[c-nsp] RSTP convergence time

[Ambedkar]

Hi,
I am using RSTP with hello time=1sec  with snooping diabled. There are
three scenarios i have tested, in which convergence time is varying.

The following diagram shows the test setup:

                 +------+
                  |   A   |
                 +------+
                 /        \
                /          \
               /            \
           +------+     +------+
           |   B    | ----|    C   |
           +------+     +------+
1. A - Root Bridge
2. B-C & C-A Root port
3. C-B is Alternate port

Case-1
1. A, B and C are Cisco 2960 switches  model WS-C2960-24TC-L with IOS Ver
12.2(44)SE6.
2. When link breaks from B-A or C-A , the delay between convergence is
coming around 200ms and when link comes back it is 300ms

Case-2
1. A is Cisco 6509 sup2  model WS-X6K-S2U-MSFC2 with Software ver 8.3(2)
2. B and C are 2960 switches model WS-C2960-24TC-L with IOS Ver 12.2(44)SE6.
3. When link breaks from B-A or C-A , the delay between convergence is
coming around 300ms and when link comes back it is 1.1 sec

Case-3
1. A is Cisco 6509 sup720 with IOS ver 12.2(17r)SX5
2. B and C are 2960 switches model WS-C2960-24TC-L with IOS Ver 12.2(44)SE6.
3. When link breaks from B-A or C-A , the delay between convergence is
coming around 1sec and when link comes back it is 300ms.

In case-2 and case-3, why the convergence time is high compare to case-1,
in which Cisco 6509 is advanced layer-3 switch compared to cisco 2960

Can anybody please help to get minimum convergence time for case-2 and
case-3.

Thanks,
Ambi