[Bridge] Time of topology change in root bridge

[Butorina Lilya <lilybox@yandex.ru>]

Hi.

I have two bridges with RSTP:

     hdlc0------hdlc0
br0 |                | br1
     hdlc1------hdlc1

br0 is root bridge.

And my initial tree topology:
#rstpctl showport br0
*    hdlc0 8001 Fwd  8000-00ee10022202 8000-00ee10022202 8001 D
*    hdlc1 8002 Fwd  8000-00ee10022202 8000-00ee10022202 8002 D

#rstpctl showport br1
*    hdlc0 8001 Blk  8000-00ee10022202 8000-00ee10022202 8002 R
*    hdlc1 8002 Fwd  8000-00ee10022202 8000-00ee10022202 8001 A


Next I break link on br1 on root port hdlc0 and get new three topology immedatly:
#rstpctl showport br0
*    hdlc0 8001 Dis  8000-00ee10022202 8000-00ee10022202 8001
*    hdlc1 8002 Fwd  8000-00ee10022202 8000-00ee10022202 8002 D

#rstpctl showport br1
*    hdlc0 8001 Dis  8000-00ee10022202 8000-00ee10022202 8002 
*    hdlc1 8002 Fwd  8000-00ee10022202 8000-00ee10022202 8001 R


Next I restore link. 
Here I expect that bouth bridges calculate new (initial) tree topology in 4sec.

I see expected on br1:
*    hdlc0 8001 Blk  8000-00ee10022202 8000-00ee10022202 8002 R
*    hdlc1 8002 Fwd  8000-00ee10022202 8000-00ee10022202 8001 A

But on root bridge br0 I see new tree topology in 30sec.
This time interval looks like STP value.

Is this correct behavior of RSTP or bug?


Thanks. 
Lilya.