User`s manual

CLARION M10 SERIES STRUCTURE
M10 SERIES USER’S MANUAL PAGE 10
Prior to the re-transmission, the M10 recognizes and memorizes the source
MAC address of an Ethernet device connected to the M10 through the
MAU port. The Download occurs only when the M10 recognizes complete
matching of the memorized source MAC address and destination MAC
address written in a received radio frame. Once the M10 memorizes the
source MAC address, no update of the source MAC address is performed in
the M10 unless the power turns off. That is, applications that lead to
frequent changing of the source MAC address of the Ethernet frame
coming from plural Ethernet devices through the MAU interface are not
suitable for making the re-transmission effective. In case of such
applications, we recommend the M10 be configured without re-
transmission.
The re-transmission protocol is based on the recognition of
acknowledgment generated by a M10 that received a radio data frame from
another. A radio frame that carries the acknowledgment is called an Ack-
frame and effects only the RF MAC level protocol. Contents of the Ack-
frame never appear at the MAU port. The Ack-frame is transmitted
immediately after the completion of receiving.
The re-transmission is not available for Broadcast-frames because no
Ack-frame can be transmitted for Broadcast-frames (it contains a
destination address of all 1 bits).
Figure 2.3.5 shows two different causes of re-transmission. One is missing
of Ack-frame (Ack #2) and another is missing data-frame (Data #3). In
each case, the M10 #1 recognizes no return of the Ack-frame from M10 #2,
then M10 #1 initiates re-transmission. The M10 #1 recognizes that a
duplicate frame has been received, then M10 #1 filters it out (i.e. download
does not occur). This function is called Duplicate filter.
The duplicate filter is functional only in case a single Ethernet device is
connected to the M10. The function will be updated in the future to make
it available for multiple Ethernet devices.
Duplicate frames that the M10 has not filtered out will be removed by a
function of NOS (Network Operating System). The number of re-
transmissions is limited to seven (i.e. eight transmission totally).
Accordingly, if no transmission of a frame was successful by the seventh
re-transmission, the successful transmission will depend on the another re-
transmission function provided by the NOS protocol.