Question 11/XVII - Support of DTEs (TE2s) with V-Series type interfaces
on an
ISDN, and interworking of DTEs with modems on PSTNs with
TE2s and TE1s on ISDNs
(Continuation of Questions 11 and 24/XVII, 1985-1988)
(Of interest to Study Groups IV, VII, VIII, XI, XVIII)

Considering

(a) that ISDNs will offer the universal interfaces to connect subscriber
terminals according to the reference configurations described in
Recommendation I.411;

(b) that, during the evolution of ISDN, there will exist, for an
indefinite period, DTEs with V-Series type interfaces which have to be
connected to the ISDN;

(c) that, during this evolution of ISDN, there will exist a need for
some terminals on ISDNs (TE1s and adapted TE2s) to interwork with DTEs
connected (with modems) to PSTNs and with DTEs connected to non-ISDN
digital networks;

(d) that Recommendation V.110 describes procedures for adapting TE2s to
an ISDN 64 kbit/s B channel (or 8, 16 or 32 kbit/s sub-rate channels);

(e) that Recommendation V.120 describes procedures for adapting TE2s to
ISDN B and H channels, etc., using an HDLC-based protocol;

(f) that 3.1 kHz bearer capability provides for the connection of modem-
equipped TE2s to an ISDN B channel with a terminal adaptor which
includes the CODEC function;

(g) that Recommendation I.122 describes the additional packet mode
bearer service (APMBS) on which it is desirable to support existing DTEs
with
V-Series type interfaces;

(h) that the D channel signalling protocol is described in
Recommendations I.430, I.431, I.441/Q.921 and I.451/Q.931;

(i) that the I.500-Series includes the requirements to interworking
between ISDNs and existing networks;

(j) that Recommendation T.90 describes a protocol that may be used by
TE1s,

What procedures/protocols should be recommended for the adaption to
ISDNs of DTEs with V-Series type interfaces and what interworking
functions should be defined for the connection of modem-equipped DTEs on
a PSTN with terminals on an ISDN, a PDN or other digital network?

The following are some of the points that should be considered:

1. continuation of the study, associated with Recommendations V.110 and
V.120, of the functionality required for the adaption of existing DTEs
to ISDNs;

2. continuation of the study of multi-modem configurations, for use in
interworking functions, that automatically adapt to the characteristics
of the calling/called modem;

3. continuation of the study of alternate voice/data service using DTE
adaption procedures described in Recommendations V.110 and V.120 in
association with the 64 kbit/s bearer channel as well as using modem-
equipped DTEs in association with the 3.1 kHz bearer channel;

4. what are the appropriate means of multiplexing, both deterministic
(see e.g., I.460 and I.430) and statistical, the output of several TE2s
onto a single ISDN bearer channel?

5. what should be the interworking requirements between V-Series auto-
calling procedures (e.g., V.25bis) and ISDN access signalling
protocols/procedures?

6. what are the appropriate functions that should be recommended for the
adaption of existing TE2s with V-Series interfaces to ISDN channels for
use with the new ISDN APMBS defined in Recommendation I.122?

7. what interworking functions are required for the interconnection of
modem-equipped DTEs on the PSTN with a ISDN. This includes study of
provisions for operation with network-independent clocks and multiple
modem configurations with automatic modem type and rate identification
capabilities?

8. what are the appropriate maintenance/testing methods to be applied in
terminal adaption and interworking configurations?

Note - The study of these points requires close coordination with Study
Groups IV, VII, VIII, XI and XVIII.