...1 What?...2 Why?...3 How? ( ) IEEE / 23

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康彪乌
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1 .... IEEE ( ) IEEE / 23

2 ...1 What?...2 Why?...3 How? ( ) IEEE / 23

3 ...1 What?...2 Why?...3 How? ( ) IEEE / 23

4 IEEE 1588 ( ) IEEE / 23

5 IEEE 1588 IEEE 1588 ( ) IEEE / 23

6 IEEE 1588 IEEE 1588 IEEE 1588 ( ) IEEE / 23

7 ...1 What?...2 Why?...3 How? ( ) IEEE / 23

8 : SNTP RFC ms-150ms NTP RFC us-50ms PTP IEEE 1588 ( ) IEEE / 23

9 1588 ( ) IEEE / 23

10 1588 <1us ( ) IEEE / 23

11 1588 <1us GPS IRIG-B ( ) IEEE / 23

12 1588 <1us GPS IRIG-B BMC ( ) IEEE / 23

13 1588 <1us GPS IRIG-B BMC ( ) IEEE / 23

14 1588 <1us GPS IRIG-B BMC GPS ( ) IEEE / 23

15 ...1 What?...2 Why?...3 How? ( ) IEEE / 23

16 IEEE 1588 v2 : PTP Ordinary/Slave Clock Grandmaster Clock Boundary Clock Transparent Clock BMC sync Message follow-up Message announce message one step operation two step operation delay-req/resp msg pdelay-req/resp msg point to point (P2P) 1588 OC OC MC MC->OC MC(s) advertise capabilities to enable BMC On the fly manipulation of 1588 packets by MC and TC ( ) IEEE / 23

17 IEEE 1588 ( ) IEEE / 23

18 ( ) IEEE / 23

19 ( ) IEEE / 23

20 Qos ( ) IEEE / 23

21 Qos 100Mbps 64 5us ( ) IEEE / 23

22 Qos 100Mbps 64 5us 100Mbps us ( ) IEEE / 23

23 Qos 100Mbps 64 5us 100Mbps us OC ( ) IEEE / 23

24 Qos 100Mbps 64 5us 100Mbps us OC 1588 v ( ) IEEE / 23

25 ( ) IEEE / 23

26 Estimated Send Time (100) Precise Send Time (101) B Precise Receive Time (108) Master Clock PTP Appl. G/MII t 0 SYNC(100??) FOLLOW_UP(101!) DELAY_REQ t 3 t 2 DELAY_RESP(108) Slave Clock G/MII PTP Appl. t 1 A Precise Receive Time (106) Offset Computation Precise Send Time (111) Key Equations: A = t 1 t 0 = Delay + Offset B = t 3 -t 2 = Delay Offset Delay = (A+B) / 2 Offset = (A-B) / 2 Example: A = = 5 B = = -3 Delay = (5-3) / 2 = 1 Offset = (5+3) / 2 = 4 IEEE 1588 Synchronization Message Sequence 116 UDP port 319: Sync and Delay_Req UDP port 320: Follow_up, Delay_Resp, and Mgmt ( ) IEEE / 23

27 ( ) IEEE / 23

28 End-to-End Master Transparent Clock Slave T1 Sync Follow_up Sync Follow_up T2 Delay_Req T3 Delay_Req T4 Delay_Resp Delay_Resp End to End residence time correction model Delay request-response path length measurement ( ) IEEE / 23

29 Peer-to-Peer Master Transparent Clock Slave T1 Sync Follow_up Sync Follow_up T2 T4 T5 PDelay_Req S-TC PDelay_Resp TC-S T3 T6 PDelay_Req TC-M PDelay_Resp_Follow_Up TC-S PDelay_Resp M-TC PDelay_Resp_Follow_Up M-TC Peer to Peer residence time and link delay correction model S-TC : Slave to Transparent Clock M-TC : Master to Transparent Clock Peer delay link measurement ( ) IEEE / 23

30 Peer-to-Peer Residence time = t r1 Residence time = t r2 GM Ordinary Clock-0 P2P TC Propagation time = t p0 S Ordinary Clock-1 P2P TC Propagation time = t p1 S Ordinary Clock-2 P2P TC Link 1 Link 2 Link 3 Propagation time = t p2 S Ordinary Clock-3 P2P TC N 1 Sync correction field + Follow Up correction field = (t ri + t pi ) (1) N 1 N total propagation plus residence time = t ri + t pi (2) i=1 i=1 i=1 slave offset = t 2 t 1 total propagation plus residence time (3) ( ) IEEE / 23

31 E2E vs. P2P + Scale poorly with the number of devices (master sees all slaves) + Good for linear systems (eliminates cascaded servos) Can introduce 1:N topology + + Scale well with the number of devices + Good for linear systems (large number of daisy chained clocks) + Rapid recovery with changes in network topology Cannot resolve 1:N introduced by ordinary switches, wireless, or end-to-end TC Must maintain per port path length state and measuring mechanisms. Only used in homogeneous P2P systems. Requires a boundary clock at the edges. 6 (vs. 4) measurements ( ) IEEE / 23

32 IEEE 1588 Now, it's 9:28! Milliseconds of delay and variation introduced by protocol stack Master Clock PTP UDP IP MAC PHY Variable delay introduced by the Network due to the topology: Hundreds of nanoseconds to microseconds for repeaters & switches Milliseconds for routers Network Slave Clock PTP UDP IP MAC PHY OK, thanks 9:28! Milliseconds of delay and variation introduced by protocol stack PTP Packet Now it's 9:28 Software Timestamp Implementation ( ) IEEE / 23

33 IEEE 1588 Master Clock Slave Clock Now, it's PTP PTP OK, thanks 9:28! UDP UDP IP IP MAC MAC PHY Network PHY 9:28! PTP Packet Now it's 9:28 Hardware Timestamp Implementation ( ) IEEE / 23

34 PTP Message Header PTP Message Header Bits transportspecific messagetype reserved versionptp messagelength domainnumber reserved flagfield correctionfield reserved sourceportidentity sequenceid controlfield logmessageinterval 0 Octets Offset ( ) IEEE / 23

35 : Message Type Message Type Message Class Value Sync Event 0 Delay Req Event 1 Pdelay Req Event 2 Pdelay Resp Event 3 Reserved 4 7 Follow Up General 8 Delay Resp General 9 Pdelay Resp Follow Up General A Announce General B Signaling General C Management General D Reserved E F ( ) IEEE / 23

36 Value of flagfield : Value of flagfield Octet Bit Message types Name 0 0 Announce,Sync,Follow Up,Delay Respon alternatemasterflag ( ) IEEE / 23

37 Announce Message Annouce Message Bits Octets Offset header 34 0 origintimestamp currentutcoffset 2 46 reserved 1 47 grandmasterpriority grandmasterclockquality 4 40 grandmasterpriority grandmasteridentity 8 53 stepsremoved 2 61 timesource 1 63 ( ) IEEE / 23

38 Sync and Delay Req messages Sync and Delay_ReqmessagesMessage Bits Octets Offset header 34 0 origintimestamp ( ) IEEE / 23

39 Thank you! Author: Address: Zheng Xiao-jun No.11 Phoenix Road of Jiangning Development Zone Guodian Nanjing Automation CO.,LTD Nanjing, , China ( ) IEEE / 23

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