Question 29/I - Customer control procedures in the PSTN and the ISDN
(revision and continuation of Question 9/II
from 1985-1988)

Considering

(a) that customer performance of basic and supplementary services in
the PSTN and the ISDN depends in part on satisfactory user control
procedures;

(b) that some services in the ISDN may be controlled from various
locations;

(c) that terminals may be portable;

(d) that in the ISDN new kinds of information may need to be given by
the user to the network;

(e) that customers who travel will be less inconvenienced if the
important elements of control procedures do not change from one
country to another;

(f) that control procedures should be optimized in order to avoid
customer difficulties and the resulting economic losses;

(g) that Recommendations E.131 and E.132 were issued to limit
proliferation of control procedure differences for supplementary
services in the PSTN;

(h) that a uniform interpretation of control procedure descriptions will
facilitate the standardization of these procedures;

(i) that interworking will for many years be commonplace between
ISDN and other networks, particularly the PSTN and PDNs;

(j) that customers may be required to provide personal identification;

(k) that draft Recommendation E.331 remains to be completed,

the following Questions should be answered:

1. What elements of customer control procedures for supplementary
services in the PSTN and ISDN should be standardized (described with
use of the specification and description language SDL, if applicable and
helpful)?

2. What principles should be recommended to govern the way services
may be controlled from various locations?

3. What Recommendations are needed to ensure optimal procedures
for ISDN services?

4. What procedures should be recommended to ensure optimal
usability of interworking networks?

5. What minimum procedures can be recommended for setting up ISDN
calls (incomplete draft Recommendation E.331)? (Annexed).

ANNEX

(to Question 29/I)

Draft Recommendation E.331

MINIMUM USER-TERMINAL INTERFACE FOR
ENTERING ADDRESSES INTO AN ISDN TERMINAL

1. General

1.1 Intent

This Recommendation is intended to achieve a degree of world-wide
uniformity in the basic procedure for inputting destination numbers to
an ISDN terminal. It is intended to cover the long-term requirements
rather than to meet intermediate, changeover needs, and it provides for
the same procedure for the two kinds of signalling: functional
signalling
between the terminal and the switch, and stimulus signalling between
the user and the switch (as in the PSTN).

1.2 Background

The customer using a PSTN terminal communicates directly with a
switching machine, but a customer using an ISDN terminal with
functional signalling communicates with the terminal, which delivers
appropriate access- signalling messages to a switch in a different form
from that used between user and terminal (see Figure 1/E.331.)

FIGURE 1/E.331

The relationship of dialling plan and numbering
plan when functional signalling is used

There are many ways by which a user could interact with a terminal to
make his intentions known to it; they will, in practice, vary according
to
features provided and to cost.

The minimum procedures specified here are suitable for use with a
terminal with a dialling  capacity of ten digits and a star (*) and a
square (#), i.e., the signalling ability of a push-button telephone with
tone signalling.

Minimum procedural requirements are in no way intended to preclude
taking advantage of opportunities for new or varied communication
services, or the design of intelligent terminals, or the design of
cooperative procedures for user control. They are intended to allow the
establishment of connections without regard to the type of terminal,
and to achieve as much similarity as possible between different
countries of origination. Application is primarily but not exclusively
aimed at terminals supporting single services, usually voice services.

1.3 Underlying principles

Some aspects of the ISDN, notably the openness of the numbering plan,
the possibility for subaddresses, and the existence of functional
signalling require users to do some things in ways different from how
they are done in the PSTN. However, it is possible and desirable to
preserve some aspects of using the PSTN, and this Recommendation
attempts to do this as it aims at the following goals:

a) unifying the basic MMI procedures world-wide for establishing calls
from ISDN terminals;

b) exercising basic control through the equivalent of the 12-button
telephone pad;

c) assisting in a smooth transition from PSTN to ISDN by preserving
where possible and convenient a similarity to the procedures of the
PSTN; in particular, by allowing a user to set up a simple voice call
with
a procedure differing as little as possible from that used for the same
purpose in the PSTN, and by maintaining a positioning analogy between
the information associated with a destination number and the national
uses of prefixes in the PSTN;

d) having procedures bear a visible relationship to the ISDN numbering
plan;

e) minimizing the number of control actions needed and making it
reasonably easy to remember what to do;

f) having the same procedure for functional signalling (where the
terminal translates into Q.931 protocols) able to serve also for
stimulus
signalling (where the switch makes the translation).

In specifying the basic procedure, this Recommendation recognizes
that an agreed set of principles does not necessarily lead different
people to the same solution, even though one of the principles be that a
single solution is desirable.

2. Minimum terminal capability

2.1 This Recommendation defines a minimum procedure that can be
applied to a terminal having the ability to receive as input the ten
decimal digits and the star (*) and the square (#).

2.2 The minimum procedure enables the user to specify, for an intended
connection:

a) the destination number;

b) the destination sub-address, if any;

c) the numbering plan identification (NPI), if the destination number is
not an ISDN number;

d) the type of number, if necessary.

Future study should add to this list the ability to select a carrier.

2.3 The minimum procedure does not provide for user input of data for
every field required for ISDN addressing. Default values for some fields
must be assigned by the terminal in the case of functional signalling,
or by the switch in the case of stimulus signalling.

3. Numbering Plan Identification (NPI)

3.1 If the called number is in the same numbering plan as the
originating
terminal no NPI need be indicated by the user. The absence of an NPI
should be taken to mean a number in the same numbering plan as the
network to which the terminal is connected.

3.2 The NPI should be indicated, if at all, by a single digit followed
by a star (*)

The recommended digits are:

1for the ISDN/Telephony numbering plan (E.164/E.163)

3for the Data numbering plan (X.121)

4for the Telex numbering plan (F.69)

0for numbering plan unknown

8for a national numbering plan

9for a private numbering plan

Here are two possible alternatives for section 3.2.

3.2 The NPI should be indicated, if at all, by a single digit followed
by a star (*). The digits to be used are for further study.

or

3.2 The NPI should be indicated, if at all, by a single digit followed
by a
star (*). The digits to be used are a national matter.

3.3 The NPI, when input, precedes both TON and the called number.

Note 1 - A separator is used after the NPI to avoid reserving a digit
that
could not be used to start an E.164/E.163 number.

Note 2 - It is expected, that except when the originating terminal is
behind a PBX, the need to indicate a different numbering plan will be
infrequent.

4. Type of number (TON)

4.1 The type of number (TON) should be indicated, if necessary, by up to
three digits; whether or not the choice of digits is a national matter
is
for further study (the following notes would apply if the choice were a
national matter):

Note 1 - Since no character is used to delimit the TON, it should start
with a digit that is not used to start a national E.164/E.163 number.

Note 2 - It is anticipated that administrations will choose to indicate
TONs for international number, national number, and network-specific
number with the same digits that are used as prefixes for analogous
purposes in their PSTNs.

4.2 The absence of a TON should be taken to mean a local subscriber
number.

4.3 The indication of TON should follow the NPI (if any) and precede the
called number.

5. Sub-address and end of dialling

5.1 The start of a dialled sub-address is indicated by a star (or by two
stars: see section 5.5).

5.2 The end of a dialled address (including sub-address, if any: see
Figure 2/E.331) is indicated by a square.

5.3 The sub-address of a terminal intended to be accessible from simple
terminals should contain only digits.

5.4 If dialling stops without the terminating square, the necessary
decision on how to respond and the interval between the last input and
this decision are national matters.

5.5 There are two types of sub-address, user-specified sub-address and
NSAP sub-address, defined by Recommendation I.334. Thus Type of
Sub-address (TOSA), defined by Q.931, or an appropriate distinction of
sub-address, is necessary. The start of an NSAP sub-address is
indicated by two stars, and of a user specified sub-address by one
star .

Note 1 - The square is recommended as an end-of-message character
in Recommendation E.132.

Note 2 - Because of the possible input of a sub-address, a terminal
cannot determine from numbering plan information alone (e.g., fixed-
length numbers) that input has ended.

6. Carrier selection

Where carrier selection is offered, it is desirable that the basic
procedure provide a method for the user to make this selection. This is
a matter for future study.

7. Summary

7.1 The NPI followed by a star should be dialled first, if necessary.

7.2 The type of number should be dialled next, if necessary.

7.3 The address number should be input next, including one or two stars
to begin a sub-address if present, and ending with the terminator
square. Two stars are used if a sub-address is an NSAP sub-address,
one star if it is a user- specified sub-address.

7.4 The general sequence is illustrated in Figure 2/E.331, with examples
of particular sequences in Figures 3 to 7/E.331. In these figures, a
national destination code (NDC) in an ISDN number is analogous to a
trunk code or area code in a PSTN number.

7.5 A method for selecting a carrier is for future study.

FIGURE 2/E.331

The general sequence, illustrated with an ISDN number

Note - It would be seldom, if ever, that every part of this sequence
were
input for a single connection.

1  For the terminating #, "always signalled" means either the # is
signalled,  or that the termination of dialling is deduced by a terminal
or switch.  This interpretation is applicable to the # throughout
Figures 2 to 7/E.331.

FIGURE 3/E.331

Calling a number in the Data numbering plan (X.121)

FIGURE 4/E.331

Calling a local ISDN number without a sub-address

FIGURE 5/E.331

Calling a local ISDN number with an NSAP sub-address

FIGURE 6/E.331

Calling a long-distance national PSTN number

FIGURE 7/E.331

Calling an international ISDN number with a user-specified sub-address