1、 AMERICAN NATIONAL STANDARD FOR TELECOMMUNICATIONS ATIS-0300231.2003(R2007) LAYER 1 IN-SERVICE TRANSMISSION PERFORMANCE MONITORING ATIS is the leading technical planning and standards development organization committed to the rapid development of global, market-driven standards for the information,
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5、onal 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 has been reached by directly a
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9、uld 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 CAUTION NOTICE: This American National Standard may be revised or withdrawn at any time.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 be taken periodically to reaf
10、firm, 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 Revision T1.231-1997) American National Standard for Telecommunications Layer 1 In
11、-Service Transmission Performance Monitoring Secretariat Alliance for Telecommunications Industry Solutions Approved October 22, 2003 American National Standards Institute, Inc. Abstract This standard provides performance monitoring (PM) functions and requirements applicable to Layer 1 transmission
12、signals for the covered levels of the North American transmission hierarchy. This standard provides functional requirements to support maintenance and is not meant to be an equipment specification. This standard, and its subparts, supersedes and replaces T1.231-1997 in its entirety. ATIS-0300231.200
13、3 ii Foreword The information contained in this Foreword is not part of this American National Standard (ANS) and has not been processed in accordance with ANSIs requirements for an ANS. As such, this Foreword may contain material that has not been subjected to public review or a consensus process.
14、In addition, it does not contain requirements necessary for conformance to the standard. This American National Standard is one of a series of maintenance operations standards developed by Technical Subcommittee T1M1 of Committee T1 - Telecommunications. Committee T1 standards serve the public throu
15、gh improved understanding between carriers, end-users, and manufacturers. This standard specifies a basic set of monitoring requirements, and provides criteria that is common to a set of standards, the T1.231 series, which define applications for a specific level in the hierarchy. The documents, whi
16、ch are included in the T1.231 series (at the time that this document is approved), are listed below: T1.231-2003, Layer 1 In-Service Transmission Performance Monitoring. T1.231.01-2003, DSL Layer 1 In-Service Digital Transmission Performance Monitoring. T1.231.02-2003, DS1 Layer 1 In-Service Digital
17、 Transmission Performance Monitoring. T1.231.03-2003, DS3 Layer 1 In-Service Digital Transmission Performance Monitoring. T1.231.04-2003, SONET Layer 1 In-Service Digital Transmission Performance Monitoring. T1.231.05-200x, OTN Layer 1 In-Service Transmission Performance Monitoring. (This standard i
18、s not yet approved.) This standard will be useful to anyone engaged in the design, provisioning, or operation, of telecommunications equipment or services, utilizing transmission technologies. The standard establishes uniform and consistent performance monitoring (PM) functions and requirements appl
19、icable to Layer 1 transmission signals for the covered levels of the North American transmission hierarchy. This standard is intended to be a living document, subject to revision and updating as warranted by advances in transmission technologies Compliance with the standard should provide uniform an
20、d consistent measurement parameters and techniques for circuits, facilities, and networks. In some cases, location-oriented options are needed to ensure compatibility: this need for options is imposed by significant differences between network providers as well as between network elements Requiremen
21、ts are designated by the word shall, while recommendations utilize the word should. Requirements specify the minimum acceptable functionality for effective PM in a network element; recommendations identify functionality that may enhance PM capabilities for some users. There are four annexes in this
22、document. All are informative, and are not considered part of the standard. Suggestions for the improvement of this standard will be welcome They should be sent to the Alliance for Telecommunications Industry Solutions, 1200 G Street, NW, Suite 500, Washington, DC, 20005. This standard was processed
23、 and approved for submittal to ANSI by Accredited Standards Committee on Telecommunications, T1. Committee approval of the standard does not necessarily imply that all members voted for its approval. At the time it approved this standard, the T1 Committee had the following members: E.R. Hapeman, T1
24、Chair W.R. Zeuch, T1 Vice-Chair J.A. Crandall, T1 Director S.M. Carioti, T1 Disciplines S.D. Barclay, T1 Secretary C.A. Underkoffler, T1 Chief Editor T. Malpass, T1M1 Technical Editor EXCHANGE CARRIERS Organization Represented Name of Representative AT 2) testing; and 3) restoration. Each is describ
25、ed briefly below; additionally, surveillance is discussed in more detail in 4.2, while testing and restoration are not addressed further in this standard. In addition to the philosophies identified here, G.7710 also includes additional performance management applications. 4.1.1 Surveillance Surveill
26、ance refers to the real-time, non-intrusive monitoring of the various components of a network, so that performance degradations can be identified before customer service is adversely affected. 4.1.2 Testing In the classic sense, testing is the process of verifying failures or performance degradation
27、s by subjecting particular network entities to predetermined inputs (such as quasi-random test signals) and measuring the resulting response. The test signals are often applied to the entire digital bit stream, thus requiring that testing be done on an intrusive (out-of-service) basis. An example is
28、 the loopback test performed on a transmission line to sectionalize a failure. Modern digital signal formats (e.g., DS1 ESF, DS3 C-bit parity, and SONET) provide capabilities that permit the development of non-intrusive testing through the use of the signal overhead. Predetermined signals can be app
29、lied to the overhead channel without affecting the customer payload. Maintenance functions such as trouble isolation can now be accomplished without interruption of service. This standard provides a forward-looking platform to develop the concept of trouble diagnosis on a non-intrusive basis via the
30、 use of digital signal overhead analysis. ATIS-0300231.2003 5 4.1.3 Restoration Restoration refers to the process of rerouting the service of a particular network entity that has suffered a failure or a severe performance degradation. Network restoration can range from simple protection switching of
31、 a transmission line to more complicated rerouting of traffic around a failed switch, cross-connect system, central office, etc. 4.2 Fundamental elements of network surveillance Surveillance has two distinct, but related, functional elements. These are alarm/status monitoring and performance monitor
32、ing (PM). 4.2.1 Alarm/status monitoring Alarm/status monitoring is a process that tracks failure events to contribute to an understanding of the overall transmission performance of an entity. The information conveyed via alarm/status monitoring consists of a set of binary data, known as indications
33、that are maintained by the Network Element (NE). The NE sets and clears indications according to well-defined criteria based on the occurrence and duration of specific events. Some events lead immediately to indications, while others must persist for a specified soaking time prior to the setting of
34、an indication. Discussions related to alarm/status monitoring in this standard are limited to monitoring of transmission failures. 4.2.2 Performance Monitoring (PM) Performance monitoring is the process of continuous collection, analysis, and reporting of performance data associated with a transmiss
35、ion entity. In the context of this standard, the term performance monitoring (PM) refers to the set of functions and capabilities necessary for an NE to gather, store, threshold (see below), and report performance data associated with its monitored transmission entities. These performance-related da
36、ta elements are termed performance parameters. Figure 1 shows a graphical representation of this process. The fundamental building blocks of the various performance parameters are a set of primitives detectable from the monitored signal. For instance, a common performance primitive is the block codi
37、ng error detected from a monitored transmission signal (e.g., a CRC-6 code violation in a DS1 ESF signal). This primitive is the basis for generation and storage of performance parameters such as Errored Seconds (ES) and Severely Errored Seconds (SES). For some signals, performance primitives in the
38、 incoming direction are reported to the far-end via special messages embedded within the signal format. Examples include: the Performance Report Message (PRM) in DS1 ESF, Far-End Block Error (FEBE) indicators in DS3 C-bit applications, and Remote Error Indicators (REI) in SONET. With such a capabili
39、ty built into a transmission signal, part of the monitoring functions (derivation, storage, thresholding, and reporting of parameters) for transmission performance observed at the far-end can be provided at the near-end. In contrast with alarm/status indications, performance parameters are quantitat
40、ive - not binary - in nature. Furthermore, alarm and status indications are generally reported under failure events, while performance parameters are normally gathered under in-service, non-failure conditions. Thus, alarm/status monitoring and PM complement one another as basic tools of surveillance
41、-based maintenance. Performance parameters are accumulated over predetermined accumulation periods (normally 15 minutes and one day), and are maintained in designated storage registers; see 6.1.2.1 for register definitions. At the end of every accumulation period (i.e., at the end of each 15 minutes
42、 for 15-minute and at the end of each day for day performance registers), the current value of the performance parameter register is saved in its corresponding “previous period“ register, and the current register is initialized. Depending on the type of the performance parameter, additional register
43、s may be provided to maintain a recent history of the parameter (e.g., 31 additional 15-minute registers for errored seconds, etc.). Performance history data is useful for verifying customer trouble reports and in responding to alerts, so as to quickly assess the recent performance of transport syst
44、ems and to sectionalize the trouble or degradation. This history can also be used in performance assessment against long-term performance objectives. It is expected that degradations in transmission performance are automatically communicated based on their relationship to a particular threshold valu
45、e. Most performance parameters have a corresponding settable threshold. If, at any time during the accumulation period, the current value of a performance parameter reaches or exceeds its corresponding threshold value, a Threshold Crossing Alert (TCA) or Out of Range Alert (ORA) message is generated
46、 and sent. Thus, alert messages can convey the early indication that the performance of a given transmission entity may have degraded and that a maintenance action may be warranted. ATIS-0300231.2003 6 Defect AnomalyFailureGenerateparametersThresholding CurrentPreviousRecentAlarmindicationsAlertmess
47、agesCurrentdataHistoricdataStoragePrimitivesFigure 1 - Performance Monitoring Process 4.3 Performance Estimation PM must support the functions of service quality assessment. Defined performance parameters and data collection and storage techniques must provide the capability to construct a view of p
48、erformance. This is accomplished by ensuring that approximations of bit error statistics can be derived from the defined parameters. For example, counts of cyclic redundancy check (CRC) code violations enable the direct calculation of block error ratios, thereby allowing an estimation of minimum bit
49、 error ratios (BERs). The additional information of ES and SES counts permits an estimation of the degree of burstiness of the errors, which may help identify the source of the errors. Similarly, the character of the error statistics may indicate the effect of the degradation on specific services. Random errors at a relatively low BER, for example, may have a significant effect on a packet service, but little effect on a video service; conversely, bursty errors even at a high BER may have little effect on a packet service, but significant effect on ATIS-0300231.2003 7 a vi
