AT&T 7500 series, 7100 series, 2500 series, 7200 series, 7400 series

B-26SYNCHRONIZATION OF DIGITAL FACILITIES

____________________________________________________________________________________________________________________________

_

RULE 7:

The number of nodes receiving synchronization reference from any given node should be minimized.

EXAMPLE FOR RULE 7

Figure B-19,Excessive Synchronization from One Node , shows an excess of synchronization from one node. If transmission facility linking nodes A-B fails, then nodes B, D, E, and F will lose their synchronization. However, if this same facility fails in ﬁgure B-20,Minimized Synchronization from One Node , only nodes B, D, and E will lose synchronization. Node F remains synchronized to the network.

With few exceptions, it is not possible to engineer a synchronization network that will satisfy all seven rules. In general, rules 1 through 3 apply in all cases. For rules 4 through 7, use those rules that apply to your speciﬁc network and try to minimize outages based on the cases presented in the examples for each of these rules.

	A
B		C
D	E	F
	. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
	DIGITAL TRANSMISSION FACILITY
	PRIMARY FREQUENCY REFERENCE
. . . . . . . . . . . . . .	SECONDARY (BACKUP) FREQUENCY REFERENCE

Figure B-19.Excessive Synchronization from One Node

Image 234

AT&T 7500 series, 7100 series, 2500 series, 7200 series, 7400 series manual Figure B-19.Excessive Synchronization from One Node

Contents

Definity Communications System Page Contents Multiplexing Outside the Switch Communication System Networking AN Overview Tandem TIE Trunk Networks Distributed Communications System DCS Data Connectivity AN Overview Special Data Features Data Communications Capabilities Data Communications Configurations Related Documents Synchronization of Digital Facilities Trunking Terms and Capabilities Communications Protocols GlossaryIndex List of Figures DSU Mpdm Figure B-1 Options for Synchronization Figure B-11 External and Internal Reference Levels List of Tables BCC EIA RS-449 V.24 LEADS/DEFINITIONS EIA RS-232C V.28 LEADS/DEFINITIONSEIA RS-232D V.28 LEADS/DEFINITIONS EIA RS-366 LEADS/DEFINITIONS Xvi Contents About this Document Prerequisite Skills and KnowledgeDocument Organization Part ∙ Glossary ∙ Index HOW to Make Comments about this Document AT&T Xx about this Document Introduction to Connectivity 2INTRODUCTION to Connectivity Transmission Types Analog TransmissionDigital Transmission Analog-to-Digital Conversion Analog VS. Digital 6TRANSMISSION Types Entering the Switch Transmission StatesVoice Transmission 8TRANSMISSION States Digital Switch Exiting the Switch ⎜ Module Circuit Packs Data Transmission Protocol Layers 12TRANSMISSION States Originating Switch Destination Protocols Used Layer 1 Protocols Layer 2 Protocols Protocol States ⎜DMI Mode Code Connectivity Rules 16TRANSMISSION States Frequency-Division Multiplexing Multiplexed CommunicationTypes of Multiplexing Time-Division Multiplexing Statistical Multiplexing Multiplexing Over DS1 Facilities Line Coding Alternating Mark InversionZero Code Suppression ZCS Line Coding B8ZS Line Coding Signal Inversion Restricted ⎜ Unrestricted ⎜ DMI 7Data-Module Capabilities Part 2 D4 Framing Framing Signaling D4 FramingESF Framing Robbed-Bit Signaling ESF 24th-Channel Signaling⎜ Channels 24th Channel ⎜ 24th Channel ⎜ Frame No Trunk Types/Destinations ⎜ Signaling Types ⎜ DMI-BOS⎜ Isdn PRI Multiplexing Outside the Switch Multiplexing onto T1 Trunks CDM CEM Host Digital DMI PBX Compressing the Signal Getting the Signal Ready for the Central OfﬁceAltering Channel Assignments on T1 Trunks DR23N DR18M DR18W DR23W Multiplexing with MicrowaveMicrowave System T1 Trunk Capacity Demultiplexing 10.Possible Multiplexed Connections Statistical Multiplexing Trunking ApplicationLocal Exchange Trunks Tie Trunks Miscellaneous Trunks Special-Access TrunksAuxiliary Trunks Release Link Trunks RLTs Advanced Private Line Termination Aplt Trunks Remote Access TrunksHost-Access Trunks Connectivity Administration Options System 85/G2 AdministrationSignaling Types Signaling Protocols Trunk Type Group Type System 75/G1 AdministrationComm Type DS1 Options Interface Circuit Trunk Tables Trunking 44TRUNKING 11.Generic 1 and Generic 2 Digital Trunks Voice BCC 46TRUNKING Trunking 48TRUNKING Trunking 50TRUNKING Trunking 52TRUNKING Communication System Networking AN Overview Types of Networks Network Evolution DCS Software ⎜ Network Type S75/G1 S85/G2 PackagePEC Software Capabilities System 75 and Generic 1 UDP Package DIMENSION, System 85, and Generic 2 Multipremises Package System 75 and Generic 1 PNA Package Distributed Communications System Network Call Processing Internal Dial Plan Uniform NumberingRouting the Call DAC + EXT To ARS Auxiliary Call Information Automatic Alternate Routing Selecting a Routing Pattern ∙ RNX ∙ The FRL of the call ∙ Where the trunk group appears in the list of preferencesSelecting a Trunk Group Modifying the Digits Automatic Route Selection Analyzing the Dialed Number Communication System Networking AN Overview To AAR Selecting the Routing Pattern Network Administration Networking Feature ParametersPrivate Network Trunks ⎜ Maap ⎜ Vmaap System Definity Feature PBX 20COMMUNICATION System Networking AN Overview Tandem TIE Trunk Networks Interactions with Other Networks 2TANDEM TIE Trunk Networks Attendant Lines ⎜ Main Satellite ⎜ Trunks MS/T Configurations Main-Satellite Conﬁguration Main-Tributary Conﬁguration MS/T Features Networking Package Multipremises with ETA Main Networking Package PNA, ETN Routing Incoming Calls Routing Outgoing Calls Other Routing Capabilities Engineering Considerations Interactions Page ETN Configurations ETN Trunks Page Access and Bypass Access Tie Trunks Features Off-Net TrunksUniform Numbering Plan Attendant ETN Interactions with Other Networks Extension Number Portability Clusters Software-Deﬁned Network Call Routing SDN to ETN Call Routing ETN to SDN Release Link Trunk Networks CAS and ACD Centralized Attendant Service Automatic Call Distribution Distributed Communications System Clusters Main-Satellite/Tributary Networks Distributed Communications System DCS Switch Node Capacity DCS ClustersDCS Links Signaling Link Speed Signaling LinksSwitch Physical Links ⎜Logical Channels/Link Signaling Link Protocol Transmission Media Direct Link DCS Connections Linkage Design Distributed Communications System DCS MTDM/MPDM DCS Signaling Link ConnectionsEquipment Distance Limitation System 75 or Generic 1 G1 to System 75 or G1 System 75/G1 Signaling Channel DCP Mtdm System 85 or Generic 2 G2 to System 85 or G2 Modem System 75 or Generic 1 G1 to System 85 or Generic 2 G2 RS232C to RS449 Conversion Dciu Transparent Attendant Features Dimension Signaling LinksTransparent Features Attendant Call Waiting Alphanumeric Display Attendant Control of Trunk Group Access⎜ ACA Automatic Circuit Assurance Busy Veriﬁcation of Terminal Lines Class-of-Service/Restriction DisplayTrunk Group Busy/Warning Indicators Calling Number Display Transparent Voice Terminal Features Alerting-Distinctive RingingAutomatic Callback on Busy or No Answer Call Waiting Call Coverage ToneCall Forwarding Leave Word Calling LWC Without AP Audio Information Exchange Audix Features Transparency Call Transfer/Conference 20.AUDIX in a DCS Network Definity PBX ⎜ Feature 22DISTRIBUTED Communications System DCS Administration Considerations Distributed Communications System, Issue 3 Dimension PBX Data Connectivity AN Overview Data Communications Variables Communications Protocols Digital PBX Public Switched Network Pooled Modem Analog vs. Digital Synchronous vs. Asynchronous ∙ ∙ ∙ Simplex vs. Half-Duplex vs. Full-Duplex Parallel vs. Serial Transmission Speed Creating Switch Packet vs. Circuit Switches Type of Communications Channel Channel Information Bearer vs. Signaling Channels Transmission Mode Changes and Modem PoolsChannel Assignment Dial-up vs. Dedicated Connections Special Data Features Terminal Dialing Computer Dialing ⎜Data Services FeaturesData Call Setup From a Voice Terminal Data Hot Line Data Restriction Data ProtectionData Privacy Data Only Off-Premises Extension Off-Premises Data-Only Extension Conﬁgurations Data Communications Capabilities 2DATA Communications Capabilities DTE Connections DTE CompatibilityProtocol Converters Terminal Emulators PC/PBX or PC/ISDN DCE Possibilities Data ModulesVoice Terminal Adjunct Data Modules ADUs Data Module CharacteristicsStandalone Data Modules Modems DTE Connections Dtdm ADM ⎜ PC/PBXPC/PBX PC/ISDN Modem Pooling Connections DCP TIP-RING 12DTE Connections Data Module Local Area Network Connections LAN TopologyLAN Protocol LAN Connectors LAN Transmission MediaAdvantages of a Communications System in a LAN Environment LAN LAN Access to/from LANs That Use Other Operating SystemsType Operating Gateway PC System Software Local Area Network Connections Remote PC ISN Communication Communication Between the LAN and Other NetworksX.25 Router Type Operating Communications System PackageSNA Gateway Communication System as a LAN Backup 12.LAN/SNA Connectivity Public and Private Data Network Connections Accunet Packet ServiceAPS Access Public Data Networks Circuit-Switched Public Data Networks SDS and Sddn Applications Public and Private Data Network Connections MPDM/M1 Public and Private Data Network Connections DTE Mpdm Private Data Networks Terrestrial Private Data Network LinksPrivate Connections Through Accunet T1.5 and T45 MPDM/M1* AMI 28PUBLIC and Private Data Network Connections ⎜AMI Satellite Private Data Network Links Telemarketing Host Connections Isdn GatewayIntegrated Telemarketing Gateway 22.Telemarketing Gateway Conﬁguration For further details, see 34TELEMARKETING Host Connections Data Network Administration 36DATA Network Administration Data Communications Configurations DSC and PSC Connections DSC 4DATA Communications Configurations SNA Node Connections Connections Through Public or Private Data Networks File TransfersVideo Teleconferencing Image Processing FAX Transmittal 8DATA Communications Configurations Operation Related DocumentsGeneral Reference 2RELATED Documents Related Documents Dimension Administration System 75 and Generic 6RELATED Documents Service SalesSystem 85 and Generic 8RELATED Documents Sales 10RELATED Documents Synchronization of Digital Facilities Need for Synchronization Figure B-1.Options for Synchronization Synchronization Hierarchy 4SYNCHRONIZATION of Digital Facilities Synchronization of Digital Facilities ∙ DDS Figure B-3.Stratum Levels for the Synchronization Hierarchy System 85 and Generic 2 Synchronization ArchitecturePage Primary RED YEL Good LOS Misf Primary Secondary Reference Indicators ⎜ Reference⎜ Indicators ⎜ Blue RED System 75 and Generic 1 Synchronization Architecture Figure B-6.Tone-Clock Synchronizer Nonduplicated, Generic System 75 and Generic 1 Synchronization Software Operation Criteria for Switching to the Secondary Reference Criteria for Switching Back to the Primary Reference External Synchronization Clock CROSS-CONNECT B25A Cable Output Figure B-9.External-Clock Interface Selecting a Timing Source for the Switch Network Synchronization and Engineering Internal Reference Selection Rules Rule Example for Rule Figure B-13.Proper Use of Backup Facilities Page Figure B-15.Optimal Diverse Routing Figure B-16.Less Than Optimal Diverse Routing Figure B-17.Excessive Cascading Figure B-19.Excessive Synchronization from One Node External-Reference Selection Rules Rules 2 Through Availability of Synchronization Sources MisconceptionFact USE of Generic 2 AS a System Clock Reference Line-Only Mode DS1/DMI-BOS ANN11 or TN767Conclusions on Synchronization ISDN-PRI Trunk Facilities USE of Generic 1 AS a System Clock Reference Line+Trunk Mode DS1/DMI-BOS ANN35 or TN767 with TN555DMI-MOS ANN35 or TN767 with TN555 Trunk-Mode ISDN-PRI TN767 Line-Only Mode DS1/DMI-BOS TN767 Trunk-Mode Interface ISDN-PRI + Robbed Bit TN767Trunk-Mode DS1/DMI-MOS TN767 32SYNCHRONIZATION of Digital Facilities Trunking Terms and Capabilities Wire Tie TrunkAddress Signaling Frequently Used Terms Auto or Automatic-incoming Alerting SignalsAPLT-Advanced Private Line Termination Auto or Automatic-outgoing Customer Provided Access Ccsa or Common Control Switching ArrangementCX Signaling or Composite Signaling Cut-Through Mode of Operation Delay-Dial Outgoing Delay-DialDelay-Dial Incoming Delay-Dial Start-Dial Ddsd Dial Repeating Tie Trunk Derived E&M Lead SignalingDesigned Trunks Dial-Pulse Lead Signaling or Ear & Mouth Signaling Direct AccessEpscs or Enhanced Private Switched Communications Service Standard or Type 1A and Type I compatible or Type 1B ETN Trunking Facilities FX or Foreign Exchange Glare Resolution GlareGlare Detection Immediate Start Ground StartHigh-Usage Trunk Group Immediate Start Incoming Intermachine Trunk IMT Interdigit Time-outIntermediate High-Usage Trunk Group Intertandem Trunk Main PBX Out-of-Band SignalingParty Test Signal Main-Satellite Trunks Senderized Mode of Operation Reverse BatterySF or Single Frequency signaling Signal Converter Stop-Go Signaling Signaling TypeSpecial Access Connections Supervisory Signaling Type of Dialing Touch-Tone SignalingTrunk Type or trunk group type Type of Outpulsing Wats Wide Area Telephone Service Trunk Wink-Start IncomingWink-Start Outgoing Suggestions and Helpful Hints Trunking Characteristics Table Signaling Types System 85, or Dimension PBX Switch aSupervision Signaling Tion Generic ⎜GROUP/CALL Type Switch B GROUP/CALL Type DOD 23/FX-DOD OUTIN/DID GROUP/CALL Type Signaling 26/WATS 27/WATS OUT28/WATS-DOD OUT ⎜⎜ E&M 35/TIE ESS 5ESS ⎜OTHER ⎜ LS ⎜ RB ⎜ System 85, or ⎜DIMENSION PBX ⎜ ⎜57/CAS RLT-OUTGOING From Branch ⎜66/CAS RLT-INCOMING Main Satellite ⎜DIAL-TONE with Analog Data Modem Side Digital Data ⎜DATA Module Side 103/HOST AccessLine Side 104/HOST Access Trunk Side Other 32TRUNKING Terms and Capabilities Communications Protocols Data-Link Layer OSI ModelPhysical Layer Network LayerPage Figure D-1.OSI Reference Model Application Layer Session LayerPresentation Layer Standard Protocols Table D-1.Some Ccitt Digital Standards Table D-2.Some Ccitt Analog Standards Ccitt X.26 RS-423A FED-STD Table D-2.Some Ccitt Analog Standards Other Common Standards CCITT-ISO AT&T Protocols EIA Data Mode Capabilities Digital Multiplexed InterfaceData Modes Applications Description Control Data DCP DS1/DMI/BOS Channel 14COMMUNICATIONS Protocols Communications Protocols Flag Digital Communications Protocol Or multipoint BX.25 Communication Pathways and Endpoints Message, Packet, and Frame Sldh Lead Definitions SBA SCFSCB SBB RL/CG CH/CI RDA SDASTA RSA CRQ DPRACR PND DDA BBABBB DDB ⎜ PIN 8LEAD Definitions Networking FEATURES--AVAILABILITY Matrix ⎜⎜ R1 Networking FEATURES--AVAILABILITY Matrix Contd ⎜ NA ⎜ Uniform Numbering ⎜ Plan Note 6NETWORKING FEATURES--AVAILABILITY Matrix Abbreviations CSU CRCCSM DAC FAX ETAETN FEP Mtdm MpdmMS/T NCP SNA SDNSMT Teho AB-6ABBREVIATIONS ADM GlossaryACU AVD ADS Automatic Alternate Also high-volume tandemAudix Standalone Routing AAR Bit-oriented signaling Service BccosBipolar signal Message-oriented signaling BSC CcittCPU COS CcisCOR CPE See network channel-terminating equipment See data communications equipment DCS cluster DCS node Dciu linkDCP DCS See bit rate DDC DDD See digital telephone DMI/MOS DCS DMI-BOSDMI-MOS DS1 Communications systems and switch Error-free secondESS electronic switching Framing format Extended trunk access BX.25 DCIU/PI Hdlc Keyboard dialing Kilo bits per second kbps LAN LapdSee basic rate interface See primary rate interface Also wide area network Listed directory numberLocal area network LAN Local exchange company Ncte NAU PAD PVC PDM Robbed-bit signaling 921, and signaling system numberRemote access trunk Protocol converter PC Sdlc TDM UCD UNP Wats Wide Area Service Wats trunkTelecommunications Service Telecommunications Index ARS 2-4,2-7,2-8,2-14plan Bypass access trunk 1-37,4-7,4-8,5-1,5-4,C-2IN-2 Index Logical 6-3,D-19restricted 1-20unrestricted Channel bank 1-9,1-10,1-29,1-30,B-20frame Dial access code 2-2,2-5,2-10,2-13,2-17,3-1,4-4CRC 1-25CSMA/CD 8-13CSU DAC 2-2,2-5,2-10,2-13,2-17,3-1,4-4,4-7,4-8,4-9,6-23 DMI 1-14, D-11 Mode 1-15,1-16,1-42,2-13,9-1MOS6digitizer DS1-Contd FRL 2-10, 2-13 D4 1-24, 1-27ESF 1-24, 1-27 Gateway 7-2 DCS 1-36,2-3,5-14 Statistical 1-17,1-18,1-34LOS B-9,B-13 LWC 6-18,6-21,6-24 ETN 1-36,2-2,2-8,3-1,4-1,5-1,6-1 Analog 1-7,9-2trunk PAD 7-2,8-21PCM 1-5,1-7,1-14,1-18,B-1 DS1 1-13,1-16,1-18 PRI 1-13, D-11 RS-232C1-13,D-9Physical layer 1-11,1-15,D-2,D-9 RS-232C1-13,6-3 1-39, C-3, C-5, C-6 RNX 2-10Subnet trunking 2-11, 2-14, 4-9 Intelligent main 2-4, 4-4, 4-7 TCM 2-11,6-23 Analog 1-3,7-2,7-4 Bypass access 1-37,4-7,4-8,5-1,5-4T1 carrier 1-6,1-18,1-32 ﬁnal 5-2,C-9 Uniform numbering 2-8, 5-1, 5-5 Uniform dial plan 2-5, 2-8, 2-9Analog 1-9 Auxiliary 1-10, 1-35 IN-12 Index