1、ETSI EN 300 462-2-1 VI 2.1 (2002-06) European Sfandard (Telecommunicafions series) Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 2-1 : Synchronization network architecture based on SDH networks 2 ETSI EN 300 462-2-1 VI .2.1 (2002-06) Reference REN/TM-O10
2、92 Keywords architecture, SDH, synchronization, transmission ETSI 650 Route des Lucioles F-O6921 Sophia Antipolis Cedex - FRANCE Tel.: +33 4 92 94 42 O0 Fax: +33 4 93 65 47 16 Siret No 348 623 562 00017 - NAF 742 C Association but non lucratif enregistre la Sous-prfecture de Grasse (06) No 7803/88 I
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6、foregoing restriction extend to reproduction in all media. O European Telecommunications Standards Institute 2002. All rights reserved. DECTTM, PLUGTESTSTMand UMTSTMare Trade Marks of ETSI registered for the benefit of its Members. TIPHONTM and the TIPHON logo are Trade Marks currently being registe
7、red by ETSI for the benefit of its Members. 3GPPTM is a Trade Mark of ETSI registered for the benefit of its Members and of the 3GPP Organizational Partners. ETSI 3 ETSI EN 300 462-2-1 VI .2.1 (2002-06) Contents Intellectual Property Rights . .4 Foreword . 4 1 2 3 3.1 3.2 4 5 5.1 5.2 5.3 6 7 8 9 9.1
8、 9.2 10 10.1 10.2 10.3 10.4 Scope 6 References . .6 Definitions and abbreviations .7 Synchronization methods .7 Functional description of clock types .8 7 7 . . . . 8 8 9 Synchronization network architecture 1 O Primary Reference Clock (PRC) . Synchronization Supply Unit (SSU) . SDH Equipment Clock
9、(SEC) . . . . Synchronization modes 11 Synchronization network reference chain . .12 Synchronization network evolution. .14 Optical Transport Networks 14 Synchronization network robustness . .14 14 SDH networks . 14 14 15 15 General . . Trail redundancy . . Synchronization status message . . . Annex
10、 A (informative): Bibliography . 16 History 17 ETSI 4 ETSI EN 300 462-2-1 VI .2.1 (2002-06) Intellectual Property Rights IPRs essential or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available f
11、or ETSI members and non-members, and can be found in ETSI SR O00 3 14: “Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notijied to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (5)
12、. Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. No guarantee can be given as to the existence of other IPRs not referenced in SR O00 3 14 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present d
13、ocument. Foreword This European Standard (Telecommunications series) has been produced by ETSI Technical Committee Transmission and Multiplexing (TM). The present document has been produced to provide requirements for synchronization networks that are compatible with the performance requirements of
14、digital networks. It is one of a family of documents covering various aspects of synchronization networks. The present document is part 2-1 of a multi-part deliverable covering generic requirements for synchronization networks, as identified below: Part 1-1: Part 2-1: Part 3-1: Part 4-1 : Part 4-2:
15、Part 5-1: Part 6-1 : Part 6-2: Part 7-1 : “Definitions and terminology for synchronization networks“; “Synchronization network architecture based on SDH networks“; “The control of jitter and wander within synchronization networks“; “Timing characteristics of slave clocks suitable for synchronization
16、 supply to Synchronous Digital Hierarchy (SDH) and Plesiochronous Digital Hierarchy (PDH) equipment“; “Timing characteristics of slave clocks suitable for synchronization supply to Synchronous Digital Hierarchy (SDH) and Plesiochronous Digital Hierarchy (PDH) equipment; Implementation Conformance St
17、atement (ICs) proforma specification“; “Timing characteristics of slave clocks suitable for operation in Synchronous Digital Hierarchy (SDH) equipment “ ; “Timing characteristics of primary reference clocks“; “Timing characteristics of primary reference clocks; Implementation Conformance Statement (
18、ICs) proforma specification“; “Timing characteristics of slave clocks suitable for synchronization supply to equipment in local node applications“. Part 2-1 has been revised in several sections with regard to the work done in EG 201 793 7 and to reflect the present status of synchronization networks
19、. ETSI 5 ETSI EN 300 462-2-1 VI .2.1 (2002-06) National transposition dates Date of adoption of this EN: Date of latest announcement of this EN (doa): Date of latest publication of new National Standard or endorsement of this EN (dop/e): Date of withdrawal of any conflicting National Standard (dow):
20、 3 1 May 2002 3 1 August 2002 28 February 2003 28 February 2003 ETSI 6 ETSI EN 300 462-2-1 VI .2.1 (2002-06) 1 Scope The present document specifies the architectural principles that should be applied for the design of synchronization networks that are suitable for the synchronization of Synchronous
21、Digital Hierarchy (SDH) and Plesiochronous Digital Hierarchy (PDH) networks. It supports the construction of synchronization networks that support both the short-term stability requirements of SDH networks and the long-term stability requirements of digital switching networks (e.g. PSTN) connected t
22、o the SDH network. It applies to the design of new synchronization networks. It does not characterize existing synchronization networks based on PDH networks. The present document specifies the rules and architectural principles the implementation of synchronization networks shall follow. This infor
23、mation is supplemented by EG 201 793 7. It gives guidance and examples how these rules and architectural principles can be used to set up a synchronization scheme for various network configurations. 2 Refe re nces The following documents contain provisions which, through reference in this text, cons
24、titute provisions of the present document. References are either specific (identified by date of publication andor edition number or version number) or non-specific. For a specific reference, subsequent revisions do not apply. For a non-specific reference, the latest version applies. il ETSI EN 300
25、462-1-1 : “Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 1 - 1 : Definitions and terminology for synchronization networks“ ETSI EN 300 462-3-1 : “Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 3-1 : The contro
26、l of jitter and wander within synchronization networks“. 21 31 ETSI EN 300 147: “Transmission and Multiplexing (TM); Synchronous Digital Hierarchy (SDH); Multiplexing structure“. ETSI EN 300 462-5-1 : “Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 5-1 :
27、Timing characteristics of slave clocks suitable for operation in Synchronous Digital Hierarchy (SDH) equipment“. ETSI EN 300 462-6-1 : “Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 6- 1 : Timing characteristics of primary reference clocks“. ETSI EN 300
28、462-4-1 : “Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 4-1 : Timing characteristics of slave clocks suitable for synchronization supply to Synchronous Digital Hierarchy (SDH) and Plesiochronous Digital Hierarchy (PDH) equipment“. ETSI EG 20 1 793 : “Tr
29、ansmission and Multiplexing (TM); Synchronization network engineering“ ETSI EN 300 462-7-1 : “Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 7-1 : Timing characteristics of slave clocks suitable for synchronization supply to equipment in local node applic
30、ations“. ETSI EN 300 417-6-1 : “Transmission and Multiplexing (TM); Generic requirements of transport functionality of equipment; Part 6- 1 : Synchronization layer functions“. 41 51 61 71 SI 91 ETSI 7 ETSI EN 300 462-2-1 VI .2.1 (2002-06) 3 Definitions and abbreviations 3.1 De fin it ions For the pu
31、rposes of the present document, the terms and definitions given in EN 300 462-1-1 i apply. 3.2 Abbreviations For the purposes of the present document, the abbreviations defined in EN 300 462-1-1 i and the following apply: ADM AIS NE OTN PDH PPm PRC PSTN SASE SDH SEC SETG SETS s su S SM STM-N Add Dro
32、p Multiplexer Alarm Indication Signal Network Element Optical Transport Network Plesiochronous Digital Hierarchy parts per million Primary Reference Clock Public Switched Telephone Network Stand-Alone Synchronization Equipment Synchronous Digital Hierarchy SDH Equipment Clock SDH Equipment Timing Ge
33、nerator SDH Equipment Timing Source Synchronization Supply Unit Synchronization Status Message Synchronous Transport Module N 4 Synchronization methods Master-slave synchronization is appropriate for synchronizing SDH networks and the following material offers guidance on using this method. Master-s
34、lave synchronization uses a hierarchy of clocks in which each level of the hierarchy is synchronized with reference to a higher level. There are four qualities of clock in the synchronization hierarchy shown below: - Primary Reference Clock (PRC): see EN 300 462-6-1 5; - slave clock (transit node):
35、see EN 300 462-4-1 6; - slave clock (local node): see EN 300 462-7-1 SI; - SDH Equipment Clock (SEC): see EN 300 462-5-1 4. The PRC is the highest quality hierarchical clock and the SEC is the lowest quality clock. Higher quality clocks shall not be synchronized by lower quality clocks in holdover m
36、ode, but clocks in holdover mode can be used to synchronize clocks of the same quality. There are limits on the number of clocks, which can be connected in a synchronization distribution trail (see clause 8). Clock reference signals are distributed between levels of the hierarchy via a distribution
37、network, which may use the facilities of the transport network. The transport network may contain SECS. The distribution of timing between hierarchical node clocks shall be performed using a method, which avoids intermediate pointer processing. Two possible methods are as follows: a) recover timing
38、from a received Synchronous Transport Module N (STM-N) signal (this avoids the unpredictable effect of a pointer adjustment on the downstream slave clock); b) derive timing from a synchronization trail that is not supported by a SDH network. The master-slave method uses a single-ended synchronizatio
39、n technique with the slave clock selecting the synchronization trail to be used as its reference and changing to an alternative if the original trail fails. This is a unilateral control scheme. ETSI 8 ETSI EN 300 462-2-1 VI .2.1 (2002-06) 5 Functional description of clock types 5.1 Primary Reference
40、 Clock (PRC) The PRC is a logical function conforming to the requirements of EN 300 462-6-1 5. It generates the master clock for a network or part of a network. The PRC equipment may either: - - implement its own free running oscillator (e.g. Caesium tube oscillator); or be a slave clock being synch
41、ronized to a high accuracy free running clock by terrestrial or satellite radio signals (e.g. GPS). 5.2 Synchronization Supply Unit (SSU) A SSU is a logical function conforming to the requirements of EN 300 462-4-1 6 or EN 300 462-7-1 SI. It: - - - - accepts synchronization inputs from a number of s
42、ources; selects one of these inputs; filters this sources clock removing jitter and short-term wander; distributes the resultant clock to other elements within a node. In the event of failure or degradation of all synchronization reference inputs, the SSU will use a high quality internal oscillator
43、to maintain the stability and accuracy of the frequency of its output signals (holdover mode). A functional diagram of the SSU is shown in figure 1. The physical implementation of this function may be integrated within a SDH network element, integrated within Public Switched Telephone Network (PSTN)
44、 switch, or as a stand-alone unit (a Stand-Alone Synchronization Equipment, (SASE). TI T2 T4 -b TO -b Key: TO: Internal system clock. TI : T2 : T3: T4 : TG: Timing Generator. NOTE 1: Where the SSU is integrated within a SDH Network Element (NE), TO should be provided. NOTE 2: It may be possible to f
45、orce the SSU into a free-running condition. Timing reference signal derived from STM-N input. Timing reference signal derived from 2 048 kbitk input. Timing reference signal derived from 2 048 kHz or 2 048 kbis with SSM External reference timing signal (2 048 kHz or 2 048 kbis with SSM). Figure 1: T
46、he SSU clock function ETSI 9 ETSI EN 300 462-2-1 VI .2.1 (2002-06) 5.3 SDH Equipment Clock (SEC) The SEC is a logical function of input signal selection and clock filtering. The selection function conforms to the requirements of EN 300 417-6-1 5 and the filtering function conforms to the requirement
47、s of EN 300 462-5-1 4. The SEC: - - - filters this sources clock. accepts synchronization inputs from a number of sources within that element; selects one of these inputs; In the event of failure of all synchronization reference inputs the SEC shall use its own internal clock as the active clock sou
48、rce (holdover mode). The SEC is specified to be used in SDH equipment as the timing source for the outgoing SDH STM-N interfaces of the NE. A functional diagram of the SEC is shown in figure 2. Key: TO: TI : T2 : T3: T4 : SETG: NOTE 1: NOTE 2: . p cz q k k,. k + . I $ r - - - - - - 4 Select I- - I I
49、 I I Select I r-* s : I I. I s : I Internal system clock. Timing reference signal derived from STM-N input. Timing reference signal derived from 2 048 kbitk input. Timing reference signal derived from 2 048 kHz or 2 048 kbis with SSM External reference timing signal (2 048 kHz or 2 048 kbis with SSM). SDH Equipment Timing Generator. The SEC is a functional subset of the SETS as described in EG 201 793 7. It may be possible to force the SEC into a free running condition. T4 + Figure 2: The SEC clock function ETSI 10 ETSI EN 300 462-2-1
