一道RSTP协议，极难懂，求解析？

flysnowsuda

QUESTION 352
Which three statements about RSTP are true?(choose three)
A. RSTP significantly reduces topology reconverging time after a link failure.
B. RSTP expends the STP port roles by adding the alternate and backup roles.
C. RSTP port atates are blocking,discarding,learing,or forwarding.
D. RSTP also uses the STP proprsal-agreement sequence.
E. RSTP use the same timer-baseed process as STP on point-to-point links.
F. RSTP provides a faster transition to the forwarding state on point-to-point links than STP does.
Answer: ABF
Section: New
Explanation/Reference:
A能够减少汇聚时间
B比STP增加了端口角色alternat和backup
F在点到点链路提供比STP更快的传输和转发


主要是D E 选项，根本看不懂意思，求解析？

0700380227

D选项：RSTP和STP一样使用P、A位，  STP不适用PA位。D错
E选项：RSTP在点到点链路上使用PA协商快速收敛，不像STP经过2倍的转发延时计时器。E错

璃箜-博

E说RSTP使用与STP在点到点link用一样的间隔时间，那肯定是错的，RSTP收敛时间比STP快多咯....你看AF的选项就知道了....