ZyXEL Communications Zyair B-1000 v.2, User Manual

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ZyAIR Access Point Series User’s Guide
System Screens 5-5
If the Fragmentation Threshold value is smaller than the RTS/CTS value (see previously) you set then the
RTS (Request To Send)/CTS (Clear to Send) handshake will never occur as data frames will be fragmented
before they reach
RTS/CTS size.
5.3 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.
5.3.1 Rapid STP
The ZyAIR 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.
5.3.2 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 next table.
Table 5-1 STP Path Costs
LINK SPEED RECOMMENDED VALUE RECOMMENDED RANGE ALLOWED 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