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

B-22SYNCHRONIZATION OF DIGITAL FACILITIES

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		DIGITAL TRANSMISSION FACILITY
		PRIMARY FREQUENCY REFERENCE
. . . . . . . . . . . . . . . . . .		SECONDARY (BACKUP) FREQUENCY REFERENCE

Figure B-14.Improper Use of Backup Facilities

Availability is deﬁned as the ratio of the mean time between failures (the average time between successive system failures, abbreviated MTBFs) to the sum of the MTBFs and the mean time to repair (the total maintenance time divided by the total number of failures during the same amount of time abbreviated MTTR). Low availability (poor transmission performance) is used as a criterion to reject a facility as a reference candidate or to reassign one already chosen.

Characteristics that primarily determine the availability of a transmission facility are rank-ordered as follows:

1.History record

2.Activity

3.Facility length

4.System rate (that is, whether the facility supports T1 or ﬁber)

5.Protection switching

6.Physical type (that is, whether the facility is physically installed as an underground, buried, or aerial paired cable, a coaxial cable, or a radio link). (Satellite facilities should not be used to supply synchronization.)

7.Number and type of regenerative repeaters

8.Number of digital terminal products and other intermediate ofﬁce equipment, if any

Image 230

AT&T 2500 series, 7500 series, 7100 series, 7200 series, 7400 series, 7300 series manual

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 Index Trunking Terms and Capabilities Communications ProtocolsGlossary 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 Document Organization About this DocumentPrerequisite Skills and Knowledge Part ∙ Glossary ∙ Index HOW to Make Comments about this Document AT&T Xx about this Document Introduction to Connectivity 2INTRODUCTION to Connectivity Digital Transmission Transmission TypesAnalog Transmission Analog-to-Digital Conversion Analog VS. Digital 6TRANSMISSION Types Voice Transmission Entering the SwitchTransmission States 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 Zero Code Suppression ZCS Line Coding Line CodingAlternating Mark Inversion B8ZS Line Coding Signal Inversion Restricted ⎜ Unrestricted ⎜ DMI 7Data-Module Capabilities Part 2 D4 Framing Framing ESF Framing SignalingD4 Framing Robbed-Bit Signaling ESF 24th-Channel Signaling⎜ Channels 24th Channel ⎜ 24th Channel ⎜ Frame No ⎜ Isdn PRI Trunk Types/Destinations ⎜ Signaling Types⎜ DMI-BOS Multiplexing Outside the Switch Multiplexing onto T1 Trunks CDM CEM Host Digital DMI PBX Altering Channel Assignments on T1 Trunks Compressing the SignalGetting the Signal Ready for the Central Ofﬁce DR23N DR18M DR18W DR23W Multiplexing with MicrowaveMicrowave System T1 Trunk Capacity Demultiplexing 10.Possible Multiplexed Connections Statistical Multiplexing Local Exchange Trunks TrunkingApplication Tie Trunks Miscellaneous Trunks Special-Access TrunksAuxiliary Trunks Release Link Trunks RLTs Advanced Private Line Termination Aplt Trunks Remote Access TrunksHost-Access Trunks Connectivity Signaling Types Administration OptionsSystem 85/G2 Administration 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 Routing the Call Internal Dial PlanUniform Numbering 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 Private Network Trunks Network AdministrationNetworking Feature Parameters ⎜ 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 Uniform Numbering Plan FeaturesOff-Net Trunks 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 DCS Links Switch Node CapacityDCS Clusters 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 Automatic Callback on Busy or No Answer Transparent Voice Terminal FeaturesAlerting-Distinctive Ringing 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 Assignment Dial-up vs. Dedicated Connections Channel Information Bearer vs. Signaling ChannelsTransmission Mode Changes and Modem Pools 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 Protocol Converters DTE ConnectionsDTE Compatibility Terminal Emulators PC/PBX or PC/ISDN Voice Terminal Adjunct Data Modules DCE PossibilitiesData 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 LAN Protocol Local Area Network ConnectionsLAN Topology Advantages of a Communications System in a LAN Environment LAN ConnectorsLAN Transmission Media LAN LAN Access to/from LANs That Use Other Operating SystemsType Operating Gateway PC System Software Local Area Network Connections Remote PC X.25 Router ISN CommunicationCommunication Between the LAN and Other Networks SNA Gateway Type Operating CommunicationsSystem Package 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 Connections Through Accunet T1.5 and T45 Private Data NetworksTerrestrial Private Data Network Links MPDM/M1* AMI 28PUBLIC and Private Data Network Connections ⎜AMI Satellite Private Data Network Links Integrated Telemarketing Gateway Telemarketing Host ConnectionsIsdn 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 Video Teleconferencing Connections Through Public or Private Data NetworksFile Transfers Image Processing FAX Transmittal 8DATA Communications Configurations Operation Related DocumentsGeneral Reference 2RELATED Documents Related Documents Dimension Administration System 75 and Generic 6RELATED Documents System 85 and Generic ServiceSales 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 Fact Availability of Synchronization SourcesMisconception 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 Trunk-Mode DS1/DMI-MOS TN767 Line-Only Mode DS1/DMI-BOS TN767Trunk-Mode Interface ISDN-PRI + Robbed Bit 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 Detection Glare ResolutionGlare 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 Wink-Start Outgoing Wats Wide Area Telephone Service TrunkWink-Start Incoming 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 IN/DID DOD23/FX-DOD OUT GROUP/CALL Type Signaling 28/WATS-DOD OUT 26/WATS27/WATS 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 Modes Data Mode CapabilitiesDigital Multiplexed Interface 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 CPU BSCCcitt 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 See basic rate interface See primary rate interface Keyboard dialing Kilo bits per second kbpsLAN Lapd 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