1、STD-ETSI ETS 300 4b2-3-ENGL 1777 = 3400855 015b243 94T - EUROPEAN 1 ELECOMMUNICATION STANDARD ETS 300 462-3 January 1997 Source: ETSI TC-TM Reference: DE/TM-03017-3 ICs: 33.020 Key words: Synchronization, transmission, network Transmission and Multiplexing (TM); Generic requirements for synchronizat
2、ion networks; Part 3: The control of jitter and wander within synchronization networks ETSI European Telecommunications Standards Institute ETSI Secretariat Postal address: F-O6921 Sophia Antipolis CEDEX - FRANCE Off ice address: 650 Route des Lucioles - Sophia Antipolis - Valbonne - FRANCE X.400: c
3、=fr, a=atlas, p=etsi, %secretariat - internet: secretariat etsi.fr Tel.: +33 4 92 94 42 O0 - Fax: +33 4 93 65 47 16 Copyright Notification: No part may be reproduced except as authorized by written permission. The copyright and the foregoing restriction extend to reproduction in all media. Q Europea
4、n Telecommunications Standards Institute 1997. All rights reserved. STD-ETSI ETS 300 4b2-3-ENGL 1997 3400855 OL5b244 88b Page 2 ETS 300 462-3: January 1997 Whilst every care has been taken in the preparation and publication of this document, errors in content, typographical or otherwise, may occur.
5、If you have comments concerning its accuracy, please write to “ETSI Editing and Committee Support Dept,“ at the address shown on the title page. STD*ETSI ETS 300 4b2-3-ENGL 1777 m 3400855 O15b245 712 m Page 3 ETS 300 462-3: January 1997 Contents Foreword . 5 Scope 7 Normative references 7 Definition
6、s. symbols and abbreviations . 8 3.1 Definitions 8 3.2 Symbols . 8 3.3 Abbreviations . 8 Basic philosophy for the control of jitter and wander . 8 Synchronization interfaces 9 Synchronization reference network . 10 Network limits for jitter and wander at synchronization interfaces 10 7.1 Network lim
7、its for jitter . 11 7.2 Network limits for wander 11 7.2.1 Network limits for wander at PRC outputs 12 7.2.2 Network limits for wander at SSU outputs . 13 7.2.3 Network limits for wander at SEC outputs . 15 7.2.4 Network limits for wander at PDH distribution outputs 16 Annex A (normative): Anti-alia
8、sing filter to be used for the measurement of MTIE and TDEV . 18 A.l Measurement philosophy 18 Filter specification. sampling time and measurement interval 18 Network model underlying the network limit . 20 A.2 Annex B (informative): B.l Introduction 20 B.2 Considerations on the network model . 20 8
9、.3 History 24 Information regarding the simulations . 22 Page 4 ETS 300 462-3: January 1997 Blank page STD-ETSI ETS 300 4b2-3-ENGL 1997 M 3400855 0356247 575 M Transposition dates Date of adoption 3 January 1997 Page 5 ETS 300 462-3: January 1997 Foreword This European Telecommunication Standard (ET
10、S) has been produced by the Transmission and Multiplexing (TM) Technical Committee of the European Telecommunication Standards Institute (ETSI) in order to provide requirements for synchronization networks that are compatible with the performance requirements for digital networks. It is one of a fam
11、ily of ETSs covering various aspects of synchronization networks: Part 1: “Definitions and terminology for synchronization networks“ (ETS 300 462-1). Part 2: “Synchronization network architecture“ (ETS 300 462-2). Part 3: “The control of jitter and wander within synchronization networks“ (ETS 300 46
12、2-3). Part 4: “Timing characteristics of slave clocks suitable for synchronization supply to Synchronous Digital Hierarchy (SDH) and Plesiochronous Digital Hierarchy (PDH) equipment“ (ETS 300 462-4). Part 5: “Timing characteristics of slave clocks suitable for operation in Synchronous Digital Hierar
13、chy (SDH) equipment“ (ETS 300 462-5). Part 6: “Timing characteristics of primary reference clocks“ (ETS 300 462-6). Date of latest publication of new National Standard or endorsement of this ETS (dop/e): 31 October 1997 Date of withdrawal of any conflicting National Standard (dow): 31 October 1997 P
14、age 6 ETS 300 462-3: January 1997 Blank page STD-ETSI ETS 300 qb2-3-ENGL 1797 3900855 OL5b2Li7 368 M Page 7 ETC 300 462-3: January 1997 1 Scope This third part of ETS 300 462 outlines requirements for the control of jitter and wander within synchronization Networks that are constructed according to
15、the architectural principles described in ETS 300 462-2 2. A synchronization network that complies with the network limits for jitter and wander specified in this ETS will be suitable for the synchronization of Synchronous Digital Hierarchy (SDH) and Public Switched Telephone Network (PSTN) networks
16、. It combines the short term stability requirements of SDH networks with the long term stability requirements of the PSTN. The values specified in this ETS refer to the design of new synchronization networks. They do not necessarily represent the performance of existing PSTN synchronization networks
17、. The network limits specified in this ETS form the network requirements from which the clock specifications in ETS 300 462-4 3, ETS 300 462-5 4 and ETS 300 462-6 5 have been derived. 2 Normative references This ETS incorporates by dated and undated reference, provisions from other publications. The
18、se normative references are cited at the appropriate places in the text and the publications are listed hereafter. For dated references, subsequent amendments to or revisions of any of these publications apply to this ETS only when incorporated in it by amendment or revision. For undated references
19、the latest edition of the publication referred to applies. 41 I51 prETS 300 462-1 (1 996): “Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 1 : Definitions and terminology for synchronization networks“. ETS 300 462-2 (1 995): “Transmission and Multiplexing
20、 (TM); Generic requirements for synchronization networks; Part 2: Synchronization network arc hi tect u re“. prETS 300 462-4: “Transmiscion and Multiplexing (TM); Generic requirements for synchronization networks; Pari 4: Timing characteristics of slave clocks suitable for synchronization supply to
21、Synchronous Digital Hierarchy (SDH) and Plesiochronous Digital Hierarchy (PDH) equipment“. ETS 300 462-5 (1 995): “Transmission and Multiplexing (TM); Generic requirements for synchronization networks: Part 5: Timing characteristics of slave clocks suitable for operation in Synchronous Digital Hiera
22、rchy (SDH) equipment“. prETS 300 462-6: “Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 6: Timing characteristics of primary reference clocks“. ITU-T Recommendation G.822: “Controlled slip rate objectives on an international digital connection“. ITU-T Rec
23、ommendation G.823: “The control of jitter and wander within digital networks which are based on the 2 048 kbit/s hierarchy“. ITU-T Recommendation 0.1 71 : “Timing jitter measuring equipment for digital sys terns“. ITU-T Recommendation G.783: “Characteristics of synchronous digital hierarchy (SDH) eq
24、uipment functional blocks“. STD-ETSI ETS 300 qb2-3-ENGL Page 8 ETS 300 462-3: January 1997 3 Definitions, symbols and abbreviations 3.1 Definitions For the purposes of this ETS, the definitions given in ETS 300 462-1 l apply. 3.2 Symbols For the purposes of this ETS the symbols and diagrammatic conv
25、entions described in ETS 300 462-1 l apply. 3.3 Abbreviations MTIE PDH PSTN PRC SDH SEC ssu STM-N TDEV UTC Maximum Time Interval Error Plesiochronous Digital Hierarchy Public Switched Telephone Network Primary Reference Clock Synchronous Digital Hierarchy SDH Equipment Clock Synchronization Supply U
26、nit Synchronous Transport Module, level N Time DEViation Universal Time Co-ordinated 4 Basic philosophy for the control of jitter and wander The 300 462 series of ETSs describes the synchronization network as a logically distinct network layer with its own planning rules and performance requirements
27、. The philosophy for the control of jitter and wander in the synchronization network layer is the same as applied to the payload carrying layers of the transport network, which can be found in ITU-T Recommendation G.823 7. It is based on the need to recommend a maximum network limit that should not
28、be exceeded at any synchronization interface. This network limit represents the worst case accumulation of jitter and wander within the synchronization network reference chain shown in figure 5 of ETS 300 462-2 2. The main purpose for defining a network limit is that it provides the maximum amount o
29、f jitter and wander that any synchronization element in the network may experience at its input, since the network limit should not be exceeded at the output of a synchronization element anywhere in the network. The network limits therefore provide indirectly the requirements for the lower limit of
30、maximum tolerable jitter and wander at the input of synchronization elements. The wander tolerance of the large installed base of 64 kbit/s digital switches, .e. the differential wander that a switch will tolerate before giving rise to controlled slip, together with the slip performance objectives s
31、tated in ITU-T Recommendation G.822 6, have to be respected when introducing new transport technologies in the network. This differential wander is the cumulative effect of wander in the synchronization network and the wander that the transport of the data between switches may introduce. In the case
32、 of SDH, in most implementations, the latter is dependent on the wander that the SDH network elements experience at their synchronization inputs. The wander in a synchronization network that is also suitable for the synchronization of SDH therefore needs to be controlled to a level that is compatibl
33、e with the slip performance objectives of the 64 kbit/s switched network. It should be noted that the implication of the network limit definition is, that in practical networks the jitter and wander values at most synchronization interfaces should be well within the network limits, because the netwo
34、rk limits will only appear at the end of a synchronization chain that is as long as the reference chain. STD*ETSI ETS 300 Yb2-3-ENGL 1777 3Y00855 O15b251 TLb Page 9 ETS 300 462-3: January 1997 5 Synchronization interfaces The synchronization interfaces that are specified in this ETS are depicted in
35、figure 1. This figure is an expanded version of figure 6 of ETS 300 462-2 2 showing examples of actual physical interfaces that may appear in synchronization networks. Universal Time Co-ordinated (UTC) is indicated in the figure as the reference relative to which all network limits are specified. Be
36、cause of the way it is defined, there is no physical entity or interface associated with UTC. Two alternative synchronization distribution methods may be used between Synchronization Supply Unit (SSUs), and between Primary Reference Clock (PRC) and SSUs. SDH distribution makes use of the SDH section
37、 layer and may be a cascade of sections with at most 20 intermediate SDH network elements, each containing an SDH Equipment Clock (SEC). Plesiochronous Digital Hierarchy (PDH) distribution makes use of a 2 Mbit/s PDH path that may be traversing a number of intermediate PDH multiplexing stages and PD
38、H line systems. These are not shown explicitly, because they do not contain clocks that are subject to this ETS. .,. . . . . . .UTC . . . . . . . . . . . . . Note 1 I Note 1 I I Note 1 V I A SECS 0 Note 1 v Q Note 1: The maximum number of cloks in these chains is specified in ETS 300 462-2 2. - Sync
39、hronization interface at a PRC output for which the network limit applies. Synchronization interface at a SSU output for which the network limit applies. Synchronization interface at a SEC output for which the network limit applies. Synchronization interface at a PDH synchronization distribution out
40、put for which the network limit applies 0 _ Figure 1 : Synchronization reference chain showing where the network limits apply STD-ETSI ETS 300 Lib2-3-ENGL 3777 3400855 0356252 752 Page 10 ETC 300 462-3: January 1997 Figure 1 shows that four types of synchronization interfaces can be distinguished in
41、 the synchronization network: - - - - synchronization interfaces at PRC outputs; synchronization interfaces at SSU outputs; synchronization interfaces at SEC outputs; synchronization interfaces at PDH distribution outputs. This ETS therefore provides four sets of network limit requirements, one for
42、each type of interface. 6 Synchronization reference network The synchronization reference chain defined in figure 5 of ETS 300 462-2 2 has to support not only a homogeneous SDH transport network, to which the transport network will evolve sooner or later, but also the evolution towards an all SDH tr
43、ansport network. In the transitional period, a mixed situation will exist where data paths may traverse both PDH and SDH sub-networks. The additional PDH/SDH mappings give rise to an increase of the wander that the data path is experiencing because the wander that appears at the output of one SDH is
44、land is passed on transparently through subsequent islands via the asynchronous mapping process. It is therefore the transitional period which puts the most stringent requirements on the performance of the synchronization network. To provide for consistency between the specifications of the individu
45、al synchronization elements and the network limits an iterative process has been followed. The accumulation of wander in the synchronization reference network has been calculated based on a set of assumptions on: - - - the number and performance of individual synchronization elements; the number and
46、 size of transients in the synchronization network; the level of diurnal wander. The resulting quality of the synchronization network has then been applied to a reference model for the data path of four synchronous islands. Subsequently, the set of assumptions has been varied until a combination was
47、 found that met the requirement for the average differential wander experienced by a slip buffer terminated equipment (e.g. a 64 kbit/s exchange) of less than 18 ps measured over one day. The assumptions that were found to meet this requirement are documented in annex B. It is stressed however that
48、many other combinations of assumptions are conceivable that will comply with the network limits resulting from the set given in annex B. These are elaborated in this informative annex for guidance only. Provided these assumptions are fulfilled, the 18 ps wander limit will be met also across multiple
49、 operator domains. A network operator may use a different set of rules, e.g. with a different number of SSUs and other assumptions about the transients in the synchronization chain, provided the synchronization network limits for jitter and wander specified in this standard are adhered to. 7 Network limits for jitter and wander at synchronization interfaces The specification of network limits for synchronization interfaces is primarily intended to reflect the results of a theoretical analysis of the worst case
