) indicates that a signalling system having a lower
capability than ISUP can be selected, provided that the bearer capability
requirements can be met.
.LP
An (R) indicates that the call should be rejected.
.LP
\fINote\ 1\fR
\ \(em\ If another ISDN signalling system is available nationally then this may be selected, provided that it can support the service requested.
.LP
\fINote\ 2\fR
\ \(em\ If a non\(hyISUP route is selected then it must be possible to convey the information transfer capability indication by other means, e.g., path of
entry or \fIJ\fR
bit in TUP.
.LP
\fINote\ 3\fR
\ \(em\ Loss of ISDN supplementary services.
.nr PS 9
.RT
.ad r
\fBTable 3/E.172 [T3.172], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
.sp 4
\fB7\fR \fBNetwork capability\fR
.sp 1P
.RT
.PP
In order to establish if a connection can be made, it is necessary for
the network node to consider the items outlined in \(sc\ 5 together with
the
network elements (see Table\ 4/E.172).
.RT
.LP
.rs
.sp 9P
.ad r
BLANC
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [1T4.172]\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(342p) .
TABLE\ 4/E.172
.TE
.TS
center box;
lw(12p) | cw(42p) | cw(216p) sw(72p) , ^ | ^ | c | c.
} Analogue Digital 24 circuits Digital 32 circuits A\(hyu conversion ADPCM (Note 7) CME/DSI Analog satellite Digital satellite (Note 4) Links (Note 8) Echo control Analog Digital
_
.T&
cw(12p) | lw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^ | l | c | c | c | c | c | c | c | c | c | c | c | c.
P S T N *) Voice \(sr \(sr \(sr \(sr \(sr \(sr (Note 4) \(sr \(sr \(sr \(sr \(sr
Voice band data (Note 5) \(sr \(sr \(sr \(sr \(sr (Note 2) (Note 4) \(sr \(sr No (Note 9) \(sr \(sr
_
.TE
.TS
center box;
cw(12p) | lw(42p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) | cw(24p) , ^ | l | c | c | c | c | c | c | c | c | c | c | c | c
^ | l | c | c | c | c | c | c | c | c | c | c | c | c.
I S D N 64 kbit/s unrestricted No \(sr (Note 1) \(sr No No No No \(sr \(sr No No \(sr
} No \(sr (Note 1) \(sr FS No No No \(sr \(sr FS No \(sr 384 kbit/s unrestricted No \(sr (Note 1) \(sr No No No No \(sr \(sr No No \(sr (Note 3) 1536 kbit/s unrestricted No \(sr (Note 1) No No No No No \(sr \(sr No No \(sr (Note 3) 1920 kbit/s unrestricted No No \(sr No No No No \(sr \(sr No No \(sr (Note 3)
.TE
.nr PS 9
.RT
.ad r
\fBTableau 4/E.172 [1T4.172] A L'ITALIENNE, p. 15\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [2T4.172]\fR
.LP
\fINote\ 1\fR
\ \(em\ Provided the transmission line code is bit sequence independent.
Otherwise only 64\ kbit/s restricted is possible.
.LP
\fINote\ 2\fR
\ \(em\ DSI/CME could be included in a connection element selection for a
voice\(hyband data call. However, the constant activity of voice\(hyband
data would cause permanent trunk/channel assignment for the duration of
the call, thereby reducing the potential DSI gain.
.LP
\fINote\ 3\fR
\ \(em\ Switching at these bit rates is for further study.
.LP
\fINote\ 4\fR
\ \(em\ For voice/speech calls, only single satellite hops are permitted
(see Recommendation E.171). For data calls in the ISDN, the subject is for
further study.
.LP
\fINote\ 5\fR
\ \(em\ The maximum modem bit rate that can be supported depends on the
transmission performance within or between Administrations. The extent
of this support is a bilaterally agreed matter. The network may include
signal processing techniques, provided they are appropriately modified or
functionally removed prior to information transfer.
.LP
\fINote\ 6\fR
\ \(em\ Does not guarantee the support of voice\(hyband data.
.LP
\fINote\ 7\fR
\ \(em\ Currently only 32 kbit/s ADPCM in accordance with
Recommendation G.721.
.LP
\fINote\ 8\fR
\ \(em\ For the number of links in the total connection, see \(sc\ 3 of
this Recommendation, and for satellite links see Recommendation\ E.171.
.LP
\fINote\ 9\fR
\ \(em\ Echo control equipment is disabled by the \*Quser\*U (e.g., modem
tone).
.LP
\fINote\ 10\fR
\ \(em\ The echo control equipment can be disabled either by the \*Quser\*U
or the \*Qexchange\*U. This is for further study.
.LP
\fINote\ 11\fR
\ \(em\ Within national networks it is sometimes possible to provide
digital end\(hyto\(hyend connectivity, this is also possible across international
boundaries subject to bilateral agreement.
.LP
\fINote\ 12\fR
\ \(em\ 2 | (mu | 4 kbit/s service is for further study.
.ad r
\fBTableau 4/E.172 suite (remarques) [2T4.172] A L'ITALIENNE, p. 16\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB8\fR \fBRouting process using S.S. No. 7 ISUP parameter fields\fR
.sp 1P
.RT
.PP
The route selection and subsequent circuit selection will depend on the
outcome of the analysis of the above information. In some cases this
analysis will require the call to be rejected; in others it may be necessary
to select dedicated routes. The actual route selection process using S.S.
No.\ 7
ISUP is shown in Figure\ 1/E.172.
.RT
.LP
.rs
.sp 34P
.ad r
\fBFigure 1/E.172, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB9\fR \fBChange of service during a call\fR
.sp 1P
.RT
.PP
Recommendation\ I.211 identifies one bearer service (as defined in \(sc\
2.1.5 of that Recommendation) for which the value of the information
transfer capability attribute can alternate between speech and 64\ kbit/s
unrestricted. When the user requests this bearer service, the initial value
of this alterable attribute value must be identified in the Q.931 signalling
messages during call set\(hyup. During the call, the user will also use
signalling messages to request a change in absolute value of this attribute
when it is
actually desired; and the network will confirm the request for change (see
Recommendation\ Q.763, \(sc\ 3.4).
.bp
.PP
The capability for change of service during a call can be implemented relatively
easily when no echo control or A\(hy\(*m law conversion is present in the
connection, e.g.,\ intra\(hyEurope. However, the implementation of the
network
capability to support change of service during a call is for further study
in the following areas:
.RT
.LP
\(em
disablement/bypass/introduction of echo control,
.LP
\(em
disablement/bypass/introduction of A\(hy\(*m law conversion,
.LP
\(em
disablement/bypass/introduction of CME/DSI equipment.
.sp 2P
.LP
\fB10\fR \fBPath selection\fR
.sp 1P
.RT
.PP
This is for further study.
.RT
.sp 2P
.LP
\fB11\fR \fBSummary\fR
.sp 1P
.RT
.PP
This Recommendation describes call routing in the ISDN era in terms of
both network design and the route selection process.
.PP
For network design, Table\ 1/E.172 shows the number of links allowed, while
Table\ 4/E.172 should be used to determine which real network components
may comprise the links, depending on the ISDN services they are required
to
support.
.PP
For route selection, Table 2/E.172 shows the types of information
which may be analyzed at various stages of the call routing process. Of
these, two of the most significant for ISDN calls are the S.S. No.\ 7 ISUP
parameters \(em\ transmission medium requirement (TMR) and ISUP preference
indicator. To
further illustrate the use of these parameters, Annex\ C shows a hypothetical
network with examples of route selection for different types of
call.
.RT
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation E.172)
.sp 9p
.RT
.ce 0
.ce 1000
\fBTransmission medium requirement (TMR) values\fR
.sp 1P
.RT
.ce 0
.PP
As outlined in \(sc 5 h), for calls between networks, the TMR
should be set to the minimum transmission resource required to support the
call. This Annex gives TMR values for ISDN services, to be used across
international and internetwork boundaries.
.sp 1P
.RT
.sp 2P
.LP
A.1
\fIBearer services\fR
.sp 1P
.RT
.LP
.sp 1
\fIService\fR
\fITMR value\fR Speech
Speech
3.1 kHz Audio
3.1 kHz Audio
64 kbit/s unrestricted
64 kbit/s unrestricted
Alternate speech, 64\ kbit/s unrestricted
a)\ Initial mode = speech
Speech, 64 kbit/s unrestricted
b)\ Initial mode = 64\ kbit/s unrestricted
64\ kbit/s unrestricted, Speech
.bp
.sp 2P
.LP
A.2
\fITeleservices\fR
.sp 1P
.RT
.LP
.sp 1
\fIService\fR
\fITMR value\fR Telephony
Speech
Telefax (Group\ 4)
64 kbit/s unrestricted
Teletex
64 kbit/s unrestricted
Videotex
For further study
Video telephony
For further study
Interworking from PSTN
.PP
A.3
When interworking from a PSTN, the TMR should normally be set to 3.1\ kHz
audio. However, it is recognized that in some interworking cases
this may be inappropriate (see Recommendation\ I.335). The routing impact of
interworking between networks is for further study.
.sp 9p
.RT
.PP
A.4
Other services are for further study.
.sp 9p
.RT
.ce 1000
ANNEX\ B
.ce 0
.ce 1000
(to Recommendation E.172)
.sp 9p
.RT
.ce 0
.ce 1000
\fBSetting the ISUP preference indicator\fR
.sp 1P
.RT
.ce 0
.PP
The ISUP preference indicator should be set at the originating exchange
according to the following criteria, by analysis of the bearer service
or teleservice request and supplementary service request contained in the\
Q.931 SETUP message, as indicated in \(sc\ 5,\ i).
.sp 1P
.RT
.sp 1P
.LP
B.1
\fIBearer service or teleservice request\fR
.sp 9p
.RT
.LP
\(em
If the BC is 64 kbit/s unrestricted and a telematic teleservice (e.g.,
Teletex) is requested, then the indicator should be set to ISUP \*Qrequired\*U.
This is to ensure that Higher Layer Compatibility (HLC) information can be
passed across the network for terminal compatibility checking
(Recommendations\ I.210 and I.212 refer). (See Note.)
.LP
\(em
For the bearer services speech and 3.1\ kHz audio, the supplementary
service request will determine the value of the ISUP preference indicator.
(See below.)
.LP
\(em
For calls originating from the PSTN, the indicator should be set to
ISUP \*Qnot required\*U.
.bp
.PP
\fINote\fR \ \(em\ For telematic teleservices, ISUP \*Qrequired\*U is suggested
to ensure terminal compatibility with other telematic terminals. ISUP
\*Qrequired\*U calls, however, cannot interwork with dedicated networks.
For cases in which such interworking is desired, networks may set the ISUP
preference
indicator to ISUP \*Qpreferred\*U.
.sp 1P
.LP
B.2
\fISupplementary service request\fR
.sp 9p
.RT
.LP
\(em
For all supplementary services, invoked at initial call request,
except for those shown below, the indicator should be set to ISUP
\*Qpreferred\*U.
.LP
\(em
For the following supplementary services, invoked at initial call
request, the indicator must be set to ISUP \*Qrequired\*U:
.LP
a)
closed User Group (CUG), see Note\ 1,
.LP
b)
reverse charging,
.LP
c)
completion of Calls to Busy Subscribers (CCBS), see
Note\ 2.
.LP
\(em
In order to allow supplementary services invoked after initial call
request to succeed, all calls from ISDN callers should be set to ISUP
\*Qpreferred\*U, as a minimum.
.PP
\fINote\ 1\fR \ \(em\ Non\(hyCUG calls, from subscribers with CUG with
outgoing access, should be set to ISUP Preferred.
.PP
\fINote\ 2\fR \ \(em\ For the CCBS Supplementary service, the call resulting
from acceptance of the CCBS recall may need the ISUP Preference Indicator
to be set to ISUP Required; this is for further study.
.PP
It is recognised that this list of criteria is not exhaustive and
furher study is required on the impact of other supplementary services
on the setting of the ISUP preference Indicator.
.RT
.ce 1000
ANNEX\ C
.ce 0
.ce 1000
(to Recommendation E.172)
.sp 9p
.RT
.ce 0
.ce 1000
\fBUse of S.S. No. 7 ISUP parameters for route selection\fR
.sp 1P
.RT
.ce 0
.PP
In the following examples, calls are offered to Exchange A on the incoming
64\ kbit/s PCM route using S.S. No.\ 7 ISUP signalling (see
Figure\ C\(hy1/E.172).
.sp 1P
.RT
.sp 1P
.LP
\fIExample 1\ \(em\ Telephony call with supplementary service to Exchange B\fR
.sp 9p
.RT
.PP
\fIISUP parameters\fR
.RT
.LP
\(em
TMR = SPEECH
.LP
\(em
ISUP preference indicator = ISUP PREFERRED
.PP
\fIRouting\fR
.RT
.LP
\(em
First choice: Route 1
.LP
\(em
Second choice: Route 2 (but supplementary service may not be provided)
.sp 1P
.LP
\fIExample 2\ \(em\ Telephony call with CUG without outgoing access to\fR
\fIExchange\ B\fR
.sp 9p
.RT
.PP
\fIISUP parameters\fR
.RT
.LP
\(em
TMR = SPEECH
.LP
\(em
ISUP preference indicator = ISUP REQUIRED
.PP
\fIRouting\fR
.RT
.LP
\(em
Route 1 only
.bp
.sp 1P
.LP
\fIExample 3\ \(em\ Teleservice Group 4 facsimile call to Exchange C\fR \v'2p'
.sp 9p
.RT
.PP
\fIISUP parameters\fR
.RT
.LP
\(em
TMR = 64 kbit/s unrestricted
.LP
\(em
ISUP preference indicator = ISUP REQUIRED
.PP
\fIRouting\fR
.RT
.LP
\(em
Route 1 to Exchange B then Route 4 to Exchange C,
provided that:
.LP
a)
all echo control and ADPCM devices are disabled, and
.LP
b)
if Route 4 is a national variant of S.S. No.\ 7 ISUP, it
can support the service request.
.sp 1P
.LP
\fIExample 4\ \(em\ Voice\(hyband data call to Exchange C\fR
.sp 9p
.RT
.PP
\fIISUP parameters\fR
.RT
.LP
\(em
TMR = 3.1 kHz AUDIO
.LP
\(em
ISUP Preference Indicator = ISUP NOT REQUIRED
.PP
\fIRouting\fR
.FS
In this example, it is necessary to remove echo
control and ADPCM devices from all routes used. This may preclude the
use of Route\ 2 if the 3.1\ kHz audio requirement is not indicated to