1、INTERNATIONAL TELECOMMUNICATION UNION ITU=T TELECOMMUNICATION STANDARDIZATION SECTOR OF ITU X.134 (08197) SERIES X: DATA NETWORKS AND OPEN SYSTEM COM M U NI CATI ON Public data networks - Network aspects Portion boundaries and pac ket-lay er reference events: Basis for defining packet-switched perfo
2、rmance parameters ITU-T Recommendation X. 134 (Previously CCITT Recommendation) STD-ITU-T RECMN X-134-ENGL 1997 - 48b2591 Ob39705 115 ITU-T X-SERIES RECOMMENDATIONS DATA NETWORKS AND OPEN SYSTEM COMMUNICATION PUBLIC DATA NETWORKS Services and facilities Administrative arrangements OPEN SYSTEM INTERC
3、ONNECTION Model and notation X.200-X.209 Service definitions X.210-X.219 Connection-mode protocol specifications X.220-X.229 Connectionless-mode protocol specifications X.230-X.239 Protocol Identification Security Protocols Layer Managed Objects Conformance testing X.290-X.299 INTERWORKING BETWEEN N
4、ETWORKS Satellite data transmission systems MESSAGE HANDLING SYSTEMS X.400-X.499 DIRECTORY OS1 NETWORKING AND SYSTEM ASPECTS X.630-X.649 Naming, Addressing and Registration Abstract Syntax Notation One (ASN. 1) Systems Management framework and architecture Management Communication Service and Protoc
5、ol Structure of Management Information Management functions OS1 MANAGEMENT OS1 APPLICATIONS Commitment, Concurrency and Recovery Transaction processing Remote operations OPEN DISTRIBUTED PROCESSING For further details, please refir to ITU-T List of Recommendations. ITU-T RECOMMENDATION X.134 PORTION
6、 BOUNDARIES AND PACKET-LAYER REFERENCE EVENTS: BASIS FOR DEFINING PACKET-SWITCHED PERFORMANCE PARAMETERS Summary This Recommendation provides the performance model for the X.130-Series Recommendations on PSPDN perfonnance. Source ITU-T Recommendation X.134 was revised by ITU-T Study Group 7 (1997-20
7、00) and was approved under the WSC Resolution No. 1 procedure on the 9th of August 1997. Recommendation X.134 (08/97) - i STD-ITU-T RECMN X-134-ENGL 1777 4862573 Ob37707 T78 D FOREWORD IT (international Telecommunication Union) is the United Nations Specialized Agency in the field of telecommuni- ca
8、tions. The IT Telecommunication Standardization Sector (IT-T) is a permanent organ of the IT. The IT-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 Telecommuni
9、cation Standardization Conference (WTSC), which 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 IT-T is covered by the procedure laid down in WTSC R
10、esolution No. 1. in some areas of information 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 adminis
11、tration and a recognized operating agency. INTELLECTUAL PROPERTY 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 IT takes no position concerning the evidence, validity or ap
12、plicability of claimed Intellectual Property Rights, whether asserted by IT members or others outside of the Recommendation development process. As of the date of approval of this Recommendation, the IT hadhad not received notice of intellectual property, protected by patents, which may be required
13、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. O ITU 1997 All rights reserved. No part of this publication may be reproduced or utilized in any form or by an
14、y means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the ITLJ. 11 Recommendation X.134 (08/97) CONTENTS Page 1 Introduction 1 2 References 3 3 Abbreviations . 3 4 Virtuai connection sections and portions . 4 5 Packet-layer reference events . 4 5
15、.1 Definitions 4 5.2 Performance-significant reference events . 5 Recommendation X.134 (08/97) . 111 STD-ITU-T RECMN X-134-ENGL L977 48b259L Ob37709 8hO Recommendation X.134 PORTION BOUNDARIES AND PACKET-LAYER REFERENCE EVENTS: BASIS FOR DEFINING PACKET-SWITCHED PERFORMANCE PARAMETERS (revised in 19
16、97) 1 Introduction 1.1 This Recommendation is the first in a series of four Recommendations (X.134 to X.137) that define performance parameters and values for international packet-switched data communication services. Figure 1 illustrates the scope of these four Recommendations and the relationships
17、 among them. 1.2 This Recommendation divides a virtual connection into basic sections whose boundaries are associated withX.25 and X.75 interfaces. The performance of collections of these basic sections can be estimated using the packet-switched performance parameters defined in Recommendations X. 1
18、35 to 137 and the measurement techniques defined in Recommendations X.138 and X.139. In order to apportion the performance of an international virtual connection, this Recommendation defines two particular collections of basic sections for which performance values will be specified: national portion
19、s and international portions. As defined, every international virtuai connection contains two national portions and one intemational portion. The performance of these three portions can be combined in the calculation of the end-to-end virtual connection performance. These Recommendations do not spec
20、ifi performance values for other collections of basic sections; however, the ability to decompose a virtual connection into its basic sections will be useful in planning the performance of national and international portions. 1.3 The performance parameters in Recommendations X.135 to X.137 are defin
21、ed in terms of packet-layer reference events which can be observed at the boundaries between basic sections and thus can be observed at the portion boundaries. This Recommendation defines the performance significant packet-layer reference events. 1.4 For comparability and completeness, packet-switch
22、ed 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 defined in the matrix: access, user information transfer, and disengagement. These general functions correspond to call Se
23、t-up, data (and interrupt) transfer, and call clearing in packet-switched virtual call services conforming to Recommendations X.25 and X.75. Each function is considered with respect to three general performance concerns (or “performance criteria“): speed, accuracy, and dependability. These express,
24、respectively, the delay or rate, degree of correctness, and degree of certainty with which the function is performed. 1.5 Recommendation X. 135 defines protocol-specific speed of service parameters and values associated with each of the three data communication functions. Recommendation X.136 define
25、s protocol-specific accuracy and dependability parameters and values associated with each function. X.135 and X.136 parameters are called “primary parameters“ to emphasize their direct derivation from packet-layer reference events. 1.6 An associated two-state model provides a basis for describing ov
26、erall service availability. A specified availability function compares the values for a subset of the primary parameters with corresponding outage thresholds to classi the service as “available“ (no service outage) or “unavailable“ (service outage) during scheduled service time. Recommendation X.137
27、 specifies the availability function and defines the availability parameters and values that characterize the resulting binary random process. 1.7 receivable at points within the scope of the DTEs, further elements must be included. in order to relate the network performance values given in Recommen
28、dations X.135 to X.137 to the service Recommendation X.134 (08197) 1 STD-ITU-T RECMN X*L34-ENGL 1.7.1 In particular, specification of service performance at the layer 3/4 boundary (OS1 Network service) must include those processes within the DTEs concerned with the transfer of packets from the physi
29、cal circuit of the DTEDCE interface to the layer 314 boundary at each end of the virtual connection, however they may be implemented. This processing may include elements associated with OS1 layers 1,2 and 3 and may involve transmission across private wide-area and/or local-area networks. 1.7.2 Spec
30、ification of service performance for the user or application, if required, must similarly include in addition, those processes within the DTEs concerned with the transfer of information from the layer 314 boundary to the layer 7 upper boundary beyond each end of the virtual connection, however they
31、may be implemented. This processing may include elements associated with OS1 layers 4,5,6 and 7. 1.7.3 Additional protocol- or service-specific reference events would need to be defined to cover these aspects, but are outside the scope of this Recommendation. However, the parameter definitions of Re
32、commendations X.135 to X.137 can readily be adapted to correspond to any extension of scope. Rec. X.134 I 1 Network section (Packet network) u Circuit section DTE DSE (X.25 or X.75) I Physical interface Physical interface Physical interface Physical interface ! ! ! 1 +- -+-!-+= -+-y- I / I (Packet-l
33、ayer reference events) Rec. X.136 available X.137 unavailable T071494J-931dOl Figure 1K.134 - Packet-switched service performance description framework 2 Recommendation X.134 (08/97) STD-ITU-T RECMN X.13Y-ENGL I997 m 48b2591 Ob39733 439 2 References The following IT-T Recommendations and other refer
34、ences contain provisions which, through reference in this text, constitute provisions of this Recommendation. 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
35、investigate 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,
36、 public data networks and Integrated Services Digital Networks (ISDNs). ITU-T Recommendation X.2 (1 996), International data transmission services and optional user facilities in public data networks and ISDNs. ITU-T Recommendation X.25 (1996), Interface between Data Terminal Equipment (DTE) and Dat
37、a Circuit- terminating Equipment CE) for terminals operating in the packet mode and connected to public data networks by dedicated circuit. ITU-T Recommendation X.75 (1 996), Packet-switched signalling system between public networks providing data transmission services. ITU-T Recommendation X.96 (19
38、93), Callprogress signals in public data networks. ITU-T Recommendation X. 110 (1996), International routingprinciples and routingplan for public data networks. ITU-T Recommendation X.135 (1997), Speed of service (delay and throughput) performance values for public data networks when providing inter
39、national packet-switched services. ITU-T Recommendation X. 136 (1997), Accuracy and dependability performance values for public data networks when providing infernational packet-switched services. IT-T Recommendation X. 137 (1997), Availability performance values for public data networks when provid
40、ing internat ional packet-switched services. ITU-T Recommendation X.138 (1997), Measurement of performance values for public data networks when providing international packet-switched services. ITU-T Recommendation X.139 (1997), Echo, drop, generator and test DTEs for measurement of performance valu
41、es in public data networh when providing international packet-switched services. CCITT Recommendation X. 140 (1992), General quality of service parameters for communication via public data networks. ITU-T Recommendation X.2 13 (1999, Information technology - Open Systems Interconnection - Network se
42、rvice definition. CCITT Recommendation X.323 (1 988), General arrangements for interworking between Packet-Switched Public Data Networks (PSPDNs) . Abbreviations This Recommendation uses the following abbreviations: DCE Data Circuit-terminating Equipment DSE Data Switching Exchange DTE Data Terminal
43、 Equipment REJ Reject RNR Receive Not Ready RR Receive Ready STE Signalling Terminai Equipment Recommendation X.134 (08/97) 3 - STD-ITU-T RECMN X-134-ENGL 1997 W 48b2591 b39712 355 4 Virtual connection sections and portions in the context of Recommendations X.134 to X.137, the following definitions
44、apply: An access circuit section is the physical circuit or set of circuits connecting a DTE to the local DSE. It does not include any parts of the DTE or DSE. These Recommendations assume that X.25 procedures are used on an access circuit section. An internetwork circuit section is the physical cir
45、cuit or set of circuits, connecting a DSE in one network with a DSEin a different network. It does not include any parts of either DSE. These Recommendations assume that X.75 procedures are used on an internetwork circuit section. A circuit section is either an access circuit section or an internetw
46、ork circuit section. A network section consists of the network components that provide a vdl connection between two circuit sections. The network provider is responsible for the performance of the network section. An access network section is a network section connected to (at least) one access circ
47、uit section. A transit network section is a network section between two internetwork circuit sections. A basic section of a virtual connection is either an access network section, a transit network section, an access circuit section, or an intemetwork circuit section. A section boundary (or boundary
48、) separates a network section fiom the adjacent circuit section or it separates an access circuit section fiom the adjacent DTE. A national portion of an international virtual connection is a collection of adjacent alternating network sections and circuit sections entirely within the borders of one
49、nation. The national portion connects a DTE to an internetwork circuit section that crosses the national border. The national portion includes the access circuit section and excludes the internetwork circuit section that crosses the national border. A national portion always includes one access circuit section and one access network section, and it may include one or more pairs of internetwork circuit sections and transit network sections. There are two national portions of any intemational virtual circuit. An international portion of an internation
