Ieee 1588 ptp


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IEEE Standard 1588 Precision Timing Protocol

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Ieee 1588 ptp

  1. 1. IEEE Standard 1588 Precision Timing Protocol - PTP 許勝倉@NCU 2008/March/08
  2. 2. Why Timing Sync• Time Division Multiplexing - TDM• Circuit Emulation over Packet - CESoP• Time Division Multiplexing - TDMoIP• Wireless Backhaul• Building Integrated Timing Supplies - BITS
  3. 3. Clock Source to Sync• Global Positioning System- GPS• Network Time Protocol - NTP• Adaptive clock Recovery - ACR• Precision Timing Protocol - PTP• Building Integrated Timing Supplies - BITS• Clock from Loop• Atom Clock Source
  4. 4. Timing RequirementsT1 Standard, Maximum time variation • 8.4us over 900 seconds • 18us over 24 hoursT1 Standard, Maximum time Interval error at sync • 1us over 2000 seconds • 2us over 100000 secondsMobile station frequency accuracy • 50 Parts Per Billion (ppb)
  5. 5. Timing protocols problems• ACR - Expensive oscillate source• GPS - Weak signal indoor• NTP - Not meet 50ppb• BITS - Price too high• Loop Clock - Can’t over Packet Network• Atom Clock Source - Price very high
  6. 6. Synchronizing TDM Internet BITS/SSU PTP Master T1/E1 Access NodePSTN DS1 ADSL PSTN Switch PTP Slave Ethernet
  7. 7. How PTP workPreamble SFD SRC MAC DST MAC Length/Type Data CRC 10101011 IP Header UDP Header PTP Message
  8. 8. Clock Network Ordinary Clock (Best Master) Master Clock Source Master Master Master Slave Boundary Clock (Ethernet Switch)Salve Salve Salve Master Master Master Salve Boundary Clock (Ethernet Switch) Salve Salve Ordinary Clock
  9. 9. PTP Messages Type Message ValueSYNC 0DELAY REQUEST 1FOLLOW UP 2DELAY RESPONSE 3MANAGEMENT 4Reserved 5-255
  10. 10. PTP in Software• PTP define in IANA Multicast address• Use UDP port 319 for Event message• Use UDP port 320 for general message• Packet size less than 300 bytes• Header length less than 40 bytes
  11. 11. 0x0800 SRC IP UDP SYNC Port 319 PTP protocol Message Origin TimeStemp in Origin TimeStemp in PTP vsersion Type Seconds Nano Seconds DELAY REQUEST Port 319 PTP protocol Message Origin TimeStemp in Origin TimeStemp in Estimated Master Estimated Master PTP vsersion Type Seconds Nano Seconds Variance Drift FOLLOW UP Port 320 PTP protocol Message Origin TimeStemp in Origin TimeStemp in PTP vsersion Type Seconds Nano Seconds DELAY RESPONSE Port 320 PTP protocol Message Delay Receipt in Delay Receipt in PTP vsersion Type seconds Nano Seconds
  12. 12. T1 Sync T2 Follow-up T3 Delay request T4 Delay response Sync T1 Follow-up Sync Follow-upMaster Network Slave
  13. 13. Offset T1 Sync Delay T2 Follow-up T3 Delay Delay request Offset T4 Delay responseMaster Slave
  14. 14. Delay and Jitter Master Slave PTP PTP Application UDP UDP IP IPDelay and Jitter Protocol Stack Driver Driver Driver MAC MAC MII PHY PHY Network Delay and Jitter Network
  15. 15. Hardware for Time StampMicroprocessor Ethernet MAC Ethernet PHY LAN/WAN Time Stamping Unit (TSU) Precision time stamping in hardware
  16. 16. Open Source PTPD
  17. 17. Conclusion• PTP require addition hardware to reduce processor and software’s delay and jitter for more precision clock.• PTP is cheaper than Atom clock source.• PTP could meet 50 ppb requirement of TDM network.• With PTP, TDM could over Packet Switch Network without sync clock loss.
  18. 18. Reference• IEEE Standard 1588-2002 Version 2• IEEE 1588 Precision Timing Protocol, Jeremy Bennington, Symmetricom• High Precision clock Synchronization according to IEEE 1588 Implementation and Performance Issue, Hans Weibel, Zurich Univ.• PTPD for Linux• IEEE Standard 802.1AS Draft