1、 INTERNATIONAL TELECOMMUNICATION UNION ITU-T X.147TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU (10/2003) SERIES X: DATA NETWORKS AND OPEN SYSTEM COMMUNICATIONS Public data networks Network aspects Frame Relay network availability ITU-T Recommendation X.147 ITU-T X-SERIES RECOMMENDATIONS DATA NETW
2、ORKS 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.180X.199 OPEN SYSTEMS INTERCONNECTION Model and notation X.200X.
3、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 Managed Objects X.280X.289 Conformance testing X.290X.299 INTE
4、RWORKING 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 Efficiency X.630X.639 Quality of service X.640X.649 Naming, Addres
5、sing 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 Information X.720X.729 Management functions and ODMA functions X.7
6、30X.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 list of ITU-T Recommendations. ITU-T Rec. X.147 (10/2003) i ITU-
7、T Recommendation X.147 Frame Relay network availability Summary This Recommendation defines network performance parameters, objectives and measurement methods for describing the availability of Frame Relay networks. The specified parameters and objectives apply to international Frame Relay connectio
8、n portions National Portions, International Transit Network Portions and International Interoperator Portions. The objectives, which are worst-case values, are intended to assist service providers with network planning by limiting the aggregate effect of network impairments, including congestion, eq
9、uipment failures and transmission errors. A set of network objectives is specified which define the overall network performance based on a statistical sample of Frame Relay connections. The objectives do not apply to or define the performance of an individual Frame Relay connection. A two-state avai
10、lability model is defined along with criteria for determining if the service during specific periods of time should be declared to be either available or unavailable. A number of procedures are defined in order to assess the availability performance of virtual connections. An expression for determin
11、ing a value for overall network availability is presented. Information for estimating availability from a minimal set of observations is also presented. Source ITU-T Recommendation X.147 was approved by ITU-T Study Group 17 (2001-2004) under the ITU-T Recommendation A.8 procedure on 29 October 2003.
12、 ii ITU-T Rec. X.147 (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 technical, oper
13、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
14、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
15、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
16、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
17、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
18、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
19、 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 means whatsoe
20、ver, without the prior written permission of ITU. ITU-T Rec. X.147 (10/2003) iii CONTENTS Page 1 Scope 1 2 References. 3 3 Definitions 4 4 Abbreviations 4 5 Conventions 5 6 General Frame Relay performance reference model 5 6.1 Frame Relay virtual connection portions and measurement points 5 7 Method
21、 for specifying availability 6 7.1 General definition of availability 6 7.2 Availability model 6 7.3 Definition of available/unavailable state 7 7.4 Methods for assessing availability 8 7.5 Availability parameters 8 8 Availability performance objectives. 9 8.1 Availability Ratio . 10 8.2 Mean Time B
22、etween Outages 10 Annex A Determining availability states by use of performance parameter thresholds. 10 A.1 Frame Relay virtual connection availability. 10 Annex B Use of Frame Relay STATUS Messages or Alarm Indication as availability criteria. 12 Annex C Use of FR OAM non-latching loopback message
23、s for estimation of Frame Relay connection availability when using connectivity as the outage criteria . 13 C.1 Introduction 13 C.2 The declaration from connection available to connection unavailable 14 C.3 The declaration from connection unavailable to connection available 15 C.4 In-service estimat
24、ion of availability . 15 Annex D Use of FR OAM to monitor Frame Loss Ratio in order to assess availability 15 Annex E Calculation of Mean Network Availability Ratio based on the measurement of individual Virtual Connection Unavailability 16 Appendix I Sampling estimation of PVC availability paramete
25、rs 17 I.1 A minimal test for PVC service availability. 17 I.2 Procedures for estimating PVC service availability. 17 I.3 Procedures for estimating mean time between PVC service outages. 17 ITU-T Rec. X.147 (10/2003) 1 ITU-T Recommendation X.147 Frame Relay network availability 1 Scope The purpose of
26、 this Recommendation is to define network performance parameters, worst-case objectives and measurement methods, for FR virtual connection availability together with allocations to national and international portions applicable to international frame relay services. The specified parameters and obje
27、ctives apply to Frame Relay connection portions as defined in Figure 2. This Recommendation applies to those networks supporting the service class options of ITU-T Recs X.36 and X.76. (Signalling and service class interworking issues are covered in ITU-T Recs X.36 and X.76.) The 3 3 performance matr
28、ix defined in ITU-T Rec. X.134 (see Figure 1) is used as a guide to identify the applicability of this Recommendation. This Recommendation applies to both permanent and switched virtual connections. An international Frame Relay virtual connection consists of two national portions and one internation
29、al portion. The international portion may also be subdivided into a number of connection portions transit network sections and interoperator circuit sections. A two-state availability model is defined along with criteria for determining if the service during specific periods of time should be declar
30、ed to be either available or unavailable. A number of procedures are defined in order to assess the availability performance of virtual connections. An expression for determining a value for overall network availability is presented. Using this Recommendation, worst-case performance objectives can b
31、e derived for the national portions and the international portion of an international Frame Relay connection. Methods for estimating end-to-end availability performance are also provided. The objectives specified in this Recommendation, which are worst-case values, are intended to assist service pro
32、viders with network planning by limiting the aggregate effect of network impairments, including congestion, equipment failures and transmission errors, on Frame Relay virtual connection availability. They do not directly correspond to the level of Quality of Service to be expected by individual cust
33、omers. This Recommendation defines the availability of a Frame Relay connection in a way that is independent of user behaviour (i.e., a connection can be declared unavailable even if the user is not transmitting frame at a given time). Availability objectives need not be met on any connection that a
34、 network provider has determined to be non-compliant with the traffic contract defined by the CIR and EIR. 2 ITU-T Rec. X.147 (10/2003) X.147_F1Physicalinterface(Frame relaynetwork)DSE DSENetwork sectionDTEorDSECircuit sectionDTEorDSEFrame transfer reference eventsFunctionAccess(call set-up)Userinfo
35、rmationtransferDisengagement(call tear-down)Speed DependabilityAccuracyX.144 and X.146CriterionServiceavailable(no outage)AvailabilityServiceavailable(outage)PhysicalinterfacePhysicalinterfacePhysicalinterfaceX.144X.147X.145X.145Figure 1/X.147 Scope of this Recommendation ITU-T Rec. X.147 (10/2003)
36、3 X.147_F2AccessnetworksectionAccesscircuitsectionDTENational portion National portionInternational portionOne or more(optional)Inter-networkcircuitsectionTransitnetworksectionInter-networkcircuitsectionTransitnetworksectionInter-networkcircuitsectionAccessnetworksectionAccesscircuitsectionInter-net
37、workcircuitsectionTransitnetworksectionDTENationalborderNationalborder(optional)Zero or more(optional)One or more(optional)International virtual connection (end-to-end)International virtual connection (edge-to-edge)Portion boundarySection boundaryFigure 2/X.147 General Reference model for the apport
38、ionment of national and international portions of a multiple-network international Frame Relay virtual connection 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
39、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. A li
40、st 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 X.36 (2003), Interface between Data Terminal Equipment (DTE) and Data Circu
41、it-Terminating Equipment (DCE) for public data networks providing frame relay data transmission service by dedicated circuit. 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.
42、140 (1992), 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 perfor
43、mance parameters 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 networ
44、ks providing the international frame relay service. 4 ITU-T Rec. X.147 (10/2003) ITU-T Recommendation X.151 (2003), Frame Relay operations and maintenance Principles and functions. Frame Relay Forum Technical Committee: FRF.19 (2001), Frame Relay Operations, Administration and Maintenance Implementa
45、tion Agreement. 3 Definitions The terms and definitions used in this Recommendation are consistent with those used in ITU-T Recs X.140, X.144, X.145 and X.146 and in FRF.19. Specific definitions for Service Availability/Availability Ratio and Mean Time Between Service Outages are given in 7.5. 4 Abb
46、reviations This Recommendation uses the following abbreviations: ACS Access Circuit Section ANS Access Network Section CEP Connection set-up Error Probability CFP Connection set-up Failure Probability CIR Committed Information Rate DE Discard Eligible DSE Data Switching Exchange DTE Data Terminal Eq
47、uipment EFR Extra Frame Rate EIR Excess Information Rate FE Frame Layer Reference Event FLR Frame Loss Ratio FROMP Frame Relay OAM Maintenance Point FTD Frame Transfer Delay ICS Internetwork Circuit Section ISC International Switching Centre MP Measurement Point MTBSO Mean Time Between Service Outag
48、es MTTSR Mean Time To Service Restoral NNI Network-to-Network Interface PDP Premature Disconnect Probability PDSP Premature Disconnect Stimulus Probability PVC Permanent Virtual Circuit RFER Residual Frame Error Ratio SA Service Availability SVC Switched Virtual Circuit TE Terminal Equipment ITU-T R
49、ec. X.147 (10/2003) 5 TNS Transit Network Section 5 Conventions No specific conventions apply 6 General Frame Relay performance reference model The performance model for this Recommendation is consistent with that used in ITU-T Recs X.144 and X.145. For completeness, this performance model is illustrated in Figure 2. An end-to-end international Frame Relay virtual connection consists of two national portions and one international portion. In certain cases, the international portion could consist solely of an in
