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.\" Troff code generated by TPS Convert from ITU Original Files
.\" Not Copyright ( c) 1991
.\"
.\" Assumes tbl, eqn, MS macros, and lots of luck.
.TA 1c 2c 3c 4c 5c 6c 7c 8c
.ds CH
.ds CF
.EQ
delim @@
.EN
.nr LL 40.5P
.nr ll 40.5P
.nr HM 3P
.nr FM 6P
.nr PO 4P
.nr PD 9p
.po 4P
.rs
\v | 5i'
.sp 2P
.LP
\fBRecommendation\ I.122\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBFRAMEWORK\ FOR\ PROVIDING\ ADDITIONAL\ PACKET\ MODE\ BEARER\ SERVICES\fR
.EF '% Fascicle\ III.7\ \(em\ Rec.\ I.122''
.OF '''Fascicle\ III.7\ \(em\ Rec.\ I.122 %'
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBIntroduction\fR
.sp 1P
.RT
.PP
Packet mode bearer services supported by an ISDN are given in
Recommendation\ I.232. Recommendation\ I.462 (X.31) specifies the procedures
for two such bearer services, virtual call and permanent virtual circuit
bearer
services, for the support of X.25 packet mode terminals in ISDN.
.PP
This Recommendation establishes an architectural framework within
which additional packet mode bearer services are described.
.RT
.sp 1P
.LP
1.1
\fIScope\fR
.sp 9p
.RT
.PP
The architectural framework and service descriptions given in this Recommendation
provide the basis for further work to be done by CCITT during
the 1989\(hy1992 Study Period. This method of work involves first the description
of services and then the development of protocols to support them.
.PP
During the course of this work the first ISDN principle given in
Recommendation\ I.120 should be followed. That is, a wide range of applications
should be supported by the same network using a limited set of connection
types and multipurpose user\(hynetwork interface arrangements. From considerations
in
this Recommendation it is also desirable to limit the number of bearer
services. It is recognized, however, that at this time it is premature to
exclude any potential bearer services. The criteria on the basis of which
the number of these bearer services could be reduced requires further study.
.PP
The Recommendation also provides a
general description on
interworking
requirements between I.122 based services and I.462 (X.31)
based services or PSPDNs.
.RT
.sp 1P
.LP
1.2
\fIObjectives\fR
.sp 9p
.RT
.PP
The principle of separation of the user and control planes for all telecommunication
services has been established as a fundamental concept of the ISDN protocol
reference model (Rec.\ I.320). This principle has been
applied, however, only to circuit mode services. Packet mode services in
ISDN are based on Recommendation\ I.462 (X.31). Recommendation\ I.462 (X.31)
is a
pragmatic approach that minimizes deployment and interworking difficulties,
while at the same time providing access to packet services through an
integrated physical interface.
.PP
The evolution of packet mode services in ISDN has been investigated, and
an architectural framework for providing additional packet mode services
has been established in this Recommendation. In undertaking this investigation
the main objective was to establish a framework based on the ISDN protocol
reference models described in Recommendation\ I.320. More specifically, this
framework was aimed at achieving:
.RT
.LP
a)
full integration of C\(hyplane (control plane) procedures for all services,
i.e.\ one set of protocols for call control; supplementary
services and operational, administrative and maintenance messages (OAM)
across all telecommunication services;
.LP
b)
the decoupling of user information transfer requirements
from C\(hyplane transfer requirements. This allows the possibility of defining
telecommunication services whose U\(hyplane (user plane) characteristics are
tailor\(hymade only to the transfer needs of user information and not to
those of C\(hyplane information.
.PP
The bearer services supported within this architectural framework are in
the virtual call and permanent virtual circuit bearer service category.
All bearer services defined within this framework if and when included
in
Rec.\ I.232 will have recommended overall provision\ A (Additional).
.bp
.sp 1P
.LP
1.3
\fIDefinitions of terms\fR
.sp 9p
.RT
.PP
In the context of this Recommendation, the following definitions
apply:
.PP
\fINote\fR \ \(em\ This list is not complete. For example, some of these
definitions apply to terms relevant to only some of the bearer services
discussed in this Recommendation.
.RT
.sp 1P
.LP
1.3.1
\fBdelivered duplicate frames\fR
.sp 9p
.RT
.PP
A frame D received by a particular destination user is defined to be a
duplicated frame if both of the following conditions are true:
.RT
.LP
a)
D was not generated by the source user;
.LP
b)
D is exactly the same as a frame that was previously
delivered to that destination.
.sp 1P
.LP
1.3.2
\fBdelivered errored frames\fR
.sp 9p
.RT
.PP
A delivered frame is defined to be an errored frame when the
value of one or more bits in the frame is in error, or when some, but not
all, bits in the frame are lost bits or extra bits (i.e.\ bits that were
not present in the original signal). (See Rec.\ X.140).
.RT
.sp 1P
.LP
1.3.3
\fBdelivered out\(hyof\(hysequence frames\fR
.sp 9p
.RT
.PP
\fI\fR Consider a sequence of frames \fIF\fR\d1\u, \fIF\fR\d2\u, \fIf\fR\d3\u, | | | ,
\fIF\fR\d\fIn\fR\u. Assume that \fIF\fR\d1\uis transmitted first, \fIF\fR\d\fI2\fR\usecond,
| | |
\fIF\fR\d\fIn\fR\ulast.
.PP
A delivered frame \fIF\fR\d\fIi\fR\uis defined to be out\(hyof\(hysequence
if it
arrives at the destination user after any of the frames\ \fIF\fR \d(\fIi\fR
\ +\ 1)
\u, \fIF\fR \d(\fIi\fR \ +\ 2)
\u, | | | , \fIF\fR\d\fIn\fR\u.
.RT
.sp 1P
.LP
1.3.4
\fBdynamic window control\fR
.sp 9p
.RT
.PP
The term dynamic window control refers to a set of procedures
based on which the transmitter's transmit window is modified, according to a
user\(hyperceived congestion condition in the network.
.RT
.sp 1P
.LP
1.3.5
\fBend\(hyto\(hyend communication\fR
.sp 9p
.RT
.PP
End\(hyto\(hyend communication is a direct peer\(hyto\(hypeer communication
of TE to TE, or TE to a network interworking function (IWF) supporting,
for
example, PSPDN interworking.
.RT
.sp 1P
.LP
1.3.6
\fBexplicit congestion message\fR
.sp 9p
.RT
.PP
Explicit congestion message is a message generated by the network and sent
to a user terminal to indicate a congestion condition.
.RT
.sp 1P
.LP
1.3.7
\fBimplicit congestion control\fR
.sp 9p
.RT
.PP
Implicit congestion control is a scheme under which user terminals first
detct a possible congestion condition by means other than explicit
congestion messages, and then take appropriate action to reduce their
throughput.
.RT
.sp 1P
.LP
1.3.8
\fBinformation integrity\fR
.sp 9p
.RT
.PP
Information integrity is a network providing frame\(hyrelaying bearer service
defines that all frames carried by the network shall satisfy the FCS
check.
.RT
.sp 1P
.LP
1.3.9
\fBlogically separate (C\(hyplane information)\fR
.sp 9p
.RT
.PP
Logically separate means that C\(hyplane information is sent
separately from U\(hyplane information in one of the following ways:
.RT
.LP
1)
on a physically separate interface;
.LP
2)
on another channel (time slot) within the same interface;
or
.LP
3)
on a separate logical link within the same channel
(e.g.,\ D\(hychannel).
.bp
.sp 1P
.LP
1.3.10
\fBlost frames\fR
.sp 9p
.RT
.PP
A transmitted frame is declared to be a lost frame when the frame is not
delivered to the intended destination user within a specified timeout
period, and the network is responsible. (See Rec.\ X.140).
.RT
.sp 1P
.LP
1.3.11
\fBmisdelivered frames\fR
.sp 9p
.RT
.PP
A misdelivered frame is a frame transferred from a source user to a destination
user other than the intended destination user. It is considered inconsequential
whether the information is correct or incorrect in content.
(See Rec.\ X.140).
.RT
.sp 1P
.LP
1.3.12
\fBquality of service (QOS)\(hyparameter set\fR (See
Rec.\ X.213)
.sp 9p
.RT
.PP
For each QOS\(hyparameter, a set of \*Qsubparameters\*U is defined from
among the following possibilities:
.RT
.LP
a)
a \fItarget\fR | value which is the QOS value desired by the
calling user;
.LP
b)
the \fIlower quality acceptable\fR | value which is the lowest
QOS value agreeable to the calling user. (When the lowest quality acceptable
refers to throughput, the term \*Qminimum\*U may be used, while when it
refers to transit delay, the term \*Qmaximum\*U may be used.);
.LP
c)
an \fIavailable\fR | value which is the QOS that the network is willing
to provide;
.LP
d)
a \fIselected\fR | value which is the QOS value to which the
called user agrees.
.sp 1P
.LP
1.3.13
\fBreal time call establishment\fR
.sp 9p
.RT
.PP
The term real time call establishment refers to a set of
procedures based on which the communication can be started in a relatively
short time (i.e.\ in the order of a few seconds) after the request is made.
(See definition for demand communication establishment in
Rec.\ I.130).
.RT
.sp 1P
.LP
1.3.14
\fBresidual error rate\fR
.sp 9p
.RT
.PP
Residual error rate is defined for both the additional packet\(hymode bearer
services and the corresponding layer services.
.PP
The layer services corresponding to the additional packet\(hymode bearer
services are characterized by the exchange of service data units (SDUs).
For frame relaying\ 1, SDUs are exchanged at the functional boundary between
the
core functions of Recommendation
.FS
I.441* is I.441 with appropriate
extensions. The use of the extensions may depend on each bearer service
and is for further study.
.FE
and the end\(hyto\(hyend protocol implemented above them. For frame relaying\
2 and frame switching, SDUs are exchanged at the functional
boundary between the complete I.441* and the end\(hyto\(hyend functions
implemented above I.441*. For the X.25\(hybased additional packet mode
service (APMS), SDUs are exchanged at the functional boundary of X.25 PLP\(hyDTP
(packet layer
protocol\(hydata transfer part) and the end\(hyto\(hyend functions implemented
above.
.PP
The network participates in this exchange by means of protocol data units
(PDUs). In frame relaying\ 1 and 2, PDUs are frames as defined in the
core functions of I.441*. In frame switching, PDUs are frames as defined in
I.441*, while in X.25\(hybased APMS, they are packets as defined in X.25 PLP.
.PP
The residual error rate for the corresponding layer service of APMS is
defined as:
\v'6p'
.RT
.sp 1P
.ce 1000
\fIR\fR = 1 \(em
@ { otal~correct~SDUs~delivered } over { otal~offered~SDUs } @
.ce 0
.sp 1P
.PP
.sp 1
The residual error rate for the APMS is defined as the
ratio:
\v'6p'
.sp 1P
.ce 1000
\fIR\fR = 1 \(em
@ { otal~correct~PDUs~delivered } over { otal~offered~PDUs } @
.ce 0
.sp 1P
.LP
.sp 1
.bp
.sp 1P
.LP
1.3.15
\fBthroughput\fR
.sp 9p
.RT
.PP
Throughput for a virtual connection section
.FS
Virtual connection section is defined in Rec.\ X.134.
.FE
in a network providing the frame
relaying bearer service, is the number of data bits contained between the
address field and the FCS field of the frames successfully transferred
in one direction across that section per unit time. Successful transfer
means that the FCS check for each frame is satisfied.
.RT
.sp 1P
.LP
1.3.16
\fBtransit delay\fR
.sp 9p
.RT
.PP
Transit delay is defined only between pairs of section
boundaries
.FS
The definition of section boundaries is given in
Rec.\ X.134.
.FE
. Transit delay of a frame protocol data unit (FPDU)
.FS
The
definition of FPDU is given above in residual error rate.
.FE
starts at the
time\ \fIt\fR\d1\uat which the first bit of the FPDU crosses the first
boundary, and ends at the time\ \fIt\fR\d2\uat which the last bit of the
FPDU crosses the second boundary.
.PP
Transit delay = \fIt\fR\d2\u\(em\fIt\fR\d1\u.
.RT
.sp 2P
.LP
\fB2\fR \fBService aspects\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
\fIGeneral service characteristics\fR
.sp 9p
.RT
.PP
This Recommendation describes a set of potential
packet mode
bearer services
that have the following characteristics in
common:
.RT
.LP
1)
All C\(hyplane procedures, if needed, are performed in a
logically separate manner using protocol procedures that are integrated
across all telecommunications services (i.e.\ I.451 with appropriate extensions).
.LP
2)
The U\(hyplane procedures share the same layer 1 functions
based on Rec.\ I.430/I.431. Moreover, they share the same core
procedres, defined in \(sc\ 3.1, that among other functions allow for statistical
multiplexing of user information flows immediately above the layer\ 1
functions.
.PP
The basic bearer service provided by the network is the order
preserving bidirectional transfer (see \(sc\ 2.3.1) of service data units
(i.e.\ frames or packets) from one S/T reference point to another. The data
units are routed through the network on the basis of an attached label
(e.g.\ the data link connection identifier (DLCI) value of the frame). This
.PP
label is a logical identifier with local significance. In the virtual call
case, the value of the logical identifier and the other associated parameters
are negotiated during the call set\(hyup by means of C\(hyplane procedures.
Depending on the bearer service and parameters, the network may accept
or reject the user requested service. In the permanent virtual circuit
case, the logical
identifier and the other associated parameters are defined by means of
administrative procedures. The network treatment of the data units,
(e.g.\ unacknowledged transfer, acknowledged transfer, error recovery) in
addition to simple transfer, depends on the specific bearer service requested.
.PP
The user network interface structure at the S/T reference point allows
for the establishment of multiple virtual calls and/or permanent virtual
circuits to many destinations.
.RT
.sp 1P
.LP
2.2
\fIQuality of Service parameters\fR
.sp 9p
.RT
.PP
Each potential bearer service described in this Recommendation
provides service quality that is characterized by the values of the following
parameters:
.RT
.LP
1)
throughput;
.LP
2)
transit delay;
.LP
3)
information integrity;
.LP
4)
residual error rate;
.LP
5)
delivered errored frames;
.LP
6)
delivered duplicated frames;
.LP
7)
delivered out\(hyof\(hysequence frames;
.bp
.LP
8)
lost frames;
.LP
9)
misdelivered frames;
.LP
10)
others for further study.
.PP
\fINote\fR \ \(em\ The applicability and values of these parameters for
different bearer services are for further study.
.sp 1P
.LP
2.3
\fIIndividual\fR \fIbearer service descriptions\fR
.sp 9p
.RT
.PP
This section contains descriptions of four specific potential
bearer services proposed for standardization:
.RT
.LP
a)
frame relaying 1,
.LP
b)
frame relaying 2,
.LP
c)
frame switching, and
.LP
d)
X.25\(hybased additional packet mode.
.sp 1P
.LP
2.3.1
\fIFrame relaying 1 service description\fR
.sp 9p
.RT
.PP
Frame relaying 1
shares with the other services the general service characteristics and
quality of service parameters described in \(sc\(sc\ 2.1 and 2.2, respectively.
.PP
The
frame relaying 1 data units
are frames as defined in
Rec.\ I.441. The basic bearer service provided is the unacknowledged
transfer of frames from S/T to S/T reference point. More specifically,
in the U\(hyplane:
.RT
.LP
1)
it preserves their order as given at one S/T reference point if and when
they are delivered at the other end.
.LP
\fINote\fR \ \(em\ Since the network does not terminate the upper part of
I.441, sequence numbers are not kept by the network. Networks should be
implemented in a way that, in principle, frame order is preserved;
.LP
2)
it detects transmission, format and operational errors (e.g. frames of
unknown DLCI);
.LP
3)
frames are transported transparently (in the network), only the address
and FCS field may be modified;
.LP
4)
it does not acknowledge frames (within the network).
.PP
All of the above functions are based on Rec.\ I.441.
Appropriate extensions to the core functions of Rec.\ I.441 may be
needed, e.g.\ for congestion control. In the C\(hyplane all signalling
capabilities for call control, parameter negotiation,\ etc. are based on a
common set of protocols (e.g.\ Rec.\ I.451 extended), as for all ISDN
telecommunication services. In the case of permanent virtual circuits (PVC)
no real time call establishment is necessary and parameters are agreed
upon at subscription time.
.PP
However, additional functions are needed:
.RT
.LP
\(em
to monitor throughput and to enforce it,
.LP
\(em
to control congestion.
.PP
The mechanisms to achieve these functions are still under
investigation.
.PP
Appropriate protocol capabilities should be available so that the
network may discard erroneous frames if it elects to do so. Note that if
networks elect to forward erroneous frames to the user, fraud and misdelivery
of frames may occur.
.PP
From the service perspective, frame relaying 1 provides service
quality characteristics with the following parameter values:
.PP
(Parameter values are for further study).
.RT
.sp 1P
.LP
2.3.2
\fIFrame relaying 2 service description\fR
.sp 9p
.RT
.PP
Frame relaying 2
shares with the other services the general service characteristics and
Quality of Service parameters described in \(sc\(sc\ 2.1 and 2.2, respectively.
.bp
.PP
The frame relaying data units are frames as defined in
Rec.\ I.441. The basic bearer service provided is an unacknowledged
transfer of frames from S/T to S/T reference point. More specifically,
in the U\(hyplane:
.RT
.LP
1)
it preserves their order as given at one S/T reference point if and when
they are delivered at the other end.
.LP
\fINote\fR \ \(em\ Since the network does not terminate th upper part of
I.441, sequence numbers are not kept by the network. Networks should be
implemented in a way that, in principle, frame order is preserved;
.LP
2)
it detects transmission, format and operational errors (e.g. frames of
unknown DLCI);
.LP
3)
frames are transported transparently in the network, only
the address and FCS field may be modified;
.LP
4)
it does not acknowledge frames (within the network);
.LP
5)
normally the only frames received by a user are those sent by the distant
user. (Currently, implicit congestion control is preferred in
which the network does not generate any congestion control messages toward
the user. The generation of explicit congestion control messages by the
network is for further study.)
.PP
All of the above functions are based on Rec.\ I.441.
Appropriate extensions to Rec.\ I.441 may be needed, e.g.\ in relation
to congestion control.
.PP
In the C\(hyplane all signalling capabilities for call control, parameter
negotiation,\ etc. are based on a common set of protocols
(e.g.\ Rec.\ I.451 extended), as for all ISDN telecommunication
services. In the case of permanent virtual circuits (PVC) no real time call
establishment is necessary and any parameters are agreed upon at subscription
time.
.PP
However, additional network functions are needed:
.RT
.LP
\(em
to monitor throughput and to enforce it,
.LP
\(em
to control congestion.
.PP
The mechanisms to achieve these functions are still under
investigation.
.PP
Appropriate protocol capabilities should be available so that the
network may discard erroneous frames if it elects to do so. Note that if
networks elect to forward erroneous frames to the user, fraud and misdelivery
of frames may occur.
.PP
The difference between the two types of frame relaying is that in
frame relaying\ 2 the end points always implement, above the core functions,
the upper part of Rec.\ I.441 extended. Consequently, in frame relaying\
2
the network may take advantage of the knowledge of the layer\ 2 parameters in
order to facilitate network operations such as charging and resource
allocation. In frame relaying\ 1 the functions implemented end\(hyto\(hyend
above the core functions are user selectable and may not be the upper part
of
Rec.\ I.441. Consequently, in frame relaying\ 1 the network in
principle has no knowledge of the protocol used end\(hyto\(hyend.
.PP
From the service perspective, frame relaying 2 provides service
quality characteristics with the following parameter values:
.PP
(Parameter values are for further study).
.PP
The terminal operates with an extended I.441 protocol. As a result
the user perspective is the transparent transport of data end\(hyto\(hyend,
with a
quality influenced by the statistical multiplexing of data streams in the
network. Acknowledgement of data is end\(hyto\(hyend as well as error detection
and recovery.
.RT
.sp 1P
.LP
2.3.3
\fIFrame switching service description\fR
.sp 9p
.RT
.PP
Frame switching
has general service characteristics and
Quality of Service parameters as given in \(sc\(sc\ 2.1 and 2.2, respectively.
.PP
In addition, in the U\(hyplane, frame switching:
.RT
.LP
1)
provides for the acknowledged transport of frames;
.LP
2)
detects and recovers from transmission, format, and
operational error;
.LP
3)
detects and recovers from lost or duplicated frames;
.LP
4)
provides flow control.
.PP
All of the above functions are based on Recommendation\ I.441.
Appropriate extensions to Recommendation\ I.441 may be needed.
.bp
.PP
In the C\(hyplane all signalling capabilities for all call control,
parameter negotiation,\ etc. are based on a common set of protocols
(e.g.\ Rec.\ I.451 extended), as for all ISDN telecommunication
services. In the case of permanent virtual circuits no real time call
establishment is necessary and any parameters are agreed upon at subscription
time.
.PP
From the service perspective, frame switching provides service quality
characteristics with the following parameter values:
.PP
(Parameter values are for further study).
.RT
.sp 1P
.LP
2.3.4
\fIX.25\(hybased\fR \fIadditional packet mode service description\fR
.sp 9p
.RT
.PP
X.25\(hybased additional packet mode has general service
characteristics and Quality of Service parameters similar to the packet mode
services described in X.31.
.PP
The U\(hyplane capabilities are the same as in X.25 PLP Data Transfer
Part (DTP)
.PP
In the C\(hyplane all signalling capabilities for call control, parameter
negotiation,\ etc. are based on a common set of protocols
(e.g.\ Rec.\ I.451 extended), as for all ISDN telecommunication
services. In the case of permanent virtual circuits (PVC) no real time call
establishment is necessary and any parameters are agreed upon at subscription
time.
.RT
.sp 2P
.LP
\fB3\fR \fBUser\(hynetwork interface protocol reference model\fR
.sp 1P
.RT
.PP
Figure 1/I.122 is a direct application of the ISDN protocol
reference model to the packet mode communications discussed in this
Recommendation. It shows the user\(hynetwork interface protocol architecture.
Only those functions on the network side that are visible on the user side
of the
S/T reference point are shown.
.PP
On the user side, Recommendations I.430 or I.431 provide the layer 1 protocol
for the U\(hy (user) C\(hy (control) planes. The C\(hyplane uses the D\(hychannel
with Recommendations\ I.441 extended and I.451 extended as the layer\ 2
and 3
protocols, respectively. In the case of permanent virtual circuits (PVC) no
real time call establishment is necessary and any parameters are agreed
upon at subscription time. The U\(hyplane may use any channel (D, B, H\d0\uand
H\d1\u) on which the user implements at least the lower part (the core
functions) of
Recommendation\ I.441.
.RT
.LP
.rs
.sp 23P
.ad r
\fBFigure 1/I.122, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T1.122]\fR
.ce
TABLE\ 1/I.122
.ce
\fBU\(hyplane functions applicable to each bearer service\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(96p) | cw(66p) | cw(66p) .
Bearer service User terminal (Note 1) Network
_
.T&
lw(96p) | lw(66p) | lw(66p) .
Frame relaying 1 I.441* Core (Note 2) I.441* Core
_
.T&
lw(96p) | lw(66p) | lw(66p) .
Frame relaying 2 I.441* I.441* Core
_
.T&
lw(96p) | lw(66p) | lw(66p) .
Frame switching I.441* I.441*
_
.T&
lw(96p) | lw(66p) | lw(66p) .
{
X.25\(hybased additional packet mode
} I.441* X.25 DTP I.441* X.25 DTP
.TE
.LP
\fINote\ 1\fR
\ \(em\ Additional user selectable functions may be
implemented.
.LP
\fINote\ 2\fR
\ \(em\ I.441* is I.441 with appropriate extensions. The use of the
extensions may depend on each bearer service and is for
further study.
.nr PS 9
.RT
.ad r
\fBTable 1/I.122 [T1.122], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.1
\fICore functions of Rec. I.441\fR
.sp 9p
.RT
.PP
The core functions are:
.RT
.LP
\(em
frame delimiting, alignment, and transparency,
.LP
\(em
frame multiplexing/demultiplexing using the address field,
.LP
\(em
inspection of the frame to ensure that it consists of an
integer number of octets prior to zero bit insertion or following zero bit
extraction,
.LP
\(em
inspection of the frame to ensure that it is neither too long nor too
short (see Note),
.LP
\(em
detection of transmission errors.
.PP
\fINote\fR \ \(em\ The maximum and minimum frame lengths that apply to
the Additional packet mode bearer services are for further study.
.sp 1P
.LP
3.2
\fIOther\fR \fIuser terminal functions\fR
.sp 9p
.RT
.PP
If not already prescribed by the selected packet mode bearer
service, the user may also implement functions such as, for example, recovery
from detected transmission, format, and operational errors above the core
functions using the full procedures of Recommendation\ I.441. Additional
functions such as flow control may also be implemented. For example, X.25
data transfer functions may also be implemented above the preceding stack.
.RT
.sp 1P
.LP
3.3
\fINetwork functions\fR
.sp 9p
.RT
.PP
On the network side, Recommendations I.430 or I.431 provide the
layer 1 protocol for both C\(hy and U\(hyplanes. The C\(hyplane is handled
just as on
the user side, i.e.\ the network fully terminates the protocols of
Recommendations\ I.441 and I.451. In the U\(hyplane, at least the core
functions of Recommendation\ I.441 protocol are terminated. The network
may terminate
additional protocol functions only as requested by the user and negotiated
and agreed to by the user and the network. The U\(hyplane protocols to
be terminated by the network are determined by the specific bearer service
requested by the user, and negotiated and agreed to by the user and network.
.PP
Interactions between the U\(hy and C\(hyplanes of the terminal, and between
the U\(hy and C\(hyplanes of the network are independent. As a result,
coordination between the U\(hy and C\(hyplanes at the users equipment is
not the responsibility of the network.
.bp
.PP
During the three phases of a call (call establishment, data transfer, and
call clearing), C\(hy and U\(hyplane synchronization is achieved in a similar
way as for all ISDN telecommunications services. That is, after the C\(hyplane
has
established the connection, the U\(hyplane may commence data transfer with or
.PP
without an initialization procedure in the U\(hyplane. In the case of permanent
virtual circuit the establishment and call clearing is accomplished by
administrative procedures.
.RT
.sp 1P
.LP
3.4
\fIFurther service requirements at the user\(hynetwork interface\fR
.sp 9p
.RT
.PP
Procedures at the user\(hynetwork interface should be also applicable when
two users are connected via a circuit mode bearer service (permanent or
demand). Mechanisms that can be used to achieve this objective include, for
example, the symmetrization of the procedure involved, or the use of additional
procedures for the determination of the asymmetric relationships. The selection
of such a mechanism is for further study.
.RT
.sp 1P
.LP
3.5
\fIPotential bearer services\fR
.sp 9p
.RT
.PP
Four potential bearer services are identified as part of this
architectural framework. The first potential bearer service, frame relaying\
1, is provided when no functions above the core functions are terminated
by the
network: if needed, such functions are terminated only end\(hyto\(hyend.
.PP
The second potential bearer service, frame relaying 2, is provided
when no functions above the core functions are terminated by the network;
I.441 upper functions are terminated only at the end points.
.PP
The third potential bearer service, frame switching, is provided when the
full Recommendation\ I.441 protocol is terminated by the network.
.PP
The fourth potential bearer service, X.25\(hybased additional packet
mode, is provided when the full Recommendation\ I.441 protocol and the data
transfer part (DTP) of Recommendation\ X.25 PLP (packet layer protocol) are
terminated by the network.
.PP
Further information on the service characteristics of these four
potential bearer services is given in Annex\ A.
.RT
.sp 2P
.LP
\fB4\fR \fBInterworking requirements\fR
.sp 1P
.RT
.sp 1P
.LP
4.1
\fIInterworking between packet mode services\fR
.sp 9p
.RT
.PP
To interconnect different packet mode bearer services, it is
necessary to provide interworking between an ISDN offering any of the bearer
services described in this Recommendation, and:
.RT
.LP
1)
an ISDN offering any of these additional packet mode bearer services,
.LP
2)
an X.25\(hybased service offered either by an ISDN or a
PSPDN.
.PP
For interworking configuration 1), procedures for both the C\(hyplane and
the U\(hyplane at an internetwork reference point which includes international
gateway reference points, have to be standardized. In addition it would be
desirable that these procedures be developed in such a way that they also
could be used at an inter\(hyexchange reference point within an ISDN offering
any of the bearer services described in this Recommendation. Examples of
such procedures may include: routing, address translation, security and
accounting tasks.
.PP
For interworking configuration 2), interworking based on either call control
mapping or port access is possible. A high level description of
interworking arrangements is contained in Annex\ B.
.RT
.sp 1P
.LP
4.2
\fISupport of existing terminals\fR
.sp 9p
.RT
.PP
Additionally, terminal adapter functions should be provided that
allow existing terminals (e.g.\ asynchronous, start/stop DTEs, X.25 packet
mode DTEs and V\(hySeries interface terminals) to access from an ISDN one
or more of
the bearer services described in this Recommendation.
.RT
.sp 1P
.LP
4.3
\fIInterworking with circuit mode services\fR
.sp 9p
.RT
.PP
Other service interworking configurations (e.g. with a CSPDN, or
between different bearer services within an ISDN) may also need to be
considered.
.bp
.RT
.sp 2P
.LP
\fB5\fR \fBSupport of OSI connection\(hyoriented network layer service\fR
.sp 1P
.RT
.PP
In the interworking between an ISDN offering any of the bearer
services described in this Recommendation and X.25\(hybased service offered
either by an ISDN or a PSPDN, an interworking function (IWF) is required.
.PP
To support network layer service (Rec.\ X.213) when the
bearer service used is one of the bearer services described in this
Recommendation, the use of additional end system functionality may be required
and end\(hyto\(hyend (i.e.\ TE\(hyto\(hyTE or TE\(hyto\(hyIWF) compatibility
must be ensured.
.PP
Annex C contains requirements for the support of network layer service
(Rec.\ X.213).
.RT
.sp 2P
.LP
\fB6\fR \fBApplications\fR
.sp 1P
.RT
.PP
Packet mode bearer services described in this Recommendation aim at data
services up to 2\ Mbit/s. Within this broad category, some specific
applications are as follows:
.RT
.LP
1)
\fIBlock interactive data applications\fR
.LP
An example of a block interactive application would be high
resolution graphics (e.g.\ high resolution videotex, CAD/CAM). The main
characteristics of this type of application are low delays [e.g.\ approximately
less than . | | \ ms (the exact value is for further study)] and throughput
approximately in the range of 500\ kbit/s to 2048\ kbit/s.
.LP
2)
\fIFile transfer\fR
.LP
The file transfer application is intended to cater for large file transfer
requirements. Transit delay is not as critical for this application as
it is for example in the first application. Higher throughput (e.g.\ 16\
kbit/s to 2048\ kbit/s) might be necessary in order to produce reasonable
transfer
times for large files.
.LP
3)
\fIMultiplexed low bit rate\fR
.LP
The multiplexed low bit rate application exploits the multiplexing capabilities
of the layer\ 2 protocol in order to provide an economical access arrangement
for a large group of low bit rate applications. The low bit rate
sources should be multiplexed onto any ISDN\(hychannel by an NT function which
could take the form of a LAN, PABX, or Centrex. The delay requirements
are in the area of | | | \ ms (the exact value is for further study)
and the throughput within the range of 16\ kbit/s to 2048\ kbit/s.
.LP
4)
\fICharacter\(hyinteractive traffic\fR
.LP
An example of a character\(hyinteractive traffic is text editing. The
main characteristics of this type of applications are short frames, low
delays and low throughput.
.PP
Identification of additional applications and their
characteristics (e.g.\ delay, throughput,\ etc.) for bearer services described
in this Recommendation are desirable for the complete definition of the
service
requirements.
\v'1P'
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation I.122)
.sp 9p
.RT
.ce 0
.ce 1000
\fBFurther service\(hyrelated information\fR
.sp 1P
.RT
.ce 0
.LP
A.1
\fIIntroduction\fR
.sp 1P
.RT
.PP
This Annex contains further service related information on the
I.122 based bearer services. The intent of this Annex is to clarify and
supplement the service descriptions given in the main body of this
Recommendation. Note that the information given in this Annex should not be
interpreted as material that completes the service descriptions of the
bearer services given in this Recommendation.
.bp
.RT
.sp 2P
.LP
A.2
\fIService related information\fR
.sp 1P
.RT
.sp 1P
.LP
A.2.1
\fIFrame relaying 1\fR
.sp 9p
.RT
.PP
The U\(hyplane configuration for this service is shown in
Figure\ A\(hy1/I.122.
.RT
.LP
.rs
.sp 24P
.ad r
\fBFigure A\(hy1/I.122, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
Figure A\(hy1/I.122 shows the network in a generic way and
illustrates all U\(hyplane functions up to and including layer\ 3. In a
specific
network, frame relaying\ 1 may be implemented in one or more nodes, all other
nodes in the network providing only circuit\(hymode functions.
.PP
Frame relaying 1 can be offered on both, basic and primary rate
interfaces and on any ISDN channel (D, B, and H). Some restrictions (e.g.\
frame length) apply when in an end\(hyto\(hyend connection at least one
of the access
channels is the D\(hychannel (16\ kbit/s).
.PP
The bearer service provided by the network at the S/T reference point supports
only the core functions defined in \(sc\ 3.1. A frame received by such
a point is discarded if the frame does not meet the I.441 core format
requirements (for example, if the frame is too long, has an unknown
label,\ etc.). Moreover, frames may be discarded due to internal network
conditions, or other reasons such as throughput enforcement.
.PP
In all other cases, the frame is relayed to one of the adjacent nodes according
to the routing plan established at call set\(hyup time, or at
subscription time (if the network is providing a permanent virtual circuit
service).
.PP
No additional U\(hyplane functions (see Note) visible to the users are
performed by the network. If needed by the application, additional functions
are performed end\(hyto\(hyend by layer(s) above the core functions.
.PP
\fINote\fR \ \(em\ Some additional auxiliary U\(hyplane functions such
as reset or explicit congestion control may be defined if needed from the
service
perspective.
.bp
.RT
.sp 1P
.LP
A.2.2
\fIFrame relaying 2\fR
.sp 9p
.RT
.PP
The U\(hyplane configuration for this service is shown in
Figure\ A\(hy2/I.122.
.RT
.LP
.rs
.sp 20P
.ad r
\fBFigure A\(hy2/I.122, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
Figure A\(hy2/I.122 shows the network in a generic way and
illustrates all U\(hyplane functions up to and including layer\ 3. In a
specific
network, frame relaying\ 2 may be implemented in one or more nodes, all other
nodes in the network providing only circuit\(hymode functions.
.PP
Frame relaying 2 can be offered on both, basic and primary rate
interfaces and on any ISDN channel (D, B, and H). Some restrictions (e.g.\
frame length) apply when in an end\(hyto\(hyend connection at least one
of the access
channels is the D\(hychannel (16\ kbit/s).
.PP
The bearer service provided by the network at the S/T reference point supports
only the core functions defined in \(sc\ 3.1. A frame received by such
a point is discarded if the frame does not meet the I.441 core format
requirements (for example, if the frame is too long, has an unknown
label,\ etc.). Moreover, frames may be discarded due to internal network
conditions, or other possible reasons such as throughput enforcement.
.PP
The terminals operate end\(hyto\(hyend with the complete I.441* protocol.
In all other cases, the frame is relayed to one of the adjacent nodes according
to the routing plan established at call set\(hyup time, or at subscription
time (if the network is providing a permanent virtual circuit service).
.PP
No additional U\(hyplane functions (see Note) visible to the users are
performed by the network. If needed by the application, additional functions
are performed end\(hyto\(hyend by layer(s) above the core functions.
.PP
\fINote\fR \ \(em\ Some additional auxiliary U\(hyplane functions such
as reset or explicit congestion control may be defined if needed from the
service
perspective.
.RT
.sp 1P
.LP
A.2.3
\fIFrame switching\fR
.sp 9p
.RT
.PP
The U\(hyplane configuration for this service is shown in
Figure\ A\(hy3/I.122.
.RT
.PP
Figure A\(hy3/I.122 shows the network in a generic way and
illustrates all functions up to and including layer\ 3. In a specific
network, frame switching must be implemented in at least one node in the
network.
.bp
.RT
.LP
.rs
.sp 15P
.ad r
\fBFigure A\(hy3/I.122, p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
Frame switching can be offered on both basic and primary rate
interfaces and on any ISDN channel (D, B, and H). Some restrictions (e.g.\
frame length) apply when in an end\(hyto\(hyend connection at least one
of the access
channels is the D\(hychannel (16\ kbit/s).
.PP
The bearer service provided by the network at the S/T reference point supports
the full Recommendation\ I.441 function. Received frames that satisfy the
Recommendation\ I.441 procedure are passed on to an adjacent node according
to a routine plan established at call set\(hyup time, or at subscription
time.
.PP
No additional U\(hyplane functions visible to the users are performed in
the network. If needed by the application, additional functions are performed
end\(hyto\(hyend by layer(s) above layer\ 2.
.RT
.sp 1P
.LP
A.2.4
\fIX.25\(hybased additional packet mode\fR
.sp 9p
.RT
.PP
The U\(hyplane configuration can comprise several nodes having layer 1,
layer 2, and layer\ 3 functions as is shown in Figure\ A\(hy4/I.122.
Figure\ A\(hy4/I.122 shows the network in a generic way and illustrates all
functions up to and including layer\ 3. Other configurations with nodes
making use only of the core aspects of Recommendation\ I.441 as defined
in \(sc\ 3.1 of
Recommendation\ I.122 are possible.
.RT
.LP
.rs
.sp 17P
.ad r
\fBFigure A\(hy4/I.122, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
X\(hy25\(hybased additional packet mode service can be offered on both
the basic and primary rate ISDN access interfaces and on any ISDN channel
(D, B,
and H). Some restrictions (e.g.\ packet length) apply when in an end\(hyto\(hyend
connection at least one of the access channels is the D\(hychannel (16\
kbit/s).
.PP
The bearer service provided by the network at the S/T reference point supports
the full Recommendation\ I.441 and the data transfer part of
Recommendation\ X.25 PLP functions.
.PP
The U\(hyplane contains X.25\(hybased layer 3 functions and the C\(hyplane
procedures use Recommendation\ I.451 extended to transfer the parameters
necessary for the establishment and release of virtual circuits
(e.g.\ throughput class, window size,\ etc.). The capability to negotiate some
parameters must also be provided. Whether or not X.25 multiplexing is provided
is for further study.
.PP
X.25 PLP\(hyDTP consists of all X.25 PLP functions with the exception of
the connection establishment and release functions, including user facilities
(supplementary services). The exclusion of other X.25 PLP functions is
for
further study.
\v'1P'
.RT
.ce 1000
ANNEX\ B
.ce 0
.ce 1000
(to Recommendation I.122)
.sp 9p
.RT
.ce 0
.ce 1000
\fBGeneral arrangement for interworking between an ISDN\fR
.sp 1P
.RT
.ce 0
.ce 1000
\fBwhere I.122 bearer services are requested\fR
.ce 0
.ce 1000
\fBand an ISDN or a PSPDN providing service based on Recommendation X.25\fR
.ce 0
.LP
B.1
\fIPossible scenarios\fR
.sp 1P
.RT
.PP
Figure B\(hy1/I.122 shows the interworking arrangements considered.
When the interworking function IWF logically belongs to the ISDN
(Recommendation\ I.122), interworking based on call control mapping takes
place. In the case where the IWF logically belongs to the PSPDN (Recommendation\
X.25) or ISDN (Recommendation\ X.31), interworking based on either call
control
mapping or port access is possible. As shown in the figure, different
interfaces can be specified for the different reference points, depending on
whether the IWF logically belongs to the ISDN (Recommendation\ I.122),
or to the PSPDN (Recommendation\ X.25) or ISDN (Recommendation\ X.31).
.RT
.sp 1P
.LP
B.2
\fIIWF logically belonging to ISDN (Recommendation I.122)\fR
.sp 9p
.RT
.PP
To enable interworking, the I.122 bearer services, in conjunction with
an IWF, should provide full support of the X.213 network layer services.
The association of an ISDN (Recommendation\ I.122) with an IWF in such
a manner could therefore be considered globally as a Type\ I subnetwork,
in the sense
defined in Recommendation\ X.300.
.PP
A PSPDN (Recommendation X.25) or an ISDN (Recommendation X.31) could also
be considered as a Type\ I subnetwork.
.PP
As specified in Recommendation X.300, the interworking arrangement
between two Type\ I subnetworks should be based on Recommendation\ X.75.
.RT
.sp 1P
.LP
B.3
\fIIWF logically belonging to the PSPDN (Recommendation X.25)/ISDN\fR
\fI(Recommendation X.31)\fR
.sp 9p
.RT
.PP
The association of a PSPDN (Recommendation X.25)/ISDN
(Recommendation\ X.31) with an IWF together behaves like a user terminal
requesting I.122 service from an ISDN (Recommendation\ I.122). Therefore, the
interworking arrangement can be based on Recommendation\ I.122.
.PP
In this arrangement, interworking based on either call control mapping
or port access is possible. When port access method is used, existing call
control procedures in Recommendation\ X.25 are used for the control of
virtual circuits.
.bp
.RT
.LP
.rs
.sp 30P
.ad r
\fBFigure B\(hy1/I.122, p.\fR
.sp 1P
.RT
.ad b
.RT
.ce 1000
ANNEX\ C
.ce 0
.ce 1000
(to Recommendation I.122)
.sp 9p
.RT
.ce 0
.ce 1000
\fBSupport of network layer service (X.213)\fR
.sp 1P
.RT
.ce 0
.ce 1000
\fBin an ISDN offering additional packet mode bearer services\fR
.ce 0
.PP
C.1
Network layer service can be provided by using the X.25\(hybased additional
packet mode bearer service. In this case the mapping concerns
enhanced Recommendations\ I.451 and X.25 data transfer functions. In the
case of frame switching and frame relaying, the network layer service can
be provided through the use of enhanced Recommendation\ I.451, with, in
addition:
.sp 1P
.RT
.LP
a)
additional end system functionality, or
.LP
b)
enhanced I.441 functions.
.sp 1P
.LP
C.2
\fIC\(hyplane enhancements\fR
.sp 9p
.RT
.PP
Recommendation I.451 should be enhanced so that the OSI network
service parameters can be paired with Recommendation\ I.451 messages and
information elements for all bearer services. Serveral enhancements to
Recommendation\ I.451 are needed to convey all connection establishment and
release primitives and parameters in relevant I.451 protocol elements.
.bp
.RT
.sp 1P
.LP
C.3
\fIU\(hyplane enhancements\fR
.sp 9p
.RT
.PP
For frame switching and frame relaying, there are two different
approaches for the mapping of data transfer primitives into protocol
elements:
.RT
.LP
1)
layer 3 protocol elements supported by a DTE specific
protocol which is transparent for the network (preferably X.25 PLP), and
.LP
2)
I.441 protocol elements enhanced to map directly into the
OSI network service data transfer primitives.
.PP
Further study is required for the selection and detailed
definition of one of the two options.
\v'1P'
.ce 1000
ANNEX\ D
.ce 0
.ce 1000
(to Recommendation I.122)
.sp 9p
.RT
.ce 0
.ce 1000
\fBCongestion control in frame relaying service\fR
.sp 1P
.RT
.ce 0
.PP
\fINote\fR \ \(em\ This Annex does not cover congestion control in frame
switching and X.25\(hybased additional packet mode bearer services. This
is
because in these services, there is termination of user data transfer protocol
in the network and so existing mechanisms for congestion control can be
used.
.sp 1P
.RT
.sp 1P
.LP
D.1
\fIGeneral objectives of\fR \fIcongestion control\fR
.sp 9p
.RT
.PP
The term \*Qcongestion control\*U as used here refers to a set of
mechanisms incorporated to attain certain network performance objectives,
particularly in the peak periods, while optimizing or improving the network
resource requirements.
.RT
.LP
1)
The network should, with high probability, meet the Quality of Service
in terms of throughput, delay and availability negotiated with the user.
Therefore, the number of occurrences of user perceived congestion should
be minimized.
.LP
2)
Under heavy load, the network should not allow user
interference to the extent where one user can monopolize network resource
usage at the expense of other users.
.PP
Specific congestion control mechanisms to achieve these objectives are
for further study. One possible approach of congestion control is presented
below.
.sp 1P
.LP
D.2
\fIUser reaction to network congestion\fR
.sp 9p
.RT
.PP
The network has no other direct control on the data flow of a user other
than dropping frames. It does so without sending explicit congestion
control messages to the user. Frame discard by a network may have charging
implications. This requires further study.
.PP
Users should reduce their information transfer rate when they perceive
the impact of network congestion. Reduction of throughput by a user may
well
result in an increase of the effective throughput available to the user
during congestion.
.PP
It is suggested that a user of frame relaying 1 service implement some
form of congestion\(hysensitive adaptation function that has the following
characteristics:
.RT
.LP
i)
no blocking of data flow under normal conditions,
.LP
ii)
reduction to a lower throughput upon detection of network congestion,
.LP
iii)
progressive increase to the maximum negotiated throughput upon congestion
abatement.
.PP
For frame relaying 2 service, the user is required to implement
the above congestion\(hysensitive adaptation function through the use of the
windowing mechanism in Recommendation\ I.441. In this case, the user will
base the detection of congestion on events available in the I.441 elements
of
procedure (e.g.\ receipt of a REJECT frame, detection of frame loss,\ etc.).
The user dynamically adjusts its window size in accordance with network
congestion condition.
.bp
.sp 1P
.LP
D.3
\fIControl action by the network congestion\fR
.sp 9p
.RT
.PP
Users of frame relaying services should reduce their information
transfer rate when they perceive the impact of network congestion (see
\(sc\ 2).
But the network cannot rely solely on the user's behaviour to control network
congestion. This is the case for both frame relaying\ 1 and frame relaying\
2
services.
.PP
The network should monitor the throughput of each call/interface and exercise
a frame discard strategy under congestion conditions, for those
calls/interfaces that exceed their negotiated throughput. However, because
congestion can occur even when the calls do not exceed their negotiated
throughput (e.g.\ network failures), the network should discard frames
in a way that assures some fairness among users.
.PP
The selection of mechanism(s) which may be used by the network for
this purpose are for further study.
.RT
.LP
.rs
.sp 43P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.ce 1000
\v'3P'
SECTION\ 3
.ce 0
.sp 1P
.ce 1000
\fBGENERAL MODELLING METHODS\fR
.ce 0
.sp 1P
.sp 2P
.LP
\fBRecommendation\ I.130\fR
.RT
.sp 2P
.ce 1000
\fBMETHOD FOR THE CHARACTERIZATION OF TELECOMMUNICATION\fR
.EF '% Fascicle\ III.7\ \(em\ Rec.\ I.130''
.OF '''Fascicle\ III.7\ \(em\ Rec.\ I.130 %'
.ce 0
.ce 1000
\fBSERVICES SUPPORTED BY AN ISDN AND NETWORK\fR
.ce 0
.sp 1P
.ce 1000
\fBCAPABILITIES OF AN ISDN\fR
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral considerations\fR
.sp 1P
.RT
.PP
The concept and the principles of ISDNs are described in
Recommendation\ I.120. The purpose of this Recommendation is to provide
a method for the characterization of telecommunication services (including
supplementary services) and a definition of the needed network capabilities
in an ISDN, in
order to support the identified services.
.PP
The main objectives are:
.RT
.LP
a)
to give a common framework and tools to be adopted for
service description;
.LP
b)
to show how, starting from the service definition, it is
possible to define protocols and network resources for providing such
services;
.LP
c)
to make reference to those Recommendations which are
relevant to the above two points.
.sp 2P
.LP
\fB2\fR \fBStructure and application of the overall method\fR
.sp 1P
.RT
.PP
The method is divided into three main stages of activity: service aspects
(stage\ 1), functional network aspects (stage\ 2) and network
implementation aspects (stage\ 3).
.PP
Within each stage a number of steps have been identified, as shown in Figure\
1/I.130. In principle, the application of the method is sequential,
stage\ 1 given the service description from the user point of view, stage\ 2
offering an intermediate view of what happens at the user\(hynetwork interface
and inside the network between different exchanges, and stage\ 3 giving
the actual switching and service nodes descriptions, as well as protocols
and format to be adopted.
.PP
In order to classify and relate the various Recommendations relevant to
the method, a three level structure is used where each level applies to
the three above\(hymentioned stages.
.PP
Level\ 1 is a description of the overall method, and is contained in
this Recommendation.
.PP
Level\ 2 identifies and defines the tools for the work within each
stage. Examples of these tools are frameworks for service prose descriptions,
libraries of pre\(hydefined functions, graphical conventions,\ etc. All
these tools are covered by Recommendations.
.PP
Level\ 3 is the actual application of the method to each individual
service and is contained in various Recommendations.
.PP
The application of the method for stage\ 1 results in a description of
the service. Stage\ 2 results in one or more implementation independent
scenarios, and stage\ 3 results in a set of protocol and switching
Recommendations needed to realize the service for each scenario.
.PP
Figure\ 2/I.130 illustrates the concept of levels in relation to
various Recommendations relevant to the method.
.bp
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure 1/I.130, p. 8\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 2/I.130, p. 9\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB3\fR \fBDescription of the method\fR
.sp 1P
.RT
.PP
As referred to in \(sc\ 2 above, there are three stages of the method as
follows:
.PP
Stage\ 1 is an overall service description from the user's standpoint.
.PP
Stage\ 2 is an overall description of the organization of the network functions
to map service requirements into network capabilities.
.PP
Stage\ 3 is the definition of switching and signalling capabilities
needed to support services defined in stage\ 1.
.PP
Each stage consists of several steps.
.RT
.sp 1P
.LP
3.1
\fIStage 1\fR
.sp 9p
.RT
.PP
Stage\ 1 is an overall service description from the user's point of view,
but does not deal with the details of the human interface itself. The
stage\ 1 service description is independent of the amount of functionality in
the user's terminal, other than that required to provide the human interface.
For example the conference calling service description is designed to be
independent of whether the conference bridge is in the terminal, in the
serving exchange or elsewhere.
.PP
The steps in stage\ 1 are:
.RT
.LP
\fIStep 1.1\ \(em\ Service prose definition and description\fR
.LP
This step describes the service in terms of the perceptions of the user
receiving the service and any other users involved in the service. It
describes events in a generic term which does not constrain terminal or
network design. It is intended to allow an understanding of the service
without regard to implementation. The description should include operational,
control,
interworking and administrative aspects as well as interactions with other
sevices. A detailed format and list of definitions for terms used for service
prose definition and description is contained in Recommendation\ I.210.
.LP
\fIStep 1.2\ \(em\ Static description of the service using attributes\fR
.LP
The static, that is, time\(hyindependent, aspects of a service can, in
some cases, be efficiently described by attributes. An attribute is a
characteristic or functional description which is common to several services
and therefore needs to be described in detail only once. Subsequently,
it can be referred to by a name or other designation. Within the scope
of an attribute definition there may be multiple parameters or identified
functional variations which are called attribute values.
.LP
The attribute technique is described more fully in
Recommendation\ I.140. It contains an outline of the technique and definitions
of attributes and attributes values, valid for both services and connection
types. The attributes and attribute values identified for services can
be found in Rec.\ I.210 (Annexes\ B and\ C) for bearer services and for
teleservices. The use of the attribute technique in the description of
supplementary services
is for further study.
.LP
\fIStep 1.3\ \(em\ Dynamic description of the service using\fR
\fIgraphic means\fR
.LP
The dynamic description of a service contains all the information that
is sent and received by the user from activation invocation of the service
to completion of the service. The information is presented in the form
of an
overall Specification and Description Language\ (SDL) diagram. An overall SDL
diagram is a flow chart which identifies all possible actions relevant
to the service as perceived by the user. It treats the network as a single
entity,
that is, no information flows within the network are considered. The method
of using the overall SDL diagrams for service description is given in
Recommendation\ I.210, Annex\ D.
.sp 1P
.LP
3.2
\fIStage 2\fR
.sp 9p
.RT
.PP
Stage 2 identifies the functional capabilities and the information flows
needed to support the service as described in stage\ 1. The stage\ 2
description will also include user operations not directly associated with a
call (e.g.\ user change of call forwarding parameters via his sevice interface)
as described in stage\ 1. Furthermore, it identifies various possible physical
locations for the functional capabilities. The output of stage\ 2 which
is
signalling system independent is used as an input to the design of signalling
system and exchange switching Recommendations.
.bp
.PP
The steps in stage\ 2 are:
.RT
.LP
\fIStep 2.1\ \(em\ Derivation of a functional model\fR
.LP
A functional model is derived for each basic and for each
supplementary service. The functions required to provide the service are
grouped into functional entities. The functional model is the aggregate
of the functional entities and their relationships. The concept of a functional
entity is contained in the ISDN functional principles Recommendation\ (I.310).
In the case of supplementary services the relationship between the supplementary
service and the basic service is shown by a composite functional model.
.LP
\fIStep 2.2\ \(em\ Information flow diagrams\fR
.LP
The distribution of the functions needed to provide a service as defined
by the functional model requires that interactions be defined between functional
entities. Such an interaction is referred to as an \*Q
information flow
\*U and has a name descriptive of the intent of the information flow.
Information flow diagrams are created for successful operation and may be
created as appropriate for other cases. The semantic meaning and information
content of each information flow is determined.
.LP
\fIStep 2.3\ \(em\ SDL diagrams for functional entities\fR
.LP
The functions performed within a functional entity are identified and
represented in the form of a Specification and Description Language (SDL)
diagram. The inputs and outputs of the SDL diagram are to and from the
users as described in stage\ 1 and are information flows to and from other
functional
entities.
.LP
SDL diagrams are defined for each functional entity based on the information
flows defined for the successful operation of the service. The SDL diagram
also covers the unsuccessful cases.
.LP
\fIStep 2.4\ \(em\ Functional entity actions\fR
.LP
The actions performed within a functional entity are represented as a
list, or sequence, of functional entity actions\ (FEAs) in prose form.
These form the basis for understanding the meaning of the information
flows and provide a basis for the stage\ 3 switching Recommendations.
.LP
\fINote\fR \ \(em\ The relationship between the FEAs and the elementary
functions\ (EFs), as listed in Recommendation\ I.310 is for further study.
.LP
\fIStep 2.5\ \(em\ Allocation of functional entities to physical\fR
\fIlocations\fR
.LP
In this step, the functional entities and information flows
identified in previous steps are allocated to specific types of physical
locations,\ e.g. a PABX or an exchange. Each allocation is called a scenario.
The relationship supported between two functional entities located in different
physical locations must be realized wihin protocol(s) supported between
those locations.
.LP
The detailed procedures and formats used and the concepts needed for
the stage\ 2 description can be found in Recommendations\ Q.65 and I.310.
.sp 1P
.LP
3.3
\fIStage 3\fR
.sp 9p
.RT
.PP
In stage\ 3 the information flow and SDL diagrams from the stage\ 2 output
form the basis for producing the signalling system protocol
Recommendations and the switching Recommendations.
.PP
The steps in stage\ 3 will need to be repeated for each service where,
because of different allocations of functional entities to physical locations,
different protocols and procedures are needed.
.PP
The steps in stage\ 3 are:
.RT
.LP
\fIStep 3.1\ \(em\ Protocols and formats\fR
.LP
The messages needed to support the information flows and the
modifications to existing information flows between the nodes are identified
and the detailed message elements and procedures are designed into the
relevant signalling systems.
.LP
\fIStep 3.2\ \(em\ Switching and service nodes\fR
.LP
The requirements identified for switching functions (functional
entity actions) are incorporated into the switching Recommendations
(Q.500\(hySeries).
.bp
.LP
\fBMONTAGE : PAGE 84 = PAGE BLANCHE\fR
.sp 1P
.RT
.LP
.bp
.sp 1P
.ce 1000
\v'3P'
SECTION\ 4
.ce 0
.sp 1P
.ce 1000
\fBTELECOMMUNICATION NETWORK AND SERVICE ATTRIBUTES\fR \v'1P'
.ce 0
.sp 1P
.sp 2P
.LP
\fBRecommendation\ I.140\fR
.RT
.sp 2P
.LP
.EF '% Fascicle\ III.7\ \(em\ Rec.\ I.140''
.OF '''Fascicle\ III.7\ \(em\ Rec.\ I.140 %'
.ce 1000
\fBATTRIBUTE TECHNIQUE FOR THE CHARACTERIZATION OF\fR
.ce 0
.ce 1000
\fBTELECOMMUNICATION SERVICES SUPPORTED BY AN\fR
.ce 0
.sp 1P
.ce 1000
\fBISDN AND NETWORK CAPABILITIES OF AN ISDN\fR
.ce 0
.sp 1P
.ce 1000
\fI(former Recommendation I.130 of the Red Book;\fR
.sp 9p
.RT
.ce 0
.sp 1P
.ce 1000
\fIamended at Melbourne, 1988)\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral considerations\fR
.sp 1P
.RT
.PP
The purpose of this Recommendation is to introduce the attribute
technique and to describe attributes and list attribute values. Attributes
are used in the characterization of services and network capabilities provided
by an ISDN. The attribute technique can also be used to describe the salient
features of other objects of study in telecommunications, e.g.\ charging.
.PP
This Recommendation (in the general\ I.100\(hySeries) will act as a
library of all attributes and attribute values used in other
I\(hySeries\ Recommendations. The inclusion of a particular attribute value
in this Recommendation does not mean that this particular object is being
recommended by CCITT, but that it is a potential attribute (or attribute
value) which may be used in a particular Recomendation in the\ I\(hySeries
(e.g.\ to describe a
CCITT\(hyrecommended service).
.PP
Annex\ A includes all attributes and their values so far identified and
defined.
.RT
.sp 2P
.LP
\fB2\fR \fBAttribute technique\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
\fIOutline of the technique\fR
.sp 9p
.RT
.PP
This technique is used to describe objects in a structured, simple manner
and to highlight the important aspects of the object. In order to be
able to identify comparable objects, e.g.\ bearer services, the general
concept of the object is broken down in a number of salient features. The
salient
features are termed \fIattributes\fR . | ach attribute is independent
of the others so that a change in the value of one will not affect the
others. To describe a particular object the attributes are assigned values
which identify that
object.
.PP
It is not always necessary or useful to describe an object in great
detail and so attributes have been graded into three levels:
.RT
.LP
\(em
dominant attributes
: these define a sub\(hyset
containing similar objects, this sub\(hyset is termed a class or category;
.LP
\(em
secondary attributes
: these define a particular
object; and
.LP
\(em
qualifying attributes
: these define variants of an
object.
.PP
Characterization of attributes should be used in the I\(hySeries of Recommendations
when appropriate.
.bp
.sp 1P
.LP
2.2
\fIBasic rules\fR
.sp 9p
.RT
.LP
\(em
Each attribute is assigned a name and definition.
.LP
\(em
Some attributes may apply to only one object, others may be applicable
to several objects. In this case the same attribute name is used.
.LP
\(em
A given value should have the same name and definition in all Recommendations.
.LP
\(em
Depending on the nature of the object described, a particular attribute
may need to be used more than once.
.LP
\(em
Each attribute should be described by three perspectives;
generic, service and network.
.sp 2P
.LP
2.3
\fIAttribute lists\fR
.sp 1P
.RT
.sp 1P
.LP
2.3.1
\fIGeneric attributes\fR
.sp 9p
.RT
.LP
Information transfer mode
.LP
Information transfer rate
.LP
Information transfer capability
.LP
Establishment
.LP
Symmetry
.LP
Configuration
.LP
Structure
.LP
Channel (rate)
.LP
Control protocol
.LP
Information transfer protocol
.LP
Performance
.LP
Interworking
.LP
Operations
.LP
Type of user information
.LP
High layer protocol
.PP
\fINote\fR \ \(em\ This list will be completed according to further results
on studies of connectionless, multi\(hymedia, broadband and mobile services.
.sp 2P
.LP
2.3.2
\fIService attributes\fR
.sp 1P
.RT
.sp 1P
.LP
2.3.2.1
\fIBearer services\fR
.sp 9p
.RT
.LP
1
Information transfer mode
.LP
2
Information transfer rate
.FS
Service information transfer
rate considered at the access point.
.FE
.LP
3
Information transfer capability
.LP
4
Structure
.LP
5
Establishment of communication
.LP
6
Symmetry
.LP
7
Communication configuration
.LP
8
Access channel and rate
.LP
9\(hy1
Signalling access protocol layer 1
.LP
9\(hy2
Signalling access protocol layer 2
.LP
9\(hy3
Signalling access protocol layer 3
.LP
Information access protocol (layer\ 1\(hy3) at the access point.
.FE
9\(hy4
Information access protocol layer 1
.LP
9\(hy5
Information access protocol layer 2
.LP
9\(hy6
Information access protocol layer 3
.LP
10
Supplementary services provided
.LP
11
Quality of service
.LP
12
Interworking possibilities
.LP
13
Operational and commercial
.LP
.sp 1
.bp
.sp 1P
.LP
2.3.2.2
\fITeleservices\fR
.sp 9p
.RT
.PP
1, 2, 3, 4, 5, 6, 7, 8, 9\(hy1, 9\(hy2, 9\(hy3, 9\(hy4, 9\(hy5, 9\(hy6:
refer to \(sc\ 2.3.2.1.
.RT
.LP
10
Type of user information
.LP
11
Layer 4 protocol
.LP
12
Layer 5 protocol
.LP
13
Layer 6 protocol
.LP
14
Layer 7 protocol
.LP
15
Supplementary services provided
.LP
16
Quality of service
.LP
17
Interworking possibilities
.LP
18
Operational and commercial
.sp 1P
.LP
2.3.2.3
\fISupplementary services\fR
.sp 9p
.RT
.PP
For further study.\fR
.RT
.sp 1P
.LP
2.3.2.4
\fICharging\fR
.sp 9p
.RT
.PP
For further study.
.RT
.sp 2P
.LP
2.3.3
\fINetwork attributes\fR
.sp 1P
.RT
.sp 1P
.LP
2.3.3.1
\fIConnection types\fR
.sp 9p
.RT
.LP
1
Information transfer mode
.LP
2
Information transfer rate
.FS
Information transfer rate is
considered between access points.
.FE
.LP
3
Information transfer susceptance
.LP
4
Establishment of communication
.LP
5
Symmetry
.LP
6
Connection configuration
.LP
7
Structure
.LP
8
Channel (rate)
.LP
9
Connection control protocol
.LP
10
Information transfer coding/protocol
.FS
Information
transfer protocol is considered between access points.
.FE
.LP
11
Network performance
.LP
12
Network interworking
.LP
13
Operations and management
.sp 1P
.LP
2.3.3.2
\fIConnection elements\fR
.sp 9p
.RT
.LP
1
Information transfer mode
.LP
2
Information transfer rate
.LP
3
Information transfer susceptance
.LP
4
Establishment of communication
.LP
5
Symmetry
.LP
6
Connection configuration
.LP
7
Structure
.LP
8
Channel (rate)
.LP
9
Connection control protocol
.LP
10
Information transfer coding/protocol
.LP
11
Network performance
.LP
12
Network interworking
.LP
13
Operations and management
.LP
.sp 1
.bp
.sp 1P
.LP
2.3.3.3
\fIOther network entities\fR
.sp 9p
.RT
.PP
The definition of attributes for basic connection components, and network
capabilities to support supplementary services needs further
study.
.RT
.sp 1P
.LP
2.4
\fIAttribute definition\fR
.sp 9p
.RT
.PP
A list of definitions of attributes and attribute values is
contained in Annex\ A to this Recommendation.
.RT
.sp 2P
.LP
\fB3\fR \fBApplication to the I\(hySeries Recommendations\fR
.sp 1P
.RT
.PP
This technique has been applied in I.200\(hySeries Recommendations for
the specification of the telecommunications services supported by and ISDN
and in Recommendation\ I.340 for the characterization of ISDN connection
types and connection elements.
.PP
The application of the attribute technique for the characterization of
multi\(hymedia services is for further study.
\v'1P'
.RT
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation I.140)
.sp 9p
.RT
.ce 0
.ce 1000
\fBList of definitions of \fR \fBattributes\fR
.sp 9p
.RT
.ce 0
.ce 1000
\fBand \fR \fBattribute values\fR
.ce 0
.LP
A.1
\fIDefinitions of the attributes\fR
.sp 1P
.RT
.sp 2P
.LP
A.1.1
\fITelecomunication service attribute definitions\fR
.sp 1P
.RT
.sp 1P
.LP
\fBInformation transfer mode\fR
.sp 9p
.RT
.PP
This attribute describes the operational mode for transferring
(transporting and switching) user information through the ISDN.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ circuit
.sp 1P
.RT
.LP
\(em\ packet
.sp 1P
.LP
\fBInformation transfer rate\fR
.sp 9p
.RT
.PP
This attribute describes either the bit rate (circuit mode) or the throughput
(packet mode). It refers to the transfer of digital information at the
access points.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ appropriate bit or throughput rate
.sp 1P
.RT
.sp 1P
.LP
\fBInformation transfer capability\fR
.sp 9p
.RT
.PP
This attribute describes the capability associated with the
transfer of different types of information through the ISDN.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ unrestricted digital information
.sp 1P
.RT
.LP
\(em\ speech
.LP
\(em\ 3.1 kHz audio
.LP
\(em\ 7 kHz audio
.LP
\(em\ 15 kHz audio
.LP
\(em\ video
.LP
\(em\ other values
.bp
.sp 1P
.LP
\fBStructure\fR
.sp 9p
.RT
.PP
This attribute refers to the capability of the ISDN to deliver
information to the destination access point or reference point in a structure
(e.g.\ time interval for circuit mode, service data unit for packet mode),
that was presented in a corresponding signal structured at the origin (access
point or reference point).
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ 8 kHz integrity
.sp 1P
.RT
.LP
\(em\ service data unit integrity
.LP
\(em\ time slot sequence integrity
.LP
\(em\ restricted differential time delay
.LP
\(em\ unstructured
.sp 1P
.LP
\fBEstablishment of communication\fR
.sp 9p
.RT
.PP
This attribute describes the mode of establishment associated to the telecommunication
service used to establish and release a given
communication.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ demand
.sp 1P
.RT
.LP
\(em\ reserved
.LP
\(em\ permanent
.sp 1P
.LP
\fBSymmetry\fR
.sp 9p
.RT
.PP
This attribute describes the relationship of information flow
between two (or more) access points or reference points involved in a
communication.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ unidirectional
.sp 1P
.RT
.LP
\(em\ bidirectional symmetric
.LP
\(em\ bidirectional asymmetric
.sp 1P
.LP
\fBCommunication configuration\fR
.sp 9p
.RT
.PP
This attribute describes the spatial arrangement for transferring information
between two or more access points. It completes the structure
associated with a telecommunication service as it associates the relationship
between the access points involved and the flow of information between
these
access points.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ point\(hyto\(hypoint
.sp 1P
.RT
.LP
\(em\ multipoint
.LP
\(em\ broadcast
.sp 1P
.LP
\fBAccess channel and rate\fR
.sp 9p
.RT
.PP
This attribute describes the channels and their bit rate used to transfer
the user information and/or signalling information at a given access point.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ name of the channel (letter) and the corresponding bit rate
.sp 1P
.RT
.PP
\fINote\fR \ \(em\ This attribute can be used several times for
communication characterization.
.sp 1P
.LP
\fBSignalling access protocol layer\ 1\(hy3, information access
protocol layer\ 1\(hy3\fR
.sp 9p
.RT
.PP
These attributes characterize the protocol on the signalling or
user information transfer channel at a given access point or reference
point.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ appropriate protocol
.bp
.sp 1P
.RT
.sp 1P
.LP
\fBType of user information\fR
.sp 9p
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ speech
.sp 1P
.RT
.LP
\(em\ sound
.LP
\(em\ text
.LP
\(em\ facsimile
.LP
\(em\ text\(hyfacsimile
.LP
\(em\ videotex
.LP
\(em\ video
.LP
\(em\ text\(hyinteractive
.sp 1P
.LP
\fBLayer 4\ \(em\ 7 protocol\fR
.sp 9p
.RT
.PP
These attributes characterize the protocol on the user information transfer
channel at a given access point or reference point.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ appropriate protocol
.sp 1P
.RT
.sp 1P
.LP
\fBSupplementary services provided\fR
.sp 9p
.RT
.PP
This attribute refers to the supplementary services associated
with a given telecommunication service.
.RT
.sp 1P
.LP
\fBQuality of service\fR
.sp 9p
.RT
.PP
This attribute is described by a group of specific sub\(hyattributes, for
example: service reliability, service availability.
.PP
The values are under study.
.RT
.sp 1P
.LP
\fBInterworking possibilities\fR
.sp 9p
.RT
.PP
To be defined.
.RT
.sp 1P
.LP
\fBOperational and commercial\fR
.sp 9p
.RT
.PP
To be defined.
.RT
.sp 2P
.LP
A.1.2
\fIConnection type attribute definitions\fR
.sp 1P
.RT
.sp 1P
.LP
\fBInformation transfer mode\fR
.sp 9p
.RT
.PP
This attribute describes the operational mode for transferring
(transporting and switching) user information through the ISDN.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ circuit
.sp 1P
.RT
.LP
\(em\ packet
.sp 1P
.LP
\fBInformation transfer rate\fR
.sp 9p
.RT
.PP
This attribute describes either the bit rate (circuit mode) or the throughput
(packet mode). It refers to the transfer of digital information
between access points or reference points.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ appropriate bit or throughput rate
.sp 1P
.RT
.sp 1P
.LP
\fBInformation transfer susceptance\fR
.sp 9p
.RT
.PP
This attribute describes the capability associated with the
transfer of different types of information through the ISDN.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ unrestricted digital information
.sp 1P
.RT
.LP
\(em\ speech
.LP
\(em\ 3.1 kHz audio
.LP
\(em\ 7 kHz audio
.LP
\(em\ 15 kHz audio
.LP
\(em\ video
.LP
\(em\ other values
.bp
.sp 1P
.LP
\fBEstablishment of connection\fR
.sp 9p
.RT
.PP
This attribute describes the mode of establishment used to
establish and release a given connection in an ISDN.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ demand
.sp 1P
.RT
.LP
\(em\ semi\(hypermanent
.LP
\(em\ permanent
.sp 1P
.LP
\fBSymmetry\fR
.sp 9p
.RT
.PP
This attribute describes the relationship of information flow
between two (or more) access points or reference points of a connection.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ unidirectional
.sp 1P
.RT
.LP
\(em\ bidirectional symmetric
.LP
\(em\ bidirectional asymmetric
.sp 1P
.LP
\fBConnection configuration\fR
.sp 9p
.RT
.PP
This attribute describes the spatial arrangement for transferring information
on a given connection. It consists of two sub\(hyattributes, topology and
dynamics.
.RT
.sp 1P
.LP
\fBStructure\fR
.sp 9p
.RT
.PP
This attribute refers to the capability of the ISDN to deliver
information to the destination access point or reference point in a structure
(e.g.\ time interval for circuit mode, service data unit for packet mode),
that was presented in a corresponding signal structured at the origin (access
point or reference point).
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ 8 kHz integrity
.sp 1P
.RT
.LP
\(em\ service data unit integrity
.LP
\(em\ time slot sequence integrity
.LP
\(em\ restricted differential time delay
.LP
\(em\ unstructured
.sp 1P
.LP
\fBChannel (rate)\fR
.sp 9p
.RT
.PP
This attribute describes the channels and their bit rate used to transfer
the user information and/or signalling information at a given access point.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ name of the channel (letter) and the corresponding bit rate
.sp 1P
.RT
.PP
\fINote\fR \ \(em\ This attribute can be used several times.
.sp 1P
.LP
\fBConnection control protocol, information transfer
coding/protocol\fR
.sp 9p
.RT
.PP
These attributes characterize the protocol/coding on the
signalling or user information transfer channel at a given access point or
reference point.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ appropriate protocol or coding
.sp 1P
.RT
.sp 1P
.LP
\fBNetwork performance\fR
.sp 9p
.RT
.PP
This attribute describes the network performance that relates to an ISDN
connection.
.bp
.PP
This performance attribute consists of sub\(hyattributes, for
example:
.RT
.LP
\fIError performance\fR : the values are given in the appropriate
Recommendations.
.LP
\fISlip performance\fR : the values are given in the appropriate
Recommendations.
.PP
The definition of further sub\(hyattributes is for further study.
.sp 1P
.LP
\fBNetwork interworking\fR
.sp 9p
.RT
.PP
To be defined.
.RT
.sp 1P
.LP
\fBOperation and management\fR
.sp 9p
.RT
.PP
To be defined.
.RT
.sp 2P
.LP
A.1.3
\fIConnection element attribute defintions\fR
.sp 1P
.RT
.sp 1P
.LP
\fBInformation transfer mode\fR
.sp 9p
.RT
.PP
This attribute describes the operational mode for transferring
(transporting and switching) user information through the ISDN.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ circuit
.sp 1P
.RT
.LP
\(em\ packet
.sp 1P
.LP
\fBInformation transfer rate\fR
.sp 9p
.RT
.PP
This attribute describes either the bit rate (circuit mode) or the throughput
(packet mode). It refers to the transfer of digital information
between access points or reference points.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ appropriate bit or throughput rate
.sp 1P
.RT
.sp 1P
.LP
\fBInformation transfer susceptance\fR
.sp 9p
.RT
.PP
This attribute identifies equipment which may restrict the types of information
which may pass through the ISDN.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ speech processing equipment
.sp 1P
.RT
.LP
\(em\ echo suppression equipment
.LP
\(em\ multi\(hysatellite hope
.LP
\(em\ null
.sp 1P
.LP
\fBEstablishment of connection\fR
.sp 9p
.RT
.PP
This attribute describes the mode of establishment used to
establish and release a given connection element in an ISDN.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ demand
.sp 1P
.RT
.LP
\(em\ semi\(hypermanent
.LP
\(em\ permanent
.sp 1P
.LP
\fBSymmetry\fR
.sp 9p
.RT
.PP
This attribute describes the relationship of information flow
between two (or more) access points or reference points of a connection
element.
.bp
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ undirectional
.sp 1P
.RT
.LP
\(em\ bidirectional symmetric
.LP
\(em\ bidirectional asymmetric
.sp 1P
.LP
\fBConnection configuration\fR
.sp 9p
.RT
.PP
This attribute describes the spatial arrangement for transferring information
across a given connection element. It consists of two
sub\(hyattributes, topology and uniformity.
.RT
.sp 1P
.LP
\fBStructure\fR
.sp 9p
.RT
.PP
This attribute refers to the capability of the ISDN to deliver
information to the destination access point or reference point in a structure
(e.g.\ time interval for circuit mode, service data unit for packet mode),
that was presented in a corresponding signal structured at the origin (access
point or reference point).
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ 8 kHz integrity
.sp 1P
.RT
.LP
\(em\ service data unit integrity
.LP
\(em\ time slot sequence integrity
.LP
\(em\ 8 kHz integrity with restricted differential time delay
.LP
\(em\ unstructured
.sp 1P
.LP
\fBChannel (rate)\fR
.sp 9p
.RT
.PP
This attribute describes the channels and their bit rate used to transfer
the user information and/or signalling information at a given access point.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ name of the channel (letter) and the corresponding bit rate
.sp 1P
.RT
.PP
\fINote\fR \ \(em\ This attribute can be used several times.
.sp 1P
.LP
\fBConnection control protocol, information transfer
coding/protocol\fR
.sp 9p
.RT
.PP
These attributes characterize the protocol/coding on the
signalling or user information transfer channel at a given access point or
reference point.
.RT
.sp 2P
.LP
\fIPossible values\fR :
\(em\ appropriate protocol or coding
.sp 1P
.RT
.sp 1P
.LP
\fBNetwork performance\fR
.sp 9p
.RT
.PP
This attribute describes the network performance that relate to an ISDN
connection element.
.PP
This performance attribute consists of sub\(hyattributes, for
example:
.RT
.LP
\fIError performance\fR : The values are given in the appropriate
Recommendations.
.LP
\fISlip performance\fR : The values are given in the appropriate
Recommendations.
.PP
The definition of further sub\(hyattributes is for further
study.
.sp 1P
.LP
\fBNetwork interworking\fR
.sp 9p
.RT
.PP
To be defined.
.RT
.sp 1P
.LP
\fBOperation and management\fR
.sp 9p
.RT
.PP
To be defined.
.bp
.RT
.sp 2P
.LP
A.2
\fIDefinition of the attribute values\fR
.sp 1P
.RT
.sp 1P
.LP
\fBunrestricted digital information\fR
.sp 9p
.RT
.PP
Transfer of information sequence of bits at its specified bit rate without
alteration.
.RT
.LP
This\ implies:\ \(em\ bit sequence independence
.LP
This\ implies:\
\(em\ digit sequence integrity
.LP
This\ implies:\
\(em\ bit integrity.
.sp 1P
.LP
\fBspeech\fR
.sp 9p
.RT
.PP
Digital representation of speech coded according to a specified
encoding rule (e.g.\ A\(hylaw, \(*m\(hylaw).
.RT
.sp 1P
.LP
\fB3.1 kHz audio\fR
.sp 9p
.RT
.PP
Digital representation of audio information such as voice\(hyband
data and speech with a bandwidth of 3.1\ kHz, the encoding rule being specified
(e.g.\ A\(hylaw, \(*m\(hylaw).
.RT
.sp 1P
.LP
\fB7 kHz audio\fR
.sp 9p
.RT
.PP
Digital representation of audio information with a bandwidth of
7\ kHz, the encoding rule being specified.
.RT
.sp 1P
.LP
\fB15 kHz audio\fR
.sp 9p
.RT
.PP
Digital representation of audio information with a bandwidth of
15\ kHz, the encoding rule being specified.
.RT
.sp 1P
.LP
\fBvideo\fR
.sp 9p
.RT
.PP
Digital representation of video image information, the encoding
rule being specified.
.RT
.sp 1P
.LP
\fB8 kHz integrity\fR
.sp 9p
.RT
.PP
This value applies when:
.RT
.LP
i)
at each user\(hynetwork interface, intervals of 125 \(*ms are
implicitly or explicitly demarcated, and
.LP
ii)
all bits submitted within a single demarcated 125 \(*ms
interval
are delivered within a corresponding single demarcated 125\ \(*ms interval.
.sp 1P
.LP
\fBservice data unit integrity\fR
.sp 9p
.RT
.PP
This value applies when:
.RT
.LP
i)
at each user\(hynetwork interface, protocols provide a
mechanism
for identifying the boundaries of service data units (e.g.\ X.25 complete
packet sequence), and
.LP
ii)
all bits submitted within a single service data unit are
delivered in a corresponding service data unit.
.sp 1P
.LP
\fBunstructured\fR
.sp 9p
.RT
.PP
This value is applicable when the telecommunication service or
connection neither provides structural boundaries nor preserves structural
integrity.
.RT
.sp 1P
.LP
\fBdemand (communication)\fR
.sp 9p
.RT
.PP
The communication can be started as soon as possible after the
request is made (e.g.\ \fIt\fR\d1\u\ \(em\ \fIt\fR\d0\uis as short as possible).
.PP
Communication and connection release occurs in response to the request
of any of the users (calling or called users), \fIt\fR\d3\u\ \(em\ \fIt\fR\d2\uis
as short as possible (see Figure\ A\(hy1/I.140).
.bp
.RT
.LP
.rs
.sp 18P
.ad r
\fBFigure A\(hy1/I.140, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
\fBreserved (communication)\fR
.sp 9p
.RT
.PP
The communication can be started at time instant \fIt\fR\d1\uexplicitly
specified at the time instant of communication and connection
request, \fIt\fR\d0\u. Communication and connection release occurs at time
instant \fIt\fR\d3\uexplicitly specified also at \fIt\fR\d0\u. Communication
and connection
duration is predetermined: the communication and connection is set up for a
specified period of time. As an option, connection release occurs at time
instant \fIt\fR\d3\ufollowing a release request made at time instant \fIt\fR\d2\uduring
the communication and \fIa priori\fR undetermined (\fIt\fR\d3\u\ \(em\
\fIt\fR\d2\uis as short as possible). This option corresponds to an unspecified
duration of the
communication and connection, or to a possibility of unanticipated release
(see Figure\ A.1/I.140).
.RT
.sp 1P
.LP
\fBpermanent (communication)\fR
.sp 9p
.RT
.PP
The communication can be started after the connection is set up at time
instant \fIt\fR\d1\uin response to a subscription request for the service
at time instant \fIt\fR\d0\u. the duration may be unspecified. The communication
and
connection is released at time instant \fIt\fR\d3\ucorresponding to the
end of the subscription.
.RT
.sp 1P
.LP
\fBswitched (connection)\fR
.sp 9p
.RT
.PP
ISDN circuit switched connections/connection elements are set up at any
time on demand via e.g.\ a bit channel in response to signalling
information received from subscribers, other exchanges or other networks,
i.e.\ on a per\(hycall\(hybasis. Message/packet switched connections/connection
elements provided by an ISDN may be set up on demand via circuit\(hymode
channels (e.g.\ B\(hychannels) and special packet switching units or via
the D\(hychannel
subject to any D\(hychannel priority/flow control restrictions that may be
applicable.
.PP
\fINote\fR \ \(em\ A more general definition of this value is also given in
Recommendation\ I.112 (No.311).
.RT
.sp 1P
.LP
\fBsemi\(hypermanent (connection)\fR
.sp 9p
.RT
.PP
Semi\(hypermanent connections/connection elements pass through a
switching network.
.PP
Semi\(hypermanent connections/connection elements between agreed points may
be provided for an indefinite period of time after subscription, for a fixed
period or for agreed periods during a day, week or other interval.
.bp
.RT
.sp 1P
.LP
\fBpermanent (connection)\fR
.sp 9p
.RT
.PP
Permanent connections/connection elements are described by the
following characteristics:
.PP
Permanent connections/connection elements are available to the
connected subscriber at any time during the period of subscription between
fixed network destination points requested by the subscribers.
.RT
.sp 1P
.LP
\fBunidirectional\fR
.sp 9p
.RT
.PP
This value applies when the information flow of messages is
provided only in one direction.
.RT
.sp 1P
.LP
\fBbidirectional symmetric\fR
.sp 9p
.RT
.PP
This value applies when the information flow characteristics
provided
by the service are the same between two (or more) access points or reference
points in the forward and backward directions.
.RT
.sp 1P
.LP
\fBbidirectional asymmetric\fR
.sp 9p
.RT
.PP
This value applies when the information flow characteristics
provided by the service are different in the two directions.
.RT
.sp 1P
.LP
\fBpoint\(hyto\(hypoint communication\fR
.sp 9p
.RT
.PP
This value applies when there are only two access points.
.RT
.sp 1P
.LP
\fBmultipoint communication\fR
.sp 9p
.RT
.PP
This value applies when more than two access points (see\ Note) are provided
by the service. The exact characteristics of the information flows
must be specified separately based on functions provided by the ISDN.
.PP
\fINote\fR \ \(em\ The number of access points can be undefined.
.RT
.sp 1P
.LP
\fBbroadcast communication\fR
.sp 9p
.RT
.PP
This value applies when more than two access points (see\ Note) are provided
by the service. The information flows from a unique point (source) to the
others (destination) in only one direction.
.PP
\fINote\fR \ \(em\ The number of destination access points is undefined.
.RT
.sp 1P
.LP
\fBpoint\(hyto\(hypoint connection\fR
.sp 9p
.RT
.PP
This value applies when only two end points are provided by the
connection.
.RT
.sp 1P
.LP
\fBmultipoint connection\fR
.sp 9p
.RT
.PP
This value applies when more than two end points are provided by the connection,
and thus many different information flows are possible.
.RT
.sp 1P
.LP
\fBbroadcast connection\fR
.sp 9p
.RT
.PP
To be defined.
.RT
.sp 1P
.LP
\fBsimple connection\fR
.sp 9p
.RT
.PP
A connection consisting of only one connection element.
.RT
.sp 1P
.LP
\fBtandem connection\fR
.sp 9p
.RT
.PP
Two or more connection elements in series form a connection.
.bp
.RT
.sp 1P
.LP
\fBparallel connection\fR
.sp 9p
.RT
.PP
Two or more connection elements in parallel form a
connection.
.RT
.sp 1P
.LP
\fBstar\fR
.sp 9p
.RT
.PP
To be defined.
.RT
.sp 1P
.LP
\fBmesh\fR
.sp 9p
.RT
.PP
To be defined.
.RT
.sp 1P
.LP
\fBuniform\fR
.sp 9p
.RT
.PP
This value applies when all connection elements have the same
attribute values.
.RT
.sp 1P
.LP
\fBnon uniform\fR
.sp 9p
.RT
.PP
This value applies in all other cases.
.RT
.sp 1P
.LP
\fBconcurrent\fR
.sp 9p
.RT
.PP
The configuration of a connection is described as concurrent when all of
the connection elements involved are established simultaneously and
released simultaneously.
.RT
.sp 1P
.LP
\fBsequential\fR
.sp 9p
.RT
.PP
A connection has a sequential configuration when its connection
elements are established and released sequentially i.e.\ only one of several
connection elements or chains of connection elements exists at any given
time.
.RT
.sp 1P
.LP
\fBadd/remove\fR
.sp 9p
.RT
.PP
When connection elements can be established and released while
other connection elements of the same connections still exist, the
configuration of this connection is described as add/remove.
.RT
.sp 1P
.LP
\fBSymmetry and/or topology change\fR
.sp 9p
.RT
.PP
When the symmetry attribute value of the connection element can be changed
during a call.
.RT
.sp 1P
.LP
\fBTime slot sequence integrity\fR
.sp 9p
.RT
.PP
This value applies when
.RT
.LP
i)
at each user\(hynetwork interface, time slots are implicitly or explicitly
demarcated for each access channel of an aggregate of access
channels, and
.LP
ii)
the information parts delivered from the time slots at the receiving
end are in the same order as submitted at the transmitting end.
.PP
\fINote\fR \ \(em\ Preserving the order of bits within an individual time
slot from the transmitting to the receiving end is not part of this
definition.
.sp 1P
.LP
\fB8 kHz integrity with restricted differential time
delay\ (RDTD)\fR
.sp 9p
.RT
.PP
This value applies when the following conditions are
met:
.RT
.LP
\(em
that at each point in a connection or connection element,
time slots are explicity or implicitly demarcated for each information
channel or an aggregate of information channels; and
.LP
\(em
that the information parts submitted to the time slots at the transmitting
end are delivered to the receiving end with a differential time
delay of not more than 50\ ms (provisional).
.bp
.sp 2P
.LP
\fBRecommendation\ I.141\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBISDN NETWORK CHARGING CAPABILITIES ATTRIBUTES\fR
.EF '% Fascicle\ III.7\ \(em\ Rec.\ I.141''
.OF '''Fascicle\ III.7\ \(em\ Rec.\ I.141 %'
.ce 0
.sp 1P
.ce 1000
\fI(Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBPreamble\fR
.sp 1P
.RT
.PP
On the basis of charging principles provided in the D.200\(hySeries, this
Recommendation covers the method for identifying the network charging
capabilities and provides a candidate list of attributes in Annex\ A.
.RT
.sp 2P
.LP
\fB2\fR \fBGeneral\fR
.sp 1P
.RT
.PP
ISDNs shall support a range of services as defined in the
I.200\(hySeries of Recommendations. Charging capabilities and mechanisms
need to be associated with each service.
.PP
To ensure that service charging requirements may be supported by
network charging facilities, it is essential that the service requirements
be specified in a format which simplifies the identification of network
requirements. The attribute technique is considered an appropriate mechanism
by which service requirements may be related to network requirements and
has thus been utilized in this Recommendation. (See Figure\ 1/I.141.)
.RT
.LP
.rs
.sp 7P
.ad r
\fBFigure 1/I.141, p. \fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB3\fR \fBISDN services characteristics\fR
.sp 1P
.RT
.PP
Specifically, the services to which network charging capabilities attributes
should be applied are as given in Table\ 1/I.141.
.RT
.LP
.sp 2
.ce
\fBH.T. [T1.141]\fR
.ce
TABLE\ 1/I.141
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(90p) | cw(78p) .
Service Recommendations
_
.T&
lw(90p) | cw(78p) .
Bearer services I.230\(hySeries
.T&
lw(90p) | cw(78p) .
Teleservices I.240\(hySeries
.T&
lw(90p) | cw(78p) .
Supplementary services I.250\(hySeries
_
.TE
.nr PS 9
.RT
.ad r
\fBTable 1/I.141 [T1.141], p. \fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fB4\fR \fBRole and application of the attribute technique\fR
.sp 1P
.RT
.PP
For each service defined in the I.200\(hySeries Recommendations, one set
of attribute values should be selected for each network charging capability
attribute. Assignment of attribute values for a specific service will allow
the determination of the network requirements relating to this service.
.PP
The definition of charging requirements in terms of network charging capability
attributes is intended to provide a link between the service
charging characteristics and the respective network charging mechanisms.
.PP
Network charging capability attributes are also intended to indicate the
range of information to be transferred either within the signalling network
or by some other means.
.PP
Annex\ A lists the candidate network charging capability attributes and
the possible values so far identified.
\v'1P'
.RT
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation I.141)
.sp 9p
.RT
.ce 0
.ce 1000
\fBCandidate network charging capability attributes\fR
.sp 1P
.RT
.ce 0
.LP
.sp 1
.ce
\fBH.T. [T2.141]\fR
.ce
TABLE\ A\(hy1/I.141
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(78p) | cw(90p) .
Attribute Possible values
_
.T&
lw(168p) .
Charging capabilities
_
.T&
lw(78p) | lw(90p) .
Usage | ua\d\u)\d {
Service requested
Call attempt | ub\d\u)\d
Call set\(hyup
Duration
Volume
Basis of provision
}
_
.T&
lw(78p) | lw(90p) .
Modulation Distance Time of usage
_
.T&
lw(168p) .
Billing capabilities
_
.T&
lw(78p) | lw(90p) .
Billing identification {
Calling party (sent paid)
Called party (reverse/collect)
Transferred (third party)
}
_
.T&
lw(78p) | lw(90p) .
Collection {
Subscriber billing
Credit card
Coin box
Debit card
}
_
.T&
lw(78p) | lw(90p) .
Mode {
On line
Off line
}
.TE
.LP
\ua\d\u)\d
The identification and definition of values for supplementary
services (e.g. registration, activation)
is for further study.
.LP
\ub\d\u)\d
For further study.
.nr PS 9
.RT
.ad r
\fBTableau A\(hy1/I.141 [T2.141], p. 13\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
\fBMONTAGE : PAGE 100 = PAGE BLANCHE\fR
.sp 1P
.RT
.LP
.bp