IEEE1588-v2

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The introduction about IEEE1588v2

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IEEE1588-v2

  1. 1. IEEE1588-v2 Introduction
  2. 2. AGENDA • • • • • • Time Synchronization IEEE1588-2002 IEEE1588-2008 Best Master Clock Algorithm Message Transport Implementation
  3. 3. Time Synchronization • NTP/SNTP – Application Layer – Not accuracies(10~100 ms) • GPS – Expensive • Precision Time Protocol (PTP) – – – – Local area network sub-microsecond (μs) Measurement and control system Master-slave architecture
  4. 4. IEEE1588-2002 Clock Type • Ordinary Clock (OC) – a single PTP port – end nodes • Boundary Clock (BC) – multiple PTP port – sync from one network to another – switch & router • Grandmaster Clock (GMC) – stable & accuracies • GPS or atomic clock – Best Master Clock (BMC)  define GMC – One GMC in local network
  5. 5. IEEE1588-2002 Clock Type GPS GMC S M S BC M S OC OC M S BC M S OC
  6. 6. IEEE1588-2002 Message type • Sync (Offset) – Master to Slave – Timestamp (predict send out time) – Send every 2 sec • Follow up (Offset) – Master to Slave – Contain send sync timestamp • Delay Request (Delay) – Slave to Master – Send every 4 ~ 60 sec • Delay Response (Delay) – Master to Slave
  7. 7. Synchronizing with Master and Slave • Synchronizing – Delay + Offset = t2-t1 – Delay - Offset = t4-t3 – Delay • ((t2-t1) + (t4-t3)) / 2 – Offset • ((t2-t1) - (t4-t3)) / 2 • Precision – Software (ms) – Software + Hardware (μs)
  8. 8. Synchronizing with Local Clock • Drift – Frequency is difference between master & slave clock • Solution – Time stamp in hardware – Follow-up message to adjust the frequency
  9. 9. IEEE1588-2008 Clock and Message Type • Transparent Clock (TC) – Convey PTP message – End-to-End (E2E) Transparent Clock • forwards all messages on the network • Add the switch “transit time” to “correction field” on SYNC & DELAY_REQUEST message • No “propagation delay” – Peer-to-Peer (P2P) Transparent Clock • Add “propagation delay” (upstream link delay) • Add “transit time” + “upstream link delay” to “correction field” • Message Type – Pdelay_Req – Pdelay_Resp – Pdelay_Resp_Follow_Up
  10. 10. IEEE1588-2008 Clock and Message Type Sunc, Follow _Up, Delay_R eq, Delay_Re sp GPS GMC M S E2E TC M Pdelay_Req, Pdelay_Resp, Pdelay_Resq _Follow_Up GPS GMC S M S P2P TC OC S OC S M S OC OC
  11. 11. Synchronizing with P2P TC • Synchronizing – Delay + Offset = t2-t1 – Delay - Offset = t4-t3 – Delay • ((t2-t1) + (t4-t3)) / 2 – Offset • ((t2-t1) - (t4-t3)) / 2
  12. 12. Best Master Clock Algorithm (BMC) • Select the best candidate clock – Identifier : MAC address – Quality : timing deviation (GPS is highest quality) • 1588-2002 : data field stratum • 1588-2002 : clock accuracy & clock class – Priority : help select a grandmaster • 1588-2002 : boolean • 1588-2008 : two 8-bit – Variance
  13. 13. Message Transport • Ethernet layer – EtherType : 0x88F7 – Multicast address : 01:1B:19:00:00:00 – Peer Delay address[2008] : 01:80:C2:00:00:0E • IP layer – Multicast address : 224.0.1.129 & FF0x::181 – Peer Delay address[2008] : 224.0.0.107 & FF02::6B • UDP – Event Message : 319 • Sync, Delay_Req, Pdelay_Req, Pdelay_Resp – General Message : 320 • Follow_Up, Delay_Resp, Pdelay_Resp_Follow_Up
  14. 14. Implementation • Software on linux – PTPd (BSD lisence) • IEEE1588-2002, 2008 (OC) • HW:Intel 82576 or 82580 – Ptpv2d (GPL) • IEEE1588-2002, 2008 and IEEE802.1AS (OC) • HW:Freescale MPC831x family – Ptp4l (GPL) • IEEE1588-2002, 2008 and IEEE802.1AS (BC, OC) – Linux PTP Hardware Clock (linux kernel 3.0) – SO_TIMESTAMPING (linux kernel 2.6.30) • HW:Freescale eTSEC gianfar, National Semiconductor DP83640, Intel IXP465

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