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

 

 

 

 

 

LINK SPEED

RECOMMENDED

RECOMMENDED

ALLOWED

 

 

VALUE

RANGE

RANGE

 

 

 

Path Cost

 

4Mbps

250

100 to 1000

1 to 65535

 

 

 

 

 

 

Path Cost

 

10Mbps

100

50 to 600

1 to 65535

 

 

 

 

 

 

Path Cost

 

16Mbps

62

40 to 400

1 to 65535

 

 

 

 

 

 

Path Cost

 

100Mbps

19

10 to 60

1 to 65535

 

 

 

 

 

 

Path Cost

 

1Gbps

4

3 to 10

1 to 65535

 

 

 

 

 

 

Path Cost

 

10Gbps

2

1 to 5

1 to 65535

 

 

 

 

 

 

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.

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NWA1100-N User’s Guide