Siemens SIMATIC Power Line Booster Operating Instructions Manual page 97

Buffer
The Traffic Manager has various buffers to cache the incoming Ethernet frames until they
can be packaged and send in a container. Buffers that are not in use do not have an effect
on the bandwidth of the PLB communication. That is why a parameter adaptation is not
required in case of change.
The buffers differ in the priority with which they are emptied and sent.
The Traffic Manager can only transmit a specific number of bytes in each poll cycle (query of
a master and a slave responding to it). The number of bytes is configured with the "Container
size" (see Communication (Page 98)). If a buffer overflow occurs, this is shown in the log
(Page 85).
● The data of the "Prio 1 buffer" are sent first. Here the cyclical data is buffered. The
selected default is configured so that there is sufficient space for the cyclical data of the
PROFINET devices connected to the PLB in typical applications. If more PROFINET data
is to be transmitted via powerline than is set in the default configuration, the size of the
Prio 1 buffer must be increased.
● The "Prio 2 buffer" is reserved for PROFINET alarms. The selected default is configured
so that there is sufficient space for any alarms that may occur in the PROFINET devices
connected to the PLB.
● The "Prio 3 buffer" is for "User-prioritized data". If this buffer is activated, the Unicast
frames are buffered in the ports specified for TCP/UDP in User priority (Page 99). The
saved frames are sent directly after the PROFINET data (Prio 1 and Prio 2) if there is still
space in the container.
● All Unicast data that are not Prio 1 to Prio 3 are buffered in the "Prio 4 buffer" and sent (if
there is still space in the container).
● The "Broadcast buffer" is the buffer for all broadcast and multicast data. Broadcast
frames are not sent until the data of Prio 1 to Prio 4 class have been sent and when there
is sufficient space in the container.
● All frames that cannot be assigned to an Ethernet station behind a slave are saved in the
buffer "Frames for unknown stations" (only in the PLB master). For PDS applications,
these are frames that are created due to the redundant transfer via PRP (Page 39), for
example, and that can only be sent in the PRP section in which the vehicle is currently
located. You can use the checkmarks to suppress this buffer and thus its transfer.
Power Line Booster
Operating Instructions, 11/2019, A5E36203125A-AG
System configuration and system status (web interface)
6.4 Powerline
97