ETSI EN 300 462-2-1 V1.1.1 (1998-05)

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.Transmission and Multiplexing (TM); Generic requirements for synchronization networks; Part 2-1: Synchronization network architecture33.040.20Prenosni sistemTransmission systemsICS:Ta slovenski standard je istoveten z:EN 300 462-2-1 Version 1.1.1SIST EN 300 462-2-1 V1.1.1:2003en01-december-2003SIST EN 300 462-2-1 V1.1.1:2003SLOVENSKI
STANDARD



SIST EN 300 462-2-1 V1.1.1:2003



EN 300 462-2-1 V1.1.1 (1998-05)European Standard (Telecommunications series)Transmission and Multiplexing (TM);Generic requirements for synchronization networks;Part 2-1: Synchronization network architectureSIST EN 300 462-2-1 V1.1.1:2003



ETSIEN 300 462-2-1 V1.1.1 (1998-05)2ReferenceREN/TM-03017-2-1 (4a0i9ico.PDF)Keywordssynchronization, timing, transmissionETSIPostal addressF-06921 Sophia Antipolis Cedex - FRANCEOffice address650 Route des Lucioles - Sophia AntipolisValbonne - FRANCETel.: +33 4 92 94 42 00
Fax: +33 4 93 65 47 16Siret N° 348 623 562 00017 - NAF 742 CAssociation à but non lucratif enregistrée à laSous-Préfecture de Grasse (06) N° 7803/88Internetsecretariat@etsi.frhttp://www.etsi.frhttp://www.etsi.orgCopyright NotificationNo part may be reproduced except as authorized by written permission.The copyright and the foregoing restriction extend to reproduction in all media.© European Telecommunications Standards Institute 1998.All rights reserved.SIST EN 300 462-2-1 V1.1.1:2003



ETSIEN 300 462-2-1 V1.1.1 (1998-05)3ContentsIntellectual Property Rights.4Foreword.41Scope.62References.63Definitions and abbreviations.63.1Definitions.63.2Abbreviations.74Synchronization methods.74.1Master-slave synchronization.74.2Mutual synchronization.85Functional description of clock types.85.1Primary Reference Clock (PRC).85.2Synchronization Supply Unit (SSU).85.3SDH Equipment Clock (SEC).96Synchronization network architecture.107Synchronization modes.128Synchronization network reference chain.129Synchronization strategy.1410Synchronization network evolution.1411Synchronization network robustness.14History.16SIST EN 300 462-2-1 V1.1.1:2003



ETSIEN 300 462-2-1 V1.1.1 (1998-05)4Intellectual Property RightsIPRs essential or potentially essential to the present document may have been declared to ETSI. The informationpertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be foundin ETR 314: "Intellectual Property Rights (IPRs); Essential, or potentially Essential, IPRs notified to ETSI in respect ofETSI standards", which is available free of charge from the ETSI Secretariat. Latest updates are available on the ETSIWeb server (http://www.etsi.fr/ipr or http://www.etsi.org/ipr).Pursuant to the ETSI Interim IPR Policy, no investigation, including IPR searches, has been carried out by ETSI. Noguarantee can be given as to the existence of other IPRs not referenced in ETR 314 (or the updates on the ETSI Webserver) which are, or may be, or may become, essential to the present document.ForewordThis European Standard (Telecommunications series) has been produced by the Transmission and Multiplexing (TM)Technical Committee.The present document has been produced to provide requirements for synchronization networks that are compatible withthe performance requirements of digital networks. It is one of a family of documents covering various aspects ofsynchronization networks:Part 1-1:"Definitions and terminology for synchronization networks";Part 2-1:"Synchronization network architecture";Part 3-1:"The control of jitter and wander within synchronization networks";Part 4-1:"Timing characteristics of slave clocks suitable for synchronization supply to Synchronous DigitalHierarchy (SDH) and Plesiochronous Digital Hierarchy (PDH) equipment";Part 4-2:"Timing characteristics of slave clocks suitable for synchronization supply to Synchronous DigitalHierarchy (SDH) and Plesiochronous Digital Hierarchy (PDH) equipment ImplementationConformance (ICS) Statement";Part 5-1:"Timing characteristics of slave clocks suitable for operation in Synchronous Digital Hierarchy(SDH) equipment";Part 6-1:"Timing characteristics of primary reference clocks";Part 6-2:"Timing characteristics of primary reference clocks Implementation Conformance (ICS)Statement";Part 7-1:"Timing characteristics of slave clocks suitable for synchronization supply to equipment in localnode applications".Parts 1-1, 2-1, 3-1 and 5-1 have previously been published as ETS 300 462 Parts 1, 2, 3 and 5, respectively.Additionally, parts 4-1 and 6-1 completed the Voting phase of the Two Step Approval procedure as ETS 300 462 Parts4 and 6, respectively.It was decided to prepare ICS proformas for several of the parts and this necessitated a re-numbering of the individualdocument parts. It was also decided to create a new part 7-1.This in turn led to a need to re-publish new versions of all six parts of the original ETS. At the same time, theopportunity was taken to convert the document type to EN.This has involved no technical change to any of the documents. However part 5-1 has been modified, due to editorialerrors which appeared in ETS 300 462-5.SIST EN 300 462-2-1 V1.1.1:2003



ETSIEN 300 462-2-1 V1.1.1 (1998-05)5Transposition datesDate of adoption of this ETS:16 August 1996Date of latest announcement of this ETS (doa):31 December 1996Date of latest publication of new National Standardor endorsement of this ETS (dop/e):30 June 1997Date of withdrawal of any conflicting National Standard (dow):30 June 1997NOTE:The above transposition table is the original table from ETS 300 462-2 (September 1996, see History).SIST EN 300 462-2-1 V1.1.1:2003



ETSIEN 300 462-2-1 V1.1.1 (1998-05)61ScopeThis European Standard (Telecommunications series) specifies the architectural principles that should be applied for thedesign of synchronization networks that are suitable for the synchronization of Synchronous Digital Hierarchy (SDH)and Plesiochronous Digital Hierarchy (PDH) networks. It supports the construction of synchronization networks thatsupport both the short term stability requirements of SDH networks and the long term stability requirements of PDHnetworks. It applies to the design of new synchronization networks. It does not characterize existing PDHsynchronization networks.2ReferencesThe following documents contain provisions which, through reference in this text, constitute provisions of the presentdocument.· References are either specific (identified by date of publication, edition number, version number, etc.) ornon-specific.· For a specific reference, subsequent revisions do not apply.· For a non-specific reference, subsequent revisions do apply.· A non-specific reference to an ETS shall also be taken to refer to later versions published as an EN with the samenumber.[1]EN 300 462-1-1: "Transmission and Multiplexing (TM); Generic requirements for synchronizationnetworks; Part 1-1: Definitions and terminology for synchronization networks".[2]EN 300 462-3-1: "Transmission and Multiplexing (TM); Generic requirements for synchronizationnetworks; Part 3-1: The control of jitter and wander within synchronization networks".[3]ETS 300 147 (1995): "Transmission and Multiplexing (TM); Synchronous Digital Hierarchy(SDH) Multiplexing structure".[4]EN 300 462-5-1: "Transmission and Multiplexing (TM); Generic requirements for synchronizationnetworks; Part 5-1: Timing characteristics of slave clocks suitable for operation in SynchronousDigital Hierarchy (SDH) equipment".[5]EN 300 462-6-1: "Transmission and Multiplexing (TM); Generic requirements for synchronizationnetworks; Part 6-1: Timing characteristics of primary reference clocks".[6]ITU-T Recommendation G.783 (1994): "Characteristics of synchronous digital hierarchy (SDH)equipment functional blocks".[7]EN 300 462-4-1: "Transmission and Multiplexing (TM); Generic requirements for synchronizationnetworks; Part 4-1: Timing characteristics of slave clocks suitable for synchronization supply toSynchronous Digital Hierarchy (SDH) and Plesiochronous Digital Hierarchy (PDH) equipment".3Definitions and abbreviations3.1DefinitionsFor the purposes of the present document, the definitions given in EN 300 462-1-1 [1] apply:SIST EN 300 462-2-1 V1.1.1:2003



ETSIEN 300 462-2-1 V1.1.1 (1998-05)73.2AbbreviationsFor the purposes of the present document, the abbreviations given in EN 300 462-1-1 [1], together with the following,apply:AISAlarm Indication SignalNENetwork ElementPDHPlesiochronous Digital Hierarchyppmparts per millionPRCPrimary Reference ClockPSTNPublic Switched Telephone NetworkSASEStand-Alone Synchronization EquipmentSDHSynchronous Digital HierarchySECSDH Equipment ClockSETSSDH Equipment Timing SourceSSUSynchronization Supply UnitSTM-NSynchronous Transport Module NTUTributary Unit4Synchronization methodsThere are two fundamental methods of synchronizing nodal clocks. These are identified in EN 300 462-1-1 [1]:-master-slave synchronization;-mutual synchronization.4.1Master-slave synchronizationMaster-slave synchronization is appropriate for synchronizing SDH networks and the following material offers guidanceon using this method.Master-slave synchronization uses a hierarchy of clocks in which each level of the hierarchy is synchronized withreference 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):see EN 300 462-4-1 [7];-slave clock (local node):see EN 300 462-4-1 [7];-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 must notbe synchronised by lower quality clocks in holdover mode, but clocks in holdover mode can be used to synchroniseclocks of the same quality. There are limits on the number of clocks which can be connected in a synchronizationdistribution trail (see clause 8). Clock reference signals are distributed between levels of the hierarchy via a distributionnetwork which may use the facilities of the transport network. The transport network may contain SECs. Thedistribution of timing between hierarchical node clocks shall be performed using a method which avoids intermediatepointer processing. Two possible methods are as follows:a)recover timing from a received Synchronous Transport Module N (STM-N) signal (this avoids the unpredictableeffect 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 synchronization technique with the slave clock determining thesynchronization trail to be used as its reference and changing to an alternative if the original trail fails. This is aunilateral control scheme.SIST EN 300 462-2-1 V1.1.1:2003



ETSIEN 300 462-2-1 V1.1.1 (1998-05)84.2Mutual synchronizationThe feasibility of employing mutual synchronization is left for further study. The remainder of the present documentrefers only to the hierarchical master-slave approach.5Functional description of clock types5.1Primary Reference Clock (PRC)A PRC is a stand-alone clock and a logical function which:-is either an autonomous clock; or-it accepts synchronization from a radio or satellite signal and performs filtering.The PRC shall conform to EN 300 462-5-1 [4].5.2Synchronization Supply Unit (SSU)A SSU is a logical function which:-accepts synchronization inputs from a number of sources;-selects one of these inputs;-filters this source's clock; and-distributes the resultant clock to other elements within a node.A functional diagram of the SSU is shown in figure 1.In the event of failure or degradation of all synchronization reference inputs,
the SSU will use an internal timi
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