Change of services (Note 7) (Should be defined) (Should be defined)
.TE
.LP
\fINote\ 1\fR
\ \(em\ For charging use.
.LP
\fINote\ 2\fR
\ \(em\ For discrimination of priority call/ordinary call.
.LP
\fINote\ 3\fR
\ \(em\ These indicators are used to identify:
.LP
1)
international incoming call,
.LP
2)
available end\(hyto\(hyend signalling system,
.LP
3)
charged call/noncharged call.
.LP
\fINote\ 4\fR
\ \(em\ When a satellite circuit is employed for an interworking call at the interworking point, this information is processed at the IWF. If a satellite
circuit is not employed for a call, this information is transferred through the IWF transparently.
.LP
\fINote\ 5\fR
\ \(em\ There may be cases where the terminal compatibility information
is processed (see \(sc\ 5.4).
.LP
\fINote\ 6\fR
\ \(em\ This information is used only when access charging is necessary.
.LP
\fINote\ 7\fR
\ \(em\ All ISDNs do not necessarily provide identical services (or
connection types). When a change of services occurs at the IWF, the network
should send the indication for change of services and may solicit acceptance of change of services to a calling user in certain cases (see \(sc\ 5.3.1 of this
Recommendation).
.LP
\fINote\ 8\fR
\ \(em\ The information in this category is transferred through the IWF
transparently.
.nr PS 9
.RT
.ad r
\fBTableau 1/I.520 [T1.520], p. 2\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T2.520]\fR
.ce
TABLE\ 2/I.520
.ce
\fBInformation required for IWF between ISDNs for circuit
.ce
mode supplementary services\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(36p) | cw(68p) | cw(62p) | cw(62p) .
Category Required information Q.931 information element Q.763 parameter name
_
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
ii Supplementary service request {
Network specific facility
Key pad facility
Feature activation
Feature indication
} (Should be defined)
_
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
Progress indicator Progress indicator Access transport
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
iii Suspend/Resume indicator Notification indicator Suspend/Resume indicator
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 2/I.520 [T2.520], p. 3\fR
.ad b
.RT
.ce
\fBH.T. [T3.520]\fR
.ce
TABLE\ 3/I.520
.ce
\fBInformation required for IWF between ISDNs for packet mode
.ce
\fBbearer services (in\(hyband signalling)\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(36p) | cw(68p) | cw(62p) | cw(62p) .
Category Required information Rec. X.25 information Rec. X.75 information
_
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
i {
Transit network identification
} RPOA selection {
Transit network identification
}
_
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
Packet type Packet type identifier Packet type identifier
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
Logical channel number Logical channel number Logical channel number
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
Called party number Called DTE address Called DTE address
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
Throughput class Throughput class negotiation Throughput class indication
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
ii Window size {
Flow control parameter negotiation
} Window size indication
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
Packet size {
Flow control parameter negotiation
} Packet size indication
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
Call identifier (Unnecessary) Call identifier
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
Transit delay selection {
Transit delay indication/selection
} Transit delay indication
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
{
User\(hyto\(hyuser information
} Fast select identifier Fast select indication
_
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
Calling party number Calling DTE address Calling DTE address
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
Terminal compatibility (Call user data) (Should be defined)
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
iii Subaddress {
Calling address extension
Called address extension
} {
Calling address extension
Called address extension
}
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
Cause Diagnostic code Diagnostic code
_
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
Cause for interworking (Should be defined) (Should be defined)
.T&
cw(36p) | lw(68p) | lw(62p) | lw(62p) .
iv Charging Charging information (Should be defined)
.TE
.LP
\fINote\fR
\ \(em\ The relationship between X.25 facilities and ISDN supplementary
services is for further study.
.nr PS 9
.RT
.ad r
\fBTableau 3/I.520 [T3.520], p. 4\fR
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB4\fR \fBDescription of \fR \fBISDN\(hyISDN interworking configurations\fR
.sp 1P
.RT
.sp 1P
.LP
4.1
\fIISDN\(hyISDN interface where circuit mode bearer services are provided\fR
\fIby both ISDNs\fR
.sp 9p
.RT
.PP
See Figure 2/I.520.
.RT
.LP
.rs
.sp 8P
.ad r
\fBFigure 2/I.520, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
4.1.1
\fIBearer services\fR
.sp 9p
.RT
.PP
Individual bearer service categories are defined in the
I.230\(hySeries of Recommendations.
.PP
Layer 1 interworking specifications are recommended in
Recommendation\ I.511. Layers\ 2 and 3 in the U\(hyplane are passed
transparently.
.RT
.sp 2P
.LP
4.1.2
\fISupplementary services\fR
.sp 1P
.RT
.sp 1P
.LP
4.1.2.1
\fIOther than user\(hyto\(hyuser signalling\fR
.sp 9p
.RT
.PP
For supplementary services other than user\(hyto\(hyuser signalling, call
control information is transferred via Signalling System\ No.\ 7 across
the N\dx\ureference point. The interface for user information transfer
is not different from that of basic bearer services.
.RT
.sp 1P
.LP
4.1.2.2
\fIUser\(hyto\(hyuser signalling services\fR
.sp 9p
.RT
.PP
There are two methods of transferring user\(hyto\(hyuser signalling. One
is transfer of user\(hyto\(hyuser signalling within Q.931 call control
messages which have been mapped into Signalling System\ No.\ 7 messages
and then are conveyed
via the Signalling System\ No.\ 7 network. The other is transfer of user\(hyto\(hyuser
signalling within stand alone USER INFO messages (which have been mapped
into Signalling System\ No.\ 7 messages and then are conveyed via the Signalling
System\ No.\ 7 network), or optionally may be transferred via packet handlers
(PHs) in some ISDNs. In the case where user\(hyto\(hyuser signalling is
transferred between packet handlers (PHs) in both ISDNs, the X.75 protocol
may be applied to the internetwork interface to transfer user\(hyto\(hyuser
signalling. In the case where user\(hyto\(hyuser signalling is transferred
via Signalling System\ No.\ 7
networks in both ISDNs or at least in one ISDN, the Signalling System\ No.\ 7
protocol should be applied to the internetwork interface for user\(hyto\(hyuser
signalling.
.RT
.sp 1P
.LP
4.1.3
\fISignalling System No. 7 for the control of circuit mode services\fR
\fIat the \fR \fIN\fR
.sp 9p
.RT
.EF '% \fIx\ reference\ point''
.OF '''\fIx\ reference\ point %'
.PP
For the control of circuit mode services in the long term,
Signalling System\ No.\ 7 with ISUP will be used at the N\dx\ureference
point.
.RT
.sp 1P
.LP
4.2
\fIISDN\(hyISDN Interface where both ISDNs provide X.31 case B based\fR
\fIpacket mode bearer services\fR
.sp 9p
.RT
.PP
See Figure 3/I.520.
.PP
The X.75 protocol is used to transfer X.31 based packet mode
services at the N\dx\ureference point. Layers\ 1, 2, and 3 for this interface
are specified in X.75.
.bp
.RT
.LP
.rs
.sp 7P
.ad r
\fBFigure 3/I.520, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
4.3
\fIISDN\(hyISDN interface where a circuit mode bearer service is provided\fR
\fIby one ISDN to access either a PSPDN, or a PH and an X.31 case B packet\fR
\fImode bearer service provided by another ISDN\fR
.sp 9p
.RT
.PP
With this type of interworking, two different configurations are
considered, I and II. In configuration I, interworking between the two ISDNs
utilizes X.75 interexchange signalling. See Figure\ 4/I.520.
.PP
In configuration II, a circuit switched access to the PH in the
ISDN\d(\\dp\\ds\\d)\uis provided, and the interworking between the two ISDNs
utilizes a Signalling System\ No.\ 7 protocol.
.PP
This interworking arrangement applies for data transmission services. General
arrangements are covered in \(sc\ 6.3 of X.320. There are two
possibilities:
.RT
.LP
i)
X.31 case A interworking with X.31 case\ B. Case\ A refers to the situation
where a transparent circuit switched access to PSPDN is provided by ISDN.
Case\ B refers to the situation where a packet mode bearer service is provided
by an ISDN PH.
.LP
ii)
ISDN circuit switched access to an ISDN PH (this case may exist if the
originating ISDN does not have PH functionality).
.PP
Several aspects of interworking for data transmission services as well
as their application to other transmission services are for further
study.
.LP
.rs
.sp 9P
.ad r
\fBFigure 4a/I.520, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 13P
.ad r
\fBFigure 4b/I.520, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
4.4
\fIISDN\(hyISDN interworking via a transit network\fR
.sp 9p
.RT
.PP
ISDN\(hyISDN interworking via a transit network ( see Figure 5/I.520) may
be a useful configuration in the short term for extending specific ISDN
services on an end\(hyto\(hyend basis. Special transmission, switching
and signalling capabilities may have to be deployed in the transit network
to ensure that the specific ISDN service is available end\(hyto\(hyend.
.PP
The detailed interworking functions and interfaces for this
configuration are for further study.
.RT
.LP
.rs
.sp 7P
.ad r
\fBFigure 5/I.520, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
4.5
\fIISDN\(hyISDN interface for additional packet mode bearer services\fR
.sp 9p
.RT
.PP
For packet mode services that are currently under study, out\(hyband call
control signalling is used. The same out\(hyband call control is used for
circuit mode services. Two alternatives can be considered for this out\(hyband
call control: enhancement of Signalling System\ No.\ 7 and enhancement of the
D\(hychannel protocol. The choice between the two alternatives is for further
study.
.RT
.sp 1P
.LP
4.6
\fIISDN\(hyISDN interface where an X.31 case B based packet mode bearer\fR
\fIservice is provided on one ISDN and an additional packet mode bearer\fR
\fIservice is requested on another ISDN\fR
.sp 9p
.RT
.PP
Two alternatives can be considered: the first is based on in\(hyband signalling
(X.75), and the second is based on out\(hyband signalling (Signalling System\
No.\ 7 or D\(hychannel protocol). The choice between the two alternatives
is for further study.
.RT
.sp 1P
.LP
4.7
\fIISDN\(hyISDN interface for circuit mode to additional packet mode\fR
\fIservice\fR
.sp 9p
.RT
.PP
This section is for further study.
.RT
.sp 2P
.LP
\fB5\fR \fBInterworking functions\fR
.sp 1P
.RT
.PP
Interworking functions commonly employed for various types of
interworking are described in Recommendation\ I.510. The interworking functions
specific to ISDN\(hyISDN interworking are described here.
.RT
.sp 1P
.LP
5.1
\fIEcho control processing and speech processing\fR
.sp 9p
.RT
.PP
Table 4/I.520 shows the permitted relationship between circuit mode bearer
services and various forms of speech processing functionality. These
speech processing functions include digital speech interpolation (DSI),
low rate encoding (LRE) and digital circuit multiplication (DCM). Depending
upon the particular relationship to the circuit mode bearer services, these
processing functions are specified as essential, optional, prohibited or
functionally disabled.
.PP
For a speech, 3.1 kHz audio, or 64 kbitB/Fs unrestricted call within an
ISDN, appropriate network control is required to ensure that the relationship
shown within Table\ 4/I.520 is realized. An example of this control might
be
routing (to exclude or include a function) or out\(hyband signalling (to
disable a function). Further, it is to be noted that a disabling tone (see
Recommendations\ V.25 and I.530) may be used to functionally remove echo
control devices on a 3.1\ kHz audio bearer service connection.
.bp
.RT
.LP
.ce
\fBH.T. [T4.520]\fR
.ce
TABLE\ 4/I.520
.ce
\fBRelationship between speech processing and bearer services\fR
.ce
\fBwithin an ISDN and for ISDN\(hyISDN interworking \fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(36p) sw(36p) sw(36p) sw(36p) sw(36p) , ^ | c | c | c | c s
Digital circuit multiplication employing LRE and DSI and having
controllable flexibility in modes of operation.
.LP
\fINote\fR
\ \(em\ The bearer services in columns 1, 2 and 3 of the table permit control of speech processing devices only at call set\(hyup as required for the particular bearer service requested. The bearer service in column\ 4 requires additional
post set\(hyup user\(hyto\(hynetwork signalling (out\(hyband by D\(hychannel messages) in
order to perform the required in\(hycall service modifications between the
relevant alternative services.
.LP
\ua\d\u)\d
For the 3.1 kHz audio bearer service, echo control is included in the connection at the time of call set\(hyup. It is disabled for the transmission of voice\(hyband data by use of the disabling tone (see Recs.\ V.25 and I.\ 530).
.LP
\ub\d\u)\d
The exchange may set up a 64 kbit/s unrestricted bearer path with echo control devices and A\(hy\(*m law converters (if necessary) enabled for speech. In any case, the set up of parallel paths for speech and 64\ kbit/s unrestricted must be avoided.
.LP
\uc\d\u)\d
Echo control needs to be disabled when continuity check is
performed.
.LP
\ud\d\u)\d
Although echo control may not be required in ISDN\(hyISDN
interworking for digital telephones (for further study), its inclusion for
possible internetworking reasons for the speech bearer service is essential
(see also Rec.\ I.530).
.LP
\ue\d\u)\d
The necessity for network or terminal provided echo control in
4\(hywire end\(hyto\(hyend speech connections is for further study.
.LP
\uf\d\u)\d
The IWF converting A\(hy\(*m laws should also make the necessary bit
translation in the bearer capability information element to indicate the law
used.
.LP
\ug\d\u)\d
The network may include signal processing techniques provided they are appropriately modified or functionally removed prior to information
transfer.
.LP
\uh\d\u)\d
The 64 kbit/s transparent capability will be invoked, subject to the available transmission capacity, by the adjoining exchange over a dedicated out\(hyband signalling system.
.LP
\ui\d\u)\d
The provision of this bearer service using DCM is subject to the ability of the out\(hyband signalling system and the DCM equipment to execute
in\(hycall modifications initiated by the adjoining exchange.
.nr PS 9
.RT
.ad r
\fBTable 4/I.520 [T4.520], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
For a call which involves communication through different ISDNs, the network
information regarding control of these functions needs to be
extended across the ISDN\(hyISDN internetwork interfaces. This information
transfer is realized between the exchanges in interworking ISDNs by means
of:
.LP
1)
the Signalling System No. 7 ISUP bearer capability
information element, and
.LP
2)
the use of a disabling tone (see Recommendations\ V.25 and
I.530) by terminals, in the case of a 3.1\ kHz audio bearer service.
.PP
The control of speech processing functions (DCM, A\(hy\(*m\ law
conversion, echo control,\ etc.) by exchanges is:
.LP
a)
not needed when a disabling tone (see Recommendations\ V.25 and I.530)
is used, in conjunction with the 3.1\ kHz audio bearer service by a terminal(s),
and
.LP
b)
to be implemented using out\(hyband call processes (currently under study)
when needed.
.PP
The procedures in the case of alternate speech/64 kbitB/Fs
unrestricted bearer services, are for further study.
.sp 1P
.LP
5.2
\fIGeneration of in\(hyband tones and announcements for speech and\fR
\fI3.1 kHz audio bearer services\fR
.sp 9p
.RT
.PP
(\fINote\fR \ \(em\ This function is also necessary for a call within one
ISDN, which does not involve network interworking nor internal ISDN
interworking.)
.RT
.sp 1P
.LP
5.2.1
\fIUnsuccessful call delivery\fR
.sp 9p
.RT
.PP
The point of call failure (i.e. the point at which the connection cannot
proceed further) should generate the appropriate out\(hyband clearing
message toward the calling exchange. In response to this message, the calling
exchange should send the appropriate out\(hyband message to the calling
user.
However, for speech and 3.1\ kHz audio bearer services, the network must be
capable of generating the appropriate in\(hyband tones or announcements.
In this case, the clearing message should not be sent prior to the completion
of the
announcements.
.RT
.sp 1P
.LP
5.2.2
\fISuccessful call delivery\fR
.sp 9p
.RT
.PP
For speech and 3.1 kHz audio bearer services, the terminating
exchange should generate in\(hyband ring back tone towards the calling
user upon successful delivery of the call.
.RT
.sp 1P
.LP
5.3
\fICall negotiation between ISDNs\fR
.sp 9p
.RT
.PP
There are two aspects of call negotiation between ISDNs: service
agreement and connection agreement.
.RT
.sp 1P
.LP
5.3.1
\fIService agreement between ISDNs\fR
.sp 9p
.RT
.PP
Service agreement between ISDNs is defined as established
compatibility between the two networks on a requested service. The service
agreement does not necessarily occur on a call\(hyby\(hycall basis, but in a
pre\(hydetermined way which has been agreed by bilateral negotiation between
the two ISDNs. If the service agreement is established, connection agreement
then begins between the two ISDNs.
.PP
If the service agreement is not established, procedures are for
further study, including the following four alternatives. Additionally, the
impact of these alternatives on user\(hyto\(hynetwork protocols or internetwork
protocols is for further study.
.RT
.LP
1)
The call may be established without the service
compatibility (e.g.\ in the case of a supplementary service request).
.LP
2)
The call may be cleared.
.LP
3)
Either of the ISDNs may negotiate with the originating user to change
or abandon the user's service request.
.LP
4)
Another alternative may be selected from the originating
user's service profile.
.bp
.sp 1P
.LP
5.3.2
\fIConnection agreement between ISDNs\fR
.sp 9p
.RT
.PP
Connection agreement between ISDNs is defined as negotiation on the connection
element between the two networks. Connection agreement is required when
the connection elements employed in each ISDN are different, even if
service agreement exists. (For example, see Appendix\ I.) The use of call
progress indicators for this purpose is for further study.
.PP
In a speech bearer service, the objects for connection agreement might
be the use of one of the following: UDI (unrestricted digital information)/RDI
(restricted digital information), satellite circuits, DSI circuits, the
difference of PCM coding rules, circuit selection between digital networks
having different hierarchical structures,\ etc. Parameter exchange, if
required, are executed by the two networks.
.PP
The connection agreement does not necessarily occur on a call\(hyby\(hycall
basis, but in a pre\(hydetermined way which has been established by other
Recommendations (e.g.\ Recommendation\ G.802 for interworking between hierarchies
and Recommendation\ G.711 for A\(hy\(*m\ law conversion) or agreed between
two
ISDNs.
.RT
.sp 1P
.LP
5.4
\fICompatibility checking between end users of different\fR
\fIISDNs\fR
.sp 9p
.RT
.PP
When the connection path between two terminals on different ISDNs is established,
low level compatibility (LLC), high layer compatibility (HLC) or user defined
compatibility may be examined on an end\(hyto\(hyend basis.
.PP
Compatibility checking items between end users are as
follows:
.RT
.LP
1)
\fILow layer compatibility\fR
.LP
LLC information would normally be used for user\(hyto\(hyuser call
negotiation and would be passed transparently through the networks. The IWF
may, where required, examine and act on LLC information (see
Recommendation\ I.515, \(sc\ 2.2.1.3) in the cases where the LLC checking
lists (see Recommendation\ Q.931) employed by the relevant ISDNs are different.
.LP
2)
\fIHigh layer compatibility\fR
.LP
The HLC is to be conveyed transparently and the networks
need not operate on it. The examination and action on HLC information by the
IWF is for further study, in the case where the HLC checking lists employed
by the relevant ISDNs are different.
.LP
3)
\fIUser defined compatibility checking\fR
.LP
User defined compatibility
checking is the user responsibility. The network does not participate in
this compatibility checking.
.sp 2P
.LP
\fB6\fR \fBFunctional interworking requirements for data transmission\fR
\fBservices\fR
.sp 1P
.RT
.PP
See Recommendation X.320 on general arrangements for interworking between
ISDNs for the provision of data transmission services.
.PP
Network interworking requirements for the case where an X.31 based
packet mode bearer service is requested on one ISDN and a new packet mode
bearer service is requested on another ISDN will be provided when new packet
mode bearer services are defined.
.RT
.sp 2P
.LP
\fB7\fR \fBReferences\fR
.sp 1P
.RT
.PP
See Recommendation I.500.
\v'1P'
.RT
.ce 1000
APPENDIX\ I
.ce 0
.ce 1000
(to Recommendation I.520)
.sp 9p
.RT
.ce 0
.ce 1000
\fBISDN connections involving\fR
.sp 1P
.RT
.ce 0
.ce 1000
\fBrestricted 64 kbit/s transfer capability\fR
.ce 0
.LP
I.1
\fIGeneral\fR
.sp 1P
.RT
.PP
During an interim period the existence of networks or parts of
networks only capable of transferring 64\ kbit/s in a restricted manner
(i.e.\ 64\ kbit/s octet structured transfer capability with the all\(hyzero not
permitted) will have to be taken into account for international
intercommunication purposes.
.bp
.PP
For those networks, or parts thereof, the rules described hereafter
have to be followed in order to allow communication with networks, or parts
thereof, that already provide unrestricted 64\ kbit/s transfer capability.
The necessary interworking functions (e.g.\ interworking units, rate adaptors)
have to be provided by the network with restricted 64\ kbit/s transfer
capability.
Signalling provisions should be incorporated in Recommendation\ I.451 (Q.930).
The network with 64\ kbit/s transfer capability will not be affected by
this
interworking, other than transporting the appropriate signalling across this
network to and from the terminal connected to the 64\ kbit/s network.
.RT
.sp 1P
.LP
I.2
\fIInterworking with ISDNs providing restricted 64\ kbit/s\fR
(see Figure I\(hy1/I.520)
.sp 9p
.RT
.LP
.rs
.sp 20P
.ad r
\fBFigure I\(hy1/I.520, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
ISDN 1 may have some arrangements having only restricted 64\ kbit/s transfer
capability. ISDN\ 2 is unrestricted. In both cases, at the reference
points\ S/T, the I.412 user\(hynetwork interfaces are provided. However, where
restricted 64\ kbit/s arrangements are involved, only information streams not
having the all\(hyzero octet are possible.
.PP
Four possible cases of interworking for circuit switched connections between
terminals\ A and\ B are considered (UDI means unrestricted digital
information and RDI means restricted digital information). (See
Table\ I\(hy1/I.520.)
.RT
.sp 1P
.LP
I.3
\fIConsiderations for terminal designed to operate with restricted\fR
\fI64 kbit/s transfer capability\fR (Figure I\(hy2/I.520)
.sp 9p
.RT
.PP
Existing terminals at rates less than 64 kbit/s will require rate adaption
to operate with restricted 64\ kbit/s transfer capability (see