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3.5 Backward set-up request message
The following type of backward set-up request message is specified and is
identified by one of the heading codes H1. The other H1 codes in this message
group are spare.
3.5.1 General request message
The basic format of the general request message is shown in Figure
10/Q.723.
Figure 10/Q.723 - CCITT 35570
The following codes are used in the fields of the general request message:
a) Label: see S 2
b) Heading code H0 is coded 0011
c) Heading code H1 is coded 0001
d) Request type indicators
bit A: calling party category request indicator
0 no calling party category request
1 calling party category request
bit B: calling line identity request indicator
0 no calling line identity request
1 calling line identity request
bit C: original called address request
0 no original called address request
1 original called address request
bit D: malicious call identification indicator (national option)
0 no malicious call identification encountered
1 malicious call identification encountered
bit E: hold request indicator
0 hold not requested
1 hold requested
bit F: echo suppressor request indicator
0 no outgoing half echo suppressor requested
1 outgoing half echo suppressor requested
bit GH: spare
3.6 Successful backward set-up information messages
The following types of successful backward set-up information messages are
specified and are each identified by a different heading code H1:
- address-complete message
- charging message.
3.6.1 Address-complete message
The basic format of the address-complete message is shown in Figure
11/Q.723.
Figure 11/Q.723 - CCITT 35580
The following codes are used in the fields of the address-complete
PAGE18 Fascicle VI.8 - Rec. Q.723
message:
a) Label: see S 2
b) Heading code H0 is coded 0100
c) Heading code H1 is coded 0001
d) Message indicators
bits B A: type of address-complete signal indicators
0 0 address-complete signal
0 1 address-complete signal, charge
1 0 address-complete signal, no charge
1 1 address-complete signal, payphone
bit C: subscriber-free indicator
0 no indication
1 subscriber-free
bit D: incoming echo suppressor indicator
0 no incoming half echo suppressor included
1 incoming half echo suppressor included
bit E: call forwarding indicator
0 call not forwarded
1 call forwarded
bit F: signalling path indicator
0 any path
1 all signalling system No. 7 path
bits G H: spare, for national use (may be used to indicate call
redirection, holding of the connection or the end-to-end
signalling method to be used).
Note - The address-complete signal without qualification is classified for
the time being in the basic national category of signals. The use of this signal
in the international network is for further study.
3.6.2 Charging message (see Note)
The basic format of the charging message is shown in Figure 12/Q.723.
Figure 12/Q.723 - CCITT 35585
The following codes are used in the fields of the charging message:
a) Label: see S 2
b) Heading code H0 is coded 0100
c) Heading code H1 is coded 0010
d) Charging information
(Possible formats and codes of the charging information field are shown in
Annex A.)
Note - The charging message is classified, for the time being, in the
basic national category of messages. The use of this message in the international
network is for further study.
3.7 Unsuccessful backward set-up information messages
Fascicle VI.8 - Rec. Q.723 PAGE31
3.7.1 Simple unsuccessful backward set-up information message
The basic format of the simple unsuccessful backward set-up information
message is shown in Figure 13/Q.723.
Figure 13/Q.723 - CCITT 35570
The following codes are used in the fields of the simple unsuccessful
backward set-up information message.
a) Label: see S 2
b) Heading code H0 is coded 0101
PAGE18 Fascicle VI.8 - Rec. Q.723
c) Heading code H1 contains signal codes as follows:
0000 spare
0001 switching-equipment-congestion signal
0010 circuit-group-congestion signal
0011 national-network-congestion signal
0100 address-incomplete signal
0101 call-failure signal
0110 subscriber-busy signal (electrical)
0111 unallocated-number signal
1000 line-out-of-service signal
1001 send-special-information-tone signal
1010 access barred signal
1011 digital path not provided signal
1100 misdialled trunk prefix signal (for national use)
1101 ü
to ì spare
1110 Φ
3.7.2 Extended unsuccessful backward set-up information message
The basic format of the extended unsuccessful backward set-up information
message is shown in Figure 13a/Q.723.
Figure 13a/Q.723 - CCITT 85960
The following codes are used in the fields of the extended unsuccessful
backward set-up information message:
a) Label: see S 2
b) Heading code H0 is coded 0101
c) Heading code H1 contains signal code 1111
d) Octet indicator
bi D C B A unsuccessful indicator
ts
0 0
Fascicle VI.8 - Rec. Q.723 PAGE31
0 0 spare
0 0 0 1 subscriber busy
0 0 1 0 ü
t ì spare
o
1 1 1 1 Φ
G H F E spare
:
PAGE18 Fascicle VI.8 - Rec. Q.723
e) Signalling point code
The point code of the signalling point in which the message is
originated.
3.8 Call supervision message
The basic format of the call supervision message is shown in Figure
14/Q.723.
Figure 14/Q.723 - CCITT 35570
The following codes are used in the fields of the call supervision
message:
a) Label: see S 2
b) Heading code H0 is coded 0110
c) Heading code H1 contains signal codes as follows:
0000 answer signal, unqualified
0001 answer signal, charge
0010 answer signal, no charge
0011 clear-back signal
0100 clear-forward signal
0101 re-answer signal
0110 forward-transfer signal
0111 calling party clear signal (national option)
1000 ü
to ì spare
1111 Φ
3.9 Circuit supervision message
The basic format of the circuit supervision message is shown in Figure
15/Q.723.
Figure 15/Q.723 - CCITT 35570
Fascicle VI.8 - Rec. Q.723 PAGE31
The following codes are used in the fields of the circuit supervision
message:
a) Label: see S 2
b) Heading code H0 is coded 0111
c) Heading code H1 contains signal codes as follows:
0000 spare
0001 release-guard signal
0010 blocking signal
0011 blocking-acknowledgement signal
0100 unblocking signal
0101 unblocking-acknowledgement signal
0110 continuity-check-request signal
0111 reset-circuit signal
1000 ü
to ì spare
1111 Φ
3.10 Circuit group supervision message
The basic format of the circuit group supervision message is shown in
Figure 16/Q.723:
Figure 16/Q.723 - CCITT 85970
The following codes are used in the fields of the circuit group
supervision message:
a) Label: see S 2
The following interpretations apply to the CIC given in the label:
i) If the range field is not coded all zero the CIC given in the label
is the first CIC within the circuit group or the first CIC within
that part of the circuit group.
ii) If the range field is coded all zero (national option) the CIC
given in the label is a representative CIC within the circuit
group.
b) Heading code H0 is coded 1000
c) Heading code H1 contains message codes as follows:
0000 spare
0001 Maintenance oriented group blocking message
0010 Maintenance oriented group blocking-acknowledging message
0011 Maintenance oriented group unblocking message
0100 Maintenance oriented group unblocking-acknowledgement message
0101 Hardware failure oriented group blocking message
0110 Hardware failure oriented group blocking-acknowledge message
0111 Hardware failure oriented group unblocking message
1000 Hardware failure oriented group unblocking-acknowledgement
PAGE18 Fascicle VI.8 - Rec. Q.723
message
1001 Circuit group reset message
1010 Circuit group reset-acknowledgement message
1011 Software generated group blocking message (national option)
1100 Software generated group blocking-acknowledgement message
(national option)
1101 Software generated group unblocking message (national option)
1110 Software generated group unblocking-acknowledgement message
(national option)
1111 spare
d) Range: in principle, two different codings are possible:
i) not all zero: The message is related to a whole circuit group or a
part thereof, and includes a status field unless the message is the
circuit group reset message. The number of consecutive circuits to
be handled is indicated by the value contained in the range field
increased by 1. The CIC of the first circuit to be handled is given
in the label. The number of circuits to be indicated is 2 (range
value 1) to 256 (range value 255).
ii) all zero1) (national option): The message is related to a
pre-determined circuit group. No status field is included. In this
case the circuit group is addressed by means of a representative
CIC within the circuit group.
Note - In national networks, the range field may not be used if only the
concept of pre-determined circuit group applies.
e) Status field
All circuit group supervision messages except the circuit group reset
message include a status field containing status indicator bits when
the range field is not coded all zero. The number of status indicator
bits is indicated by the value given in the range field increased by
one.
The status field contains up to 256 one bit status indicators. The
first status indicator bit is related to the circuit indicated by the
CIC contained within the label, the second one is related to the
circuit address by the CIC contained in the label increased by 1.
Figure 17/Q.723 - CCITT 73570
The CIC of the last circuit concerned is obtained by adding the value
given in the range field to the CIC in the label. The status field consists of an
integral number of octets. Bits within the last octet that are not used as status
indicators are filled with zeros.
The status indicator bits are coded as follows:
- in all group blocking messages (MGB, HGB, SGB)
1 blocking
0 no blocking
1) Range value zero is only for national use.
Fascicle VI.8 - Rec. Q.723 PAGE31
- in all group blocking-acknowledgement messages (MGB, HBA, SBA)
1 blocking acknowledgement
0 no blocking acknowledgement
- in all unblocking messages (MGU, HGU, SGU)
1 unblocking
0 no unblocking
- in all group unblocking-acknowledgement messages (MUA, HUA, SUA)
1 unblocking acknowledgement
0 no unblocking acknowledgement
- in the circuit group reset-acknowledgement message (GRA)
1 blocking for maintenance reasons
0 no blocking for maintenance reasons
3.11 Circuit network management messages
The following type of circuit network management message is specified and
identified by one of the heading codes H1. Unallocated H1 codes in this message
group are spare.
3.11.1 Automatic congestion control information message
The basic format of the automatic congestion control (ACC) information
message is shown in Figure 18/Q.723:
Figure 18/Q.723 - T1109900-88
The following codes are used in the fields of the automatic congestion
control information message.
a) Label: see S 2
b) Heading code H0 is coded 1001
c) Heading code H1 is coded 0001
d) Message indicators
bi B A ACC information
ts
0 0 spare
0 1 congestion level 1
PAGE18 Fascicle VI.8 - Rec. Q.723
1 0 congestion level 2
1 1 spare
bits HGFEDC spare
ANNEX A
(to Recommendation Q.723)
Charging messages
A.1 Introduction
The application of Signalling System No. 7 in national networks was
recognized from the beginning of the discussions about the signalling system. The
result of this can be found throughout the specifications especially in those
Recommendations dealing with the TUP. One of the points which is particularly of
interest for an Administration is the possibility of transfer of charging
information. Signalling System No. 7 allows for such a feature for charging a
calling subscriber by defining a specific charging message as indicated in S
3.6.2. However, the detailed format, coding and related procedures are not given,
mostly because this matter is very dependent on the circumstances within a
specific national network. The following examples illustrate a particular
implementation in a national network for telephony without exclusion of other
possible solutions.
A.2 Starting points
Before describing in detail the messages involved, a number of starting
points have to be adopted.
a) The first No. 7 exchange performs metering according to all possible
tariffs.
b) The determination of a particular tariff is performed in a point
somewhere in the network.
c) The receipt of messages containing charging information should be
acknowledged within the call control procedures.
d) At dedicated moments the actual charging should be adapted.
e) A variety of charging possibilities should be available.
The effect of these starting points is:
a) the actual generation of charging units according to a particular
tariff is always performed at the lowest level of the national public
telephone network (local exchange);
b) the determination of tariffs for local and trunk calls is carried out
in the local exchange and for international calls in the international
exchange; however, also the use of a centre for determination of all
kinds of tariffs is possible;
c) the transmission of charging information is assured at the highest
level of the call control procedures and possibly inhibits call
completion without receipt of charging information;
d) calls of long duration can be subject to different charging rates;
e) the application of charge free calls, specific charge on answer, time
dependent charging during a call, additional (specific) charge during a
call and a combination of these.
A.3 Messages and procedures
To meet all the above mentioned requirements a number of messages are
defined.
A.3.1 Charging message
This message has to be sent for any call, charge free or not. In the
procedure this is covered by the fact that the charging message has to be
received during call set up before receipt of the address complete message.
If not, then the call should be cleared immediately.
The content of the message will vary depending on the actual tariff and
this is indicated by a number of indicators indicating the presence of certain
fields in the message.
Possible contents:
a) charge band
The indication of a certain charge band should allow the receiving
exchange to charge a call according to a certain tariff including
possible switchover times to higher or lower rates. This method results
in a simple message but requires the receiving exchange to have all the
information available related to all possible charge bands, national
and international.
Fascicle VI.8 - Rec. Q.723 PAGE31
b) explicit charging indication
In this case the message contains explicit indications of details of
the tariff viz.
- number of charging units on answer (packet)
- time dependent tariff(s)
- possible switchover time.
This method results in a more complex message but does not require the
permanent storage of any charging information.
A.3.2 Change message
A consequence of the adoption of the method with explicit charging
indication (S A.3.1 b)) is the necessity to allow for tariff switchover for calls
of very long duration or for calls which are answered just after the switchover
time given in the message described in S A.3.1 b). The content of such at message
is rather simple because it only contains the new applicable tariff and the
actual switch-over time.
The procedure to acknowledge the receipt of the message cannot be found in
the normal call control procedure, therefore an acknowledgement message (see S
A.3.5) in the forward direction is used. If this acknowledgement message is not
received within a certain time, the change message has to be repeated.
A.3.3 Collection charging
For a variety of reasons it might be necessary to charge a subscriber
during the call a certain amount. For this purpose a message is used indicating
the number of charging units related to the amount for which the subscriber has
to be charged.
The procedure to assure the receipt of this message is the same as
described in S A.3.2 above. A possible further collection charging message should
not be sent before receipt of the acknowledgement message and the charging
confirmation message (see S A.3.4 charging confirmation).
A.3.4 Charging confirmation
In relation with the message described in S A.3.3 a message in the forward
direction is required indicating how many charging units actually are charged to
the subscriber. This number should match to the number given in the collection
charging message, otherwise it must be concluded that for some reason the order
is not executed, e.g., a certain service should now be withheld to be furnished
to the subscriber.
Again the procedure is the one as described in S A.3.2 above but in the
opposite direction.
A.3.5 Acknowledgement
To acknowledge the receipt of the messages described in SS A.3.2, A.3.3
and A.3.4, an acknowledgement message is used in both directions only indicating
the receipt of the related message.
A.4 Formats and codes
A.4.1 Charging messages
A.4.1.1 Charge band
TABLEAU CCITT 86010
PAGE18 Fascicle VI.8 - Rec. Q.723
- Charge band
A charge indicates the combination of tariffs including switch-over
times which is applicable for a certain period (e.g., day or week).
A.4.1.2 Explicit charging indication
tableau ccitt 86020
- Message indicators
bit A: tariff indicator current tariff (A)
0 packet charging field and tariff indicators current tariff (A)
not present
1 packet charging field and tariff indicators current tariff (A)
present
bit B: tariff factor current tariff (A)
0 tariff factor field current tariff (A) not present
1 tariff factor field current tariff (A) present
bit C: tariff indicator next tariff (B)
0 packet charging field and tariff indicators next tariff (B) not
present
1 packet charging field and tariff indicators next tariff (B)
present
bit D: tariff factor next tariff (B)
0 tariff factor field next tariff (B) not present
1 tariff factor field next tariff (B) present
bit H-E spare
- Packet charging field
0000
| number of charging units on answer
1111
- Tariff indicators
0000 tariff scale 0 (no time dependent tariff)
0001 tariff scale I
| | every scale indicates a certain step in
seconds or parts thereof
1111 tariff scale XV
- Tariff factors
If a call is charge free (A = B = C = D = 0) only the message indicator
octet is present.
If a call is charge free from the start but may become chargeable (A =
1, B = 0, C = 1, D = 0/1), the packet charging field for the current
tariff is 0000 and the tariff indicator for the current tariff
indicates scale 0.
If a call is chargeable from the start but may become charge free (A =
1, B = 0/1, C = 1, D = 0) the packet charging field for the next tariff
is 0000 and the tariff indicator for the next tariff indicates scale 0.
If a call is chargeable according to only one tariff (A = 1, B = 0/1, C
= 0, D = 0), also the time indicator is not present in the message. The
actual tariff is determined by multiplication of the step indicated by
the tariff indicator with the tariff factor which gives then a specific
charging unit interval in seconds.
- Time indicator
000000 spare
Fascicle VI.8 - Rec. Q.723 PAGE31
000001 00.30 h
000010 01.00 h
| |
| |
110000 24.00 h
A.4.2 Tariff change message
Tableau ccitt 86030
Message indicator
Bit A: tariff factor next tariff
0 tariff factor field next tariff not present
1 tariff factor field next tariff present
Bits D-B: spare
- Tariff indicator, tariff factor and time indicator: see S A.4.1.2
A.4.3 Collection charging message
tableau ccitt 86040
The collection field contains the number of charging units which are to be
charged to the calling subscriber. The field has a length of 8 bits so a maximum
of 256 units is possible.
A.4.4 Charging confirmation message
tableau ccitt 86040
- Heading code H1
H1 = 0101 confirmation of packet charging
H1 = 0110 confirmation of collection charging
- Charging unit field
Number of charging units which actually are charged to the calling
party
A.4.5 Acknowledgement message
tableau ccitt 86050
- Heading code H1
H1 = 1000 acknowledgement receipt of tariff review, collection
charging or charging confirmation message
References
[1] CCITT Recommendation Characteristics of primary PCM multiplex equipment
operating at 2048 kbit/s, Rec. G.732.
[2] CCITT Recommendation Characteristics of 2048-kbit/s frame structure for
use with digital exchanges, Vol. III, Rec. G.734.
[3] CCITT Recommendation Second order PCM multiplex equipment operating at
8448 kbit/s, Rec. G.744.
[4] CCITT Recommendation Characteristics of 8448-kbit/s frame structure for
use with digital exchanges, Rec. G.746.
[5] CCITT Recommendation Language digit or discriminating digits, Rec. Q.104.
PAGE18 Fascicle VI.8 - Rec. Q.723
[6] CCITT Recommendation Signalling Connection Control Part, Recs.
Q.711-Q.714.
Fascicle VI.8 - Rec. Q.723 PAGE31