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Methods for Verification of Network Timing and

1. G 812 a Normal operation the ring is b After fibre cut node 2 enters holdover c Synchronization restored the ring is synchronized by node 1 and becomes master of the ring synchronized again by node 1 gt Working traffic link gt Protection traffic link Synchronization propagatio Fig 22 SSM Messages on SONET PDH Ring 1 7 Use of SSM can significantly impact the planning of Network Synchronization but is fully chronicled in other industry literature Check REFERENCES Section for more information The TROUBLESHOOTING section will advise site technicians how to read SSM in the network Again it is worth noting the SSM does not guaranty signal quality but does identify traceability If a T1 E1 signal carries an SSM then at least it can be traced back to a BITS source at some point If not the SSM will say Don t Use me SSM codes are standardized worldwide so if equipped with a proper Timing Test Set such as the Halcyon Model GbB310 RITS technicians can clearly read the SSM associated with T1 and El BITS links The 704A can also evaluate the quality and performance of the T1 E1 BITS link as well as Composite Clock CC BITS links This will be thoroughly explored in the TROUBLESHOOTING section Page 22 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links D a fe j ae UF 1T MOVES 17 MEASUR
2. 26 Maintaining Timing in SONET Page 27 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links Iak UF 17 MOVES 17 MEASURES Network Elements Network Elements Network Elements g SH amp S N GPS Grandm asel Clock IEEE 1588 Client Slave IEEE 1588 biienvSlave are 1588 IEEE 1588 IEEE pen ee e LTE Node LTE Node LTE Node Ethernet Integrated IEEE Integrated IEEE 1588 Client 1588 Client Fig 26 Maintaining Timing in Packet based Networks 1 92 Page 28 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links obid ilaa ke UF 17 MOVES 17 MEASURES 1 8 5 There are two basic NTP implementations SNTP and NTP If you are going to install a single server in a small network less than 50 or so clients Simple Network Time Protocol SNTP will work fine However if your plan is larger serving hundreds of clients PCs Network Elements etc then you may need full NTP Full NTP has many expanded capabilities for discovering adjacent NTP servers configuration preferences such as ability to serve as a primary or secondary time source and more These are fully chronicled elsewhere check RESOURSES section for more info In the illustration below the BITS system contains a SNTP Server function providing Time Stamps to
3. 4 Synchronization Signal Stratum Levels Prior to adoption of GPS for synchronization of BITS systems earlier attempts to provide network synchronization followed a hierarchical model as shown in Figure 8 A Cesium Beam oscillator provided precision frequency output and the synchronizing signal cascaded downward through the tiers of switching centers Stratum Level 1 was the most pure signal available so as the signal passed through each level switch transport etc it was of lesser quality more jitter etc Therefore by the time the signal reached the End Office the switching office closest to customers it was Stratum 4 in quality In short the higher the Stratum Level 1 is highest quality the higher the level of stability as compared to the ideal Therefore as the Stratum levels decrease 1 is best 2 is lesser quality 4 is much lesser quality so then do variances in stability Think of it this way the higher the Stratum Level designation number 1 e 4 the more frame slips will occur in the transmission equipment What does this matter Table 1 below provides a glimpse Remember Stratum 1 is as good as it gets followed by lesser quality Stratum 2 lesser still quality Stratum 3 and much lesser quality Stratum 4 This is like your golf score lower numbers are the goal A slip will cause a l l Voice compressed l Primary Office click Cesium Beam Oscillator 7 e A slip can wipe out Facsimile l several lines A slip can
4. FREE RUN BITS signals supplied Again you will soon discover how the use of SSM can aide in such situations GPS Antenna CLOCK OUTPUT Strat 1 Fig 13 Output with good GPS Inputs The CLOCK section contains the backup oscillators which can Holdover the quality of the BITS outputs over time For example if you lost both GPS and the external signal the Holdover Oscillation would maintain as near Stratum 1 as possible A Rubidium oscillator can hold outputs to Stratum 2 or 2e almost Stratum 1 but not quite while oven controlled crystal oscillator can hold outputs to Stratum 3 or 3e almost Stratum 2 GPS Antenna OUTPUT Strat 2e GPS X RECEIVER PRS Fig 14 Output with failed GPS Inputs Page 14 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links ap a fe j aA UF IT MOVES 17 MEASURES There is a big difference in cost between rubidium and crystal oscillators so some logic behind which is best for you If your system contains two GPS receivers then you have one layer of redundancy In other words both GPS receivers antennas or antenna cables would have to fail before any of the holdover oscillators would be utilized However if both GPS receivers failed a rubidium oscillator would Holdover at just less than Stratum 1 for several weeks
5. Mode Timing Insertion Unit 0 c cece cece cece cece eee eee eeneneeees 19 Fig 20 PRS Serving Multiple BITS Distribution Systems c cee eeeeee ones 20 FO 2 nc MOn Tiernan ESETE ERT EEE 21 Pig 2259M on SONED PDH RNE c2docrccstcetececbackaseasenmeenaoeniesonenmnoeres cctaaiues 22 Fig 23 NTP Client Server Example Query Respomnse cccceeeeeeeeeeeeeeeeeeees 24 Fig 24 Microsoft Windows NTP Setup ccc cece ccc e eee e eee eee ee eee eee eee nnnnnnes 25 Fig 25 Configuring Microsoft Windows NTPP for Internet Server 26 Fig 26 Maintaining Timing in SONET 0 ccc cece cece eee c cece cece ene e eee e eee eeenee 2l Fig 26a Maintaining Timing in Packet Based Networks 0 ccccccc cece cece cence eeees 28 Fig 27 BITS System with Built In NTP Server ccccee ccc e cece eee e eee eee eeeee ees 29 Pig 26 WAT NIP Sel VE Scene nsatcestencmanem cso ladeevoanonsenet eee AEAEE ES 30 Fig 29 NTP to BITS yia EMeriels20210242 ccjermctevrcadusataawidsoacesatassttenccdtuatecaseseana 31 Fig 30 Modern Combination BITS NTP System 0 ccc cccccc cece cece eee e eee e eee ne eees 32 FTO ole MO LOOP eeen Er e EAEE EEEa EE err n 33 Fig 32 BITS Site Survey of Network Elements 0 c cece eee cece cece ee enennees 34 Fig Soa BLIS Location Planning 02sec i ctetcecineddcrncaarcawnradasoeouetieheoacdeameesaaeetncsce 35 Fig 34 GPS Antenn
6. cause several seconds of Regional Office dropout Toll Tandem A slip can wipe out Office Compressed video or several lines More Video Conferencing slips can freeze frames End Office for several seconds Switches Channel Slips will reduce RANKS Encrypted data transmission protocol throughput Loss of key Loss of packets Fig 8 resulting in degraded Stratum Levels by office Packet data throughput and re transmission delays SS7 Networks Table 1 Effects of Frame Slips 1 4 Page 10 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links laH k UF 17 MOVES 17 MEASURES Since GPS based BITS systems are widely deployed End Office locations now enjoy the same Stratum Level as peer and Primary Offices However Network Synchronization does not end at the local Central Office End Office Strat Strat Strat Strat 1 1 1 1 Primary Regional Toll Tandem End Office Office Office Office Switches Channel Banks Fig 9 Stratum Levels on Par Network Synchronization Includes the Customer Loop As new services and bandwidth requirements increased T1 and fiber optic transmission systems were extended to customer locations The customer in turn connected terminal equipment of equal complexity often subscribing to service from multiple carriers In many cases ring based self healing fiber optic networks deliver optim
7. cece cece eee e ees 6 gi ee Peer bored oad og Od ps1 s ee ey ere Cree eer re ee eres E E ne ten ene meee ree 7 Pie 4 ple PEM Enk 2 xcccctsaccocensesescatutar taneeaseysedeeacae CEE e 8 Fig 5 Synchronization of Multiple PCM Network Elements 0 c ce ee ee eees 8 Fig 6 External Timing vs Loop Line Timing 0 cece eeeeeeeeeeeeee sees eeeees 9 POs Fig te ECU PAIN CY cee o asrey oeaos ra e peT 9 Fig 8 Stratum Levels by Office Hierarchy the old way eceeeeeeeeeeeeeees 10 Fig 9 Stratum Levels Now on PAR the new way ccccccc eee eeeeeeeeeeeeeeeaeas 11 Fig 10 Synchronization Includes Customer LOOpS 0 ccccccece cece cece eeeeeeeeeeees 11 Pite le asi BIS COCK onreine EAEE E ET 12 Pig 12 BILS Clock Tipu Interia Cis Fass G nhc onloae stipes E a a ciewakeenerenecenna 13 Fig 13 BITS Clock Output w Good Input 0 cece cece cece cece eee e een enes 14 Fig 14 BITS Clock Output w Failed Input cece ccc cece ence eeeeeeeeeeeeeeeeens 14 Big 15 Redundant BIS Syse ireen ote atta daaneneus E E A EEEa 15 Fig 16 Unprotected Output MOd6 3 cciccccnicincan iiss ateinceansaanmaaeabereensiedsavadadeenrssnnnt 16 Pig 17 2Protected Output Port MOGG lt 5 1005o30c 0 derapcaeencannnasydeescenecemadietiecertageadieee 17 Fig L8 Protected Full Output MOGC sicc ccrscceressasenaswtecatienceansideeatinenesaseeneeeates 18 Fig 19 Retimer
8. concerned about the time you gave me perhaps I Il check several other sources and compare the time displays arriving at some logical answer I will use all references available to determine exactly what I believe is the correct time While that is the premise behind NTP let s first examine legacy Synchronization methods Page 6 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing A aa and Synchronization Links alo NOTE UF IT MOVES 17 MEASURES 1 2 The Need for Synchronization in Networks Modern technician lingo blurs the line between several aspects of Network Synchronization In practice it is normal for the following terms to be interchanged by technicians for the same meaning Timing BITS Clocking and Synchronization While the engineering purist objects to this we will delight technicians worldwide by not making a big deal out of it with exception of the sections relating to IP based Network Time Protocol NTP The introduction of Pulse Code Modulation PCM and digital transmission systems into the telephone network resulted in improved quality and efficiencies for transmitting voice and data A single PCM link worked just fine as the digital signals were governed by clocks built into the PCM Channel Banks Switch Channel Bank Channel Bank T1 PCM Database Fig 3 Single PCM link Page 7 of 47 Copyright 2009 2013 dB Lev
9. in IP networks NTP and PTP They are utilized exclusively they are not mixed in the same network generally Page 23 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links a a fe j aA UF 17 MOVES 17 MEASURES Utilization of NTP PTP requires a host server and a remote client In the example shown below a PC is connected via Ethernet to a NTP server resident in a BITS system While this explanation is an oversimplification of NTP PTP protocol the process works like this PC or remote Network Element sends NTP query to the server with a transmit Time Stamp server responds with multiple Time Stamps The query response contains information elements that allow the client to calculate round trip delay of the messages adjusting for the difference and yielding high accuracy as to actual time within milliseconds sub milliseconds for PTP The PC repeats this process for as many times as necessary to establish the initial setting updating at specific periods once hour once day once week based on settings If more than one NTP PTP server exists the NTP PTP client can reference both hosts further increasing accuracy of the end result However for most applications a single server is adequate GPS Antenna PC BITS w built in NTP Server PC to Server gt What time is it asked this question at xx xx xx xx Server to
10. multiple Network Elements and PCs at the site It is possible to utilize a NTP server over several HOPS however this should be limited to less than 6 HOPS for critical applications GPS Antenna Router D S built in SNTP Server Fig 27 BITS w Built In NTP Server Page 29 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links UF 17 MOVES 17 MEASURES NTP is most accurate when multiple NTP servers are deployed One or two servers will source back to GPS and the remaining servers will poll each other This mesh configuration creates an extremely stable time reference system which may achieve nanosecond accuracy with redundancies to eliminate network outages GPS Antenna Servers Fig 28 Multiple NTP Servers Page 30 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links obid ilaa ke UF IT MOVES 17 MEASURES 1 8 6 TDM Sync from an IP Based Network NTP may also be utilized to provide T1 E1 or other signals to locations where it is not possible or convenient to install an exterior GPS antenna First you must establish a site that will be GPS based and install a BITS system with NTP capabilities This will be termed a Grandmaster Clock At one or more remote sites a very small footp
11. to identify troubleshoot and correct Network Synchronization and Timing troubles This must include practical examples for completion of required tasks analysis flowcharts and simplified overview of the concepts of Network Timing and Synchronization This white paper provides directions for connection of laptop PCs Network Sniffers and analysis of NTP links and also use of a timing test set analysis of test results corrective measures and installation guidelines for the three most widely used BITS timing link types worldwide 1 T1 with or without SSM 2 El with or without SSM 3 CC Composite Clock 4 Network Time Protocol 5 Precision Time Protocol 6 IEEE 1588v2 Benefit 1 This white paper will equip telecommunications site technicians to quickly evaluate the quality and usefulness of BITS timing signals with instructions for testing all the way to the Network Element and advanced troubleshooting of NTP related troubles This will result in significant reduction in restoral times for timing related outages and reduction of costly repeated chronic trouble reports Benefit 2 This white paper can be used to or serve as a guideline for establishing routine maintenance procedures that can reduce or eliminate potential timing related failures before they occur by introducing a method for remote long term monitoring of critical timing circuits Benefit 3 Lastly this white paper will provide a fr
12. utilizes Network Time Protocol NTP for short which can constantly update the PC internal clock However for this program to work properly the PC must be connected to the Internet at least once per week so it can poll one of several NTP Servers If you double click the time display a window will appear titled Date and Time Properties Depending on the vintage of your PC WIN2K and previous are doubtful you should see three tabs one allows you to adjust the time and date a second let s you select the proper time zone and the third should be labeled Internet Time Date and Time Properties Date amp Time Time Zone Internet Time Time 6 30 40PM Pe Current time zone Central Daylight Time Fig 24 Windows NTP Setup 1 8 Page 25 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links a a fe j aA UF 17 MOVES 17 MEASURES 1 8 3 Click on the Internet Time tab and you can select from a number of sites in a drop down window the NTP server of choice In this example the NTP server maintained by the US National Institute of Standards and Technology is selected Therefore at regular intervals typically once week the PC sends an NTP query message to the NTP server requesting a Time Stamp If successful a message in middle of screen advises the exact time of the update and also displays the date time for th
13. 1 0 7 freeware 1998 2009 Gerald Combs www wireshark org TIMING amp SYNCHONIZATION EQUIPMENT e TesCom SyncPort www tescomusa com TIMING amp SYNCHONIZATION Surveys amp Assessments e TesCom Inc www tescomusa com Page 4 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links hei iliaValks UF 17 MOVES 17 MEASURES 1 0 The term Timing has historically been associated with Time Division Multiplexed TDM Networks where a Building Integrated Timing Supply BITS utilized T1 E1 Composite Clock or other links to synchronize Network Elements A technician might express I ve got a Timing problem in my office Or I need to run external Timing to that Channel Bank Strictly speaking this is not Timing it is Synchronization Timing is a method for providing a reliable reference of exactly what time it is right now For example the answer might be that it s 10 23 00 or twenty three minutes past ten o clock AM Note that we still don t know what time zone we are referencing EST CST PST etc This is more commonly referred to as a Time Stamp signifying an exact moment in time One of the most widely deployed protocols for time stamping 1s called Network Time Protocol or NTP for short When you think of Timing think Time Stamps Synchronization then is a means for using a frequency reference to stabilize trans
14. 2 Physical BES Shef SiGe rereana aa e 19 oT nos Antenna Loss BUUT esisiini E EAE VENEA LISa Pro s and Cons Tor DUC wees ccc cecentacanansan Ene eaae ENEA 199 82 Von Anena SINE oudere a SEa sees 1 9 9 RF Interference Considerations cccc cece cece eeeeeaeeeeeas LITIU Lichinine Protecto a ict used scan anes aaa Nai e 1 9 11 Physical Placement of Lightning Protection Elements 1 9 12 BITS Output Cabling Guidelines 0 ccc cece cece cece ee eeees 1 9 13 Connecting BITS Outputs to Network Elements 00eee 1 9 14 BITS Output Test Access Arrangements cee cece cece eeeeeeees 1 9 15 Connecting BITS to SONET PDH Network Elements Page 1 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links UF 17 MOVES 17 MEASURES Troubleshooting Section Timing and Synchronization Links List of Tables Tl PRPC 16 00 Frome Goo et cotter ganda Erer EEO iit sea tecceudasaeeeretee totes 10 Tce USUI PrO esre ene tueneautmneteeesueneasencetecenesobet secdane 13 Tocos BITS Output Cable Length Limits 0 cc ccc ee eeeeeeeeeeeaenees 43 List of Figures Fig 1 Timing ys Synchronization esc cosddentesacdacwadevexeeindedgasedaindesedetdaedeus dances 5 Fig 2 Timing amp Synchronization of Network Element 0 ccc ccccee
15. A dB Levels White Paper UF fT MOVES 7 MEASURES Dallas TX USA 214 257 8823 www dblevels com Methods for Verification of Network Timing and Synchronization Links By Daniel B Burch July 2009 UPDATED October 2013 Contents Introduction Problem Statement Previous Options Recommended Solution Implementation Summary July 2009 UPDATED October 2013 0 UO OO WD DW Introduction Guidelines for Network Synchronization and Timing have been adequately chronicled for Network Planners and Engineers however there has been a void in materials and procedures to guide local site technicians and maintenance engineers regarding testing of BITS clock input and output links and troubleshooting of synchronization and timing related problems in general Problem Statement Telecommunications site technicians are tasked with maintaining a wide array and vintage of Network Elements including TDM voice switches Fiber Optic transmission equipment Channel Banks Add Drop Multiplexers and IP based routers gateways switches and management systems For the entire Network to be properly synchronized nearly all of these devices require connections to the Building Integrated Timing Supply BITS Equipment installations for local office and field locations were based on prevailing procedures of the day resulting in a myriad of possible connection arrangements test access points and cabling conventions Overall Synchronizat
16. CM links Page 8 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing a and Synchronization Links Obs es UF 17 MOVES 17 MEASURES 1 3 How Network Synchronization is achieved By connecting one end of the Channel Bank to a common frequency reference External Timing the far end Channel Bank could be configured to derive synchronization from the incoming T1 pulses Loop Timing also called Line Timing resulting in synchronization of both Channel Banks BITS Clock Channel Bank Channel Bank External T1 PCM Loop Timing Timing Fig 6 External and Loop Timing Of course if both ends of the PCM span had clock sources that were on par with each other then you could connect the Channel Banks at each end to their respective BITS as shown below BITS Clock BITS Clock Channel Bank Channel Bank External T1 PCM External Timing Timing Fig 7 External Timing only To insure the Building Integrated Timing Supply BITS in each office are in sync with one another a higher order signal is required for all BITS systems to reference equally In the USA this signal is derived from satellites in the Global Positioning System GPS Page 9 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links D a fe j ae UF 1T MOVES 17 MEASURES 1
17. ES 1 8 NTP and IP type timing Outputs As discussed earlier TDM networks traditionally required only T1 E1 Composite Clock CC or similar synchronization links to Network Elements TDM based networks required Frequency Synchronization with some network elements also requiring Phase Synchronization However as networks migrate to all IP LTE etc the physical layer mechanisms to support TDM frequency references have been largely eliminated Therefore if the new networks are to pass synchronization signals they must be packet based A physical layer technique known as Synchronous Ethernet Sync E has been proposed but would require 100 replacement of network elements to achieve end to end success so at this writing not considered a viable option for most networks Modern networks also present a mix of copper and fiber optic topologies further complicating use of Sync E due to E O and O E conversions The remainder of this paper will consider packet based synchronization techniques 1 8 1 The Inverse of Frequency is Time Frequency Label TIME Period 25 Hz Hertz Hz 4s 5 Hz Hertz Hz 2s 1 HZ Hertz Hz 1s 2 Hz Hertz Hz 5 s 500 ms 100 Hz Hertz Hz 10 ms 1000 Hz Kilo Hertz kHz 1 ms 1000 us 1 000 000 Hz Mega Hertz mHz 1 us 1000 ns 1 000 000 000 000 Hz Giga Hertz gHz 1 ns So if the network will no longer pass a discrete frequency component how is it able to carry synchronization
18. PC gt Time is xx xx xx xx you asked this question xx xx Xx xx ago PC to Server gt What time is it asked this question at xx xx xx xx Server to PC gt Time is xx xx xx xx you asked this question xx xx xx xx ago PC to Server gt What time is it asked this question at xx xx xx xx Server to PC gt Time is xx xx xx xx you asked this question xx xx xx xx ago PC to Server gt What time is it asked this question at xx xx xx xx Server to PC gt Time is xx xx xx xx you asked this question xx xx xx xx ago PC to Server gt What time is it asked this question at xx xx xx xx Server to PC gt Time is xx xx xx xx you asked this question xx xx Xx xx ago Fig 23 NTP Client Server Query Response 1 71 Page 24 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links AD a fe j aA UF 17 MOVES 17 MEASURES 1 8 2 To better understand NTP consider the clock in your personal computer Every PC contains an on board clock which plods along on its own This is not an extremely accurate timekeeper so you may have noticed that over weeks or months the PC clock needs adjusted Look down into the bottom right corner of your PC screen and observe the time display If you have several PCs the time is likely to vary by several minutes or more However modern PCs now contain a small program which
19. PS Antenna SONET MUX T1 SSM Stratum 1 PRS CLOCK OUTPUT On the T1 Facility Data Link the message looks like this F bits FPS 001011 CRC 010011 FDL 0000010011111111 Fig 21 SSM Message on T1 For SSM to be useful connected Network Elements must be configured with instructions for actions to be taken in event of degradation of the SSM code For example a normal SSM message of Stratum 1 PRS indicates the T1 or E1 signal is traceable back to a Stratum 1 source While the SSM is not a guarantee of signal quality it can be used to automatically alert connected Network Equipment if the BITS knowingly becomes degraded Page 21 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links 1 7 1 SSM is especially useful in maintaining sync in SONET PDH rings The illustration below shows how SSM helps nodes on a ring network make changes to where each node picks timing off the network With SSM the ring is able to automatically reconfigure maintaining synchronization with no technician interaction offering ample time for repair of the original fault condition Network master clock X Network X Network X m master clock 39 master clock ai PRC G 811 PRC G 811 PRC G 811 Synchronization Synchronization ynchronization network network etwork SASE clock G 812 SASE clock SASE clock
20. The most labor intensive tasks associated with installation of a BITS system relate to installing antenna and antenna cabling running cables between BITS outputs and Network Elements Of the two antenna installation can be the most difficult so we will examine these issues first 1 9 7 GPS signals arrive at the antenna in the neighborhood of 130dBm which also happens to be near the upper range of sensitivity for GPS Receivers Most commercial GPS antennas feature 30dB of gain therefore the loss budget for antenna cabling is around 15dB Antenna line loss varies by the size type and gauge of the cable For example coaxial RG 58U cabling burns through most of the 15dB loss budget with margin at around 75 feet This incorporates losses associated with connectors and insertion loss of the Lightning Arrestor and connections Therefore antenna runs longer than approximately 75 feet require lower loss cabling such as RG 213U LMR 400 or LMR 600 based on distance requirements Alternative schemes are available that utilize fiber optic cabling or frequency conversion units which allow longer runs of RG 58U up to 1 500 feet Page 35 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links obid ilaa ke UF IT MOVES 17 MEASURES 130 dBm Receive level from satellites Active antenna gain 30 dB 130 dBm Rx Sens Total losses can b
21. a Loss BUCS Cl ssuciccccacavereecdudvscctttciaaieddsddeepaamesciemeddececendceae 36 Fig 35 Down Up Converter External 0 00 cece cc cece cece cece cece eee eneeneeeeeeaneaaes 37 Fig 35a Down Up Converter Integrated 0 ccc ccc cece cece cece cece eeeeeeeeeneaaas 37 Fig 36 Typical Antenna Installations cece cece cence eee eee cece ence eee n eee aeenes 39 Fig 37 AVoid Metal Surface Areas oz sacade sues erste dicede cans ymunewsaesaaine resistia nii 40 Fig 38 Result of Inadequate Lightning Protection cccccc ccc eee eeeeeeeaaaes 41 Fig 40 Inside vs Outside Mounting of Lightning Protection eeeeeeeeeeeeees 42 Fig 40a Lightning Arrester Element cc cc ccccccccccceeceeeeeeeesennnsneeenneenneeeeess 42 Page 2 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links D a fe j aA UF 1T MOVES 17 MEASURES List of Figures Cont Fig 41 DSX Panel Wiring Scheme 0 cece ce cccce cece cece eee e eee eeeeeeeeeeeeeeeeeeeees 44 Fig 42 DSX Panel w Bantam Jacks c cece cece cece eee e eee e ee eee eee eee eneenneeeees 45 References 1 4 Stefano Bregni Synchronization of Digital Telecommunications Networks Wiley Press 2002 ISBN 0 71 61550 1 Chapter 4 Page 137 1 7 Stefano Bregni Synchronization of Digital Telecommuni
22. al reliability in the customer loop Therefore transmission systems beyond the local End Office must be included in Synchronization Planning GPS Antennas Central Office Customer Site Customer Site Fig 10 Sync of Customer Loops Page 11 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links ap a fe j aA UF 17 MOVES 17 MEASURES 1 5 Anatomy of a BITS Clock This overview will equip the reader with concepts of a Building Integrated Timing Supply BITS system Though BITS systems vary in complexity they really perform several simple tasks Here s a block drawing of a basic system Oa T GPS INPUT RECEIVER INTERFACE CLOCK MANAGEMENT OUTPUT PRS Fig 11 Basic BITS Clock 1 5 1 The GPS RECEIVER section contains one or two identical receiver units that provide power to the active GPS antenna decode signals from multiple GPS satellites and convert the data into reference signals and time stamps that will be distributed by various output ports The decoded GPS data and signals are first presented to the INPUT INTERFACE for further processing There are two configurations for BITS systems those with integrated GPS RECEIVERS those with separate GPS RECEIVERS Since even separated GPS RECEIVERS are usually mounted atop the BITS sh
23. alled However installing longer runs of cable than permitted will significantly degrade the signal which could lead to intermittent operation For existing installations this may pose a problem as the existing wiring may have been in place for many years In this case use of a test set to measure the quality and usefulness of the signal is in order This will be fully explained in the TROUBLESHOOTING section Page 43 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links a a fe j aA UF 17 MOVES 17 MEASURES 1 9 13 Connecting BITS to Network Elements Multiple wiring schemes may be encountered when connecting cables to BITS systems For many years wire wrap was the preferred method and many modern systems have maintained that feature However this has largely been replaced by standard RJ48 and other connections which require much less space in the equipment rack 1 9 14 To aide in troubleshooting efforts many companies also wire BITS Outputs through test points such as Digital Signal Cross connect DSX panels The BITS Output circuit can quickly be monitored with a test set for repair efforts As shown below the BITS Output signal can be wired through the DSX panel so that Monitoring Testing or Patching can be quickly achieved greatly reducing troubleshooting time This process fully described in Troubleshooting section Se
24. amework for testing of new Synchronization Plans as they are implemented ensuring that the design objectives have been achieved July 2009 UPDATED October 2013 in practice installation including recognition of timing loops which prove fatal to Network Operations Implementation To achieve the deliverables in this white paper the end user company must acknowledge the identified deficiencies provide minimal to moderate funding of required test equipment review existing practice and procedure relating to BITS testing at the local site and finally condense and distribute the procedures herein inserting any additional safeguards required by your company Such additions may include escalation procedures authorizations for performing routine maintenance and safety procedures for wrist strap grounding where required Summary Since deregulation of AT amp T in the 1980 s telecommunications networks have become interconnected islands of technology with no supreme arbiter to insure all the rules are obeyed As these interconnections span the globe carriers of all sizes can now impact overall network performance and reliability It is critical that every carrier develop a Synchronization Plan which fits well with the rest of the world ensuring reliable self healing transmission paths A key component then is to properly equip and train telecommunications site technicians to adequately maintain timing and synchr
25. ay be installed on each floor of a multi story building or at distant ends of a large floorplan This will be determined by the number and type of BITS outputs required and the distance from the BITS shelf to the connected Network Elements This will be reviewed in greater detail in the section BITS Installation Considerations GPS Antennas i DUAL GPS RECEIVERS PRS T1 E1 w SSM INPUT Ei INTERFACE clocks MANAGEMENT OUTPUT BITS A INPUT Ei INTERFACE clocks MANAGEMENT OUTPUT BITS B INPUT Ei INTERFACE clocks MANAGEMENT OUTPUT BITS C INPUT EE INTERFACE clocks MANAGEMENT OUTPUT BITS D Fig 20 PRS Serving Multiple BITS Distribution Shelves Page 20 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links 1 7 Sync Status Messaging Sync Status Messaging SSM provides a means for Network Elements downstream from the BITS system to be alerted the Stratum Level of the timing signal With a system of coded messages transmitted out of band on a T1 ESF or El signal SSM allows Network Elements to follow an automatic pre determined process for selecting the timing source of the highest Stratum Level thereby eliminating outages due to timing failures For T1 ESF the Facility Data Link carriers the SSM codes as shown below G
26. cations Networks Wiley Press 2002 ISBN 0 71 61550 1 Chapter 4 Page 185 1 71 David Mills Computer Network Time Synchronization The Network Time Protocol CRC Press 2006 Chapter 1 Pages 3 4 1 8 1 9 Microsoft Corp Windows Vista 1 93 dB Levels Inc 1 94 TesCom SyncPort 104 rear photo 1 95 TesCom SyncPort 104 System Manual 385 8000 Rev AF Page 41 1 97 dB Levels file photo 1 98 dB Levels file photo 1 99 dB Levels file photo 2 1 dB Levels file photo 2 2 dB Levels file photo Page 3 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links AD a fe j SS UF 1T MOVES 17 MEASURES Resources BOOKS e Computer Network Time Synchronization The Network Time Protocol David L Mills CRC Press 2006 ISBN 0 8493 5805 1 e Synchronization of Digital Telecommunications Networks Stefano Bregni Wiley Press 2002 ISBN 0 71 61550 1 JOB AIDES TUTORIALS ETC e TesCom Inc www tescomusa com e Virtual Help Desk for Telecom Technicians dB Levels Inc www dblevels com e 1 H E L P interactive Halcyon Electronic Learning Program www tescomusa com CC TITIMING TEST SETs e Halcyon TIMS DDS T1 Recording Timing Test Sets TesCom Inc www tescomusa com e T Com 440B OPT 31 TesCom Inc www tescomusa com NETWORK SNIFFER free versions available for PC e WIRESHARK Network Protocol Analyzer Ver
27. cted or the entire network will collapse upon a GPS failure A Timing Loop occurs when a BITS system is in some way referencing an input signal that is directly or indirectly derived from one of its own outputs GPS GPS traceable T1 E1 Antenna or other reference Inputs Unintentional use of reference signal traceable to the original output on the same BITS Fig 31 Timing Loop Page 33 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links AD a fe j aA UF 17 MOVES 17 MEASURES 1 9 3 What and How Many As previously discussed any BITS installation should be driven by specific dictates of the Synchronization Plan Sync Plan If the office is small with fewer than 64 Network Elements to be connected a Site Survey will provide the details from which a Sync Plan may be developed 1 9 4 A basic site survey consists of an audit of all Network Elements NEs determination of the type of synchronization signals required by each NE availability of suitable power and ventilation location and suitability of existing grounding scheme for the lightning arrestors and access to a clear sky view on the outside of the building From this survey the Sync Plan will identify the size type and number of BITS systems required for the site including redundancy requirements Type Additional Number of Input Number of Input Additiona
28. cturers recommended installation procedure for lightning protection hardware Failure to do so could actually increase the chance of permanent damage to the BITS system Page 41 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links YRVYVIES UF IT MOVES 17 MEASURES In addition to the manufacturer s instructions local building codes must also be understood and applied The subject of grounding is very important and each site likely is equipped with appropriate grounding systems The building engineer should be consulted to locate the most appropriate grounding connection point for the antenna lightning arrestors If not appropriately installed these connections could introduce hazardous and destructive transient voltages into equipment ground circuits The point is you cannot merely grab any nearby ground lightning protection grounds are usually routed directly to the main ground buss away from normal equipment grounds Below is a typical lightning arrestor arrangement Note the Isolation Ground Adapter which actively ground the shield during a strike 1 9 11 Indoors or Outdoors Obviously the antennas are placed in an outdoor environment but what about the lightning protection kit Experts are split on two approaches install protection right at the point the antenna cable penetrates the building outside install protection at the near
29. e next scheduled query In this case the PC was updated 6 33 PM local time on 4 1 2009 and the next scheduled update will occur at 6 30 PM local time on 4 8 2009 Note you must check the box to automatically synchronize or you will have to manually click UPDATE NOW at regular intervals of your own choosing Date and Time Properties _ SE gt gt gt E gt gt gt gt gt __ Date amp Time Time Zone Internet Time i Automatically synchronize with an Internet time server Server time nistgqoy as Update Mow The time has been successfully synchronized with time nist gay on 4 1 2009 at 6 33 PM Next synchronization 4 8 2009 at 6 33 PM Synchronization can occur only when your computer is connected to the Internet Learn more about time synchronization in Help and Support Center Fig 25 Configuring Windows Client to Source a NIST NTP Server 1 9 It is notable that NTP has been around for a very long time but has only recently been more widely adopted deployed and utilized Over the past several years Network Providers have grown to rely heavily on NTP for time management of all critical network elements including call processor records for billing systems network management devices including routers Ethernet switches and the management side of all switching and transmission systems Page 26 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Net
30. e no more than 15 75 MHz Cable Type 15 dB Loss Loss per 100 ft 30 m RG 58 75 feet 23 m 20 dB RG 213 125 feet 38 m 12 dB RG 59 150 feet 46 m 10 dB RG 8 250 feet 75 m 6 dB LMR400 275 feet 84 m 5 4 dB LMR600 450 feet 137 m 3 3 dB LMR1700 1 150 feet 350 m 1 3 dB Fig 34 Antenna Loss Budget 1 95 Page 36 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links D aA UF 17 MOVES 17 MEASURES The larger size LMR cables can get quite expensive requiring special tools and skill for installing connectors At some point there is a cost advantage to installing a down up converter which will allow cheaper RG 58U cable runs of up to 1 500 feet RG 58U Antenna Cable Down Converter Upto1 500 feet gt Up Converter Lower Intermediate Frequency Fig 35 External Down Up Converter copper or fiber Up Converter built into clock RG 58U Antenna Cable Down Converter Upto1 500feet gt Lower Intermediate Frequency Fig 35a Integrated Down Up Converter copper or fiber Page 37 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links AD a fe j aA UF IT MOVES 17 MEASURES 1 9 8 Pro s and Con s for Down Up Conversion The use of Down Up conversion should be carefully con
31. eSeusienradaedaseeedaadenes 15 6 3 Protected Full MOG ss ois tscsis ponsteresdedccndesbadin rinkiin eded kia irian 1 5 6 4 Timing Insertion Mode cc cccc cece cece eee eeeeee eee eeeeneneeeeeeeees 1 6 BITS Distribution Shelves 0 cece eee e eee e cece eee eeeeeeeeeeeeeees ee eee Sync Status Messaging SSM cscccscc cede beactvcweswoesesacthedeenteeeweceedu 1 7 1 SSM in SONET PDH NetWork Secs scones osns vswcendendee cigabesadaciansenctes E Network Time Protocol NTP and Precision Time Protocol PTP 1 8 1 The Inverse of Frequency is Time cc cece eee e eee eeeeeeeeeeeeees e ee EE ULC A OEE ea teceas ee E A T E E Ee a INS Gas E canto E E T T E TA ET 1 8 4 Need for Reliable Time Stamps ccrccsisrciscrisiesssisrirrirsicscinsesie 1 8 4 1 IEEE 1588v2 PTP for packet LTE networks 00 cece cece Pores OC ploy me NIP WP eee E E 1 8 6 Deriving TDM Synchronization from PTP cc cece eee e es L387 5 Purchase a TDM or PIP Clock co issaserassccctexsnsanetensstuweadeniceas ace EI theo BITS Installation Considerations 0c cece eeeeeeeeeeeeeeeeeeeees E Aceua Me OC IA oan cana ene use EN neces E E E E ree DD eect TM TGS oes reece cane ne von dgente agg tun mee etees a caaueneraneneseuces Deiat erg enn oe ase Saran EE EE E A E E ues L9 Scene RECUNGANCY IREGQUITCINEING vasiuuinyvernasuniusdaeuersdeanandatede bastuuseendes L 9 6
32. ected Port Mode Page 17 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links hei iliaVatk UF 17 MOVES 17 MEASURES 1 5 6 3 In Protected Full Mode the Network Element will have two Sync Input connectors example Input A amp Input B or Input 1 amp Input 2 These may be wire wrap or RJ type connectors The BITS outputs are taken from adjacent output cards but the ports are not set up as Protected Port Rather the Network Element has two independent sync links so that in event a BITS card or cable fails the second sync input is unaffected In this case both BITS links are active all the time This is the most preferred method for connecting Network Elements to a BITS system MUX etc T1 E1 w SSM Output Card 1 Port 1 Output Card 2 Port 1 T1 E1 w SSM BITS OUTPUT Fig 18 Protected Full Mode Page 18 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links D aA UF 17 MOVES 17 MEASURES 1 5 6 4 Timing Insertion Mode allows Network Equipment that has no external sync port no extra pins used just for sync input to be brought into the same level of synchronization as adjacent Network Elements that have dedicated BITS connections Basically the traffic bearing T1 E1 to the Network Elemen
33. eee 4 MON JACK MON JACK OUT JACK OUT JACK i J i IN K M hy Digital a gt Equipment CROSS CONNECTS d DSX Fig 41 DSX Panel Wiring Scheme Page 44 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links AD afe aA UF 17 MOVES 17 MEASURES Two basic types of DSX Panels are prevalent Bantam Jack and RJ45 Jack Both types are shown below Gi 4 rl 71 1 4 ee cee ececcceccosscs ececcccccooces men 2 os l Ra e i i pN es lt lt mY f a te Lat M i a i9 171 i i SEEGER ESSER E808 eeceeeeeoesees Secccccccoeees 2565685558885 8SS SSHSSTSSSSSGSSGS Sseeeseseecesen ASS SS SSS SSS ecoooon ee a TS Gg ih AAD BA eT e PANEL 7 th C if J a 1 a0 E ia LETTI T T EE 5 gt z a i rs JHSS e P e 4 a n He e mI lg lt ily li a ow 7 iy tion i arai p ji ipi Ty Fig 42 DSX Panel with Bantam Jacks Fig 43 DSX Panel with RJ45 Jacks Page 45 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links D a fe j eS UF 17 MOVES 17 MEASURES 2 0 0 Clock Families Unfortunately much of the GPS Clock world remains fractured in terms o
34. elf we will consider them as a whole The reason they are separate in large systems is that several distribution shelves may make use of the same GPS RECEIVERS The separate GPS RECEIVERS may also be labeled Primary Reference Source PRS as the literally are the primary source of Stratum 1 for the office Some PRS systems also contain their own holdover oscillator s apart from what may be in the BITS shelf Page 12 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links 1 5 2 The INPUT INTERFACE allows several types of signals to drive the system including single or dual GPS T1 El or Composite Clock CC and SMHz or 1OMHz from another BITS system or Stratum source However other than GPS all other input signals must be traceable to originate from a Stratum 1 source or equiv GPS TI E1 wiSSM INPUT INTERFACE cc 3 10 MHz IEEE 1588 v2 PTP WUT Fig 12 BITS Clock Input Interface 1 5 3 The INPUT INTERFACE CLOCK and MANAGEMENT sections all work together to determine the best available reference for maintaining stable outputs with a default pecking order The priority list assumes GPS is reliable and the external T1 E1 or other signal is from reliable source While you may change the list in software typical default is 1 PRIORITY 2 PRIORITY 3 PRIORITY 4 PRIORITY Table 2 BITS Input Priorit
35. els Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links D es UF 17 MOVES 17 MEASURES However when end to end connections traversed two or more PCM links subtle deviations in the Channel Bank clocks allowed frame slips causing audible clicks in the voice traffic and occasional interruption or slowness of data connections Channel Bank Channel Bank Hi how are you doing Switch T1 PCM clicks heard Hi how are CLICK doing Fig 4 Multiple PCM links The solution was to connect all Channel Banks with a common frequency reference synchronizing the internal Channel Bank clocks There were actually two clock signals in the Channel Bank 64kbps and 8kbps called BIT and BYTE respectively These clock signals are utilized to convert analog voice signals into a PCM data stream aligning the encoders and Framers which drive the T1 output signals Since it was impractical to wire BIT and BYTE clock leads from the Building Integrated Timing Supply BITS a composite signal was developed allowing a single link between BITS and Channel Bank The composite signal consisted of 64kbps stream with a purposeful error every 8kb and is called Composite Clock CC BITS Clack t Channel Bank Channel Bank Hi how are ey you doing No Audible Ti PCM clicks heard Hi how are you doing Fig 5 Multiple synchronized P
36. est point the antenna cable enters the building inside Both concepts are radically opposed yet both agree that the point of entry or the wall through which the antenna cable passes is the right spot This stops the lightning surge from traversing all the way into the equipment room This will or course be governed by local ordinance codes and company policy Fig 40 Inside vs Outside 2 1 Fig 40a Lightning Arrester 2 1 Page 42 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links D a fe j ae UF IT MOVES 17 MEASURES 1 9 12 BITS Output Cabling This section will explore the process for connecting Network Elements to the BITS outputs Recall our earlier discussion that the Sync Plan should drive all requirements for connecting Network Elements provisioning links and ensuring no Timing Loops are constructed The Sync Plan should also yield an assignment record that instructs provisioning out each output designation of protected paths and CLLI code or other identifying code for the connected equipment Some BITS systems offer internal port assignment logs to maintain on site records However this information must be routinely updated or reliability will suffer as the network undergoes rearrangements For troubleshooting efforts nothing is more important than a record of output assignments on a per card basis As pr
37. etworks placement of several non redundant clocks around the ring may eliminate the need for fully redundant systems at each site 1 9 5 Historically redundancy was thought of as ordering two of each critical component within the system proper However due to shrinking system footprints a new concept has emerged called Shelf Redundancy With Shelf Redundancy you order a non redundant system times 2 meaning you mount identical systems together achieving 100 redundancy down to the backplane You still have two antennas GPS receivers holdover oscillators and outputs they are just associated with completely separate shelves This arrangement is frequently lower cost that a fully loaded single shelf redundant system as newer technology offers significant improvements in cost per port as compared with older hardened designs Page 34 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links a a fe j aA UF 17 MOVES 17 MEASURES 1 9 6 Where Planning and installing a BITS system into an office is a daunting task The two prime considerations relate to the distance from a proposed equipment rack bay location to the majority of Network Elements to be connected and the distance from the bay to an outdoor location where GPS antennas will be mounted Network GPS Elements Antennas Fig 33 BITS Location Planning
38. eviously discussed each output type carries a set of requirements for staying within the useful range of proper operation While the main qualifier is cable length this can be greatly impacted by the size type and gauge of cabling used to connect the Network Elements Assuming proper cables installed typical distance limits are shown below eet Table 3 Output Limits For T1 E1 connections it is important to employ a suitable cable which is rated for T1 E1 signals Inexpensive fine gauge UTP will yield poor results The suggested cable is two conductor twisted pair shielded 22 gauge solid copper with a drain wire A drain wire is a bare solid copper wire that is wrapped tightly against but outside the shield The wire connects to a grounding point at the Network Element to eliminate noise and signals which may be couple to the cable In most cases the drain wire is not attached at the BITS end but is insulated with heat shrink tubing Unless dictated by local code or company policy it is not recommended that both ends be grounded as this will result in a ground loop that may actually cause more noise to be coupled to the inner wires When it comes to selection of wire types check the manufacturer s recommendations as they likely have tested their equipment with many cable types and best positioned to provide this information The distance limits shown above are for general planning and may vary based on the type of output cards inst
39. f scalability Few clock manufacturers utilize common parts between platforms with completely separate requirements for installation practices antenna requirements and sparing policies Throughout this whitepaper we have utilized the timing products from TesCom Inc including the SyncPort line of scalable clocks and a small footprint GPS PTP client clock All three models of the SyncPort line 1 RU 2 RU 3 RU utilize the same antennas lightning arresters output cards and connector arrangements Ethernet NTP PTP Management cards System commands SNMP and management conventions GUI pages menu titles front panel LED scheme and more So you can use the 1 RU in small offices or as a PTP client slave and the 2 RU or 3 RU in larger offices while keeping most maintenance requirements the same across all offices All three shelves can operate in IEEE 1588 PTP Grandmaster or Client Slave mode and their IEEE 1588 PTP pricing is a fraction of the cost for competing systems All SyncPort systems offer multiple AC and DC powering options over 200 output types multiple means of management and in many cases are drop in replacements for legacy clocks of any manufacturer The 1 RU shelf offers up to 32 outputs including IEEE 1588v2 PTP the 2 RU shelf offers up to 64 outputs including IEEE 1588v2 PTP the 3 RU shelf offers up to 104 outputs including IEEE 1588v2 PTP Many outputs also available in optical format and IEEE 1588 PTP available
40. ghtning rodents animals theft or vandalism so why spend the money for redundancy everywhere but the antenna However installing twin antennas in Down Up systems is usually cost prohibitive Use of standard L1 band GPS antennas provides greater flexibility in long term maintenance for antennas and lightning arresters If the OEM of Down Up shutters operations or drops support of your scheme the clock is useless However there are several quality manufacturers for antennas and lightning arresters significantly reducing the risk of dealing with vendor proprietary elements Page 38 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links Laas UF IT MOVES 17 MEASURES 1 9 8 Antenna Siting The most critical step in BITS installations is careful selection of the antenna site If you get this wrong the BITS clock will be plagued by intermittent troubles for the life of the system While it is imperative to adhere strictly to the antenna cable loss budgets this will be for naught if the antenna is located in the presence of interfering signals or blocked from a clear view of the sky Basically the antennas need to be installed with no less than 30 feet of separation In fact use the most separation your cable length will allow The extra length could save one of the antennas in event of a lightning strike tree limb or vandalism shotgun bla
41. in 100BaseT or Gigabit Ethernet These clocks are all Made in the USA All SyncPort datasheets available www tescomusa com See Next Page Page 46 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links D LaYvalbs UF 17 MOVES 17 MEASURES SyncPort 32 GTF Module AENA e TE L a a A i TERET KEO i i s A n eg pres A iN aS f SyncPort 104 O00000 Edi Wanu Ester Cont SyncPort 104 TesCom This concludes the Overview Section Page 47 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013
42. ion Planning was thwarted by failure to properly connect all related Network Elements fueled by installations which did not follow strict standards Most locations adhered to some level of Synchronization Planning so the Network was generally stable for long periods of time Historically site technicians rarely needed to work on BITS so they possess little if any knowledge or understanding of neither the local BITS system nor its relevance to network troubles However as Network transmission rates and channel capacities have risen so also have outages related to Network Synchronization The implementation of Sync Status Messaging SSM on T1 and El timing links greatly increased reliability and complexity of Synchronization Planning and testing SSM provides a means for Network Elements downstream from the BITS to be aware of the traceability of the timing signal with a hierarchal system of coded messages Transmitted out of band on El and the Facility Data Link for T1 SSM allows Network Elements to follow an automatic pre determined process for selecting the timing source of the highest reference thereby eliminating outages due to timing failures Network Time Protocol PTP and Precision Time Protocol PTP TEEE 1588v2 are now also widely implemented across carrier networks supported by little if any procedure for turn up and maintenance testing Currently site technicians lack 1 Test equipment to
43. ive diagnostics on the BITS system The most commonly used commands analyze the integrity of the antenna circuit for proper operation display the number of GPS satellites seen and the value of the received signals for timing purposes the length of time the system has remained at Stratum 1 and other critical issues like condition and status of holdover oscillators Page 15 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links 1 5 6 Finally the OUTPUT section provides physical access for connecting jumpers or cables to each connected Network Element The outputs generally have been wire wrap pins but a variety of modular connector types are in use including individual female RJ45 or BNC connectors There is a very wide variety of output types including T1 E1 Composite Clock CC 5 10MHz 2 048 MHz square wave RS422 1 5MHz RS422 8KHz 1PPS IRIG B NTP PTP and more How do you know which output is right for each Network Element Consult the user s manual There are four ways to connect Network Equipment to the BITS system Unprotected Protected Port Protected Full and Timing Insertion 1 5 6 1 Unprotected Mode means that the Network Element has only one Sync Input connector Channel Bank for example and does not warrant redundant card protection In this case an output card sync cable or Sync Input failure would result in s
44. l Network Element Required Inputs Requirements Inputs Distance to BITS Alcatel Channel Bank CC 1 8 Alcatel Channel Bank CC 1 o J o o 120 ft Cisco SONET TIW SSM 2 NP 1 t SESS a a2 S y f OOA Fujitsu DSLAM CC 2 NP 1 20t O E e e Fig 32 BITS Site Survey NEs Once the audit of Network Elements is completed it is a simple thing to tally up the number of required outputs by type Note in the example above one Network Element Brand X MUX has no external sync input so will have to be Line Timed on the traffic bearing T1 This can be accomplished via a Timing Insertion Unit where the traffic bearing T1 is looped into and out of the BITS system In most small offices all Network Elements will be within allowable distance limits from the BITS system Larger offices especially with multi floor buildings will require up to several BITS Distribution Shelves The BITS Distribution Shelves have to be engineered so that the allowable output cable distances can be met without violating the distance limits between the BITS Distribution Shelf and Primary Reference Source locations These distance limits will be fully explored below Redundancy requirements vary and based on each companies synchronization philosophy Larger companies usually opt for dual antennas antenna cables GPS receivers and holdover oscillators employing Protected Card or Protected Full output redundancy For companies with SONET PDH n
45. mission equipment across a single or multiple locations Router Server Serial or Ethernet Timing Output Time stamp data Timing and sync Outputs T1 E1 wW SSM Synchronization Output Frequency Reference SONET PDH MUX Fig 1 Timing vs Synchronization Page 5 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links ep a fe j aA UF 17 MOVES 17 MEASURES In some cases Network Elements require connections for both Timing and Synchronization For example a Voice over IP Gateway needs to be synchronized on the TDM side yet requires Network Time Protocol NTP for accurate time stamping on the IP side Likewise a SONET PDH Node may require Synchronization for network traffic and NTP for accurate time stamping of events like alarms or status changes Ethernet VoIP THE Gateway Time Stamp Data For IP Side Timing and sync Outputs T1 E1 wW SSM Synchronization Output Frequency Reference For TDM side Voice Switch Fig 2 Timing amp Synchronization Of Same Network Element 1 1 Allow this analogy to illustrate the difference between Timing and Synchronization If I ask you What time is it I d expect you to look at your watch and tell me the time not hand me a metronome so we could stay on beat with musical instruments In fact if I really am
46. nd Synchronization Links Ofe LEVES UF 17 MOVES 17 MEASURES This section provides an overview of basic considerations for typical BITS system installation at a site The need for BITS at a location should be driven by Network Planners utilizing an instrument called a Synchronization Plan or Sync Plan for short 1 9 1 The Sync Plan should be the guiding reference tool for all BITS installations decisioning of the BITS type size and redundancy connecting of Network Elements and management troubleshooting directives Routine maintenance of BITS output links does not require access to the Sync Plan Failed output cards or cables improper output configuration and basic BITS system analysis are pretty logical tasks If Lightning damages one of the antennas replace the antenna If an Output card fails replace output card However persistent unexplained troubles require a closer look at the entire synchronization strategy Frequent dropped calls sporadic errors in 56 64kbps DDS and or T1 E1 circuits bearer traffic issues on ISDN channels SS7 failures unexplained trunk failures and frequent multiple alarms are all indicators that synchronization problems exist 1 9 2 When contacted for technical support on difficult synchronization troubles experts will always want a look at the Sync Plan You have to know where synchronization starts originates and where it ends what s connected It is crucial that Timing Loops be identified and corre
47. ng and Synchronization vendors will gladly assist in reviewing your needs If the predominance of your output requirements are Synchronization based T1 E1 CC etc then the best solution is to add NTP capability to a new or existing BITS system However if the majority of your needs are on the IP side purchasing a GPS based NTP server is best Most commercial NTP servers also have a limited number of Synchronization outputs as well so today you can have both in a single package Below is the rear view of a modern combination BITS NTP system available in ANSI or ETSI versions that may be equipped with single or dual GPS Receivers up to 2 external inputs single or dual Rubidium crystal or mix of Rubidium crystal holdover oscillators and 64 outputs that can be programmed by port allowing you to skinny down or fatten up as needed The system also offers IP connections for SNMP management and up to two ports of SNTP and IEEE 1588 v2 all at only 2 Rack Units RU Just a few years ago this same capability would have consumed 10 RU The SNTP option for this system sells for under US 800 Today there is no reason to buy separate elements for providing Synchronization and Timing outputs Fig 30 Modern Combination BITS NTP System 1 94 1 9 BITS Installation Considerations Page 32 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing A aa e e e D Cai D a
48. ng pattern RF path of nearby antennas If the loss budget is respected the antennas free of interfering signals and away from broad metal surfaces and the lightning arrestors properly connected the BITS clock can provide decades of worry free service However if you break the rules be prepared for intermittent problems and lots of nighttime work tours Page 40 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links UF 17 MOVES 17 MEASURES 1 9 10 Antenna Lightning Protection As previously discussed the antenna element is the most likely point of failure in a BITS system excluding configuration errors It should go without saying that any element that breaches the office walls should be adequately protected from delivering harmful voltages into the equipment room Failure to do so routinely results in failures as shown below which can cost upwards of 8 000 to repair r 1 i a Tm _ _ Wwe PTTTTIL Tt ttt or UWA mi G a Fig 38 Result of Inadequate Lightning Protection 1 99 For active GPS antennas special protection devices allow normal operation and isolation from ground except the duration of a lightning strike The isolation and protection elements activate and if not damaged or destroyed faithfully return to the previous state It is critical to observe the manufa
49. onization links at the local level If not services will be unreliable and noisy calls will be dropped Internet connections will slow and HDTV images will be irregularly pixilated ruining the quality so heavily touted by broadband connections Methods for Verification of Network Timing and Synchronization Links D a fe j ae Table of Contents Overview Section Introduction to Timing amp Synchronization including NTP PTP and SSM 1 0 Timing vs Synchronization cccccc cece eeeeeeeeeeeeeeeeeeennes Elaes Wristwatch vs Metronome 0cceeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeees Pien Need for Synchronization in Networks 00eeeeeeeeeeeeeeeeeeeees Bes E How Synchronization Achieved ccccccc cece cece ee eeeeeeeeeeenaaees 1 4 Sy Saum VC 2 conyers cntuuetooceanvanesamsatacasareinaacoonedaseses LD esae Anatomy of a BITS Clock 0 ccc ccc cece cece cece cece ee enenaannes Fake D PRCC CIV ENS 54 aban teen ceg EEO EES Easa MOU LICL GCC eea EERO N A Eae PACKING PO cet eee eE EE EE ASE 1 5 4 Holdover Oscillators 0 ccc cece cece eee e eee e eee e eee e cece eee eeeeeeeeeeeees 15 5 BITS Clock Managements cccanecstwededasmueseninpansestaaieaannwcesess gnaw LSG DUS OUDUIS 2 2s2c lt setsntetedscnaronedndsosdsnehcasaseteulsenianerttasidaoscdooed 1 5 6 1 Unprotected MOC oiiecicsntwiesccsvesetontadate niken naea 1 5 6 2 Protected Port MOG ie 64 05 ccs tisceeetsseseelevetausdan
50. properly evaluate BITS output signals including readout of critical SSM codes for T1 and E1 signals 2 Procedures for testing BITS and NTP output links 3 Training to quickly identify Network Timing and Synchronization problems July 2009 UPDATED October 2013 Previous Options The common fall back method has been to closely monitor alarms in the BITS equipment at the System Level with hopes that individual timing output troubles could be detected at the higher level However this is often not the case Modern GPS based Network Synchronization Systems do provide alarm monitoring to determine overall system operation quality and usefulness of the GPS signal status of antenna cables and antenna operation and a limited number of output related faults such as shorted output cables Troubleshooting methods were generally directed from a distant Network Operations Center NOC with the local site technician performing eyes and ears function for the NOC engineer Cards could be swapped LEDs viewed for activity etc However at some point the NOC engineer must direct the site technician to perform physical maintenance activity such as cable testing tracing and Network Element connection verification At this point the local technician was very limited in availability of tools and training Recommended Solution The solution is to provide telecommunications site technicians with tools and information procedures
51. rint Edge Client Edge BITS device accepts the NTP feed over Ethernet connection and converts the precision information into stable BITS outputs such as T1 El 1Pulse Per Second or 5 1OMHz The benefit of this arrangement is that the Grandmaster Clock is only moderately priced but the Edge Client devices are usually priced under 2 000 Therefore one Grandmaster can provide Stratum quality synchronization signals to a dozen or more end locations served only by your internal Ethernet network GPS Antenna Edge Client Edge Client Edge BITS Edge BITS nan i wa _ a s eel E hemet Ei En E e m Edge Client Edge Client Edge BITS Edge BITS Grand mast r T1 E1BITS Signal Fig 29 NTP to BITS via Ethernet 1 93 Page 31 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links Leafs UF 17 MOVES 17 MEASURES 1 8 7 Purchase a TDM or PTP Clock The decision of which time protocol to use will be based on the current and future design of you IP network NTP may be utilized in almost any network configuration that meets minimal guidelines However 1588 requires some additional network topologies and performance enhancements already are in place such as QoS Therefore significant improvements may be required for existing networks However when developing a new network such issues will likely be mute Timi
52. sidered as there are significant implications for long range office planning sparing costs and dependence on proprietary equipment Here are the Pro considerations 1 Allows use of lower cost RGS8U cabling for extreme antenna lengths Conversely here are several Con considerations 1 GPS signal may not be shared with other devices connects only to the specialized Up converter All Down Up elements are vendor proprietary vendors support longevity Many Down Converters require separate power at antenna Requires non standard lightning arresters An additional point of failure Complicates troubleshooting procedures Expensive to maintain replacement parts ieee a Through installation of an active GPS splitter unity gain or gain standard L1 band GPS signals 1575 MHz may be shared among many GPS devices in the same building However if Down Up converters are employed where the Up conversion is inside the clock no signal sharing is possible This greatly limits use of the incoming signals which will require additional antennas for any additional equipment Most clocks utilizing Down Up conversion utilize only a single antenna regardless of the number of internal GPS receivers However if you are spending extra money to achieve redundancy in major elements such as GPS receiver oscillator etc it makes no sense to limit the installation to a single antenna The antenna is the most exposed part in the entire system prone to damage from li
53. signals to network elements The answer is based on the simple premise that the inverse of frequency is time Therefore if one can produce a reliable accurate flow of time stamps a frequency component may be recovered and utilized for frequency and phase references For three decades Network Time Protocol NTP has been employed to carry time stamps which resolve to millisecond accuracy in telecommunications power generation manufacturing automation financial transactions and medical applications However modern network elements require sub millisecond accuracy so for synchronization purposes NTP has been replaced by a newer protocol entitled Precision Time Protocol PTP and more specifically the version of PTP known as JEEE 588v2 One key benefit of PTP IEEE 1588v2 is use of Profiles for the types of networks to be installed For example a communications network has different synchronization requirements than a power generation management network therefore rather than having a generic PTP which requires the user to manually configure a dozen or more critical parameters in the PTP client or server a quick setup is achieved by invoking the appropriate Profile for the network requirements For example most telecommunications networks utilize the Telcom Profile for PTP greatly simplifying the installation process especially when adding new clients Therefore two different methods for achieving accurate time stamps are employed
54. st etc Locating antennas away from public view is highly desirable The antennas should not be the highest object on the roofline Rather they should have a clear view of the sky with an angle of at least 45 degrees and also a view of the distant horizon if possible Use of conduits is suggested mostly to protect the cable from deterioration Avoid tree branches radio transmission antennas and low placement on high vertical walls Fig 36 Typical Antenna Installations 1 97 Page 39 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links p es UF 17 MOVES 17 MEASURES 1 9 9 RF Interference and Metal Surfaces It is not recommended to locate the antennas near broad metallic surfaces as shown below The metal can potentially act as a reflector for interfering signals and also be a magnet for lightning strikes This installation looks beautiful but should be relocated Se m i en i a l fa s i on T Y _ Pj g a Fig 37 Avoid Metal Surfaces 1 98 Do not install GPS antennas near transmitting antennas or high power antenna feed lines RF leakage and direct radiation can wipe out or intermittently interfere with the GPS signals which are at 125dB Take note of any radiating elements and also beware of line of sight path violations where the GPS antenna is placed in the radiati
55. t is looped through the BITS system where the traffic bearing T1 E1 is re timed Therefore the T1 E1 bearer traffic is maintained but the Network Element is now synchronized with all other Network Elements connected directly to BITS To the Engineering purist re timer is a misnomer however it is the accepted term for this mode of synchronization The more correct term re synchronizer is just too clumsy Incoming Traffic bearing T1 E1 wi unknown sync NE with no external BITS port TIU Re Timed traffic bearing T1 E1 BITS OUTPUT Fig 19 Re timer Mode w Timing Insertion Unit Page 19 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links ap a fe j aA UF 17 MOVES 17 MEASURES 1 6 BITS Distribution Shelves In larger office locations a single Primary Reference Source PRS may provide Stratum 1 links to one or more BITS Distribution shelves Recall an earlier discussion that there are two configurations for BITS systems those with integrated GPS Receivers those with separate GPS Receivers Systems without GPS Receivers are referred to as BITS Distribution Shelves There is no need to install multiple sets of PRS in the same site so a large building can be surveyed placing BITS Distribution Shelves at strategic locations For example BITS Distributions Shelves m
56. unit you could repair the receiver antenna or cabling A crystal oscillator would Holdover several days but at a lower Stratum level than rubidium Therefore rubidium buys you longer holdover at higher quality than crystal oscillators Some companies equip BITS systems with two of every critical component two antennas two receivers two oscillators two output ports per connected element This is called Full Redundancy However before the second oscillator would be used both receivers and the primary oscillator would have to fail so in some cases it may be appropriate to have a primary rubidium and secondary crystal holdover oscillator It is highly unlikely but not impossible that the secondary oscillator would ever have to carry the day The decisions for the number and type of receivers and oscillators are governed by your company guidelines and may vary by site GPS Antennas oe GPS GPS i INPUT RECEIV RECEIV INTER INTER OUT OUT ER ER RACE FACE CLOCK CLOCK MANAGEMENT 5 ane PRS PRS Fig 15 Redundant BITS System 1 5 5 The MANAGEMENT section of a BITS system is pretty self evident That is it allows communications via Serial and or Ethernet ports offers configuration menus manages and displays sends alarms and generally keeps track of the rest of the system The MANAGEMENT section provides a means for performing simple or exhaust
57. work Timing and Synchronization Links op fej aA UF 17 MOVES 17 MEASURES 1 8 4 Need for Reliable Time Stamps While you may consider the PC clock to be a mild convenience consider the benefits of maintaining accuracy of the local clock Many clients PC programs make use of the time stamp for events such as email bank transactions stock purchases ebay activity etc Also Windows uses the clock to maintain files updates events so that if needed critical information can be retrieved to restore from a PC crash It really is best if you keep the clock current 1 8 4 1 The use of NTP PTP has grown way beyond simple timekeeping for administrative and maintenance purposes Reliable 7ime Stamps form the basis for numerous Network Utilization and Performance measuring tools Customers now demand some form of proof for network performance such as availability throughput and latency Accurate Time Stamps are the key to delivering real time reports for network performance In the drawings below BITS systems SyncPort are used to supply T1 and PTP to both TDM SONET and Packet LTE networks The PTP method is also useful for Pseudo Wire Emulation PWE Network Elements PWE is the method for transporting TDM signals like T1 across a packet networks Network Elements Network Elements Network Elements g SH Q GPS ei i Clock Clock Djstributor Clock Djstributor Fiber Fiber SONET Node SONET Node SONET Node _ Fiber Fiber Fiber Fig
58. y Therefore if a GPS signal is present that is first priority and is Stratum 1 If GPS fails the external input may be considered the next best source This depends on a couple considerations Over a period of hours days the BITS system will compare the External Signal with the GPS reference If the signal is of sufficient quality the system will maintain it in the priority list Additionally if the signal is a T1 or E1 with SSM the system can immediately determine the traceability to a BITS source This will be explained in detail in the next section Page 13 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links p fej aA UF 17 MOVES 17 MEASURES 1 5 4 If neither GPS nor External Signal is acceptable the system will fall back to HOLDOVER Holdover quality is based on the type of Holdover Oscillator installed in the system If the GPS or External Signal is not restored within the range of the Holdover Oscillator the system will degrade to FREE RUN condition This is to say the output signals are likely at or below Stratum 4 and troubles at the local office are likely Even though the system is in FREE RUN at least all the outputs of the same BITS system are pretty close in quality However that creates additional problems when SONET equipment is used as SONET elements contain an internal Stratum 3 clock which may be better than the
59. ync loss to the Network Element While this was standard practice over the years many companies now demand at least Protected Port Mode MUX etc T1 E1 w iSSM Output Card 1 Port 1 BITS OUTPUT Fig 16 Unprotected Mode Page 16 of 47 Copyright 2009 2013 dB Levels Inc All Rights Reserved Ver 2 1 10 2013 Methods for Verification of Network Timing and Synchronization Links olsi Liavalks UF 17 MOVES 17 MEASURES 1 5 6 2 As stated above most companies require single input Network Elements to be protected at least at the card level This means the primary output is coupled internally or via a Y cable to an output of the same type on an adjacent output card The outputs work as a pair with one working and the other in standby mode In event of failure the secondary card is quickly activated so that sync is maintained to the Network Element NOTE generally protected card arrangements must be configured in the BITS shelf with specific outputs assigned Some systems do offer automatic protection of cards without the need for Y cables Consult User s Manuals Also make sure the selected outputs are configured prior to connecting any Y cables or you will be shorting live outputs together which may result in card damage This is called Protected Port Mode MUX etc T1 E1 w SSM Output Card 1 Port 1 Output Card 2 Port 1 BITS OUTPUT Y Cable Fig 17 Prot

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