[EFM-P2MP] Definition of Timestamp in MPCP messages
Folks,
Last night on the Conference call there was a question concerning the
"meaning" of timestamps in MPCP messages. For example, does the
timestamp mean that this is the time that the first byte of the message
is passed on to lower layers, or is it the time the first byte of the
timestamp is passed to lower layers. I thought I would begin the
discussion by asking some of the EPON developers here. They gave me the
following answer to the question:
"In our current implementation, the timestamp is the status of the local
counter at the insertion time which is a couple of cycles before the
timestamp enters the 8b10b encoder. The 8b10b encoder will then
introduce further latency that becomes part of the roundtrip delay.
I would prefer a definition of the timestamp as the status of the local
clock at the time of sampling, where the delay between time of sampling
and PMD transmission time of the message (or of the timestamp) is
constant for any EPON compatible olt or onu unit."
Their feeling was that either definition would work, as long as it is
specified in the standard so all will implement consistently...
cheers,
bobg