting\fR
.sp 9p
.RT
.PP
Assume served user A has an established call with user B and wishes to
transfer user B to user C, and users A, B and C all have subscribed to
the Call Waiting Service. If a call from user D is received while:
.RT
.LP
i)
user A is invoking Normal Call Transfer
.LP
\(em
If user D calls user A at any time before A requests
the completion of the transfer of user\ B to user\ C,
then user\ A shall receive a call waiting indication.
When user\ B is transferred to user\ C, a B\(hychannel
would normally become idle, enabling user A to accept
the waiting call.
.LP
\(em
If user D calls user B, then user B can use normal call waiting procedures
to accept the waiting call
(preferably once the transfer to user\ C is completed).
If user\ B had a call waiting indication while the call was
established with user\ A, the
call waiting indication
shall not be affected by the transfer of user B to user\ C.
.LP
\(em
If user D calls user C during the transfer process
(i.e. while user C is engaged on an active call with user\ A),
the call waiting indication shall be presented to user\ C.
User\ C could then use Normal Call Waiting procedures to accept
the waiting call (preferably once the call transfer is
completed).
.LP
ii)
user A is invoking Single\(hyStep Call Transfer
.LP
\(em
User A may receive a call waiting indication any time before or during
the transfer invocation. Once the Single\(hyStep
Call Transfer is invoked, then user\ A is disconnected from
user\ B, thus, causing a B\(hychannel to normally become idle,
enabling user\ A to accept the waiting call.
.LP
\(em
User B may receive a call waiting indication any time before or during
the transfer invocation. User\ B could then use
Normal Call Waiting procedures to accept the waiting call
(preferably once the transfer is completed). If the transfer is
not successful (e.g. user\ C is busy), then user\ B would normally
release the call, causing a B\(hychannel to become idle and enabling
user\ B to accept the waiting call.
.LP
\(em
If the call from user D arrives at user C's serving
office after the call from A, user C would receive a call waiting
indication. The call waiting indication shall not be affected by
the transfer of user B to user C. User C could then use Normal
Call Waiting procedures to accept the waiting call (preferably
once the transfer is completed). If the call from user D arrives
before the call from user\ A, the call from user A will receive
call waiting treatment.
.LP
iii)
user A is invoking Explicit Call Transfer
.LP
\(em
The interaction for users A, B, or C with call
waiting are the same as for\ i) above.
.bp
.sp 1P
.LP
1.6.2
\fICall Transfer\fR
.sp 9p
.RT
.PP
It shall be possible for both users (user A and user B) in a
normal call, who have each subscribed to the Call Transfer Service, to
simultaneously transfer the call. That is, if user A and user B are active
in an established call, user\ A could transfer the call to a user C and
user B
could transfer the call to a user\ D. Call progress signals and other
notifications will be delivered to the appropriate party at the time
the signal is received. See Figure\ 1/I.252.
.RT
.LP
.rs
.sp 8P
.ad r
\fBFigure 1/I.252, (N), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
1.6.3
\fIConnected Line Identification Presentation (COLP)\fR
.sp 9p
.RT
.PP
Assume that user A has an established call with user B and wishes to transfer
this call with user\ B to user\ C. Except in the case where user\ C
prohibits the presentation of his/her number, user C's number shall be
presented:
.RT
.LP
\(em
to user B upon the successful completion of the transfer to
user\ C (independent of the type of transfer procedure invoked by
user\ A) provided that user B has subscribed to COLP;
.LP
\(em
to user A when user A is using the Normal or Explicit Call
Transfer procedures and has subscribed to COLP. The reached party's
number will not be presented to user A if user A invokes the
Single\(hyStep Call Transfer procedure.
.PP
\fINote\fR \ \(em\ Number presentation may not be possible if
interworking with a non\(hyISDN network is involved in the call transfer.
.sp 1P
.LP
1.6.4
\fIConnected Line Identification Restriction (COLR)\fR
.sp 9p
.RT
.PP
Assume that a user A has an established call with a user B and
wishes to transfer this call with user\ B to a user\ C.
.PP
If user C has subscribed to COLR, then user A shall not receive
user\ C's number when user\ A invokes any Call Transfer procedure and user\ B
shall not receive user C's number during the transfer of user\ B to
user\ C.
.RT
.sp 1P
.LP
1.6.5
\fICalling Line Identification Presentation (CLIP)\fR
.sp 9p
.RT
.PP
For Normal and Explicit Call Transfers, user A shall have his
number presented to user C and user B shall have his number presented to
user\ C unless:
.RT
.LP
1)
user A or B has number presentation restrictions; or
.LP
2)
the call transfer process requires interworking with a
non\(hyISDN network.
.PP
For Single\(hyStep Call Transfer, if user C has subscribed to CLIP he shall
receive the number of user B unless:
.LP
1)
User B has address presentation restrictions; or
.LP
2)
the call transfer process requires interworking with a
non\(hyISDN network.
.PP
User C may also receive user A's address as a \*Q
redirecting
party
\*U unless:
.LP
1)
User A has address presentation restrictions; or
.LP
2)
the call transfer process requires interworking with a
non\(hyISDN network.
.bp
.sp 1P
.LP
1.6.6
\fICalling Line Identification Restriction (CLIR)\fR
.sp 9p
.RT
.PP
Assume that a user A has an established call with a user B and wishes to
transfer this call with user\ B to a user\ C.
.PP
If user A has subscribed to CLIR, then user C shall not receive a
calling number when user A invokes any Call Transfer procedure. If user\
B has subscribed to CLIR, then user\ C shall not receive a calling number
during the transfer of user B to user\ C.
.RT
.sp 1P
.LP
1.6.7
\fIClosed User Group (CUG)\fR
.sp 9p
.RT
.PP
The intention of CUG is to allow some connections and prohibit
others; call transfer must not compromise this intention.
.PP
Assume that a user A has an established call with user B and wishes to
transfer this call with user\ B to a user\ C. When considering CUG requirements
and restrictions, the transfer process (all three procedures) should be
considered as three separate call processings:
.RT
.LP
1)
when users A and B established their original connection, if
user A and/or user B was a member of a CUG, then CUG requirements must
have been met before the two parties were connected;
.LP
2)
when user A invokes a transfer procedure, both user A and
user C must meet CUG requirements before the call can be completed, if
either user A or user C is a member of a CUG;
.LP
3)
finally, the transfer connection of user B to user C must
first meet all CUG requirements (if either user\ B and/or user C is a
member of a CUG) before the two parties can establish
communications.
.PP
The above requirements insure that CUG security is not violated. They prevent,
for example, a user A who meets CUG requirements with user\ C from transferring
a user B who does not meet CUG requirements with user\ C.
.sp 1P
.LP
1.6.8
\fIConference Calling\fR
.sp 9p
.RT
.PP
Refer to Recommendation\ I.254, \(sc\ 1.6.2, ineraction with Call
Transfer.
.RT
.sp 1P
.LP
1.6.9
\fIDirect\(hyDialling\(hyIn\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
1.6.10
\fICall Divertion (i.e. Call Forwarding Services)\fR
.sp 9p
.RT
.PP
In general, if the served user attempts to establish a call to a
party that is forwarding calls, the forwarded\(hyto party will be alerted
and may be transferred to. Specific procedures are described below.
.PP
The count for the number of forwarding \*Qhops\*U should be cleared
each time a call transfer occurs.
.PP
Assume that a user A has an established call with a user B and wishes to
transfer this call with user\ B to a user\ C:
.RT
.sp 1P
.LP
1.6.10.1
\fICall Forwarding Busy (CFB)\fR
.sp 9p
.RT
.PP
User C, which has subscribed to CFB, may be busy on another call
when user A's call is received. The call from user A would then be routed to
another user\ D. For Normal and Explicit Call Transfers, user A would, in
general, be aware of the forwarding and could make a decision as to whether
or not the transfer of user\ B should be completed to the forwarded\(hyto
user D. For Single\(hyStep Call transfer, user\ B would be connected to
the forwarded\(hyto
user\ D.
.bp
.RT
.sp 1P
.LP
1.6.10.2
\fICall Forwarding No Reply (CFNR)\fR
.sp 9p
.RT
.PP
User C, who has subscribed to CFNR, may have a free access but does not
answer user A's call. Upon expiration of the CFNR timer, user A's call
would be routed to another user\ D. For Normal and Explicit Call Transfers,
user\ A would, in general, be aware of the forwarding and could make a
decision as to whether or not the transfer of user\ B should be completed
to the
forwarded\(hyto user\ D. For Single\(hyStep Call Transfer, user\ B would
be connected to the forwarded\(hyto user\ D.
.RT
.sp 1P
.LP
1.6.10.3
\fICall Forwarding Unconditional (CFU)\fR
.sp 9p
.RT
.PP
If user C has subscribed to CFU, then user A's call will be routed to another
user D. For Normal and Explicit Call Transfers, user A would, in
general, be aware of the forwarding and could make a decision as to whether
or not the transfer of user B should be completed to the forwarded\(hyto
user D. For Single\(hyStep Call Transfer, user B would be connected to
the forwarded\(hyto
user\ D.
.RT
.sp 1P
.LP
1.6.11
\fILine Hunting\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
1.6.12
\fIThree\(hyParty Service\fR
.sp 9p
.RT
.PP
The forms of call transfer given in Table\ 1/I.252 are applicable to the
indicated states of Three\(hyParty Service.
.RT
.ce
\fBH.T. [T5.252]\fR
.ce
TABLE\ 1/I.252
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(60p) | cw(36p) sw(36p) sw(36p) , ^ | c | c | c.
{
Three\(hyparty service state
} Call transfer
Normal Single\(hystep Explicit
_
.T&
lw(60p) | cw(36p) | cw(36p) | cw(36p) .
Active/held {
YES | fB\fR\(ua\fBa\fR\(ua\fB)\fR
} NA YES
_
.T&
lw(60p) | cw(36p) | cw(36p) | cw(36p) .
Three\(hyway conversation YES | ua\d\u)\d\fR NA {
NA
\fR
\ua\d\u)\d
See Figure 4/I.254, three\(hyparty service dynamic
description.
}
_
.TE
.nr PS 9
.RT
.ad r
\fBTable 1/I.252 [T5.252], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
1.6.13
\fIUser\(hyto\(hyUser Signalling (UUS)\fR
.sp 9p
.RT
.PP
Prior to transfer: Prior to beginning a transfer user\ A can employ UUS
services 1, 2 and\ 3 normally.
.PP
During transfer: UUS services 1, 2 and 3 are only allowable between
user\ A and user B and/or between user\ A and user\ C. User\(hyto\(hyuser
information\ (UUI) sent by user B will be delivered to user A, not user
C. UUI cannot be transferred between users\ B and\ C during this time.
The delivery of service 3 UUI cannot be guaranteed during transfer.
.PP
After completion of transfer: Only if user B and user A both request service(s)
1, 2 and/or 3, is that service(s) available for use between users\ B and
C after the transfer is completed. If user A did not request a given
service in the set\(hyup to user\ C, user\ B will be informed that he can
no longer employ that service on this call. If user\ A requested a particular
service in the set\(hyup to user\ C, but the service was not requested
by user\ B in the
initial
set\(hyup message to user\ A, user\ C will be informed at the completion of the
transfer that he can no longer employ the service.
.PP
\fINote 1\fR \ \(em\ The procedures to be followed if transfer of charge is
permitted are for further study.
.PP
\fINote 2\fR \ \(em\ The procedures to be followed if the number of allowable
messages has been reached by any party are for further study.
.bp
.RT
.sp 1P
.LP
1.6.14
\fIMultiple Subscriber Number\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
1.6.15
\fICall Hold\fR
.sp 9p
.RT
.PP
Parties held by users A, B and C, before invoking a transfer
process will continue to be held by the parties after the transfer process.
For example, if user\ B places his call to user\ A on hold during user
A's transfer of the call to user\ C, the resulting call from user\ B to
user\ C shall remain
held by user\ B until it is retrieved by user\ B. The only exception to
this is the Explicit Call Transfer procedure when user\ A transfers user
B to user\ C. In this case, user B will no longer be held by user A after
the transfer is
completed.
.PP
Special case: Assume users A and B were in an active call and user A places
user B on hold, and user B places user\ A on hold. If user A transfers
user\ B to user\ C by invoking the Explicit Call Transfer procedure, then the
transfer shall take effect with the resulting call between users\ B and\ C
remaining held by user\ B and the held call between user\ A to user\ B shall be
discarded (i.e. user\ B cannot retrieve user\ A after the transfer).
.RT
.sp 1P
.LP
1.6.16
\fIAdvice of Charge\fR
.sp 9p
.RT
.PP
Refer to Recommendation I.256, \(sc\(sc\ 2.1.6.2, 2.2.6.2, 2.3.6.2,
Interaction with Call Transfer.
.RT
.sp 1P
.LP
1.7
\fIDynamic description\fR
.sp 9p
.RT
.PP
The dynamic description of this service is shown in
Figure\ 2/I.252.
.RT
.sp 2P
.LP
\fB2\fR I.252.2\ \(em
\fBCall Forwarding Busy\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
\fIDefinition\fR
.sp 9p
.RT
.PP
Call Forwarding Busy (CFB) permits a \*Qserved user\*U (see \(sc\ 2.2.2)
to have the network send to another number all incoming calls for the served
user's ISDN number (or just those associated with a specified basic service)
which meet busy at the served user's ISDN number. The served user's originating
service is unaffected.
.PP
\fINote\fR \ \(em\ In normal situations, the CFB service is provided on a per
access basis. (In these situations, there is a one\(hyto\(hyone relationship
between ISDN number and access.) However, the network may recognize multiple
numbers on a single interface; in addition, it may not undertstand a complete
ISDN number (e.g.\ DDI). In these cases, the CFB service is offered on
the basis of the part of the ISDN number which the network can recognize.
.RT
.sp 2P
.LP
2.2
\fIDescription\fR
.sp 1P
.RT
.sp 1P
.LP
2.2.1
\fIGeneral description\fR
.sp 9p
.RT
.PP
For a given ISDN number, this service (including options) may be
subscribed to for each basic service to which the user(s) of the number
subscribes, or collectively for all the basic services to which the user(s)
subscribes. Since subscription is on an ISDN number basis, the same Call
Forwarding subscriptions will apply to all terminals using this number.
.PP
\fINote\fR \ \(em\ In this service description, it is assumed that a single
ISDN number is not shared across multiple interfaces. A single ISDN number
may,
however, be shared by multiple terminals on the same interface. Procedures
permitting an ISDN number to be shared across multiple interfaces are for
further study. For multiple access installations, it may be possible for the
user to specify, on activation, if the service is applicable to a specific
access or all accesses associated with that installation.
.PP
The served user can request a different forwarded\(hyto number for
each basic service subscription parameter value to which he has subscribed.
.PP
An indication that the CFB service is activated on a number may, as an
option, be given to the user who has forwarding activated, each time an
outgoing call is made. This may take the form of a special indication in the
proceed response.
.bp
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure 2/I.252, (N), p. 7\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 3/I.252, (N), p. 8\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 4/I.252, (N), p. 9\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
2.2.2
\fISpecific terminology\fR
.sp 9p
.RT
.PP
A
\fIserved user\fR is a user of a particular ISDN number who is requesting
that calls to his number be forwarded. This user may also be
referred to as the forwarding user or the called user.
.PP
A
\fIforwarded\(hyto user\fR is a user to whom the call shall be
forwarded.
.RT
.sp 1P
.LP
2.2.3
\fIQualifications on the applicability to telecommunications\fR
\fIservices\fR
.sp 9p
.RT
.PP
No restrictions identified.
.RT
.sp 2P
.LP
2.3
\fIProcedures\fR
.sp 1P
.RT
.sp 1P
.LP
2.3.1
\fIProvision/withdrawal\fR
.sp 9p
.RT
.PP
CFB shall be provided after pre\(hyarrangement with the service
provider.
.PP
The service can be offered with three subscription options. Options
apply separately to each basic service subscribed to on each ISDN number.
For each subscription option, only one value can be selected. Subscription
options are summarized below:
.RT
.LP
.sp 1
\fISubscription options\fR
\fIValue\fR
.LP
Served user receives notification that call has been forwarded
\(em
No
\(em
Yes, with call offering information (see \(sc\ 2.3.2.2)
\fR Calling user receives notification that his call has been forwarded
\(em
No
\(em
Yes, with or without forwarded\(hyto user number
\fR Served user receives notification that CFB is currently activated
\(em
No
\(em
Yes
.sp 2P
.LP
2.3.2
\fINormal procedures\fR
.sp 1P
.RT
.sp 1P
.LP
2.3.2.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
Same as for Call Forwarding Unconditional (CFU), see \(sc\ 4.
.RT
.sp 1P
.LP
2.3.2.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
The following illustration clarifies the CFB procedures. Assume
that A calls B1, who forwards the call to B2,\ . | | , Bm,\ . | | , Bx.
The final receiver of the call is\ C.
.RT
.LP
.rs
.sp 2P
.ad r
\fBFigure, (N), p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
2.3.2.2.1
\fIServed user Bm's perspective\fR
.sp 9p
.RT
.PP
If CFB is active and the served user is Network Determined User
Busy (NDUB) or User Determined User Busy (UDUB), then an incoming call
to the served user will be forwarded. In case of NDUB, the call is not
offered to the served user.
.PP
In the case of UDUB, the call will have been offered to the served
user. Normal call set\(hyup information will already have been provided to the
served user. When the forwarding attempt is started, the served user will
receive notification that a call has been forwarded. No further notification
is given.
.PP
When an incoming call is forwarded without being offered to the
served user (i.e. NDUB condition), the served user, as a subscription option,
may receive notification of the call forwarding (but will not be able to
answer the incoming call). This notification is given as soon as the
forwarding
attempt
is started.
.PP
This notification includes the following information (on the call that
has been forwarded):
.RT
.LP
1)
indication that a call has been forwarded;
.LP
2)
telecommunications service information (e.g. bearer
capability, higher layer compatibility);
.LP
3)
user\(hyto\(hyuser information;
.LP
4)
Bm's number;
.LP
5)
calling party number A (if CLIP applicable).
.PP
If multiple forwardings have occurred and the served user is
authorized to receive additional information, he may also receive:
.LP
6)
originally called number B1;
.LP
7)
cause for original forwarding;
.LP
8)
last
forwarding number
B | m\ \(em\ 1);
.LP
9)
cause for last forwarding.
.sp 1P
.LP
2.3.2.2.2
\fIForwarded\(hyto user C's perspective:\fR
.sp 9p
.RT
.PP
The forwarded\(hyto user C will receive an indication that the call
has been forwarded.
.PP
As an option he may also receive:
.RT
.LP
1)
originally called number B1;
.LP
2)
cause for original forwarding;
.LP
3)
last forwarding number Bx;
.LP
4)
cause for last forwarding.
.PP
(Depending on the use of other supplementary services, the
forwarded\(hyto user C may also receive information such as the calling party A
number and user\(hyto\(hyuser signalling. See the descriptions of interactions
with other supplementary services.)
.sp 1P
.LP
2.3.2.2.3
\fICalling user A's perpective\fR :
.sp 9p
.RT
.PP
As a subscription option, the served user Bm can request that the calling
user receive a notification that the call has been forwarded and, as an
additional subscription option, that notification can include the forwarded\(hy
to number B(m+1). Transfer of the forwarded\(hyto user number will not
take place if number restrictions at the forwarded\(hyto user exist.
.RT
.sp 2P
.LP
2.3.3
\fIExceptional procedures\fR
.sp 1P
.RT
.sp 1P
.LP
2.3.3.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc\ 4).
.RT
.sp 1P
.LP
2.3.3.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
Call forwarding applies only to subscribed basic services. Calls to an
ISDN number requesting a basic service which is not subscribed to, will
never be forwarded.
.bp
.PP
Within an ISDN, or tandem ISDNs, the total number of all
forwardings for each call should be limited. The maximum number of such
connections should be limited to a value between 3 and 5 for each call.
This is to prevent infinite looping.
.PP
If the limit is reached and an attempt is made to forward the call
an additional time, then the forwarded call shall be treated as follows:
.PP
If the
forwarded call
cannot be completed to the forwarded\(hyto destination, then the network
will clear the forwarded leg of the call.
Specifically, if CFB has been invoked, and CNFR has not occurred, then
the call would be cleared back towards the calling user, and the calling
user would be sent a cause to indicate that the call has been forwarded
but not completed
(i.e. because of network congestion, invalid number, facility not available,
etc.). If the forwarded call cannot be completed and if CFNR has occurred,
then the call should only be cleared back as far as the CFNR exchange and
the
calling user will, in the case of a telephony call, continue to receive
inband ringing tone.
.RT
.sp 2P
.LP
2.3.4
\fIAlternative procedures\fR
.sp 1P
.RT
.sp 1P
.LP
2.3.4.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
None identified.
.RT
.sp 1P
.LP
2.3.4.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
None identified.
.RT
.sp 1P
.LP
2.4
\fINetwork capabilities for charging\fR
.sp 9p
.RT
.PP
This Recommendation does not cover charging principles. Future
Recommendations in the D\(hySeries are expected to contain that information.
.PP
It shall be possible to charge the subscriber accurately for the
service.
.RT
.sp 1P
.LP
2.5
\fIInterworking requirements\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc\ 4).
.RT
.sp 1P
.LP
2.6
\fIInteraction with other supplementary services\fR
.sp 9p
.RT
.PP
The ways in which Call Forwarding Busy interacts with other
supplementary services are in general identical to the ways in which Call
Forwarding Unconditional interacts with other supplementary services. Thus,
if the interactions are described to be \*Qsame as CFU\*U, the CFU text
should be
taken verbatim, except that the expression \*QCall Forwarding Unconditional\*U
should be replaced by \*QCall Forwarding Busy\*U.
.RT
.sp 1P
.LP
2.6.1
\fICall Waiting\fR
.sp 9p
.RT
.PP
Calling user: same as CFU (see \(sc\ 4).
.PP
Called user: No interaction. That is, if the user is not NDUB, Call
Waiting will take place. If the user is NDUB, Call Forwarding Busy will take
place.
.PP
Forwarded\(hyto user: A forwarded call can invoke Call
Waiting.
.RT
.sp 1P
.LP
2.6.2
\fICall Transfer\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc\ 4).
.RT
.sp 1P
.LP
2.6.3
\fIConnected Line Identification Presentation\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc\ 4).
.RT
.sp 1P
.LP
2.6.4
\fIConnected Line Identification Restriction\fR
.sp 9p
.RT
.PP
Same as CFU.
.bp
.RT
.sp 1P
.LP
2.6.5
\fICalling Line Identification Presentation\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc\ 4).
.RT
.sp 1P
.LP
2.6.6
\fIConnected Line Identification Restriction\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc\ 4).
.RT
.sp 1P
.LP
2.6.7
\fIClosed User Group\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc\ 4).
.RT
.sp 1P
.LP
2.6.8
\fIConference Calling\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc\ 4).
.RT
.sp 1P
.LP
2.6.9
\fIDirect\(hyDialling\(hyIn\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 2P
.LP
2.6.10
\fICall Diversion (i.e. Call Forwarding) services\fR
.sp 1P
.RT
.sp 1P
.LP
2.6.10.1
\fICall Forwarding Busy\fR
.sp 9p
.RT
.PP
Not applicable.
.RT
.sp 1P
.LP
2.6.10.2
\fICall Forwarding No Reply\fR
.sp 9p
.RT
.PP
The invocation of CFB takes precedence over CFNR.
.RT
.sp 1P
.LP
2.6.10.3
\fICall Forwarding Unconditional\fR
.sp 9p
.RT
.PP
The invocation of CFU takes precedence over CFB.
.RT
.sp 1P
.LP
2.6.11
\fILine Hunting\fR
.sp 9p
.RT
.PP
In general, Line Hunting takes precedence over CFB. Thus, CFB only occurs
if all members of the
hunt group
are busy.
.RT
.sp 1P
.LP
2.6.12
\fIThree\(hyParty Service\fR
.sp 9p
.RT
.PP
Refer to Recommendation\ I.254, \(sc\ 2.6.10, interaction with CFB.
.RT
.sp 1P
.LP
2.6.13
\fIUser\(hyto\(hyUser Signalling\fR
.sp 9p
.RT
.PP
Same as CFU (\(sc\ 4), except that service 2 of UUS cannot be
guaranteed prior to completion of the Call Forwarding Busy in case of a
user\(hydetermined\(hybusy.
.RT
.sp 1P
.LP
2.6.14
\fIMultiple Subscriber Number\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
2.6.15
\fICall Hold\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.bp
.RT
.sp 1P
.LP
2.6.16
\fIAdvice of Charge\fR
.sp 9p
.RT
.PP
Refer to Recommendation\ I.256, \(sc\(sc\ 2.1.6.10, 2.2.6.10, 2.3.6.10,
interaction with CFB.
.RT
.sp 1P
.LP
2.7
\fIDynamic description\fR
.sp 9p
.RT
.PP
The dynamic description given in Figure\ 5/I.252 contains the
descriptions of the three Call Forwarding services (CFU, CFB, and CFNR).
.RT
.LP
.rs
.sp 43P
.ad r
\fBFigure 5/I.252 (feuillet 1 sur 5), (N), p. 11\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 5/I.252 (feuillet 2 sur 5), (N), p. 12\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 5/I.252 (feuillet 3 sur 5), (N), p. 13\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 5/I.252 (feuillet 4 sur 5), (N), p. 14\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 5/I.252 (feuillet 5 sur 5), (N), p. 15\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB3\fR I.252.3\ \(em
\fBCall Forwarding No Reply\fR
.sp 1P
.RT
.sp 1P
.LP
3.1
\fIDefinition\fR
.sp 9p
.RT
.PP
Call Forwarding No Reply (CFNR) permits a \*Qserved user\*U (see
\(sc\ 3.2.2) to have the network send to another number all incoming calls
for the served user's ISDN number which meet no reply, or just those associated
with a specific basic service which meet no reply. The served user's originating
service is unaffected.
.PP
\fINote\fR \ \(em\ In normal situations, the CFNR service is provided on
a per access basis. (In these situations, there is a one\(hyto\(hyone relationship
between ISDN number and access.) However, the network may recognize multiple
numbers on a single interface; in addition, it may not understand a complete
ISDN number (e.g.\ DDI). In these cases, the CFNR service is offered on
the basis of the
part of the ISDN number which the network can recognize.
.RT
.sp 2P
.LP
3.2
\fIDefinition\fR
.sp 1P
.RT
.sp 1P
.LP
3.2.1
\fIGeneral description\fR
.sp 9p
.RT
.PP
For a given ISDN number, this service (including options) may be
subscribed to for each basic service to which the user(s) of the number
subscribes, or collectively for all the basic services to which the user(s)
subscribes. Since subscription is on an ISDN number basis, the same
Call Forwarding subscriptions will apply to all terminals using this
number.
.PP
Two conditions of CFNR are possible as follows:
.RT
.LP
1)
the call is offered and no indication of a compatible
terminal is received; or
.LP
2)
the call is offered and an indication of a compatible
terminal is received.
.PP
Only case 2) is considered here. Case 1) is for further
study.
.PP
\fINote\fR \ \(em\ In this service description, it is assumed that a single
ISDN number is not shared across multiple interfaces. A single ISDN number
may,
however, be shared by multiple terminals on the same interface. Procedures
permitting an ISDN number to be shared across multiple interfaces are for
further study. For multiple access installations, it may be possible for the
user to specify, on activation, if the service is applicable to a specific
access or all accesses associated with that installation.
.PP
The served user can request a different forwarded\(hyto number for each
basic service subscription parameter value to which he has subscribed.
.PP
An indication that the CFNR service is activated on a number may, as an
option, be given to the user who has forwarding activated, each time an
outgoing call is made. This may take the form of a special indication in the
proceed response.
.RT
.sp 1P
.LP
3.2.2
\fISpecific terminology\fR
.sp 9p
.RT
.PP
A \fIserved user\fR | is a user of particular ISDN number who is
requesting that calls to his number be forwarded. This user may also be
referred to as the forwarding user or the called user.
.PP
\fIA forwarded\(hyto user\fR | is a user to whom the call shall be
forwarded.
.RT
.sp 1P
.LP
3.2.3
\fIQualifications on the applicability to telecommunication\fR
\fIservices\fR
.sp 9p
.RT
.PP
No restrictions identified.
.RT
.sp 2P
.LP
3.3
\fIProcedures\fR
.sp 1P
.RT
.sp 1P
.LP
3.3.1
\fIProvision/withdrawal\fR
.sp 9p
.RT
.PP
CFNR shall be provided after pre\(hyarrangement with the service
provider.
.bp
.PP
The service can be offered with four subscription options. Options
apply separately to each basic service subscribed to an each ISDN number.
For each subscription option, only one value can be selected. Subscription
options are summarized below:
.RT
.LP
.sp 1
\fISubscription options\fR \fIValue\fR Served user receives notification
that call has been forwarded
\(em
No
\(em
Yes, with call offering information (see
\(sc\ 3.3.2.2)
Calling user receives notification that his call has been forwarded
\(em
No
\(em
Yes, with or without forwarded\(hyto user number
.LP
No reply condition timer
\(em
5\(hy60 seconds, in steps of 5 seconds
Served user received notification that CFNR is currently activated
\(em
No
\(em
Yes
.sp 2P
.LP
3.3.2
\fINormal procedures\fR
.sp 1P
.RT
.sp 1P
.LP
3.3.2.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc 4).
.RT
.sp 1P
.LP
3.3.2.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
The following illustration clarifies the CFNR procedures. Assume
that A calls B1, who forwards the call to B2,\ . | | , Bm,\ . | | , Bx.
The final receiver of the call is C.
.RT
.LP
.rs
.sp 2P
.ad r
\fBFigure, (N), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.3.2.2.1
\fIServed user Bm's perspective\fR
.sp 9p
.RT
.PP
When CFNR is active, incoming calls will be offered to the served user.
Normal call offering information is provided to the served user. If the
served user does not reply within a subscribed time interval, the call
will be forwarded. The served user, as a subscription option, may receive
notification that a call has been forwarded. This notification is given
as soon as the
forwarding attempt is started. No further notification is given.
.RT
.sp 1P
.LP
3.3.2.2.2
\fIForwarded\(hyto user C's perspective\fR
.sp 9p
.RT
.PP
The forwarded\(hyto user C will receive an indication that the call
has been forwarded.
.PP
As an option he may also receive:
.RT
.LP
1)
originally called number B1;
.LP
2)
cause for original forwarding;
.LP
3)
last forwarding number Bx;
.LP
4)
cause for last forwarding.
.PP
(Depending on the use or other supplementary services, the
forwarded\(hyto user\ C may also receive information such as the calling
party\ A
number and user\(hyto\(hyuser signalling. See the descriptions of interactions
with other supplementary services.)
.bp
.sp 1P
.LP
3.3.2.2.3
\fICalling user A's perspective\fR
.sp 9p
.RT
.PP
As a subscription option, the served user Bm can request that the calling
user receive a notification that the call has been forwarded and, as an
additional subscription option, that notification can include the forwarded\(hyto
number\ B(m\ +\ 1). Transfer of the fowarded\(hyto user number will not
take place if number restrictions at the forwarded\(hyto user exist.
.RT
.sp 2P
.LP
3.3.3
\fIExceptional procedures\fR
.sp 1P
.RT
.sp 1P
.LP
3.3.3.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc 4).
.RT
.sp 1P
.LP
3.3.3.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
Call forwarding applies only to subscribed basic services. Calls to an
ISDN number requesting a basic service which is not subscribed to will
never be forwarded.
.PP
Within an ISDN, or tandem ISDNs, the total number of all forwardings for
each call should be limited. The maximum number of such connections should
be limited to a value between 3 and 5 for each call. This is to prevent
infinite looping.
.PP
If the limit is reached and an attempt is made to forward the call an additional
time, the forwarded call shall be treated as follows:
.PP
If the forwarded call cannot be completed to the forwarded\(hyto
destination, then the network will clear the forwarded leg of the call
and the calling user will, in the case of a telephony call, continue to
receive inband ringing tone. The \*Qno reply timer\*U will not be restarted
by the network.
(Note that during the activation of CFNR, the calling user shall continue to
alert the forwarding user until alerting commences at the forwarded\(hyto
user.)
.RT
.sp 2P
.LP
3.3.4
\fIAlternative procedures\fR
.sp 1P
.RT
.sp 1P
.LP
3.3.4.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
None identified.
.RT
.sp 1P
.LP
3.3.4.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
None identified.
.RT
.sp 1P
.LP
3.4
\fINetwork capabilities for charging\fR
.sp 9p
.RT
.PP
This Recommendation does not cover charging principles. Future
Recommendations in the D\(hyseries are expected to contain that information.
.PP
It shall be possible to charge the subscriber accurately for the
service.
.RT
.sp 1P
.LP
3.5
\fIInterworking requirements\fR
.sp 9p
.RT
.PP
If a forwarded\(hyto number is not within the ISDN, then an
interworking situation is said to exist.
.PP
If a forwarded call meets an interworking situation, then an
interworking indication should be sent to the calling party. Also, if the
network cannot determine that the forwarded call cannot be completed (i.e.\
the progress of the call is provided in\(hyband), the network shall cease
alerting at the diverting termination and connect the calling user to the
diverted call in order to receive these inband supervisory indications.
.PP
\fINote\fR \ \(em\ The number of times a call has been forwarded once it has
exited the Common Channel Signalling (CCS) network cannot be limited by
this CCS network.
.bp
.RT
.sp 1P
.LP
3.6
\fIInteraction with other supplementary services\fR
.sp 9p
.RT
.PP
The ways in which Call Forwarding No Reply interacts with other
supplementary services are in general identical to the ways in which Call
Forwarding Unconditional interacts with other supplementary services. Thus,
if the interactions are described to be \*Qsame as CFU\*U, the CFU text
should be
taken verbatim, except that the expression \*QCall Forwarding Unconditional\*U
should be replaced by \*QCall Forwarding Busy\*U.
.RT
.sp 1P
.LP
3.6.1
\fICall Waiting\fR
.sp 9p
.RT
.PP
Refer to Recommendation I.253, \(sc 1.6.10, interaction with
CFNR.
.RT
.sp 1P
.LP
3.6.2
\fICall Transfer\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc 4).
.RT
.sp 1P
.LP
3.6.3
\fIConnected Line Identification Presentation\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc 4).
.RT
.sp 1P
.LP
3.6.4
\fIConnected Line Identification Restriction\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc 4).
.RT
.sp 1P
.LP
3.6.5
\fICalling Line Identification Presentation\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc 4).
.RT
.sp 1P
.LP
3.6.6
\fICalling Line Identification Restriction\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc 4).
.RT
.sp 1P
.LP
3.6.7
\fIClosed User Group\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc 4).
.RT
.sp 1P
.LP
3.6.8
\fIConference Calling\fR
.sp 9p
.RT
.PP
Same as CFU (see \(sc 4).
.RT
.sp 1P
.LP
3.6.9
\fIDirect\(hyDialling\(hyIn\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 2P
.LP
3.6.10
\fICall Diversion (i.e. Call Forwarding) services\fR
.sp 1P
.RT
.sp 1P
.LP
3.6.10.1
\fICall Forwarding Busy\fR
.sp 9p
.RT
.PP
The invocation of CFB takes precedence over CFNR.
.RT
.sp 1P
.LP
3.6.10.2
\fICall Forwarding No Reply\fR
.sp 9p
.RT
.PP
Not applicable.
.RT
.sp 1P
.LP
3.6.10.3
\fICall Forwarding Unconditional\fR
.sp 9p
.RT
.PP
The invocation of CFB takes precedence over CFNR.
.RT
.sp 1P
.LP
3.6.11
\fILine Hunting\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.bp
.RT
.sp 1P
.LP
3.6.12
\fIThree\(hyParty Service\fR
.sp 9p
.RT
.PP
Refer to Recommendation I.254, \(sc 2.6.10, interaction with
CFNR.
.RT
.sp 1P
.LP
3.6.13
\fIUser\(hyto\(hyUser Signalling\fR
.sp 9p
.RT
.PP
\fIService\ 1:\fR \ A CFNR subscriber who has CFNR activated should not
respond by accepting or rejecting a
User\(hyto\(hyUser Service\ 1
request
until the call is answered. If a call for which User\(hyto\(hyUser Service\
1 was
requested undergoes CFNR, User\(hyto\(hyUser Service\ 1 will not be extended
to the
forwarded\(hyto user.
.PP
\fIService\ 2:\fR \ An outgoing call which meets a called party with CFNR
activated cannot use
User\(hyto\(hyUser Service\ 2
. On CFNR, User\(hyto\(hyUser
Service\ 2 will not be extended to the forwarded\(hyto user.
.PP
\fIService\ 3:\fR \ A CFNR subscriber who has CFNR activated should not
respond by accepting or rejecting a User\(hyto\(hyUser Service\ 3 request
until the
call is answered. If a call which
User\(hyto\(hyUser Service\ 3
was requested undergoes CFNR, User\(hyto\(hyUser Service\ 3 may be extended
to the forwarded\(hyto user if the forwarding party allows it.
.RT
.sp 1P
.LP
3.6.14
\fIMultiple Subscriber Number\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
3.6.15
\fICall Hold\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
3.6.16
\fIAdvice of Charge\fR
.sp 9p
.RT
.PP
Refer to Recommendation I.256, \(sc\(sc 2.1.6.10, 2.2.6.10, 2.3.6.10,
interaction with CFNR.
.RT
.sp 1P
.LP
3.7
\fIDynamic description\fR
.sp 9p
.RT
.PP
Refer to the CFB dynamic description (which covers CFU, CFB, and
CFNR) in \(sc\ 2.
.RT
.sp 2P
.LP
\fB4\fR I.252.4\ \(em
\fBCall Forwarding Unconditional\fR
.sp 1P
.RT
.sp 1P
.LP
4.1
\fIDefinition\fR
.sp 9p
.RT
.PP
Call Forwarding Unconditional (CFU) permits a \*Qserved user\*U (see
\(sc\ 4.2.2) to have the network send to another number all incoming calls
for the served user's ISDN number (or just those associated with a specified
basic
service). The served user's originating service is unaffected. If this
service is activated, calls are forwarded no matter what the condition
of the
termination. Other Call Forwarding services provide for call forwarding
based on condition e.g.\ Call Forwarding Busy (CFB) and Call Forwarding
No Reply
(CFNR).
.PP
\fINote\fR \ \(em\ In normal situations, the CFU service is provided on a per
access basis. (In these situations, there is a one\(hyto\(hyone relationship
between ISDN number and access.) However, the network may recognize multiple
numbers on a single interface; in addition, it may not understand a complete
ISDN number (e.g.\ DDI). In these cases, the CFU service is offered on
the basis of the part of the ISDN number which the network can recognize.
.bp
.RT
.sp 2P
.LP
4.2
\fIDescription\fR
.sp 1P
.RT
.sp 1P
.LP
4.2.1
\fIGeneral description\fR
.sp 9p
.RT
.PP
For a given ISDN number, this service (including options) may be
subscribed to for each basic service to which the user(s) of the number
subscribes, or collectively for all the basic services to which the user(s)
subscribes. Since subscription is on an ISDN number basis, the same Call
Forwarding subscriptions will apply to all terminals using this number.
.PP
\fINote\fR \ \(em\ In this service description, it is assumed that a single
ISDN number is not shared across multiple interfaces. A single ISDN number
may,
however, be shared by multiple terminals on the same interface. Procedures
permitting an ISDN number to be shared across multiple interfaces are for
further study. For multiple access installations, it may be possible for the
user to specify, on activation, if the service is applicable to a specific
access or all accesses associated with that installation.
.PP
The served user can request a different forwarded\(hyto number for each
basic service subscription parameter value to which he has subscribed.
.PP
An indication that the CFU service is activated on a number may, as an
option, be given to the user who has Forwarding activated, each time an
outgoing call is made. This may take the form of a special indication in the
proceed response.
.RT
.sp 1P
.LP
4.2.2
\fISpecific terminology\fR
.sp 9p
.RT
.PP
A \fIserved user\fR is a user of a particular ISDN number who is
requesting that calls to his number be forwarded. This user may also be
referred to as the forwarding user or the called user.
.PP
A \fIforwarded\(hyto user\fR is a user to whom the call shall be
forwarded.
.RT
.sp 1P
.LP
4.2.3
\fIQualifications on the applicability to telecommunication\fR
\fIservices\fR
.sp 9p
.RT
.PP
No restrictions identified.
.RT
.sp 2P
.LP
4.3
\fIProcedures\fR
.sp 1P
.RT
.sp 1P
.LP
4.3.1
\fIProvision/withdrawal\fR
.sp 9p
.RT
.PP
CFU shall be provided after pre\(hyarrangement with the service
provider.
.PP
The service can be offered with three subscription options. Options
apply separately to each basic service subscribed to on each ISDN number.
For each subscription option, only one value can be selected. Subscription
options are summarized below:
.RT
.LP
.sp 1
.LP
\fISubscription options\fR \fIValue\fR Served user receives notification
that call has been forwarded
\(em
No
\(em
Yes, with call offering information (see \(sc 4.3.2.2)
Calling user receives notification that his call has been forwarded
\(em
No
\(em
Yes, with or without forwarded\(hyto user number
Served user receives notification that CFU is currently activated
\(em
No
\(em
Yes
.bp
.sp 2P
.LP
4.3.2
\fINormal procedures\fR
.sp 1P
.RT
.sp 1P
.LP
4..3.2.1
\fIActivationB/FdeactivationB/Fregistration\fR
.sp 9p
.RT
.PP
If the served user has subscribed to CFU, the served user will use the
activation procedure.
.PP
To activate CFU, the served user must supply:
.RT
.LP
1)
the forwarded\(hyto number;
.LP
2)
information as to whether all calls or all calls of a
specified basic service should be forwarded;
.LP
3)
possibly the ISDN number for which CFU should
apply.
.PP
As a network option, verification of the forwarded\(hyto number
should be accomplished, if possible, before accepting the call forwarding
request.
.PP
When the served user so activates CFU, the service provider will
return notification of acceptance or rejection of the request (see Exceptional
procedures, \(sc\ 4.3.3, for a list of possible causes for rejection).
.PP
This notification will include the number of the forwarded\(hyto user to
whom the call forwarding is active. If a single number can be used by more
than one terminal, activation of CFU will be possible from any terminal
which uses this number. As a service option, activation/deactivation may
be restricted to selected terminals (users) (e.g.\ by use of a password).
.PP
CFU can be deactivated in either of two ways. The user can
specifically deactivate the CFU activation. The user can activate CFU for
the specified basic service to another number, thus causing the previous
invocation of CFU to be overridden.
.RT
.sp 1P
.LP
4.3.2.2
\fIInvocation and opertion\fR
.sp 9p
.RT
.PP
The following illustration clarifies the CFU procedures. Assume
that A calls B1, who forwards the call to B2,\ . | | , Bm,\ . | | , Bx.
The final receiver of the call is\ C.
.RT
.LP
.rs
.sp 2P
.ad r
\fBFigure, (N), p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
4.3.2.2.1
\fIServed user Bm's perspective\fR
.sp 9p
.RT
.PP
When CFU is active, all incoming calls will be forwarded without
being offered to the served user Bm. When an incoming call is forwarded
without being offered to the served user, the served user, as a subscription
option,
may receive notification of the call forwarding (but will not be able to
answer the incoming call). This notification is given as soon as the forwarding
attempt is started.
.PP
This notification includes the following information (on the call that
has been forwarded):
.RT
.LP
1)
indication that a call has been forwarded;
.LP
2)
telecommunication service information (e.g. bearer
capability, higher layer compatibility);
.LP
3)
user\(hyto\(hyuser information;
.LP
4)
Bm's number;
.LP
5)
calling party's number A (if CLIP applicable).
.PP
If multiple forwardings have occurred and the served user is
authorized to receive additional information, he may also receive:
.LP
6)
originally called number B1;
.LP
7)
cause for original forwarding;
.LP
8)
last forwarding number B(m\ \(em\ 1);
.LP
9)
cause for last forwarding.
.bp
.sp 1P
.LP
4.3.2.2.2
\fIForwarded\(hyto user C's perspective\fR
.sp 9p
.RT
.PP
The forwarded\(hyto User C will receive an indication that call has
been forwarded.
.PP
As an option he may also receive:
.RT
.LP
1)
originally called number B1;
.LP
2)
cause for original forwarding;
.LP
3)
last forwarding number Bx;
.LP
4)
cause for last forwarding.
.PP
(Depending on the use of other supplementary services, the
forwarded\(hyto user\ C may also receive information such as the calling
party A
number and user\(hyto\(hyuser signalling. See the descriptions of interactions
with other supplementary services.)
.sp 1P
.LP
4.3.2.2.3
\fICalling user A's perspective\fR
.sp 9p
.RT
.PP
As a subscription option, the served user Bm can request that the calling
user receive a notification that the call has been forwarded and, as an
additional subscription option, that notification can include the forwarded\(hyto
number\ B(m+1). Transfer of the forwarded\(hyto user number will not take
place if number restrictions at the forwarded\(hyto user exist.
.RT
.sp 2P
.LP
4.3.3
\fIExceptional procedures\fR
.sp 1P
.RT
.sp 1P
.LP
4.3.3.1
\fIActivation/deactivation/registration\fR \v'2p'
.sp 9p
.RT
.LP
4.3.3.1.1\ \ Call Forwarding Unconditional for all basic services and Call
Forwarding of particular basic services cannot be activated
simultaneously.
.PP
If the system cannot accept an activation request, the served user should
receive a notification that Call Forwarding activation was
unsuccessful. Possible causes are:
.LP
i)
service not subscribed;
.LP
ii)
forwarded\(hyto invalid ISDN number;
.LP
iii)
use of an operator access prefix;
.LP
iv)
forwarded\(hyto ISDN number's telecommunication services
violate subscribed constraints (e.g.\ group restrictions);
.LP
v)
forwarded\(hyto ISDN number is of a free number within the same office
(i.e.\ a number to which no call is chargeable);
.LP
vi)
insufficient information;
.LP
vii)
requested telecommunication service is not provided to the forwarded\(hyto
ISDN number;
.LP
viii)
forwarded\(hyto number is a special service code (e.g.
police);
.LP
ix)
forwarded\(hyto number is served user's number.
.PP
However, the network is not required to validate information
related to the forwarded\(hyto user.
.sp 1P
.LP
4.3.3.1.2
\fIDeactivation\fR
.sp 9p
.RT
.PP
If the user does not specify completely which CFU request is to be deactivated
(e.g.\ the basic service and/or the originator's number), the
network will reject the deactivation request with appropriate cause.
.PP
If the network cannot accept a user's request for deactivation, the
cause will be returned to the user, e.g.\ incorrect origination ISDN number
used.
.PP
If the network deactivates CFU without the served user having
requested deactivation (e.g. when an exceptional condition occurs), the
served user will receive notification along with the cause.
.bp
.RT
.sp 1P
.LP
4.3.3.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
Call forwarding applies only to subscribed basic services. Calls to an
ISDN number requesting a basic service which is not subscribed to, will
never be forwarded.
.PP
Within an ISDN, or tandem ISDNs, the total number of all forwardings for
each call should be limited. The maximum number of such connections should
be limited to a value between 3 and 5 for each call. This is to prevent
infinite looping.
.PP
If the limit is reached and an attempt is made to forward the call an additional
time, then the forwarded call shall be treated as follows:
.PP
If the forwarded call cannot be completed to the forwarded\(hyto
destination, then the network will clear the forwarded leg of the call.
Specifically, if CFU has been invoked, then the call would be cleared back
towards the calling user. If the call has not previously undergone CFNR, the
call will be cleared all the way back to the calling user and the calling
user will be informed that no user is responding. If the call has previously
undergone CFNR the call will only be cleared back as far as the CFNR exchange
and the calling user will, in case of a telephony call, continue to receive\fR
inband ringing tone.
.RT
.sp 2P
.LP
4.3.4
\fIAlternative procedures\fR
.sp 1P
.RT
.sp 1P
.LP
4.3.4.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
None identified.
.RT
.sp 1P
.LP
4.3.4.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
None identified.
.RT
.sp 1P
.LP
4.4
\fINetwork capabilities for charging\fR
.sp 9p
.RT
.PP
This Recommendation does not cover charging principles. Future
Recommendations in the D\(hySeries are expected to contain that information.
.PP
It shall be possible to charge the subscriber accurately for the
service.
.RT
.sp 1P
.LP
4.5
\fIInterworking requirements\fR
.sp 9p
.RT
.PP
If the fowarded\(hyto number is not within the ISDN, then an
interworking situation is said to exist.
.PP
If a forwarded call meets an interworking situation, then an
interworking indication should be sent to the calling party.
.PP
\fINote\fR \ \(em\ The number of times a call has been forwarded once it has
exited the Common Channel Signalling (CCS) network, cannot be limited by the
CCS network.
.RT
.sp 2P
.LP
4.6
\fIInteraction with other supplementary services\fR
.sp 1P
.RT
.sp 1P
.LP
4.6.1
\fICall Waiting\fR
.sp 9p
.RT
.PP
Calling user: No impact i.e. neither supplementary service affects the
operation of the other supplementary service.
.PP
Called user: If a called user has activated CFU, then execution of
that forwarding condition takes precedence over Call Waiting. CFU can be
activated while a call is waiting without changing the state of the waiting
call.
.PP
Forwarded\(hyto user: A forwarded call can invoke Call
Waiting.
.bp
.RT
.sp 2P
.LP
4.6.2
\fICall Transfer\fR
.sp 1P
.RT
.sp 1P
.LP
4.6.2.1
\fITransfer of a Forwarded Call\fR
.sp 9p
.RT
.PP
Calling user: A call which has been forwarded can be transferred by the
calling user.
.PP
Called user: No impact i.e. neither supplementary service affects the operation
of the other supplementary service.
.PP
Forwarded\(hyto user: A call that has been transferred will be forwarded
if the transferred\(hyto user has CFU active and the appropriate forwarding
conditions are met. A call which has been forwarded can by transferred
by the forwarded\(hyto user.
.RT
.sp 1P
.LP
4.6.2.2
\fIForwarding of a Call During Transfer\fR
.sp 9p
.RT
.PP
A call which is being transferred can be forwarded by the party to whom
the call is being transferred.
.RT
.sp 1P
.LP
4.6.3
\fIConnected Line Identification Presentation\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
4.6.4
\fIConnected Line Identification Restriction\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
4.6.5
\fICalling Line Identification Presentation\fR
.sp 9p
.RT
.PP
Called user: If subscribed to, the called user can receive the
Calling Line Identification of all calls which have been forwarded.
.PP
Forwarded\(hyto user: Forwarded\(hyto users having subscribed to CLIP may
receive the calling user's number. If subscribed to by the called user, the
forwarded\(hyto user may receive the called user's number when a call has been
forwarded.
.PP
Forwarded\(hyto users who have subscribed to CLIP may receive the calling
user's number if the calling user has not subscribed/invoked CLIR. In addition,
forwarded\(hyto users subscribing to CLIP may also receive the original
called
user's number and the last forwarding user's number if neither has
subscribed/invoked CLIR (e.g.\ if A calls B1 who forwards A to B2 who forwards
A to B3 who forwards A to C, then C will receive A, B1 and B3's number,
unless A, B1 and B3 have restricted delivery).
.RT
.sp 1P
.LP
4.6.6
\fICalling Line Identification Restriction\fR
.sp 9p
.RT
.PP
Calling user: When the CLIR is applicable and activated, the
Calling Line Identification will not be presented to the forwarded\(hyto user
unless both the forwarding and forwarded\(hyto users are in the override
category. In addition, if the forwarding user is in an override category,
the calling
party's number will be provided in the call offering information. The latter
is a national option.
.RT
.sp 1P
.LP
4.6.7
\fIClosed User Group\fR
.sp 9p
.RT
.PP
CUG restrictions must be met on each leg of the call. In addition, CUG
restrictions must be met end\(hyto\(hyend. In the case of multiple forwarding,
CUG restrictions have to be met in addition at each intermediate forwarding
point.
.bp
.PP
Called user/forwarded\(hyto user: When a call is forwarded, a new check
of the CUG restrictions is made at the \*Qforwarded\(hyto\*U destination.
The CUG
information sent to the \*Qforwarded to\*U destination is the same CUG
information that was sent from the originating network.
.PP
Forwarding (i.e. called) user: Call forwarding can only be activated if
CUG restrictions between the forwarding user and the forwarded\(hyto user
are met.
.RT
.sp 1P
.LP
4.6.8
\fIConference Calling\fR
.sp 9p
.RT
.PP
Calling user: If a conference controller attempts to establish a
conference call and calls a user with call forwarding active, the forwarded\(hyto
user will be alerted and can be added to the conference.
.PP
Called user: No impact i.e. neither supplementary service affects the operation
of the other supplementary service.
.PP
Forwarded\(hyto user: A forwarded\(hyto user can establish a conference
using an existing forwarded call as one of the conference connections.
.PP
A call, which has been forwarded, can be added to an existing
conference by the forwarded\(hyto user.
.RT
.sp 1P
.LP
4.6.9
\fIDirect\(hyDialling\(hyIn\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 2P
.LP
4.6.10
\fICall Diversion (i.e. Call Forwarding) services\fR
.sp 1P
.RT
.sp 1P
.LP
4.6.10.1
\fICall Forwarding Busy\fR
.sp 9p
.RT
.PP
The invocation of CFU takes precedence over CFB.
.RT
.sp 1P
.LP
4.6.10.2
\fICall Forwarding No Reply\fR
.sp 9p
.RT
.PP
The invocation of CFU takes precedence over CFNR.
.RT
.sp 1P
.LP
4.6.10.3
\fICall Forwarding Unconditional\fR
.sp 9p
.RT
.PP
Not applicable.
.RT
.sp 1P
.LP
4.6.11
\fILine Hunting\fR
.sp 9p
.RT
.PP
Calling user: No impact i.e. neither supplementary service affects the
operation of the other supplementary service.
.PP
Called user: Call Forwarding may be assignable to all or part of the hunting
group. When forwarding is only required on part of the hunting group
the forwarding customer must specify, at activation, which access the service
is to be invoked from. Procedures for the operation of this service in
association with part of a hunt group need to be completed. In general, CFU
takes precedence over Line Hunting.
.PP
Forwarded\(hyto user: Forwarded calls will be treated as normal calls
when completing to a multi\(hyline group user.
.RT
.sp 1P
.LP
4.6.12
\fIThree\(hyParty Service\fR
.sp 9p
.RT
.PP
Refer to Recommendation I.254, \(sc 2.6.10, interaction with
CFU.
.bp
.RT
.sp 1P
.LP
4.6.13
\fIUser\(hyto\(hyUser Signalling (UUS)\fR
.sp 9p
.RT
.PP
Call originated by a user with CFU activated: Since CFU does not
affect the forwarding user's ability to make outgoing calls, a user with CFU
activated can send and receive user\(hyto\(hyuser information (UUI) in
association
with an ongoing call or at the set\(hyup of a new call.
.PP
Call incoming to a user with CFU activated:
.PP
During forwarding: Any UUI which accompanies the set\(hyup of the call
will be forwarded along with the forwarded call if both the calling and
forwarding (i.e.\ called) parties have subscribed to service\ 1.
.PP
After forwarding: If the calling party has requested UUS service(s) 1,
2 and/or 3 in his initial call set\(hyup, and if the fowarding (i.e.\ called)
party has subscribed to the same service(s), then that service (those services)
will automatically be extended so that they are available for use between
the
calling party and the forwarded\(hyto party. If the forwarding party does not
subscribe to the same service (set of services), the calling party will be
informed that he can no longer employ the service(s) on this call.
.RT
.sp 1P
.LP
4.6.14
\fIMultiple Subscriber Number\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
4.6.15
\fICall Hold\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
4.6.16
\fIAdvice of Charge\fR
.sp 9p
.RT
.PP
Refer to Recommendation I.256, \(sc\(sc 2.1.6.10, 2.2.6.10,
2.3.6.10.
.RT
.sp 1P
.LP
4.7
\fIDynamic description\fR
.sp 9p
.RT
.PP
Refer to CFB dynamic description (which covers CFB, CFNR and CFU) in \(sc\ 2.
.RT
.sp 2P
.LP
\fB5\fR I.252.5\ \(em
\fBCall Deflection\fR
.sp 1P
.RT
.PP
This service, having been identified, now requires further study; its description
is not yet included.
.RT
.sp 2P
.LP
\fB6\fR I.252.6\ \(em
\fBLine Hunting\fR
.sp 1P
.RT
.sp 1P
.LP
6.1
\fIDefinition\fR
.sp 9p
.RT
.PP
Line Hunting is a supplementary service which enables incoming
calls to a specific ISDN number to be distributed over a group of interfaces.
.PP
\fINote\fR \ \(em\ Development of Line Hunting to cover the case of hunting
on available ISDN numbers, or addresses, rather than on interfaces is a
possible extension of the service.
.RT
.sp 2P
.LP
6.2
\fIDescription\fR
.sp 1P
.RT
.sp 1P
.LP
6.2.1
\fIGeneral description\fR
.sp 9p
.RT
.PP
The interfaces selected for Line Hunting may be contained within
one node, or may encompass more than one node.
.PP
It is the responsibility of the user to provide terminals to his
interfaces for effective operation of the service. The problem of terminal
compatibility in the Line Hunting supplementary service is also the
responsibility of the user of the service.
.bp
.RT
.sp 1P
.LP
6.2.2
\fISpecific terminology\fR
.sp 9p
.RT
.PP
The following specific terminology is used to describe the possible selection
method:
.RT
.LP
.sp 1
\v'6p'
Sequential hunting
\v'6p'
A sequential search is conducted over the members of the group in a
fixed pre\(hyspecified order
Uniform distribution
An equal distribution of calls is provided to idle members of the
group
.PP
The actual algorithm for each hunting method is a network provider option.
.PP
\fINote\fR \ \(em\ The status of an individual channel may be included in the
selection criteria above.
.PP
The selection of an interface is based on the availability of
information channels rather than on the NDUB status. As part of each
applicable bearer service or teleservice, there is already an option specifying
the maximum number of information channels which can be used on the interface
for each ISDN number, all ISDN numbers or subsets of ISDN numbers.
.RT
.sp 1P
.LP
6.2.3
\fIQualifications on the applicability to telecommunication\fR
\fIservices\fR
.sp 9p
.RT
.PP
This supplementary service is considered meaningful when applied
to the speech and 3.1\ kHz audio bearer services and to the Telephony
teleservice. Furthermore, it may also be meaningful when applied to other
services.
.RT
.sp 2P
.LP
6.3
\fIProcedures\fR
.sp 1P
.RT
.sp 1P
.LP
6.3.1
\fIProvision/withdrawal\fR
.sp 9p
.RT
.PP
Line Hunting is offered, with possible subscription options, as a service
to the called party and applied to an ISDN number. For each
subscription the following are specified:
.RT
.LP
.sp 1
\fISubscription options\fR \fIValues\fR Selected Method
\(em
Sequential
\(em
Uniform
Members
\(em
List of 2 or more interfaces
.sp 2P
.LP
6.3.2
\fINormal procedures\fR
.sp 1P
.RT
.sp 1P
.LP
6.3.2.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
Line Hunting is activated on provision and deactivated on
withdrawal.
.RT
.sp 1P
.LP
6.3.2.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
An incoming call to an ISDN number on which Line Hunting is in
operation will be offered to a specific available interface in a pre\(hydefined
manner. The selection of the specified interface may provide for a uniform
distribution of calls or sequential distribution of calls.
.PP
The method of selecting the interface may be either Sequential Hunting
or Uniform Distribution. The selection algorithm may include reference
to the channel status.
.PP
Once an interface has been selected, normal call set\(hyup procedures
apply and Line Hunting procedures are considered complete.
.PP
Outgoing calls from a Line Hunting Group are unaffected by this
service.
.bp
.RT
.sp 2P
.LP
6.3.3
\fIExceptional procedures\fR
.sp 1P
.RT
.sp 1P
.LP
6.3.3.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
None identified.
.RT
.sp 1P
.LP
6.3.3.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
If no interface is available, the Line Hunting service is
unsuccessful and a busy indication is returned to the calling subscriber.
.PP
If no compatible terminal on a selected interface responds, no further
line hunting action is provided and the call is released in the normal
manner.
.PP
If the offered call is rejected at an interface, the call is released with
normal procedures. No further hunting is provided.
.RT
.sp 2P
.LP
6.3.4
\fIAlternative procedures\fR
.sp 1P
.RT
.sp 1P
.LP
6.3.4.1
\fIActivation/deactivation/registration\fR
.sp 9p
.RT
.PP
None identified.
.RT
.sp 1P
.LP
6.3.4.2
\fIInvocation and operation\fR
.sp 9p
.RT
.PP
None identified.
.RT
.sp 1P
.LP
6.4
\fINetwork capabilities for charging\fR
.sp 9p
.RT
.PP
This Recommendation does not cover charging principles. Future
Recommendations in the D\(hySeries are expected to contain that information.
.PP
It shall be possible to charge the subscriber accurately for the
service.
.RT
.sp 1P
.LP
6.5
\fIInterworking requirements\fR
.sp 9p
.RT
.PP
The possibility of a line hunting group including both ISDN and
non\(hyISDN interfaces for a particular Line Hunting service should be
considered. This is for futher study.
.RT
.sp 2P
.LP
6.6
\fIInteraction with other supplementary services\fR
.sp 1P
.RT
.sp 1P
.LP
6.6.1
\fICall Waiting\fR
.sp 9p
.RT
.PP
The Call Waiting service should not be provided to a line in a
hunt group.
.RT
.sp 1P
.LP
6.6.2
\fICall Transfer\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
6.6.3
\fIConnected Line Identification Presentation\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
6.6.4
\fIConnected Line Identification Restriction\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
6.6.5
\fICalling Line Identification Presentation\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary
service affects the operation of
the other supplementary service.
.bp
.RT
.sp 1P
.LP
6.6.6
\fICalling Line Identification Restriction\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary
service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
6.6.7
\fIClosed User Group\fR
.sp 9p
.RT
.PP
When a free line of a Line Hunting Group has been found, any CUG
restrictions must be met before the connection will be established.
.RT
.sp 1P
.LP
6.6.8
\fIConference Calling\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary
service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
6.6.9
\fIDirect\(hyDialling\(hyIn\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 2P
.LP
6.6.10
\fICall Diversion (i.e. Call Forwarding) services\fR
.sp 1P
.RT
.sp 1P
.LP
6.6.10.1
\fICall Forwarding Busy (CFB)\fR
.sp 9p
.RT
.PP
If the outcome of the Line Hunting supplementary service is
unsuccessful (see \(sc\ 6.3.3.2 above), CFB may be invoked.
.RT
.sp 1P
.LP
6.6.10.2
\fICall Forwarding No Reply\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
6.6.10.3
\fICall Forwarding Unconditional\fR
.sp 9p
.RT
.PP
When the CUF and Line Hunting supplementary services are both
subscribed to on the same ISDN number, the CFU supplementary service takes
priority. Further information is contained in the CUF definition
in\ \(sc\ 4.
.RT
.sp 1P
.LP
6.6.11
\fILine Hunting\fR
.sp 9p
.RT
.PP
Not relevant.
.RT
.sp 1P
.LP
6.6.12
\fIThree\(hyParty Service\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
6.6.13
\fIUser\(hyto\(hyUser Signalling\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary
service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
6.6.14
\fIMultiple Subscriber Number\fR
.sp 9p
.RT
.PP
For further study.
.RT
.sp 1P
.LP
6.6.15
\fICall Hold\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.RT
.sp 1P
.LP
6.6.16
\fIAdvice of Charge\fR
.sp 9p
.RT
.PP
No impact, i.e. neither supplementary service affects the operation of
the other supplementary service.
.bp
.RT
.sp 1P
.LP
6.7
\fIDynamic description\fR
.sp 9p
.RT
.PP
The dynamic description of this service is contained in
Figure\ 6/I.252.
.RT
.LP
.rs
.sp 48P
.ad r
\fBFigure 6/I.252, (N), p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp