3. Calling Line Identification Presentation (CLIP)
4. Calling Line Identification Restriction (CLIR)
5. Connected Line Identification Presentation (COLP)
6. Connected Line Identification Restriction (COLR)
7. Malicious call identification (under study)
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Recommendation Q.81
NUMBER IDENTIFICATION SUPPLEMENTARY SERVICES
1 Direct Dialling In (DDI)
1.1 wDefinition
Direct Dialling In (DDI) enables a user to call directly another user on a ISPBX or other private
system without attendant intervention.
1.2 wDescription
1.2.1 wGeneral description
A part of the ISDN number, which is significant to the user, is passed to the user. This
supplementary service is based on the use of the ISDN number and does not include sub-addressing.
wNote- A similar method to select a terminal on a passive bus is described in the Stage 1
description of the supplementary service MSN.
wNote- The caller may or may not find the ISDN number in the public directory.
Recommendation E.164 provides the flexibility for administrations to use national numbering plans
of fixed or variable number lengths. This flexibility also applies to DDI numbers,
i.e. even within a given PABX DDI numbers of different lengths may appear.
The number of digits used by a PABX supporting the DDI feature is not necessarily known by their
serving local exchange nor by any other entity of the public network.
The DDI number (fixed or variable length) is sent en-bloc or by over-lap sending from the
exchange to the PABX or other private system which finally and automatically
establishes a connection to the destination without the assistance of an operator.
1.2.2 wQualifications on the applicability to Telecommunication Services
Fascicle VI.1 - Rec. Q.81 1.
No restrictions.
1.3 wDerivation of a functional model(Step 1)
1.3.1 wFunctional model description
Two functional models are used to show the different requirements of DDI.
Functional model 1 represents the situation where DDI is used to address a terminal on a single
ISPBX connected to the public network.
Functional model 2 describes the situation where DDI is used to address a terminal within a
private network consisting of several PBXs.
Although functional model 1 can be seen as a special application of model 2 it is preferred to
describe the two models independently to show different situations more clearly.
FIGURE 1-1/Q.81
Two functional models for DDI
1.3.2 wDescription of the functional entities
FE1: Call control agent of the calling user
FE2: Call control entity of the calling user
FE3: DDI Access control to the private network (located in the public network)
FE4: DDI Service control for the called user and access control in the private network
FE5: Call control agent of the called user
FE6: DDI Access control in the private network
FE7: DDI Service control in the private network for the called user.
1.3.3 wRelationship to basic service
The call setup procedures in the public network are mainly the same as for the basic service.
FE1 and FE2 therefore have the same functionality as CCA and CC. r1 and r2 correspond to r1 and
r2 in the basic service.
FE3 includes specific functionality of DDI in the relationship r3.
FE4, FE6 and FE7 are entities in a private network that are only specified here as far as they
are influenced by r3. The same applies for r4 and r5.
1.4 wInformation flow diagrams (Step 2)
2 Fascicle VI.1 - Rec. Q.81
1.4.1 wDiagrams
The diagrams for model 1 are shown in Figure 1-2/Q.81.
Insert diagram
1.4.1.1 wDiagrams for model 2
Insert diagram
Notes
2a) Optional signalling information which may be used to acknowledge seizure and/or for B channel
negotiation.
2b) Optional signalling information which may be used to indicate complete address information.
2c) If not already sent, this signalling information may be sent to the originating user to
indicate complete address information.
2d) If the PABX recognizes the receipt of complete address information, this signalling
information may be sent.
2e) On receipt of complete address information, this signalling information may be generated by
the sub-PABX. If already sent by the PABX, it will not be transferred to
the originating user.
3) Instead of ALTERTING, a CONNECT signalling information may be sent directly in case of an
automatically responding terminal.
4) Optional early switch through of backward transmission path.
1.4.2 wDefinitions
The definitions for ACK, ADDRESS INFO, PROCEEDING, REPORT and SETUP are the same as for the basic
service.
1.4.2.1.1 Meaning of [PROGRESS]
PROGRESS can be sent from the entity serving the called user to indicate that sufficient ADDRESS
INFO was received to address a user terminal or access line. It is an unconfirmed
information flow.
1.4.2.2.1 Information content of [PROGRESS]
Fascicle VI.1 - Rec. Q.81 3.
B-channel information in r3 if not yet included in a previous sent information element.
1.5 wSDL diagrams of functional entities (Step 3)
SDL diagrams are provided for FE3 covering the aspects of both functional models and giving the
relation between r2 and r3. FE1 and FE2 are, as said, already covered by the basic
procedures so that all aspects of DDI, that are relevant for the public network, are
covered in these diagrams.
In the SDL diagrams only those procedures are described that deviate from the basic procedures.
wNote 1- Through connection is generally only done when the setup confirmation is received from
the called user. This is described in option A.
In specific national applications through connection may already be done in an earlier point in
time. This is covered in options B1 or B2 and requires further considerations.
wNote 2- Negotiation of a B channel is not necessarily an independent information flow. It can
be combined with the first backward information flow that is required for call
control. This information flow can be PROGRESS, REPORT (alerting) or SETUP.
1.6 wFunctional entity actions (Step 4)
1.6.1 wSpecific actions in FE3
1.6.1.1 Channel selection
Negotiation for the selection of a B-channel will be permitted between the network and the PABX.
The selection procedure is as follows:
a) in the SETUP Request, the network will indicate one of the following:
1) channel is indicated, no acceptable alternative; or
2) channel is indicated, any alternative is acceptable; or
3) any channel is acceptable.
b) In cases 1) and 2), if the indicated channel is acceptable and available, the PABX selects it
for the call.
In case 2), if the PABX cannot grant the indicated channel, it selects any other available B-
channel and identifies that channel in the first information sent in
response to the SETUP Indication.
In case 3), the PABX selects any available B-channel and identifies that channel in the first
information sent in response to the SETUP Indication.
c) If no channel identification information element is present in the first response, the B-
channel indicated in the SETUP Request will be assumed.
If the B-channel indicated in the first response is unacceptable to the network, it will
clear the call.
d) When a B-channel has been selected by the PABX that channel may be connected by the PABX.
e) In case 1), if the indicated B-channel is not available, or in cases 2), 3), if no B-channel
is available and the PABX cannot proceed with the offered call, the PABX
clears the call.
4 Fascicle VI.1 - Rec. Q.81
The preferred solution for B-channel selection is alternative 1): B-channel is selected by
exchange B.
1.6.1.2 Through connection
The general time for through connection in FE3 is, when setup is confirmed by the called user.
This prevents fraudulent use of the connection without charging.
As a consequence of this procedure all tones and announcements during call setup have to be
generated in the public network.
As an alternative some network providers may allow for an early through connection.
1.6.2 wSpecific actions in FE6 and FE7
1.6.2.1 Through connection
In case of an ISDN terminal or sub-PABX connected to the PABX, the through connection of the B-
channel in the PABX is done with the sending of SETUP to the terminal/sub-PABX. In
the sub-PABX the through connection is done with the sending of SETUP to the terminal.
In the terminal the through connection is done at the receipt of CONNECT ACKNOWLEDGE
from the PABX/sub-PABX.
In case of an analogue terminal connected to the ISDN PABX/sub-PABX the through connection of the
B-channel in the terminal is done with the sending of CONNECT to the ISDN PABX/sub-PABX. In the ISDN PABX/sub-PABX the through connection is done at the receipt of
SETUP Confirmation from the terminal. Note that this case is for further study.
1.7 wAllocation of functional entities to physical locations
The mapping between functional entities and their possible physical locations is given in the
