1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-0100507.2002(R2011) Network Performance Parameters for Circuit-Switched Digital Services Definitions and Measurements ATIS is the leading technical planning and standards development organization committed to the rapid development of global, ma
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5、D Approval of an American National Standard requires review by ANSI that the requirements for due process, consensus, and other criteria for approval have been met by the standards developer. Consensus is established when, in the judgment of the ANSI Board of Standards Review, substantial agreement
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8、s Institute does not develop standards and will in no circumstances give an interpretation of any American National Standard. Moreover, no person shall have the right or authority to issue an interpretation of an American National Standard in the name of the American National Standards Institute. Re
9、quests for interpretations should be addressed to the secretariat or sponsor whose name appears on the title page of this standard. CAUTION NOTICE: This American National Standard may be revised or withdrawn at any time. The procedures of the American National Standards Institute require that action
10、 be taken periodically to reaffirm, revise, or withdraw this standard. Purchasers of American National Standards may receive current information on all standards by calling or writing the American National Standards Institute. Notice of Disclaimer T1A1.3 Chair Henri Suyderhoud, OKI America, Incorpor
11、ated; T1A1.3 Vice-Chair Organization Represented Name of Representative Oscar Avellaneda Nortel Networks Ken Biholar Alcatel USA John Boal MEGAXESS, Inc. Dick Bobilin Acterna David Brady BellSouth Rick Canaday AT b) Block error ratio worse than 10nB, for XBnumber of consecutive observation periods o
12、f NBduration; c) More than Xtnumber of consecutive severely errored units of time. Receipt of a premature disconnect stimulus may result in a connection being disconnected and then reestablished. NOTE Only that subset of these criteria specified for a given service shall be considered. 3.2.9 Request
13、 acknowledgment: A signal from a network in response to an access request, indicating the networks readiness to accept address information. 4 Functional reference model The performance parameters for circuit-switched digital connections shall be specified in terms of the reference model in Figure 1.
14、 End-to-end performance shall be specified from NI-to-NI with performance allocated for NI-to-INI and INI-to-INI. Since connections may or may not span multiple networks, INIs are shown within dashed lines. For intra-network connections (no INIs), end-to-end parameters apply. ATIS-0100507.2002 4 NOT
15、ES 1. The exchange-carrier switch or the interexchange carrier network may not be in the circuit. However, at least one switch must be in the network. 2. NI Network Interface 3. INI Inter-Network Interface: INIs are only present when the service is provided across multiple networks. Where a point of
16、 termination (POT) exists, it will coincide with an INI. 4. There is the possibility that each segment may be comprised of transport from several providers. T1.TR.51-1996 provides details of an alternate model that may be operational where transport is obtained from more than one provider in a segme
17、nt. Figure 1 Functional reference model Inter-LATA network 5 Measurements 5.1 Types of measurements The parameters can be measured in the following ways: a) Out-of-service measurements: These measurements require the service to be made unavailable to the user. b) In-service measurements: These measu
18、rements are performed without disturbing user information transmissions. The measurements may not be available to the service providers. 5.2 Measurement purposes The following measurements and tests are made to verify long-term service performance: ATIS-0100507.2002 5 a) Acceptance tests: These test
19、s verify that the value of performance parameters are within prescribed limits after completion of a new service installation. The measurements for these tests are performed on an out-of-service basis. b) Trouble verification tests: These tests verify the need for maintenance activity, in response t
20、o a trouble report. The measurements for these tests are performed on either an in-service or out-of-service basis. c) Repair verification tests: These tests verify that the values of the performance parameters are within prescribed limits after completion of a repair activity. The measurements for
21、these tests are generally performed on an out-of-service basis. d) Service monitoring: These measurements verify that the values of the performance parameters are within prescribed limits. These in-service measurements are performed on a continuous or periodic basis. e) Characterization measurements
22、: These measurements collect data for determining the performance of a specific population (defined by bit rate, facility, type, and other characteristics). These measurements are performed on either an in-service or out-of-service basis. 6 Performance parameters Circuit-switched digital services ar
23、e characterized by three phases: the access phase, the information transfer phase, and the disengagement phase. a) Access phase: The access phase includes all those activities that are required for the establishment of a switched digital connection. The access phase begins with an access request and
24、 ends with connection establishment. b) Information transfer phase: The information transfer phase begins at connection establishment and ends with a disengagement request. c) Disengagement phase: The disengagement phase includes all those activities that are required for the termination of a switch
25、ed digital connection. The disengagement phase begins with a disengagement request and ends when the network is ready to respond to a new user access request. Parameters are measured at the network interface and are described in terms of defined interface events. These parameters, being network-spec
26、ific, only describe network performance. 6.1 Access phase performance parameters The access phase performance parameters are defined in this subsection. Delay calculations are made only on successful events and exclude any user-dependent delay. The event sequences for these parameters are shown in F
27、igure 2. ATIS-0100507.2002 6 NOTE When the complete address is included with the Access Request, T1 and T3 are coincident. PARAMETER MEASUREMENTS The Request Acknowledgment Delay is (T2-T1). The Request Acknowledgment Delay may only be measured when the Request Acknowledgment signal/message is prese
28、nt. The Alerting Indicator Delay is (T6-T3). The Alerting Indicator Delay may only be measured when the Alerting Indicator signal/message is present. In cases where the Alerting Indicator is provided external to the network under measure, the time (T5-T4) shall be subtracted from the measured value.
29、 The Connection Establishment Delay is (T8-T3) (T7-T4). Figure 2 Access phase event sequence Following are the access phase performance parameters: a) Request acknowledgment delay: This parameter is the time between the transmission of an access request and the receipt of the request acknowledgment.
30、 NOTE In all cases where the addressing information is sent with the access request, request acknowledgment delay is not measured separately. b) Alerting indicator delay: This parameter is the time between the transmission of the complete address and the receipt of the alerting indicator. Since an a
31、lerting indicator is not always provided, this parameter is not always measurable. T1 Access Request T2 Request Acknowledgement T3 Transmission of complete address (Note) T6 Alerting Indicator T8 Answer Indicator Connection Establishment orAlertingSignalT4T5AlertingIndicatorAnswerIndicatorT7Indicate
32、s event/signal/message that may occur Indicates event/signal/message that will occur Signal/MessageTransfer PointSignal/MessageTransfer PointNETWORKATIS-0100507.2002 7 c) Connection establishment delay: This parameter is the time between the transmission of the complete address and the connection es
33、tablishment, which may be indicated by a connection establishment signal. d) Incorrect access probability: This parameter is the ratio of the number of access attempts that result in incorrect access to total access attempts. Incorrect access occurs when a connection is established to a user other t
34、han the one intended. Incorrect addressing is excluded. e) Access denial probability: This parameter is the ratio of the total access phase attempts that are unsuccessful to the total number of access phase attempts. An access phase attempt is unsuccessful (access denial) when any of the following e
35、vents are observed: 1) The request acknowledgment delay exceeds S1 units of time; 2) The connection establishment delay exceeds S2 units of time; or 3) An indication of denied access is received. 6.2 Information transfer phase performance parameters 6.2.1 Parameter definitions a) Bit error ratio (BE
36、R): This parameter is the ratio of the number of bit errors to the total number or bits transmitted in a given time interval. Bit error ratio is used in this document to establish threshold values in defining performance parameters. b) Block error ratio (BLER): This parameter is the ratio of the blo
37、cks that contain at, least one bit in error to the total number of blocks transmitted in a given time interval. c) Errored unit of time measure: This parameter is the number or percent of errored units of time in a specified period. d) Severely errored unit of time measure: This parameter is the num
38、ber or percent of severely errored units of time in a specified period. e) Variation in mean one-way absolute delay: This parameter is the variation in one-way absolute delay between connections between the same end points, stated in terms of an interval of time. f) Premature disconnect probability:
39、 This parameter is the ratio of the number of premature disconnects (cut-offs) to the total number of successful accesses. g) Premature disconnect stimulus probability: The number of premature stimulus events per unit time over a specified period. ATIS-0100507.2002 8 6.2.2 Accuracy performance deter
40、mination The accuracy performance events and parameters are: Events Parameters Bit error Bit error ratio (BER) Block error Block error ratio (BLER) Errored Unit of Time (EUT) Errored unit of time measure Severely Errored Unit of Time (SEUT) Severely errored unit of time measure Severely Errored Peri
41、od (SEP) Severely errored period measure NOTE - Definitions for these events and parameters are found in T1.503-2002. 6.2.2.1 Single measurement period procedure This procedure is typically used in the design of trouble and repair verification tests. Performance determination for accuracy parameter
42、is based on the following relationships: a) Z number of intervals of length Q (on a single connection) are examined, where Z is an integer value and Q is an interval of time or a fixed number of bits corresponding to the event under consideration. b) For each interval Q examined, a determination is
43、made as to whether a threshold value W for the event has been exceeded, where W is a threshold of transmission bit or block errors over interval Q corresponding to the event under consideration. c) To determine the performance for the parameter under consideration, measure a total of Z intervals of
44、length Q and count the number of intervals where the number of transmission bit or block errors crosses the threshold W. The number of intervals counted is Y and the performance is the value Y/Z. Table 1 shows the relationship of the events to the intervals and thresholds. Table 1 Relationship of th
45、e accuracy event to the intervals and thresholds Event Interval (Q) Threshold (W) Errored unit of time Unit time Zero Errors Errored Block Block length (time or number of bits) Zero Errors Severely Errored Unit of Time Unit time Block error count over interval Q corresponding to 30% (see Note) Error
46、ed blocks (where a suitable block is not available, 10-3BER) or 1 SDP Severely Errored Period 3 unit times while in the available state 100% SEUT (a non-SEUT stops the sequence) NOTE - The errored block threshold for defining an SES (SEUT where the unit of time is 1 second) for SDH sections is diffe
47、rent from 30% and typically lower. ATIS-0100507.2002 9 6.2.2.2 Multiple measurement period procedures These procedures shall be used for service monitoring and characterization measurements (i.e., service performance acceptability). Measurements are made for each of a number of continuous fixed-leng
48、th time intervals. Performance is specified in terms of the ratio of intervals having parameter values within the limits established for a single interval to the total number of intervals examined. This procedure is based on the following relationships: a) V number of intervals of length U are exami
49、ned, where V is an integer value and U is an interval of Z contiguous intervals of length Q or a fixed number of bits Z x Q, (if Q represents a fixed number of bits) corresponding to the parameter under consideration. b) For each interval U, a determination is made as to whether a threshold value L for the parameter has been exceeded, where L is a threshold value for the measurement Y. c) To determine the performance for the parameter under consideration, measure Y over a total of V intervals (each comprised of Z intervals of length Q) and count the number of intervals
