1. Home
    2. /
  2. Manuals
    3. /
  3. Zyxel
    4. /
  4. P-660HN-F1Z
    5. /
  5. 73
Page 361 / 421 Scroll up to view Page 356 - 360
Appendix D Wireless LANs
P-660HN-FxZ Series User’s Guide
358
Figure 234
Basic Service Set
ESS
An Extended Service Set (ESS) consists of a series of overlapping BSSs, each containing an
access point, with each access point connected together by a wired network. This wired
connection between APs is called a Distribution System (DS).
This type of wireless LAN topology is called an Infrastructure WLAN. The Access Points not
only provide communication with the wired network but also mediate wireless network traffic
in the immediate neighborhood.
An ESSID (ESS IDentification) uniquely identifies each ESS. All access points and their
associated wireless clients within the same ESS must have the same ESSID in order to
communicate.
Page 362 / 421
Appendix D Wireless LANs
P-660HN-FxZ Series User’s Guide
359
Figure 235
Infrastructure WLAN
Channel
A channel is the radio frequency(ies) used by wireless devices to transmit and receive data.
Channels available depend on your geographical area. You may have a choice of channels (for
your region) so you should use a channel different from an adjacent AP (access point) to
reduce interference. Interference occurs when radio signals from different access points
overlap causing interference and degrading performance.
Adjacent channels partially overlap however. To avoid interference due to overlap, your AP
should be on a channel at least five channels away from a channel that an adjacent AP is using.
For example, if your region has 11 channels and an adjacent AP is using channel 1, then you
need to select a channel between 6 or 11.
RTS/CTS
A hidden node occurs when two stations are within range of the same access point, but are not
within range of each other. The following figure illustrates a hidden node. Both stations (STA)
are within range of the access point (AP) or wireless gateway, but out-of-range of each other,
so they cannot "hear" each other, that is they do not know if the channel is currently being
used. Therefore, they are considered hidden from each other.
Page 363 / 421
Appendix D Wireless LANs
P-660HN-FxZ Series User’s Guide
360
Figure 236
RTS/CTS
When station
A
sends data to the AP, it might not know that the station
B
is already using the
channel. If these two stations send data at the same time, collisions may occur when both sets
of data arrive at the AP at the same time, resulting in a loss of messages for both stations.
RTS/CTS
is designed to prevent collisions due to hidden nodes. An
RTS/CTS
defines the
biggest size data frame you can send before an RTS (Request To Send)/CTS (Clear to Send)
handshake is invoked.
When a data frame exceeds the
RTS/CTS
value you set (between 0 to 2432 bytes), the station
that wants to transmit this frame must first send an RTS (Request To Send) message to the AP
for permission to send it. The AP then responds with a CTS (Clear to Send) message to all
other stations within its range to notify them to defer their transmission. It also reserves and
confirms with the requesting station the time frame for the requested transmission.
Stations can send frames smaller than the specified
RTS/CTS
directly to the AP without the
RTS (Request To Send)/CTS (Clear to Send) handshake.
You should only configure
RTS/CTS
if the possibility of hidden nodes exists on your network
and the "cost" of resending large frames is more than the extra network overhead involved in
the RTS (Request To Send)/CTS (Clear to Send) handshake.
If the
RTS/CTS
value is greater than the
Fragmentation Threshold
value (see next), 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.
"
Enabling the RTS Threshold causes redundant network overhead that could
negatively affect the throughput performance instead of providing a remedy.
Fragmentation Threshold
A
Fragmentation Threshold
is the maximum data fragment size (between 256 and 2432
bytes) that can be sent in the wireless network before the AP will fragment the packet into
smaller data frames.
A large
Fragmentation Threshold
is recommended for networks not prone to interference
while you should set a smaller threshold for busy networks or networks that are prone to
interference.
Page 364 / 421
Appendix D Wireless LANs
P-660HN-FxZ Series User’s Guide
361
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.
Preamble Type
Preamble is used to signal that data is coming to the receiver. Short and long refer to the length
of the synchronization field in a packet.
Short preamble increases performance as less time sending preamble means more time for
sending data. All IEEE 802.11 compliant wireless adapters support long preamble, but not all
support short preamble.
Use long preamble if you are unsure what preamble mode other wireless devices on the
network support, and to provide more reliable communications in busy wireless networks.
Use short preamble if you are sure all wireless devices on the network support it, and to
provide more efficient communications.
Use the dynamic setting to automatically use short preamble when all wireless devices on the
network support it, otherwise the ZyXEL Device uses long preamble.
"
The wireless devices MUST
use the same preamble mode in order to
communicate.
IEEE 802.11g Wireless LAN
IEEE 802.11g is fully compatible with the IEEE 802.11b standard. This means an IEEE
802.11b adapter can interface directly with an IEEE 802.11g access point (and vice versa) at
11 Mbps or lower depending on range. IEEE 802.11g has several intermediate rate steps
between the maximum and minimum data rates. The IEEE 802.11g data rate and modulation
are as follows:
Wireless Security Overview
Wireless security is vital to your network to protect wireless communication between wireless
clients, access points and the wired network.
Table 142
IEEE 802.11g
DATA RATE (MBPS)
MODULATION
1
DBPSK (Differential Binary Phase Shift Keyed)
2
DQPSK (Differential Quadrature Phase Shift Keying)
5.5 / 11
CCK (Complementary Code Keying)
6/9/12/18/24/36/48/54
OFDM (Orthogonal Frequency Division Multiplexing)
Page 365 / 421
Appendix D Wireless LANs
P-660HN-FxZ Series User’s Guide
362
Wireless security methods available on the ZyXEL Device are data encryption, wireless client
authentication, restricting access by device MAC address and hiding the ZyXEL Device
identity.
The following figure shows the relative effectiveness of these wireless security methods
available on your ZyXEL Device.
"
You must enable the same wireless security settings on the ZyXEL Device and
on all wireless clients that you want to associate with it.
IEEE 802.1x
In June 2001, the IEEE 802.1x standard was designed to extend the features of IEEE 802.11 to
support extended authentication as well as providing additional accounting and control
features. It is supported by Windows XP and a number of network devices. Some advantages
of IEEE 802.1x are:
•
User based identification that allows for roaming.
•
Support for RADIUS (Remote Authentication Dial In User Service, RFC 2138, 2139) for
centralized user profile and accounting management on a network RADIUS server.
•
Support for EAP (Extensible Authentication Protocol, RFC 2486) that allows additional
authentication methods to be deployed with no changes to the access point or the wireless
clients.
RADIUS
RADIUS is based on a client-server model that supports authentication, authorization and
accounting. The access point is the client and the server is the RADIUS server. The RADIUS
server handles the following tasks:
• Authentication
Determines the identity of the users.
• Authorization
Table 143
Wireless Security Levels
SECURITY
LEVEL
SECURITY TYPE
Least
Secure
Most Secure
Unique SSID (Default)
Unique SSID with Hide SSID Enabled
MAC Address Filtering
WEP Encryption
IEEE802.1x EAP with RADIUS Server Authentication
Wi-Fi Protected Access (WPA)
WPA2

Rate

4 / 5 based on 1 vote.

Popular Zyxel Models

Famous Router IPs
Famous Router Companies
Bookmark Our Site

Press Ctrl + D to add this site to your favorites!

Share
Top