ZyXEL Communications 802.11a/g Wireless CardBus Card ZyXEL AG-120, Руководство пользователя

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Chapter 8 Wireless Configuration
NWA-3500/NWA-3550 User’s Guide
133
8.5.1.4 STP Port States
STP assigns five port states (see next table) to eliminate packet looping. A bridge
port is not allowed to go directly from blocking state to forwarding state so as to
eliminate transient loops.
8.5.2 DFS
When you choose 802.11a in Access Point mode, the NWA uses DFS (Dynamic
Frequency Selection) to give you a wider choice of wireless channels.
DFS allows you to use channels in the frequency range normally reserved for radar
systems. Radar uses radio signals to detect the location of objects for military,
meteorological or air traffic control purposes. As long as your NWA detects no
radar activity on the channel you select, you can use the channel to communicate.
However, a wireless LAN operating on the same frequency as an active radar
system could disrupt the radar system. Therefore, if the NWA detects radar
activity on the channel you select, it automatically instructs the wireless clients to
move to another channel, then resumes communications on the new channel.
8.5.3 Roaming
A wireless station is a device with an IEEE 802.11a/b/g compliant wireless
interface. An access point (AP) acts as a bridge between the wireless and wired
networks. An AP creates its own wireless coverage area. A wireless station can
associate with a particular access point only if it is within the access point’s
coverage area.
In a network environment with multiple access points, wireless stations are able to
switch from one access point to another as they move between the coverage
areas. This is known as roaming. As the wireless station moves from place to
place, it is responsible for choosing the most appropriate access point depending
on the signal strength, network utilization or other factors.
Table 31 STP Port States
PORT
STATES
DESCRIPTIONS
Disabled STP is disabled (default).
Blocking Only configuration and management BPDUs are received and processed.
Listening All BPDUs are received and processed.
Learning All BPDUs are received and processed. Information frames are
submitted to the learning process but not forwarded.
Forwarding All BPDUs are received and processed. All information frames are
received and forwarded.