Spanning Tree Protocol (Stp); Rapid Stp; Stp Terminology - ZyXEL Communications NWA-1100 Manual

Chapter 6 Wireless Settings Screen
On APs without WMM QoS, all traffic streams are given the same access priority to the wireless
network. If the introduction of another traffic stream creates a data transmission demand that
exceeds the current network capacity, then the new traffic stream reduces the throughput of the
other traffic streams.
The NWA uses WMM QoS to prioritize traffic streams according to the IEEE 802.1q or DSCP
information in each packet's header. The NWA automatically determines the priority to use for an
individual traffic stream. This prevents reductions in data transmission for applications that are
sensitive to latency and jitter (variations in delay).

6.5.2 Spanning Tree Protocol (STP)

STP detects and breaks network loops and provides backup links between switches, bridges or
routers. It allows a bridge to interact with other STP-compliant bridges in your network to ensure
that only one route exists between any two stations on the network.

6.5.2.1 Rapid STP

The NWA uses IEEE 802.1w RSTP (Rapid Spanning Tree Protocol) that allow faster convergence of
the spanning tree (while also being backwards compatible with STP-only aware bridges). Using
RSTP topology change information does not have to propagate to the root bridge and unwanted
learned addresses are flushed from the filtering database. In RSTP, the port states are Discarding,
Learning, and Forwarding.

6.5.2.2 STP Terminology

The root bridge is the base of the spanning tree; it is the bridge with the lowest identifier value
(MAC address).
Path cost is the cost of transmitting a frame onto a LAN through that port. It is assigned according
to the speed of the link to which a port is attached. The slower the media, the higher the cost - see
the following table.
Table 15 STP Path Costs
Path Cost
Path Cost
Path Cost
Path Cost
Path Cost
Path Cost
On each bridge, the root port is the port through which this bridge communicates with the root. It is
the port on this switch with the lowest path cost to the root (the root path cost). If there is no root
port, then this bridge has been accepted as the root bridge of the spanning tree network.
For each LAN segment, a designated bridge is selected. This bridge has the lowest cost to the root
among the bridges connected to the LAN.
76
RECOMMENDED
LINK SPEED
VALUE
4Mbps 250
10Mbps 100
16Mbps 62
100Mbps 19
1Gbps 4
10Gbps 2
RECOMMENDED ALLOWED
RANGE RANGE
100 to 1000 1 to 65535
50 to 600 1 to 65535
40 to 400 1 to 65535
10 to 60 1 to 65535
3 to 10 1 to 65535
1 to 5 1 to 65535
NWA1100-N User's Guide