1、INTERNATIONAL TELECOMMUNICATION UNION ITU-T TELECOM M UN I CAT ION STANDARDIZATION SECTOR OF ITU E.451 (02/2001) SERIES E: OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS Network management - Checking the quality of the international telephone service Facsimile call
2、 cut-off performance ITU-T Recommendation E.451 (Formerly CCIlT Recommendation) ITU-T E-SERIES RECOMMENDATIONS OVERALL NETWORK OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS INTERNATIONAL OPERATION Definitions General provisions concerning Administrations General provisions concer
3、ning users Operation of international telephone services Numbering plan of the international telephone service International routing plan Tones in national signalling systems Numbering plan of the international telephone service Maritime mobile service and public land mobile service OPERATIONAL PROV
4、ISIONS RELATING TO CHARGING AND ACCOUNTING IN THE INTERNATIONAL TELEPHONE SERVICE Charging in the international telephone service Measuring and recording call durations for accounting purposes UTILIZATION OF THE INTERNATIONAL TELEPHONE NETWORK FOR NON- TELEPHONY APPLICATIONS General Phototelegraphy
5、ISDN PROVISIONS CONCERNING USERS INTERNATIONAL ROUTING PLAN NETWORK MANAGEMENT International service statistics International network management Checking the quality of the international telephone service Measurement and recording of traffic Forecasting of traffic Determination of the number of circ
6、uits in manual operation Determination of the number of circuits in automatic and semi-automatic operation Grade of service Definitions Traffic engineering for IP-networks ISDN traffic engineering Mobile network traffic engineering TRAFFIC ENGINEERING QUALITY OF TELECOMMUNICATION SERVICES: CONCEPTS,
7、 MODELS, OBJECTIVES AND DEPENDABILITY PLANNING Terms and definitions related to the quality of telecommunication services Models for telecommunication services Objectives for quality of service and related concepts of telecommunication services Use of quality of service objectives for planning of te
8、lecommunication networks Field data collection and evaluation on the performance of equipment, networks and services E.100-E.103 E. 104-E. 1 19 E. 120-E. 139 E.140-E.159 E. 160-E. 169 E. 170-E. 179 E.180-E. 189 E.190-E.199 E.200-E.229 E.230-E.249 E.260-E.269 E.300-E.3 19 E.320-E.329 E.330-E.349 E.35
9、0-E.399 E.400-E.409 E.4 10-E.4 19 E.420-. users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid ITU-T Recommandations is regularly published. - -
10、 - - ITU-T E.450 (1998), Facsimile qualily of service on public networks - General aspects. ITU-T E.456 (1998), Test transaction for facsimile transmission performance. ITU-T E.457 (1996), Facsimile measurement methodologies. ITU-T E.460 (2000), Measurements and metrics for monitoring the performanc
11、e of V.34 Group 3 Facsimile. ITU-T T.30 (1999), Procedures for document facsimile transmission in the general switched telephone network. - 3 Scope The definitions in clause 4 below apply to test calls: a) that use automatic-to-automatic scenario (method No. 4 in Table 1T.30) and may be adapted for
12、other methods in the same table; b) that use standard test transactions as defined in ITU-T E.456. cl where the intended receiving facsimile terminal has responded by going off-hook and CED has been received at the originating terminal see clause 5e)l; ITU-T E.451 (02/2001) 1 d) that are sent to a r
13、eceiving facsimile terminal that is connected to a dedicated line and not shared with voice terminals. 4 Definitions This Recommendation defines the following terms: a) A pre-message phase B failure is considered to have occurred if prior to the transmittal of the first page, either the originating
14、or the terminating facsimile terminal goes on-hook prior to the reception of a CFR message by the originating terminal. A post-message phase B failure is considered to have occurred if a phase B failure occurs after the transmission of any page. A phase C/phase D failure at any page is considered to
15、 have occurred if a valid post message response (MCF, RTP, RTN, PIN, PIP) is not received in response to either the MPS or the EOP message. If this occurs at mth page, then rn- 1 pages are considered to be successfully transmitted but one can consider that there was a failure at the mth page. When t
16、ransmitting N-page transactions, the facsimile call cut-off ratio (expressed as a percentage) for N pages is b) c) %CN = (FN / T) x 100 where FN is the number of transactions where there was either a phase B, C, or D failure, and T is the total number of transactions satisfying the conditions in cla
17、use 3. Based on the definition in item c) above, facsimile call cut-off ratios for m pages (1imcN)is d) %Cm = (Fm / T) x 100 where Fm is the number of transactions that had a phase B, C or D failure at the mth page. The cut-off ratio for transactions for which a pre-message phase B failure occurs is
18、 e) %ClB = (FIB / T) X 100 where FIB is the number of transactions with a pre-picture phase B failure. Given that conditions a) to d) in clause 3 have been satisfied, it is possible to define conditional facsimile success (CFS) ratios which are the complements of cutoff ratios: %CFSN = 100 - %CN f)
19、%CFSm= 100 - %Cm %CFSB = 100 - %c1B g) End-to-end facsimile success (FS) ratios can be defined as follows: %FSN = PACR x %CFSN %FSm = PACR x %CFSm %FSB = PACR x %CFSB The FSs represent the true facsimile success performance observed by the customers. The ratio PACR is the phase A completion ratio an
20、d is dependent on several factors. These factors include network blocking, terminal availability, proper operation of the terminating facsimile terminal and correct reception of the CED signal by the originating terminal. 2 ITU-T E.451 (02/2001) 5 Remarks a During test calls, retransmissions of page
21、s may occur. The retransmitted pages are not counted for computing call cut-off ratios. For example, if retransmissions occur prior to the mth page of the original document followed by a failure at the mth page, it is still counted as a cut-off at the mth page. A test transaction of 3 pages as defin
22、ed in JTU-T E.456 shall be used. For manual to automatic test calls (method No. 2 in Table 1lT.30) there are no changes in definitions contained in clause 4 provided that there are no operator errors. From a measurement point of view, the precise evaluation of cut-off ratios CN requires that the T.3
23、0 HDLC protocol messages be monitored and recorded during test transactions. This should not be a problem for specially constructedkonfigured test vehicles or network based monitoring systems. If measurements are made between terminals from the same manufacturer that will result in the use of non-st
24、andard features, the possible impact of these features on cut-off ratios should be identified and understood. Machines from some manufacturers disconnect on the receipt of an RTN while others do not. In the presence of network impairments, machines that disconnect on the receipt of an RTN may result
25、 in a higher facsimile call cut-off ratio compared to those machines that do not disconnect on the receipt of an RTN. Therefore, it is important to explicitly state the characteristics of machines such as the response to RTNs when comparing the results from the different machines. b) cl d) e 0 ITU-T E.451 (02/2001) 3
