According to Table 157, the Timestamp parameter is described as:
"The time the Client sent the request."

But what is the TRUE purpose of this parameter?

Should the Server use this information to determine how old/stale a request is from a Client? (likewise when a Client receives a response from a Server)

Even if time-synchronization is not in place and a Client sent a date that was 1-year old, what should the Server do?

Should the Server care about this parameter? if not, then do we need this parameter?

Obviously some clarification is needed, some thoughts:

1.) Server can be configured with a user-definable setting to determine the age of a request (based on this parameter) that should be allowed. Messages with a timestamp outside of this tolerance are rejected.

2.) Server merely uses the setting as part of diagnostics capturing/logging, i.e. the Client issued the call at {client time} which was received at {server time} etc.

3.) Specify that the parameter is optional, but when implemented it should do... and when not implemented then...