1、 INTERNATIONAL TELECOMMUNICATION UNION X.146TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2000) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS Public data networks Network aspects Performance objectives and quality of service classes applicable to frame relay ITU-T Recommendation X.146
2、 (Formerly CCITT Recommendation) 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 arrang
3、ements X.180X.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
4、.279 Layer 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.60
5、0X.629 Efficiency 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 Mana
6、gement Information 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 refe
7、r to the list of ITU-T Recommendations. ITU-T X.146 (10/2000) i ITU-T Recommendation X.146 Performance objectives and quality of service classes applicable to frame relay Summary This Recommendation defines the reference model, national/international apportion model, frame relay service classes and
8、their associated delay and loss objectives, applicable to networks providing frame relay PVC or SVC service and supporting frame relay service classes. Source ITU-T Recommendation X.146 was revised by ITU-T Study Group 7 (1997-2000) and approved by the World Telecommunication Standardization Assembl
9、y (Montreal, September 27 October 6 2000). ii ITU-T X.146 (10/2000) 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 res
10、ponsible for studying technical, 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
11、 ITU-T study groups which, 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 collabora
12、tive basis with ISO and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. INTELLECTUAL PROPERTY RIGHTS ITU draws attention to the possibility that the practice or implementa
13、tion of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process. As
14、of the date of approval of this Recommendation, ITU had not received notice of intellectual property, protected by patents, 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
15、to consult the TSB patent database. Ge3 ITU 2001 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU. ITU-T X.146 (10/2000) iii CONTENTS Page
16、 1 Scope. 1 2 References. 3 3 Abbreviations 3 4 Reference model . 4 5 Network performance objectives and frame relay quality of service classes 5 5.1 Nature of the network performance objectives. 6 5.2 Statistical estimation of network performance . 6 5.3 Unspecified performance 7 5.4 Standardized F
17、rame Size for FTD performance measurement. 7 5.5 Frame relay service classes . 7 6 Service class allocation methods 8 6.1 Route length calculation . 8 6.2 Access circuit section allocations . 8 6.3 Frame delay allocations to national and international portions 9 6.4 Frame loss allocations to nationa
18、l and international portions. 10 Appendix I Illustration of the weighted distribution concept for X.146 with possible application to frame relay SVC connections and measurement methods to estimate the 95th percentile of FTD 10 I.1 Weighted distributions and SVC performance estimation 10 I.2 Methods
19、to estimate the 95th percentile of FTD 12 Appendix II Effect of transmission delay and frame size on FTD 13 ITU-T X.146 (10/2000) 1 ITU-T Recommendation X.146 Performance objectives and quality of service classes applicable to frame relay 1 Scope The purpose of this Recommendation is to define frame
20、 relay service classes with their associated delay and loss parameters, together with allocations to national and international portions applicable to international frame relay services in accordance with ITU-T Recommendations identified herein. This Recommendation defines frame relay service classe
21、s that may be used to describe the information transfer phase of data networks when providing international frame relay service (either permanent virtual connection service or switched virtual connection service). Two frame relay performance parameters of ITU-T X.144 frame transfer delay and committ
22、ed frame loss ratio are used to characterize the various frame relay service classes. This Recommendation applies only to those networks supporting the service class options of X.36 and X.76. Signalling and service class interworking issues are covered in ITU-T X.36 and X.76. The 3 3 performance mat
23、rix defined in ITU-T X.134 (see Figure 1) is used as a guide to identify the applicability of this Recommendation. As mentioned above, this Recommendation applies to the information transfer phase of a frame relay virtual connection. The parameters defined in this Recommendation may be allocated to
24、specify the performance of end-to-end frame relay connections or connection portions as specified in ITU-T X.144. The frame relay service classes defined in this Recommendation describe specific design objectives for the information transfer phase of the national and international portions of an int
25、ernational virtual connection. In the context of this Recommendation, the term “service class“ is equivalent to the terms “quality of service class“ or “QoS class“ as used in ITU-T I.356. NOTE 1 The service classes defined in this Recommendation may be augmented or modified based upon further study
26、of the requirements of frame relay to be supported on networks. NOTE 2 The defined service classes are intended to characterize frame relay connections in the available state. This Recommendation is organized as follows: clause 2 presents references; clause 3 presents abbreviations; clause 4 reviews
27、 the performance model of ITU-T X.144 and its national and international portions that provide the basis for the allocations given in clause 5; clause 5 defines frame relay service classes applicable to the user information transfer phase of a frame relay virtual connection, based primarily on the t
28、wo performance parameters of frame transfer delay (FTD) and committed frame loss ratio (FLRc); clause 6 defines allocations of the service classes defined in clause 5 to the national and international portions described in clause 4. 2 ITU-T X.146 (10/2000) T0732420-99Physicalinterface(Frame relaynet
29、work)DSE DSENetwork sectionDTEorDSECircuit sectionDTEorDSEFrame transfer reference eventsFunctionAccess(call set-up)UserinformationtransferDisengagement(call tear-down)Speed DependabilityAccuracyX.144 and X.146CriterionServiceavailable(no outage)AvailabilityServiceavailable(outage)PhysicalinterfaceP
30、hysicalinterfacePhysicalinterfaceX.144X.144X.145X.145X.145Figure 1/X.146 Scope of this Recommendation ITU-T X.146 (10/2000) 3 2 References The following ITU-T Recommendations and other references contain provisions which, through reference in this text, constitute provisions of this Recommendation.
31、At the time of publication, the editions indicated were valid. All Recommendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigate the possibility of applying the most recent edition of the Recommendations and other references li
32、sted below. A list of currently valid ITU-T Recommendations is regularly published. ITU-T G.114 (2000), One-way transmission time. ITU-T X.36 (2000), Interface Between Data Terminal Equipment (DTE) and Data Circuit-Terminating Equipment (DCE) for public data networks providing frame relay data trans
33、mission service by dedicated circuit. ITU-T X.76 (2000), Network-to-network interface between public networks providing PVC and/or SVC frame relay data transmission service. ITU-T X.140 (1992), General quality of service parameters for communication via public data networks. ITU-T X.144 (2000), User
34、 information transfer performance parameters for data networks providing international frame relay PVC service. ITU-T X.145 (1996), Performance for data networks providing international frame relay SVC service. 3 Abbreviations This Recommendation uses the following abbreviations: AR Access line Rate
35、 for the access circuit section CPE Customer Premises Equipment DCE Data Circuit-terminating Equipment DkmAir route distance DSE Data Switching Equipment DTE Data Terminal Equipment FDJ Frame Delay Jitter FLRcCommitted frame loss ratio FTD Frame Transfer Delay FTDaAccess circuit section frame transf
36、er delay FTDIInternational portion frame transfer delay FTDNNational portion frame transfer delay FTDOEdge-to-edge frame transfer delay objective NNI Network-to-Network Interface PVC Permanent Virtual Connection QoS Quality of Service RaAccess circuit section route length 4 ITU-T X.146 (10/2000) RIR
37、oute length of the international portion RkmRoute length SVC Switched Virtual Connection UNI User-to-Network Interface 4 Reference model The performance model for this Recommendation is that of ITU-T X.144 (as presented in clause 4/X.144). For completeness, this performance model is illustrated by F
38、igure 2. The national and international portions of this frame relay performance model are those used in clause 6. T0733460-00AccessnetworksectionAccesscircuitsectionDTENational portion National portionInternational portionOne or more(optional)Inter-networkcircuitsectionTransitnetworksectionInter-ne
39、tworkcircuitsectionTransitnetworksectionInter-networkcircuitsectionAccessnetworksectionAccesscircuitsectionInter-networkcircuitsectionTransitnetworksectionDTENationalborderNationalborder(optional)Zero or more(optional)One or more(optional)International virtual connection (end-to-end)International vi
40、rtual connection (edge-to-edge)Portion boundarySection boundaryFigure 2/X.146 Reference model for the apportionment of national and international portions of a multiple-network international virtual connection Note that an end-to-end international virtual connection consists of two national portions
41、 and one international portion. In certain cases, the international portion could consist solely of an internetwork circuit section. In this Recommendation, the term edge-to-edge denotes the performance of the end-to-end connection excluding the two access circuit sections. This model applies to the
42、 information transfer phase of a frame relay connection, and is applicable to either a switched virtual connection (SVC) or a permanent virtual connection (PVC). The Data Terminal Equipment (DTE) is not part of the end-to-end international virtual connection; hence, its contribution to the user expe
43、rience is not considered in this Recommendation. Private frame relay networks are considered as DTE, and thus neither is their performance contribution considered in this Recommendation. The subject of quantifying the degree to which a private frame relay network contributes to the overall user expe
44、rience is a subject for further study. ITU-T X.146 (10/2000) 5 5 Network performance objectives and frame relay quality of service classes This clause discusses the general nature of per-connection frame relay network performance objectives and the specific quality of service (QoS) classes of Table
45、1 through which they are supported. Issues of estimating these network objectives are also discussed, as is the weighting referred to in Table 1. With respect to the frame relay QoS classes in Table 1, the user has the option of requesting a different QoS class for each new SVC or PVC. While three o
46、f the four QoS classes in Table 1 have numeric objectives for both FLRcand FTD, there is one class (class 0) for which no objectives are specified. Class 0 is therefore sometimes referred to as the unspecified class. Table 1/X.146 Frame relay service classes Class Network support FLRcFTD (ms) FDJ (m
47、s) 0 Mandatory, default class No upper bound specified on FLRc. But FLRcwill have a practical upper bound and will not be arbitrarily bad. No upper bound specified on FTD. But delay will have a practical upper bound and will not be arbitrarily large. Not Applicable 1 Mandatory Value 1200 km, then Rk
48、m= 1.25 Dkm. This rule does not apply if there is a satellite in the portion. 6.2 Access circuit section allocations An access circuit section is part of a national portion. ITU-T X.146 (10/2000) 9 As noted above, the major contribution to FLRcperformance is complexity. The apportionment of the nati
49、onal portion FLRcallocation to the access circuit section is a national matter. Hence, this Recommendation makes no allocation to the access circuit section for FLRc. For FTD, the contribution of the access circuit section could be significant, depending on both its length and its nominal access line rate. The following formula quantifies the access circuit sections contribution to FTD. The following notation is used: AR stands for the access line rate of the access circuit section in bits per second; FTDai
