1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T X.142TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2003) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS Public data networks Network aspects Quality of service metrics for characterizing Frame Relay/ATM service interworking performance ITU-T
2、 Recommendation X.142 ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS PUBLIC DATA NETWORKS Services and facilities X.1X.19 Interfaces X.20X.49 Transmission, signalling and switching X.50X.89 Network aspects X.90X.149 Maintenance X.150X.179 Administrative arrangements X.18
3、0X.199 OPEN SYSTEMS INTERCONNECTION Model and notation X.200X.209 Service definitions X.210X.219 Connection-mode protocol specifications X.220X.229 Connectionless-mode protocol specifications X.230X.239 PICS proformas X.240X.259 Protocol Identification X.260X.269 Security Protocols X.270X.279 Layer
4、Managed Objects X.280X.289 Conformance testing X.290X.299 INTERWORKING BETWEEN NETWORKS General X.300X.349 Satellite data transmission systems X.350X.369 IP-based networks X.370X.399 MESSAGE HANDLING SYSTEMS X.400X.499 DIRECTORY X.500X.599 OSI NETWORKING AND SYSTEM ASPECTS Networking X.600X.629 Effi
5、ciency X.630X.639 Quality of service X.640X.649 Naming, Addressing and Registration X.650X.679 Abstract Syntax Notation One (ASN.1) X.680X.699 OSI MANAGEMENT Systems Management framework and architecture X.700X.709 Management Communication Service and Protocol X.710X.719 Structure of Management Info
6、rmation X.720X.729 Management functions and ODMA functions X.730X.799 SECURITY X.800X.849 OSI APPLICATIONS Commitment, Concurrency and Recovery X.850X.859 Transaction processing X.860X.879 Remote operations X.880X.899 OPEN DISTRIBUTED PROCESSING X.900X.999 For further details, please refer to the li
7、st of ITU-T Recommendations. ITU-T Rec. X.142 (10/2003) i ITU-T Recommendation X.142 Quality of service metrics for characterizing Frame Relay/ATM service interworking performance Summary This Recommendation defines quality of service metrics for characterizing performance in the case of FR/ATM serv
8、ice interworking. The specified metrics can be used to quantify the performance of either the FR/ATM interworking function/unit or the quality of the end-to-end data connection. This Recommendation is complementary to ITU-T Rec. X.140 as it is a specific case of the general techniques described ther
9、ein for assessing performance. The specified metrics allow users and network operators to assess the performance from a user perspective. The metrics provide a simple manner by which either users or network operators could characterize the end-to-end performance. The defined metrics are not intended
10、 to be a replacement for the frame layer or ATM layer primary performance parameters but can be used to provide a user-oriented perspective of end-to-end performance. Source ITU-T Recommendation X.142 was approved by ITU-T Study Group 17 (2001-2004) under the ITU-T Recommendation A.8 procedure on 29
11、 October 2003. ii ITU-T Rec. X.142 (10/2003) 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 t
12、echnical, operating 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 whi
13、ch, in turn, produce 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
14、 IEC. NOTE In 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
15、 ensure e.g. interoperability 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 d
16、oes not suggest 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 concern
17、ing the evidence, 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 pate
18、nts, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. ITU 2004 All rights reserved. No part of this publication may be reproduced, by any
19、 means whatsoever, without the prior written permission of ITU. ITU-T Rec. X.142 (10/2003) iii CONTENTS Page 1 Scope 1 2 References. 1 3 Definitions 2 4 Abbreviations 2 5 Conventions 2 6 General reference model for FR/ATM service interworking . 3 7 Metrics for characterizing FR/ATM service interwork
20、ing performance 4 7.1 Data block delivered ratio/loss ratio. 4 7.2 Data block transfer delay 4 7.3 Data block delay jitter 5 8 Formal relationships between frame level and ATM level performance and traffic parameters. 5 9 Performance objectives. 5 Appendix I Estimation of loss and transit delay in t
21、he case of FR/ATM service interworking 6 I.1 Introduction 6 I.2 Estimation of end-to-end transit delay . 6 I.3 Estimation of data block loss ratio . 6 ITU-T Rec. X.142 (10/2003) 1 ITU-T Recommendation X.142 Quality of service metrics for characterizing Frame Relay/ATM service interworking performanc
22、e 1 Scope The purpose of this Recommendation is to define metrics for characterizing frame relay/ATM service interworking performance. This Recommendation is complementary to ITU-T Rec. X.140 as it is a specific case of the general techniques described in ITU-T Rec. X.140 for assessing performance.
23、Due to the intrinsic differences in the FR and ATM protocols, it is difficult, particularly from a user perspective, to directly map the performance parameters of one technology to the other in order to quantify the end-to-end performance in the case of FR/ATM service interworking. Since FR frames c
24、an be of varying length, the loss of one frame may translate into the loss of more than one cell. Also the transit delay of frames across a network will generally be longer than for ATM cells due to increased clocking and switching delays associated with larger frame sizes. The purpose of defining m
25、etrics is to ensure that there is a standard way of characterizing performance in the case where the end-to-end connection cannot be characterized by the usual frame or cell layer performance parameters and objectives. The specified metrics allow users and network operators to readily assess the per
26、formance from a user perspective. The metrics provide a simple manner by which either users or network operators may quantify (measure) the performance of either the FR/ATM interworking function/unit or the quality of the end-to-end data connection. The specified metrics and objectives apply in the
27、case where FR/ATM service interworking is provided. Although FR/ATM service interworking is a network option, there is no reason to prevent the service being provided on an end-to-end basis which may involve an international frame relay or ATM connection and, accordingly, this Recommendation also ha
28、s applicability on international connections. This Recommendation applies to those networks supporting the frame relay ATM/service interworking as defined in ITU-T Rec. I.555. It should be carefully noted that the defined metrics are not intended to be a replacement for the frame layer or ATM layer
29、primary performance parameters but have been defined to provide a user-oriented perspective of end-to-end performance. 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
30、time of publication, the editions indicated were valid. 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.
31、 A list of the currently valid ITU-T Recommendations 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 Recommendation I.356 (2000), B-ISDN ATM layer cell transfer performance. ITU-T Recomm
32、endation I.555 (1997), Frame Relaying Bearer Service interworking. ITU-T Recommendation X.36 (2003), Interface between Data Terminal Equipment (DTE) and Data Circuit-terminating Equipment (DCE) for public data networks providing frame relay data transmission service by dedicated circuit. 2 ITU-T Rec
33、. X.142 (10/2003) ITU-T Recommendation X.76 (2003), Network-to-network interface between public networks providing PVC and/or SVC frame relay data transmission service. ITU-T Recommendation X.111 (2003), Principles for the routing of international frame relay traffic. ITU-T Recommendation X.140 (199
34、2), General quality of service parameters for communication via public data networks. ITU-T Recommendation X.144 (2003), User information transfer performance parameters for public frame relay data networks. ITU-T Recommendation X.145 (2003), Connection establishment and disengagement performance pa
35、rameters for public Frame Relay data networks providing SVC services. ITU-T Recommendation X.146 (2000), Performance objectives and quality of service classes applicable to frame relay. ITU-T Recommendation X.148 (2003), Procedures for the measurement of the performance of public data networks provi
36、ding the international frame relay service. 3 Definitions The terms and definitions used in this Recommendation are consistent with those used in ITU-T Recs I.356, I.555, X.36, X.76, X.111, X.140, X.144, X.145, X.146 and X.148. 4 Abbreviations This Recommendation uses the following abbreviations: AT
37、M Asynchronous Transfer Mode CLR Cell Loss Ratio DBDJ Data Block Delay Jitter DBDR Data Block Delivered Ratio DBLR Data Block Loss Ratio DBTD Data Block Transfer Delay FCS Frame Check Sequence FLR Frame Loss Ratio FR Frame Relay FTD Frame Transfer Delay IWF InterWorking Function MP Measurement Point
38、 PVC Permanent Virtual Circuit SVC Switched Virtual Circuit 5 Conventions No specific conventions apply. ITU-T Rec. X.142 (10/2003) 3 6 General reference model for FR/ATM service interworking A general reference model in the case where a frame relay service user interworks with an ATM service user i
39、s shown in Figure 1. The ATM service user performs no frame relay service specific functions, and the frame relay service user performs no ATM service specific functions. The ATM terminal has no knowledge that the distant terminal is connected to a frame relay network and likewise, the frame relay t
40、erminal has no knowledge that the distant terminal is connected to an ATM network. This is known as service interworking. All interworking is performed by the FR/ATM interworking function. The functionality provided by the FR/ATM interworking function can be located in either the frame relay network
41、, or the ATM network, or may be a separate entity. ITU-T Rec. X.111 provides guidance and principles for the routing of traffic between frame relay and ATM networks. In the case where FR/ATM service interworking is provided on an international connection, the network operators will route traffic to
42、the FR/ATM IWF in accordance with network capabilities and bilateral arrangements. X.142_F1MP-FR MP-ATMFrame relay network(Note 1)ATM network(Note 2)FR/ATMIWFFrame relayterminalequipmentATMterminalequipmentNOTE 1 The FR connection between the originating FR terminal equipment and the FR/ATM IWF may
43、involve one or more transit networks.NOTE 2 The ATM connection between the FR/ATM IWF and the destination ATM terminalequipment may involve one or more transit networks.NOTE 3 The IWF may be functionally located in either the frame relay network or the ATM network or may be a separate entity as show
44、n.Figure 1/X.142 Frame relay/ATM service interworking X.142_F2Measurementboundary B1FR/ATMIWFData blockencapsulated in FR frames Data blockencapsulatedin ATM cellsMP-FRframe relay interfaceMP-ATMATMinterfaceMeasurementboundary B2Figure 2/X.142 General location of measurement points Whilst frame rela
45、y (or ATM) layer performance can be measured/monitored at any network boundary where a frame relay (or ATM) layer reference event can be monitored, the metrics defined in this Recommendation strictly apply in the case where one measurement point has access to the frame layer reference events and the
46、 other measurement point has access to ATM layer reference events. That is, the measurement is assessed across two boundaries B1and B2, where B1is a measurement point on the frame relay side of the interworking function and B2is a measurement point on the ATM side of the interworking function (or vi
47、ce versa) as shown in Figure 2. 4 ITU-T Rec. X.142 (10/2003) 7 Metrics for characterizing FR/ATM service interworking performance This clause defines a number of metrics which can be used to characterize the transmission performance of the end-to-end connection in the case of FR/ATM service interwor
48、king. Three parameters are defined: Data Block Delivered Ratio, Data Block Transfer Delay and Data Block Delay Jitter. The measured/achieved value for each of these parameters will depend on the frame and ATM cell loss ratios, frame transfer delay and frame delay jitter, cell transfer delay and cell
49、 delay variation performance. The FR/ATM service interworking performance metrics are independent of the frame relay or ATM service classes or traffic contracts which may be used to establish the end-to-end connection. The metrics are applicable to both SVCs and PVCs. 7.1 Data block delivered ratio/loss ratio The effects of frame or cell loss on the end-to-end performance is characterized by the metric of Data Block Delivered Ratio (DBDR). This parameter characterizes the user data transfer performance of the end-to-end con
