1、 STD-ITU-T RECMN X-13b-ENGL 1997 D 48b2591 Ob39719 7UT INTERNATIONAL TELECOMMUN CATION UN ION ITU-T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU X.136 (08/97) SERIES X: DATA NETWORKS AND OPEN SYSTEM CO MM U N IC ATION Public data networks - Network aspects Accuracy and dependability performance v
2、alues for public data networks when providing international packet-switched services ITU-T Recommendation X.136 (Previously CCITT Recommendation) ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATION PUBLIC DATA NETWORKS Services and facilities In terfaces x.1-x.199 x.l-x.19 X.2
3、-X.49 Transmission, signalling and switching X.50-X.89 Maintenance Administrative arrangements OPEN SYSTEM INTERCONNECTION Model and notation Service definitions Connection-mode protocol specifications Connectionless-mode protocol specifications PICS proformas Protocol Identification security Protoc
4、ols Layer Managed Objects Conformance testing General Satellite data transmission systems MESSAGE HANDLING SYSTEMS DIRECTORY OS1 NETWORKING AND SYSTEM ASPECTS Networking Efficiency Naming, Addressing and Registration Abstract Syntax Notation One (ASN.l) Systems Management framework and architecture
5、Management Communication Service and Protocol Structure of Management Information Management functions INTERWORKING BETWEEN NETWORKS OS1 MANAGEMENT SECURITY OS1 APPLICATIONS Commitment, Concurrency and Recovery Transaction processing Remote operations OPEN DISTRIBUTED PROCESSING X. 150-X. 179 - X.18
6、0-X.199 X.200-X.299 X.200-X.209 X.210-X.219 X.220-X.229 X.23-X.239 X.240-X.259 X.260-X.269 X.270-X.279 X.280-X.289 X.290-X.299 x.300-x.399 x.300-x.349 x.350-x.399 x.400-x.499 X.500-X.599 X.600-X.699 X.600-X.629 X.630-X.649 X.650-X.679 X.68-X.699 X.700-X.799 X.700-X.709 X.710-X.719 X.720-X.729 x.730-
7、x.799 X.800-X. 849 X.850-X.899 X.850-X.859 X.860-X.879 X. 880-X. 899 x.900-x.999 For further details, please refer to ITU-TList of Recommendations. STDaITU-T RECMN X-13b-ENGL 1777 Lib2591 Ob39721 3bB m ITU-T RECOMMENDATION X.136 ACCURACY AND DEPENDABILITY PERFORMANCE VALUES FOR PUBLIC DATA NETWORKS
8、WHEN PROVIDING INTERNATIONAL PACKET-SWITCHED SERVICES Summary This Recommendation provides accuracy and dependability parameters and associates worst-case objectives within the X. 130-Series Recommendations on PSPDN performance. Source ITU-T Recommendation X.136 was revised by -T Study Group 7 (1997
9、-2000) and was approved under the WTSC Resolution No. 1 procedure on the 9th of August 1997. * Recommendation X.136 (08/97) 1 FOREWORD ITU (International Telecommunication Union) is the United Nations Specialized Agency in the field of telecommuni- cations. The ITU Telecommunication Standardization
10、Sector (ITU-T) is a permanent organ of the U. The ITU-T is responsible 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 Conference (WTSC), which
11、 meets every four years, establishes the topics for study by the ITU-T Study Groups which, in their turn, produce Recommendations on these topics. - The approval of Recommendations by the Members of the ITU-T is covered by the procedure laid down in WTSC Resolution No. 1. In some areas of informatio
12、n technology which fall within ITU-Ts purview, the necessary standards are prepared on a collaborative basis with IS0 and IEC. NOTE In this Recommendation, the expression “Administration“ is used for conciseness to indicate both a telecommunication administration and a recognized operating agency. I
13、NTELLECTUAL PROPERW RIGHTS The ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. The ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property
14、 Rights, whether asserted by ITU members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, the ITU hadfhad not received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However
15、, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database. I O ITU 1997 Ali rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, incl
16、uding photocopying and microfilm, without permission in writing from the ITU. 11 Recommendation X136 (08/97) STD-ITU-T RECMN XaL3b-ENGL 2777 D 48b259L Ob37723 130 CONTENTS Introduction and scope . References Abbreviations . Access parameters 4.1 4.2 Call Set-up error probability Call Set-up failure
17、probability . User information transfer parameters 5.1 Residual error ratio . 5.2 Reset parameters . . 5.3 Premature disconnect parameters . Disengagement performance - Call clear failure probability . 6.1 Call clear failure probability definition . 6.2 Values . 6.3 Local clear confirmation . Annex
18、A . Ancilliary information on accurancy and dependability measurement . Annex B - Representative end-to-end accuracy and dependability performance . B.l B.2 Definition of the example end-wend connections . End-to-end accuracy and dependability performance for the type 1 and type 2 configuration exam
19、ples . B.3 Notes on key assumptions. results and implications . Recommendation X.136 (08/97) Page 1 3 4 4 4 6 6 7 8 10 11 12 12 12 13 15 15 15 16 . 111 STD-ITU-T RECMN X.13b-ENGL 1977 48b2571 Ob37724 077 Recommendation X.136 ACCURACY AND DEPENDABILITY PERFORMANCE VALUES FOR PUBLIC DATA NETWORKS WHEN
20、 PROVIDING INTERNATIONAL PACKET-SWITCHED SERVICES (revised in 1997) 1 Introduction and scope - 1.1 This Recommendation is the third in a series of four Recommendations (X.134 to X.137) that define perfor- mance parameters and values for international packet-switched data communication services. Figu
21、re 1 illustrates the scope of these four Recommendations and the relationships among them. 1.2 Recommendation X. 134 divides a virtual connection into basic sections whose boundaries are associated with X.25 and X.75 interfaces; defines particular collections of basic sections, called virtual connec
22、tion portions, for which performance values will be specified; and defines a set of packet-layer reference events (PES) which provide a basis for performance parameter definition. The basic sections consist of network sections and circuit sections. They are deli- mited, in each case, by physical Dat
23、a Terminal Equipment (DTE) or Data Switching Equipment (DSE) interfaces. Virtual connection portions are identified either as national portions or international portions. Each PE is defined to occur when a packet, crossing a section boundary, changes the state of the packet-layer interface. 1.3 For
24、comparability and completeness, packet-switched network performance is considered in the context of the 3 x 3 performance matrix defined in Recommendation X. 140. Three protocol-independent data communication functions are identified in the matrix: access, user information transfer, and disengagemen
25、t. These general functions correspond to call Set-up, data (and interrupt), transfer, and call clearing in packet-switched virtual call services conforming to the Recommendations X.25 and X.75. Each function is considered with respect to three general performance concerns (or “performance criteria”)
26、: speed, accuracy, and dependability. These express, respectively, the delay or rate, degree of correctness, and degree of certainty with which the function is performed. 1.4 Recommendation X.135 defines protocol-specific speed of service parameters and values associated with each of the three data
27、communication functions. This Recommendation defines protocol-specific accuracy and dependability parameters and values associated with each function. The Recommendation X. 135 parameters and this Recommendation parameters are called ”primary parameters” to emphasize their direct derivation from pac
28、ket-layer reference events. 1.5 An associated two-state model provides a basis for describing overall service availability. A specified availability function compares the values for a subset of the primary parameters with corresponding outage thresholds to classify the service as ”available” (no ser
29、vice outage) or “unavailable” (service outage) during scheduled service time. Recommendation X. 137 specifies the availability function and defines the availability parameters and values that characterize the resulting binary random process. 1.6 Eight accuracy and dependability parameters are define
30、d in this Recommendation: two access parameters (call set-up error probability and call Set-up failure probability), five user information transfer parameters (residual error ratio, reset stimulus probability, reset probability, premature disconnect stimulus probability, and premature disconnect pro
31、bability), and one disengagement parameter (call clear failure probability). Each parameter can be applied to any basic section or portion of a virtual connection. This generally makes the parameters useful in performance allocation and concatenation. 1.7 This Recommendation specifies accuracy and d
32、ependability values for national and international portions of two types (see Table 1). Performance values for data terminal equipment are not specified, but the parameters defined in this Recommendation may be employed in such specification to assist users in establishing quantitative relationships
33、 between network performance and quality of service (see Recommendation X. 140). Recommendation X.136 (08197) 1 STD-ITU-T RECMN X*LYb-ENGL L977 48b259L Ob39725 TU3 / (Packet-layer reference events) I / Rec. X.134 Network section (Packet network) Physical interface Physicalinterface ! ! - -? Circuit
34、section DSE DTE I GE (X.25 or X.75) mom Physical interface Physical interface II ! - Il oc-(- Access informaiion transfer Disenga- gement Speed Accuracy Depejdabiliiy Service Service available X.137 unavailable TO71 56MWd01 Figure 1K.136 - Packet-switched service performance description framework Ta
35、ble 1K.136 - Virtual connection portion types for which performance values are specified) I Typical characteristics I Portion type I National A National B International A Internationai B Terrestrial connection via an access network section. Connection via an access network section with one satellite
36、 circuit; or via an access network section and one or more transit network sections. Connection via a direct terrestrial internetwork section. Connection via two satellite circuits and one transit network section; or via one satellite circuit and two or more transit network sections. a) The values s
37、pecified for type B portions also apply to virtual connection portions not explicitly identified as type A or type B. 2 Recommendation X.136 (08/97) STD.ITU-T RECMN X.13b-ENGL 1777 m 48b2571 Ob3772b 74T H 1.8 Worst-case values for each of the eight accuracy and dependability parameters are specified
38、 below for each virtual connection portion type identified in Table 1. The term “worst case“ means that these values should be met, during any hour of scheduled service time, in the worst performing virtual connection portion used in providing inter- national packet-switched services. The performanc
39、e of a virtual connection portion may be better than the worst-case values specified in this Recommendation. Design objectives that take into account more demanding user applications and network performance and connectivity enhancements are for further study. Numerical methods for combining individu
40、al portion performance values to estimate end-to-end performance are also provided in this Recommendation. DTE to DTE values for two particular hypothetical reference connections are derived using these methods in Annex B. 2 References The following ITU-T Recommendations, and other references contai
41、n provisions which, through reference in this text, constitute provisions of this Recommendation. At the time of publication, the editions indicated were valid. All Recom- mendations and other references are subject to revision; all users of this Recommendation are therefore encouraged to investigat
42、e the possibility of applying the most recent edition of the Recommendations and other references listed below. A list of the currently valid IT-T Recommendations is regularly published. - IT-T Recommendation X. 1 (1996), International user classes of service in, and categories of access to, public
43、data networks and Integrated Services Digital Networks (ISDNs). - ITU-T Recommendation X.2 (1996), International data transmission services and optional user facilities in public data networks and ISDNs. - IT-T Recommendation X.25 (1996), Interface between Data Terminai Equipment (DTE) and Data Circ
44、uit-terminating Equipment CE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit. - IT-T Recommendation X.75 (1996), Packet-switched signalling system between public networks providing data transmission services. - IT-T Recommendation X.96 (1993), C
45、allprogress signals in public data networks. - ITU-T Recommendation X. 1 10 (1996), International routingprinciples and routingplan for public data networks. - IT-T Recommendation X. 134 (1997), Portion boundaries and packet-layer reference events: Basis for defining packet-switched performance para
46、meters. - IT-T Recommendation X.135 (1997), Speed of service (delay and throughput) performance values for public data networks when providing international packet-switched services. - ITU-T Recommendation X. 137 (1997), Availability performance values for public data networks when providing interna
47、tional packet-switched services. - IT-T Recommendation X.138 (1997), Measurement of performance values for public data networks when providing international packet-switched services. - IT-T Recommendation X.139 (1997), Echo, drop, generator and test DTEs for measurement of performance values in publ
48、ic data networks when providing international packet-switched services. - CCIT Recommendation X.140 (1992), General quality of service parameters for communication via public data networks. - IT-T Recommendation X.213 (1995), Information technology - Open Systems Interconnection - Network service de
49、finition. - CCIT Recommendation X.323 (1988), General arrangements for interworking between Packet-Switched Public Data Networks (PSPDNs). Recommendation X.136 (08/97) 3 3 Abbreviations This Recommendation uses the following abbreviations: DCE DSE DTE PE PVC RER vc 4 Data Circuit-terminating Equipment Data Switching Equipment Data Terminal Equipment Packet-layer reference Event Permanent Virtual Circuit Residual Error Ratio Virtual Connection - Access parameters This clause specifies worst-case values for two access parameters: call set
