User manual
The first spanning tree protocol was invented in 1985 at the Digital Equipment Corporation
by Radia Perlman. In 1990, the IEEE published the first standard for the protocol as 802.1D,based
on the algorithm designed by Perlman. Subsequent versions were published in 1998 and 2004,
incorporating various extensions.
Although the purpose of a standard is to promote interworking of equipment from different
vendors, different implementations of a standard are not guaranteed to work, due for example to
differences in default timer settings. The IEEE encourages vendors to provide a "Protocol
Implementation Conformance Statement", declaring which capabilities and options have been
implemented,
[8]
to help users determine whether different implementations will interwork correctly.
Also, the original Perlman-inspired Spanning Tree Protocol, called DEC STP, is not a
standard and differs from the IEEE version in message format as well as timer settings. Some
bridges implement both the IEEE and the DEC versions of the Spanning Tree Protocol, but their
interworking can create issues for the network administrator, as illustrated by the problem discussed
in an on-line Cisco document.
[9]
Rapid Spanning Tree Protocol
In 2001, the IEEE introduced Rapid Spanning Tree Protocol (RSTP) as 802.1w. RSTP
provides significantly faster spanning tree convergence after a topology change, introducing new
convergence behaviors and bridge port roles to do this. RSTP was designed to be backwards-
compatible with standard STP.While STP can take 30 to 50 seconds to respond to a topology
change, RSTP is typically able to respond to changes within 3 × Hello times (default: 3 times 2
seconds) or within a few milliseconds of a physical link failure. The so-called Hello time is an
important and configurable time interval that is used by RSTP for several purposes; its default value
is 2 seconds. Standard IEEE 802.1D-2004 incorporates RSTP and obsoletes the original STP
standard
Select RSTP function in rapid ring network interface as