D-Link DES-3250TG User Manual page 36

DES-3250TG Layer 2 Fast Ethernet Switch User's Guide
implementing IEEE 802.1d, however the advantages of using
RSTP will be lost.
The IEEE 802.1w Rapid Spanning Tree Protocol (RSTP) evolved
from the 802.1d STP standard. RSTP was developed in order to
overcome some limitations of STP that impede the function of
some recent switching innovations, in particular, certain Layer
3 function that are increasingly handled by Ethernet switches.
The basic function and much of the terminology is the same as
STP. Most of the settings configured for STP are also used for
RSTP. This section introduces some new Spanning Tree
concepts and illustrates the main differences between the two
protocols.
Port Transition States
An essential difference between the two protocols is in the way
ports transition to a forwarding state and the in the way this
transition relates to the role of the port (forwarding or not
forwarding) in the topology. RSTP combines the transition
states disabled, blocking, and listening used in 802.1d and
creates a single state: discarding. In either case, ports do not
forward packets; in the STP port transition states disabled,
blocking, or listening, or in the RSTP port state discarding,
there is no functional difference, the port is not active in the
network topology. Table 5-1 below compares how the two
protocols differ regarding the port state transition.
802.1d STP 802.1w RSTP
Disabled Discarding
Blocking Discarding
Listening Discarding
Learning Learning
Forwarding? Learning?
No
No
No
No
28
No
No
No
Yes