I had a query in PTP Transparent Clock(TC), Please consider the below picture for my question.

I will try to express my question with the help of a real world example

Say, two places Place_A <-----|Toll_Plaza|------> Place_B

Assume time taken to travel from Place_A to Place_B is x minutes (which includes the time taken at Toll_Plaza).

Just imagine the same thing happening with the Transparent clock in PTP Synchronization, a TC just calculates the residence taken at a device and modifies the correction field and forwards the packet to the other device.

It anyways time taken will be same irrespective of TC existence from a Peer to Peer.

How come it helps in having right accuracy? What is the real purpose in introducing a TC in IEEE 1588v2?

Any explanation will be helpful and welcome. Thanks in Advance !!!

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  • Adding another question : Is there any way to know just by seeing the packet capture, the clock which it is configured for? – user60007 Jan 8 '20 at 6:38
  • I would assume that other clock types won't have the same message IDs as transparent clocks. The transit time is calculated by the corresponding messages: The measured transit time of a SYNC message is added to the correction field of the corresponding FOLLOW_UP message. The measured transit time of a DELAY_REQUEST message is added to the correction field of the corresponding DELAY_RESPONSE message. – Bobby Voychin Jan 8 '20 at 12:31
  • Did any answer help you? If so, you should accept the answer so that the question doesn't keep popping up forever, looking for an answer. Alternatively, you can post and accept your own answer. – Ron Maupin Dec 17 '20 at 14:58

PTP with Transparent Clock is used to synchronize the clock of a network client with a server (similar to NTP). However, PTP is mainly used in LANs, with much higher precision than NTP (usually 10's of microseconds to 10's of nanoseconds).

The protocol has two dependencies:

  • UDP: Typically, PTP uses UDP as its transport protocol (although other transport protocols are possible). The well known UDP ports for PTP traffic are 319 (Event Message) and 320 (General Message).

  • Ethernet: Starting with IEEE1588 Version2, a native Layer2 Ethernet implementation was designed. PTP can use Ethernet as its transport protocol. The well known Ethernet type for PTP traffic is 0x88F7.

Example Traffic:

Sync Message

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Follow-up Message:

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Delay Request Message

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Delay Response Message

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