synchronization the “heartbeat” of the office

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SynchronizationThe “Heartbeat” of the OfficePresented by Lisa Carlisle


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Agenda• Sync Standards• Two Aspects of Synchronization

– Components of the Building Integrated Supply (BITS) systems– Intraoffice Timing Distribution to the receiving Network Elements

• Why are we doing so many BITS clock installations• Engineering Considerations• Installations Considerations• Waivers• Record Keeping• Summary• Questions


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AT&T Sync Standards• AT&T Sync Standards originated from various Telcordia standards– GR-436-CORE Digital Network Synchronization Plan (documents the Building

Integrated Timing Supply (BITS) concept)– GR-1244-CORE Clocks for the Synchronized Network: Common Generic

Requirements (covers generic network element interfaces)– GR-378-CORE Generic Requirements for Timing Signal Generators (covers

TSG’s, aka “BITS Clocks”)– GR-2830-CORE Primary Reference Source: Generic Criteria (covers Stratum 1

sources: GPS and Cesium)• SBC, AT&T Core, BellSouth and AT&T Mobility practices were

consolidated into the current sync sections of TP-76300 and TP-76400• The sync sections of these TPs are subject to continued refinement as

technologies evolve and clarification is needed


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Two Aspects of SynchronizationThe Synchronization installations in an office include the BITS ensemble itself and providing timing references to elements in the office that require an external timing source• Components of the BITS system (sometimes called the “clock”)

– Primary Reference Source (PRS) – not necessarily at every office and connected to the Timing Signal Generator (TSG) via twisted pair (DS1 connection)• GPS PRS requires the installation of an antenna either on the roof top or “through the wall” –

gets its Stratum 1 traceability from the GPS satellite constellation• Cesium PRS – stand alone unit installed in the same relay rack as the Timing Signal

Generator– Timing Signal Generator (TSG) provides the timing outputs used as references for all

the Network Elements that require an external timing source• Output generation signal type is driven by the card type installed in the TSG or via software

options set up when the output card is placed in the shelf• Most common output signals are DS1 or Composite Clock – used for traditional TDM Network

Elements• Packet based timing is beginning to be deployed in the form of Precision Time Protocol (PTP)

or Network Time Protocol (NTP)


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Two Aspects of Synchronization - continued• Intraoffice Distribution of the timing signals to the receiving

Network Elements– All Network Elements capable of External Timing shall be timed from

the office BITS system– Most Network Elements require a Primary and Secondary timing lead

that originates from diverse cards in the BITS shelf and routes diversely to the receiving NE

– Next Generation TSG’s can provide:• DS1 timing reference• Composite Clock (64 kbps) timing reference• PTP Packet based reference via an electrical or optical SFP on the PTP card• NTP Packet based reference via an electrical or optical SFP on the NTP card• Some TSG’s can provide a 2.048kHz (E1) references


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Why are We Doing so Many Clock Installations• There are approximately 5400 locations (L-S, L-B, L-T wireline

locations) equipped with a BITS clock system and nearly all are or were equipped with MD’d sync equipment

• A Business Case was approved in mid 2005 and updated as additional companies were merged into the new AT&T to replace all the MD’d sync equipment (PRS sources as well as TSG’s)– Yearly Business Case funding has allowed for the cutover of the MD’d sync

equipment to the currently approved Next Generation sync equipment in about 150-200 locations per year with the larger locations being cutover first

– If yearly funding remains at the current rate, the number of office conversions will increase due to the replacement configurations being smaller – same money covers more locations


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Why are We Doing so Many Clock Installations - continued• The MD’d Sync equipment can include equipment labeled as

Symmetricom, Telecom Solutions, Austron-Datum or HP:– DCD-ST2 (Telecom Solutions now known as Symmetricom) TSG– DCD-400 (TSG)– DCD-523 (TSG)– TSG3800 (originally labeled DATUM now owned by Symmetricom) TSG– DCD-CIM (Telecom Solutions) TSG– NDSU/SDE (clock distributor)– DCD-LPR (Telecom Solutions/Symmetricom) GPS PRS– PRS-45 (Telecom Solutions/Symmetricom) Cesium PRS– HP 553310A (now Symmetricom) GPS PRS– TS2500 (Symmetricom) GPS PRS


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Why are We Doing so Many Clock Installations - continued• To avoid re-cabling every network element that is receiving a timing

reference from the MD’d clock equipment, the MD’d equipment wire wrap panel is maintained after the office conversion

• Maintaining the diversity to the network elements is a must after the conversion and the next generation clock port capacity is more dense (20 ports vs. 10 ports) so not only is physical diverse cable routing necessary but output card diversity in the new clock needs to be maintained.

• Cutover Y-cables (20 port to two 10 ports) are used to connect the new clock to the old clock wire wrap panels

• The Cut-over plans (maintaining diversity) are provided in the Sync Planners ER documents which should be provided in the Detail Specs and installation requirement and should be followed


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Engineering Considerations• For the MD’d sync cutover projects the ER document provided by

the Sync Planner is KEY and it needs to be followed during the engineering phase as well as the installation phase of the project and should be included in the Detail Spec

• Diversity, Diversity, Diversity– The BITS clock provides the timing reference to every critical element in

the office and as much diversity that can be obtained should be obtained• BDFB powering to the TSG fuse panel should be from diverse BDFB’s if available

or from separate A and B loads if diverse BDFB’s are not available or feasible to use

• Cabling from the BDFB to the sync bay fuse panel should be diverse• Output card selection within the TSG should be diverse (even/odd – old DCD

products, separate mated output groups – next gen TSG’s)• Cabling from the next gen TSG to the old TSG wire wrap panel• Cabling to network elements receiving timing references


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Engineering Considerations - continued

• Exceptions to Diversity– Allowable exceptions identified in the TP documents include but not

limited to:• Use of a single BDFB to provide power, but separate A & B loads should be

used• Cable runs on the same cable rack when diverse racking is not available

(minimum opposite sides of the cable rack) and the length of commonality should be minimized

• Use of a common cable hole between floors or rooms to run timing leads• Use of odd and even cards in old DCD TSG clocks – some regions assigned

output cards in a manner that will not allow for old/even diversity – in this situation separate cards must be used to provide primary/secondary timing leads to a network element


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Engineering Considerations - continued• Cabling from the BITS clock to the network elements is defined in the TP

documents as “Red” jacketed type 1175A single pair shielded cable. There are two exceptions to this requirement– Gray jacketed 1175A cable may be used in Legacy AT&T sites (due to the red color

designation being used for power leads)– Red jacketed 735C coaxial cable is used to connect 2048 MHz analog sync

references to Ericsson 3810 and 3820 RNC’s• “Red Books” used to display the sync assignments on site are required at all

locations that have on-site records maintained (L-S and some L-B). If records were maintained locally in some fashion, a “Red Book” will be required for new clock installations. The “Red Books” can be filled with computer print outs of the Tab/DB records and this is the standard for all sites that maintain on-site sync assignment records. The only sites that do not require “Red Books” are those sites where on-site records of sync assignments have never been kept. Examples; Mobility MTSO’s and some legacy BellSouth sites.


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Engineering Considerations - continued• Deployment of NTP or PTP in an already existing Symmetricom

TH5500 TSG will require the addition of a horizontal fiber tray under the front of the shelf to support the front fiber connection to the NTP or PTP SFP

• Sync output assignments must be updated in the mechanized record keeping systems (Tab/DB, SyncTrac, GEOLink, etc.) for new additions as well as the cutover projects


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Installation Considerations• Diversity, Diversity, Diversity• Streaker tests– The streaker tests will identify cabling continuity and polarity

between the output module slots and the wire wrap panels– Streaker cards have been designed for the Symmetricom TH5500,

SSU-2000 and FEI-Zyfer US5G TSG products and are available from TAG.

– Streaker tests are required for all new installations of the above noted TSG products and the results should be included with the job folder

• Correct labeling on the sync cabling showing to and from information


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Installation Considerations - continued• Symmetricom has established some “kits” that include the TSG

shelves, panels, mounting hardware as well as some plug-in units. These kits are ordered by the MEI and shipped to the OTV who is responsible for the plug-in units shipped with the kit. The OTV will be required to provide the plug-ins shipped with the kits for shelf turn up.

• The OTV needs to inventory received materials against the material list included in the ER document – some items are not accounted for or are not what was requested and discrepancies need to be corrected before the equipment is tested and turned up for service

• Timing cable shielding should be grounded at one end only – usually the BITS clock end


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Sync Related Waivers• Waivers must be submitted for all deviations from the AT&T

Standard Drawings, regardless of who requested the deviation– If the deviation is at the request of the Sync Planner and the

variance is not covered in the drawing notes that refer to the ER document, please note the name of the Sync Planner in the text of the waiver request to help facilitate expedient approval of the waiver request

• Make sure the most current version of the TP document is used when determining a waiver request is needed. Read the TP completely as many exceptions are already identified as acceptable (i.e. the use of the “Red Books”, odd/even card assignment in old DCD BITS clocks, etc.)


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Sync Related Waivers - continued• Be as explicit as possible when submitting a waiver request.

Provide pictures of the situation if possible• Contact Dave Overdorf, Sync Standards SME, at

[email protected], or 770-232-9183 if there are questions about the sync sections of the TPs, or an opinion is sought on the need for a waiver request.

• Don’t submit a waiver request for a violation or deviation that is found for a situation that is already in service or in place. Waiver requests are for new installations/work only

mailto:[email protected]


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Sync Assignment Recordkeeping• Depending on the region, the sync assignments are

maintained in different systems– Legacy SBC uses Tab/DB– Legacy BellSouth uses SyncTrac– Legacy AT&T uses GEOLink– Mobility uses a shared drive that requires permission to update

• OTV responsibilities– Tab/DB – The OTV is to update the assignments in Tab/DB for all

new assignments and for all cutover projects shall transfer data from the on-site records or the DCD Tab/DB records. Network element assignments requiring primary and secondary assignments must be made in diverse cards in the TSG. All notes identified in the ER document regarding Tab/DB should be followed.


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Sync Assignment Recordkeeping - continued• OTV responsibilities - continued– SyncTrac – a web based system that uses a simple GUI to retrieve and add

data. Records are stored by State and CO. Permissions are assigned dependent on the level needed, OTV’s are able to make assignments and add new systems. The OTV reviews the records for available spare ports and makes assignments in SyncTrac as required maintaining diversity of card assignments when required.

– GEOLink – Legacy AT&T sync assignments are made by AT&T personnel currently. The OTV must request the assignment ports via CSMHotline. The OTV will provide the Name, email address, Phone #, FIC location, Eq Type and Unit/Shelf # in the request. Once the assignment is made by AT&T personnel in GEOlink, an email will be sent to the OTV with the assignment information

– Mobility – The OTV requests any assignment through the MEI who issues an IWOS request to the NP&E Sync Planner. The assignments are maintained in the shared drive by the AT&T Sync Planner so the OTV has no responsibility in maintaining the Mobility sync assignments


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Summary• AT&T Sync standards are derived from Telcordia standards

documents• An Office Sync system includes the components of the BITS

system (PRS and TSG) as well as the connection of the timing references to the network elements in the office

• Sync BITS clock installations will not be slowing for the foreseeable future due to the extremely high number of MD’d sync elements currently working in the AT&T network

• Engineering and Installation considerations for sync jobs– Use the ER documents prepared by the Sync Planner– Diversity is the KEY– Avoid some common errors by using the streaker cards, labeling the

cable properly, maintaining diversity identified in the ER document


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Summary - continued

• Know when to submit a waiver request – when in doubt contact Dave Overdorf for assistance. Provide as much detail as possible when a waiver request is needed

• Some exceptions are already identified in the TP documents so a waiver request may not be required

• Sync assignment records vary by region – know your responsibilities for the installation work being done

• Sync provides the heartbeat to every critical element in an office, so do your part to keep it healthy


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Questions?

synchronization the “heartbeat” of the office

Documents

att marks

att core

att logo

att mobility practices

timing references

timing signal generators

timing outputs

core generic requirements