ProSoft Technology RLX2-IHW User Manual page 99

considered a port. These BPDUs are the communications means to allow each RSTP
device in the network to make sure that the proper connections still exist.
In the following illustration, the port status dialog box is obtained by clicking on the Port
Status button on the main RLX2 web page. It shows a list of all ports and their state. In
this example, the RLX2 Radio has 4 RSTP "ports":

Ethernet port (1)

A port for its parent connection (2)

A port for each of its two child connections (11 and 12).
BPDUs are sent out the port at a rate called the "Hello Time". The accepted standard
value for this is 2 seconds. If a radio (or any other RSTP device) does not get a BPDU for
2 Hello Times, it assumes the RSTP device that had been there is no longer available. It
can then open an alternate path if one is available. This process is much like the STP
process. If other devices on the network are not operating in rapid spanning tree mode,
the radio will revert to normal spanning tree operation on a per-port basis.
RSTP provides a performance enhancement over STP operation. By comparison, the
radio using the STP algorithm would revert its port to the listening state, and then to the
learning state, before returning to the forwarding state. Each of these states takes at
least 15 seconds, during which the STP devices are listening for BPDUs to re-negotiate
the network topology. The advantage of using the RSTP functionality is that is uses
active handshaking between adjacent RSTP devices to re-negotiate the network
topology. This process takes one to two seconds.
Each RLX2 Radio contains a switch table, which tells it how to forward Ethernet packets
to get them to their proper destination. When the network topology changes, the RLX2
Radio the Ethernet switch table is flushed immediately. This allows it to pass traffic
immediately over the new network topology and learn the configuration in the process.
Until the learning is complete, the packets are broadcast to their destination. As each
packet is seen and the switch table rebuilds, the radios return to directing packets to
their destinations.
ProSoft Technology, Inc.
November 3, 2016
RLX2 Industrial Hotspot Series
Page 99 of 208