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1991-12-30
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Recommendation E.425
INTERNAL AUTOMATIC OBSERVATIONS1)
1 Definitions
1.1 essential information (of internal automatic observations)
The answer seizure ratio (ASR) (see S 1.3) or answer bid ratio (ABR) (see
S 1.4), whichever is appropriate in terms of attempts, completed attempts and
percentage completed.
1.2 supplementary information (of internal automatic observations)
Information on signalling faults, subscriber behaviour and the network.
1.3 answer seizure ratio (ASR)
ASR gives the relationship between the number of seizures that result in
an answer signal and the total number of seizures. This is a direct measure of
the effectiveness of the service being offered and is usually expressed as a
percentage as follows:
ASR = eq \f( Seizures resulting in answer signal,Total seizures) x
100
Measurement of ASR may be made on a route or on a destination code basis.
1.4 answer bid ratio (ABR)
Gives the relationship between the number of bids that result in an answer
signal and the total number of bids.
ABR = eq \f( Bids resulting in answer signal,Total bids) x 100
ABR is expressed as a percentage and is a direct measure of the
effectiveness of traffic from the point of measurement. It is similar to ASR
except that it includes bids that do not result in a seizure.
2 Merits of internal automatic observations
The advantage of internal monitoring is that a large volume of records can
be collected. The large volume of data obtained from an internal observation
system allows day-to-d of network performance.
Daily analysis of this information has proven invaluable in trouble
detection, and, coupled with a good maintenance response, is
instrumental in providing the best possible quali y of service.2)
The disadvantage is that this method does not have the capability
of detecting tones or speech and therefore cannot present a
complete representation of all call dispositions.
To overcome this disadvantage Administrations are advised to
use Recommendation E.422 as well to supplement the data obtained
from internal automatic observations.
3 Time of observations
The results of all observations taken over the whole day should be
recorded.
4 Exchange of the results of observations
1) This Recommendation also applies in case external monitoring equipment is used when a
route is monitored constantly for all or a large (statistical significance) number of
calls. Refer to Recommendation E.421, S 2.4.
2) Using these techniques one can improve the quality of service even when no distinction
can be made between ring no answer, subscriber busy (or congestion indicated by
congestion tone) and recorded announcement.
3) The Administration supplying the data must indicate whether the ASR or ABR is
used.
Fascicle II.3 - Rec. E.425 PAGE1
4.1 The essential information3 ) should be exchanged monthly (preferably by
facsimile o all network analyses points of
those Administrations who are interested (the analyses points can
then make comparisons between different streams going to the same
destination). If information on ASR or ABR can be supplied
separately for direct routes and indirect routes via transit
countries, this should also be exchanged as being essential
information, including the name of the transit country involved.
4.2 With respect to supplementary data such as: signalling faults,
failures due to calling subscriber, failures due to called
subscriber and failures due to the network, a quarterly exchange of
information is appropriate. Because different formats will be
required, mail seems the most likely means to be used for
exchanging supplementary data.
4.3 Besides the monthly and quarterly exchange of information, a
direct contact on all aspects should be made (by telephone) as soon
as action is required to prevent a persistent drop in the quality
of service.
5 Classes of calls
The distinction between classes of calls (such as operator-operator,
subscriber-subscriber and operator-subscriber) is considered useful in
identifying problems relating to the quality of service. This can only be done if
the language digit4) and some of the subsequent digits are analyzed.
6 Destination analysis from service observation data
Consideration should be given to include the dialled digits, as observed
by the monitoring equipment, in the exchange of information, especially for the
sake of destination analyses (see Recommendation E.420, Annex A).
7 Details about supplementary information for CCITT Signalling System No. 5
7.1 Signalling faults
- faulty signals;
- time outs, the main item in this category being no proceed-to-send
signal;
- busy flash. (Since busy flash is applied in many situations, including
failures due to calling and called subscriber and the network, it is
considered useful to between busy flash
received within 0-15 seconds, 15-30 seconds and after 30
seconds when making destination analysis.)
7.2 Ineffective calls associated with the calling subscriber
Premature rel to distinguish between release
before or after having received ringing tone; equipment
which can detect audible signals is required.
7.3 Ineffective calls associated with the called subscriber
Ringing tone no answer cannot be detected without equipment which can
detect audible signals.
7.4 Network
Here only the busy flash can be detected without equipment which can
detect audible signals.
8 Equipment impact
8.1 Administrations are recommended to consider inclusion of appropriate
facilities in existing and new exchanges to record all or some of the following
phases:
a) Calls switched to speech position, then:
1) answered;
2) unanswered, but released by calling party;
3) timed out awaiting answer;
call failure signal (busy flash or
equivalent) received;
4) Th discrimination digit is inserted
automatically, or by the operator, between the country code
(Recommendation E.161) and the national (significant) number.
PAGE4 Fascicle II.3 - Rec. E.425
5) timed out after clearback signal ;
6) faulty signal received after answer.
b) Calls failing to switch to speech position:
1) clear forward signal received;
2) insufficient digits received;
3) congestion on international circuits;
4) faulty signals received into exchange;
5) signalling fault into next exchange;
6) time out while signalling to next exchange;
7) congestion signal received from next exchange;
8) vacant number received;
9) busy subscriber signal received;
10) line out of order signal
received;
11) transferred subscriber signal
received.
As a minimum requirement one should be capable of determining the answer
seizure r o (ASR) or the answer bid ratio
(ABR). This recording can be done by off-line
processing of call records if they contain some more information
than the information already required for international accounting.
8.2 Another way to assemble date on the quality of service (QOS)
on outgoing circuit groups is through event counters. Five event
counters already give a reasonable amount of information, three of
them being common to the Signalling Systems No. 5, No. 6 and R2:
seizure, answer and busy signals5).
Signalling System No. 5
The number of:
- seizing signals sent;
- end-of-pulsing (ST) signals sent;
- proceed-to-send signals received;
- busy flash signals received;
- answer signals received.
Signalling System No. 6
The number of:
- initial address messages (IAM) sent;
- congestion (switching-equipment; circuit groups; national network)
signals, call-failure signals and confusion signals received;
- address-complete (subscriber-free, charge; subscriber-free, no charge;
subscriber-free, coinbox; charge; no charge; coinbox) signals received;
- subscriber busy signals received;
- answer (charge; no charge) signals received.
Signalling System R2
The number of:
- seizing signals sent;
- congestion [national network (A4 or B4); international exchange (A15)]
signals received;
- address complete (charge; subscriber's line free, charge; subscriber's
line free, no charge) signals received;
- subscriber line busy signals received;
- answer signals received.
5) In case the event counting is used to analyze the quality of service to a particular
destination, the counting should be done separately for each signalling system.
Fascicle II.3 - Rec. E.425 PAGE1
PAGE4 Fascicle II.3 - Rec. E.425