Figure 1. Flowchart for Missing Delay_Response Messages
The upstream master clock should respond to every Delay_Request message with a corresponding Delay_Response message having the same sequence ID value.
The requestingSourcePortidentity and requestingSourcePortID values in the response message must also match the clockIdentity and sourcePortID values in the request message - otherwise the response message will be ignored.
Missing one or two Delay_Response messages should not affect synchronization accuracy or precision, but missing many of these messages or missing consecutive sequence IDs might harm synchronization of the clocks.