1、 International Telecommunication Union ITU-T O.220TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (03/2007) SERIES O: SPECIFICATIONS OF MEASURING EQUIPMENT Equipment to perform measurements on leased-circuit services Framework for end-to-end QoS measurement and supervision for leased-circuit service
2、s ITU-T Recommendation O.220 ITU-T O-SERIES RECOMMENDATIONS SPECIFICATIONS OF MEASURING EQUIPMENT General O.1O.9 Maintenance access O.10O.19 Automatic and semi-automatic measuring systems O.20O.39 Equipment for the measurement of analogue parameters O.40O.129 Equipment for the measurement of digital
3、 and analogue/digital parameters O.130O.199 Equipment for the measurement of optical channel parameters O.200O.209 Equipment to perform measurements on IP networks O.210O.219 Equipment to perform measurements on leased-circuit services O.220O.229 For further details, please refer to the list of ITU-
4、T Recommendations. ITU-T Rec. O.220 (03/2007) i ITU-T Recommendation O.220 Framework for end-to-end QoS measurement and supervision for leased-circuit services Summary ITU-T Recommendation O.220 describes the overview of the end-to-end QoS measurement and supervision mechanisms, which can be used to
5、 carry out SLA guarantee. Several options for the end-to-end QoS measurement and supervision mechanisms are provided. Source ITU-T Recommendation O.220 was approved on 16 March 2007 by ITU-T Study Group 4 (2005-2008) under the ITU-T Recommendation A.8 procedure. Keywords End-to-end, probe, QoS, SLA.
6、 ii ITU-T Rec. O.220 (03/2007) FOREWORD The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, oper
7、ating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, p
8、roduce Recommendations on these topics. The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with ISO and IEC. NOTE In
9、this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. i
10、nteroperability or applicability) and compliance with the Recommendation is achieved when all of these mandatory provisions are met. The words “shall“ or some other obligatory language such as “must“ and the negative equivalents are used to express requirements. The use of such words does not sugges
11、t that compliance with the Recommendation is required of any party. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the eviden
12、ce, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, which may
13、 be required to implement this Recommendation. However, implementers are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database at http:/www.itu.int/ITU-T/ipr/. ITU 2007 All rights reserved. No part of this publication may be
14、reproduced, by any means whatsoever, without the prior written permission of ITU. ITU-T Rec. O.220 (03/2007) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 1 3.1 Terms defined elsewhere 1 3.2 Terms defined in this Recommendation. 2 4 Abbreviations and acronyms 2 5 Conventions 2 6 Overview
15、 2 6.1 Introduction to the service environment of LCS 2 6.2 Purpose of QoS monitoring and supervision for LCS 3 6.3 Problems with QoS monitoring and supervision in the traditional way. 3 7 Basic requirements for the functions of end-to-end QoS monitoring. 3 8 Overview of end-to-end QoS monitoring an
16、d supervision mechanisms 4 9 Introduction to QoS probes. 4 9.1 Functional description 4 9.2 The purpose of using QoS measurement instruments for end-to-end QoS monitoring 4 9.3 Connection methods between a QoS probe and the monitored network 5 10 Deployment of measurement instruments 5 10.1 In the m
17、iddle of the network 5 10.2 At the edge of the SPs network 7 11 Connection methods between QoS measurement instruments and management systems 7 11.1 Measurement instruments connected to TMN OS with individual lines . 7 11.2 Measurement instruments connected to TMN OS with a converged management inte
18、rface. 8 12 Considerations for selecting the end-to-end QoS monitoring mechanisms using probes 8 12.1 Reliability consideration. 8 12.2 Deployment consideration 9 12.3 Interconnection consideration 9 13 Examples of end-to-end QoS monitoring options 9 13.1 Example 1: Parallel connection with individu
19、al management interfaces. 9 13.2 Example 2: Serial connection with a converged management interface 10 Appendix I Examples of alarms and QoS parameters to be monitored 11 Bibliography. 12 ITU-T Rec. O.220 (03/2007) 1 ITU-T Recommendation O.220 Framework for end-to-end QoS measurement and supervision
20、 for leased-circuit services 1 Scope When a service provider (SP) plans to provide a service to a key customer with QoS guarantees using an SLA, some measures should be taken to monitor the end-to-end QoS provided to the customer, so that it is possible for the SP to know whether the SLA has been vi
21、olated or not during the whole lifetime of the service. The purpose of this Recommendation is to introduce an architectural framework, supporting end-to-end QoS monitoring functionality. This functionality can be achieved in multiple ways. NE with built-in capabilities is one choice for those networ
22、k technologies that support it, and stand-alone instrumentation is another choice, which can be applied to the network technologies that do not provide this functionality within their own technologies. It is the intention of this Recommendation to provide solutions which do not influence the network
23、 elements. This Recommendation provides an overview of end-to-end QoS measurement and supervision architectures. Within its scope, it provides an overview of: problems currently experienced when carrying out end-to-end QoS measurement and supervision for a network service; considerations for the loc
24、alization of the responsibility when a SLA is violated, either due to network side problems or to customer side problems; general recommendations for the mechanisms of the end-to-end QoS measurement and supervision using measurement instruments (such as probes); and other considerations for selectin
25、g end-to-end QoS monitoring and supervision mechanisms using probes. 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were v
26、alid. All Recommendations and other references are subject to revision; 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 Recommendatio
27、ns is regularly published. The reference to a document within this Recommendation does not give it, as a stand-alone document, the status of a Recommendation. ITU-T E.860 ITU-T Recommendation E.860 (2002), Framework of a service level agreement. ITU-T M.3208.1 ITU-T Recommendation M.3208.1 (1997), T
28、MN management services for dedicated and reconfigurable circuits network: Leased circuit services. 3 Definitions 3.1 Terms defined elsewhere This Recommendation uses the following terms defined elsewhere: 3.1.1 service level agreement (SLA): ITU-T E.860. 3.1.2 leased circuit service (LCS): ITU-T M.3
29、208.1. 2 ITU-T Rec. O.220 (03/2007) 3.2 Terms defined in this Recommendation This Recommendation defines the following term: 3.2.1 QoS probe: A measurement and test instrument that can be used to monitor alarms and collect QoS parameters in a network in real time. 4 Abbreviations and acronyms This R
30、ecommendation uses the following abbreviations and acronyms: AIS Alarm Indication Signal ATM Asynchronous Transfer Mode DCN Data Communications Network DDN Digital Data Network EMS Element Management System ES Errored Second IP Internet Protocol LCS Leased Circuit Service LOF Loss Of Frame LOS Loss
31、Of Signal NE Network Element OS Operating System PCM Pulse Code Modulation QoS Quality of Service SC Service Customer SES Severely Errored Second SLA Service Level Agreement SP Service Provider TMF TeleManagement Forum US Unavailable Seconds 5 Conventions None. 6 Overview 6.1 Introduction to the ser
32、vice environment of LCS The current services provided on leased circuit to key customers mainly include (but are not limited to) the following: 2M digital circuits (for IP or PCM); DDN; ATM; ITU-T Rec. O.220 (03/2007) 3 X.25; Frame relay. 6.2 Purpose of QoS monitoring and supervision for LCS In gene
33、ral, the purpose of the QoS monitoring and supervision is to: monitor the performance parameters, detect faults in real time and generate QoS reports, in order to know the running status and QoS level of the circuits provided to customers; support QoS reporting to key customers with an SLA; help loc
34、ate faults occurring in the network quickly and precisely; fast locate the responsibility for a specific QoS degradation. Some service problems are not occurring at the network side, but at the user side, which is outside the scope of the end-to-end LCS, and should not be counted as LCS QoS degradat
35、ion; and try to provide better technical support to key customers. 6.3 Problems with QoS monitoring and supervision in the traditional way Traditionally, a network management system (NMS) collects performance data from element management systems (EMSs) and network elements (NEs) directly, and then a
36、nalyses the QoS of the transport part of the leased circuits according to the collected data. Limitations of the system implementations could create obstacles which are difficult to overcome: Hardware and software implementation choices in traditional EMSs or NEs put limits on their performance when
37、 executing all the performance monitoring tasks, possibly resulting in performance degradation of managed systems or even telecommunication services of the NEs. No end-to-end QoS parameters are provided for a specific customer, as there is no specific instrument positioned for a specific customer. W
38、ith the traditional way of QoS data measurement, precise fault location may be difficult. 7 Basic requirements for the functions of end-to-end QoS monitoring In order to support end-to-end QoS monitoring for an LCS, the following functional requirements should be supported by a QoS measurement mecha
39、nism: real-time collection of QoS data for an end-to-end service; the end-to-end QoS monitoring shall provide means to collect QoS data for a specific service customer (SC); detection for QoS-related problems at both customer side and network side; there shall be mechanisms for a QoS measurement ins
40、trument to transfer its monitored result to the network management systems (directly or indirectly); the end-to-end QoS monitoring mechanisms shall be controlled by management systems (such as an NMS or an EMS); and the interfaces for exchanging management information between QoS measurement instrum
41、ents, or between QoS measurement instruments and management systems, shall be provided. A list of the alarms and QoS parameters that may be monitored for end-to-end QoS monitoring can be found in Appendix I. 4 ITU-T Rec. O.220 (03/2007) 8 Overview of end-to-end QoS monitoring and supervision mechani
42、sms In order to solve the problems encountered in the traditional way of QoS measurement as mentioned in clause 6.3, and to meet the requirements as listed in clause 7, some proposed architectures and considerations for the end-to-end QoS monitoring and supervision are provided in the following clau
43、ses, and will be described in three aspects, namely: introduction to QoS probes; deployment of the measurement instruments; and connection methods between QoS measurement instruments and management systems. The combination of the three aspects will result in several end-to-end QoS monitoring and sup
44、ervision mechanisms. 9 Introduction to QoS probes 9.1 Functional description QoS probes are stand-alone measurement instruments used to monitor the QoS information of a specified circuit(s). A QoS probe is able to provide the following functions: collect the specified QoS parameters from the monitor
45、ed circuit(s); transfer the collected QoS data to the network management systems; help to locate the fault position in the monitored circuit(s). 9.2 The purpose of using QoS measurement instruments for end-to-end QoS monitoring The purpose of introducing measurement instruments, such as QoS probes,
46、is to solve the issues in end-to-end QoS monitoring which the traditional performance management cannot easily solve. The purposes and the benefits are summarized in the following list: 1) From the perspective of hardware system performance, they can improve the overall performance of end-to-end QoS
47、 monitoring, because it is more efficient to install one or more QoS probes for the desired measurement points than improving the overall processing capability of the EMSs, and there is no need to change the current serving NEs that do not provide powerful QoS monitoring capabilities. 2) The traditi
48、onal QoS parameters are mainly monitored from the network perspective, and the focus is not on individual services from the end-to-end QoS perspective. It is difficult to provide the QoS parameter data for a specific LCS SC. When QoS probes are applied for the end-to-end QoS monitoring, it will be m
49、uch easier to collect the end-to-end service parameters that are specific for a customer, as QoS probes can be designed to provide the capability for monitoring dedicated QoS parameters for one or more LCS SCs at the same time. 3) As the traditional QoS monitoring mechanisms are mainly focusing on the detection of network problems, when there is a QoS complaint from a SC, it is usually very hard to make a decision on whether the QoS degradation or service unavailability is caused by the SPs network or by the SC o
