User's Manual

AirWorks AWK-3121 User’s Manual References
5-4
STP and RSTP
The STP/RSTP Concept
Spanning Tree Protocol (STP) was designed to help reduce link failures in a network, and provide
protection from loops. Networks that have a complicated architecture are prone to broadcast
storms caused by unintended loops in the network. The STP protocol is part of the IEEE802.1D
standard, 1998 Edition bridge specification. The explanation given below uses bridge instead of
switch.
Rapid Spanning Tree Protocol (RSTP) implements the Spanning Tree Algorithm and Protocol
defined by IEEE802.1w-2001 standard. RSTP provides the following benefits:
y The topology of a bridged network will be determined much more quickly compared to STP.
y RSTP is backward compatible with STP, making it relatively easy to deploy. For example:
 Defaults to sending 802.1D-style BPDUs if packets with this format are received.
 STP (802.1D) and RSTP (802.1w) can operate on the LAN ports and WLAN ports (AP
and WDS1-WDS8) of the same AWK-3121.
This feature is particularly helpful when the AWK-3121 connects to older equipment, such as
legacy switches.
Differences between RSTP and STP
RSTP is similar to STP, but includes additional information in the BPDUs that allow each bridge
to confirm that it has taken action to prevent loops from forming when it decides to enable a link
to a neighboring bridge. Adjacent bridges connected via point-to-point links will be able to enable
a link without waiting to ensure that all other bridges in the network have had time to react to the
change. The main benefit of RSTP is that the configuration decision is made locally rather than
network-wide, allowing RSTP to carry out automatic configuration and restore a link faster than
STP.