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Page 22

DXD/PTP/GPS User Manual (rev 2.10) 

16. Guidelines for configuring PTP (Precision Time Protocol) 

Only a few years ago, setting up a network was not a task most audio or video engineers were concerned with. This was the 
responsibility of the IT department. Nowadays, it has become an important part of more and more installations and, as we 
move towards A/V over IP, careful advance planning of the network and proper configuration is necessary, demanding a new 
set of skills. 

Although configuring an A/V network includes many settings that do not concern the DXD-8, PTP is a complex standard and a 
good understanding of network technology is required. The best source of information for PTP is the IEEE 1588 standard itself 
available here: https://standards.ieee.org/standard/1588-2019.html. There are also many publications available from 
different organizations such as SMPTE and AES with best practices recommendations. 

PTP’s role is to synchronize the real-time clocks of the different nodes on a network but it does not make the network itself 
synchronous. The traditional master/slave architecture is also very different when dealing with PTP thanks to the BMCA. 

The list below only includes some very basic PTP requirements and recommendations and is not meant to be a comprehensive 
check list. 

16.1 REQUIREMENTS 

PTP Domain

: Devices that need to be synchronized together via PTP must be part of the same domain. Be sure the PTP 

domain is set properly on your DXD as messages with any other domain number will be ignored. 
(menu 5.2). 

Ports Timing

: per IEEE 1588, all devices on a PTP domain must have the same value set for these ports timing: 

-

Announce Interval 

-

Announce Receipt Timeout 

(menu 5.4). 

Delay Mechanism

: Two different delay mechanisms are available: E2E and P2P. End-to End mechanism is more 

versatile because it can handle ordinary switches and routers but in large networks with lots of slaves, the master clock 
and the network could be heavily burdened with large amount of delay request and response messages. With Peer–to-
Peer mechanism, delay is established between neighbors only. 

-

P2P requires all of the devices to be PTP-aware as ordinary switches will not respond to peer-delay messages. 

-

All the 1588 nodes on the same messaging path are required to use the same delay mechanism. 

(menu 5.3). 

16.2 RECOMMENDATIONS 

PTP Profile

: It is recommended to use the same profile for all units in any particular domain.  Failure to do so can lead 

to unexpected results. 
(menu 5.3). 

Priority Fields

: If the DXD-8 is your preferred master clock, the simplest way to make it the Grandmaster is to set the Priority 1 

field low enough to win the BMCA. However, it is also recommended that all candidate GMs would have the same Priority 1 
value to avoid causing hierarchy issues as the Priority 1 field overrides any clock quality changes in the GM. 
(menu 5.2). 

Keep in mind that, with PTP, the BMCA always determines which device becomes Grandmaster. As conditions change 
(loss of GPS for example), another Grandmaster could be selected, changing the state of the DXD-8 port. But this would 
only be true if, as recommended above, all candidate GMs would have the same Priority 1 value. 

Содержание DXD/GPS

Страница 1: ...k DXD OCXO OCXO option for the DXD Universal Clock Operations manual Version 2 10 January 2021 All materials herein Brainstorm Electronics Inc Brainstorm Electronics reserves the right to change or mo...

Страница 2: ...6 GPS Menus 8 6 1 SATELLITES SELECTION MENU 6 1 8 6 2 GPS SETTINGS MENU 6 2 8 6 3 ADVANCED GPS SETTINGS MENU 6 3 8 7 DXD OCXO 9 8 Time of Day 9 8 1 RTC Real Time Clock 10 8 2 Time Jam 10 8 2 1 TIME JA...

Страница 3: ...9 15 Typical PTP use 20 15 1 HYBRID SYNC GENERATOR ACCEPTING MULTIPLE REFERENCES 20 15 2 DISTRIBUTED PTP VS INDIVIDUAL GRANDMASTERS WITH GNSS 21 16 Guidelines for con fi guring PTP Precision Time Prot...

Страница 4: ...a series of 4 numbers separated by periods This key is only valid for the DXD 8 with the serial number used when you placed the order Note that PTP is optional on the DXD 8 only A feature key is not r...

Страница 5: ...ng LOCAL REF WHEN GM When PTP Mode is selected if GPS is available this fields enables GPS to be set as the reference when the DXD 8 is the Grandmaster Enabling this field will announce the DXD 8 as G...

Страница 6: ...a quick set up This menu gives you the option to set the timing values to the pro fi le default values 4 4 PORT TIMING MENU 5 4 Announce Interval 3 to 4 1 8sec 16sec Sets the rate at which the master...

Страница 7: ...in your DXD an antenna will need to be connected to the receiver s SMA connector an antenna is not included with the DXD GPS The cable needs an SMA Male connector on the DXD side Ideally the antenna s...

Страница 8: ...sideration as it can not only impact the signal strength but also cause a delay in the signal Under typical conditions however the expected cable delay is negligible in the nanoseconds range The follo...

Страница 9: ...e reference sources include time and rate information GPS and PTP for example carry precise time and date information as well as frequency However traditional reference signals such as video sync or w...

Страница 10: ...nd wanting all of the cross frame outputs 25 etc to be in correct phase and epoch as well as wordclocks and AES In a primarily legacy application this is the way to increase the number of legacy outpu...

Страница 11: ...to use Local Time instead while others may even prefer different standards for different times Be aware that even though the time source may give Time Of Day it may not correspond to the time indicate...

Страница 12: ...on Jan 1 1970 This process occurs everyday at the same time as set in the DAILY JAM TIME fi eld Daily Jam Time The value entered in the DAILY JAM TIME field is the amount of time after midnight local...

Страница 13: ...to LOCKED GRANDMASTER In case the DXD is or becomes a PTP Salve when locked it changes to LOCKED PTP SLAVE Note that if another source was selected in the reference menu such as Video Sync and the DXD...

Страница 14: ...lock and the Grandmaster in sec Additional times may appear on this page such as Time Code based on the installed options 11 2 2 GPS RECEIVER STATUS PAGE The GPS RECEIVER status page displays the foll...

Страница 15: ...as the ability to clock to a non Dante PTP v2 clock AVB Audio Video Bridging is a set of IEEE standards that facilitate the transport of high performance audio and video on a LAN One of those standard...

Страница 16: ...suited clock is found it will become the Grandmaster 12 6 SYNCHRONIZATION There are several different PTP messages used during synchronization sequenced as follows 1 The grandmaster sends a Sync messa...

Страница 17: ...clocks on a single PTP communication path must use the same method to measure the time delay 12 8 TYPES OF CLOCKS IEEE 1588 de fi nes three different types of clocks Ordinary Clock OC Boundary Clock...

Страница 18: ...ate of the port can change The BMCA determines what unit becomes the Grandmaster If the current Grandmaster disappears or looses GPS another Grandmaster is selected For more on the Grandmaster selecti...

Страница 19: ...it has been set by the operator 14 1 JUMP TO RELOCK When the time difference detected between the external PTP GM and the DXD System Time is above the Jump Threshold value the DXD will jump to the ne...

Страница 20: ...t all equipment could be kept perfectly synchronized But for added fl exibility the DXD s can also be set up to lock to any legacy sync or to PTP as illustrated below These choices are available in th...

Страница 21: ...TP slaves to an external Grandmaster in the second illustration the DXD 8 s are all Grandmaster for their networks and each is locked to GNSS This second solution is particularly useful when distances...

Страница 22: ...ith any other domain number will be ignored menu 5 2 Ports Timing per IEEE 1588 all devices on a PTP domain must have the same value set for these ports timing Announce Interval Announce Receipt Timeo...

Страница 23: ...GMPv2 On larger networks a router is required to manage multicast group membership Switches that support IGMP snooping are also recommended 17 Troubleshooting Error Warning Messages 17 1 PTP NO PORT W...

Страница 24: ...3 Menu 5 1 If PTP was selected TIME JAM BNC INPUT will automatically show in menu 5 1 in blue blue status information The words Time Jam will also appear on the REFERENCE line at the bottom of the ma...

Страница 25: ...the ribbon cable to J23 the GPS connector on the motherboard B J23 is the designator number on both DXD 8 and DXD 16 PCB As always with ribbon cables make sure the connectors are properly oriented do...

Страница 26: ...Including cable loss Low Gain mode FLNA High 3 For best jammer resistance and lower power consumption use 10 dB lower gain than the max gain 18 3 2 RECOMMENDED PASSIVE ANTENNA 1 High Gain mode FLNA Op...

Страница 27: ...TIMEOUT 3 announce intervals SYNC INTERVAL 1 sec log 0 MINIMUM DELAY REQUEST INTERVAL 1 sync interval GLONASS Yes GALLILEO No QZSS LIC A Yes SBAS QZSS LIS SBAS DIF FIX ANTENNA CABLE DELAY 0 ANTENNA H...

Страница 28: ...Page 28 DXD PTP GPS User Manual rev 2 10...

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