Add a new subclause 12.29.2, titled "Representation of times", with the following text:
"The time values of 12.29.1 (e.g. AdminBaseTime) shall be represented at the point where
a frame passes the reference plane marking the boundary between the network media and PHY
(i.e. on-the-wire time point).
Figure 12-6 shows two points in time for scheduled traffic. The time of gate open/close
described in subclause 8.6.8.4 is used for transmission selection, and that point in time
exists internal to the Bridge (i.e. above MAC and PHY). A delay exists between this
internal time point and the time of transmit on-the-wire. For example, if transition of
a gate from closed to open immediately results in selection of a frame for transmission,
there will be a delay from that internal time of transmission selection to the start of the
frame on-the-wire. The internal time point will have variance (min/max), and the delay to
the on-the-wire time point will also have variance.
Since the Bridge contains the information needed in order to compute the min/max delay
from the internal time point to the on-the-wire time point, the Bridge is responsible
for performing the adjustments in order to represent the managed objects as on-the-wire
time.
NOTE: As an example, consider an IEEE Std 802.3 Port configured to transmit a single
traffic class with known frame lengths, and the managed objects are configured with
a cycle of open for one millisecond, then closed for one millisecond. If a continuous
burst of frames is transmitted through the Bridge to the Port, no symbol of a frame
can transmit from the PHY during the closed window (i.e. from start of Preable through
end of Frame Check Sequence)."
Insert a new Figure 12-6, titled "Points in time for scheduled traffic":
+------------------ -----------------------+
| Transmission selection for |
| scheduled traffic (8.6.8.4) | <- internal time point
| |
+---------------(EISS)---------------------+
| |
| Subclause 6.9 |
| |
+---------------(ISS)----------------------+
| |
| Subclause 8.5.1 |
| |
+---------------(ISS)----------------------+
| |
| MAC |
| |