Allied Telesis AT-S63 - Manual (Page 279)

AT-S63 Management Software Features Guide
Section V: Spanning Tree Protocols 279
Mixed STP and RSTP Networks
RSTP IEEE 802.1w is fully compliant with STP IEEE 802.1d. A network
can have both protocols. If both RSTP and STP are present in a network,
they operate together to create a single spanning tree domain. Given this,
if you decide to activate spanning tree on the AT-9400 Switch, there is no
reason not to use RSTP, even if the other switches are running STP. The
switch combines its RSTP with the STP on the other switches by
monitoring the traffic on the ports for BPDU packets. Ports that receive
RSTP BPDU packets operate in RSTP mode while ports receiving STP
BPDU packets operate in STP mode.