home
***
CD-ROM
|
disk
|
FTP
|
other
***
search
/
InfoMagic Standards 1994 January
/
InfoMagic Standards - January 1994.iso
/
ccitt
/
1988
/
troff
/
4_1_09.tro
< prev
next >
Wrap
Text File
|
1991-12-13
|
142KB
|
5,166 lines
.rs
.\" Troff code generated by TPS Convert from ITU Original Files
.\" Not Copyright ( c) 1991
.\"
.\" Assumes tbl, eqn, MS macros, and lots of luck.
.TA 1c 2c 3c 4c 5c 6c 7c 8c
.ds CH
.ds CF
.EQ
delim @@
.EN
.nr LL 40.5P
.nr ll 40.5P
.nr HM 3P
.nr FM 6P
.nr PO 4P
.nr PD 9p
.po 4P
.rs
\v | 5i'
.LP
\fBMONTAGE: FIN DE LA RECOMMANDATION M.460 EN T\* | TE DE CETTE PAGE\fR
.sp 2P
.LP
\v'15P'
\fBRecommendation\ M.470\fR
.RT
.sp 2P
.ce 1000
\fBSETTING\ UP\ AND\ LINING\ UP\ ANALOGUE\ CHANNELS\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.470''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.470 %'
.ce 0
.sp 1P
.ce 1000
\fBFOR\ INTERNATIONAL\ TELECOMMUNICATION\ SERVICES\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBCheck of channel\(hytranslating equipment\fR
.sp 1P
.RT
.PP
The translating equipment, before it is connected to the ends of
the link, must be checked and adjusted to ensure that it meets CCITT
Recommendations and the other relevant specifications. The check should
include a general visual inspection and vibration tests, if applicable.
This is of
particular importance if the equipment has remained unused since acceptance
tests were carried out after installation.
.RT
.sp 2P
.LP
\fB2\fR \fBSetting up and lining up the analogue channels\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
\fIMeasurement and \fR \fIadjustment of levels\fR
.sp 9p
.RT
.LP
.PP
After the group link has been set up, and the channel\(hytranslating equipment
at each end of the group link has been connected and checked, the
channels are adjusted as follows.
.PP
An 1020\ Hz test
.FS
For further information about the choice
of the test signal frequency, refer to Recommendation\ O.6\ [1].
.FE
signal is sent over each channel in
turn at a level of \(em10\ dBm0. At the transmitting end, the channel\(hytranslating
equipment is adjusted so that the sideband level on each channel at its
output is as near to nominal as possible. At the receiving end, the
channel\(hytranslating equipment should then be adjusted to bring the received
level on each channel as near as possible to its nominal value.
.RT
.sp 1P
.LP
2.2
\fIChecking the \fR \fIanalogue channel performance\fR
.sp 9p
.RT
.PP
Channel performance measurements are only required when the need is indicated
during circuit line\(hyup. On such occasions the parameters to be
checked will depend on the particular difficulty experienced during circuit
line\(hyup.
.RT
.sp 2P
.LP
\fB3\fR \fBCheck level of line signalling\fR
.sp 1P
.RT
.PP
In the case of groups which are intended to be used for telephone circuits
employing Signalling System\ R2, the checks of signalling level
stipulated in the Specifications of Signalling System\ R2 should be made\ [2].
.PP
For other signalling systems, the check of signalling level should be carried
out at the circuit line\(hyup stage (see Recommendation\ M.580, \(sc\ 8).
.RT
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fI1020 Hz reference test frequency\fR , Vol.\ IV,
Rec.\ O.6.
.LP
[2]
CCITT Recommendations \fISpecifications of Signalling System R2\fR ,
Vol.\ VI, Recs.\ Q.400 to\ Q.490.
.bp
.sp 2P
.LP
\fBRecommendation\ M.475\fR
.RT
.sp 2P
.ce 1000
\fBSETTING\ UP\ AND\ LINING\ UP\ MIXED\ ANALOGUE/DIGITAL\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.475''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.475 %'
.ce 0
.sp 1P
.ce 1000
\fBCHANNELS\ FOR\ INTERNATIONAL\ TELECOMMUNICATION\ SERVICES\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBCheck of FDM multiplex or transmultiplexer equipment\fR
.sp 1P
.RT
.PP
The FDM multiplex or transmultiplexer equipment, before it is
connected to a group or supergroup link, must be checked to ensure that it
meets CCITT Recommendations and the other relevant specifications. The check
should include a general visual inspection and vibration tests, if applicable.
This is of particular importance if the equipment has remained unused since
acceptance tests were carried out after installation.
.RT
.sp 2P
.LP
\fB2\fR \fBSetting up and lining up \fR \fBmixed analogue/digital\fR
\fBchannels\fR
.sp 1P
.RT
.PP
The definition of a mixed analogue/digital channel is given in
Recommendation\ M.300. When these channels are used for international telephone
.PP
circuits, the required circuit transmission loss will in many cases be
established through the use of variable loss pads in the transmultiplexer.
For these mixed analogue/digital channel applications, Administrations
may, through bilateral agreement, defer the separate
channel line\(hyup
procedures
contained in this Recommendation, and perform, instead, the appropriate
circuit section and circuit line\(hyup procedures of Recommendation\ M.580.
.PP
As a prerequisite to setting up and lining up channels using the
procedures in this Recommendation, the involved group and supergroup links
shall have been set up and lined up in accordance with
Recommendation\ M.460.
.RT
.sp 1P
.LP
2.1
\fIMeasurement and\fR
\fIadjustment of levels\fR
.sp 9p
.RT
.PP
Depending upon the type of test equipment used, and the access
features of the transmultiplexer, the following procedures may require
taking an entire
transmultiplexer
out of service while each channel is being lined up. Careful consideration
should be given to procedures for removing
transmultiplexers from service, and for restoring them to service, especially
where the group links which terminate on the transmultiplexer are not
.PP
co\(hyterminous, or where international leased circuits are provided on
transmultiplexers.
.RT
.sp 1P
.LP
2.1.1
\fITransmultiplexers at each end of the group or supergroup link\fR
.sp 9p
.RT
.PP
For further information about the choice of the test signal
frequency, refer to Recommendation\ O.6\ [1].
.FE
\fINote\fR \ \(em\ These configurations are shown in a) and b) of
Figure\ 1/M.475.
.PP
After the group or supergroup links have been set up, and the
transmultiplexing equipments at the ends of the group or supergroup links
have been checked and connected, the channels are adjusted as follows.
.PP
At the transmitting end, a bit sequence corresponding to 1020 Hz
test tone at a level of \(em10\ dBm0 is applied to the 64\ kbit/s time slot
appearance of each channel in turn, at the digital path access point associated
with the input to the transmultiplexer, using appropriate digital test
equipment. At the receiving end, the 64\ kbit/s time slot appearance of each
channel is monitored in turn at the digital path access point associated
with the output of the transmultiplexer, using appropriate digital test
equipment, and each channel is adjusted as near as possible to its nominal
level.
.RT
.sp 1P
.LP
2.1.2
\fI24\(hychannel transmultiplexer at one end of the group\fR
\fIlinks, with channel translating equipment at the other end\fR
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ This configuration is shown in c) of Figure 1/M.475.
.PP
After the group links have been set up, and the transmultiplexing
and channel translating equipments at the ends of the group links have been
checked and connected, the channels are adjusted as follows.
.PP
Transmitting from the channel translating equipment towards the
transmultiplexer, an 1020\ Hz
test signal is sent over each channel in
turn at a level of \(em10\ dBm0. The channel translating equipment is adjusted
so that the sideband level on each channel is as near to the nominal level
as
possible. At the receiving end, the 64\ kbit/s time slot corresponding
to each channel is monitored in turn at the digital path access point associated
with the output of the transmultiplexer, and each channel is adjusted to
obtain the bit sequence corresponding to the nominal level of the received
test
signal.
.bp
.RT
.LP
.rs
.sp 47P
.ad r
\fBFigure 1/M.475, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.PP
Transmitting from the transmultiplexer towards the channel translating
equipments, a bit sequence corresponding to 1020\ Hz
test tone at a
level of \(em10\ dBm0 is applied to the 64\ kbit/s time slot of each
channel in turn, at the digital path access point associated with the digital
input to the transmultiplexer, using appropriate digital test equipment.
At the receiving end, the channel translating equipment should then be
adjusted to
bring the received level on each channel as near as possible to its nominal
value.
.RT
.sp 1P
.LP
2.1.3
\fI60\(hychannel transmultiplexer at one end of a supergroup link,\fR
\fIwith group and channel translating equipments at the other end\fR
.sp 9p
.RT
.PP
\fINote\fR \ \(em\ This configuration is shown in d) of Figure 1/M.475.
.PP
After the supergroup link and group links have been set up, and the
transmultiplexing, group translating, and channel translating equipments
at the ends of the supergroup link and group links have been checked and
connected,
the channels are adjusted by the following procedures in \(sc\ 2.1.2 above.
.RT
.sp 2P
.LP
\fB3\fR \fBCheck level of line signalling\fR
.sp 1P
.RT
.PP
In the case of groups which are intended to be used for telephone circuits
employing Signalling System\ R2, the checks of signalling level
stipulated in the Specifications of Signalling System\ R2 should be made\ [2].
.PP
For other signalling systems, the check of signalling level should be carried
out at the circuit line\(hyup stage (see the Recommendation\ M.580).
.RT
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fI1020 Hz reference test frequency\fR , Vol. IV,
Rec.\ O.6
.LP
[2]
CCITT Recommendations \fISpecifications of Signalling System R2\fR ,
Vol.\ VI, Recs.\ Q.400 to Q.490.
.LP
.IP
\fB2.4\ Planned\ outages and restoration of transmission systems\fR
.sp 1P
.RT
.sp 2P
.LP
\fBRecommendation\ M.490\fR
.RT
.sp 2P
.ce 1000
\fBEXCHANGE\ OF\ INFORMATION\ FOR\ PLANNED\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.490''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.490 %'
.ce 0
.sp 1P
.ce 1000
\fBOUTAGES\ OF\ TRANSMISSION\ SYSTEMS\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral\fR
.sp 1P
.RT
.PP
\fIPlanned\fR outages
of transmission systems are required to allow planned work to be done with
the minimum impairment to the service
concerned. All tests, measurements, rearrangements, etc., which are not
attributed directly to a failure \(em\ and are known in advance\ \(em are
considered to be \fIplanned work\fR . Such work will include installation
of new equipment,
routine maintenance, work on power supply equipment and in some cases,
work for the clearance of faults which at first could only be remedied
provisionally
(mainly cable faults).
.PP
In the event of planned work which results in the complete or partial interruption
in a transmission system, efforts are at first made to reroute the telecommunication
traffic as required. If special restoration plans exist for cases of faults,
these plans can also be used in the event of planned outages. Should rerouting
be impossible, planned work is generally carried out during
periods of light traffic, e.g. at night. To allow appropriate measures to be
taken, all stations affected by the planned outage must be informed in good
time.
.bp
.RT
.sp 2P
.LP
\fB2\fR \fBPlanned outages of international groups, supergroups, etc.\fR
.sp 1P
.RT
.PP
When an Administration plans the outage of a transmission system
carrying international group/supergroup, etc. links, it should inform all
other Administrations in whose territories the links concerned terminate.
This
information should be given by telex at least three working days in
advance.
.FS
The time limit of three working days is not intended to affect
other agreements in special cases, e.g.\ a notification time of two weeks in
planned outages of submarine cable systems.
.FE
An example is given in
Figure\ 1/M.490. There are cases in which more than three days are necessary,
such as those involving extensive rearrangements. If, in exceptional cases,
a three\(hyday notice cannot be given, advice should be given by telephone
so as to ensure that the Administrations concerned still have sufficient
time to take
the appropriate steps. Planned outages should not be carried out if notice
cannot be given and received at least 24\ hours in advance.
.PP
In practice, Administrations have entrusted different entities,
i.e. either their international centres or their technical services with the
exchange of information for planned outages. Therefore, it is essential that
each Administration states clearly to whom reports on outages are to be
sent
.FS
Normally such information is exchanged between the System Availability
Information Points (see Recommendation\ M.721).
.FE
. In any case, the technical service of an Administration should be aware
of the outages planned in its own country, and try to reduce their impact
on international services to a minimum. Passing on of the information within
the area of an Administration, e.g. to the control stations for leased
and special circuits, or to the users of leased
circuits, is done according to the national practice.
.RT
.sp 2P
.LP
\fB3\fR \fBPlanned outages of national transmission systems, which affect
international leased and special circuits\fR
.sp 1P
.RT
.PP
In the international centres, international leased and special
circuits are frequently through\(hyconnected in the voice\(hyfrequency band and
routed to the destination via national group links. An outage of these group
links leads to a break in the international circuit. In these cases, informing
the circuit control station and the users is of particular importance in
order to avoid unnecessary fault location in the other country.
.PP
If an outage is planned for a national system within the area of the Administration
being entrusted with the terminal sub\(hycontrol function for a
circuit, the circuit control station should be informed direct or via the
two transmission maintenance points (international line) (see
Recommendation\ M.1014\ [1] or via the technical service so as to enable the
control station to inform the user in good time. In addition, it may be
advisable that the terminal
.PP
sub\(hycontrol station informs the user at its end of the circuit of the
planned outage, since an exchange of information between the users at both
ends of the circuit is not always possible. Figure\ 2/M.490 illustrates
the possible flow of information for this case.
.PP
A similar procedure should be applied if a planned outage of a
national system in a transit country affects an international leased or
special circuit.
.PP
If an outage is planned for a national system within the area of an
Administration having control functions for a circuit, it is recommended
that the sub\(hycontrol station be advised in order to avoid unnecessary
queries in the event of a fault report being submitted by the user in the
distant country
concerned. The transmission maintenance point (international line) in its
own country should be informed in any case.
.RT
.LP
.sp 14
.bp
.LP
.rs
.sp 33P
.ad r
\fBFigure 1/M.490 [T1.490], p. 2\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 14P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.LP
.rs
.sp 37P
.ad r
\fBFigure 2/M.490, p. 3\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fBReference\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fITransmission maintenance point international\fR
\fIline (TMP\(hyIL)\fR , Vol.\ IV, Rec.\ M.1014.
.LP
.rs
.sp 9P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.sp 2P
.LP
\fBRecommendation\ M.495\fR
.RT
.sp 2P
.ce 1000
\fBTRANSMISSION\ RESTORATION\ AND\ TRANSMISSION\ ROUTE\ DIVERSITY:\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.495''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.495 %'
.ce 0
.sp 1P
.ce 1000
\fBTERMINOLOGY\ AND\ GENERAL\ PRINCIPLES\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBPurpose of transmission restoration and transmission route\fR
\fBdiversity\fR
.sp 1P
.RT
.PP
The purpose of transmission restoration and transmission route
diversity is to protect the continuity and quality of international
telecommunication services by minimizing the effects of potential effects
of a transmission failure.
.PP
This Recommendation applies to both analogue and digital
transmission.
.PP
\fINote\fR \ \(em\ This Recommendation may also apply in the case of hazardous
conditions.
.RT
.sp 2P
.LP
\fB2\fR \fBCauses of transmission failures\fR
.sp 1P
.RT
.PP
The causes of transmission failures can be divided into three major categories:
.RT
.LP
\(em
equipment failure: this can be reduced by improving equipment reliability;
.LP
\(em
outages due to the operating organization. For example,
maintenance work or human errors;
.LP
\(em
external causes which are very difficult to prevent and for which specific
protection might be needed. For example weather conditions or
excavation work.
.PP
In this Recommendation, failures or faults that are referred to
may be either total or partial failures or faults. The relevant terminology
concerning failures and faults can be found in Supplement\ No.\ 6\ [1].
.sp 2P
.LP
\fB3\fR \fBDefinitions concerning transmission restoration and transmission\fR
\fBroute diversity\fR
.sp 1P
.RT
.PP
The purpose of this terminology is to define a vocabulary which can be
used in connection with transmission restoration and transmission route
diversity.
.PP
\fINote\fR \ \(em\ In this terminology, the term \*Qlink\*U is used as
a generic
term for digital section, digital path, group link or section, supergroup
link or section, mastergroup link or section, supermastergroup link or
section, line section, section and line link.
.RT
.sp 2P
.LP
3.1
\fIBasic concepts\fR
.sp 1P
.RT
.sp 1P
.LP
3.1.1
\fBtransmission restoration\fR
.sp 9p
.RT
.PP
The different actions taken in order to restore the transmission of a signal
affected by a transmission fault.
.RT
.sp 1P
.LP
3.1.2
\fBtransmission restoration function\fR
.sp 9p
.RT
.PP
The ability to perform under stated conditions and within given
time constraints the transmission restoration.
.PP
\fINote\ 1\fR \ \(em\ This function is aimed at increasing the transmission
availability; it can provide transmission link supervision and control, the
sending and receiving of control and check signals, and the changeover from
normal to an alternative link, if necessary by assembling links.
.PP
\fINote\ 2\fR \ \(em\ This function can allow the restoration of failed
transmission systems, links, groups, digital blocks, equipment,\ etc.,
as well as the restoration for maintenance purposes such as planned outages,
or to
remedy conditions that affect transmission such as fading.
.PP
\fINote\ 3\fR \ \(em\ The transmission restoration function can be implemented
by equipment that is dedicated to it, or by equipment that has other functions,
such as, for example, automatic digital distribution frames.
.bp
.RT
.sp 1P
.LP
3.1.3
\fBtransmission restoration function: direct transmission\fR
\fBrestoration (protection link switching)\fR
.sp 9p
.RT
.PP
Direct transmission restoration is that category of transmission restoration
function in which one transmission link between two stations is
substituted for another between those two stations.
.PP
\fINote\fR \ \(em\ This reflects a configuration in which M links proctect N
links, or in which N+M links give redundancy to a relation requiring N\
links, with the extremities of all links in the same locations. It is recommended
to use the expression N+M direct transmission restoration to designate
such a
configuration. See Figure 1/M.495.
.RT
.LP
.rs
.sp 10P
.ad r
\fBFigure 1/M.495, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.1.4
\fBtransmission restoration function: automatic or semi\(hyautomatic\fR
\fBtransmission rerouting (protection network switching)\fR
.sp 9p
.RT
.PP
Automatic or semi\(hyautomatic transmission rerouting is that
category of transmission restoration function in which transmission links
are assembled together and substituted for another link.
.PP
\fINote\fR \ \(em\ This reflects a configuration in which a certain number of
links form a restoration network and protect normal links. Within a given
transmission station, or for a given switching equipment, M\ links protect
N\ links. It is recommended to use the expression N+M automatic transmission
rerouting to designate such a configuration.
.PP
Figure 2/M.495 shows un example. In Station A, M restoration links can
be used for restoration of N\ normal. A link between\ A and\ B can be restored,
for example, directly or via\ C.
.RT
.LP
.rs
.sp 17P
.ad r
\fBFigure 2/M.495, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.1.5
\fBtransmission restoration function: 1+1 restoration\fR
.sp 9p
.RT
.PP
1+1 restoration is that category of transmission restoration
function in which one transmission link is substituted for another associated
link, generally on another transmission route. See Figure\ 3/M.495.
.RT
.LP
.rs
.sp 9P
.ad r
\fBFigure 3/M.495, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.1.6
\fBtransmission restoration function: manual transmission\fR
\fBrerouting\fR
.sp 9p
.RT
.PP
Manual transmission rerouting is that category of transmission
restoration function in which one transmission link is replaced manually by
another when a complete or partial transmission route failure has occurred
or when the normal route restoration link is not available due to a previous
or
simultaneous interruption, or when there is no such restoration link provided.
.PP
\fINote\fR \ \(em\ Such rerouting is normally effected using plugs and
cords.
.RT
.sp 1P
.LP
3.1.7
\fBtransmission restoration control function\fR
.sp 9p
.RT
.PP
This is the function which decides whether restoration is necessary on
the basis of information from the link supervision system or link alarms.
.PP
\fINote\fR \ \(em\ The control function might be included in a specific
equipment, or in the transmission restoration equipment itself, or within a
restoration control centre. Control decisions can also be taken by people
in, for example, a control centre.
.RT
.sp 2P
.LP
3.2
\fISystems and equipment\fR
.sp 1P
.RT
.sp 1P
.LP
3.2.1
\fBtransmission restoration system\fR
.sp 9p
.RT
.PP
A system that can be used to implement the transmission
restoration function. An example is shown in Figure\ 4/M.495.
.RT
.sp 1P
.LP
3.2.2
\fBtransmission restoration equipment\fR
.sp 9p
.RT
.PP
The part of the transmission restoration system that switches the transmission
from the normal link to a restoration link.
.RT
.sp 1P
.LP
3.2.3
\fBnormal transmission link/equipment; normal digital block,\fR
\fBgroup, supergroup, etc.\fR
.sp 9p
.RT
.PP
A transmission link/equipment or a digital block, group,
supergroup,\ etc., which is used for transmission under normal operating
conditions.
.RT
.sp 1P
.LP
3.2.4
\fBrestoration link/equipment\fR
.sp 9p
.RT
.PP
A transmission link/equipment which is used for transmission when the normal
link/equipment is not available.
.PP
\fINote\ 1\fR \ \(em\ A restoration link or equipment is generally idle under
normal operating conditions, but might be used under these conditions by
low\(hypriority traffic for which a lower degree of service availability is
accepted.
.PP
\fINote\ 2\fR \ \(em\ Note 1 may not apply to 1+1 type restoration system
where both links are carrying the traffic.
.bp
.RT
.sp 1P
.LP
3.2.5
\fBrestoration network\fR
.sp 9p
.RT
.PP
The network formed by all restoration links.
.RT
.LP
.rs
.sp 34P
.ad r
\fBFigure 4/M.495, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
3.3
\fIControl\fR (see also Figure 5/M.495)
.sp 1P
.RT
.sp 1P
.LP
3.3.1
\fBcontrol equipment\fR
.sp 9p
.RT
.PP
An equipment that is used to implement the transmission
restoration control function.
.RT
.sp 1P
.LP
3.3.2
\fBrestoration control centre\fR
.sp 9p
.RT
.PP
A centre supervising all or part of normal and restoration
transmission systems.
.PP
\fINote\fR \ \(em\ A restoration control centre can be included within
a control centre which is not dedicated to restoration.
.RT
.sp 1P
.LP
3.3.3
\fBcontrolled station\fR
.sp 9p
.RT
.PP
The station that has its systems, links and other maintenance
elements supervised, where the information and commands for switching are
sent to and received from, the control centre, and where the switching
is
effected.
.bp
.RT
.sp 1P
.LP
3.3.4
\fBrestoration unit\fR
.sp 9p
.RT
.PP
All normal and restoration links and associated switching
equipment capable of being controlled from a particular control centre.
.PP
\fINote\fR \ \(em\ Some networks areas may be controlled from more than one
control centre.
.RT
.sp 1P
.LP
3.3.5
\fBcontrol circuit\fR
.sp 9p
.RT
.PP
A circuit used for the transmission of restoration control
information.
.RT
.LP
.rs
.sp 17P
.ad r
\fBFigure 5/M.495, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
3.4
\fITime intervals associated with transmission restoration processes\fR
.sp 9p
.RT
.PP
The following time intervals are intended to describe the
different time components between the failure of a signal and its restoration.
These time intervals can be used to characterize those transmission restoration
systems, equipment\ etc. See also figure\ 6/M.495.
.RT
.LP
.rs
.sp 19P
.ad r
\fBFigure 6/M.495, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
3.4.1
\fBdetection time, T\fR\(da\fB1\fR
.sp 9p
.RT
.PP
Time interval between a potential failure of transmission and the recognition
of that potential failure.
.RT
.sp 1P
.LP
3.4.2
\fBwaiting time, T\fR\(da\fB2\fR
.sp 9p
.RT
.PP
Time interval after the recognition of a potential failure and its confirmation
as a fault requiring restoration.
.RT
.sp 1P
.LP
3.4.3
\fBrestoration procedure time, T\fR\(da\fB3\fR
.sp 9p
.RT
.PP
Time interval between the confirmation of a fault and completion of the
processing and transmission of the control signals required to effect
restoration.
.RT
.sp 1P
.LP
3.4.4
\fBrestoration transfer time, T\fR\(da\fB4\fR
.sp 9p
.RT
.PP
Time interval between completion of the processing and
transmission of the control signals required to effect restoration and the
completion of transmission restoration operations.
.RT
.sp 1P
.LP
3.4.5
\fBrecovery time, T\fR\(da\fB5\fR
.sp 9p
.RT
.PP
Time interval between the completion of transmission restoration operations
and the full restoration of failed transmission.
.PP
\fINote\fR \ \(em\ This may include the verification of switching operations,
re\(hysynchronization of digital transmission,\ etc.
.RT
.sp 1P
.LP
3.4.6
\fBconfirmation time, T\fR\(da\fBc\fR
.sp 9p
.RT
.PP
The time from the occurrence of the potencial failure to the
instant when the fault is confirmed as requiring a restoration:
T\dc\u\ =\ T\d1\u\ +\ T\d2\u.
.RT
.sp 1P
.LP
3.4.7
\fBtransfer time, T\fR\(da\fBt\fR
.sp 9p
.RT
.PP
The time interval after the confirmation that a fault requires a restoration
to the completion of the transmission restoration operation;
T\dt\u\ =\ T\d3\u\ +\ T\d4\u.
.RT
.sp 1P
.LP
3.4.8
\fBrestoration time, T\fR\(da\fBr\fR
.sp 9p
.RT
.PP
The time from the occurrence of the failure to the restoration of the faulty
transmission:
T\dr\u\ =\ T\d1\u\ +\ T\d2\u\ +\ T\d3\u\ +\ T\d4\u\ +\ T\d5\u= confirmation
time +
transfer time +\ T\d5\u.
.PP
\fINote\fR \ \(em\ An apparent fault might be detected by an equipment
and not confirmed after the confirmation operations. In this case, only
times T\d1\uand T\d2\uare relevant.
.RT
.sp 2P
.LP
3.5
\fISoftware related terms\fR
.sp 1P
.RT
.sp 1P
.LP
3.5.1
\fBnetwork image\fR
.sp 9p
.RT
.PP
Software description of the transmission network to be
protected.
.RT
.sp 1P
.LP
3.5.2
\fBfault definition program\fR
.sp 9p
.RT
.PP
Program which collects fault information and defines faulty
transmission links.
.RT
.sp 1P
.LP
3.5.3
\fBrestoration algorithm\fR
.sp 9p
.RT
.PP
Method for forming restoration links for faulty normal
transmission links.
.RT
.sp 1P
.LP
3.5.4
\fBrestoration control program\fR
.sp 9p
.RT
.PP
A decision making program which controls restoration
processes.
.bp
.RT
.sp 2P
.LP
3.6
\fIRoute diversity\fR
.sp 1P
.RT
.sp 1P
.LP
3.6.1
\fBtransmission route\fR
.sp 9p
.RT
.PP
A transmission facility on a specific medium used by a certain
number of transmission systems between two stations.
.PP
\fINote\ 1\fR \ \(em\ For example, one cable between two stations could
be regarded as one transmission route (whatever the number of systems using
this cable
might be) and a radio system between these two points could be regarded
as an other route.
.PP
\fINote\ 2\fR \ \(em\ This definition represents a physical route; this is
different from the term \*Qroute\*U which is defined in the
Recommendations\ E.600\ [2], Q.9\ [3] and\ Z.341\ [4], which represents
a logical
route.
.RT
.sp 1P
.LP
3.6.2
\fBtransmission route diversity\fR
.sp 9p
.RT
.PP
The provision of at least two links between two nodes in a
transmission network which are routed over different transmission routes.
.PP
\fINote\fR \ \(em\ In case of a failure of one link, transmission route
diversity allows some traffic between the two nodes still to be carried over
the remaining link(s).
.RT
.LP
\fB4\fR \fBPrinciples of\fR
\fBtransmission restoration and transmission\fR
\fBroute diversity\fR
.sp 1P
.RT
.sp 2P
.LP
4.1
\fIGeneral principles\fR
.sp 1P
.RT
.PP
4.1.1
In case of a fault of an international transmission system,
complete and fast transmission restoration is a maintenance objective.
Line and terminal equipment allocated for transmission restoration should
be left
available to the extent that the objective can be achieved. This equipment
may sometimes be used for other purposes as required, e.g.,\ planned outages.
.sp 9p
.RT
.PP
4.1.2
When planning new routes or changes to existing routes, account
should be taken of the requirements of restoration.
.PP
4.1.3
The responsibility for restoration should be based on the
following principles in the case of an interruption due to a fault or to a
planned outage of a transmission link:
.LP
a)
when the fault of an international transmission link takes place on a
national section, restoration is solely the affair of the
Administration involved;
.LP
b)
when a fault takes place on an international section of an international
route, restoration is the affair of the Administrations of the
two countries directly involved, even if Administrations of other countries
are concerned;
.LP
c)
in the case of a satellite fault, the responsibility
to restore the satellite capability rests with the designated satellite
system manager;
.LP
d)
restoration should be effected in the transmission network at the highest
order of link permitted by the network (group link, supergroup link,\ etc.)
taking into account the service which is carried;
.LP
e)
it would be desirable to arrive, if possible, at complete
restoration based upon bilateral and/or multilateral agreements. Special
consideration is necessary when, in practical cases, complete restoration
cannot be achieved. When complete restoration is not possible the links
to be restored should contain those circuits that satisfy the special needs
of the
Administrations involved to the extent possible. Sufficient restoration
capacity should therefore be provided to reflect the special interests
of each Administration involved. Certain services might be considered as
priority
services by bilateral agreements; in this case, they should be grouped on
groups or digital blocks that are restored in priority;
.LP
f
)
in the case where it is not possible to restore all
circuits through the procedures envisaged under\ a), b), and\ c), each
terminal Administration should make the necessary agreements to use all
available routes lending themselves to restoration.
.bp
.sp 1P
.LP
4.2
\fITransmission restoration systems\fR
.sp 9p
.RT
.PP
The following points regarding transmission restoration systems
should be noted:
.RT
.LP
a)
in the case when a transmission restoration network exists, it might
be used under normal operating conditions for preemptible traffic.
However, the restoration time might be a little longer when low priority
traffic has to be interrupted before the restoration;
.LP
b)
transmission restoration systems might be used for specific maintenance
purposes such as planned outages. In this case, a planned
restoration should be effected in such a way that the resulting impact on
tranmission quality and availability is minimized;
.LP
c)
certain normal transmission links may have a priority
restoration, with preemption on restoration links. On these links should be
routed groups and digital blocks bearing services that are considered having
priority;
.LP
d)
in general, when the normal transmission link can be used
again, transmission is switched back from the restoration link. This
switch\(hyback can be made manually, semi\(hyautomatically or automatically; it
should be made in such a way that the resulting impact on transmission
quality and availability is minimized;
.LP
e)
in certain cases, restoration of transmission might be
effected separately for the receive and transmit directions;
.LP
f
)
in case of automatic or semi\(hyautomatic restoration
systems,
there should be a possibility of manual action for a forced restoration
or an inhibition. This action has to be possible semi\(hyautomatically
for automatic
restoration systems;
.LP
g)
transmission restoration systems should be built in such a way that a
fault of one of its components or a maintenance action on it will
result, in most cases, in minimal impact on normal transmission quality and
availability.
.sp 1P
.LP
4.3
\fITransmission route diversity\fR
.sp 9p
.RT
.PP
Transmission route diversity is a way of protecting circuits groups (a
number of circuits with the same terminal points) against the effects of
transmission failures. Circuit groups are divided into smaller groups which
are carried on different transmission routes. In this way, a transmission
faults of one transmission route does not completely interrupt the service.
.PP
For example, 60 public circuits between two exchanges can be divided into
2 groups of 30\ circuits routed on cable and radio link. See
Figure\ 7/M.495.
.RT
.LP
.rs
.sp 13P
.ad r
\fBFigure 7/M.495, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
4.4
\fIRestoration times\fR
.sp 1P
.RT
.PP
4.4.1
It is useful to consider the restoration system in terms of the
component time intervals involved. Some of these have been identified in the
above terminology. These time intervals vary depending on whether the
transmission system is analogue or digital. In the case of digital, the bit
rate is also a factor.
.bp
.sp 9p
.RT
.PP
4.4.2
It might be necessary, when specifying restoration times, and
especially the confirmation time, to examine the different transmission
restoration systems that might be used at the same time on a given link: for
example, a 1+1 restoration system with its normal link beared by a
transmission system protected by an N+1 direct transmission restoration
system.
.PP
4.4.3
The aim for restoration time performance objective will come from service
interruption objectives which were currently under study by CCITT.
.PP
There might be different aims for various types of failure and of restoration
type: single transmission system or complete transmission route
failure; automatic, semi\(hyautomatic or manual restoration,\ etc.
.sp 1P
.LP
4.5
\fIRestoration criteria\fR
.sp 9p
.RT
.PP
The criteria used to decide if a restoration action is necessary
can be based upon transmission fault and also occurrence of bad quality
(signal\(hyto\(hynoise ratio for analogue transmission, bit error ratio,
thresholds of Recommendation\ G.821\ [5] for digital transmission,\ etc.).
.RT
.sp 2P
.LP
\fB5\fR \fBMethods of transmission restoration\fR
.sp 1P
.RT
.sp 1P
.LP
5.1
\fIGeneral\fR
.sp 9p
.RT
.PP
The links provided for transmission restoration can be used in the event
of both faults and planned outages. Methods for restoration will
necessarily vary according to the particular system and circumstances involved.
They will include transmission restoration and physical repair using manual,
semi\(hyautomatic or fully automatic methods. In order to choose the restoration
method, it is appropriate for the Administrations involved to take into
account the following elements in a bilateral or multilateral agreement:
.RT
.LP
a)
the level of availability desired;
.LP
b)
the facilities that may be used for restoration;
.LP
c)
the economics related to the particular system being
considered;
.LP
d)
the compatibility of transmission equipment at appropriate locations
(for example analogue/digital, satellite/coaxial\ etc.).
.sp 1P
.LP
5.2
\fIAutomatic restoration\fR
.sp 9p
.RT
.PP
Automatic restoration is possible with the use of automatic
restoration systems, which can be of three main types:
.RT
.LP
\(em
1+1 transmission restoration;
.LP
\(em
direct transmission restoration (protection link switching);
.LP
\(em
automatic transmission rerouting (protection network
switching).
.PP
The functional organization of these restoration systems is
described within Recommendation\ M.496.
.sp 1P
.LP
5.3
\fISemi\(hyautomatic restoration\fR
.sp 9p
.RT
.PP
Specific equipment and transmission restoration systems are
introduced in order to allow automatic restoration. As any interruption of
service is undesirable, especially in the case of planned outages, this
equipment should generally allow the remote manual activation and control of
automatic transmission rerouting systems in order to change from the normal
route to a previously set\(hyup and tested restoration route.
.RT
.sp 1P
.LP
5.4
\fIManual restoration\fR
.sp 9p
.RT
.PP
The complexity of the evolving international transmission network demands
flexibility in any transmission restoration arrangement. In general,
transmission restoration can be achieved by manual switching, for example on
analogue or digital distribution frames. In this case a distribution frame
is necessary. The links used for transmission restoration are arranged
in a
network configuration with particular restoration requirements being met by
using such links either singly or connected in tandem. This arrangement is
flexible and maximizes the use of international restoration links which are
expensive to provide and therefore limited in number.
.bp
.RT
.sp 2P
.LP
\fB6\fR \fBConsiderations involved in planning\fR
\fBtransmission restoration\fR \fBsystems\fR
.sp 1P
.RT
.sp 1P
.LP
6.1
\fIParameters to be taken into account:\fR
.sp 9p
.RT
.PP
Restoration arrangements for transmission systems may be applied at any
level in the multiplex hierarchy that is bilaterally or multilaterally
agreed upon. The switching configuration itself may be a 1+1 or more complex
N+M relationship, involving N normal links being protected by M\ restoration
links. When planning a physical restoration system on an international basis
the following considerations, among others, should be taken into account
in the context of the desired availability and the economics involved.
.RT
.LP
a)
availability of restoration capacity, taking into account
the number of restoration and normal links;
.LP
b)
transmission characteristics of the restoration link(s);
.LP
c)
services to be restored and the acceptability of additional delay to
confirm a fault and minimize switching (see \(sc\ 4.4 of this
Recommendation);
.LP
d)
threshold at which fault is to be established (this may be adjustable
in a range) (see \(sc\ 4.5);
.LP
e)
switching level in the multiplex hierarchy and whether any restorative
switching is to be applied at more than one level;
.LP
f
)
manual or automatic switch\(hyback techniques;
.LP
g)
use of telemetry and control system, if required;
.LP
h)
the need of a unidirectional or bidirectional system;
.LP
i)
apportionment to the switches of the maximum degradation of the transmission
characteristics (for example, maximum crosstalk, maximum
unavailability. | | );
.LP
j
)
desirable restoration time (see \(sc\ 4.4 of this
Recommendation);
.LP
k)
changed propagation time resulting from restoration over
another route (this may be particularly important in the case of data
transmission);
.LP
l)
other functions that might be included in restoration
equipment for maintenance purposes.
.sp 1P
.LP
6.2
\fIRestoration network planning\fR
.sp 9p
.RT
.PP
The restoration network should be dimensioned according to the
objectives of the restoration capability for faulty transmission systems or
equipment, as well as for planned outages.
.PP
One example of a method for dimensioning a restoration network
without the help of simulation software is to add systematically a certain
proportion of restoration links to the normal links.
.PP
Another method is to dimension the restoration network for the
restoration of certain priority services in case of a single transmission
route or transmission link fault. A priority protection for specific services
would allow these services to have a better availability. This would allow
the
planning of a smaller and therefore cheaper restoration network that would
be required for a systematic restoration of all transmission routes failures.
The restoration network obtained in such a way would not only cost less
in
investment, but it would also serve to restore non\(hypriority traffic when
restoration links are available.
.RT
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Supplement \fITerms and definitions for quality of service,\fR
\fInetwork performance, dependability and trafficability studies\fR , Fascicle\
II.3, Supplement\ No.\ 6.
.LP
[2]
CCITT Recommendation \fITerms and definitions of teletraffic engineering\fR
, Vol.\ II, Rec.\ E.600.
.LP
[3]
CCITT Recommendation \fIVocabulary of switching and signalling terms\fR ,
Vol.\ VI, Rec.\ Q.9.
.LP
[4]
CCITT Recommendation \fIGlossary of terms\fR , Vol.\ VI, Rec.\ Z.341.
.LP
[5]
CCITT Recommendation \fIError performance of an international digital\fR
\fIconnection forming part of an Integrated Services Digital Network\fR
, Vol.\ III, Rec.\ G.821.
.bp
.sp 2P
.LP
\fBRecommendation\ M.496\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBFUNCTIONAL\ ORGANIZATION\ FOR\ AUTOMATIC\ TRANSMISSION\fR |
\fBRESTORATION\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.496''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.496 %'
.ce 0
.sp 1P
.PP
This Recommendation is a description of the functional
organization for three general types of automatic transmission restoration
systems:
.sp 1P
.RT
.LP
\(em
1+1 transmission restoration;
.LP
\(em
N+M direct transmission restoration (protection link
switching);
.LP
\(em
N+M automatic rerouting (protection network
switching).
.PP
The terminology and general principles of transmission restoration are
described in Recommendation\ M.495. Specifications for equipment of the
1+1 restoration system type can be found in Recommendation\ G.181\ [1].
Specifications for equipment of the N+M direct transmission restoration or
automatic rerouting system type can be found in Recommendation\ G.180\ [2].
.LP
\fB1\fR \fB1+1 transmission restoration\fR
.sp 1P
.RT
.sp 2P
.LP
1.1
\fIPurpose of 1+1 transmission restoration\fR
.sp 1P
.RT
.PP
1.1.1
1\ +\ 1 restoration is used for the restoration of one group or
digital block or link on one restoration link that is dedicated to its
transmission restoration.
.sp 9p
.RT
.PP
1.1.2
This type of restoration is generally reserved for specific
services with a need for a very high availability.
.PP
1.1.3
As this method of restoration is rather expensive (duplication of transmission
links), it is often effected, at the present time, at low
hierarchichal levels (for example, group or primary digital block). This
is a preventive protection, adapted to specific services, whereas restoration
at the highest order group or digital block is a corrective protection
for part of the network.
.PP
Figure 3/M.495 illustrates such a configuration.
.sp 2P
.LP
1.2
\fIMethod of transmission restoration\fR
.sp 1P
.RT
.PP
1.2.1
The transmission signal is sent on the normal link and generally also on
the restoration link at the same time.
.sp 9p
.RT
.PP
1.2.2
In order to ensure the best availability of transmission, it is
recommended to have the restoration link routed on a transmission route
different from the route of the normal link.
.PP
1.2.3
Control equipment or a control function implemented in equipment with other
functions, at both ends of the link, ensures link supervision and
control and detects the occurrence of such conditions that may need a
restoration action. Generally, there is no control circuit in such a
transmission restoration system: control and switching can be done at both
receive ends of the signal.
.PP
When a fault has been detected and confirmed, the switching
equipment receives a command for a switching action.
.PP
1.2.4
If a switchback function is provided, when the normal link becomes
available again for transmission, it is advisable to perform the switchback
at a time when there is the least impact on the traffic concerned. At that
time, a switching command is sent by the control equipment. The switching
equipment
switches back the transmission to the normal link.
.PP
This switching is normally effected in such a way that it has
minimal impact on transmission quality and availability.
.sp 1P
.LP
1.3
\fIRestoration time\fR
.sp 9p
.RT
.PP
Restoration time should be kept as short as possible, in order to have
minimal impact on service availability.
.bp
.RT
.sp 2P
.LP
\fB2\fR \fBN+M direct transmission restoration (protection link\fR
\fBswitching)\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
\fIPurpose of N+M direct transmission restoration\fR
.sp 9p
.RT
.PP
N+M direct transmission restoration systems provide M restoration links
for N normal links. All the links have their terminal equipments located
at the same locations.
.PP
Figure 1/M.495 illustrates such a configuration.
.RT
.sp 2P
.LP
2.2
\fIMethod of transmission restoration\fR
.sp 1P
.RT
.PP
2.2.1
The M restoration links may be routed on the same transmission
route as all, or part, of the N normal link; but preferably, some restoration
links may be routed over a different route, so that a fault of a whole
transmission route allows the restoration of some links.
.sp 9p
.RT
.PP
2.2.2
This type of transmission restoration can be effected at all
hierarchical levels. It is often used at the transmission system level.
.PP
2.2.3
At both ends of the links, control equipment (or a control
function implemented in equipment) ensures link supervision and control, and
detects the occurrence of a failure. The control circuits for this function
might be on a restoration link, or on another link which is not one of the
N\ normal links, or duplicated on at least 2 of the N\ normal links.
.PP
2.2.4
Some of the N normal links might have a higher priority. In this case,
when one of them is in fault, it is restored in priority and can use a
restoration link on a preemptive basis. This means that:
.LP
\(em
in case of a simultaneous fault of several links, and if a
complete restoration is not possible, only the highest priority links are
restored;
.LP
\(em
if all restoration links are in use and if a normal link
having a priority higher than the priority of one of the restored links
has a failure, the lower priority restored link is interrupted so that
the link in
fault can be restored.
.PP
2.2.5
When a restoration action has been detected, confirmed and
accepted (restoration link available or priority link in fault), the switching
equipment receives a command for a switching action. Switching might be
effected at both ends systematically, but it is also possible to switch only
the faulty direction, if necessary.
.PP
2.2.6
In the case of automatic switchback, after the normal link is
available again for a normal transmission, the control equipment sends a
switchback command. In this case, the switching equipment switches back the
signal transmitted from the restoration link to the normal link. This switching
is normally effected in such a way that it has a minimal impact on transmission
quality and availability.
.sp 1P
.LP
2.3
\fIRestoration time\fR
.sp 9p
.RT
.PP
N+M direct transmission restoration is characterized by a
requirement to detect a degraded or faulty normal link and switch to a
restoration link in a time interval that is short enough not to cause
established telephone calls to be released.
.RT
.sp 2P
.LP
2.4
\fIOther considerations\fR
.sp 1P
.RT
.PP
2.4.1
A restoration link might be used, when a restoration is not
needed, for other purposes such as planned outages or non\(hypriority traffic.
In this case, it can be preferable that the N normal links have a preemption
of
the restoration link when they are in fault.
.sp 9p
.RT
.PP
2.4.2
The maximum number N of normal links for one restoration has to be dimensioned
correctly to avoid a too large number of non\(hyrestored faults. When a
large number of links have to be restored, N+M direct transmission
restoration
(with M\ >\ 1) is necessary; in this case\ M restoration links can be used
for the restoration of N\ normal ones.
.PP
2.4.3
The N+M direct transmission restoration is an automatic system,
but it should also allow manual or semi\(hyautomatic (remote manual) actions,
in order to force switching or inhibit restoration.
.bp
.sp 2P
.LP
\fB3\fR \fBN+M automatic rerouting (protection network switching)\fR
.sp 1P
.RT
.sp 1P
.LP
3.1
\fIPurpose of N+M automatic rerouting\fR
.sp 9p
.RT
.PP
N+M automatic rerouting systems provide, on a single switching
equipment, M restoration links to N\ normal ones. The restoration of 1\ normal
link is effected by a certain number of restoration links that are assembled
together.
.PP
The restoration systems belong to a restoration network.
.PP
Figure 2/M.495 illustrates such a configuration.
.RT
.sp 2P
.LP
3.2
\fIMethod of transmission restoration\fR
.sp 1P
.RT
.PP
3.2.1
At the present time, this type of restoration is generally
effected at high hierarchical levels.
.sp 9p
.RT
.PP
3.2.2
The organization of N+M automatic rerouting systems is generally complex:
a network of normal links is protected by a network of restoration
links.
.PP
There is a supervision and control of every link that can be done by or
under the control of one or several restoration control centres.
Restoration can be a specific function of a more general control centre.
.PP
3.2.3
After a failure is detected on a normal link, the restoration is
normally effected according to certain preestablished restoration plans,
if the restoration links are available. It is also possible to have a restoration
plan computed after failure detection.
.PP
A certain number of restoration links are assembled together
through switches located at the nodes of the network and connected to the
faulty link through switches located at its ends.
.PP
3.2.4
It should also be possible to have manual or semi\(hyautomatic
(remote\(hymanual) action or inhibition of N+M automatic rerouting systems.
.PP
3.2.5
If a restoration plan fails or a restoration link used for a
restoration has a failure, all restoration links involved in the restoration
plan should be released.
.PP
3.2.6
After the fault of the normal link is removed, there can be a
switchback to the normal link which should have a minimal impact on
transmission quality and availability.
.PP
3.2.7
Certain equipment, such as automatic digital distribution frames, might
have a function of N+M automatic rerouting but might not be dedicated
to it.
.sp 1P
.LP
3.3
\fIRestoration time\fR
.sp 9p
.RT
.PP
As the operations of N+M automatic rerouting take network
conditions into account, they can involve considerable data processing; they
may entail all calls being cleared or lost before the operations are completed.
Restoration times can be in the order of seconds, minutes, or even hours,
depending on the complexity of the network and its state at that moment.
.RT
.sp 2P
.LP
3.4
\fIOther considerations\fR
.sp 1P
.RT
.PP
3.4.1
Restoration links might be used under normal conditions by
low\(hypriority traffic. In this case, there is generally a preemption
by normal traffic in case of normal link failure.
.sp 9p
.RT
.PP
3.4.2
As the restoration network might not be dimensioned for the total restoration
of all transmission route interruptions and multiple failures, it might
be necessary to define certain priorities among normal links. In this
case, certain links might be restored in priority with preemption of
restoration links used by non\(hypriority links.
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation, \fICharacteristics of 1+1 type restoration\fR
\fIsystems for use on digital transmission links\fR , Rec.\ G.181.
.LP
[2]
CCITT Recommendation, \fICharacteristics of N+M type direct\fR
\fItransmission restoration systems for use on digital sections, links or\fR
\fIequipments\fR , Rec.\ G.180.
.bp
.IP
\fB2.5\ Routine\ maintenance\ of\ an\ international\ carrier\ system\fR
.sp 1P
.RT
.sp 2P
.LP
\fBRecommendation\ M.500\fR
.RT
.sp 2P
.ce 1000
\fBROUTINE\ MAINTENANCE\ MEASUREMENTS\ TO\ BE\ MADE\ ON\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.500''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.500 %'
.ce 0
.sp 1P
.ce 1000
\fBREGULATED\ LINE\ SECTIONS\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBRadio\(hyrelay regulated line section\fR
.sp 1P
.RT
.PP
Measurements should be made as indicated below:
.RT
.sp 1P
.LP
1.1
\fIRegulated line section terminal stations:\fR
.sp 9p
.RT
.LP
a)
daily reading of the line pilot level if necessitated by
the type of system. It is preferable that such measurements should
always be made at the same time of day;
.LP
b)
as necessary, readjustment to the nominal value as described in Recommendation\
M.510.
.sp 1P
.LP
1.2
\fIRadio\(hysystems terminals\fR
.sp 9p
.RT
.PP
1.2.1
At intervals to be determined by agreement between the
Administrations concerned, and based on experience of the reliability of the
system:
.LP
\(em
measurement of the loss/frequency distortion at frequencies in the baseband
(additional measuring frequencies) (permissible
limits \(+- | \ dB);
.LP
\(em
when there is no continuous recording of noise, measurement of
the total noise level on the noise\(hymeasurement channels outside
the baseband in accordance with CCIR
Recommendation\ No.\ 398
.FS
Where a protection channel is
provided, and if Administrations so desire, noise measurements
may be made on that channel with artificial loading, in
accordance with CCIR Recommendation\ 399\ [2].
.FE
\ [1]. This
measurement can be made without causing any interference in the
transmission channel.
.PP
1.2.2
When the measurement mentioned in \(sc\ 1.2.1 above gives
unacceptably high noise values, or more often, when the reliability of the
system makes it desirable, check of the following measurements in accordance
with the appropriate CCIR Recommendations for the radio\(hyrelay system
concerned should be made, the radio\(hyfrequency channel being switched
to the standby
equipment, and the measurement results compared with the results of the
reference measurements required by Recommendation\ M.450, \(sc\ 3:
.LP
\(em
the deviation of the frequency at which the level is
unchanged by pre\(hyemphasis;
.LP
\(em
the pilot frequency deviation;
.LP
\(em
the central position of the intermediate frequency in the
non\(hymodulated condition of the system;
.LP
\(em
the level of the baseband reference frequency (single frequency check);
.LP
\(em
the relative level at the radio reference measurement
frequencies (multifrequency check);
.LP
\(em
the level of individual interfering signals in the baseband in the non\(hymodulated
condition of the system.
.PP
1.2.3
So as to enable the limits for circuit loss variation to be met
(see Recommendation\ M.160), the difference in response between two systems
in diversity reception or between a working and standby system should be
minimized.
.sp 2P
.LP
\fB2\fR \fBCoaxial regulated line section\fR
.sp 1P
.RT
.PP
The following measurements should be made at regulated line section terminal
stations:
.RT
.LP
a)
daily reading of the line pilot level if necessitated by the type of
system. It is preferable that such measurements should
always be made at the same time of day;
.LP
b)
as necessary, readjustment to the nominal value as described in Recommendation\
M.510.
.PP
The Administrations concerned are left to decide for themselves
about measurements at additional measuring frequencies and about checking
the operation of the regulators.
.PP
\fINote\fR \ \(em\ Precautions to be taken with additional measuring
frequencies:
.RT
.LP
i)
When the end of a regulated line section:
.LP
\(em
is not the same as the end of a line link (i.e. when all the
groups, supergroups, etc., are through\(hyconnected from one
regulated line section to another without passing via the
through\(hyconnection equipment to the basic groups);
.bp
.LP
\(em
is the same as the end of a line link without complete
demodulation to the groups, supergroups or mastergroups (i.e.
.LP
when only part of the groups, supergroups, etc., are
through\(hyconnected direct from one line link to another,
without passing via the through\(hyconnection equipment to the
basic groups);
.LP
the maintenance personnel should:
.LP
a)
avoid sending a measuring frequency that is the same as a
pilot frequency of a following regulated line section (unless
the pilot frequency on such a following section is protected
by a blocking filter at the beginning of the section);
.LP
b)
take into account the possibility of attenuation to
additional measuring frequencies lying at the edges of the
frequency band of a through\(hyconnected basic group, supergroup,
etc., due to the presence of through\(hyconnection filters.
.LP
ii)
Interference between additional measuring frequencies on
adjacent coaxial links is possible if precautions are not taken
to avoid carrying out simultaneous measurements on adjacent links.
For this reason:
.LP
a)
there should be different dates for routine maintenance
measurements on two adjacent links;
.LP
b)
before making any measurement using an additional measuring
frequency, and especially those made when clearing faults,
repeater station staff should see to it that measurements
are not in progress on an adjacent coaxial link.
.sp 2P
.LP
\fB3\fR \fBSymmetric pair regulated line section\fR
.sp 1P
.RT
.PP
The following measurements should be made at regulated line section terminal
stations:
.RT
.LP
a)
daily reading of the line pilot level if necessitated by the type of
system. It is preferable that such measurements should
always be made at the same time of day;
.LP
b)
as necessary, readjustment to the nominal value as described in Recommendation\
M.510.
.LP
.PP
The Administrations concerned are left to decide on measurements at additional
measuring frequencies and on checking the operation of the
regulators, if applicable. The same applies to any kind of measurement
or pilot level reading at intermediate attended or unattended stations.
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCIR Recommendation \fIMeasurements of noise in actual traffic over\fR
\fIradio\(hyrelay systems for telephony using frequency\(hydivision multiplex\fR
,
Vol.\ IX, Rec.\ 398, ITU, Geneva,\ 1986.
.LP
[2]
CCIR Recommendation \fIMeasurement of noise using a continuous\fR
\fIuniform spectrum signal on frequency\(hydivision multiplex\fR \fItelephony
radio\(hyrelay systems\fR , Vol.\ IX, Rec.\ 399, ITU,
Geneva,\ 1986.
.sp 2P
.LP
\fBRecommendation\ M.510\fR
.RT
.sp 2P
.ce 1000
\fBREADJUSTMENT\ TO\ THE\ NOMINAL\ VALUE\ OF\ A\ REGULATED\ LINE\ SECTION\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.510''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.510 %'
.ce 0
.sp 1P
.ce 1000
\fB(ON\ A\ SYMMETRIC\ PAIR\ LINE,\ A\ COAXIAL\ LINE\ OR\ A\ RADIO\(hyRELAY\
LINK)\fR
.ce 0
.sp 1P
.PP
After the routine measurement or clearance of the fault and
when it has been ensured that no faults remain on the system, adjustments
should be made as necessary to bring the levels of the line pilots and
additional measuring frequencies as close as possible to their nominal value.
.sp 1P
.RT
.PP
Making the whole adjustment in the receiving terminal station
should be avoided; adjustments should be made where they are necessary,
under the direction of the control or sub\(hycontrol station concerned.
.PP
Methodical readjustment should be carried out when the level measured at
the terminal station exceeds the maintenance limits for the carrier system.
Due allowance should be made for measuring errors and for random effects
which may cause slight short\(hyterm variation. The tolerance to be allowed
depends on the type of system, its length and the periodicity of the measurements.
.PP
For example, the following tolerances may be allowed:
.RT
.LP
a)
in the case of a system with continuous gain control an
adjustment should be made only if an improvement of at least
0.3\ dB can be obtained;
.LP
b)
in the case of a system with step\(hyby\(hystep gain control allow a
permissible tolerance of \(+-\ (one\(hyhalf the gain control
step\ \(+- | .3\ dB).
.bp
.sp 2P
.LP
\fBRecommendation\ M.520\fR
.RT
.sp 2P
.ce 1000
\fBROUTINE\ MAINTENANCE\ ON\ INTERNATIONAL\ GROUP,\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.520''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.520 %'
.ce 0
.sp 1P
.ce 1000
\fBSUPERGROUP,\ ETC.,\ LINKS\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBType of routine tests\fR
.sp 1P
.RT
.PP
Only measurements of the pilot level are made on international
group, supergroup, etc. links. These do not involve other stations. Therefore,
Administrations are free to decide on the methods and periodicities. In
order to ensure that the performance limits of the links laid down in
Recommendation\ M.160 are met, the following tests are recommended for
consideration.
.RT
.sp 2P
.LP
\fB2\fR \fBLinks without an automatic regulator\fR
.sp 1P
.RT
.PP
At control stations routine measurements should be made of the
pilot level. The periodicity of these routines may be weekly or monthly
depending on the complexity of the routing and constitution of the link.
.RT
.sp 2P
.LP
\fB3\fR \fBLinks with an automatic regulator\fR
.sp 1P
.RT
.PP
At control stations where a regulator is installed, the level at
the input and output of the regulator, if these measurement points are
provided by the equipment, may be measured every six\ months.
.RT
.sp 2P
.LP
\fB4\fR \fBContinuous recording of pilot level\fR
.sp 1P
.RT
.PP
In addition to the above it is useful to be able to take continuous pilot\(hyrecordings
as required to detect fault conditions which do not
trigger the normal alarm systems.
.RT
.LP
.sp 2P
.LP
\fBRecommendation\ M.525\fR
.RT
.sp 2P
.ce 1000
\fBAUTOMATIC\ MAINTENANCE\ PROCEDURES\ FOR\ INTERNATIONAL\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.525''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.525 %'
.ce 0
.sp 1P
.ce 1000
\fBGROUP,\ SUPERGROUP,\ ETC.,\ LINKS\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral\fR
.sp 1P
.RT
.PP
In order to reduce corrective maintenance and minimize preventive maintenance
in accordance with Recommendation\ M.20 the routine measurements of group,
supergroup,\ etc. links may be carried out by automatic measurements
without interruption.
.PP
Such routine measurements, where provided, should be for the same
characteristics given in Recommendation\ M.460, e.g.\ overall loss, random
noise,\ etc.
.PP
The decision to use automatic measurement procedures and the
determination of intervals between routine measurements are matters for
agreement by the concerned Administrations.
.PP
The need for readjustment based on the results of these measurements
should be determined according to Recommendation\ M.530.
.RT
.sp 2P
.LP
\fB2\fR \fBFrequencies and levels of test signals\fR
.sp 1P
.RT
.PP
The recommended frequencies for overall loss measurement are given in Table\
1/M.525. The maintenance measurements can be made at some or all of
those frequencies.
.PP
The test frequencies for group, supergroup, etc. links are chosen to fall
between channels
, groups, supergroups,\ etc. These frequencies are shifted at \(+- | 0\
Hz with respect to 4\ kHz multiplied frequencies to avoid
carrier leaks and other spurious tones interference. The
automatic
measurement equipment
usually makes use of pre\(hydefined software and/or
hardware.
.bp
.PP
Test frequencies for supermastergroups are not shifted at \(+- | 0\ Hz,
as they are located in wide guard intervals and do not coincide with carrier
leaks and pilot frequencies.
.PP
Test frequencies 9008\ kHz, 11 | 96\ kHz and 11 | 48\ kHz given in
Recommendation\ M.460 should be shifted to avoid interferences between
supermastergroup and mastergroup No.\ 7 and No.\ 9 pilot frequencies (see
Recommendation\ M.350).
.PP
Test signal levels should generally not exceed \(em20\ dBm0. A level of
\(em10\ dBm0 may be used for master and supermastergroup measurements. When the
measurement of Group No.\ 3 (see Recommendation\ M.330) is being made,
the test signal at 103.92\ kHz has to be blocked, otherwide it is necessary
to make the correction for the loss at the frequency 103.92\ kHz, caused
by the 411.86\ kHz reject filter.
.RT
.ce
\fBH.T. [T1.525]\fR
.ce
TABLE\ 1/M.525
.ce
\fBFrequencies of test signals\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(60p) | cw(120p) .
Type of link Frequencies (kHz)
_
.T&
lw(60p) | lw(120p) .
Supermaster group {
8516.3*, 8760, 9004, 9256, 9504, 9792, 10 | 80, 10 | 24, 10 | 76, 10 | 24,
11 | 50, 11 | 00, 11 | 44, 11 | 96, 12 | 44, 12 | 87.4*
}
_
.T&
lw(60p) | lw(120p) .
Master group {
812.6*, 871.92, 931.92, 1055.92, 1179.92, 1303.92, 1427.92, 1555.92,
1675.92, 1799.92, 1923.92, 1983.92, 2043.7*
}
_
.T&
lw(60p) | lw(120p) .
Supergroup (4 kHz channels) {
312.3*, 320.08, 328.08, 344.08, 360.08, 376.08, 392.08, 408.08, 432.08,
456.08, 472.08, 488.08, 504.08, 520.08, 536.08, 544.08, 551.4*
}
_
.T&
lw(60p) | lw(120p) .
Group (4 kHz channels) {
60.6*, 63.92, 67.92, 71.92, 75.92, 79.92, 83.92, 87.92, 91.92, 95.92,
99.92, 103.92, 107.7*
}
.TE
.LP
\fINote\fR
\ \(em\ As a rule the frequencies marked by an asterisk (*) cannot be used
for measurements without traffic interruption. These frequencies may be
used in the absence of traffic in the edge channels or a low level of
test signal (below \(em45\ dBm0).
.nr PS 9
.RT
.ad r
\fBTable 1/M.525 [T1.525], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 4
.sp 2P
.LP
\fBRecommendation\ M.530\fR
.RT
.sp 2P
.ce 1000
\fBREADJUSTMENT\ TO\ THE\ NOMINAL\ VALUE\ OF\ AN\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.530''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.530 %'
.ce 0
.sp 1P
.ce 1000
\fBINTERNATIONAL\ GROUP,\ SUPERGROUP,\ ETC.,\ LINK\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral\fR
.sp 1P
.RT
.PP
Before any adjustment is made to a link it must first be ensured
that each regulated line section or higher\(hyorder link over which the link
concerned is routed is correctly adjusted and that the level of the reference
pilot at the transmitting end is correct. No readjustments will be made
on the link except under the direction of the control station, after consideration
of measurement results.
.bp
.RT
.sp 2P
.LP
\fB2\fR \fBLinks without a regulator\fR
.sp 1P
.RT
.PP
2.1
For links which use only one regulated line section, or one
higher\(hyorder link, readjustment of levels to values as close as possible to
their nominal value must be made systematically after any measurement or
clearance of a fault. Any departure in excess of \(+- | \ dB from the original
.sp 9p
.RT
.LP
line\(hyup at the time the link was first established must be investigated to
ensure that there is no fault.
.PP
2.2
For links of more complex constitution, no readjustment need be
made until the departure from the nominal value exceeds\ 0.5\ dB (see the Note
in \(sc\ 3 of this Recommendation). When the departure from the nominal value
exceeds these limits, adjustment to a value as near as possible to the
nominal value should be carried out. Adjustment at the terminal station
only is
permissible within the limits of departure from the settings at the time
of the previous reference measurements as a function of the distance to
the origin of the link or to the nearest upstream automatic regulator,
as given in
Table\ 1/M.530.
.ce
\fBH.T. [T1.530]\fR
.ce
TABLE\ 1/M.530
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(84p) | cw(144p) .
{
Distance to origin
or regulator
} {
Limit for departure from the settings noted for previous reference
measurements beyond which the possibility of a fault should be
investigated
(see the note in \(sc\ 3 of this
Recommendation)
}
_
.T&
lw(84p) | cw(144p) .
Up to 1000 km \(+- | dB
.T&
lw(84p) | cw(144p) .
1000\(hy2000 km \(+- | dB
.T&
lw(84p) | cw(144p) .
Above 2000 km \(+- | dB
_
.TE
.nr PS 9
.RT
.ad r
\fBTABLE [T1.530], p.\fR
.sp 1P
.RT
.ad b
.RT
.PP
If, for the distance concerned, adjustment at the terminal station would
cause departures greater than those permitted by the table, measurements
should be made at all through\(hyconnection points to find if a fault exists.
If a fault exists, it should be located and cleared. If no fault exists,
but the
.LP
change is due to normal causes, e.g. temperature changes, aging, etc.,
adjustments should be made at each through\(hyconnection point to bring
the level of the reference pilot as near as possible to its nominal value
before making a final adjustment at the terminal station.
.sp 2P
.LP
\fB3\fR \fBLinks with a regulator\fR
.sp 1P
.RT
.PP
No readjustment need be made until the departure from the nominal value
measured at the input to the regulator exceeds\ \(+- | \ dB. Any departure
in excess of \(+- | \ dB from the nominal value measured at this point
must be
investigated.
.PP
\fINote\fR \ \(em\ In determining the margins within which equipment should
be readjusted, it has been found useful to distinguish three ranges about
the
nominal value into which the received level might fall:
.RT
.LP
\(em
a relatively small range in which no action need be taken.
This enables the staff to avoid waste of time in continually
readjusting in order to compensate minor changes;
.LP
\(em
a somewhat larger range in which the received level may be
readjusted to as near the nominal value as possible by the
terminal station, without having to ask intermediate stations to
measure and/or readjust. (This is subject to the overriding
proviso that the cumulative adjustment made at the terminal
station must not exceed a certain amount relative to the settings
noted when the last set of reference measurements was made);
.LP
\(em
a range in which it must be assumed that a fault may exist
which must be sought and cleared before any readjustment is permitted.
After the fault (if any) has been found and all stations,
intermediate and terminal, have, if necessary, readjusted their
levels to as near the nominal value as possible, the new settings
are noted for future reference purposes when making subsequent
adjustments.
.bp
.PP
The three ranges are shown in Figure\ 1/M.530 in relation to a
typical distribution of level values.
.PP
A suitable value for \fIy\fR in Figure 1/M.530 is considered to be 2\ \fIS\fR
, where \fIS\fR is the observed standard deviation. This concept is the
basis of
Table 1/M.530.
.RT
.LP
.rs
.sp 19P
.ad r
\fBFIGURE 1/M.530 p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 3
.sp 2P
.LP
\fBRecommendation\ M.535\fR
.RT
.sp 2P
.ce 1000
\fBSPECIAL\ MAINTENANCE\ PROCEDURES\ FOR\ MULTIPLE\ DESTINATION,\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.535''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.535 %'
.ce 0
.sp 1P
.ce 1000
\fBUNIDIRECTIONAL\ (MU)\ GROUP\ AND\ SUPERGROUP\ LINKS\fR
.ce 0
.sp 1P
.PP
The Recommendations covering the maintenance of groups and
supergroups will apply as far as possible but there will be a number of new
maintenance problems which are peculiar to multiple destination links. In
particular, arrangements will be needed to check the performance of the
MU main section
of such links. In order to simplify the procedures and
.sp 1P
.RT
.LP
minimize interference to other users of the common path, it is recommended
that the send reference station (see Figure\ 1/M.460) for the MU\ main
section should act as a focal point for reports and inquiries concerning
the MU\ main section. The group, supergroup, etc., control stations will
still be responsible for
localizing a fault to a particular section of a link in accordance with
Recommendation\ M.130.
.PP
When a fault is found to be in the communication satellite link, the send
reference station will report the fault to the satellite control
responsible for this link from baseband\(hyin to baseband\(hyout. When
the fault is cleared, the send reference station will advise the MU\ main
section controls
which will in turn advise the group, supergroup, etc., controls concerned.
.bp
.sp 2P
.LP
\fBRecommendation\ M.540\fR
.RT
.sp 2P
.sp 1P
.ce 1000
\fBROUTINE\ MAINTENANCE\ OF\ CARRIER\ AND\ PILOT\ GENERATING\ EQUIPMENT\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.540''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.540 %'
.ce 0
.sp 1P
.PP
\fB1\fR
If a country has a
national frequency standard
, it is desirable to use it for checking the frequency of the
master oscillators of carrier systems
. (See Table\ 1/M.540 showing the recommended frequency
accuracy for various carrier systems.) This frequency standard can be
guaranteed to about 1\ part in 10\u8\d by means of the
three\(hyway frequency
comparisons
organized by the CCIR. However, we must note that a larger
accuracy can be obtained in the countries that will use an
atomic frequency standard
(for example cesium or rubidium).
.sp 1P
.RT
.PP
\fB2\fR
If a country has no national frequency standard, there are
two possibilities:
.sp 9p
.RT
.LP
a)
to receive by radio the standard signals transmitted in
accordance with CCIR Recommendations;
.LP
b)
to receive from a neighbouring country, over a metallic
circuit, a frequency derived from the national standard of that country.
.PP
It may be necessary in some cases to make a direct comparison of the frequency
of the master oscillators of the carrier systems of different
countries; this comparison will be effected by means of the frequency
comparison pilots.
.PP
\fB3\fR
The changeover of master oscillators may cause a short
interruption of a few milliseconds and a sudden phase\(hychange. Because the
effect of these interruptions and phase\(hychanges is felt throughout the
carrier system, changeover of master oscillators should be made only when
absolutely necessary.
.sp 9p
.RT
.LP
.rs
.sp 27P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [1T1.540]\fR
.ce
TABLE\ 1/M.540
.ce
\fBTable showing the recommended frequency accuracy for reference pilots,
.ce
carriers, etc.,\fR
.ce
\fBin various carrier systems\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(72p) | cw(84p) sw(72p) , ^ | c | c.
System Frequency and accuracy
Reference pilot Carrier generator
_
.T&
cw(72p) | cw(84p) | cw(72p) .
(1) (2) (3)
_
.T&
lw(72p) | cw(42p) | cw(42p) | cw(72p) .
(1 + 3) open\(hywire 16.110 kHz 31.110 kHz 2.5 \(mu 10\uD\dlF261\u5\d 2.5 \(mu 10\uD\dlF261\u5\d
_
.T&
lw(72p) | lw(84p) | cw(72p) .
8 circuit open\(hywire 10\uD\dlF261\u5\d
_
.T&
lw(72p) | cw(84p) | cw(72p) .
12 circuit open\(hywire 5 \(mu 10\uD\dlF261\u6\d 5 \(mu 10\uD\dlF261\u6\d
_
.T&
lw(72p) | lw(60p) | lw(24p) .
Symmetric pair Line regulating
.T&
lw(72p) | cw(60p) | cw(24p) .
\ \ | 60 kHz \ \(+- | Hz
.T&
lw(72p) | lw(60p) | cw(24p) .
1, 2, 3, 4 or 5 groups Auxiliary \ \(+- | Hz
_
.T&
lw(72p) | lw(60p) | cw(24p) .
2 supergroups {
Line regulating
\ \ | 60 kHz
\ \ | 56 kHz
} \ \(+- | Hz \ \(+- | Hz
.T&
lw(48p) | cw(24p) | lw(60p) | cw(24p) .
2.6 MHz Line regulating \ 2 | 04 kHz \fB.\fR \(+- | 0 Hz
_
.T&
lw(48p) | cw(24p) | lw(60p) | cw(24p) .
\fB2,\fR 4 MHz {
Line regulating
\ \ | 60 kHz
\ \ | 08 kHz
\ 4 | 92 kHz
Auxiliary
\ 2 | 92 kHz
} {
\fB.\fR
\ \(+- | 1 Hz
\ \(+- | 3 Hz
\(+- | 0 Hz
\fB.\fR
\ \(+- | 5 Hz
}
.T&
lw(84p) .
.T&
lw(48p) | lw(24p) | lw(60p) | cw(24p) .
{
Additional measuring
frequencies (all)
} \(+- | 0 Hz
.T&
lw(108p) .
.T&
cw(48p) | cw(24p) | lw(60p) | lw(24p) | lw(72p) , ^ | ^ | l | l | ^ .
Coaxial pair 2.6/9.5\ mm {
\fB,\fR
12 MHz
Line regulating
\ \ | 08 kHz
\ 4 | 87 kHz
12 | 35 kHz
\(+- | \(mu 10\uD\dlF261\u5\d
Additional measuring
frequencies:
< 4 MHz
> 4 MHz
\fB.\fR
\fB.\fR
\(+- | 0 Hz
\(+- | \(mu 10\uD\dlF261\u5\d
} {
Channel virtual carriers of a group
\(+- | 0\uD\dlF261\u6\d
Groups and supergroups
\(+- | 0\uD\dlF261\u7\d
Mastergroups and supergroups
\(+- | \(mu 10\uD\dlF261\u8\d
}
.T&
lw(108p) .
.T&
lw(48p) | cw(24p) | lw(60p) | cw(24p) .
\fB,\fR 60 MHz {
Line regulating
\ 4 | 87 kHz
12 | 35 kHz
22 | 72 kHz
40 | 20 kHz
61 | 60 kHz
} {
\(+- | \(mu 10\uD\dlF261\u5\d
}
.T&
lw(84p) .
.T&
lw(48p) | lw(24p) | lw(60p) | cw(24p) .
{
Additional measuring
frequencies (all)
} {
\(+- | \(mu 10\uD\dlF261\u5\d
}
.T&
lw(156p) .
.T&
cw(48p) | lw(24p) | lw(60p) | lw(24p) , ^ | l | l | l
^ | l | l | l.
{
Coaxial pairs
1.2/4.4 mm
1.3 MHz
Line regulating
\ 1 | 64 kHz
Auxiliary
60 or 308 kHz
\fB.\fR
\(+- | \(mu 10\uD\dlF261\u5\d
\fB.\fR
\(+- | \(mu 10\uD\dlF261\u5\d
\fB1,\fR
4 MHz
Line regulating
60, 308, 4287 kHz
\(+- | \(mu 10\uD\dlF261\u5\d
\fB1,\fR
6 MHz
Line regulating
308, 4287 kHz
\(+- | \(mu 10\uD\dlF261\u5\d
}
_
.T&
lw(228p) .
.TE
.nr PS 9
.RT
.ad r
\fR \fBTableau 1/M.540 [1T1.540], p. 14\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [2T1.540]\fR
.ce
TABLE\ 1/M.540 | fI(cont.)\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(72p) | cw(84p) sw(72p) , ^ | c | c.
System Frequency and accuracy
Reference pilot Carrier generator
_
.T&
cw(72p) | cw(84p) | cw(72p) .
(1) (2) (3)
_
.T&
cw(72p) | lw(60p) | cw(24p) | lw(72p) .
12 + 12 {
60 kHz
Others by agreement between Administrations
} \ \(+- | Hz {
Error in reconstituted frequency over a 140\ km section and not to
exceed 0.3\ Hz (provisional value)\fR
}
_
.T&
cw(72p) | lw(84p) | lw(72p) .
\ 6 MHz {
Video carrier
1056 kHz \(+- 5 Hz
}
_
.T&
cw(72p) | lw(84p) | lw(72p) .
12 MHz {
Video carrier
6799 kHz \(+- 100 Hz
}
_
.T&
lw(72p) | lw(60p) | lw(24p) .
4 kHz spacing
.T&
lw(72p) | cw(60p) | cw(24p) .
{
Basic group B
\ \ \ and
Basic supergroup
} {
\ 84.080 kHz \fBand\fR
104.080 kHz
411.920 kHz and 547.920 kHz
\ 84.140 kHz and 411.860 kHz\fR
} {
\fB.\fR
\ \(+- | Hz
\ \(+- | Hz
}
_
.T&
lw(72p) | cw(60p) | cw(24p) .
{
Basic mastergroup and
15\(hysupergroup assembly
} {
\ \ 1 | 52 kHz \fBand 547.920 kHz\fR
} \ \(+- | Hz
_
.T&
lw(72p) | cw(60p) | cw(24p) .
Basic supermastergroup {
\ 11 | 96 kHz \fBand 547.920 kHz\fR
} \(+- | 0 Hz
_
.T&
lw(72p) | cw(60p) | cw(24p) .
3 kHz spacing {
84 kHz (or other frequency by agreement)
} \ \(+- | Hz
_
.T&
lw(72p) | cw(60p) | cw(24p) .
{
Basic group and
Basic supergroup
} {
\ \ua\d\u)\d\fB | 52 kHz and 547.920 kHz\fR
}
.T&
lw(228p) .
.TE
.nr PS 9
.RT
.ad r
\fR \fBTableau 1/M.540 fin [2T1.540], p. 15\fR
.sp 1P
.RT
.ad b
.RT
.LP
.rs
.sp 16P
.ad r
Blanc
.ad b
.RT
.LP
.bp
.IP
2.6\ \fBBringing into service and maintenance of international digital
transmission systems\fR
.sp 1P
.RT
.sp 2P
.LP
\fBRecommendation\ M.550\fR
.RT
.sp 2P
.ce 1000
\fBPERFORMANCE\ LIMITS\ FOR\ BRINGING\ INTO\ SERVICE\ AND\ MAINTENANCE\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.550''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.550 %'
.ce 0
.sp 1P
.ce 1000
\fBOF\ DIGITAL\ PATHS,\ SECTIONS,\ AND\ LINE\ SECTIONS\fR
.ce 0
.sp 1P
.LP
\fB1\fR \fBGeneral\fR
.sp 1P
.RT
.PP
The purpose of this Recommendation is to provide limits for
bringing into service, and limits for maintenance of digital paths, sections,
and line sections in order to achieve the performance objectives given
for ISDN in the Series\ G Recommendations. These objectives include error
performance
(Rec.\ G.821\ [1]), slips (Rec.\ G.822\ [2]), jitter and wander (Rec.\
G.823\ [3]
and
Rec.\ G.824\ [4]), and availability. This Recommendation presently only
contains
.PP
limits for error performance. The other limits are under study. This
Recommendation describes the parameters to be mesured and the measurement
techniques to be employed to meet the principles given in
Recommendations\ M.20, M.32 and\ M.34.
.PP
The methods and procedures for applying these limits are described in Recommendation\
M.555 for the bringing into service procedures.
.PP
Since the performance limits are intended to satisfy the needs of the future
digital network, it must be recognized that such limits cannot be
readily achieved by all of today's digital equipment and systems. Nonetheless,
it is intended that there will be a single set of limits that applies to
all
technologies.
.PP
It is desirable to do in\(hyservice, continuous measurements. In some
cases e.g.\ for bringing into service, out\(hyof\(hyservice measurements may be
necessary.
.PP
This Recommendation covers all digital paths, sections, and line
sections which operate at 64\ kbit/s and higher, including the ISDN subscriber
access described in Recommendation\ I.412\ [5], and the network digital
hierarchy described in Recommendation\ G.702\ [6].
.PP
There is a need to reduce measured data to that which is essential
and relevant to maintenance staff.
.RT
.sp 2P
.LP
\fB2\fR \fBAllocation of objectives\fR
.sp 1P
.RT
.PP
Digital error performance objectives on which this Recommendation is based
are given in Recommendation\ G.821\ [1] for an end\(hyto\(hyend 64\ kbit/s
hypothetical reference connection (HRX) defined in Recommendation\ G.801\
[7]. These objectives are further allocated in Recommendation\ G.821\ [1]
to local,
medium, and high grade parts of the connection. However, maintenance limits
are needed for smaller entities. Hence, a further allocation is necessary,
so that limits can be developed for digital paths, digital sections, and
digital line sections, as these are defined in Recommendation\ M.300. Following
are described the reference models to be used when allocating the digital
performance
objectives on which bringing into service and maintenance limits will be
based.
.RT
.sp 1P
.LP
2.1
\fIReference models\fR
.sp 9p
.RT
.PP
The HRX of Recommendation G.801 [7] and the circuit quality
demarcation of Recommendation\ G.821\ [1] are shown combined in
Figure\ 1/M.550.
.RT
.PP
The error performance objectives for this 64 kbit/s connection are given
in Table\ 1/M.550.
.PP
Half of the overall severely errored seconds, (SES) objective of 0.2% is
reserved as a block allocation to accommodate adverse network
conditions (e.g.\ for digital radio systems) so the values in Table\ 2/M.550
apply to the remaining 0.1% SES. These overall objectives are further allocated
to the circuit quality classifications of the HRX as shown in Table\ 2/M.550.
.PP
For Recommendation G.921 [8], a further allocation of objectives to hypothetical
reference digital sections (HRDS) based on the 2.048\ Mbit/s hierarchy
is shown in Table\ 3/M.550. An HRDS is a digital line section in the terminology
of Recommendation\ M.300.
.bp
.LP
.rs
.sp 22P
.ad r
\fBFigure 1/M.550, p. 16\fR
.sp 1P
.RT
.ad b
.RT
.ce
\fBH.T. [T1.550]\fR
.ce
TABLE\ 1/M.550
.ce
\fBError performance objectives\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(90p) | cw(90p) .
Performance classification Objective (maximum % of time)
_
.T&
lw(90p) | cw(90p) .
Degraded minutes (DM) 10\fB.\ \fR
.T&
lw(90p) | cw(90p) .
{
Severely errored seconds (SES)
} \ 0.2
.T&
lw(90p) | cw(90p) .
Errored seconds (ES) \ 8\fB.\ \fR
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 1/M.550 [T1.550], p. 17\fR
.sp 1P
.RT
.ad b
.RT
.ce
\fBH.T. [T2.550]\fR
.ce
TABLE\ 2/M.550
.ce
\fBAllocation of objectives\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(90p) | cw(90p) .
{
HRX circuit quality classification
} Percentage of objective
_
.T&
lw(90p) | cw(90p) .
Local (each end) 15
.T&
lw(90p) | cw(90p) .
Medium (each end) 15
.T&
lw(90p) | cw(90p) .
High 40
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 2/M.550 [T2.550], p. 18\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.ce
\fBH.T. [T3.550]\fR
.ce
TABLE\ 3/M.550
.ce
\fBDigital line section quality classificaton for error
.ce
performance\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(54p) | cw(54p) | cw(54p) | cw(54p) .
Section quality class HRDS length (km) Allocation (%) For circuit class
_
.T&
cw(54p) | cw(54p) | cw(54p) | cw(54p) .
1 280 0.45 High or medium
.T&
cw(54p) | cw(54p) | cw(54p) | cw(54p) .
2 280 2\fB.45\fR Medium
.T&
cw(54p) | cw(54p) | cw(54p) | cw(54p) .
3 \ 50 2\fB.45\fR Medium
.T&
cw(54p) | cw(54p) | cw(54p) | cw(54p) .
4 \ 50 5\fB.45\fR Medium
_
.TE
.nr PS 9
.RT
.ad r
\fBTableau 3/M.550 [T3.550], p. 19\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 4
.PP
The allocation is a percentage of the overall objective for the
HRX for Errored Seconds (ES), SES, and Degrated Minutes (DM). For shorter
sections, there is no reduction in the allocation. For a longer section,
its
overall allocation should correspond to that of an integer number of HRDSs,
the combined length of which is at least as long as the real section.
.PP
These figures and tables are simplified versions of those in
Recommendations\ G.801\ [7], G.821\ [1], and\ G.921\ [8]. For a full explanation,
the original figures and tables, along with their footnotes, should be
consulted.
.PP
The comparable allocations for the 1.5\ Mbit/s hierarchy is under study
in Recommendation\ G.911\ [9].
.RT
.sp 1P
.LP
2.2
\fIAllocation principles to be employed\fR
.sp 9p
.RT
.PP
For this Recommendation, the allocation of the error performance
objectives for each digital path, digital section and digital line section,
as defined in Recommendation\ M.300, must be determined. This will be based
on the allocation for the different parts of the HRX as defined in
Recommendation\ G.821\ [1], and on the allocations for digital line sections
as defined in Recommendations\ G.911\ [9] and\ G.921\ [8].
.PP
The allocation principles for satellites are for further study,
taking into account Recommendation\ G.821\ [1].
.PP
The significant performance degradation of radio\(hyrelay systems tend
to be concentrated into a few days or even hours (those times with severe
fading). For this reason, a direct linear derivation of performance limits
for shorter time periods from Recommendation\ G.821\ [1] monthly performance
objectives may not be suitable for digital sections containing radio\(hyrelay
systems.
.PP
The effect of fluctuations that occur in radio\(hyrelay system
performance, as well as to a lesser degree in other transmission media,
requires further study to set appropriate bringing into service limits,
maintenance limits and test durations.
.RT
.sp 1P
.LP
2.2.1
\fIAllocation principles for sections\fR
.sp 9p
.RT
.PP
The objectives to be used for digital line sections can be taken
directly from Recommendations\ G.911\ [9] and\ G.921\ [8].
.PP
However, digital sections and digital paths are achieved by
interconnections of digital line sections and multiplexing equipment at
various hierarchical levels (8, 34, 45, 140\ Mbit/s).
.PP
The performance allocation for digital sections is the sum of the
allocations of the digital line sections from which the digital section is
derived.
.bp
.RT
.sp 1P
.LP
2.2.2
\fIAllocation principles for digital paths\fR
.sp 9p
.RT
.PP
The allocation principles for the paths differ for bringing into
service and for maintenance.
.PP
For bringing into service, the allocation is the same as that for
digital sections, namely the sum of the allocations of the digital line
sections from which the path is derived. This results in an allocation
based on the real physical configuration of the path. If the performance
objective for a path is denoted\ \fIA\fR , then:
\v'6p'
.RT
.sp 1P
.ce 1000
\fIA\fR =
@ pile { sum above \fIj\fR } @ \fIN\fR\d\fIj\fR\u | (mu | fIQ\fR\d\fIj\fR\u
.ce 0
.sp 1P
.LP
.sp 1
where
.LP
\fIN\fR\d\fIj\fR\u Number of digital line sections of quality
class \fIj\fR ,
.LP
\fIQ\fR\d\fIj\fR\u Allocation for a digital line section of quality
class\ \fIj\fR .
.PP
For maintenance allocation, to minimize the number of thresholds that must
be monitored in the exchange, a different objective is used, namely the
maximum allowed allocation for the type of path. This allocation is
determined by the class of exchange at each end of the path. The allocation
principle is illustrated by the following example.
.PP
If the nominal section of Figure 1/M.550 is made up of the 1250\ km
medium grade allocation, the medium grade path allocations can be defined
as:
.RT
.LP
\fIA\fR =
Allocation for path LE\(hyPC (local exchange\(hyprimary centre)
.LP
\fIB\fR =
Allocation for path PC\(hySC (primary centre\(hysecondary
centre)
.LP
\fIC\fR =
Allocation for path SC\(hyTC (primary centre\(hytertiary centre)
.LP
\fID\fR =
Allocation for path TC\(hyISC (tertiary centre\(hyinternational
switching centre)
.LP
Further, let
.LP
\fIW\fR\d\fIi\fR\u =
Number of digital sections of class 1 (allocation
0.45%)
.LP
\fIX\fR\d\fIi\fR\u =
Number of digital sections of class 2 (allocation 2%)
.LP
\fIY\fR\d\fIi\fR\u =
Number of digital sections of class 3 (allocation 2%)
.LP
\fIZ\fR\d\fIi\fR\u =
Number of digital sections of class 4 (allocation 5%)
.LP
where subscript \fIi\fR | denotes the paths LE\(hyPC (denoted as \fIa\fR
), PC\(hySC
(denoted as \fIb\fR ),\ etc. with allocations\ \fIA\fR , \fIB\fR ,\ etc.,
as defined
above.
.PP
To meet the Recommendation G.821 [1] objectives, each
Administration must jointly determine\ \fIA\fR to\ \fID\fR and \fIW\fR\d\fIi\fR\uto
\fIZ\fR\d\fIi\fR\ubased on its transmission plan and on its network design
in order to meet the
equations below:
.LP
\fIA\fR \ +\ \fIB\fR \ +\ \fIC\fR \ +\ \fID\fR \ \(=\ 15%
.LP
\fIA\fR
\(>="
0.45\ \fIW\fR\d\fIa\fR\u\ +\ 2.0\ \fIX\fR\d\fIa\fR\u\ +\ 2.0\ \fIY\fR\d\fIa\fR\u\
+\ 5.0
\fIZ\fR\d\fIa\fR\u
.LP
\fIB\fR
\(>="
0.45\ \fIW\fR\d\fIb\fR\u\ +\ 2.0\ \fIX\fR\d\fIb\fR\u\ +\ 2.0\ \fIY\fR\d\fIb\fR\u\
+\ 5.0
\fIZ\fR\d\fIb\fR\u
.LP
\fIC\fR
\(>="
0.45\ \fIW\fR\d\fIc\fR\u\ +\ 2.0\ \fIX\fR\d\fIc\fR\u\ +\ 2.0\ \fIY\fR\d\fIc\fR\u\
+\ 5.0
\fIZ\fR\d\fIc\fR\u
.LP
\fID\fR
\(>="
0.45\ \fIW\fR\d\fId\fR\u\ +\ 2.0\ \fIX\fR\d\fId\fR\u\ +\ 2.0\ \fIY\fR\d\fId\fR\u\
+\ 5.0
\fIZ\fR\d\fId\fR\u
.PP
For example, if the paths between the LE and PC in this
Administration's network in the worst case are made up of two line sections
of class\ 2 and one of class\ 3, then\ \fIA\fR must be 2\ \(mu\ 2%\ +\
1\ \(mu\ 2%\ =\ 6%.
Thus, \fIB\fR \ +\ \fIC\fR \ +\ \fID\fR must be \(=\ 9%. Similarly, values
of\ \fIB\fR | to\ \fID\fR can be
selected.
.sp 2P
.LP
\fB3\fR \fBRelationship between\fR
\fBperformance limits and objectives\fR
.sp 1P
.RT
.sp 1P
.LP
3.1
\fIRelationship between short\(hyterm limits and long\(hyterm objectives\fR
.sp 9p
.RT
.PP
The limits in this Recommendation are to be used to indicate the
need for actions during the phases of maintenance and bringing into service.
These procedures are intended to result in network performance which meets
the performance objectives of the relevant Series\ G Recommendations. The
particular parameters measured, the measurement duration, and the limits
used for the
procedure need not be identical to those used for specifying the performance
objectives as long as they result in network performance which meets these
objectives. For example, the error performance objectives refer to long
periods, such as one month. However, practical considerations demand that
maintenance and bringing\(hyinto\(hyservice limits be based on shorter
measurement
intervals.
.bp
.PP
Statistical fluctuations in the occurrence of anomalous events in time
means that one cannot be certain that the long\(hyterm objectives are met.
The
limits on the numbers of events and the duration of measurements must be
set to ensure that passing the tests will predict, with an acceptable level
of
confidence, that the long\(hyterm objectives will be met. The limits and
durations given as examples below were arrived at after comparing limits
derived from
statistical theory to empirically observed network performance.
.RT
.sp 1P
.LP
3.2
\fITypes of limits\fR
.sp 9p
.RT
.PP
Limits are needed for several maintenance functions as defined in Recommendation\
M.20. This Recommendation provides limits for three of these
functions: bringing into service, keeping the network operational (called
maintenance here) and system restoration. Limits for
commissioning
(installation and acceptance testing)
are not provided in CCITT
Recommendations.
.PP
Bringing\(hyinto\(hyservice tests
are rigorously done by measuring using a quasi\(hyrandom signal source
(QRSS) between digital junction
interfaces. Due to the statistical character of the degradation in digital
networks, these measurements should be long\(hyterm measurements. This
applies to new equipment or routes. However, for practical reasons (a new
path on a route with many paths already in\(hyservice, rearrangements of
the network,\ etc.) the
measurements between junctions may be reduced to a quick measurement and the
supervision completed with performance monitoring equipment.
.PP
Two limits are provided for use in bringing\(hyinto\(hyservice testing.
If performance is better than the first limit, the entity can be brought
into
service without doubt. If performance is between the two limits, further
testing is necessary. Corrective action is required if performance is worse
than the second limit. The definition of the limits are a function of a
given allocation and of the measurement duration and will be based on a
predictive
model under study. These limits depend on Recommendation\ G.821\ [1] parameters
for a given bit rate.
.PP
Once entities have been placed into service, supervision of the
network requires additional limits, as described in Recommendation\ M.20.
This supervision is done on an in\(hyservice basis using performance monitoring
equipment. The supervision process involves analyzing anomalies and defects
detected by maintenance entities to determine if the performance level is
normal, degraded, or unacceptable. Thus, degraded and unacceptable performance
limits are required. In addition, a limit on performance after intervention
(repair) is also required. It may be different than the bringing\(hyinto\(hyservice
limit.
.RT
.sp 1P
.LP
3.2.1
\fIReference performance objectives\fR
.sp 9p
.RT
.PP
The reference performance objectives are defined as the performance objectives
for ES, SES, and DM directly derived from Recommendations\ G.821\ [1],
G.911\ [9] and\ G.921\ [8] using recommended allocations and from the additional
allocations described above in \(sc\ 2 for digital paths, sections and
line
sections.
.PP
Reference performance objectives are calculated on a long\(hyterm basis
(one month is suggested). These form the basis from which limits for bringing
into service and maintenance are set.
.RT
.sp 1P
.LP
3.2.2
\fIBringing\(hyinto\(hyservice limits\fR
.sp 9p
.RT
.PP
The
aging margin
is the difference between the reference
performance objective and the bringing\(hyinto\(hyservice limit. This margin
should be as large as possible to minimize maintenance interventions.
.PP
This margin for digital line sections will depend on the procedures of
individual Administrations. A stringent limit which is 10\ times better
than the reference performance objective and a measuring period of a few
days should be used when previous commissioning tests have not been conducted.
.PP
When previous commissioning tests have been carried out, the
out\(hyof\(hyservice test for bringing into service can be conducted for
a shorter
period and does not require the same stringent limits.
.PP
Continuous in\(hyservice monitoring is required to provide sufficient
confidence in the long\(hyterm performance. (Typically, commissioning tests
have durations of several days and have more stringent limits than
bringing\(hyinto\(hyservice tests).
.PP
The ageing margin for digital sections and paths is on the order of
two times better than the reference performance objective. The testing
duration will obviously be limited to no more than a few days.
.PP
All of these bringing\(hyinto\(hyservice limits and durations are for
further study.
.bp
.PP
Two limits can be calculated:
.RT
.LP
\(em
S1, a limit corresponding to a number of events (ES, SES, DM)
under which the entity can be brought into service without any
doubt;
.LP
\(em
S2, a limit corresponding to a number of events above which
it is necessary to improve the performance of the entity under
test.
.PP
For an observed number of events between the values of S1 and S2 the entity
may be conditionally be brought into service. It then becomes
necessary to monitor the evolution of its performance during a longer period
of time. This monitoring can be performed using the TMN surveillance capability.
The value of\ S1 is equal to the bringing\(hyinto\(hyservice limit described
above.
The value of\ S2 can be derived from\ S1 using a statistical coefficient under
study.
.sp 2P
.LP
3.2.3
\fIMaintenance limits\fR
.sp 1P
.RT
.sp 1P
.LP
3.2.3.1
\fIUnacceptable performance limits\fR
.sp 9p
.RT
.PP
This performance level is defined in Recommendation\ M.20
(\(sc\ 5.1.3).
.PP
The unacceptable performance limit for a given entity is at least
10\ times worse than the reference performance objective. The monitoring
duration is between 15\ minutes and one hour.
.RT
.sp 1P
.LP
3.2.3.2
\fIDegraded performance limits\fR
.sp 9p
.RT
.PP
This performance level is defined in Recommendation\ M.20
(\(sc\ 5.1.3).
.PP
The degraded performance limit for a given entity is on the order of two
times better for line sections and 1.3\ times better for paths and sections
than the reference performance objective. The monitoring duration may be
a
fixed duration that depends on the rate in the digital hierarchy.
.RT
.sp 1P
.LP
3.2.3.3
\fIPerformance limit after intervention (repair)\fR
.sp 9p
.RT
.PP
This performance limit is on the order of eight times better than the reference
preformance objective for digital line sections and the same as the bringing\(hyinto\(hyservice
limit for digital paths and sections (see
Recommendations\ M.35 and\ M.555).
.RT
.sp 1P
.LP
3.2.4
\fISystem restoration limits\fR
.sp 9p
.RT
.PP
The \*Qrestoration indication signal\*U is used to control sytem
restoration (under study).
.RT
.sp 1P
.LP
3.3
\fIPerformance limits\fR
.sp 9p
.RT
.PP
Performance limits are defined for Recommendation\ G.821 [1]
parameters (ES, SES, DM). It is obvious that each performance limit will
have its own threshold and will require its own measurement duration. Examples
of
the above principles and limits are shown in Figure\ 2/M.550.
.RT
.sp 1P
.LP
3.4
\fITranslation of performance measurements\fR
.sp 9p
.RT
.PP
Translation of performance measurements at primary rate and above, to error
performance parameters at 64\ kbit/s will follow the rules in Annex\ D
of Recommendation\ G.821\ [1].
.RT
.sp 1P
.LP
3.5
\fIUse of thresholds\fR
.sp 9p
.RT
.PP
The general strategy for the use of performance monitoring
information and thresholds is described in Recommendation\ M.34. It is
expected that these thresholds and information will be reported to operations
systems
via the TMN for both real time and longer term analysis. When thresholds of
unacceptable or degraded performance level are reached [e.g.\ prompt
maintenance alarm (PMA) or deferred maintenance alarm (DMA)], maintenance
action should be initiated independently of the performance measurement.
Other thresholds may be used for maintenance and longer term quality analysis.
The
operations systems will use real time processing to assign maintenance
priorities to these thresholds and information, using the performance
supervision process described in Recommendation\ M.20.
.bp
.RT
.LP
.rs
.sp 31P
.ad r
\fBFigure 2/M.550, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB4\fR \fBParameters for performance limits\fR
.sp 1P
.RT
.PP
The basic performance parameters to be estimated are ES, SES, and DM as
defined in Recommendation\ G.821\ [1]. This allows measurement of the
unavailability of digital paths, sections, and line sections and of their
performance. These parameters are measured using the concepts of anomalies
and defects defined in Recommendation\ M.20 as shown in Figure\ 3/M.550.
.RT
.sp 1P
.LP
4.1
\fIBasic performance parameters\fR
.sp 9p
.RT
.PP
The basic performance parameters are the following:
.RT
.LP
\(em
\fIErrored seconds (ES)\fR
.LP
An errored second is a second with at least one anomaly or
defect.
.LP
\(em
\fISeverely errored seconds (SES)\fR
.LP
A severely errored second is a second with a binary error ratio
(BER) [as can be measured using a quasi\(hyrandom signal source (QRSS)] greater
than or equal to 10\uD\dlF261\u3\d or at least one defect (except slips).
.LP
A pseudo\(hyseverely errored second is a second with at least N1
anomalies (when the anomaly is not a binary error, i.e.\ when it is an error
indicator such as a code violation, CRC error,\ etc.) or one defect (except
slips). The value of N1 is an estimator defined to correspond to a BER
of\ 10\uD\dlF261\u3\d in one second. N1 is a function of the accuracy and
efficiency of the anomaly detectors.
.bp
.LP
\(em
\fIDegraded minutes (DM)\fR
.LP
A degraded minute is a group of 60 consecutive seconds, after
excluding SES, with a BER of\ 10\uD\dlF261\u6\d or worse.
.LP
A pseudo\(hydegraded minute is a group of 60 consecutive seconds,
after excluding SES, with at least N2 anomalies or at least one slip (when
the anomaly is not a binary error). N2 is calculated similarly to N1, to
detect a BER of\ 10\uD\dlF261\u6\d in one minute.
.PP
Two techniques used to make these measurements are QRSS and
performance monitoring.
.LP
.rs
.sp 40P
.ad r
\fBFigure 3/M.550, p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
4.2
\fIMeasurements using a QRSS\fR
.sp 9p
.RT
.PP
When a QRSS is used to measure the basic performance for bringing into
service or maintenance, the anomalies and defects detected by the
measuring equipment are defined below.
.bp
.RT
.sp 1P
.LP
4.2.1
\fIAnomalies\fR
.sp 9p
.RT
.PP
Bit errors are the only types of anomalies detected by a QRSS
measurement.
.RT
.sp 1P
.LP
4.2.2
\fIDefects\fR
.sp 9p
.RT
.PP
Loss of signal and loss of synchronization are the types of defects detected
by a QRSS measurement.
.RT
.sp 1P
.LP
4.3
\fIMeasurements using performance monitoring\fR
.sp 9p
.RT
.PP
When performance monitoring is used to estimate the basic
performance parameters for maintenance, the anomalies and defects detected
by network elements (NEs) are defined below. DM may be calculated in NEs
or in an operations system.
.RT
.sp 1P
.LP
4.3.1
\fIAnomalies\fR
.sp 9p
.RT
.PP
Anomalies detected by NEs include the following:
.RT
.LP
a)
Bit error indicators:
.LP
\(em
code violations,
.LP
\(em
CRC errors,
.LP
\(em
frame alignment signal errors,
.LP
\(em
block parity errors.
.LP
b)
Loss of signal energy (possibly brief).
.PP
The probability of error detection must be specified for both
Poisson and bursty error models. The efficiency (detected errors/actual
errors) of the information generated will be taken into account in the
establishment of the basic performance parameters.
.FS
Further study is needed to relate these anomalies to the performance parameters
specified in Recommendation\ G.821\ [1], taking into account error distributions,
e.g.\ Poisson and bursty, and
algorithms for estimating performance parameter values from observed anomalies.
This study needs to be coordinated with Working Party\ IV/2 and with Study
Groups\ XV and\ XVIII.
.FE
.sp 1P
.LP
4.3.2
\fIDefects\fR
.sp 9p
.RT
.PP
Defects include the following parameters generated by the
equipment:
.RT
.LP
\(em
loss of frame alignment (or loss of synchronisation);
.LP
\(em
loss of signal;
.LP
\(em
alarm indication signal (AIS);
.LP
\(em
alarm information to the remote end;
.LP
\(em
slips;
.LP
\(em
restoration indication signal (under study).
.PP
Loss of frame alignment is defined in G.704 [10] and AIS and alarm information
to the remote end are defined in Recommendation\ M.20, \(sc\ 5.4. A
string of \fIN\fR\d\fIi\fR\uzeros at bit rate\ \fIi\fR will be considered
a loss of signal.
The value of\ \fIN\fR\d\fIi\fR\uis for further study.
.sp 2P
.LP
\fB5\fR \fBPerformance limits\fR
.sp 1P
.RT
.PP
Performance limits are expressed by the number of events in the
specified time interval, not by the percent of time.
.PP
The tables are entered using the percent allocation of the overall
objective that applies to the entity in question. These reference performance
objectives are defined in \(sc\ 2. They are calculated as follows:
.RT
.sp 1P
.ce 1000
Reference performance objective = duration\ \(mu\ allocation\ \(mu\ objective
.ce 0
.sp 1P
.sp 2P
.LP
\fB6\fR \fBBringing\(hyinto\(hyservice and maintenance limits for digital line
sections\fR
.sp 1P
.RT
.PP
The particular allocations given in Tables 4/M.550 and 5/M.550 are for
the 2\ Mbit/s hierarchy. No similar allocations exist for the 1.5\ Mbit/s
hierarchy.
.bp
.PP
The duration of the test indicated in the tables is for example
only and requires further study. It should be noted that some Administrations
use one duration (e.g.\ on the order of days) for the test of the first
digital section in a block and a shorter duration (e.g.\ on the order of
hours) for the remaining sections in that block that are brought into service
within a few
weeks. The possibility of using shorter test durations in those cases when
in\(hyservice performance monitoring will be used following the
bringing\(hyinto\(hyservice test is an area for further study.
.RT
.ce
\fBH.T. [T4.550]\fR
.ce
TABLE\ 4/M.550
.ce
\fBBringing\(hyinto\(hyservice limits for 64\ kbit/s digital line
.ce
sections\fR
.ce
| ua\d\u)\d
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) , ^ | c | c | c | c | c | c | c | c | c.
Allocation (%) {
Reference performance
objective
Events/4 days
} S1 limit Events/4 days S2 limit Events/4 days
ES SES DM ES SES DM ES SES DM
_
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
0.45 \ 124 \ 2 \ 3 \ 12 0 0 \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(60p) .
2.0\ \ 553 \ 7 12 \ 55 1 1 For further study
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
5.0\ 1382 17 29 138 2 3 \fB\(em\fR \fB\(em\fR \fB\(em\fR
.TE
.LP
\ua\d\u)\d
The bit rate translation rules of Annex\ D of
Recommendation\ G.821 | 1] must be applied to the measurements made
at the entity rate in order to establish a comparison with the limits
outlined in this table.
.LP
\fINote\fR
\ \(em\ The values in this table are for example only.
.nr PS 9
.RT
.ad r
\fBTable 4/M.550 [T4.550], p.\fR
.sp 1P
.RT
.ad b
.RT
.ce
\fBH.T. [T5.550]\fR
.ce
TABLE\ 5/M.550
.ce
\fBMaintenance limits for 64 kbit/s digital line sections\fR
.ce
| ua\d\u)\d
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) , ^ | c | c | c | c | c | c | c | c | c.
Allocation (%) {
Reference performance
objective
Events/24 hours
} {
Unacceptable limit
Events/15 minutes
} {
Degraded limit
Events/24 hours
}
ES SES DM ES SES DM ES SES DM
_
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
0.45 \ 31 0 1 \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(60p) | cw(60p) .
2.0\ 138 2 3 For further study For further study
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
5.0\ 346 4 7 \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR
.TE
.LP
\ua\d\u)\d
The bit rate translation rules of Annex\ D of
Recommendation\ G.821 | 1] must be applied to the measurements made
at the entity rate in order to establish a comparison with the limits
outlined in this table.
.LP
\fINote\fR
\ \(em\ The values in this table are for example only.
.nr PS 9
.RT
.ad r
\fBTable 5/M.550 [T5.550], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
6.1
\fIPerformance limits for digital line sections at other rates\fR
.sp 9p
.RT
.PP
Performance limits for digital line sections at other rates,
e.g.\ 1.5, 2, 6, 8, 32, 45, 97 and 140\ Mbit/s are for further study.
.bp
.RT
.sp 2P
.LP
\fB7\fR \fBBringing\(hyinto\(hyservice and maintenance limits for digital
sections\fR
.sp 1P
.RT
.PP
The limits are shown in Tables 6/M.550 and 7/M.550.
.PP
The duration of the test indicated in the tables is for example only and
requires further study. It should be noted that some Administrations use
one duration (e.g.\
on the order of days) for the test of the first digital
section in a block and a shorter duration (e.g.\ on the order of hours)
for the remaining sections in that block that are brought into service
within a few
weeks. The possibility of using shorter test durations in those cases when
in\(hyservice performance monitoring will be used following the
bringing\(hyinto\(hyservice test is an area for further study.
.RT
.ce
\fBH.T. [T6.550]\fR
.ce
TABLE\ 6/M.550
.ce
\fBBringing\(hyinto\(hyservice limits for 64\ kbit/s digital paths and
.ce
sections\fR
.ce
| ua\d\u)\d
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) , ^ | c | c | c | c | c | c | c | c | c.
Allocation (%) {
Reference performance
objective
Events/3 days
} S1 limit Events/3 days S2 limit Events/3 days
ES SES DM ES SES DM ES SES DM
_
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 1 \ 207 \ 3 \ 4 104 1 \ 2 \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 2 \ 415 \ 5 \ 9 207 3 \ 4 \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(60p) .
\(= 3 \ 622 \ 8 13 311 4 \ 6 For further study
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 4 \ 829 10 17 415 5 \ 9 \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 5 1037 13 22 518 6 11 \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 6 1244 16 26 622 8 13 \fB\(em\fR \fB\(em\fR \fB\(em\fR
.TE
.LP
\ua\d\u)\d
The bit rate translation rules of Annex\ D of
Recommendation\ G.821 | 1] must be applied to the measurements made
at the entity rate in order to establish a comparison with the limits
outlined in this table.
.LP
\fINote\fR
\ \(em\ The values in this table are for example only.
.nr PS 9
.RT
.ad r
\fBTable 6/M.550 [T6.550], p.\fR
.sp 1P
.RT
.ad b
.RT
.ce
\fBH.T. [T7.550]\fR
.ce
TABLE\ 7/M.550
.ce
\fBMaintenance limits for 64 kbit/s digital sections\fR
.ce
| ua\d\u)\d
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) , ^ | c | c | c | c | c | c | c | c | c.
Allocation (%) {
Reference performance
objective
Events/24 hours
} {
Unacceptable limit
Events/15 minutes
} {
Degraded limit
Events/24 hours
}
ES SES DM ES SES DM ES SES DM
_
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 1 \ 69 1 1 \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 2 138 2 3 \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(60p) | cw(60p) .
\(= 3 207 3 4 For further study For further study
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 4 276 4 6 \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 5 346 4 7 \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 6 415 5 8 \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR
.TE
.LP
\ua\d\u)\d
The bit rate translation rules of Annex\ D of
Recommendation\ G.821 | 1] must be applied to the measurements made
at the entity rate in order to establish a comparison with the limits
outlined in this table.
.LP
\fINote\fR
\ \(em\ The values in this table are for example only.
.nr PS 9
.RT
.ad r
\fBTable 7/M.550 [T7.550], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
7.1
\fIPerformance limits for digital sections at other rates\fR
.sp 9p
.RT
.PP
Performance limits for digital sections at other rates, e.g.\ 1.5, 2, 6,
8, 32, 34, 45, 97 and 140\ Mbit/s are for further study.
.RT
.sp 2P
.LP
\fB8\fR \fBBringing\(hyinto\(hyservice and maintenance limits for digital
paths\fR
.sp 1P
.RT
.PP
Bringing\(hyinto\(hyservice limits for digital paths are the same as
those for digital sections, as shown in Table\ 6/M.550. The maintenance
limits are given in Table\ 8/M.550.
.RT
.ce
\fBH.T. [T8.550]\fR
.ce
TABLE\ 8/M.550
.ce
\fBMaintenance limits for 64 kbit/s digital paths\fR
.ce
| ua\d\u)\d
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) , ^ | c | c | c | c | c | c | c | c | c.
Allocation (%) {
Reference performance
objective
Events/24 hours
} {
Unacceptable limit
Events/15 minutes
} {
Degraded limit
Events/24 hours
}
ES SES DM ES SES DM ES SES DM
_
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 2.5 173 2 4 \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 3.5 242 3 5 \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(60p) | cw(60p) .
\(= 4\fB,\ \fR 276 4 6 For further study For further study
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 5.5 380 5 8 \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 6\fB.\ \fR 415 5 9 \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR \fB\(em\fR
.TE
.LP
\ua\d\u)\d
The bit rate translation rules of Annex\ D of
Recommendation\ G.821 | 1] must be applied to the measurements made
at the entity rate in order to establish a comparison with the limits
outlined in this table.
.LP
\fINote\fR
\ \(em\ The values in this table are for example only.
.nr PS 9
.RT
.ad r
\fBTable 8/M.550 [T8.550], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
8.1
\fIPerformance limits for digital paths at other rates\fR
.sp 9p
.RT
.PP
Performance limits for digital paths at other rates, e.g.\ 1.5, 2, 6, 8,
32, 34, 45, 97 and 140\ Mbit/s are for further study.
.RT
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation M.550)
.sp 9p
.RT
.ce 0
.ce 1000
\fBExample performance limits\fR
.sp 1P
.RT
.ce 0
.LP
A.1
\fICalculation of performance limits\fR
.sp 1P
.RT
.PP
The values in the following tables are for example only.
.PP
The reference performance objectives are calculated as specified in
\(sc\ 5. For example, the first three numbers in Table\ 4/M.550 are calculated
as
follows:
.RT
.LP
Number of ES
=\ 4 days \(mu 24 \(mu 60 \(mu 60 \(mu 0.0045 \(mu 0.08 = 124
.LP
Number of SES
=\ 4 days \(mu 24 \(mu 60 \(mu 60 \(mu 0.0045 \(mu 0.001 = 2
.LP
Number of DM
=\ 4 days \(mu 24 \(mu 60 \(mu 0.0045 \(mu 0.10 = 3
.bp
.PP
The value of S1 is calculated as specified in \(sc\ 3.2.2. For
example, the first three values in Table\ 4/M.550 are calculated as follows:
.LP
Number of ES
=\ 0.1 \(mu Reference performance objective = 12
.LP
Number of SES
=\ 0.1 \(mu Reference performance objective = 0.16 | ( = |
.LP
Number of DM
=\ 0.1 \(mu Reference performance objective = 0.26 | ( = |
.PP
The value of S2 is calculated from S1 by applying a statistical
parameter.
.PP
The values for unacceptable and degraded performance limits are
calculated from the values specified in \(sc\(sc\ 3.2.3.1 and\ 3.2.3.2
and include
confidence limit in addition.
.PP
It is expected that the maintenance limits will be used as thresholds for
continuous in\(hyservice performance monitoring. One crossing of these
thresholds (e.g.\ after exceeding the limits specified in Table\ A\(hy2/M.550
for
24\ hours) would not necessarily generate information requiring human response.
Rather, as noted in the footnote to Figure\ 2/M.550, it would be an input
to the alarm information process, which would collect inputs until a representative
value has been reached (which may occur over several days) and then process
such values and generate alarm information requiring human response at the
apropriate time.
.RT
.sp 1P
.LP
A.2
\fIExample of bringing\(hyinto\(hyservice and maintenance limits for
digital\fR \fIline sections\fR
.sp 9p
.RT
.PP
The values of Tables A\(hy1/M.550 and A\(hy2/M.550 are measured at the
rate of the digital sections and referred to the 64\ kbit/s rate using
Annex\ D of Recommendation\ G.821\ [1].
.RT
.ce
\fBH.T. [T9.550]\fR
.ce
TABLE\ A\(hy1/M.550
.ce
\fBExample of bringing\(hyinto\(hyservice limits for 64 kbit/s digital
.ce
line sections\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) , ^ | c | c | c | c | c | c | c | c | c.
Allocation (%) {
Reference performance
objective
Events/4 days
} S1 limit Events/4 days S2 limit Events/4 days
ES SES DM ES SES DM ES SES DM
_
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
0.45 \ 124 \ 2 \ 3 \ 12 0 0 \ 25 1 1
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
2.0\ \ 553 \ 7 12 \ 55 1 1 \ 75 2 2
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
5.0\ 1382 17 29 138 2 3 175 4 6
_
.TE
.nr PS 9
.RT
.ad r
\fBTable A\(hy1/M.550 [T9.550], p.\fR
.sp 1P
.RT
.ad b
.RT
.ce
\fBH.T. [T10.550]\fR
.ce
TABLE\ A\(hy2/M.550
.ce
\fBExample of maintenance limits for 64 kbit/s digital line
.ce
sections\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) , ^ | c | c | c | c | c | c | c | c | c.
Allocation (%) {
Reference performance
objective
Events/24 hours
} {
Unacceptable limit
Events/15 minutes
} {
Degraded limit
Events/24 hours
}
ES SES DM ES SES DM ES SES DM
_
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
0.45 \ 31 1 1 50 10 10 \ 30 1 1
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
2.0\ 138 2 3 50 10 10 \ 90 2 3
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
5.0\ 346 4 7 50 10 10 200 5 8
_
.TE
.nr PS 9
.RT
.ad r
\fBTable A\(hy2/M.550 [T10.550], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
A.3
\fIExample of bringing\(hyinto\(hyservice and maintenance limits for
digital\fR \fIsections\fR
.sp 9p
.RT
.PP
The values of Tables A\(hy3/M.550 and A\(hy4/M.550 are measured at the
rate of the digital sections and referred to the 64\ kbit/s using Annex\ D of
Recommendation\ G.821\ [1].
.RT
.ce
\fBH.T. [T11.550]\fR
.ce
TABLE\ A\(hy3/M.550
.ce
\fBExample of bringing\(hyinto\(hyservice limits for 64 kbit/s digital
paths and sections\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) , ^ | c | c | c | c | c | c | c | c | c.
Allocation (%) {
Reference performance
objective
Events/3 days
} S1 limit Events/3 days S2 limit Events/3 days
ES SES DM ES SES DM ES SES DM
_
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 1 \ 207 \ 3 \ 4 104 1 \ 2 130 \ 2 \ 3
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 2 \ 415 \ 5 \ 9 207 3 \ 4 250 \ 4 \ 6
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 3 \ 622 \ 8 13 311 4 \ 6 360 \ 6 \ 9
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 4 \ 829 10 17 415 5 \ 9 470 \ 7 12
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 5 1037 13 22 518 6 11 580 \ 9 15
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 6 1244 16 26 622 8 13 690 11 18
_
.TE
.nr PS 9
.RT
.ad r
\fBTable A\(hy3/M.550 [T11.550], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 8
.ce
\fBH.T. [T12.550]\fR
.ce
TABLE\ A\(hy4/M.550
.ce
\fBExample of maintenance limits for 64 kbit/s
.ce
digital sections\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) , ^ | c | c | c | c | c | c | c | c | c.
Allocation (%) {
Reference performance
objective
Events/24 hours
} {
Unacceptable limit
Events/15 minutes
} {
Degraded limit
Events/24 hours
}
ES SES DM ES SES DM ES SES DM
_
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 1 \ 69 1 1 100 12 12 \ 51 2 \ 2
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 2 138 2 3 100 12 12 103 3 \ 4
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 3 207 3 4 100 12 12 155 4 \ 6
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 4 276 4 6 100 12 12 207 5 \ 8
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 5 346 4 7 100 12 12 259 6 10
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 6 415 5 9 100 12 12 311 7 12
_
.TE
.nr PS 9
.RT
.ad r
\fBTable A\(hy4/M.550 [T12.550], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
A.4
\fIExample of bringing\(hyinto\(hyservice and maintenance limits for
digital\fR \fIpaths\fR
.sp 9p
.RT
.PP
The bringing\(hyinto\(hyservice limits for digital paths are the same as
those for digital sections, as shown in Table\ A\(hy3/M.550.
.PP
The values of Table A\(hy5/M.550 are usually measured at the primary rate
and referred to the 64\ kbit/s rate using Annex\ D to
Recommendation\ G.821\ [1].
.RT
.ce
\fBH.T. [T13.550]\fR
.ce
TABLE\ A\(hy5/M.550
.ce
\fBExample of maintenance limits for 64 kbit/s
.ce
digital paths\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(48p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) | cw(22p) sw(22p) sw(16p) , ^ | c | c | c | c | c | c | c | c | c.
Allocation (%) {
Reference performance
objective
Events/24 hours
} {
Unacceptable limit
Events/15 minutes
} {
Degraded limit
Events/24 hours
}
ES SES DM ES SES DM ES SES DM
_
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 2.5 173 2 4 120 15 15 130 2 3
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 3.5 242 3 5 120 15 15 181 3 4
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 4\fB.\ \fR 276 4 6 120 15 15 207 4 5
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 5.5 380 5 8 120 15 15 285 5 6
.T&
cw(48p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) | cw(22p) | cw(22p) | cw(16p) .
\(= 6\fB.\ \fR 415 5 9 120 15 15 311 6 7
_
.TE
.nr PS 9
.RT
.ad r
\fBTable A\(hy5/M.550 [T13.550], p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.sp 5
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIError performance of an international digital\fR
\fIconnection forming part of an integrated services digital network\fR
, Vol.\ III, Rec.\ G.821.
.LP
[2]
CCITT Recommendation \fIControlled slip rate objectives on an\fR
\fIinternational digital connection\fR , Vol.\ III, Rec.\ G.822.
.LP
[3]
CCITT Recommendation \fIThe control of jitter and wander within digital\fR
\fInetworks which are based on the 2048\ kbit/s hierarchy\fR Vol.\ III,
Rec.\ G.823.
.LP
[4]
CCITT Recommendation \fIThe control of jitter and wander within digital\fR
\fInetworks which are based on the 1544\ kbit/s hierarchy\fR , Vol.\ III,
Rec.\ G.824.
.LP
[5]
CCITT Recommendation \fIISDN user\(hynetwork interfaces \(em Interface\fR
\fIstructures and access capabilities\fR , Vol.\ III, Rec.\ I.412.
.LP
[6]
CCITT Recommendation \fIDigital hierarchy bit rates\fR , Vol.\ III,
Rec.\ G.702.
.LP
[7]
CCITT Recommendation \fIDigital transmission models\fR , Vol.\ III,
Rec.\ G.801.
.LP
[8]
CCITT Recommendation \fIDigital sections based on the 2048 kbit/s\fR
\fIhierarchy\fR , Vol.\ III, Rec.\ G.921.
.LP
[9]
CCITT Recommendation \fIDigital line sections at 1544 kbit/s\fR , Red
Book, Vol.\ III, Rec.\ G.911, ITU, Geneva,\ 1984.
.LP
[10]
CCITT Recommendation \fIFunctional characteristics of interfaces\fR
\fIassociated with network nodes\fR , Vol.\ III, Rec.\ G.704.
.bp
.sp 2P
.LP
\fBRecommendation\ M.555\fR
.RT
.sp 2P
.ce 1000
\fBBRINGING\ INTERNATIONAL\ DIGITAL\ BLOCKS,\ PATHS\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.555''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.555 %'
.ce 0
.sp 1P
.ce 1000
\fBAND\ SECTIONS\ INTO\ SERVICE\fR
.FS
The
procedures for introducing services using digital satellite systems are not
covered in this Recommendation. This matter is for further study for Study
Group\ IV.
.FE
.ce 0
.sp 1P
.LP
\fB1\fR \fBPreliminary exchange of information\fR
.sp 1P
.RT
.PP
The technical services concerned nominate the control and
sub\(hycontrol stations for the digital block, path or section to be brought
into operation in accordance with Recommendations\ M.80 and\ M.90.
.PP
The technical services should indicate the routing to be followed and the
method given in Recommendation\ M.570 may be applied.
.PP
Information necessary for the control station, which will be entered on a
\fIrouting form\fR is indicated below:
.RT
.LP
\(em
routing of the block, path or section,
.LP
\(em
names of control and sub\(hycontrol stations,
.LP
\(em
names of stations where the block or path appears at its
characteristic bit rate.
.PP
The overall routing form for an entire block or path is drawn up by the
control station on the basis of information furnished by its technical
service and by each sub\(hycontrol station for the sections for which the
latter is responsible.
.PP
\fINote\fR \ \(em\ When digital paths are used to provide the terrestrial
links to a time division multiple access (TDMA) satellite system, the usual
digital system supervisory signals (AIS, remote alarm,\ etc.) are not transmitted
over the satellite section. An alternative method of supervision for the
individual circuits is described in Recommendation\ Q.33.\ [1].
.PP
When the block or path is assigned its designation (according to
Recommendation\ M.140 \(sc\(sc\ 9 and\ 10), the Administration with control
station
responsibility
will assemble the necessary technical and operational information. This
should be entered into the list of related information (as defined in
Recommendation\ M.140, \(sc\ 12) which consists of the items shown in the
Annex\ A.
.RT
.sp 2P
.LP
\fB2\fR \fBDigital system arrangements\fR
.sp 1P
.RT
.sp 1P
.LP
2.1
\fIDigital hierarchy\fR
.sp 9p
.RT
.PP
The layout of the presently identified hierarchical digital bit
rates is given in Table\ 1/M.555, both for hierarchies based on 1544\ kbit/s
systems and for hierarchies based on 2048\ kbit/s systems.
.RT
.ce
\fBH.T. [T1.555], p.\fR
.ce
TABLE\ 1/M.555
.ce
\fBHierarchical bit rates\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(30p) | cw(60p) | cw(60p) .
Level 1544 kbit/s structure 2048 kbit/s structure
_
.T&
cw(30p) | cw(60p) | cw(60p) .
1 1544 \ \ 2 | 48
.T&
cw(30p) | cw(60p) | cw(60p) .
2 6312 \ \ 8 | 48
.T&
lw(10p) .
.T&
cw(30p) | lw(30p) | cw(30p) | cw(60p) .
3 32 | 64 44 | 36 \ 34 | 68
.T&
cw(30p) | lw(30p) | cw(30p) | cw(60p) .
4 97 | 28 Note 139 | 64
.TE
.LP
\fINote\fR
\ \(em\ Level 4 bit rates presently under study.
.nr PS 9
.RT
.ad r
\fBTable 1/M.555 [T1.555], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 1P
.LP
2.2
\fIDigital interworking\fR \fIarrangements\fR
.sp 9p
.RT
.PP
(The standard digital interworking arrangements presently under
study by Study Group\ XVIII will be shown when they are available).
.bp
.RT
.sp 2P
.LP
\fB3\fR \fBReference measurements for a path\fR
.sp 1P
.RT
.PP
The measurements described in \(sc\ 5.2 below for ensuring that the
digital path is within limits also constitute reference measurements. These
data should be recorded at every sub\(hycontrol station and at stations
adjacent to frontiers where the block or path appears at its characteristic
bit rate. On request, this data should be forwarded to the control station
which then can
draw up a record of reference measurements.
.RT
.LP
\fB4\fR \fBOrganization of the control of international digital blocks,\fR
\fBdigital paths, etc.\fR
.sp 1P
.RT
.sp 2P
.LP
4.1
\fIClasses of station\fR
.sp 1P
.RT
.PP
4.1.1
As far as international cooperation is concerned, only two
classes of
through\(hyconnection station
need to be designated by any
country:
.sp 9p
.RT
.LP
a)
stations which exercise control functions, i.e.,\ digital
block/digital path control stations and digital block/digital
path sub\(hycontrol stations;
.LP
b)
attended stations nearest the frontier, which in this
Recommendation are referred to as \fIfrontier stations\fR .
.PP
4.1.2
In accordance with Recommendations M.80 and M.90, the
station at each end of the digital block or digital path is the \fIcontrol\fR
\fIstation\fR for the receiving direction of transmission and the terminal
\fIsub\(hycontrol station\fR for the sending direction. Stations having control
functions in intermediate countries are digital block, digital path
intermediate sub\(hycontrol stations. Other stations involved in international
maintenance are frontier stations.
.PP
4.1.3
In general, a transit country will have one station with
control functions or one with sub\(hycontrol functions and two frontier
stations. A country in which the digital block or path terminates has only
one frontier station. In some countries, a station with control functions
or sub\(hycontrol
functions and a frontier station will be the same.
.sp 1P
.LP
4.2
\fIClasses of digital sections\fR
.sp 9p
.RT
.PP
For the purposes of setting\(hyup, making initial tests and
subsequent maintenance, an international digital path is subdivided into
national sections, international sections and main sections as defined in
Recommendation\ M.300. These terms are illustrated in Figure\ 1/M.555.
.RT
.LP
.rs
.sp 24P
.ad r
\fBFigure 1/M.555, p.\fR
.sp 1P
.RT
.ad b
.RT
.LP
.bp
.sp 1P
.LP
4.3
\fIOrganization of control functions\fR
.sp 9p
.RT
.PP
The terminal stations of each national, international and main
section will be appointed as a control or sub\(hycontrol station for that
class of section with which they are concerned. However, as a consequence
of the
definitions of national, international and main sections of a digital path,
some stations will be nominated for more than one control or sub\(hycontrol
function. For example, station\ S in Figure\ 1/M.555 is:
.RT
.LP
\(em
control station
for main section Q\(hyS,
.LP
\(em
sub\(hycontrol station
for main section S\(hyT,
.LP
\(em
control station for national section R\(hyS.
.LP
\fB5\fR \fBSetting up and initial testing of an international digital\fR
\fBpath\fR
.sp 1P
.RT
.sp 2P
.LP
5.1
\fISetting up the path\fR
.sp 1P
.RT
.PP
5.1.1
Once the route has been agreed, the (\fIn\fR \(hyth order)
digital path
control station will direct the operations needed to set up the
digital path.
.sp 9p
.RT
.PP
All the repeater stations concerned \(em i.e., the stations at the
ends of each digital section that will make up the digital path \(em should
make setting\(hyup tests and check the equipment to be used. The check
should include a general visual inspection and
vibration tests
, particularly if the
equipment has remained unused for some time since acceptance tests were
carried out after installation.
.PP
5.1.2
Each country sets up the national part within its territory, each international
digital section is set up by the stations at the ends of this
section in the two countries concerned (generally the frontier stations) and
these national and international sections are interconnected as may be
appropriate. The sub\(hycontrol stations inform the control station when each
interconnection is completed.
.sp 2P
.LP
5.2
\fIInitial testing of the digital path\fR
.sp 1P
.RT
.PP
5.2.1
The procedure for an international \fIn\fR \(hyth order digital path is
based on the progressive testing of its component sections as follows:
.sp 9p
.RT
.LP
i)
national and international sections which are then
interconnected to form main sections,
.LP
ii)
main sections which are then interconnected to form the
overall path,
.LP
iii)
overall path.
.PP
The setting\(hyup tests should include a quick test of the digital
error performance. The function of such a check is not to guarantee compliance
with performance objectives nor is it the testing of the system as part
of a
commissioning process (which might require measurement of margins), but
rather to detect any immediate problems instead of having the user do so.
Thus, it
is analogous to a continuity check of a circuit, not to a measurement of the
loss and noise of the circuit. The limits to apply are given in\ Table\
2/M.555.
.PP
For these tests, satellite paths should be considered to have an equivalent
length of 12 | 00\ km.
.PP
5.2.2
The following procedures should be used when making the tests
recommended in Table\ 2/M.555:
.LP
1)
All tests should be performed at a first order digital
connection point. Thus, tests of second order and other higher
bit rate digital systems must have the appropriate multiplexers
and demultiplexers in the test path. This ensures a complete
test of the path regardless of its bit rate.
.LP
2)
A test of digital path between two stations is set up by
connecting a QRSS (quasi\(hyrandom signal source) to the input
for the digital path at the transmitting station distribution
frame and connecting the output at the receiving station
distribution frame to a receive input of a test set such as
that described in Recommendation\ O.151\ [2].
.LP
3)
Tests may be one way in each direction or \*Qlooped\*U (combined
2\(hyway). If looped, then test equipment is required at only one
location, and the other end is arranged to be looped back
(output connected to the input at the distribution frame).
.bp
.LP
4)
Test equipment should have the features described in
Recommendation\ O.151\ [2]. Back\(hyto\(hyback tests of test equipment
should occasionally be performed (connect output to input on
the same test instrument) to test for locally generated errors
due to unfiltered a.c. power or station equipment interference.
In general, whenever possible, use protected d.c. power for all
test equipment.
.LP
5)
The results of error tests may be contaminated by events which
cause the test instrument to lose synchronization. In general,
all such \*Qlost sync\*U tests should be repeated.
.LP
6)
If the tests fail:
.LP
a)
Determine if some special circumstance was responsible for
a circuit interruption or high error rate. If it was,
repeat the test to verify that the circuit is working
correctly.
.LP
b)
If no special circumstance is found, an attempt should be
made to isolate the problem section for repair or
replacement. If the digital path starts to function
correctly during trouble isolation, repeat the original
test.
.LP
c)
For marginal failures (i.e.\ just a few counts over the
limit), the test should be repeated, but with the time
limit and the maximum allowable count doubled.
.ce
\fBH.T. [T2.555], p.\fR
.ps 9
.vs 11
.nr VS 11
.nr PS 9
.TS
center box;
cw(156p) .
TABLE\ 2/M.555
.T&
cw(156p) .
{
\fBQuick check test of digital error performance\fR
\fBfor digital section and paths at the primary rate\fR
\fB(Provisional)\fR
}
.T&
cw(48p) | cw(48p) | cw(60p) .
{
Effective distance (kilometres)
} {
Minimum test
duration
(in minutes)
} {
Maximum allowed counts | ua\d\u)\d
in errored seconds | ub\d\u)\d
}
_
.T&
cw(48p) | cw(48p) | cw(60p) .
\ \ | 00 15 \ \ 5
.T&
cw(48p) | cw(48p) | cw(60p) .
\ 1 | 00 15 \ 10
.T&
cw(48p) | cw(48p) | cw(60p) .
\ 2 | 00 15 \ 20
.T&
cw(48p) | cw(48p) | cw(60p) .
\ 4 | 00 15 \ 40
.T&
cw(48p) | cw(48p) | cw(60p) .
\ 8 | 00 15 \ 80
.T&
cw(48p) | cw(48p) | cw(60p) .
12 | 00 15 125
.T&
cw(48p) | cw(48p) | cw(60p) .
18 | 00 15 180
.T&
cw(48p) | cw(48p) | cw(60p) .
25 | 00 15 250
.TE
.LP
\ua\d\u)\d
Values relate to 1.5 or 2.0 Mbit/s and may be linearly
interpolated for other distances.
.LP
\ub\d\u)\d
For the meaning of the term \*Qerrored seconds\*U, see
Recommendation\ G.821 | 3].
.nr PS 9
.RT
.ad r
\fBTable 2/M.555 [T2.555], p.\fR
.sp 1P
.RT
.ad b
.RT
.sp 2P
.LP
\fB6\fR \fBSetting up lower\(hyorder sections after the initial testing
of\fR \fBthe higher\(hyorder paths\fR
.sp 1P
.RT
.PP
The different hierarchical orders of sections have to be set up in sequence.
.RT
.PP
6.1
Thus, when the digital path has been initially tested, each end of it is
connected to the appropriate digital multiplexing equipment and the
corresponding lower\(hyorder sections are then set up.
.sp 9p
.RT
.PP
6.2
In each case, the digital multiplexing equipment, before it is
connected to the ends of its associated path, must be checked and adjusted
to ensure that it meets CCITT Recommendations and other relevant specifications.
.PP
6.3
When the lower\(hyorder sections have been set up in the above
manner, they are interconnected as necessary to form paths, as described in
\(sc\ 5.1 above, and the appropriate path testing procedure as detailed
in \(sc\ 5.2
above, is then applied.
.bp
.ce 1000
ANNEX\ A
.ce 0
.ce 1000
(to Recommendation M.555)
.sp 9p
.RT
.ce 0
.ce 1000
\fBDesignation information of international digital blocks and paths\fR
.sp 1P
.RT
.ce 0
.LP
A.1
\fIDesignation\fR
.sp 1P
.RT
.PP
The designation is according to Recommendation\ M.140, \(sc\(sc\ 9
and\ 10.
.RT
.sp 1P
.LP
A.2
\fIRelated information\fR
.sp 9p
.RT
.PP
The additional information on digital blocks, etc. is covered by
the following items:
.RT
.LP
RI\ \ 1.
urgency for restoration;
.LP
RI\ \ 2.
terminal countries;
.LP
RI\ \ 3.
carriers' names;
.LP
RI\ \ 4.
control and subcontrol station(s);
.LP
RI\ \ 5.
fault report points;
.LP
RI\ \ 6.
routing;
.LP
RI\ \ 7.
association;
.LP
RI\ \ 8.
equipment information;
.LP
RI\ \ 9.
use;
.LP
RI\ 10.
transmission medium;
.LP
RI\ 11.
(empty item, use \*Q\(em\*U); only for the mixed
analogue/digital network: end\(hyto\(hyend information;
.LP
RI\ 12.
bit rate;
.LP
RI\ 13.
occupancy (for blocks);
.LP
RI\ 14.
actual number of channels (for primary blocks);
.LP
RI\ 15.
clocking information (for blocks);
.LP
RI\ 16.
direction of transmission (for unidirectional
blocks).
.PP
The various items will be dealt with in \(sc\ 12 of
Recommendation\ M.140.
.sp 2P
.LP
\fBReferences\fR
.sp 1P
.RT
.LP
[1]
CCITT Recommendation \fIProtection against the effects of faulty\fR
\fItransmission on groups and circuits\fR , Vol.\ VI, Rec.\ Q.33.
.LP
[2]
CCITT Recommendation \fIError performance measuring equipment for digital\fR
\fIsystems\fR , Vol.\ IV, Rec.\ O.151.
.LP
[3]
CCITT Recommendation \fIError performance of an international digital\fR
\fIconnection forming part of an integrated services digital network\fR
, Vol.\ III, Rec.\ G.821.
\v'6p'
.sp 2P
.LP
\fBRecommendation\ M.556\fR
.RT
.sp 2P
.ce 1000
\fBSETTING\ UP\ AND\ INITIAL\ TESTING\ OF\ DIGITAL\ CHANNELS\fR
.EF '% Fascicle\ IV.1\ \(em\ Rec.\ M.556''
.OF '''Fascicle\ IV.1\ \(em\ Rec.\ M.556 %'
.ce 0
.sp 1P
.ce 1000
\fBON\ AN\ INTERNATIONAL\ DIGITAL\ PATH\ OR\ BLOCK\fR
.ce 0
.sp 1P
.PP
The definition of a digital channel is given in
Recommendation\ M.300. Procedures in CCITT Recommendation\ M.555 for
bringing\(hyinto\(hyservice digital blocks and digital paths are adequate
to ensure satisfactory operation of digital channels which are provided
on the respective digital blocks or paths. No specific tests are required
for individual digital channels.
.sp 1P
.RT
.PP
Where digital channels are terminated at each end by mixed
analogue/digital terminals, Administrations may, with bilateral agreement,
choose to apply a procedure similar to that in CCITT Recommendation\ M.470,
to test from each audio input to each audio output. This procedure is
an alternative to the mixed analogue/digital terminal circuit section line\(hyup
procedure in CCITT Recommendation\ M.580.
.LP
.bp
.sp 2P
.LP
\fBMONTAGE: PAGE 334 = PAGE BLANCHE\fR
.sp 1P
.RT
.LP
.bp