1、Implementation of ISOLEC 11573 : 1994 Information technology - Telecommunications and information exchange between systems - Synchronization methods and technical requirements for Private Integrated Services Networks BS ISO/IEC 11573 : 1994 BSI BS*ISO/IEC 11573 74 = 1624667 0464504 925 BS ISO/IEC 11
2、573 : 1994 Committees responsible for this British Standard The preparation of this British Standard was entrusted to Technical Committee IST/6, Data communications, upon which the foilowing bodies were represented This British Standard, having been prepared under the direction of the Information Sy
3、stems Technology Assembly (i/-), was pubiished under the authority of the Standards Board and comes into effect on 15 May 1995 O ES1 1995 British Computer Society British Telecommunications plc CCTA (the Government Centre for Information Systems) DigitaJ Equipment Co Ltd. IBM United Kingdom Ltd. Ins
4、titution of Electrical Engineers International Computers Limited Logica UK Ltd. Nine ?Iles Computer Systems Ltd. Fhk Xerox UK Ltd. Amendments issued since publication I Text affected The following BSI references relate to the work on this standard Committee reference IST/6 Draft for comment 92/66853
5、 DC ISBN O 680 24098 3 BSI BS*ISO/IEC 11573 94 1624667 0464505 BbL = BS IS0 IEC 11573 : 1994 National foreword This British Standard reproduces verbatim JSOAEC 11573 : 1994 and implements it as the UK national standard. This British Standard is published under the direction of the information System
6、s Technology Assembly whose Technical Committee IST/6 has the responsibility to: - aid enquirers to understand the text; - present to the responsible international committee any enquiries on interpretation, or proposais for change, and keep UK interests informed; - monitor related international and
7、European developments and promulgate them in the UK NOTE. International and European Standards, as well as overseas standards, are available from Customer Services, BSI, 389 Chiswick High Road, London W4 4AL. Compliance with a British Standard does not of itself confer immunity from legal obligation
8、s. i I N T E R NAT I O NA L S TA N DA R D ISOJIEC 11573 First edition 1994-1 2-1 5 Information technology - Telecommunications and information exchange between systems - Synchronization methods and technical requirements for Private Integrated Services Networks Technologies de linformation - Tlcommu
9、nications et change dinformation entre systmes - Mthodes de synchronisation et exigences techniques pour les rseaux privs avec intgration de services Reference number ISO/IEC 11 573:1994(E) ISO/IEC 11573:1994(E) Contents Section 1 : General 1.1 Scope 1.2 Definitions . 1.3 Abbreviations and acronyms
10、. 1.4 Impact of slips . 2.1 Technical requirements . 2.1.1 Jitter and wander at the input . 2.1.1.1 CO and TO interfaces (1 44 kbits/s) 2.1.1.2 C1 and T1 interfaces (1. 544 Mbits/s) . 2.1.1.3 C2 and T2 interfaces (2. 048 Mbits/s) . 2.1.2 Jitter and wander at the output 2.1.2.1 CO and TO interfaces (
11、1 44 kbits/s) 2.1.2.2 C1 and T1 interfaces (1, 544 Mbits/s) . 2.1.2.3 C2 and T2 interfaces (2. 048 Mbits/s) . 2.1.3 Frequency deviation at the input 2.1.4 Accuracy . 2.1.5 Lock range . 2.1.6 Phase discontinuity of slave clocks 2.2 Synchronization methods for PISNs 2.2.1 High level concepts . 2.2.2 R
12、eference Clock Switching Criteria 2.2.3 Reference Restoral 2.2.4 Timing Reference Interfaces and Alarms . 2.2.5 Buffers . 2.2.6 Controls . 2.2.7 Slip performance objectives 2.2.8 Strategies Section 3 : Description of the synchronization methods 3.1 Plesiochronous operation . 3.2 Synchronization from
13、 one input 3.3 Automatic switch over with signalling . 3.4 Automatic switch over without signalling Section 2 : Technical requirements, Synchronization methods . . Annexes A Choice of clock references A.l Choice of reference from public nodes A.2 Choice of references between private nodes . A.3 Avoi
14、dance of Timing Loops B.l Master Slave configurations (synchronization) . 8.2 master-master configuration (split timing) . B Synchronization configuration Page 5 5 5 5 6 6 6 6 7 7 7 7 7 8 8 8 9 9 9 9 9 10 11 11 12 12 13 14 15 16 17 O ISO/IEC 1994 All rights reserved . Unless otherwise specified. no
15、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 the publisher . Printed in Switzerland ISO/IEC Copyright Office Case Postale 56 CH-1211 Genve 20 Switzerland BSI BS*I
16、SO/IEC 11573 74 1bZ4bb9 0464508 570 ISOIIEC 11573:1994(E) C Basis of strategies C.l Slip rate . C.2 Allocation of the controlled slips C.4 Nodal solutions C.5 Description of the five options D Synchronized Private Network Examples C.3 Unavailability of the links D.l Example with a small private netw
17、ork D.2 Example with a big private network . D.3 Example with two different public clock sources D.4 Example with a transit node E Slave Clock Performance Measurement Guidelines E.l Slave Clocks considerations . E.l.l Ideal Operation . E.1.2 Stressed Operation E.1.3 Holdover Operation . E.2 Test Con
18、figuration Guidelines E.2.1 Reference Clock E.2.2 Digital Reference Simulation E.2.3 Output Timing Signal Recovery . E.3 Test categories . E.3.1 Ideal Testing E.3.2 Stress Testing E.3.3 Holdover Testing F Signalling for management of synchronization E1 Presentation E1.1 Configuration parameters E1.2
19、 Reactions of the node F.1.3 Reference clock switching and restoral . - . F.2 Description of the states . F.2.1 Initial states . E2.2 Slave states . F.2.3 Autonomous state . F.2.4 Wait states F.3 Description of the events . E3.1 Failure of links F.3.2 Signalling information F.3.3 Time out . F.4 SDL
20、representation of the state machine . G Bibliography . 18 18 19 20 21 22 22 23 23 24 24 25 25 25 25 26 26 26 26 26 27 28 28 28 28 28 28 29 29 29 29 29 29 29 29 34 . 111 BSI BS*ISO/IEC 11573 94 1624669 0464509 407 W ISO/IEC 11573:1994(E) Foreword IS0 (the International Organization for Standardizatio
21、n) and IEC (the International Electrotechnical Commission) form the specialized system for worldwide standardization. National bodies that are members of IS0 or IEC participate in the development of International Standards through technical committees established by the respective organization to de
22、al with particular fields of technical activity. IS0 and IEC technical committees collaborate in fields of mutual interest. Other international organizations, governmental and non-governmental, in liaison with IS0 and IEC, also take part in the work. In the field of information technology, IS0 and I
23、EC have established a joint technical committee, ISO/IEC JTC 1. Draft International Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as an International Standard requires approval by at least 75% of the national bodies casting a vote. Inter
24、national Standard ISO/IEC 11 573 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology, Subcommittee SC 6, Telecommunications and information exchange between systems. During the preparation of this International Standard, information was gathered on patents upon which appl
25、ication of the standard might depend. Relevant patents were identified as belonging to ALCATEL Business Systems. However, IS0 and IEC cannot give authoritative or comprehensive information about evidence, validity or scope of patent and like rights. The patent-holder has stated that licences will be
26、 granted under reasonable terms and conditions and com- munications on this subject should be addressed to ALCATEL Business Systems Business Products Division 54, avenue Jean Jaurs 92707 Colombes Cedex France Tel. : (1) 47.85.55.55 Telex: 615.531 F Telefax: (1) 47.85.54.20 IV BSI BS*ISO/IEC 31573 94
27、 = lb24bb DVb45LO 129 M ISO/IEC 11573:1994(E) Introduction When synchronous digital signals are being transported over a communications link, the receiving end must operate at the same average frequency as the transmitting end to prevent loss of information. This is referred to as link synchronizati
28、on. When digital signals traverse a network of digital communications links, switching nodes, multiplexers, and transmission interfaces, the task of keeping all the entities operating at the same average frequency is referred to as network synchronization. The design of a PISN requires specification
29、 of the timing sources and receivers for the synchronization network. Proper design requires that timing loops in the synchronization network be avoided. A timing loop occurs when a clock is using as its reference frequency a signal that is itself traceable to the output of that clock. The formation
30、 of such a closed timing loop leads to frequency instability and is not permitted. While it is relatively straightforward to ensure against timing loops in the primary synchronization reference network, care should be taken that timing loops do not occur during failure or error conditions when vario
31、us timing references are rearranged. When a PISN is not connected to the public digital network, synchronization can be achieved by having all PISN equipment derive timing from a single source.This source should be the highest quality clock available. Alternatively, if timing is derived from more th
32、an one class I clock, or public clock traceable source, the network is said to be operating plesioc hronously. If a PISN is connected to the public network at one or more nodes, the private network designer can coordinate with the public network provider to derive class I clock, or public clock trac
33、eable timing from the public digital network. More information is available in Annex A. V BSI BS*ISO/IEC 33573 94 M Lb2Ybb9 04b4533 Ob5 INTERNATIONAL STANDARD ISO/IEC 11573:1994(E) Information technology - Telecommunications and information exchange between systems - Synchronization methods and tech
34、nical requirements for Private Integrated Services Networks Section 1 : General 1.1 Scope This international Standard contains requirements necessaryforthesynchronization of PISNs. Timing withinadigital private networkneedsto becontrolledcarefullytoensurethatthe rateofoccurrenceof slips between PINX
35、s withinthe PISN,andthe public switched networks is sufficiently low not to affect unduly the performance of voice transmissions, or the accuracy or throughput (if errored data require re-transmission) of non-voice services. Requirements are also based upon the interconnection of digital privatetele
36、communication networksviadigital facilities in the public (switched or not) telecommunication networks. This International Standard is one of a series of technical standards on telecommunications networks. This international Standard with its companion standards fills a recognized need in the teleco
37、mmunications industry brought about by the increasing use of digital equipment and facilities in private networks. It is useful to anyone engaged in the manufacture of digitalcustomerpremisesequipment (CPE) forprivatenetworkapplications, andtothosepurchasing, operating orapplying digital CPE to digi
38、tal facilities for Private Integrated Services Networks (PISN). This International Standard establishes technical criteria necessary in the design of a synchronization plan for a PEN. Compliance with these requirements would be expected to result in a quality PISN synchronization design. 1.2 Definit
39、ions For the purposes of this International Standard, the following definitions apply: 1.2.1 Accuracy A measure of the maximum departure from the nominal clock rate over a 24 h period, made anytime in the lifetime of the clock, during a defined period of time, within the declared environmental condi
40、tions. Frequency deviation may be constrained to the specific accuracy by clock operation in the free running or hold over modes, as defined below. 1.2.2 Asynchronous signals Signals having not the same nominal rate. 1.2.3 Clock free running mode In such a mode, the PINX works with its own clock sou
41、rce which is not locked to an external reference and is not using storage techniques to maintain its accuracy. 1.2.4 Clock hold over mode An operating condition of a clock in which it is not locked to an external reference clock, but uses storage techniques to maintain during a limited period of tim
42、e its accuracy with respects to the last known reference clock. 1.2.5 Controlled Slip it consists of the repetition or deletion of an integer number of octets caused by the elastic buffer mechanism used at the interface of a non-synchronous bit stream (a plesiochronous or asynchronous one). Slips an
43、d controlled slips shall be considered synonymous in this International Standard. 1.2.6 Jitter Short-term non-cumulative variations of the significant instants of a digital signal from their ideal positions in time. 1 BSI BS*ISO/IEC 11573 94 W 1624bb O464512 TT1 ISOIIEC 11573:1994(E) 1.2.7 Lock rang
44、e Maximum frequency offset from the nominal, to which a given clock is able to synchronize. 1.2.8 Master The term “master“ refers to the clock source providing the timing to the PINX. 1.2.9 Maximum time Interval error (MTIE) The maximum time interval error (TIE) for all possible measurement interval
45、s within the measurement period. Figure 1 illustrates the definition of MTIE. 1.2.1 O Phase Locked Loop (PLL) A feedback-controlled system that locks a local clock to an incoming reference clock in both frequency and phase. 1.2.1 1 Plesiochronous The essential chracteristicof time-scalesor signalssu
46、ch as their Corresponding significant instants occur at nominallythe same rate, any variation in rate being constrained within specified limits. 1.2.12 Primary Reference Clock Equipment that provides a timing signal, with a long term accuracy equal or better than 1.2.1 3 Puli in range Maximum freque
47、ncy offset from its own clock, to which a given clock is able to synchronize. 1.2.1 4 Reference Clock Timing signal used for synchronization, without any assumption on its accuracy. 1.2.15 Slave The term “slave“ refers to the PINX receiving timing from another source. 1.2.16 Slip Refer to controlled
48、 slip 1.2.1 7 Split Tlming An arrangementwhere equipment employsseparatetransmitand receiveclocksonatransmission link having no particular relationship to one another. 1.2.1 8 Synchronous Qualifies signals with corresponding significant instants occuring atthe same mean rate; the timedifference betw
49、een these homologous instants is generally limited. 1.2.1 9 Synchronization The process of adjusting the corresponding significant instants of signals so that a constant phase relationship exists between them. 1.2.20 Time-interval Error (TIE) Thevariation intimedelay of agiven timing signal with respecttoan ideal timingsignaloveraparticulartimeperiod. Figure 1 illustrates the definition of TIE. 1.2.21 Timing loop An unstable condition in which two or more equipment clocks transfer timing to each other, forming a loop without a designated master timing sou
