RSTP (Rapid Spanning Tree Protocol) is the evolution of STP. It was the originally introduced as IEEE 802.1w standard. In 2004 IEEE decided to the replace STP with the RSTP in 802.1D standard. Finally, in 2011, The IEEE decided to the move all RSTP details into the 802.1Q standard.
RSTP is
backwards-compatible with the STP and there are many similarities between two
protocols are, such as:
·
The root switch is selected using same set of the rules in the both
protocols
·
Root ports are selected with same rules, as well as designated port
on the LAN segments
·
The both STP & RSTP place each port in the either forwarding or the blocking
state. blocking state in the RSTP is called discarding state.
there are differences
between STP & RSTP:
·
RSTP enable faster convergence times the STP (usually within just the couple
of seconds)
·
STP ports states listening, blocking, & disabled are merged into the
single state in the RSTP – the discarding states
·
STP features are two port types – root and designated ports. RSTP adds
two additional port types are – alternate & backup ports.
·
With the STP, root switch generates and sends Hellos to the all other
switches which are then relayed by non-root switches. With the RSTP, each
switch can generate its they own Hellos.
Consider, following
network topology with the RSTP turned on:
In order to the avoid
loops, RSTP has placed one port on the SW3 in alternate states. This port will
be not process or forward any the frames except RSTP messages. However, if root
port on SW3 fails, the alternate port will be rapidly become root port &
start forwarding frames.
0 Comments