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Wireless Network Access Point
47
Troubleshooting
This chapter provides solutions to problems usually encountered during the
installation and operation of the Wireless Network Access Point. Read the
description below to solve your problems. If you can’t find an answer here,
check the Linksys website at www.linksys.com.
What is the purpose of antenna diversity and when should it be used?
When used, how should it be set-up?
The dual antennae on the Access Point are probably best explained using this
example. Take television, if you have ever had the old “rabbit ear type of
antenna” and saw reflections on TV (called “ghosts”), then you moved the
antenna and the reflections “went away.” (Using two antennae allows us to
“MOVE AWAY” from reflections that cause us to lose or have to retransmit
data.) They should be used indoors as outdoor reflections are rare. As long as
both antennae cover roughly the same area, this is fine.
Can the Wireless Network Access Point act as my DHCP Server?
No.
The Access Point is nothing more than a wireless hub, and as such, cannot
be configured to handle DHCP capabilities.
Can I run an application from a remote computer over the wireless net-
work?
This will depend on whether or not the application is designed to be used over
a network. Consult the application’s user guide to determine if it supports oper-
ation over a network.
Can I play multiplayer games with other users of the wireless network?
Yes, as long as the game supports multiple players over a LAN (local area net-
work). Refer to the game’s user guide for more information.
What is the IEEE 802.11b standard?
The IEEE 802.11b Wireless LAN standards subcommittee is formulating a
standard for the industry. The objective is to enable wireless LAN hardware
from different manufacturers to communicate.
Common Problems and Solutions
Frequently Asked Questions
Instant Wireless
TM
Series
THE INFO TAB
The Info tab displays general information about Linksys and the Access Point
SNMP Manager. The SNMP Configuration Utility’s copyright date and version
number are listed as well as the Utility’s firmware version. At the bottom of the
screen, you will find a button that will access Linksys’ web page (once your
Internet connection is properly set up), the email address for technical support,
and the phone number to call for technical support.
Stations
. This shows the MAC addresses of those machines making wireless
connections to the Access Point.
Statistics
. This displays the connection statistics for your wireless and
Ethernet connections.
TrapLog
. This displays the information on any SNMP messages read by
your
Access Point.
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Wireless Network Access Point
As the user moves on, the end node’s RF transmitter regularly checks the sys-
tem to determine whether it is in touch with the original Wireless Network
Access Point or whether it should seek a new one. When a node no longer
receives acknowledgment from its original Wireless Network Access Point, it
undertakes a new search. Upon finding a new Wireless Network Access Point,
it then re-registers, and the communication process continues.
What is BSS ID?
A specific Ad-hoc LAN is called a Basic Service Set (BSS). Computers in a
BSS must be configured with the same BSS ID.
What is ESSID?
An Infrastructure configuration could also support roaming capability for
mobile workers. More than one BSS can be configured as an Extended Service
Set (ESS). Users within an ESS could roam freely between BSSs while main-
taining a continuous connection to the wireless network stations and Wireless
Network Access Points.
What is ISM band?
The FCC and their counterparts outside of the U.S. have set aside bandwidth
for unlicensed use in the ISM (Industrial, Scientific and Medical) band.
Spectrum in the vicinity of 2.4 GHz, in particular, is being made available
worldwide. This presents a truly revolutionary opportunity to place convenient
high speed wireless capabilities in the hands of users around the globe.
What is Spread Spectrum?
Spread Spectrum technology is a wideband radio frequency technique devel-
oped by the military for use in reliable, secure, mission-critical communica-
tions systems. It is designed to trade off bandwidth efficiency for reliability,
integrity, and security. In other words, more bandwidth is consumed than in the
case of narrowband transmission, but the trade-off produces a signal that is, in
effect, louder and thus easier to detect, provided that the receiver knows the
parameters of the spread-spectrum signal being broadcast. If a receiver is not
tuned to the right frequency, a spread-spectrum signal looks like background
noise. There are two main alternatives, Direct Sequence Spread Spectrum
(DSSS) and Frequency Hopping Spread Spectrum (FHSS).
49
Instant Wireless™ Series
What IEEE 802.11 features are supported?
The product supports the following IEEE 802.11 functions:
CSMA/CA plus Acknowledge protocol
Multi-Channel Roaming
Automatic Rate Selection
RTS/CTS feature
Fragmentation
Power Management
What is Ad-hoc?
An Ad-hoc wireless LAN is a group of computers, each with a WLAN adapter,
connected as an independent wireless LAN. An Ad-hoc wireless LAN is appli-
cable at a departmental scale for a branch or SOHO operation.
What is Infrastructure?
An integrated wireless and wired LAN is called an Infrastructure configura-
tion. Infrastructure is applicable to enterprise scale for wireless access to a cen-
tral database, or wireless application for mobile workers.
What is Roaming?
Roaming is the ability of a portable computer user to communicate continu-
ously while moving freely throughout an area greater than that covered by a
single Wireless Network Access Point. Before using the roaming function, the
workstation must make sure that it is the same channel number as the Wireless
Network Access Point of the dedicated coverage area.
To achieve true seamless connectivity, the wireless LAN must incorporate a
number of different functions. Each node and Wireless Network Access Point,
for example, must always acknowledge receipt of each message. Each node
must maintain contact with the wireless network even when not actually trans-
mitting data. Achieving these functions simultaneously requires a dynamic RF
networking technology that links Wireless Network Access Points and nodes.
In such a system, the user’s end node undertakes a search for the best possible
access to the system. First, it evaluates such factors as signal strength and qual-
ity, as well as the message load currently being carried by each Wireless
Network Access Point and the distance of each Wireless Network Access Point
to the wired backbone. Based on that information, the node next selects the
right Wireless Network Access Point and registers its address. Communications
between end node and host computer can then be transmitted up and down the
backbone.
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Instant Wireless™ Series
What is DSSS? What is FHSS? And what are their differences?
Frequency Hopping Spread Spectrum (FHSS) uses a narrowband carrier that
changes frequency in a pattern that is known to both transmitter and receiver.
Properly synchronized, the net effect is to maintain a single logical channel. To
an unintended receiver, FHSS appears to be short-duration impulse noise.
Direct Sequence Spread Spectrum (DSSS) generates a redundant bit pattern for
each bit to be transmitted. This bit pattern is called a chip (or chipping code).
The longer the chip, the greater the probability that the original data can be
recovered. Even if one or more bits in the chip are damaged during transmis-
sion, statistical techniques embedded in the radio can recover the original data
without the need for retransmission. To an unintended receiver, DSSS appears
as low power wideband noise and is rejected (ignored) by most narrowband
receivers.
Would the information be intercepted while transmitting on air?
WLAN features two-fold protection in security. On the hardware side, as with
Direct Sequence Spread Spectrum technology, it has the inherent security fea-
ture of scrambling. On the software side, the WLAN series offers the encryp-
tion function (WEP) to enhance security and access control. Users can set it up
depending upon their needs.
Can Instant Wireless
TM
products support file and printer sharing?
Instant Wireless
TM
products perform the same function as LAN products.
Therefore, Instant Wireless
TM
products can work with Netware, Windows
NT/2000, or other LAN operating systems to support printer or file sharing.
What is WEP?
WEP is Wired Equivalent Privacy, a data privacy mechanism based on a 40 bit
shared key algorithm, as described in the IEEE 802.11 standard.
What is a MAC Address?
The Media Access Control (MAC) address is a unique number assigned by the
manufacturer to any Ethernet networking device, such as a network adapter,
that allows the network to identify it at the hardware level.
For all practical pur-
poses, this number is usually permanent.
Unlike IP addresses, which can
change every time a computer logs on to the network, the MAC address of a
device stays the same, making it a valuable identifier for the network.
50
Glossary
Ad-hoc Network
- An ad-hoc network is a wireless network or other small net-
work in which some of the network devices are part of the network only for the
duration of a communications session, while others stay in close proximity to
the rest of the network.
Default Gateway
- The router used to forward all traffic that is not addressed
to a station within the local subnet.
DHCP
(Dynamic Host Configuration Protocol) - A protocol that lets network
administrators centrally manage and automate the assignment of Internet
Protocol (IP) addresses in an organization's network. Using the Internet's set of
protocol (TCP/IP), each machine that can connect to the Internet needs a
unique IP address. When an organization sets up its computer users with a con-
nection to the Internet, an IP address must be assigned to each machine.
Without DHCP, the IP address must be entered manually at each computer and,
if computers move to another location in another part of the network, a new IP
address must be entered. DHCP lets a network administrator supervise and dis-
tribute IP addresses from a central point and automatically sends a new IP
address when a computer is plugged into a different place in the network.
DHCP uses the concept of a “lease” or amount of time that a given IP address
will be valid for a computer. The lease time can vary depending on how long a
user is likely to require the Internet connection at a particular location. It’s espe-
cially useful in education and other environments where users change fre-
quently. Using very short leases, DHCP can dynamically reconfigure networks
in which there are more computers than there are available IP addresses.
DHCP supports static addresses for computers containing Web servers that
need a permanent IP address.
DNS
- The Domain Name System (DNS) is the way that Internet domain
names are located and translated into Internet Protocol (IP) addresses. A
domain name is a meaningful and easy-to-remember “handle” for an Internet
address.
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52
IP Address
- In the most widely installed level of the Internet Protocol
(Internet Protocol) today, an IP address is a 32-binary digit number that identi-
fies each sender or receiver of information that is sent in packets across the
Internet. When you request an HTML page or send e-mail, the Internet
Protocol part of TCP/IP includes your IP address in the message (actually, in
each of the packets if more than one is required) and sends it to the IP address
that is obtained by looking up the domain name in the Uniform Resource
Locator you requested or in the e-mail address you're sending a note to. At the
other end, the recipient can see the IP address of the Web page requester or the
e-mail sender and can respond by sending another message using the IP address
it received.
IPCONFIG
- A utility that provides for querying, defining and managing IP
addresses within a network.
A commonly used utility, under Windows NT and
2000, for configuring networks with static IP addresses.
ISP
- An ISP (Internet service provider) is a company that provides individuals
and companies access to the Internet and other related services such as website
building and virtual hosting.
LAN
- A local area network (LAN) is a group of computers and associated
devices that share a common communications line and typically share the
resources of a single processor or server within a small geographic area (for
example, within an office building).
MAC Address
- The MAC (Media Access Control) address is a unique num-
ber assigned by the manufacturer to any Ethernet networking device, such as a
network adapter, that allows the network to identify it at the hardware level.
mIRC
- mIRC runs under Windows and provides a graphical interface for log-
ging onto IRC servers and listing, joining, and leaving channels.
Network Mask
- also known as the “Subnet Mask.”
PCMCIA
- The PCMCIA (Personal Computer Memory Card International
Association) is an industry group organized in 1989 to promote standards for a
credit card-size memory or I/O device that would fit into a personal computer,
usually a notebook or laptop computer.
Ping
(Packet INternet Groper) - An Internet utility used to determine whether
a particular IP address is online. It is used to test and debug a network by send-
ing out a packet and waiting for a response.
Instant Wireless
TM
Series
DSSS
- Also known as “Direct Sequence Spread Spectrum,” this is a variety of
radio transmission methods that continuously change frequencies or signal pat-
terns. Direct Sequence Spread Spectrum (DSSS), which is used in CDMA,
multiplies the data bits by a very fast, pseudo-random bit pattern (PN sequence)
that “spreads” the data into a large coded stream that takes the full bandwidth
of the channel.
Dynamic IP Address
- An IP address that is automatically assigned to a client
station in a TCP/IP network, typically by a DHCP server. Network devices that
serve multiple users, such as servers and printers, are usually assigned static IP
addresses.
ESS
- More than one BSS in a network.
FHSS
- Also known as “Frequency Hopping Spread Spectrum.” Frequency
Hopping Spread Spectrum (FHSS) continuously changes the center frequency
of a conventional carrier several times per second according to a pseudo-ran-
dom set of channels, while chirp spread spectrum changes the carrier frequen-
cy. Because a fixed frequency is not used, illegal monitoring of spread spec-
trum signals is extremely difficult, if not downright impossible depending on
the particular method.
Firmware
- Programming that is inserted into programmable read-only mem-
ory, thus becoming a permanent part of a computing device.
IEEE
- The Institute of Electrical and Electronics Engineers. The IEEE
describes itself as “the world's largest technical professional society—promot-
ing the development and application of electrotechnology and allied sciences
for the benefit of humanity, the advancement of the profession, and the well-
being of our members.”
The IEEE fosters the development of standards that often become national and
international standards. The organization publishes a number of journals, has
many local chapters, and has several large societies in special areas, such as the
IEEE Computer Society.
Infrastructure
- An infrastructure network is a wireless network or other small
network in which the wireless network devices are made a part of the network
through an Access Point that connects them to the rest of the network.
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Instant Wireless
TM
Series
UTP
- Unshielded twisted pair is the most common kind of copper telephone
wiring. Twisted pair is the ordinary copper wire that connects home and many
business computers to the telephone company. To reduce crosstalk or electro-
magnetic induction between pairs of wires, two insulated copper wires are
twisted around each other. Each signal on twisted pair requires both wires.
Since some telephone sets or desktop locations require multiple connections,
twisted pair is sometimes installed in two or more pairs, all within a single
cable.
WEP
(Wired Equivalent Privacy) - A data privacy mechanism based on a 64-
bit shared key algorithm, as described in the IEEE 802.11 standard.
WINIPCFG
- Configuration utility based on the Win32 API for querying,
defining, and managing IP addresses within a network.
A commonly used util-
ity, under Windows 95, 98, and Millennium, for configuring networks with
static IP addresses.
54
RJ-45
- A connector similar to a telephone connector that holds up to eight
wires, used for connecting Ethernet devices.
Roaming
- The ability to use a wireless device and be able to move from one
access point’s range to another without losing the connection.
Static IP Address
- A permanent IP address that is assigned to a node in a
TCP/IP network.
Subnet Mask
- The method used for splitting IP networks into a series of sub-
groups, or subnets. The mask is a binary pattern that is matched up with the IP
address to turn part of the host ID address field into a field for subnets.
TCP
(Transmission Control Protocol) - A method (protocol) used along with
the Internet Protocol (Internet Protocol) to send data in the form of message
units between computers over the Internet. While IP takes care of handling the
actual delivery of the data, TCP takes care of keeping track of the individual
units of data (called packets) that a message is divided into for efficient rout-
ing through the Internet.
TCP/IP
- Transmission Control Protocol/Internet Protocol (TCP/IP) is the
basic communication language or protocol of the Internet. It can also be used
as a communications protocol in a private network (either an intranet or an
extranet). When you are set up with direct access to the Internet, your comput-
er is provided with a copy of the TCP/IP program just as every other computer
that you may send messages to or get information from also has a copy of
TCP/IP.
UDP
(User Datagram Protocol) - A communications method (protocol) that
offers a limited amount of service when messages are exchanged between com-
puters in a network that uses the Internet Protocol (IP). UDP is an alternative
to the Transmission Control Protocol (TCP) and, together with IP, is sometimes
referred to as UDP/IP. Like the Transmission Control Protocol, UDP uses the
Internet Protocol to actually get a data unit (called a datagram) from one com-
puter to another. Unlike TCP, however, UDP does not provide the service of
dividing a message into packets (datagrams) and reassembling it at the other
end. Specifically, UDP doesn't provide sequencing of the packets that the data
arrives in. This means that the application program that uses UDP must be able
to make sure that the entire message has arrived and is in the right order.
Network applications that want to save processing time because they have very
small data units to exchange (and therefore very little message reassembling to
do) may prefer UDP to TCP.
Wireless Network Access Point
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