According to the documentation:
BPDU are sent every hello-time, and not simply relayed anymore. With 802.1D, a non-root bridge only generates BPDUs when it receives one on the root port. In fact, a bridge relays BPDUs more than it actually generates them. This is not the case with 802.1w. A bridge now sends a BPDU with its current information every seconds (2 by default), even if it does not receive any from the root bridge.
But what about the BPDU exchange between two non-root RSTP switches?
Let's say we have a 3 switch star topology like this:
.
Will the segment between SW2 and SW3 exchange BPDUs every 2 seconds?
Are the non-root bridges going to send BPDUs to the root bridge in RSTP?
Best Answer
In RSTP when the topology is synchronized, the non-root switches will not exchange BPDUs unless one of the links change. If that happens, a new synchronization process starts.
The synchronization process is as follows:
RSTP protocol’s fast convergence depends on the use of point-to-point links connecting switches. In order to quickly transition a designated port into non-discarding state, the upstream switch needs to make sure that the downstream neighbor agrees with that idea. This constitutes the process known as handshake (or proposal/agreement):
There's a great document explaining the process of the different types of STP: http://blog.ine.com/wp-content/uploads/2010/04/understanding-stp-rstp-convergence.pdf