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InfoMagic Standards 1994 January
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1988
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.rs
.\" Troff code generated by TPS Convert from ITU Original Files
.\" Not Copyright ( c) 1991
.\"
.\" Assumes tbl, eqn, MS macros, and lots of luck.
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.EN
.nr LL 40.5P
.nr ll 40.5P
.nr HM 3P
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.nr PD 9p
.po 4P
.rs
\v | 5i'
.sp 1P
.ce 1000
\v'12P'
\s12PART\ IV
\v'4P'
.RT
.ce 0
.sp 1P
.ce 1000
\fBI.400\(hySeries Recommendations\fR \v'2P'
.ce 0
.sp 1P
.ce 1000
\fBISDN\ USER\(hyNETWORK\ INTERFACES\fR
.ce 0
.sp 1P
.LP
.rs
.sp 28P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.LP
\fBMONTAGE:\ \fR PAGE 154 = PAGE BLANCHE
.sp 1P
.RT
.LP
.EF '% Fascicule\ III.8\ \(em\ Rec.\ I.410''
.OF '''Fascicule\ III.8\ \(em\ Rec.\ I.410 %'
.LP
.bp
.sp 1P
.ce 1000
\v'3P'
SECTION\ 1
.ce 0
.sp 1P
.ce 1000
\fBISDN\ USER\(hyNETWORK\ INTERFACES\fR
.ce 0
.sp 1P
.sp 2P
.LP
\fBRecommendation\ I.410\fR
.RT
.sp 2P
.ce 1000
\fBGENERAL\ ASPECTS\ AND\ PRINCIPLES\ RELATING\ TO\fR
.EF '% Fascicle\ III.8\ \(em\ Rec.\ I.410''
.OF '''Fascicle\ III.8\ \(em\ Rec.\ I.410 %'
.ce 0
.sp 1P
.ce 1000
\fBRECOMMENDATIONS\ ON\ \fR \fBISDN\ USER\(hyNETWORK\ INTERFACES\fR
.ce 0
.sp 1P
.ce 1000
\fI(Malaga\(hyTorremolinos, 1984)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral\fR
.sp 1P
.RT
.PP
1.1
Recommendation I.120 gives the conceptual principles on which an ISDN should
be based. The main feature of an ISDN is the support of a wide range of
service capabilities, including voice and nonvoice applications, in
the same network by offering end\(hyto\(hyend digital connectivity.
.sp 9p
.RT
.PP
1.2
A key element of service integration for an ISDN is the provision of a
limited set of standard multipurpose user\(hynetwork interfaces. These
interfaces represent a focal point both for the development of ISDN network
components and configurations and for the development of ISDN terminal
equipment and applications.
.PP
1.3
An ISDN is recognized by the service characteristics available
through user\(hynetwork interfaces, rather than by its internal architecture,
configuration or technology. This concert plays a key role in permitting
user and network technologies and configurations to evolve separately.
.sp 2P
.LP
\fB2\fR \fBInterface applications\fR
.sp 1P
.RT
.PP
Figure 1/I.410 shows some examples of ISDN user\(hynetwork interfaces.
The following cases are identified, corresponding to:
.RT
.LP
1)
access of a single ISDN terminal;
.LP
2)
access of a multiple ISDN terminal installation;
.LP
3)
access of multiservice PBXs, or local area networks, or,
more generally, of private networks;
.LP
4)
access of specialized storage and information processing
centres.
.PP
In addition, depending on the particular national regulatory
arrangements, either ISDN user\(hynetwork interfaces or internetwork interfaces
may be used for access of:
.LP
5)
dedicated service networks;
.LP
6)
other multiple services networks, including
ISDNs.
.bp
.sp 2P
.LP
\fB3\fR \fBInterface Recommendation objectives\fR
.sp 1P
.RT
.PP
User\(hynetwork interface Recommendations should allow:
.RT
.LP
1)
different types of terminals and applications to use the
same interface;
.LP
2)
portability of terminals from one location to another
(office, home, public access points) within one country and from one
country to another country;
.LP
3)
separate evolution of both terminal and network equipment, technologies
and configurations;
.LP
4)
efficient connection with specialized storage and
information processing centres and other networks.
.LP
.rs
.sp 26P
.ad r
\fBFigure 1/I.410, p. \fR
.sp 1P
.RT
.ad b
.RT
.PP
User\(hynetwork interfaces should be designed to provide an
appropriate balance between service capabilities and cost/tariffs, in order
to meet service demand easily.
.sp 2P
.LP
\fB4\fR \fBInterface characteristics\fR
.sp 1P
.RT
.PP
User\(hynetwork interfaces are specified by a comprehensive set of
characteristics, including:
.RT
.LP
1)
physical and electromagnetic (including optical)
characteristics;
.LP
2)
channel structures and access capabilities;
.LP
3)
user\(hynetwork protocols;
.LP
4)
maintenance and operation characteristics;
.LP
5)
performance characteristics;
.LP
6)
service characteristics.
.PP
A layered approach has been adopted for the definition of ISDN
user\(hynetwork interfaces according to the ISDN protocol reference model,
Recommendation\ I.320.
.bp
.sp 2P
.LP
\fB5\fR \fBInterface capabilities\fR
.sp 1P
.RT
.PP
In addition to the multiservice capability, an ISDN user\(hynetwork
interface may allow for capabilities such as the following:
.RT
.LP
1)
multidrop and other multiple terminal arrangements;
.LP
2)
choice of information bit rate, switching mode, coding
method,\ etc., on a call\(hyby\(hycall or other (e.g.\ semi\(hypermanent or
subscription time option) basis, over the same interface
according to the user's need;
.LP
3)
capability for compatibility checking in order to check
whether calling and called terminals can communicate with each other.
.sp 2P
.LP
\fB6\fR \fBOther I\(hySeries Recommendations\fR
.sp 1P
.RT
.PP
6.1
The reference configurations for ISDN user\(hynetwork interfaces define
the terminology for various reference points and the types of functions
that can be provided between reference points. Recommendation\ I.411 contains
the reference configurations and shows significant applications.
.sp 9p
.RT
.PP
6.2
The number of different interfaces is kept to a minimum.
Recommendation\ I.412 defines a limited set of interface structures, and
possible access capabilities for the ISDN user\(hynetwork interfaces. A
distinction is necessary between the interface structure and the access
capability supported by the particular network access arrangement.
.PP
6.3
The user\(hynetwork interfaces, as defined in Recommendations\ I.420 and\
I.421, are applicable to a wide range of situations without modification
(e.g.\ to both reference points\ S and\ T, as defined in
Recommendation\ I.411).
\v'1P'
.sp 2P
.LP
\fBRecommendation\ I.411\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBISDN\ USER\(hyNETWORK\ INTERFACES\ \(em\ REFERENCE CONFIGURATIONS\fR
.EF '% Fascicle\ III.8\ \(em\ Rec.\ I.411''
.OF '''Fascicle\ III.8\ \(em\ Rec.\ I.411 %'
.ce 0
.sp 1P
.ce 1000
\fI(Malaga\(hyTorremolinos, 1984)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral\fR
.sp 1P
.RT
.PP
1.1
This Recommendation provides the reference configurations for ISDN user\(hynetwork
interfaces.
.sp 9p
.RT
.PP
1.2
From the user's perspective, an ISDN is completely described by
the attributes that can be observed at an ISDN user\(hynetwork interface,
including physical, electromagnetic, protocol, service, capability,
maintenance, operation and performance characteristics. The key to defining,
and even recognizing, an ISDN is the specification of these characteristics.
.PP
1.3
An objective of ISDN is that a small set of compatible user\(hynetwork
interfaces can economically support a wide range of user applications,
equipment and configurations. The number of different user\(hynetwork interfaces
is minimized to maximize user flexibility through terminal compatibility
(from one application to another, one location to another, and one service
to
another) and to reduce costs through economies in production of equipment
and operation of both ISDN and user equipment. However, different interfaces
are
required for applications with widely different information rates, complexity,
or other characteristics, as well as for applications in the evolutionary
stages. In this way, simple applications need not to be burdened with the
cost of accommodating features employed by complex applications.
.PP
1.4
Another objective is to have the same interfaces used even though there
are different configurations (e.g.\ single terminal versus multiple
terminal connections, connections to a PABX versus direct connections into
the network,\ etc.) or different national regulations.
.bp
.sp 2P
.LP
\fB2\fR \fBDefinitions\fR
.sp 1P
.RT
.PP
2.1
\fBReference configurations\fR are conceptual configurations
useful in identifying various possible physical user access arrangements
to an ISDN. Two concepts are used in defining reference configurations:
reference
points and functional groupings. Layout and application examples of reference
configurations are given in \(sc\ 3.
.sp 9p
.RT
.PP
2.2
\fBFunctional groups\fR are sets of functions which may be needed in ISDN
user access arrangements. In a particular access arrangement, specific
functions in a functional group may or may not be present. Note that specific
functions in a functional group may be performed in one or more pieces
of
equipment.
.PP
2.3
\fBReference points\fR are the conceptual points dividing
functional groups. In a specific access arrangement, a reference point may
correspond to a physical interface between pieces of equipment, or there may
not be any physical interface corresponding to the reference point. Physical
interfaces that do not correspond to a reference point (e.g.\ transmission
line interfaces) will not be the subject of ISDN user\(hynetwork interface
Recommendations.
.sp 2P
.LP
\fB3\fR \fB
\fBReference configuration\fR
.sp 1P
.RT
.PP
3.1
The reference configurations for ISDN user\(hynetwork interfaces define
reference points and types of functions that can be provided between
reference points. Figure\ 1/I.411 shows the reference configurations, while
Figures\ 2/I.411, 3/I.411 and\ 4/I.411 show examples of applications of such
configurations.
.sp 9p
.RT
.PP
3.2
The ISDN user\(hynetwork interface Recommendations in the I\(hySeries
apply to physical interfaces at reference points\ S and\ T, using the recommended
interface structures according to Recommendation\ I.412. At reference point\
R, physical interfaces in accordance with other Recommendations (e.g.\
the
X\(hySeries interface Recommendations) may be used.
.PP
\fINote\ 1\fR \ \(em\ Physical interfaces not included in CCITT
Recommendations may appear at reference point\ R.
.PP
\fINote 2\fR \ \(em\ There is no reference point assigned to the transmission
line, since an ISDN user\(hynetwork interface is not envisaged at this
location.
.RT
.PP
3.3
Figure 1a/I.411 defines the reference configuration with the
functional groups NT1, NT2 and\ TE1. Figure\ 1b/I.411 illustrates that
TE1 may be replaced by the combination of TE2 and TA.
.LP
.rs
.sp 22P
.ad r
\fBFigure 1/I.411, p. \fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
3.4
Lists of functions for each functional group are given below.
Each particular function is not necessarily restricted to a single functional
group. For example, \*Qinterface termination\*U functions are included
in the
function lists of NT1, NT2 and TE. The function lists for NT2, TE and TA are
not exhaustive. For a particular access arrangement, specific functions in a
functional group are either present or absent.
.PP
The functional groups are described in relation to the ISDN
protocol reference model in Recommendation\ I.320.
.sp 1P
.LP
3.4.1
\fINetwork termination 1 (NT1)\fR
.sp 9p
.RT
.PP
This functional group includes functions broadly equivalent to
layer\ 1 (physical) of the OSI reference model. These functions are associated
with the proper physical and electromagnetic termination of the network.
NT1
functions are:
.RT
.LP
\(em
line transmission termination;
.LP
\(em
layer 1 line maintenance functions and performance
monitoring;
.LP
\(em
timing;
.LP
\(em
power transfer;
.LP
\(em
layer 1 multiplexing;
.LP
\(em
interface termination, including multidrop termination
employing layer\ 1 contention resolution.
.sp 1P
.LP
3.4.2
\fINetwork termination 2 (NT2)\fR
.sp 9p
.RT
.PP
This functional group includes functions broadly equivalent to
layer\ 1 and higher layers of the Recommendation\ X.200 reference model.
PABXs, local area networks, and terminal controllers are examples of equipment
or
combinations of equipment that provide NT2 functions. NT2 functions
include:
.RT
.LP
\(em
layers 2 and 3 protocol handling;
.LP
\(em
layers 2 and 3 multiplexing;
.LP
\(em
switching;
.LP
\(em
concentration;
.LP
\(em
maintenance functions; and
.LP
\(em
interface termination and other layer 1 functions.
.PP
For example, a simple PABX can provide NT2 functions at layers 1, 2 and\
3. A simple terminal controller can provide NT2 functions at only
layers\ 1 and\ 2. A simple time division multiplexer can provide NT2 functions
at only layer\ 1. In a specific access arrangement, the NT2 functional
group may
consist of only physical connections.
.sp 1P
.LP
3.4.3
\fITerminal equipment (TE)\fR
.sp 9p
.RT
.PP
This functional group includes functions broadly belonging to
layer\ 1 and higher layers of the Recommendation\ X.200 reference model.
Digital telephones, data terminal equipment, and integrated work stations
are examples of equipment or combinations of equipment that provide the
functions. The TE
functions are:
.RT
.LP
\(em
protocol handling;
.LP
\(em
maintenance functions;
.LP
\(em
interface functions;
.LP
\(em
connection functions to other equipments.
.sp 1P
.LP
3.4.3.1
\fITerminal equipment type 1 (TE1)\fR
.sp 9p
.RT
.PP
This functional group includes functions belonging to the
functional group TE, and with an interface that complies with the ISDN
user\(hynetwork interface Recommendations.
.RT
.sp 1P
.LP
3.4.3.2
\fITerminal equipment type 2 (TE2)\fR
.sp 9p
.RT
.PP
This functional group includes functions belonging to the
functional group TE but with an interface that complies with interface
Recommendations other than the ISDN interface Recommendation (e.g.\ the
X\(hySeries interface Recommendations) or interfaces not included in CCITT
Recommendations.
.bp
.RT
.sp 1P
.LP
3.4.4
\fITerminal adaptor (TA)\fR
.sp 9p
.RT
.PP
This functional group includes functions broadly belonging to
layer\ 1 and higher layers of the Recommendation\ X.200 reference model that
allow a TE2 terminal to be served by an ISDN user\(hynetwork interface.
Adaptors between physical interfaces at reference points\ R and\ S or\
R and\ T are examples of equipment or combinations of equipment that provide
TA functions.
.RT
.sp 2P
.LP
\fB4\fR \fBPhysical realizations of reference configurations\fR
.sp 1P
.RT
.PP
4.1
Figure 2/I.411 gives examples of configurations illustrating
combinations of physical interfaces\ at
reference points\ R, S and\ T;
Figures\ 2a/I.411 and\ 2b/I.411 show separate interfaces at\ S and\ T;
Figures\ 2c/I.411
and\ 2d/I.411 show an interface at\ S but not\ T;
Figures\ 2e/I.411 and 2f/I.411 show an interface at\ T\ but
not\ S;
Figures\ 2g/I.411 and\ 2h/I.411 show an interface at\ S and\ T where they
coincide. Additionally,
Figures\ 2b/I.411, 2d/I.411, 2f/I.411 and 2h/I.411
show an interface at reference point\ R.
.sp 9p
.RT
.PP
4.2
Figures 3/I.411 and 4/I.411 show examples of physical
implementations. The examples given in Figure\ 3/I.411 show physical
realizations of functional groups TE, NT1 and NT2, based on physical interfaces
occurring at reference points\ R, S and\ T. The examples given in Figure\
4/I.411 show applications of the reference configurations to physical configurations
when multiple physical interfaces occur at a reference point.
.PP
The examples given in Figure 4/I.411 are not intended to be either exhaustive
or mandatory. Square blocks in Figures\ 3/I.411 and\ 4/I.411 represent
equipment implementing functional groupings.
.PP
\fINote\fR \ \(em\ TE1 or TE2 + TA may be used interchangeably in
Figure\ 4/I.411.
.RT
.PP
4.2.1
Figures 4a/I.411 and 4b/I.411 show applications of the
reference
configurations in the cases where NT2 functions consist of only physical
connections. Figure 4a/I.411 describes the direct physical connection of
multiple TEs (TE1s or TE2s\ +\ TAs) to NT1 using a multidrop arrangement
(i.e.\ a bus). Figure\ 4b/I.411 illustrates the separate connection of
a number of TEs to NT1.
.PP
In these cases, all of the characteristics of the physical
interfaces applied at reference points\ S and\ T must be identical.
.PP
4.2.2
Figure 4c/I.411 shows the provision of multiple connections
between NT2 and TEs. NT2 may include various types of distribution
arrangements, such as star, bus or ring configuration included within the
equipment. Figure\ 4d/I.411 shows a case where a bus distribution is used
between TEs and the NT2 equipment.
.PP
4.2.3
Figures 4e/I.411 and 4f/I.411 show arrangements where multiple
connections are used between\ NT2
and\ NT1 equipment. In particular,
Figure\ 4e/I.411 illustrates the case of multiple NT1 equipment,
while
Figure\ 4f/I.411 refers to the case where NT1 provides layer\ 1
upward multiplexing of the multiple connections.
.PP
4.2.4
Figure 4g/I.411 illustrates the case where NT1 and NT2
functions
are merged in the same equipment; the corresponding merging of NT1 and NT2
functions for other configurations in Figure\ 4/I.411 may also occur.
.PP
4.2.5
Figure 4h/I.411 illustrates the case where TA and NT2 functions
are merged in the same equipment; the corresponding merging of TA and NT2
functions for other configurations in Figure\ 4/I.411 may also occur.
.PP
4.2.6
In addition to the examples of physical implementation shown in
Figures\ 3/I.411 and\ 4/I.411, a possible combination of NT1, NT2 and TA
into one physical entity could be considered, in which both reference points\
S and\ T
exist but are not realized as physical interfaces. Such an implementation
is to be considered an interim means of providing connection to an ISDN
and might be used to complement the recommended means of connecting terminals
via physical interfaces at reference points\ S and\ T in the early stages
of ISDN
implementation. This should not be considered as a reference configuration
because it poses significant problems in relation to the models of ISDN
presently being studied.
.PP
4.2.7
These physical implementations are limited in their arrangements
and combinations by the electrical and other characteristics of the interface
specifications and equipment.
.PP
4.3
The reference\(hyconfigurations given in Figure\ 1/I.411 apply for
the specification of the interface structures and access arrangements given
in Recommendation\ I.412.
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 2/I.411, p. 3\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 47P
.ad r
\fBFigure 3/I.411, p. 4\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 31P
.ad r
\fBFigure 4/I.411, p. 5\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fBRecommendation I.412\fR
.RT
.sp 2P
.ce 1000
\fBISDN\ USER\(hyNETWORK\ INTERFACES\fR
.EF '% Fascicle\ III.8\ \(em\ Rec.\ I.412''
.OF '''Fascicle\ III.8\ \(em\ Rec.\ I.412 %'
.ce 0
.sp 1P
.ce 1000
\fBINTERFACE\ STRUCTURES\ AND\ ACCESS\ CAPABILITIES\fR
.ce 0
.sp 1P
.ce 1000
\fI(Malaga\(hyTorremolinos, 1984; amended at Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral\fR
.sp 1P
.RT
.PP
This Recommendation defines limited sets of both channel types and interface
structures for ISDN user\(hynetwork physical interfaces.
.RT
.sp 2P
.LP
\fB2\fR \fBDefinitions\fR
.sp 1P
.RT
.PP
2.1
A channel represents a specified portion of the
information\(hycarrying capacity of an interface.
.sp 9p
.RT
.PP
2.2
Channels are classified by channel types, which have common
characteristics. Channel types are specified in \(sc\ 3.
.bp
.PP
2.3
The channels are combined into interface structures, specified in \(sc\
4. An interface structure defines the maximum digital information\(hycarrying
capacity across a physical interface.
.PP
2.4
In an actual access arrangement some of the channels available
across an ISDN user\(hynetworks physical interface, as defined in the applicable
interface structure, may not be supported by the network. Some ISDN services
will not require the full capacity of a B\(hychannel; in those cases in which
users require only such services, the access capability might be further
reduced. The capability provided by those channels that are actually available
for communication purposes, is referred to as the access capability provided
through the interface.
.sp 2P
.LP
\fB3\fR \fBChannel types and their use\fR
.sp 1P
.RT
.sp 1P
.LP
3.1
\fIB\(hychannel\fR
.sp 9p
.RT
.PP
3.1.1
The B\(hychannel is a 64 kbit/s channel accompanied by timing.
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ The method for providing this timing is a subject of
the individual interface Recommendations.
.PP
A B\(hychannel is intended to carry a wide variety of user
information streams. A distinguishing characteristic is that a B\(hychannel
does not carry signalling information for circuit switching by the ISDN.
Signalling information used for circuit switching by the ISDN is carried
over other types of channels, e.g.\ a D\(hychannel.
.RT
.PP
3.1.2
User information streams may be carried on a B\(hychannel on a
dedicated, alternate (within one call or as separate calls), or simultaneous
basis, consistent with the B\(hychannel bit rate. The following are samples of
user information streams:
.LP
i)
voice encoded at 64 kbit/s according to Recommendation
G.711;
.LP
ii)
data information corresponding to circuit or
packet\(hyswitching user classes of service at bit rates less than
or equal to 64\ kbit/s, according to Recommendation\ X.1;
.LP
iii)
wideband voice encoded at 64 kbit/s according to
Recommendation\ G.722;
.LP
iv)
voice encoded at bit rates lower than 64 kbit/s alone, or combined with
other digital information streams.
.PP
It is recognized that a B\(hychannel may also be used to carry user information
streams not covered by CCITT Recommendations.
.PP
3.1.3
B\(hychannels may be used to provide access to a variety of
communication modes within the ISDN. Examples of these modes are:
.LP
i)
circuit switching;
.LP
ii)
packet switching, supporting packet mode terminals; and
.LP
iii)
semi\(hypermanent connections.
.PP
In case i), the ISDN can provide either a transparent end\(hyto\(hyend
64\ kbit/s connection or a connection specifically suited to a particular
service, such as telephony, in which case a transparent 64\ kbit/s connection
may not be provided.
.PP
In case ii), the B\(hychannel will carry protocols at layers\ 2 and\ 3
according to Recommendation\ X.25 which have to be handled by the network.
The application of D\(hychannel protocols for this case is for further
study.
.PP
In case iii), the semi\(hypermanent connection can be provided, for
example by using circuit or packet switching modes.
.RT
.PP
3.1.4
Single information streams at bit rates less than 64 kbit/s
should be rate adapted to be carried on the B\(hychannel as described in
Recommendation\ I.460.
.PP
3.1.5
Multiple information streams from a given user may be
multiplexed together in the same B\(hychannel, but for circuit switching, an
entire B\(hychannel will be switched to a single user\(hynetwork interface.
This
multiplexing should be in accordance with Recommendation\ I.460.
.PP
\fINote\fR \ \(em\ Independent routing of subrate channels circuit switched
to different destinations is for further study.
.bp
.sp 2P
.LP
3.2
\fID\(hychannel\fR
.sp 1P
.RT
.PP
3.2.1
The D\(hychannel may have different bit rates as specified in \(sc 4.
.sp 9p
.RT
.PP
A
D\(hychannel
is primarily intended to carry signalling
information for circuit switching by the ISDN.
.PP
A D\(hychannel uses a layered protocol according to
Recommendations\ I.440, I.441, I.450 and I.451. In particular the link access
procedure is frame oriented (Note).
.PP
\fINote\fR \ \(em\ The use of Signalling System No.\ 7 at a user\(hynetwork
interface is for further study.
.RT
.PP
3.2.2
In addition to signalling information for circuit switching, a
D\(hychannel may also be used to carry teleaction information and packet\(hyswitched
data.
.PP
In certain cases where such signalling is not being utilized, the D\(hychannel
may support only teleaction information or packet\(hyswitched data.
.sp 2P
.LP
3.3
\fIH\(hychannels\fR
.sp 1P
.RT
.PP
3.3.1
H\(hychannels have the following bit rates, accompanied by
timing:
.sp 9p
.RT
.LP
H\d0\uchannel
: 384 kbit/s
.LP
H\d1\uchannels
: 1536 (H\d1\\d1\u) and 1920 (H\d1\\d2\u)
kbit/s.
.PP
\fINote\fR \ \(em\ The method for providing this timing is a subject of
the individual interface Recommendation.
.PP
Higher rate H\(hychannels are for further study.
.PP
An
H\(hychannel
is intended to carry a variety of user
information streams. A distinguishing characteristic is that an H\(hychannel
does not carry signalling information for circuit switching by the ISDN.
.RT
.PP
3.3.2
User information streams may be carried on an H\(hychannel on a
dedicated, alternate (within one call or as separate calls), or simultaneous
basis, consistent with the H\(hychannel bit rates. The following are examples
of user information streams:
.LP
i)
fast facsimile;
.LP
ii)
video: e.g.\ for teleconferencing;
.LP
iii)
high speed data;
.LP
iv)
high quality audio or sound programme material;
.LP
v)
information streams, each at rates lower than the respective H\(hychannel
bit rate (e.g.\ voice at 64\ kbit/s), which have been rate adapted or multiplexed
together;
.LP
vi)
packet\(hyswitched information.
.sp 1P
.LP
3.4
\fIOther channels\fR
.sp 9p
.RT
.PP
For further study.
.RT
.sp 2P
.LP
\fB4\fR \fBInterface structures\fR
.sp 1P
.RT
.PP
ISDN user\(hynetwork physical interfaces at ISDN reference points S
and\ T shall comply with one of the interface structures defined below.
.RT
.sp 2P
.LP
4.1
\fIB\(hychannel interface structures\fR
.sp 1P
.RT
.sp 1P
.LP
4.1.1
\fIBasic interface structure\fR
.sp 9p
.RT
.PP
4.1.1.1
The basic interface structure is composed of two B\(hychannels and one
D\(hychannel, 2 B\ +\ D. The bit rate of the D\(hychannel in this interface
structure is 16\ kbit/s.
.sp 9p
.RT
.PP
4.1.1.2
The B\(hychannels may be used independently; i.e. in different
connections at the same time.
.bp
.PP
4.1.1.3
With the basic interface structure, two B\(hychannels and one
D\(hychannel are always present at the ISDN user\(hynetwork physical interface.
One or both B\(hychannels, however, may not be supported by the network.
See
Appendix\ I.
.sp 1P
.LP
4.1.2
\fIPrimary rate B\(hychannel interface structures\fR
.sp 9p
.RT
.PP
These structures correspond to the primary rates of 1544 kbit/s and 2048\
kbit/s.
.RT
.PP
4.1.2.1
The primary rate B\(hychannel interface structures are composed of
B\(hychannels and one D\(hychannel. The bit rate of this D\(hychannel is
64\ kbit/s.
.PP
4.1.2.2
At the 1544 kbit/s primary rate the interface structure is 23
B\ +\ D.
.PP
4.1.2.3
At the 2048 kbit/s primary rate the interface structure is 30
B\ +\ D.
.PP
4.1.2.4
With the primary rate B\(hychannel interface structures, the
designated number of B\(hychannels is always present at the ISDN user\(hynetwork
physical interface. One or more of the B\(hychannels may not be supported
by the network.
.PP
4.1.2.5
In the case of a user\(hynetwork access arrangement containing
multiple interfaces, it is possible for the D\(hychannel in one structure
to carry the signalling for B\(hychannels in another primary rate structure
without an
activated D\(hychannel. When a D\(hychannel is not activated, the designated
time
slot may or may not be used to provide an additional B\(hychannel, depending on
the situation; e.g.,\ 24\ B for a 1544\ kbit/s interface.
.sp 2P
.LP
4.2
\fIH\(hychannel interface structure\fR
.sp 1P
.RT
.sp 1P
.LP
4.2.1
\fIPrimary rate interface H\fR\d\fI0\fR\u\fI\(hychannel structures\fR
.sp 9p
.RT
.PP
4.2.1.1
The primary rate interface H\d0\u\(hychannel structures are composed of
H\d0\u\(hychannels with or without a D\(hychannel, as indicated below.
When present in the same interface structure the bit rate of the D\(hychannel
is 64\ kbit/s.
Additional primary rate interface H\d0\u\(hychannel structures are for further
study.
.sp 9p
.RT
.PP
4.2.1.2
At the 1544 kbit/s primary rate interface the H\d0\u\(hychannel
structures are 4\ H\d0\uand 3\ H\d0\u\ +\ D. The use of the additional
capacity across the interface is for further study. When the D\(hychannel
is not provided, signalling for the H\d0\u\(hychannels is provided by the
D\(hychannel in
another interface.
.PP
4.2.1.3
At the 2048 kbit/s primary rate interface the H\d0\u\(hychannel
structure is 5\ H\d0\u\ +\ D. In the case of a user\(hynetwork access
arrangement containing multiple interfaces, it is possible for the D\(hychannel
in one structure to carry the signalling for H\d0\u\(hychannels in another
primary
rate interface without a D\(hychannel in use.
.PP
4.2.1.4
With the primary rate interface H\d0\u\(hychannel structures, the
designated number of H\d0\u\(hychannels is always present at the user\(hynetwork
physical interface. One or more of the H\d0\u\(hychannels may not be supported
by the network.
.PP
4.2.1.5
In the case of a user\(hynetwork access arrangement containing
multiple interfaces it is possible for the D\(hychannel of one structure
to carry the signalling for H\d0\u\(hychannels in another primary rate
interface structure without an activated D\(hychannel. When a D\(hychannel
is not required in a
1544\ kbit/s interface, the 4\ H\d0\u\(hychannel structure may be used.
.sp 2P
.LP
4.2.2.
\fIPrimary rate interface H\fR\d1\u\fI\(hychannel structures\fR
.sp 1P
.RT
.sp 1P
.LP
4.2.2.1
\fI1536 kbit/s H\fR\d1\\d1\u\fI\(hychannel Structure\fR
.sp 9p
.RT
.PP
The 1536 kbit/s H\d1\\d1\u\(hychannel structure is composed of one
1536\ kbit/s H\d1\\d1\u\(hychannel. Signalling for the H\d1\\d1\u\(hychannel,
if
required, is carried in a D\(hychannel on another interface structure within
the same user\(hynetwork access arrangement.
.RT
.sp 1P
.LP
4.2.2.2
\fI1920 kbit/s H\fR\d1\\d2\u\fI\(hychannel Structure\fR
.sp 9p
.RT
.PP
The 1920 kbit/s H\d1\\d2\u\(hychannel structure is composed of one
1920 kbit/s H\d1\\d2\u\(hychannel and a D\(hychannel. The bit rate of the
D\(hychannel is 64\ kbit/s. Signalling for the H\d1\\d2\u\(hychannel, if
required, is carried in
this D\(hychannel or the D\(hychannel of another interface structure within
the same user\(hynetwork access arrangement.
.bp
.RT
.sp 1P
.LP
4.3
\fIPrimary rate interface structures for mixtures\fR
\fIof B\(hy and H\fR\d\fI0\fR\uannels\fR
.sp 9p
.RT
.PP
A primary rate interface may have a structure consisting of a
single D\(hychannel and any mixture of B\(hy and H\d0\u\(hychannels. The
bit rate of the D\(hychannel is 64\ kbit/s. In the case of a user\(hynetwork
access arrangement
containing multiple interfaces, a D\(hychannel in one interface structure
may also carry signalling for channels in another interface structure.
When a D\(hychannel is not activated, its 64\ kbit/s capacity may or may
not be used for the mixture of B\(hy\ and H\d0\u\(hychannels, depending
on the situation, e.g.\ 3 H\d0\u\ +\ 6 B for a 1544\ kbit/s interface.
.RT
.sp 1P
.LP
4.4
\fIOther interface structure(s)\fR
.sp 9p
.RT
.PP
For further study.
.RT
.sp 2P
.LP
\fB5\fR \fBExamples of\fR
\fBapplication of interface structures\fR
.sp 1P
.RT
.sp 1P
.LP
5.1
\fIAccess arrangement for PABX, terminal controller, local area\fR
\fInetwork, etc.\fR
.sp 9p
.RT
.PP
Figure 1/I.412 illustrates a typical PABX, or LAN access
arrangement. For this particular configuration it is not necessary to apply
the same interface structure at both S and T reference points. For example,
basic interface structures may be used for interfaces located at reference
point\ S. Either basic or primary rate or other interface structures may
be used at
interfaces located at reference point\ T.
.RT
.LP
.rs
.sp 18P
.ad r
\fBFigure 1/I.412, p. \fR
.sp 1P
.RT
.ad b
.RT
.ce 1000
APPENDIX I
.ce 0
.ce 1000
(to Recommendation I.412)
.sp 9p
.RT
.ce 0
.ce 1000
\fBAccess capabilities\fR
.sp 1P
.RT
.ce 0
.PP
I.1
As stated in\ \(sc\ 2.4, not all of the channels present in an
ISDN user\(hynetwork physical interface are necessarily supported by the
network. The resulting capability provided in an ISDN user\(hynetwork access
arrangement is defined as the access capability.
.sp 1P
.RT
.PP
To assist in guiding the implementations of ISDN equipment and
services around the world, several preferred access capabilities are identified
here. While these preferred arrangements do not preclude the implementation
of other access capabilities, they are intended to assist in the worldwide
commonality which is a key objective of ISDN.
.bp
.sp 1P
.LP
I.2
\fIPreferred access capabilities\fR
.sp 9p
.RT
.PP
a)
\fIPreferred basic access capabilities\fR
.RT
.LP
\(em
2 B + D
.LP
\(em
B + D
.LP
\(em
D
.LP
b)
\fIPrimary rate \(em B\(hychannel access capabilities\fR
.LP
\(em
\fIn\fR | B + D
.LP
\fIn\fR | \(= 23 for 1544 kbit/s primary rate, unless
signalling is provided in another physical interface (see \(sc\ 4.1.2.5); then
\fIn\fR \ =\ 24 may be allowed.
.LP
\fIn\fR \(= 30 for 2048 kbit/s primary rate, unless
signalling is provided in another physical interface (see \(sc\ 4.1.2.5) then
\fIn\fR \ =\ 31 may be allowed.
.LP
c)
\fIPrimary rate\ \(em\ H\fR\d0\u\fI\(hychannel access capabilities\fR
.LP
\(em
\fIn\fR | \d0\u+ D
.LP
\fIn\fR | \(= 3 for 1544 kbit/s primary rate
.LP
\fIn\fR | \(= 5 for 2048 kbit/s primary rate
.LP
\(em
\fIn\fR | \d0\u
.LP
\fIn\fR | \(= 4 for 1544 kbit/s primary rate
.LP
d)
\fIOther channel structure access capabilities\fR
.LP
For further study.
.LP
.rs
.sp 34P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 1P
.ce 1000
\v'3P'
SECTION\ 2
.ce 0
.sp 1P
.ce 1000
\fBAPPLICATION\ OF\ I\(hySERIES\ RECOMMENDATIONS\ TO\fR
.ce 0
.sp 1P
.ce 1000
\fBISDN\ USER\(hyNETWORK\ INTERFACES\fR \v'1P'
.ce 0
.sp 1P
.sp 2P
.LP
\fBRecommendation I.420\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBBASIC\ USER\(hyNETWORK\ INTERFACE\fR
.EF '% Fascicle\ III.8\ \(em\ Rec.\ I.420''
.OF '''Fascicle\ III.8\ \(em\ Rec.\ I.420 %'
.ce 0
.sp 1P
.ce 1000
\fI(Malaga\(hyTorremolinos, 1984)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.PP
The basic user\(hynetwork interface structure is defined in
Recommendation\ I.412. The detailed specifications are contained in
Recommendations\ I.430 (layer\ 1), I.440 and I.441 (layer\ 2), I.450, I.451 and
I.452 (layer\ 3).
\v'1P'
.sp 1P
.RT
.sp 2P
.LP
\fBRecommendation I.421\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBPRIMARY\ RATE\ USER\(hyNETWORK\ INTERFACE\fR
.EF '% Fascicle\ III.8\ \(em\ Rec.\ I.421''
.OF '''Fascicle\ III.8\ \(em\ Rec.\ I.421 %'
.ce 0
.sp 1P
.ce 1000
\fI(Malaga\(hyTorremolinos, 1984)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.PP
The primary rate user\(hynetwork interface structures are
defined in Recommendation\ I.412. The detailed specifications are contained
in Recommendations\ I.431 (layer\ 1), I.440 and I.441 (layer\ 2), I.450,
I.451 and
I.452 (layer\ 3).
.sp 1P
.RT
.LP
.rs
.sp 12P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.LP
\fBMONTAGE:\ \fR PAGE 170 = PAGE BLANCHE
.sp 1P
.RT
.LP
.bp
.sp 1P
.ce 1000
\v'3P'
SECTION\ 3
.ce 0
.sp 1P
.ce 1000
\fBISDN\ USER\(hyNETWORK\ INTERFACES:\ LAYER\ 1\ RECOMMENDATIONS\fR
.ce 0
.sp 1P
.sp 2P
.LP
\fBRecommendation\ I.430\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBBASIC USER\(hyNETWORK INTERFACE\ \(em\ LAYER 1 SPECIFICATION\fR
.EF '% Fascicle\ III.8\ \(em\ Rec.\ I.430''
.OF '''Fascicle\ III.8\ \(em\ Rec.\ I.430 %'
.ce 0
.sp 1P
.ce 1000
\fI(Malaga\(hyTorremolinos, 1984; amended at Melbourne, 1988)\fR
.sp 9p
.RT
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral\fR
.sp 1P
.RT
.PP
This Recommendation defines the
layer\ 1 characteristics of the user\(hynetwork interface
to be applied at the\ S or\ T reference points for the basic interface
structure defined in Recommendation\ I.412. The reference
configurations for the interface is defined in Recommendation\ I.411 and is
reproduced in Figure\ 1/I.430.
.RT
.LP
.rs
.sp 15P
.ad r
\fBFigure 1/I.430, p. \fR
.sp 1P
.RT
.ad b
.RT
.PP
In this Recommendation, the term \*QNT\*U is used to indicate network terminating
layer\ 1 aspects of NT1 and NT2 functional groups, and the term \*QTE\*U
is used to indicate terminal terminating layer\ 1 aspects of TE1, TA and
NT2
functional groups, unless otherwise indicated. However, in\ \(sc\ 6.2 only, the
terms \*QNT\*U and \*QTE\*U have the following meaning: the term \*QNT\*U
is used to
indicate the layer\ 1 network side of the basic access interface; the term
\*QTE\*U is used to indicate the layer\ 1 terminal side of the basic access
interface.
.PP
The terminology used in this Recommendation is very specific and not contained
in the relevant terminology Recommendations. Therefore Annex\ E to
this Recommendation provides terms and definitions used in this
Recommendation.
.bp
.RT
.sp 2P
.LP
\fB2\fR \fBService characteristics\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
\fIServices required from the physical medium\fR
.sp 9p
.RT
.PP
Layer 1 of this interface requires a balanced metallic transmission medium,
for each direction of transmission, capable of
supporting\ 192\ kbit/s.
.RT
.sp 1P
.LP
2.2
\fIService provided to layer 2\fR
.sp 9p
.RT
.PP
Layer 1 provides the following services to layer\ 2 and the
management entity:
.RT
.sp 1P
.LP
2.2.1
\fITransmission capability\fR
.sp 9p
.RT
.PP
Layer 1 provides the transmission capability, by means of
appropriately encoded bit streams, for the
B\(hy and D\(hychannels and the related timing and synchronization functions.
.RT
.sp 1P
.LP
2.2.2
\fIActivation/deactivation\fR
.sp 9p
.RT
.PP
Layer 1 provides the signalling capability and the necessary
procedures to enable customer TEs and/or NTs to be deactivated when required
and reactivated when required. The activation and deactivation procedures
are defined in\ \(sc\ 6.2.
.RT
.sp 1P
.LP
2.2.3
\fID\(hychannel access\fR
.sp 9p
.RT
.PP
Layer 1 provides the signalling capability and the necessary
procedures to allow TEs to gain access to the common resource of the D\(hychannel
in an orderly fashion while meeting the performance requirement of the
D\(hychannel signalling system
. These D\(hychannel access control procedures are defined in\ \(sc\ 6.1.
.RT
.sp 1P
.LP
2.2.4
\fIMaintenance\fR
.sp 9p
.RT
.PP
Layer 1 provides the signalling capability, procedures and
necessary functions at layer\ 1 to enable the maintenance functions to be
performed.
.RT
.sp 1P
.LP
2.2.5
\fIStatus indication\fR
.sp 9p
.RT
.PP
Layer 1 provides an indication to the higher layers of the status of layer\
1.
.RT
.sp 1P
.LP
2.3
\fIPrimitives between layer 1 and the other entities\fR
.sp 9p
.RT
.PP
Primitives represent, in an abstract way, the logical exchange of information
and control between layer\ 1 and other entities. They neither
specify nor constrain the implementation of entities or interfaces.
.PP
The primitives to be passed across the layer\ 1/2 boundary or to the
management entity
and parameter values associated with these primitives are defined and summarized
in Table\ 1/I.430. For description of the syntax and use of the primitives,
refer to Recommendation\ X.211 and relevant detailed
descriptions in\ \(sc\ 6.
.RT
.sp 2P
.LP
\fB3\fR \fBModes of operation\fR
.sp 1P
.RT
.PP
Both point\(hyto\(hypoint and point\(hyto\(hymultipoint modes of operation,
as described below, are intended to be accommodated by the layer\ 1 characteristics
of the user\(hynetwork interface. In this Recommendation, the modes of
operation apply only to the layer\ 1 procedural characteristics of the
interface and do
not imply any constraints on modes of operation at higher layers.
.RT
.sp 1P
.LP
3.1
\fIPoint\(hyto\(hypoint operation\fR
.sp 9p
.RT
.PP
Point\(hyto\(hypoint operation at layer\ 1 implies that only one
source
(transmitter) and one
sink
(receiver) are active at any one time in each direction of transmission
at an\ S or\ T reference point. (Such operation is independent of the number
of interfaces which may be provided on a particular wiring configuration\
\(em\ see\ \(sc\ 4).
.bp
.RT
.ce
\fBH.T. [T1.430]\fR
.ce
TABLE\ 1/I.430
.ce
\fBPrimitives associated with layer\ 1\fR
.T&
lw(228p) .
.T&
lw(228p) .
L1 | (<- \(ra | 2
_
.T&
lw(54p) | lw(30p) | lw(30p) | lw(30p) | lw(30p) | lw(54p) .
.T&
lw(228p) .
M | (<- \(ra | 1
_
.T&
lw(54p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | lw(54p) .
MPH\(hyERROR \(em X \(em X {
Type of error or recovery from a
previously reported error
}
_
.T&
lw(54p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | lw(54p) .
MPH\(hyACTIVATE \(em X \(em \(em
_
.T&
lw(54p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | lw(54p) .
MPH\(hyDEACTIVATE X X \(em \(em
_
.T&
lw(54p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | lw(54p) .
MPH\(hyINFORMATION \(em X \(em X Connected/disconnected
.TE
.LP
\fINote\ 1\fR
\ \(em\ PH\(hyDATA REQUEST implies underlying negotiation
between layer\ 1 and layer\ 2 for the acceptance of the data.
.LP
\fINote\ 2\fR
\ \(em\ Priority indication applies only to the request
type.
.nr PS 9
.RT
.ad r
\fBTableau 1/I.430 [T1.430], p. 8\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
.sp 5
3.2
\fIPoint\(hyto\(hymultipoint operation\fR
.sp 9p
.RT
.PP
Point\(hyto\(hymultipoint operation at layer\ 1 allows more than one TE
(source and sink pair) to be simultaneously active at an\ S or\ T reference
point. (The multipoint mode of operation may be accommodated, as discussed
in\ \(sc\ 4, with point\(hyto\(hypoint or point\(hyto\(hymultipoint wiring
configurations.)
.RT
.sp 2P
.LP
\fB4\fR \fBTypes of\fR
\fBwiring configuration\fR
.sp 1P
.RT
.PP
The electrical characteristics of the user\(hynetwork interface are
determined on the basis of certain assumptions about the various wiring
configurations which may exist in the user premises. These assumptions are
identified in two major configuration descriptions,\ \(sc\ 4.1 and\ \(sc\
4.2, together with additional material contained in Annex\ A. Figure\ 2/I.430
shows a general Reference Configuration for wiring in the user premises.
.RT
.sp 1P
.LP
4.1
\fIPoint\(hyto\(hypoint configuration\fR
.sp 9p
.RT
.PP
A
point\(hyto\(hypoint wiring configuration
implies that only one source (transmitter) and one sink (receiver) are
interconnected on an
interchange circuit.
.bp
.RT
.sp 1P
.LP
4.2
\fIPoint\(hyto\(hymultipoint configuration\fR
.sp 9p
.RT
.PP
A
point\(hyto\(hymultipoint wiring configuration
allows more than one source to be connected to the same sink or more than
one sink to be
connected to the same source on an interchange circuit. Such distribution
systems are characterized by the fact that they contain no active logic
elements performing functions (other than possibly amplification or
regeneration of the signal).
.RT
.sp 1P
.LP
4.3
\fIWiring polarity integrity\fR
.sp 9p
.RT
.PP
For a
point\(hyto\(hypoint wiring configuration
, the two wires of the interchange circuit pair may be reversed. However, for a
point\(hyto\(hymultipoint wiring configuration, the wiring polarity integrity
of the interchange circuit (TE\(hyto\(hyNT direction) must be maintained
between TEs (see
the reference configuration in Figure\ 20/I.430).
.PP
In addition, the wires of the optional pairs, which may be provided
for powering, may not be reversed in either configuration.
.RT
.sp 1P
.LP
4.4
\fILocation of the interfaces\fR
.sp 9p
.RT
.PP
The wiring in the user premises is considered to be one continuous cable
run with jacks for the TEs and NT attached directly to the cable or using
stubs less than\ 1\ metre in length. The jacks are located at interface
points\ I\dA\uand I\dB\u(see Figure\ 2/I.430). One interface point, I\dA\u, is
adjacent to each TE. The other interface point I\dB\u, is adjacent to the NT.
However, in some applications, the NT may be connected to the wiring without
the use of a jack or with a jack which accommodates multiple interfaces
(e.g.,\ when the NT is a port on a\ PBX). The required electrical characteristics
(described in\ \(sc\ 8) for I\dA\uand I\dB\uare different in some aspects.
.RT
.LP
.rs
.sp 14P
.ad r
\fBFigure 2/I.430, p. \fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
4.5
\fINT and TE associated wiring\fR
.sp 9p
.RT
.PP
The wiring from the TE or the NT to its appropriate jack affects
the interface electrical characteristics. A\ TE, or an\ NT that is not
permanently connected to the interface wiring, may be equipped with either
of the following for connection to the interface point (I\dA\uand I\dB\u,
respectively):
.RT
.LP
\(em
a hard wired
connecting cord
(of not more
than\ 10\ metres in the case of a TE, and not more than\ 3\ metres in the
case of an NT) and a suitable plug, or;
.LP
\(em
a jack with a connecting cord (of not more than\ 10\ metres in the case
of a TE, and not more than 3\ metres in the case of an\ NT) which has a
suitable plug at each end.
.PP
Normally, the requirements of\ I.430 apply to the interface point (I\dA\uand
I\dB\u, respectively), and the cord forms part of the associted\ TE
or\ NT. However, as a national option, where the terminating resistors are
connected internally to the\ NT, the connecting cord may be considered as an
integral part of the interface wiring. In this case, the requirements of
this Recommendation may be applied to the NT at the connection of the connecting
cord to the NT. Note that the NT may attach directly to the interface wiring
without a detachable cord. Also note that the connector, plug and jack
used for the connection of the
detachable cord
to the NT is not subject to
standardization.
.bp
.PP
Although a TE may be provided with a cord of less than\ 5\ metres in
length, it shall meet the requirements of this Recommendation with a cord
having a minimum length of\ 5\ metres. As specified above, the TE cord may be
detachable. Such a cord may be provided as a part of the TE, or the TE
may be designed to conform to the electrical characteristics specified
in\ \(sc\ 8 with a \*Qstandard ISDN basic access TE cord\*U conforming
to the requirements specified in\ \(sc\ 8.9 of this Recommendation and
having the maximum permitted capacitance.
.PP
The use of an
extension cord
, of up to\ 25\ metres in length,
with a TE is permitted but only on point\(hyto\(hypoint wiring configurations.
(The total attenuation of the wiring and of the cord in this case should
not
exceed\ 6\ dB.)
.RT
.sp 2P
.LP
\fB5\fR \fBFunctional characteristics\fR
.sp 1P
.RT
.PP
The following paragraphs show the functions for the interface.
.RT
.sp 2P
.LP
5.1
\fIInterface functions\fR
.sp 1P
.RT
.sp 1P
.LP
5.1.1
\fIB\(hychannel\fR
.sp 9p
.RT
.PP
This function provides, for each direction of transmission, two
independent 64\ kbit/s channels for use as B\(hychannels (as defined in
Recommendation\ I.412).
.RT
.sp 1P
.LP
5.1.2
\fIBit timing\fR
.sp 9p
.RT
.PP
This function provides bit (signal element) timing at\ 192\ kbit/s to enable
the TE and NT recover information from the
aggregate bit
stream
.
.RT
.sp 1P
.LP
5.1.3
\fIOctet timing\fR
.sp 9p
.RT
.PP
This function provides 8\ kHz octet timing for the NT and TE.
.RT
.sp 1P
.LP
5.1.4
\fIFrame alignment\fR
.sp 9p
.RT
.PP
This function provides information to enable NT and TE to recover the time
division multiplexed channels.
.RT
.sp 1P
.LP
5.1.5
\fID\(hychannel\fR
.sp 9p
.RT
.PP
This function provides, for each direction of transmission, one
D\(hychannel at a bit rate of 16\ kbit/s, as defined in Recommendation\ I.412.
.RT
.sp 1P
.LP
5.1.6
\fID\(hychannel access procedure\fR
.sp 9p
.RT
.PP
This function is specified to enable TEs to gain access to the
common resource of the D\(hychannel in an orderly controlled fashion. The
functions necessary for these procedures include an
echoed D\(hychannel
at a bit rate of\ 16\ kbit/s in the direction NT to TE. For the definition
of the
procedures relating to D\(hychannel access see\ \(sc\ 6.1.
.RT
.sp 1P
.LP
5.1.7
\fIPower feeding\fR
.sp 9p
.RT
.PP
This function provides for the capability to transfer power across the
interface. The direction of power transfer depends on the application.
In a typical application, it may be desirable to provide for power transfer
from the NT towards the TEs in order to, for example, maintain a
basic telephony
service
in the event of failure of the locally provided power. (In some
applications unidirectional power feeding or no power feeding at all, across
the interface, may apply.) The detailed specification of power feeding
capability is contained in\ \(sc\ 9.
.RT
.sp 1P
.LP
5.1.8
\fIDeactivation\fR
.sp 9p
.RT
.PP
This function is specified in order to permit the TE and NT to be placed
in a
low power consumption mode
when no calls are in progress. For TEs that are power fed across the interface
from power source\ 1 and for
remotely power fed NTs, deactivation places the functions that are so powered
into a low power consumption mode (see\ \(sc\ 9). The procedures and precise
conditions under which deactivation takes place are specified in\ \(sc\
6.2. (For
some applications it will be appropriate for NTs to remain in the active
state all the time.)
.bp
.RT
.sp 1P
.LP
5.1.9
\fIActivation\fR
.sp 9p
.RT
.PP
This function restores all the functions of a TE or an NT, which
may have been placed into a low power consumption mode during deactivation,
to an operating power mode (see\ \(sc\ 9), whether under normal or restricted
power
conditions. The procedures and precise conditions under which activation
takes place are defined in | (sc\ 6.2. (For some applications it will be
appropriate for NTs to remain in the active state all the time.)
.RT
.sp 1P
.LP
5.2
\fIInterchange circuits\fR
.sp 9p
.RT
.PP
Two interchange circuits, one for each direction of transmission, shall
be used to transfer digital signals across the interface. All of the
functions described in\ \(sc\ 5.1, except for power feeding, shall be carried
by
means of a digitally multiplexed signal structured as defined in\ \(sc\ 5.4.
.RT
.sp 1P
.LP
5.3
\fIConnected/disconnected indication\fR
.sp 9p
.RT
.PP
The
appearance/disapearance of power
is the criterion used by a TE to determine whether it is connected/disconnected
at the interface.
This is necessary for TEI (Terminal Endpoint Identifier) assignments
according to the procedures described in Recommendation\ I.441.
.PP
A TE which considers itself connected, when unplugged, can cause
duplication of TEI values after reconnection. When duplication occurs,
procedures described in Recommendation\ I.441 will permit recovery.
.RT
.sp 1P
.LP
5.3.1
\fITEs powered across the interface\fR
.sp 9p
.RT
.PP
A TE which is powered from power source\ 1 or\ 2 across the interface shall
use the detection of power source\ 1 or\ 2, respectively, to establish
the connection status. (See\ \(sc\ 9 and Figure\ 20/I.430 for a description
of the power sources.)
.RT
.sp 1P
.LP
5.3.2
\fITEs not powered across the interface\fR
.sp 9p
.RT
.PP
A TE which is not powered across the interface may use
either:
.RT
.LP
a)
the detection of power source\ 1 or power source\ 2, whichever may be
provided, to establish the connection status; or
.LP
b)
the presence/absence of local power to establish the
connection status.
.PP
TEs which are not powered across the interface and are unable to detect
the presence of power source\ 1 or\ 2 shall consider themselves
connected/disconnected when local power is applied/removed.
.PP
\fINote\fR \ \(em\ It is desirable to use the detection of power source\ 1 or
source\ 2 to establish the connection status when automatic TEI selection
procedures are used within the management entity.
.RT
.sp 1P
.LP
5.3.3
\fIIndication of connection status\fR
.sp 9p
.RT
.PP
TEs which use the detection of power source\ 1 or\ 2, whichever is
used to determine connection/disconnection, to establish the connection
status shall inform the management entity (for TEI purposes) using:
.RT
.LP
a)
MPH\(hyINFORMATION INDICATION (connected)
.LP
when operational power and the presence of power source\ 1
or\ 2, whichever is used to determine connection/disconnection, is detected;
and
.LP
b)
MPH\(hyINFORMATION INDICATION (disconnected)
.LP
when the disappearance of power source\ 1 or\ 2, whichever is used to
determine connection/disconnection, is detected, or power in the TE is
lost.
.PP
TEs which are unable to detect power source\ 1 or\ 2, whichever may be
provided, and, therefore, use the presence/absence of local power to
estabish the connection status [see\ \(sc\ 5.3.2\ b)], shall inform the
management
entity using:
.LP
a)
MPH\(hyINFORMATION INDICATION (disconnected)
.LP
when power (see Note) in the TE is lost;
.LP
b)
MPH\(hyINFORMATION INDICATION (connected)
.LP
when power (see Note) in the TE is applied.
.PP
\fINote\fR \ \(em\ The term \*Qpower\*U could be the full operational power or
backup power
. Backup power is defined such that it is enough to hold
TEI values in memory and maintain the capability of receiving and transmiting
layer\ 2 frames associated with the TEI procedures.
.bp
.sp 1P
.LP
5.4
\fIFrame structure\fR
.sp 9p
.RT
.PP
In both directions of transmission, the bits shall be grouped into frames
of\ 48\ bits each. The frame structure shall be identical for all
configurations (point\(hyto\(hypoint and point\(hyto\(hymultipoint).
.RT
.sp 1P
.LP
5.4.1
\fIBit rate\fR
.sp 9p
.RT
.PP
The nominal transmitted bit rate at the interfaces shall be
192\ kbit/s in both directions of transmission.
.RT
.sp 1P
.LP
5.4.2
\fIBinary organization of the frame\fR
.sp 9p
.RT
.PP
The frame structures are different for each direction of
transmission. Both structures are illustrated diagrammatically in
Figure\ 3/I.430.
.RT
.LP
.rs
.sp 29P
.ad r
\fBFigure 3/I.430, p. \fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
5.4.2.1
\fITE to NT\fR
.sp 9p
.RT
.PP
Each frame consists of the groups of bits shown in Table\ 2/I.430; each
individual group is d.c.\(hybalanced by its last bit\ (L\ bit).
.RT
.sp 1P
.LP
5.4.2.2
\fINT to TE\fR
.sp 9p
.RT
.PP
Frames transmitted by the NT contain an
echo channel
(E\ bits) used to retransmit the D\ bits received from the TEs. The D\(hyecho
channel is used for D\(hychannel access control. The last bit of the frame
(L\ bit) is used for balancing each complete frame.
.PP
The bits are grouped as shown in Table\ 3/I.430.
.bp
.RT
.ce
\fBH.T. [T2.430]\fR
.ce
TABLE\ 2/I.430
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(144p) .
Bit position Group
_
.T&
lw(48p) | lw(144p) .
1 and 2 {
Framing signal with balance bit
}
.T&
lw(48p) | lw(144p) .
3 \(hy 11 {
B1\(hychannel (first octet) with balance bit
}
.T&
lw(48p) | lw(144p) .
12 and 13 {
D\(hychannel bit with balance bit
}
.T&
lw(48p) | lw(144p) .
14 and 15 {
F
A auxiliary framing bit or Q\ bit
with balance bit
}
.T&
lw(48p) | lw(144p) .
16 \(hy 24 {
B2\(hychannel (first octet) with balance bit
}
.T&
lw(48p) | lw(144p) .
25 and 26 {
D\(hychannel bit with balance bit
}
.T&
lw(48p) | lw(144p) .
27 \(hy 35 {
B1\(hychannel (second octet) with balance bit
}
.T&
lw(48p) | lw(144p) .
36 and 37 {
D\(hychannel bit with balance bit
\fR
}
.T&
lw(48p) | lw(144p) .
38 \(hy 46 {
B2\(hychannel (second octet) with balance bit
}
.T&
lw(48p) | lw(144p) .
47 and 48 {
D\(hychannel bit with balance bit
}
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 2/I.430 [T2.430], p. 11\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 4
.ce
\fBH.T. [T3.430]\fR
.ce
TABLE\ 3/I.430
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(120p) .
Bit position Group
_
.T&
lw(48p) | lw(120p) .
1 and 2 {
Framing signal with balance bit
}
.T&
lw(48p) | lw(120p) .
3 \(hy 10 B1\(hychannel (first octet)
.T&
lw(48p) | lw(120p) .
11 E, D\(hyecho\(hychannel bit
.T&
lw(48p) | lw(120p) .
12 D\(hychannel bit
.T&
lw(48p) | lw(120p) .
13 Bit A used for activation
.T&
lw(48p) | lw(120p) .
14 F A auxiliary framing bit
.T&
lw(48p) | lw(120p) .
15 {
N bit (coded as defined in \(sc\ 6.3)
}
.T&
lw(48p) | lw(120p) .
16 \(hy 23 B2\(hychannel (first octet)
.T&
lw(48p) | lw(120p) .
24 E, D\(hyecho\(hychannel bit
.T&
lw(48p) | lw(120p) .
25 D\(hychannel bit
.T&
lw(48p) | lw(120p) .
26 M, multiframing bit
.T&
lw(48p) | lw(120p) .
27 \(hy 34 B1\(hychannel (second octet)
.T&
lw(48p) | lw(120p) .
35 E, D\(hyecho\(hychannel bit
.T&
lw(48p) | lw(120p) .
36 D\(hychannel bit
.T&
lw(48p) | lw(120p) .
37 {
S, The use of this bit is for further study
}
.T&
lw(48p) | lw(120p) .
38 \(hy 45 B2\(hychannel (second octet)
.T&
lw(48p) | lw(120p) .
46 E, D\(hyecho\(hychannel bit
.T&
lw(48p) | lw(120p) .
47 D\(hychannel bit
.T&
lw(48p) | lw(120p) .
48 {
Frame balance bit
}
_
.TE
.LP
\fINote\fR
\ \(em\ S is set to binary ZERO.
.nr PS 9
.RT
.ad r
\fBTableau 3/I.430 [T3.430], p. 12\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
5.4.2.3
\fIRelative bit positions\fR
.sp 9p
.RT
.PP
At the TEs, timing in the direction TE to NT shall be derived from the
frames received from the NT.
.PP
The first bit of each frame transmitted from a TE towards the NT shall
be delayed, nominally, by two bit periods with respect to the first bit
of the frame received from the NT. Figure\ 3/I.430 illustrates the relative
bit
positions for both transmitted and received frames.
.RT
.sp 1P
.LP
5.5
\fILine code\fR
.sp 9p
.RT
.PP
For both directions of transmission,
pseudo\(hyternary coding
is used with\ 100% pulse width as shown in Figure\ 4/I.430. Coding is performed
in such a way that a binary ONE is represented by no line signal; whereas,
a
binary ZERO is represented by a positive or negative pulse. The first binary
ZERO following the framing bit\(hybalance bit is of the same polarity as the
framing bit\(hybalance bit. Subsequent binary ZEROs must alternate in polarity.
A balance bit is a binary ZERO if the number of binary ZEROs following
the
previous balance bit is odd. A balance bit is a binary ONE if the number of
binary ZEROs following the previous balance bit is even.
.RT
.LP
.rs
.sp 11P
.ad r
\fBFigure 4/I.430, p. \fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
5.6
\fITiming considerations\fR
.sp 9p
.RT
.PP
The NT shall derive its timing from the
network clock
. A TE shall derive its timing (bit, octet, frame) from the signal received
from the NT and use this derived timing to synchronize its transmitted
signal.
.RT
.sp 2P
.LP
\fB6\fR \fBInterface procedures\fR
.sp 1P
.RT
.sp 1P
.LP
6.1
\fID\(hychannel access procedure\fR
.sp 9p
.RT
.PP
The following procedure allows for a number of TEs connected in a multipoint
configuration to gain access to the D\(hychannel in an orderly fashion.
The procedure always ensures that, even in cases where two or more TEs
attempt to access the D\(hychannel simultaneously, one, but only one, of
the TEs will be successful in completing transmission of its information.
This procedure relies upon the use of layer\ 2 frames delimited by flags
consisting of the binary
pattern\ \*Q01111110\*U and the use of zero bit insertion to prevent flag
imitation (see Recommendation\ I.441).
.PP
The procedure also permits TEs to operate in a point\(hyto\(hypoint
manner.
.RT
.sp 1P
.LP
6.1.1
\fIInterframe (layer 2)\fR
\fItime fill\fR
.sp 9p
.RT
.PP
When a TE has no layer\ 2 frames to transmit, it shall send binary ONEs
on the D\(hychannel,\ i.e., the
interframe time fill
in the TE\(hyto\(hyNT direction shall be binary ONEs.
.PP
When an NT has no layer 2 frames to transmit, it shall send binary
ONEs or HDLC flags,\ i.e., the interframe time fill in the NT\(hyto\(hyTE
direction
shall be either all binary ONEs or repetitions of the octet\ \*Q01111110\*U.
When
the
interframe time fill
is
HDLC flags
, the flag which defines the end of a frame may define the start of the
next frame.
.bp
.RT
.sp 1P
.LP
6.1.2
\fID\(hyecho channel\fR
.sp 9p
.RT
.PP
The NT, on receipt of a D\(hychannel bit from TE or TEs, shall reflect
the binary value in the next available D\(hyecho channel bit position towards
the TE. (It may be necessary to force the D\(hyecho channel bits to all
binary ZEROs during certain loopbacks\ \(em\ see Note\ 4 of Table\ I.1/I.430
and\ \(sc\ 5 of
Recommendation\ G.960).
.RT
.sp 1P
.LP
6.1.3
\fID\(hychannel monitoring\fR
.sp 9p
.RT
.PP
A TE, while in the active condition, shall monitor the D\(hyecho
channel, counting the number of consecutive binary ONEs. If a ZERO bit is
detected, the TE shall restart counting the number of consecutive ONE bits.
The current value of the count is called\ C.
.PP
\fINote\fR \ \(em\ C need not be incremented after the value eleven has been
reached.
.RT
.sp 1P
.LP
6.1.4
\fIPriority mechanism\fR
.sp 9p
.RT
.PP
Layer 2 frames are transmitted in such a way that signalling
information is given priority (priority class\ 1) over all other types of
information (priority class\ 2). Furthermore, to ensure that within each
priority class all competing TEs are given a fair access to the D\(hychannel,
once a TE has successfully completed the transmission of a frame, it is
given a
lower level of priority within that class. The TE is given back its normal
level within a priority class when all TEs have had an opportunity to transmit
information at the normal level within that priority class.
.PP
The
priority class
of a particular layer 2 frame may be
a characteristic of the TE which is preset at manufacture or at installation,
or it may be passed down from layer\ 2 as a parameter of the PH\(hyDATA
REQUEST
primitive.
.PP
The priority mechanism is based on the requirement that a TE may start
layer\ 2 frame transmission only when\ C (see\ \(sc\ 6.1.3) is equal to,
or exceeds, the value\ X\d1\ufor priority class\ 1 or is equal to, or exceeds,
the
value\ X\d2\ufor priority class\ 2. The value of\ X\d1\ushall be eight for the
normal level and nine for the lower level of priority. The value of\ X\d2\ushall
be ten for the normal level and eleven for the lower level of priority.
.PP
In a priority class the value of the normal level of priority is
changed into the value of the lower level of priority (i.e.\ higher value)
when a TE has successfully transmitted a layer\ 2 frame of that priority
class.
.PP
The value of the lower level of priority is changed back to the value of
the normal level of priority when\ C (see\ \(sc\ 6.1.3) equals the value
of the
lower level of priority, (i.e.\ higher value).
.RT
.sp 1P
.LP
6.1.5
\fICollision detection\fR
.sp 9p
.RT
.PP
While transmitting information in the D\(hychannel, the TE
shall monitor the received D\(hyecho channel and compare the last transmitted
bit with the next available D\(hyecho bit. If the transmitted bit is the
same as the received echo, the TE shall continue its transmission. If,
however, the
received echo is different from the transmitted bit, the TE shall cease
transmission immediately and return to the
D\(hychannel monitoring
state
.
.RT
.sp 1P
.LP
6.1.6
\fIPriority system\fR
.sp 9p
.RT
.PP
Annex B describes an example of how the priority system may be
implemented.
.RT
.LP
6.2\ \
\fIActivation/deactivation\fR
.sp 1P
.RT
.sp 2P
.LP
6.2.1\ \ \fIDefinitions\fR
.sp 1P
.RT
.sp 1P
.LP
6.2.1.1\ \
\fITE states\fR
.sp 9p
.RT
.sp 1P
.LP
6.2.1.1.1\ \ State F1 (inactive): In this inactive state the TE is not
transmitting. In the case of locally powered TEs which cannot detect the
appearance/disappearance of power source\ 1 or\ 2, this state is entered when
local power is not present. For TEs which can detect power source\ 1 or power
source\ 2, this state is entered whenever loss of power (required to support
all TEI functions) is detected, or when the absence of power from source\
1 or\ 2,
whichever power source is used for determining the connection status, is
detected.
.sp 9p
.RT
.LP
6.2.1.1.2\ \ State F2 (sensing): This state is entered after the TE has been
powered on but has not determined the type of signal (if any) that the TE is
receiving.
.bp
.LP
6.2.1.1.3\ \ State F3 (deactivated): This is the deactivated state of the
physical protocol. Neither the NT nor the TE is transmitting.
.LP
6.2.1.1.4\ \ State F4 (awaiting signal): When the TE is requested to initiate
activation by means of a
PH\(hyACTIVATE REQUEST primitive, it transmits a
signal (INFO\ 1) and waits for a response from the NT.
.LP
6.2.1.1.5\ \ State F5 (identifying input): At the first receipt of any signal
from the NT, the TE ceases to transmit INFO\ 1 and awaits identification of
signal INFO\ 2 or INFO\ 4.
.LP
6.2.1.1.6\ \ State F6 (synchronized): When the TE receives an activation
signal (INFO\ 2) from the NT, it responds with a signal (INFO\ 3) and waits
for normal frames (INFO\ 4) from the NT.
.LP
6.2.1.1.7\ \ State F7 (activated): This is the normal active state with the
protocol activated in both directions. Both the NT and the TE are transmitting
normal frames.
.LP
6.2.1.1.8\ \ State F8 (lost framing): This is the condition when the TE
has lost frame synchronization and is awaiting re\(hysynchronization by
receipt of INFO\ 2 or INFO\ 4 or deactivation by receipt of INFO\ 0.
.sp 2P
.LP
6.2.1.2\ \
\fINT states\fR
.sp 1P
.RT
.sp 1P
.LP
6.2.1.2.1\ \ State G1 (deactive): In this deactivated state the NT is not
transmitting.
.sp 9p
.RT
.LP
6.2.1.2.2\ \ State G2 (pending activation): In this partially active state
the NT sends INFO\ 2 while waiting for INFO\ 3. This state will be entered
on request
by higher layers, by means of a PH\(hyACTIVATE REQUEST primitive, or on the
receipt of INFO\ 0 or lost framing while in the active state\ (G3). Then the
choice to eventually deactivate is up to higher layers within the NT.
.LP
6.2.1.2.3\ \ State G3 (active): This is the normal active state where the
NT and TE are active with INFO\ 4 and INFO\ 3, respectively. A deactivation
may be
initiated by the NT system management, by means of an MPH\(hyDEACTIVE REQUEST
primitive, or the NT may be in the active state all the time, under non\(hyfault
conditions.
.LP
6.2.1.2.4\ \ State G4 (pending deactivation): When the NT wishes to deactivate,
it may wait for a timer to expire before returning to the deactivated state.
.sp 1P
.LP
6.2.1.3
\fIActivate primitives\fR
.sp 9p
.RT
.PP
The following primitives should be used between layers\ 1 and\ 2 and between
layer\ 1 and the management entity in the activation procedures. For use
in state diagrams,\ etc., abbreviations of the primitive names are also
given.
.RT
.LP
PH\(hyACTIVATE REQUEST (PH\(hyAR)
.LP
PH\(hyACTIVATE INDICATION (PH\(hyAI)
.LP
MPH\(hyACTIVATE INDICATION (MPH\(hyAI)
.sp 1P
.LP
6.2.1.4
\fIDeactivate primitives\fR
.sp 9p
.RT
.PP
The following primitives should be used between layers\ 1 and\ 2 and between
layer\ 1 and the management entity in the deactivation procedures. For
use in state diagrams, etc., abbreviations of the primitive names are also
given.
.RT
.LP
MPH\(hyDEACTIVATE REQUEST (MPH\(hyDR)
.LP
MPH\(hyDEACTIVATE INDICATION (MPH\(hyDI)
.LP
PH\(hyDEACTIVATE INDICATION (PH\(hyDI)
.sp 1P
.LP
6.2.1.5
\fIManagement primitives\fR
.sp 9p
.RT
.PP
The following primitives should be used between layer\ 1 and the
management entity. For use in state diagrams, etc., abbreviations of the
primitive names are also given.
.RT
.LP
MPH\(hyERROR INDICATION (MPH\(hyEI)
.LP
Message unit contains type of error or recovery from a previously reported
error.
.LP
MPH\(hyINFORMATION INDICATION (MPH\(hyII)
.LP
Message unit contains information regarding the physical layer
conditions. Two parameters are provisionally defined: connected and
disconnected.
.PP
\fINote\fR \ \(em\ Implementation of primitives in NTs and TEs is not for
recommendation.
.bp
.sp 1P
.LP
6.2.1.6
\fIValid primitive sequences\fR
.sp 9p
.RT
.PP
The primitives defined in\ \(sc\ 6.2.1.3, \(sc\ 6.2.1.4 and\ \(sc\ 6.2.1.5
specify, conceptually, the service provided by layer\ 1 to layer\ 2 and the
layer\ 1 management entity. The constraints on the sequence in which the
primitives may occur are specified in Figure\ 5/I.430. These diagrams do not
represent the states which must exist for the layer\ 1 entity. However,
they do illustrate the condition that the layer\ 2 and management enities
perceive
layer\ 1 to be in at a result of the primitives transferred between entities.
Furthermore, Figure\ 5/I.430 does not represent an interface and is used only
for modelling purposes.
.RT
.LP
.rs
.sp 45P
.ad r
\fBFigure 5/I.430, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
6.2.2
\fISignals\fR
.sp 9p
.RT
.PP
The identifications of specific signals across the
S/T
reference point
are given in Table\ 4/I.430. Also included is the coding for these signals.
.RT
.LP
.sp 1
.ce
\fBH.T. [T4.430]\fR
.ce
TABLE\ 4/I.430
.ce
\fBDefinition of INFO signals\fR
.ce
(Note 1)
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(114p) | cw(114p) .
Signals from NT to TE Signals from TE to NT
_
.T&
lw(30p) | lw(84p) | lw(30p) | lw(84p) .
INFO\ 0 No signal. INFO\ 0 No signal.
.T&
lw(30p) | lw(84p) | lw(30p) | cw(84p) .
INFO\ 1 (Note\ 2) {
A continuous signal with the following pattern:
Positive ZERO, negative ZERO, six ONEs.
\fBMONTAGE Figure CCITT 62731\fR
Nominal bit rate\ = 192\ kbit/s. \fR
}
.T&
lw(30p) | lw(84p) | lw(30p) | cw(84p) .
INFO\ 2 (Note\ 3) {
Frame with all bits of B, D, and D\(hyecho channels set to
binary ZERO. Bit\ A set to binary ZERO. N\ and\ L\ bits set
according to the normal coding
rules.
}
.T&
lw(30p) | lw(84p) | lw(30p) | lw(84p) .
INFO\ 3 {
Synchronized frames with operational data on
B\ and\ D\ channels.
}
.T&
lw(30p) | lw(84p) | lw(30p) | lw(84p) .
INFO\ 4 (Note\ 3) {
Frames with operational data on B, D, and D\(hyecho channels.
Bit\ A set to binary ONE.
}
.TE
.LP
\fINote\ 1\fR
\ \(em\ For configurations where the wiring polarity may
be reversed (see\ \(sc\ 4.3) signals may be received with the polarity
of the binary ZEROs inverted. All NT and TE receivers should be
designed to tolerate wiring polarity reversals.
.LP
\fINote\ 2\fR
\ \(em\ TEs which do not need the capability to initiate activation
of a deactivated I.430 interface (e.g., TEs required to handle only
incoming calls) need not have the capability to send INFO\ 1. In all
other respects, these TEs shall be in accordance with \(sc\ 6.2. It should
be noted that in the point\(hyto\(hymultipoint configuration more than one
TE transmitting simultaneously will produce a bit pattern, as received
by the NT, different form that described above, e.g., two or more
overlapping (asynchronous) instances of INFO\ 1.
.LP
\fINote\ 3\fR
\ \(em\ During the transmission of INFO\ 2 or INFO\ 4, the\ F
A bits and
the M\ bits from the NT may provide the Q\(hybit pattern designation as
described in \(sc\ 6.3.3.
.nr PS 9
.RT
.ad r
\fBTable 4/I.430 [T4.430], p. \fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
.sp 1
6.2.3
\fIActivation/deactivation procedure for TEs\fR
.sp 1P
.RT
.sp 1P
.LP
6.2.3.1
\fIGeneral TE procedures\fR
.sp 9p
.RT
.PP
All TEs conform to the following (these statements are an aid to
understanding; the complete procedures are specified in\ \(sc\ 6.2.3.2):
.RT
.LP
a)
TEs, when first connected, when power is applied, or upon
the loss of frame alignment (see\ \(sc\ 6.3.1.1) shall transmit INFO\ 0.
However, the TE that is disconnected but powered is a special situation
and could be
transmitting INFO\ 1 when connected.
.LP
b)
TEs transmit INFO\ 3 when frame alignment is established
(see\ \(sc\ 6.3.1.2). However, the satisfactory transmission of operational
data
cannot be assured prior to the receipt of INFO\ 4.
.LP
c)
TEs that are locally powered shall, when power is removed, initiate the
transmission of INFO\ 0 before frame alignment is lost.
.bp
.sp 1P
.LP
6.2.3.2
\fISpecification of the procedure\fR
.sp 9p
.RT
.PP
The procedure for TEs which can detect power source\ 1 or\ 2 is shown in
the form of a finite state matrix Table\ 5/I.430. An SDL representation
of
the procedure is outlined in Annex\ C. The finite state matrices for two
other TE types are given in Annex\ C, Tables\ C\(hy1/I.430 and\ C\(hy2/I.430.
The finite state matrix and SDL representations reflect the requirements
necessary to assure
proper interfacing of a TE with an NT conforming to the procedures described
in Table\ 6/I.430. They also describe primitives at the layer\ 1/2 boundary
and
layer\ 1/management entity boundary.
.RT
.sp 2P
.LP
6.2.4
\fIActivation/deactivation for NTs\fR
.sp 1P
.RT
.sp 1P
.LP
6.2.4.1
\fIActivating/deactivating NTs\fR
.sp 9p
.RT
.PP
The procedure is shown in the form of a finite state matrix in
Table\ 6/I.430. An SDL representation of the procedure is outlined in Annex\
C. The
finite state matrix
and SDL representations reflect the
requirements necessary to assure proper interfacing of an
activating/deactivating NT with a TE conforming to the procedures described
in Table\ 5/I.430. They also describe primitives at the layer\ 1/2 boundary
and
layer\ 1/management entity boundary.
.RT
.sp 1P
.LP
6.2.4.2
\fINon\(hyactivating/non\(hydeactivating NTs\fR
.sp 9p
.RT
.PP
The behaviour of such NTs is the same as that of an
activating/deactivating NT never receiving MPH\(hyDEACTIVATE REQUEST from the
management entity. States\ G1 (deactive), G4 (pending deactivation) and
timers\ 1 and\ 2 may not exist from such NTs.
.RT
.sp 1P
.LP
6.2.5
\fITimer values\fR
.sp 9p
.RT
.PP
The finite state matrix tables show timers on both the TE and the NT. The
following values are defined for timers:
.RT
.LP
\(em
TE:\ Timer\ 3, not to be specified (the value depends on the
subscriber loop transmission technique. The worst case value is\ 30s).
.LP
\(em
NT:\ Timer\ 1, not to be specified.
.LP
NT:\
Timer\ 2, 25 to 100 ms.
.sp 2P
.LP
6.2.6
\fIActivation times\fR
.sp 1P
.RT
.sp 1P
.LP
6.2.6.1
\fITE activation times\fR
.sp 9p
.RT
.PP
A TE in the deactivated state (F3) shall, upon the receipt of
INFO\ 2, establish frame synchronization and initiate the transmission
of INFO\ 3 within\ 100\ ms. A TE shall recognize the receipt of INFO\ 4
within two frames (in the absence of errors).
.PP
A TE in the \*Qwaiting for signal\*U state (F4) shall, upon the receipt
of INFO\ 2, cease the transmission of INFO\ 1 and initiate the transmission
of
INFO\ 0 within\ 5\ ms and then respond to INFO\ 2, within\ 100\ ms, as
above. (Note that in Table\ 5/I.430, the transition from\ F4 to\ F5 is
indicated as the result of the receipt of \*Qany signal\*U which is in
recognition of the fact that a TE
may not know that the signal being received is INFO\ 2 until after it has
recognized the presence of a signal.)
.RT
.sp 1P
.LP
6.2.6.2
\fINT activation times\fR
.sp 9p
.RT
.PP
An NT in the deactivate state (G1) shall, upon the receipt of
INFO\ 1, initiate the transmission of INFO\ 2 (synchronized to the network)
within\ 1\ s under normal conditions. Delays, \*QDa\*U, as long as\ 30\ s are
acceptable under abnormal (non\(hyfault) conditions, e.g.,\ as a result
of a need for retrain for an associated loop transmission system.
.PP
An NT in the \*Qpending activation\*U state (G2) shall, upon the receipt
of INFO\ 3, initiate the transmission of INFO\ 4 within 500\ ms under normal
conditions. Delays, \*QDb\*U, as long as\ 15\ s are acceptable under abnormal
(non\(hyfault) conditions provided that the sum of the delays \*QDa\*U
and \*QDb\*U are
not greater than\ 30\ s.
.bp
.RT
.ce
\fBH.T. [1T5.430]\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(312p) .
TABLE\ 5/I.430
.T&
cw(312p) .
{
\fBActivation/deactivation layer 1 finite state matrix for TEs\fR
\fBTEs powered from power source 1 ou 2\fR
}
.TE
.TS
center box ;
cw(72p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
| | | | | | | | |
.T&
rw(43p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
State name Inactive Sensing Deactivated Awaiting signal Identifying input Synchronized Activated Lost framing
State number F1 F2 F3 F4 F5 F6 F7 F8
Event | | | | | | INFO sent | | | | | | INFO 0 | | INFO 0 | | INFO 0 | | INFO 1 | | INFO 0 | | INFO 3 | | INFO 3 | | INFO 0 | |
.T&
lw(72p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
{
Power on and detection of Power\ S
(Note 1 and Note 2)
} F2 \(em \(em \(em \(em \(em \(em \(em
_
Loss of power (Note\ 1) \(em F1 MPH\(hyII(d); F1 {
MPH\(hyII(d),
MPH\(hyDI,
PH\(hyDI;
F1
} {
MPH\(hyII(d),
MPH\(hyDI,
PH\(hyDI;
F1
} {
MPH\(hyII(d),
MPH\(hyDI,
PH\(hyDI;
F1
} {
MPH\(hyII(d),
MPH\(hyDI,
PH\(hyDI;
F1
} {
MPH\(hyII(d),
MPH\(hyDI,
PH\(hyDI;
F1
}
_
.T&
lw(72p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
{
Disappearance of power\ S
(Note\ 2)
} \(em F1 MPH\(hyII(d); F1 {
MPH\(hyII(d),
MPH\(hyDI,
PH\(hyDI;
F1
} {
MPH\(hyII(d),
MPH\(hyDI,
PH\(hyDI;
F1
} {
MPH\(hyII(d),
MPH\(hyDI,
PH\(hyDI;
F1
} {
MPH\(hyII(d),
MPH\(hyDI,
PH\(hyDI;
F1
} {
MPH\(hyII(d),
MPH\(hyDI,
PH\(hyDI;
F1
}
.T&
lw(72p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
PH\(hyACTIVATE REQUEST / | ST. T3; F4 | | \(em | \(em
.T&
lw(72p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Expiry T3 / / \(em MPH\(hyDI, PH\(hyDI; F3 MPH\(hyDI, PH\(hyDI; F3 MPH\(hyDI, PH\(hyDI; F3 \(em \(em
.T&
lw(72p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Receive INFO\ 0 / MPH\(hyII(c); F3 \(em \(em \(em MPH\(hyDI, PH\(hyDI; F3 MPH\(hyDI, PH\(hyDI; F3 {
MPH\(hyDI,
PH\(hyDI,
MPH\(hyEI2;
F3
}
_
.T&
lw(72p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Receive any signal (Note\ 3) / \(em \(em F5 \(em / / \(em
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 5/I.430 [1T5.430] (\*`a l'italienne), p. 16\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [2T5.430]\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(312p) .
{
TABLE\ 5/I.430 \fI(cont.)\fR
}
.T&
cw(312p) .
{
\fBActivation/deactivation layer 1 finite state matrix for TEs\fR
\fBTEs powered from power source 1 ou 2\fR
}
.TE
.TS
center box;
cw(72p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
| | | | | | | | |
.T&
rw(43p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
State name Inactive Sensing Deactivated Awaiting signal Identifying input Synchronized Activated Lost framing
.T&
lw(291p) .
.T&
rw(34p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
State number F1 F2 F3 F4 F5 F6 F7 F8
.T&
lw(274p) .
.T&
lw(48p) | rw(24p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Event | | | | | | INFO sent | | | | | | INFO 0 | | INFO 0 | | INFO 0 | | INFO 1 | | INFO 0 | | INFO 3 | | INFO 3 | | INFO 0 | |
.T&
lw(72p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Receive INFO\ 2 / MPH\(hyII(c); F6 F6 / F6 (Note\ 4) \(em MPH\(hyEI1; F6 MPH\(hyEI2; F6
_
.T&
lw(72p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Receive INFO\ 4 / {
MPH\(hyII(c),
PH\(hyAI,
MPH\(hyAI;
F7
} PH\(hyAI, MPH\(hyAI; F7 / {
PH\(hyAI,
MPH\(hyAI;
F7
(Note\ 4)
} {
PH\(hyAI,
MPH\(hyAI,
MPH\(hyEI2;
F7
} \(em {
PH\(hyAI,
MPH\(hyAI,
MPH\(hyEI2;
F7
}
_
.T&
lw(72p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) .
Lost framing / / / / / MPH\(hyEI1; F8 MPH\(hyEI1; F8 \(em
_
.T&
lw(138p) | lw(12p) | lw(162p) .
{
\(em
No change, no action
|
Impossible by the definition of the layer\ 1 service
/
Impossible situation
a, b; Fn
Issue primitives \*Qa\*U and \*Qb\*U and then go to
state\ \*QFn\*U
PH\(hyAI
Primitive PH\(hyACTIVATE INDICATION
PH\(hyDI
Primitive PH\(hyDEACTIVATE INDICATION
MPH\(hyAI
Primitive MPH\(hyACTIVATE INDICATION
} {
MPH\(hyDI
Primitive MPH\(hyDEACTIVATE INDICATION
MPH\(hyEI1
Primitive MPH\(hyERROR INDICATION
reporting error
MPH\(hyEI2
Primitive MPH\(hyERROR INDICATION
reporting recovery from error
MPH\(hyII(c)
Primitive MPH\(hyINFORMATION INDICATION (connected)
MPH\(hyII(d)
Primitive MPH\(hyINFORMATION INDICATION (disconnected)
ST. T3
Start timer\ T3
Power\ S
Power source 1 or power source 2. \fR
}
.T&
lw(312p) .
{
Primitives are signals in a conceptual queue and will be cleared
on recognition, while the INFO signals are continuous signals which
are available all the time.
}
.TE
.LP
\fINote\ 1\fR
\ \(em\ The term \*Qpower\*U could be the full operational power
or backup power. Backup power is defined such that it is enough
to hold the TEI value in memory and maintain the capability of receiving
and transmitting layer\ 2 frames associated with the TEI
procedures.
.LP
\fINote\ 2\fR
\ \(em\ The procedures described in Table\ 5/I.430 require the provision
of power source\ 1 or power source\ 2 to enable their complete operation.
A TE which determines that it is connected to an NT not providing power
source\ 1 or 2 should default to the procedures described in
Table\ C\(hy1/I.430.
.LP
\fINote\ 3\fR
\ \(em\ This event reflects the case where a signal is received
and the TE has not (yet) determined whether it is INFO\ 2 or
INFO\ 4.
.LP
\fINote\ 4\fR
\ \(em\ If INFO 2 or INFO 4 is not recognized within
5\ ms after the appearance of a signal, TEs must go to\ F5.
.RT
.ad r
\fBTableau 5/I.430 [2T5.430] (\*`a l'italienne), p. 17\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [1T6.430]\fR
.ce
TABLE\ 6/I.430
.ce
\fBActivation/deactivation layer 1 finite state matrix for NTs
.T&
lw(72p) | lw(42p) | lw(36p) | lw(42p) | lw(36p) .
.T&
lw(72p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
PH\(hyACTIVATE REQUEST Start timer T1 G2 | | Start timer T1 G2
_
.T&
lw(72p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
MPH\(hyDEACTIVATE REQUEST | Start timer T2 PH\(hyDI; G4 Start timer T2
PH\(hyDI; G4 |
.T&
lw(72p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
Expiry T1 (Note\ 1) \(em Start timer T2 PH\(hyDI; G4 / \(em
_
.T&
lw(72p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
Expiry T2 (Note\ 2) \(em \(em \(em G1
.T&
lw(72p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
Receiving INFO\ 0 \(em \(em {
MPH\(hyDI, MPH\(hyEI; G2
(Note\ 3)
} G1
_
.T&
lw(72p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
Receiving INFO\ 1 Start timer T1 G2 \(em / \(em
_
.T&
lw(72p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
Receiving INFO\ 3 / {
Stop timer T1
PH\(hyAI, MPH\(hyAI; G3
(Note\ 4)
} \(em \(em
_
.T&
lw(72p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
Lost framing / / {
MPH\(hyDI, MPH\(hyEI;
G2
(Note\ 3)
} \(em
_
.T&
lw(72p) | cw(42p) | cw(36p) | cw(42p) | cw(36p) .
{
\(em
No state change
/
Impossible by the definition of peer\(hyto\(hypeer physical
layer procedures or system internal
reasons
|
Impossible by the definition of the physical layer
service
a, b; Gn
Issue primitives \*Qa\*U and \*Qb\*U then go to
state\ \*QGn\*U
PH\(hyAI
Primitive PH\(hyACTIVATE INDICATION
PH\(hyDI
Primitive PH\(hyDEACTIVATE INDICATION
MPH\(hyAI
Primitive MPH\(hyACTIVATE INDICATION
MPH\(hyDI
Primitive MPH\(hyDEACTIVATE INDICATION
MPH\(hyEI
Primitive MPH\(hyERROR INDICATION
Primitives are signals in a conceptual queue and will be cleared
on recognition, while the INFO signals are continuous signals which
are available all the time.
}
.TE
.nr PS 9
.RT
.ad r
\fBTableau 6/I.430 [1T6.430], p. 18\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBDU TABLEAU SUR NOUVELLE PAGE\fR
.ce
\fBH.T. [T1.430]\fR
.ce
TABLE\ 1/I.430
.ce
\fBPrimitives associated with layer\ 1\fR
.TS
center box ;
lw(228p) .
L1 | (<- \(ra | 2
M | (<- \(ra | 1
_
.TE
.TS
center box;
lw(54p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | lw(54p) .
MPH\(hyERROR \(em X \(em X {
Type of error or recovery from a
previously reported error
}
_
.T&
lw(54p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | lw(54p) .
MPH\(hyACTIVATE \(em X \(em \(em
_
.T&
lw(54p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | lw(54p) .
MPH\(hyDEACTIVATE X X \(em \(em
_
.T&
lw(54p) | cw(30p) | cw(30p) | cw(30p) | cw(30p) | lw(54p) .
MPH\(hyINFORMATION \(em X \(em X {
Connected/disconnected
}
.TE
.LP
\fINote\ 1\fR
\ \(em\ PH\(hyDATA REQUEST implies underlying negotiation
between layer\ 1 and layer\ 2 for the acceptance of the data.
.LP
\fINote\ 2\fR
\ \(em\ Priority indication applies only to the request
type.
.nr PS 9
.RT
.ad r
\fBTableau 6/I.430 [2T6.430], p. 19\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 2
.sp 1P
.LP
6.2.7
\fIDeactivation times\fR
.sp 9p
.RT
.PP
A TE shall respond to the receipt of INFO\ 0 by initiating the
transmission of INFO\ 0 within\ 25\ ms.
.PP
An NT shall respond to the receipt of INFO\ 0 or the loss of frame
synchronization by initiating the transmission of INFO\ 2 within\ 25\ ms;
however, the layer\ 1 entity does not deactivate in response to INFO\ 0
from a TE.
.RT
.sp 1P
.LP
6.3
\fIFrame alignment procedures\fR
.sp 9p
.RT
.PP
The first bit of each frame is the framing bit,\ F; it is a binary ZERO.
.PP
The frame alignement procedure makes use of the fact that the framing bit
is represented by a pulse having the same polarity as the preceding pulse
(
line code violation
). This allows rapid reframing.
.PP
According to the coding rule, both the
framing bit
and the
first binary ZERO bit following the framing bit\(hybalance bit (in position\
2 in the same frame) produce a line code violation. To guarantee secure
framing, the auxiliary framing bit pair\ F\dA\uand\ N in the direction
NT to TE or the
auxiliary framing bit\ F\dA\uwith the associated
balancing bit
\ L in the direction TE to NT are introduced. This ensures that there is
a line code
violation at\ 14\ bits or less from the framing bit\ F, due to\ F\dA\uor\
N being a binary ZERO bit (NT to TE) or to\ F\dA\ubeing a binary ZERO bit
(TE to NT) if
the\ F\dA\ubit position is not used as a\ Q\ bit. The framing procedures do not
depend on the polarity of the framing bit\ F, and thus are not sensitive to
wiring polarity.
.PP
The coding rule for the auxiliary framing bit pair\ F\dA\uand\ N, in the
direction NT to TE, is such that N is the binary opposite of F\dA\u(N\
=\
F\dA\u). The F\dA\uand\ L\ bits in the direction TE to NT are always coded
such that the binary values of F\dA\uand\ L are equal.
.RT
.sp 1P
.LP
6.3.1
\fIFrame alignment procedure in the direction NT to TE\fR
.sp 9p
.RT
.PP
Frame alignment, on initial activation of the TE, shall comply with the
procedures defined in\ \(sc\ 6.2.
.RT
.sp 1P
.LP
6.3.1.1
\fILoss of frame alignment\fR
.sp 9p
.RT
.PP
Loss of frame alignment may be assumed when a time period
equivalent to two\ 48\(hybit frames has elapsed without having detected
valid pairs of
line code violations
obeying the\ \(=\ 14\ bit criterion as described
above. The TE shall cease transmission immediately.
.RT
.sp 1P
.LP
6.3.1.2
\fIFrame alignments\fR
.sp 9p
.RT
.PP
Frame alignment may be assumed to occur when three consecutive
pairs of line code violations obeying the\ \(=\ 14\ bit criterion have been
detected.
.bp
.RT
.sp 1P
.LP
6.3.2
\fIFrame alignment in the direction TE to NT\fR
.sp 9p
.RT
.PP
The criterion of a line code violation at\ 13\ bits or less from the framing
bit\ (F) shall apply except if the\ Q\(hychannel (see\ \(sc\ 6.3.3) is
provided, in which case the\ 13\ bit criterion applies in four out of five
frames.
.RT
.sp 1P
.LP
6.3.2.1
\fILoss of frame alignment\fR
.sp 9p
.RT
.PP
The NT may assume loss of frame alignment if a time period
equivalent to at least two\ 48\(hybit frames has elapsed since detecting
consecutive violations according to the\ 13\ bit criterion, if all F\dA\ubits
have been set to binary ZERO. Otherwise, a time period equivalent to at
least three\ 48\(hybit frames shall be allowed before assuming loss of
frame alignment. On detection of loss of frame alignment the NT shall continue
transmitting
towards the TE.
.RT
.sp 1P
.LP
6.3.2.2
\fIFrame alignment\fR
.sp 9p
.RT
.PP
The NT may assume that frame alignment has been regained when three consecutive
pairs of line code violations obeying the\ 13\ bit criterion have
been detected.
.RT
.sp 1P
.LP
6.3.3
\fIMulti\(hyframing\fR
.sp 9p
.RT
.PP
A multi\(hyframe described in the following paragraphs is intended to provide
extra layer\ 1 capacity in the TE\(hyto\(hyNT direction through the use
of an extra channel between the\ TE and\ NT (
Q\(hychannel
). This extra layer\ 1
capacity exists only between the TE and NT, i.e., there is no requirement
for the transmission of signals between NT and ET to carry the information
conveyed by this extra layer\ 1 capacity. The use of the Q\(hychannel is for
further study. However, TEs shall provide for identification of the bit
positions which provide this extra capacity, designated\ Q\ bits. TEs not
using this capability shall provide for setting each
Q\ bit
to a binary ONE. The provision of this capability in NTS is optional.
.PP
The use of the Q bits shall be the same in point\(hyto\(hypoint as in
point\(hyto\(hymultipoint configurations. Future standardization for the use of
Q\ bits is for further study. (There is no inherent collision detection
mechanism provided, and any
collision detection mechanism
that is
required for any application of the\ Q\ bits will be outside the scope of this
Recommendation.)
.RT
.sp 1P
.LP
6.3.3.1
\fIGeneral mechanism\fR
.sp 9p
.RT
.LP
a)
Q bit identification
: The Q bits (TE\(hyto\(hyNT) are
defined to be the bits in the F\dA\ubit position of every fifth frame.
The\ Q\(hybit positions in the TE\(hyto\(hyNT direction are identified
by binary
inversions of the F\dA\u/N\ bit pair (F\dA\u\ =\ binary ONE, N\ =\ binary
ZERO) in the NT\(hyto\(hyTE direction. The provision of the capability
in NTs is optional. The
provision for identification of the Q\(hybit positions
in the NT\(hyto\(hyTE direction permits all TEs to synchronize transmission
in Q\(hybit positions\ \(em\ thereby avoiding interference of F\dA\u\(hybits
from one TE with the
Q\(hybits of a second TE in passive bus configurations.
.LP
b)
Multi\(hyframe identification
: A multi\(hyframe, which
provides for structuring the Q\ bits in groups of four (Q1\ \(em\ Q4),
is established by setting the M\ bit, in position\ 26 of the NT\(hyto\(hyTE
frame, to binary ONE in
every twentieth frame. This structure provides for 4\(hybit characters
in a single channel, TE\(hyto\(hyNT. The provision of the capability in
NTs is optional.
.sp 1P
.LP
6.3.3.2
\fIQ\(hybit position identification algorithm\fR
.sp 9p
.RT
.PP
The Q\(hybit position identification algorithm is illustrated in
Table\ 7/I.430. Two examples of how such an identification algorithm can be
realized are as follows. The TE Q\(hybit identification algorithm may be simply
the transmission of a Q\ bit in each frame in which a binary ONE is received
in the F\dA\u\(hybit position of the NT\(hyto\(hyTE frame (i.e.,\ echoing
of the received
F\dA\ubits). Alternatively, to minimize the Q\(hybit transmission errors that
could result from errors in the F\dA\ubits of NT\(hyto\(hyTE frames, a TE may
synchronize a
frame counter
to the Q\(hybit rate and transmit Q\ bits in
every fifth frame, i.e., in frames in which F\dA\ubits should be equal to
binary ONE. The F\dA\ubit is present in every frame. Q\ bits would be
transmitted only after counter synchronization to the frame binary ONEs
in the F\dA\ubit positions of the NT\(hyto\(hyTE frames is achieved (and
only if such bits are received). When the counter is not synchronized (not
achieved or lost), a TE which uses such algorithm shall transmit binary
ZEROs in Q\(hybit positions.
The algorithm used by a TE to determine when synchronization is defined
to be achieved or the algorithm used to determine when it is defined to
be lost is
not described in this Recommendation, but it should be noted that the
transmission of multi\(hyframing from an NT is not mandatory.
.bp
.PP
No special Q\(hybit identification is required in the NT because the
maximum round trip delay of NT\(hyto\(hyTE\(hyto\(hyNT is a small fraction
of a frame and, therefore, Q\(hybit identification is inherent in the NT.
.RT
.LP
.sp 2
.ce
\fBH.T. [T7.430]\fR
.ce
TABLE\ 7/I.430
.ce
\fBQ\(hybit position identification and multi\(hyframe structure\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
Frame Number {
NT\(hyto\(hyTE
F
A bit position
} {
TE\(hyto\(hyNT
\fR
F
A bit position
(Notes\ 1 and\ 2)
} NT\(hyto\(hyTE \fR M Bit
_
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
\ 1 ONE Q1 ONE
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
\ 2 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
\ 3 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
\ 4 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
\ 5 ZERO ZERO ZERO
_
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
\ 6 ONE Q2 ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
\ 7 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
\ 8 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
\ 9 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
10 ZERO ZERO ZERO
_
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
11 ONE Q3 Z\o"E\(aa"RO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
12 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
13 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
14 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
15 ZERO ZERO ZERO
_
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
16 ONE Q4 ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
17 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
18 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
19 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
20 ZERO ZERO ZERO
_
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
\ 1 ONE Q1 ONE
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
\ 2 ZERO ZERO ZERO
.T&
cw(54p) | cw(42p) | cw(42p) | cw(42p) .
etc.
.TE
.LP
\fINote\ 1\fR
\ \(em\ If the Q\(hybits are not used by a TE, the Q\(hybits shall be
set to binary ONE.
.LP
\fINote\ 2\fR
\ \(em\ Where multi\(hyframe identification is not provided with a
binary ONE in an appropriate M\ bit, but where Q\(hybit positions are
identified, Q\(hybits\ 1 through 4 are not distinguished.
.nr PS 9
.RT
.ad r
\fBTable 7/I.430 [T7.430], p. \fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
.sp 2
6.3.3.3
\fITE Multi\(hyframe identification\fR
.sp 9p
.RT
.PP
The first frame of the multi\(hyframe is identified by the
M\ bit
equal to a binary ONE. TEs that are not intended to use, nor to provide
for the use of, the Q\(hychannel are not required to identify the
multi\(hyframe. TEs that are intended to use, or to provide for the use of, the
Q\(hychannel shall use the M\ bit equal to a binary ONE to identify the
start of
the multi\(hyframe.
.PP
The algorithm used by a TE to determine when synchronization or loss of
synchronization of the multi\(hyframe is achieved is not described in this
Recommendation, however, it should be noted that the transmission of
multi\(hyframing from an NT is not mandatory.
.bp
.RT
.sp 1P
.LP
6.3.4
\fIS\(hybit channel structuring algorithm\fR
.sp 9p
.RT
.PP
The algorithm for structuring the
S\(hybits
(NT\(hyto\(hyTE frame
bit position\ 37) into an S\(hychannel will use a combination of the F\dA\u\(hybit
inversions and the M\ bit used to structure the Q\(hybit channel as described
in\ \(sc\ 6.3.3. The use of the
S\(hychannel
and its structure are for further study.
.RT
.sp 1P
.LP
6.4
\fIIdle channel code on the B\(hychannels\fR
.sp 9p
.RT
.PP
A TE shall send binary ONEs in any B\(hychannel which is not assigned to it.
.RT
.sp 2P
.LP
\fB7\fR \fBLayer 1 maintenance\fR
.sp 1P
.RT
.PP
The test loopbacks defined for the basic user\(hynetwork interface are
specified in Appendix\ I.
.RT
.LP
.rs
.sp 43P
.sp 2P
.LP
\fBMONTAGE : \(sc 8 SUR LE RESTE DE CETTE PAGE\fR
.sp 1P
.RT
.LP
.bp