ProSoft Technology RadioLinx RLXIB-IHW-66 User Manual page 48

RLXIB-IHW-66 ♦ 802.11a, b, g
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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 RLXIB 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 RLXIB Radio flushes its Ethernet switch table 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.
Page 48 of 109
Radio Configuration / Diagnostic Utility
ProSoft Technology, Inc.
May 18, 2009
User Manual